V. N. Kornienko · I. N. Pronin Diagnostic Neuroradiology
V. N. Kornienko · I. N. Pronin
Diagnostic Neuroradiology Wi...
105 downloads
2050 Views
80MB Size
Report
This content was uploaded by our users and we assume good faith they have the permission to share this book. If you own the copyright to this book and it is wrongfully on our website, we offer a simple DMCA procedure to remove your content from our site. Start by pressing the button below!
Report copyright / DMCA form
V. N. Kornienko · I. N. Pronin Diagnostic Neuroradiology
V. N. Kornienko · I. N. Pronin
Diagnostic Neuroradiology With 1905 Figures and 22 Tables
123
Valery N. Kornienko Igor Nicolaevich Pronin
Burdenko Neurosurgical Institute Dept. of Neuroradiology 4-th Tverskaya-Yamskaya Ulica 16 Moscow, 125047 Russia
ISBN 978-3-540-75652-1
e-ISBN 978-3-540-75653-8
DOI 10.1007/978-3-540-75653-8 Library of Congress Control Number: 2008936632 © 2009 Springer-Verlag Berlin Heidelberg This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Product liability: the publishers cannot guarantee the accuracy of any information about dosage and application contained in this book. In every individual case the user must check such information by consulting the relevant literature. Cover design: Frido Steinen-Broo, eStudio Calamar, Spain Production & Typesetting: le-tex publishing services oHG, Leipzig, Germany Printed on acid-free paper 987654321 Springer.com
V.N. Kornienko, M.D., Ph.D., is the head of the Neuroimaging Department of the Burdenko Neurosurgical Institute Russian Academy of Medical Sciences, a professor, an honour scientist of the Russian Federation, and the author of 12 monographs on neuroradiology and more than 500 scientific publications.
I.N. Pronin, M.D., Ph.D., is a professor in the Neuroimaging Department of Burdenko Neurosurgical Institute Russian Academy of Medical Sciences and the author of 2 monographs on neuroradiology as well as 220 scientific publications.
Preface
In the early twentieth century, fledgling radiological technology became the basis for today’s medical visualisation methods. The first neuroradiologists used X-rays to discern anatomical brain disturbances formerly hidden by the skull. In the 1970s, computerized visualisation technology made revolutionary advances in diagnostics, especially in the field of neuroradiology. Direct digital angiography and computed tomography (CT) made it possible to explore in detail the skull cavity, to estimate normal brain anatomy, and to observe pathology. Magnetic resonance imaging (MRI) opened new doors in terms of differentiating between healthy and pathological tissue. Now in the beginning of the twenty-first century, the quality of MR images of the brain can be compared with that of traditional histological slices. Multispiral CT, high-field MRI, and positron emission tomography (PET) make it possible to visualise physiological and biological processes along with their quantitative estimation, and expand the range of diagnostic possibilities concerning brain and spinal cord disease. Noninvasive and minimally invasive methods of diagnostics and treatment including functional CT and MRI are now incorporated into everyday practice. Among them functional MRI, perfusion CT and MRI, methods of cerebral spinal fluid (CSF) flow measurement, diffusion MRI, tractography, and MR spectroscopy aid in making better prognoses regarding the results of treatment, and monitor therapy in vivo. All these methods make it possible to, e.g. carry out CT and MRI navigation during brain surgery, to plan radiotherapy, and to monitor the efficacy of treatment. With such a variety of modern visualisation methods covered in this book, we place emphasis on the physician choosing the method (or sometimes complex of methods) best suited to obtain optimal results. Radiology is the cornerstone of medical diagnostics, and a neuroradiologist may be the first physician to meet the patient in a clinical setting. There are many examples presented in this book of one being the first physician on a case. Even without the history of disease, the neuroradiologist should be able to make the correct diagnosis, guided only by personal clinical experience and the results of neurovisualisation, as proven by the case examples given in the following chapters.
Longstanding experience of neuroradiological investigations and material gained because of the combined work of clinicians, neuroradiologists, MR engineers, and physicists of the Burdenko Neurosurgical Institute of the Russian Academy of Medical Sciences are the basis of this book. The book contains 15 chapters. The first chapter outlines the stages of formation and development of neurovisualisation technology, with a historical background, and gives information necessary for understanding the novel diagnostic methods that help to visualise pathology in the context of anatomical and pathophysiological changes, even on the molecular level. New diagnostic technology makes it possible to obtain quantitative estimation of changes in disease progression, and it plays an important role in making early diagnoses within routine protocols of investigations. The chapter is aimed at readers who are familiar with the basic principles of CT and MR imaging, which is why in it we consider only the main principles and practical aspects of the newest quantitative CT and MRI diagnostic technologies, including diffusion MRI and diffusion tensor imaging, CT perfusion and MR perfusion, functional MRI, proton spectroscopy, and CT angiography and MR angiography. In other chapters, we discuss the diagnostic principles of the main categories of diseases of, and damages to, the CNS. Most of this volume is devoted to the diagnoses of cerebrovascular disease, intracerebral and extracranial tumours and tumour-like processes, inflammatory, demyelinative, and neurodegenerative disease, and traumatic brain and spinal damage. Chapters dedicated to the diagnoses of brain tumours are based on verified clinical cases (more than 30,000) using the complex approach including MRI, MRS, CT and MR perfusions, and diffusion-weighted imaging. Proton MR spectroscopy information is given in single- and multivoxel-regime formats. Each clinical chapter contains the most important information on CNS pathological changes, basic markers for specific diagnose of the diseases, and unique images of rare pathologies. We hope this book will be the source of neuroradiological knowledge for neurosurgeons, neurologists, neuroendocrinologists, neurotraumatologists, and paediatricians with
VIII
clinical experience, as well as for interns, postgraduate students, students, and physicians, who can use it for expanding their neuroradiological skills. We believe that specialists in fields adjacent to neuroradiology, for example, biophysics and medical physics, will be interested in this book as well. Many illustrations are the “visual text” of this helpful reference book and atlas for everyday, practical work. In conclusion, the authors express sincere gratitude for all the officials of our Department of Neuroradiology and our
Preface
Institute, who contributed to the publishing of this book. Our special thanks go to our colleagues Dr. Fadeeva (Chap. 1), Dr. Takush (Chap. 1), Dr. Rodionov (Chap. 1), Dr. Ozerova (Chaps. 2 and 10), Prof. Potapov (Chap. 9), Prof. Kravchuk (Chap. 9), Dr. Zaharova (Chap. 9), Dr. Aroutiunov (Chap. 10), and Dr. Serkov (Chaps. 12, 13, and 14). Moscow, Russia April 2008
V. Kornienko, I. Pronin, and E. Cabanis
Contents
1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2
Neuroradiology: History and New Research Technologies .. . . . . . . . . . . . . . . ... in collaboration with L. Fadeeva, S. Takush, and P. Rodionov Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... History of Russian Neuroradiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... New Functional Methods in Neuroradiology .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Perfusion-Weighted Imaging .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Functional MRI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Proton MR Spectroscopy .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Phosphorus MR Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Neuroradiology and Information Technologies .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Navigation in Neurosurgery .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....
2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9
Congenital Malformations of the Brain and Skull . . . . . . . . . . . . . . . . . . . . . . . . .... in collaboration with V. Ozerova Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Organogenesis Impairment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Impairment of Brain Diverticulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Impairment of Gyri and Sulci Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Changes in Brain Size .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Destructive Brain Lesions .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Histogenesis Impairment .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Arachnoid Cysts .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Congenital Anterior Cranial Malformations .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....
3 3.1 3.2 3.3
Cerebrovascular Diseases and Malformations of the Brain .. . . . . . . . . . . . . .... Stenosis and Thrombosis of the Cerebral Vessels .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Cerebral Ischaemia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Lacunar Infarction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
1 1 2 3
11 15 17 22 23 25
29
29 29 41 46 53 53 60 69 80
87 87 101 139
X
Contents
3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20
Chronic Ischaemic Brain Disease . .............. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stroke in Children ................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Non-Atherosclerotic Stenosis and Occlusion of Cerebral Arteries .. . . . . . . . . . . . . . . . . . Thrombosis of the Venous Sinuses .............. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Haemorrhagic Infarction ........................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Intracerebral Haemorrhages ................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Extracerebral Non-traumatic Haemorrhages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Intratumoral Haemorrhages ..................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hypertense Haemorrhages ...................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hypertense Encephalopathy .................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rare Causes of Intracerebral Haemorrhage .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Intracranial Arterial Aneurysms ................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Intracranial Vascular Malformations . .......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carotid–Cavernous Fistulas . .................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cavernous Angioma . ............................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Capillary Telangiectasias . ...................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Venous Malformations . ........................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
154
4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10
Supratentorial Tumours ...................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction .................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Supratentorial Tumours . ....................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Neuroepithelial Tumours . ....................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Neuronal and Mixed Neuronal–Glial Tumours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Embryonic Neuroepithelial Tumours . .......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Primary Lymphoma of the CNS .................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Metastatic Tumours .............................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Supratentorial Cysts ............................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eosinophilic Granuloma . ....................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Myeloma (Kahler’s Disease, Plasmacytoma) . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
333
5 5.1 5.2 5.3 5.4 5.5
Pineal Region Tumours ...................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction .................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Germ Cell Tumours .............................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pineal Parenchymal Tumours .................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Glial Tumours ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Other Histological Types of Tumours . .......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
489
6 6.1 6.2
Sellar and Parasellar Tumours .............. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 Introduction .................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 Anatomy .. . . . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529
158 160 172 175 176 188 193 196 197 197 199 247 302 309 316 320
333 333 335 418 425 432 440 464 476 481
489 490 503 510 510
Contents
XI
6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11 6.12 6.13 6.14 6.15 6.16 6.17 6.18 6.19 6.20
Pituitary Anomalies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... “Empty” Sella Turcica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Pituitary Adenomas .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Craniopharyngioma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Gliomas of the Optic Nerves, Chiasm, and Hypothalamus .. . . . . . . . . . . . . . . . . . . . . . ... Germinomas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Teratoma, Epidermoid Tumours, and Dermoid Tumours .. . . . . . . . . . . . . . . . . . . . . . . . .... Chordoma .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Hamartomas of the Tuber Cinereum .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Langerhans Cell Histiocytosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Ratke’s Cleft Cysts .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Meningioma .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Neurinoma of the Fifth Cranial Nerve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Metastases ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Paragangliomas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Arachnoid Cyst .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Vascular Disorders: Aneurysm .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Inflammatory Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
531
7 7.1 7.2 7.3 7.4 7.5
Infratentorial Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Intra-Axial Tumours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Extra-Axial Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Brainstem Lesions .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Меtastases ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
617
8 8.1 8.2
Tumours of the Meninges .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... 719 Meningioma .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... 719 Non-Meningothelial Tumours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 785
9
Head Trauma .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... in collaboration with A. Potapov, A. Kravchuk, and N. Zaharova Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... Primary Brain Injuries .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Secondary Injuries .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....
9.1 9.2 9.3 10
531 535 556 573 579 580 585 585 591 592 594 594 598 598 598 605 605
617 617 651 680 705
807 807 808 869
Hydrocephalus .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... 919 in collaboration with V. Ozerova and N. Aroutiunov 10.1 Physiology of the Cerebrospinal Fluid System .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 919
XII
Contents
10.2 Techniques for Neuroimaging of CSF Spaces and Quantitative Measurement of CSF Circulation ............................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3 Quantitative Techniques for Measurement of CSF Flow Velocity by PC MRI .. . . . . . . 10.4 Clinical Studies . ................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5 Complications . .................................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
921
11 11.1 11.2 11.3 11.4 11.5 11.6
945
Intracranial Infections . ...................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction .................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bacterial Infection .............................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Granulomatous Infections ...................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fungal Infection (Mycosis) of the CNS .......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Viral Infections . ................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parasitogenic Disorders .......................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
921 924 933
945 946 964 969 975 988
12
Toxic and Metabolic Disorders .............. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1003 in collaboration with S. Serkov 12.1 Introduction .................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1003 12.2 Primary Toxic and Metabolic Encephalopathies .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1003 13
Demyelinating Diseases of the Central Nervous System .. . . . . . . . . . . . . . . . . . . in collaboration with S. Serkov 13.1 Introduction .................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2 Primary Demyelinating Diseases ............... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3 Disorders with Secondary Demyelination and/or Destruction of White Matter .. . .
1033
14
1075
14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8
Neurodegenerative Disorders of the Central Nervous System . . . . . . . . . . . . . in collaboration with S. Serkov Introduction .................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synucleinopathies .............................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Taupathies .. . ................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cerebral Amyloidoses ............................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spinocerebellar Degenerations .................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Huntington’s Disease ............................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hereditary Spastic Paraplegias ................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Amyotrophic Lateral Sclerosis . ................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1033 1034 1063
1075 1076 1078 1080 1084 1084 1085 1086
15 Spine and Spinal Cord Disorders ............ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1093 15.1 Imaging Modality and Normal MRI Anatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1093 15.2 Specific Features of the Spine and Spinal Cord in Children .. . . . . . . . . . . . . . . . . . . . . . . . 1096
Contents
XIII
15.3 15.4 15.5 15.6 15.7 15.8 15.9
Congenital Spinal Pathology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Spinal Cord Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Intramedullary Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... Extramedullary–Intradural Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Extradural Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Traumatic Spine and Spinal Cord Injuries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Degenerative Spinal Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
16
Subject Index .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1285
1097 1122 1124 1150 1184 1261 1267
Chapter 1
Neuroradiology: History and New Research Technologies
1
in collaboration with L. Fadeeva, S. Takush, and P. Rodionov
1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9
Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . History of Russian Neuroradiology .. . . . . . . . . . . . . . . . . . . . . . . . . . . New Functional Methods in Neuroradiology .. . . . . . . . . . . . . . . . . Perfusion-Weighted Imaging .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . Functional MRI .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . Proton MR Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . Phosphorus MR Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . Neuroradiology and Information Technologies .. . . . . . . . . . . . . . Navigation in Neurosurgery .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1
Introduction
1 2 3 11 15 17 22 23 25
Neuroradiology is a part of general radiology that is dedicated to the diagnostic examination of the brain and spinal cord. The history of neuroradiology, as a whole, reflects the history of radiology development. The birthday of radiology could be considered as 8 November 1895; it was on this day that W. K. Roentgen was experimenting with a cathode tube and discovered a new type of radiation (emission) with high penetrating capacity. Eventually he named this new type of radiation the “X-ray”. Roentgen made the first X-ray image—a skull—in December 1895. In the beginning of January 1896, after 2 months of painstaking research, he published the article “On a New Kind of Rays”, and on 23 January he made a presentation on his discovery to a session of the Würzburg Physics–Medical Society. He showed images of bony skeleton structures, created by X-rays passed through a human body to the surface of the photographic plate. Roentgen’s discovery gave powerful impetus to research in physics, and the world’s scientific community of physicists, mathematicians, biologists and physicians welcomed this breakthrough. For his discovery of X-rays, he received the first Nobel Prize in physics in 1901. X-rays promptly became the new tool in physics research, and in medicine, they provided many opportunities to visualise the internal structures of the human body. Commonly, X-rays were named “Roentgen rays”, the cathode tubes “Roentgen tubes” and the machines
for obtaining the images of the internal structure “Roentgen machines”. The first diagnostic machine was revealed in Germany on 26 January 1896. It could capture the image of bone structures, formed on the photographic layer of specially prepared plate by passing X-rays through the body. For more than a century, medicine has been able to visualise internal organs and bones via X-rays. This method is known as radiography. The successful application of X-rays for visualisation of highcontrast bone structures facilitated the emergence of the new section of medicine: radiology. In Russia, the first roentgenograms (X-ray films) were obtained in the physics laboratories of St. Petersburg (12–13 January 1896) and Moscow (15–16 January 1896). The first Russian X-ray machine for medical diagnostics was designed by A.S. Popov at the end of February 1896, set up in the Krondshtadt Sea Hospital. At the beginning of the twentieth century, X-ray machines were available in many Russian cities: St. Petersburg (St. Petersburg University, the St. Petersburg Military Medical Academy, and the Clinical Institute of St. Petersburg), Moscow (the Moscow University), Kiev (St. Vladimir’s Imperial University) and Kazan, among others. In 1896, in St. Petersburg’s Military Medical Academy and in the Surgical Clinic of the Kiev University, the first operations were performed in the removal of foreign bodies, detected with the help of radiography. The first issue of the radiological magazine, Herald of Radiology, was produced in July 1907 in Odessa, and the first all-Russian Congress of Radiologists took place in Moscow in December 1916; thus, radiology became an independent speciality in Russia. The State Radiological and Cancer Institute was founded in 1918 in St. Petersburg; its first president was the well-known physicist A.F. Ioffe. After a year, the Physics Department of the Institute became an independent institution, the Institute of Radiology and Roentgenology, and M.I. Nemenov was appointed to the position of its director. In front of the Institute, on 29 January 1920, the first-ever monument dedicated to Roentgen was erected. The first radiological clinic was established in the Institute; later, similar clinics emerged in Paris’s Curie Institute and in the Forsell Institute in Stockholm.
2
Chapter 1
In 1919, the Russian Association of Radiologists and Roentgenologists was founded, and in 1920, the journal Herald of Roentgenology and Radiology was issued, which continues to be published today.
1.2
History of Russian Neuroradiology
The history of Russian neuroradiology began with a perspicacious prediction by V.M. Bekhterev, the outstanding Russian neuropathologist. In his presentation on 15 February 1896 in The Clinic of Central Nervous System Diseases, St. Petersburg Military Medical Academy, he told the audience that many diseases of the nerves are caused by changes in the skull and vertebrae and, possibly, X-rays could help to detect these changes. He foresaw visualisation of the paths of intracranial arteries through the skull, with the help of administration of a special substance that absorbs X-rays. He also envisaged the visualisation of a grey matter with X-rays. His predictions have come to fruition today in widely used neuroradiology methods like angiography and computer tomography (CT). V.M. Bekhterev organised the first Russian neuroradiology department in the St. Petersburg Institute, which now bears his name. Russian neuroradiology passed through the same stages as the world’s neuroradiology. Its development was prompted by the general rise of radiological science and practice, and was further stimulated by the organisation of special neurological, neurosurgical and neuropsychiatric institutions, in which the first specialised neuroradiology departments were formed. Such prominent scientists as N.N. Altgauzen, M.D. Galperin, M.B. Kopylov and F.A. Serbinenko (1974), among others, played leading roles in the formation and prospering of Russian neuroradiology. The 1920s was an epoch of pneumoencephalography development. The 1930s were marked by the emergence of brain vessel angiography. The first angiography in Russia was performed in 1930 in the Narkomzdrav Neurosurgery Clinic in Moscow by B.G. Egorov and M.B. Kopylov. They used 25% iodide sodium solution in the procedure. In 1931, with the help of angiography, a traumatic aneurysm of the carotid artery was diagnosed in the same clinic. (Later, the Clinic was reorganised as the Neurosurgery Scientific-Research Institute, which is now the Burdenko Neurosurgical Institute). It was the first clinical case of vessel lesion diagnosis in Russia. In 1965, A.I. Arutiunov and V.N. Kornienko, for the first time in Russia, started to use total angiography of brain vessels with femoral artery catheterisation (Aroutiunov 1971). In 1971, F.A. Serbinenko pioneered the method of radioendovasal occlusion of brain arteries, with the help of detached balloon. This method was subsequently named after him: the Serbinenko method. The history of neuroradiology is, on the one hand, the history of collaboration of radiologists, neurologists and neurosurgeons in the development of clinical methods of central nervous system (CNS) radiological examination. On the other
hand, it is the history of collaboration of physicists, mathematicians, engineers and radiologists in the design and creation of new devices for brain and diagnostics of spinal cord diseases. The 1930s witnessed the arrival of linear tomography methods (tomos is the Greek word meaning “section”) in radiology. Independently from B. Ziedses des Plantes, the Russian scientist V.I. Feoktistov considered the theoretical opportunity of capture of an object’s internal layer on X-ray film in the course of synchronous moving of a tube and a film relative to the motionless isocenter during the objects exposure to the radiation (Feoktistov 1935). From 1935 to 1946, the phenomenon of a nuclear magnetic resonance was discovered. In 1941, E.K. Zavojsky, in Kazakhstan, obtained one of the first nuclear magnetic resonance spectrum of a substance (Zavojsky 1945). The 1950s and 1960s witnessed a quest for practical solutions of tomography problems in neuroradiology, and the subsequent development of electronics and computer techniques. The 1970s and 1980s for Russian neuroradiology were the time of wide introduction of a CT method in the clinical setting, and the appearance of the first magnetic resonance scanners. In the Soviet Union, the first computed tomograph manufactured by EMI (London) was set up in the Scientific Research Institute of Neurology in which, on 21 June 1977, the first CT brain examination in Russia was performed. The first secondgeneration scanner ND8000 (CGR, La Rochelle, France) was set up in 1978 in the Burdenko Moscow Neurosurgical Institute. In 1985, A.N. Konovalov and V.N. Kornienko published the monograph Computed Tomography in the Neurosurgery Clinic, in which they summarised the experience of CT use at the Institute of Neurosurgery. For the period from 1981 to 1985, more than 12,000 patients were examined in the Institute; in the overwhelming majority of them, the initial diagnosis set with the help of CT was later confirmed during the operations. The first Soviet CT scanners of the second generation were made in Kiev. The first MRI scanner produced by Bruker, with the induction of the magnetic field of 0.22 T, was established in the Institute of Cable Industry, Moscow, in 1983. By the end of twentieth century, magnetic resonance imaging (MRI) had been strongly incorporated into a clinical practice, and in some cases (spinal cord examination) became a method of a choice in comparison with the usual CT. The high tissue resolution and a wide variety of types of contrast for MR images are typical for MRI. Currently, MRI employs several physical factors defining the brightness of tissue on the image such as: proton density; Т1, Т2, and Т2* relaxation time of protons in tissue; the movement of protons in the large vessels with a blood–cerebrospinal fluid (CSF) flow and passage of protons through a capillary net; random thermal water molecule motion; anisotropy of the diffusion proton motion and a magnetic susceptibility of tissues; and chemical shift of proton’s resonance frequency in molecular complexes. More importantly, volumetric CT and super-fast MRI open wide diagnostic opportunities of CNS examination not only
Neuroradiology: History and New Research Technologies
on a level of anatomic structures (simulation and support of surgery, endoscopy), but also on a level of molecular and gene biology. Neuroradiology becomes a quantitative method of brain function examination, the method of monitoring, and prediction of the results of therapeutic treatment and surgical intervention of many diseases. Currently, large, specialised neuroradiology departments exist in clinical research centres in Moscow and St. Petersburg. The general radiologists working in radiological departments of hospitals with neurosurgery and neurological or psychiatric departments deal with problems of CNS disease diagnostics. In Russia, the specialty, unfortunately, bears the name “ray diagnostics”, and it includes all the different disciplines (specialities) dealing with various sorts of radiation (emanation): radiology (including CT and MRI), ultrasound diagnostic and radiotherapy (while there is internationally accepted division into radiology) and nuclear medicine, which more precisely reflects the subject (the essence of the matter). In 1990, a society of ray diagnostics was established in Russia. The specialised training on neuroradiology is currently relatively simple: after graduation, a physician attends the special 6-month course on radiology, listens to lectures, and passes the exam on main radiology topics including neuroradiology. Large neurosurgery centres have a specialised 2-year residence on radiology, in which physicians can combine the practical neuroradiological work (from X-ray images description to work on CT and MRI and conducting such diagnostic examination like direct angiography and myelography) with scientific research. Recently, the educational process (from university to the obtainment of neuroradiology qualification) underwent revision in the light of international experience. Russian still lacks a neuroradiological society. In 2001, the Russia Academy of Medical Sciences established neuroradiology as a separate speciality. The Moscow Institute of Neurosurgery (now The Burdenko Neurosurgical Institute) was founded in 1932, based on the Neurosurgery Clinic of the State X-ray (Roentgen) Institute of Russian Ministry of Health. The academician N.N. Burdenko was the Institute organiser and he became its first director. True to his plan, the Institute was created as a complex establishment in which neurologists, radiologists, morphologists, physiologists, ophthalmologists, otolaryngologists, psychologists, and other physicians worked together with neurosurgeons. The Institute’s departments and laboratories promoted the development of such new scientific disciplines as neuroradiology, oto-ophthalmoneurology and paediatric neurosurgery, and helped to develop not only the practice, but also the theory of neurosurgery. In different years, prominent Russian neurosurgeons B.G. Egorov, A.I. Aroutiunov, A.A. Arendt, L.A. Korejsha, V.M. Ugrjumov, S.S. Brjusova, and neuroradiologists M.B. Kopylov, A.N. Kun, Z.N Poljanker and A.S. Plevako, among other scientists and experts, worked in the Institute. Currently, the Institute is the largest neurosurgery centre in Russia and, in fact, the world. There are three Members and Corresponding Members of the Russian Academy of Medical
3
Sciences, more than 40 professors, and more than 100 Ph.D.’s among the more than 2,000 Institute staff. Since 1975, the Institute has been headed by the Member of Russian Academy of Science and Russian Academy of Medical Science Professor, A.N. Konovalov. The Institute is situated in a newly built, specialised surgical complex. In this 14-story building, there are ten various clinical departments and 300 beds. The surgical unit consists of 16 operating rooms. About 5,000 complex surgeries concerning central and peripheral nervous system disorders/diseases are annually performed in the Institute. The Department of Neuroradiology is equipped by six CT scanners (three of them being spiral scanners) and three MRI scanners (with magnetic field inductions of 1,0 and 1.5 T). The department has two analogue–digital angiography (DSA) devices. Standard X-ray machines use digital carriers to record X-ray images. All diagnostic devices and installations are linked by a special informational neuroradiological network that is connected with the general Institute’s network and the Internet. Further development of neuroradiology is closely linked with the increase of processing speed and improvements in computer technologies, increase of the (MRI) magnetic field induction, the development of “open” magnets for biopsy, the intra-operational control, the examination of critically ill patients and patients with complications after an injury, the children, and so forth.
1.3
New Functional Methods in Neuroradiology
The increase of the processing speed of CT and MRI scanners, the invention of new data-registration technologies and the algorithms of data-processing transfer neuroradiology to entire new level. Neuroradiology development the follows the path “from anatomy to brain functions” (Cha 2006). Anatomic scans of standard CT and MRI demonstrate different types of tissue: blood, fat, white and grey matter, bones, and so forth. Modern CT and MRI methods can estimate speed and orientation of diffusive motion of water molecules and “see” the tissues differ in exchange interaction of protons, transport of ions and molecules (K+, Na+), environmental pH and phagocytosis (Hesseltine et al. 2007; Spilt et al. 2006; Cha 2006). With enriched blood flow, MRI can detect areas of the brain having increased neuronal and metabolic activity, find areas of damage in the brain–blood barrier, make a quantitative assessment of microvascular permeability of brain tissue, evaluate the state of receptors on the cell surface as well as hormonal activity, and reveal the presence of certain antigen and protein structures, among other abilities (Chai et al. 2007; Stadlbauer et al. 2007; Hourani et al. 2006; Holshouser et al. 2006; Cha et al. 2006). Thus, CT and MRI perform diagnostics not only on a cellular, but also on a molecular level. As such, diffusion, perfusion, and functional MRI and MR spectroscopy belong to the so-called methods of molecular visualisation.
4
1.3.1 Methods of Diffusion Motion Visualisation Diffusion is the basic physical process occurring during the cell’s metabolic reactions. Kinetic energy leads to Brownian motion (random walk) of molecules (thermal motion; the speed is about 10–3 mm2/s). As a whole, the molecular motion of protons in physiological systems is divided into three types: (1) movement with moderate speed in macroscopic vessels (about 10–100 mm/s); (2) slow flow in a capillary net, or perfusion (the speed is about 0.1–10 mm/s); and (3) diffusion motion of molecules (the speed is about 10–3 mm2/s). Blood flow in large vessels is measured as a volume-in-time unit, perfusion flow (a local blood flow) is measured as the volume of blood passing in and out of a given tissue weight (volume) per unit of time and the diffusion factor is estimated by the average square of the distance made by molecules for a time unit. Phenomenologically, the diffusion properties in the isotropic environment is characterised with the help of Fick’s law, which connects the vector of particle flux with the gradient of their concentration. The diffusion factor (coefficient), D, is a factor of proportionality. The higher the value of diffusion factor, the more quickly solution mixing occurs. A. Einstein in 1905 applied the probabilistic approach to the description of diffusive motion. According to such approach, the cumulative motion of all particles is characterised by the probability of displacement of separate molecules from one point of space to another, although the exact trajectory (trace) of each particle is unknown. For a one-dimensional case and the isotropic environment, the displacement dispersion, x2, is connected with the diffusion factor D and diffusion time, t, by Einstein’s formula: x2 = 2 Dt. The higher the value of diffusion factor, the longer an average distance of particle’s displacement (within the same time). The diffusion coefficient unit of measurement is meters squared per second—the square of the circle where the particle would be in 1 s. In the simple experiment (Fig. 1.1), the drop of paint in water always colour produced a coloured circle, and the radius of this circle infinitely grows with a time (Fig. 1.1a). In the case of impenetrable, closed border, the painted area will not grow outside this border (Fig. 1.1b).
Fig. 1.1a–c Schema of the experiment with drops of paint: types
of diffusion motion. a Free diffusion, b uniformly limited diffusion (isotropy), c non-uniformly limited diffusion (anisotropy)
Chapter 1
In the case of presence of obstacles on the water surface, the paint particles bypass them, and the painted area has an elliptic form (Fig. 1.1c). Thus, after awhile since the beginning of the experiment, the painted area is characterised by the size of the spot, its form, and its orientation on the plane. In a three-dimensional case, the law of displacement probability density is set by probability of particle transition in time t from one point, r0, to another point, r. In the simple case of free diffusion in an unlimited, isotropic, and homogeneous environment, this probability has a Gaussian distribution. The volume in which a particle would be contained in time t is sphere with the centre in r0; in the case of the limited isotropic diffusion, the sphere radius would not increase since some moment of time, and in cases of anisotropy or particle speed dependence from the motion direction, the sphere becomes ellipsoid.
1.3.1.1
Diffusion-Weighted MRI
The motion of the water molecule in live tissues occurs within the cell limits (the limited diffusion), as well as in intercellular spaces among structures, which restrict the molecules motion but still leaves them some freedom for manoeuvring between obstacles (the complicated diffusion). The term of measured or apparent diffusion coefficient was introduced to characterise the diffusion proton motion in a complex environment. Generally, this value depends on the structure and microstructure of substance, in which the water molecules are diffusing: D = 2.5 × 10–3 mm2/s in free water at body temperature (Tanner 1970). In the real biological environment, water molecules can encounter natural barriers, such as like cellular membranes and large albumin molecules, which that interfere with free motion of protons. Therefore, in practice, the apparent diffusion coefficient is calculated, and its value is lower than diffusion coefficient for pure water at temperature. The first diffusion-weighted MRI (DWI) was done in 1985 (Le Bihan et al. 1985). DWI was introduced into clinical practice together with third-generation MRI scanners (Le Bihan 1991). Spin echo-echo planar pulse sequences (SE-EPI) with two diffusion gradients (DG) of the same amplitude (G) and duration –δ are used to obtain DWI images. It is possible to apply DG in different directions, for example, in a direction of one of coordinate axes. The degree of weighting signal on diffusion rate is set by the value of the so-called diffusion factor, b, which is a parameter of the pulse sequence timing and depends on DG duration and delay time between them: b = γ2G2δ2(∆ – δ/3). In this formula, γ is the gyromagnetic ratio, G the amplitude, δ is the duration of each diffusion gradient and ∆ is a delay between diffusion gradients. The diffusion factor b is measured in seconds per squared millimetre. The measurements in DWI are performed two times, first with b = 0 s/mm2 and then with b = (500–7,000) s/mm2. DG applied along the direction of each coordinate axes of the scanner are x, y and z in DWI. In diffusion tensor MRI (DTI) measurements are performed (at least) in six DG directions.
Neuroradiology: History and New Research Technologies
5
Fig. 1.2a–d DWI (combined series), obtained with b = 500 s/mm2 (a) and b = 1,000 s/mm2 (b). c,d ADC maps for the same scans
The phase changes caused by the DG, in stationary protons (very low diffusivity) in the structure of macromolecules, are completely compensated by the moment of registration. MR signal from such protons corresponds to T2 of the tissue and is equal to a signal registered in SE-EPI sequence at b = 0 s/mm2. The protons participating in diffusion motion with water molecules get the additional phase, and MR signal from them is lowered. Diffusivity of water in a tissue is visually estimated by the degree of MR signal attenuation on DWI. In our examination, the gradient fields with amplitudes of G = 11 and 22 mT/m were used, which corresponds to diffusion factor values of b = 500 and 1,000 s/mm2, respectively. For each DWI–EPI examination, we obtain five series of scan images: one series is a T2 MRI; three at a supply diffusion gradient on each direction (х: anterior–posterior, y: right–left, and z: superior–inferior); and one, the so-called combined series for average diffusion coefficient (ADC) calculation, without taking into account the anisotropy in a tissue. In Fig. 1.2a,b, the DWI (the combined series) is shown. These images were obtained at b = 500 s/mm2 (Fig. 1.2a) and 1,000 s/mm2 (Fig. 1.2b). The visible (by eye) decrease in MR signal intensity occurs in the case of the phase signal changing in one or two times. It is possible to estimate fast proton diffusion with the ADC of 5 × 10–3 s/mm2 for b = 500 s/mm2. For b = 1,000 s/mm2, the optimum conditions for MR signal decrease visualisation would be for the protons diffusing more slowly, with the ADC on or about the order of 2.5 × 10–3 s/mm2, i.e. almost the same as in free water. With even higher
b values, it is possible to estimate the speed of diffusion motion in cell compartments (Le Bihan 2002). For a quantitative estimation of diffusion water properties in tissue, the parametrical diffusion maps are built on the colour of each pixel as it corresponds to the ADC (Fig. 1.2c,d). On the diffusion map, tissues with high speeds of water diffusion have blue– black colours.
1.3.1.1.1 Diffusion Anisotropy Diffusion anisotropy is a dependence on direction of molecular diffusion ability. The diffusion maps obtained at DG action (effect) on six different directions in the space at b = 1,000 s/ mm2 are shown in Fig. 1.3a–e, and diffusion coefficient maps in a direction of coordinate axes x, y and z are reflected in Fig. 1.3f,h. The anisotropy of diffusion characters of corpus callosum white matter is clearly visible on the images. Water molecules easily diffuse alongside nerve fibres; however, their motion in the transverse direction is limited by the impenetrable myelin membrane. For the description of diffusion properties changing with a direction, mathematical tensors are used. The diffusion tensor is defined as: � Dx x = D � D yx � Dzx −
Dx y Dy y Dz y
D xz � D yz � Dzz �
6
Chapter 1
Fig. 1.3a–i DWI obtained at DG application at six different directions (a–f), and diffusion coefficient maps in a direction of coordinate axes
x (g), y (h), and z (i)
Neuroradiology: History and New Research Technologies
The diffusion tensor is symmetrical, i.e. Dxy = Dyx, for any pair of indexes. This property reflects physical properties of the real environment, namely, diffusion properties would not change from the initial and final points of a diffusing molecule trajectory. Thanks to the diffusion tensor’s symmetry, the six tensor coefficients (three diagonal and three non-diagonal) are sufficient for characterisation of diffusion properties of water molecules. Six coefficients of diffusion tensor define the form of a diffusion ellipsoid, its sizes and its orientation in space (Pierpaoli 1996; Mori and van Zijl 2002). The diffusion isotropy means that diffusion motion of molecules does not depend on the orientation of environment, and during observation, the molecule would not leave the limits of sphere with a radius D, where D = (Dxx + Dyy + Dzz)/3 = ADC. Diffusion anisotropy assumes that, during the observation, due to orientation of environmental elements, the molecule would not leave the borders of the “diffusion ellipsoid” with half-axes λ1 λ2 and λ3; here λ1 λ2 and λ3 are the values of diffusion tensor (eigenvalues). The diffusion anisotropy can be quantitatively estimated with the use of the difference between the diffusion ellipsoid and the sphere with radius Dcp, for instance, with the help of the fractional anisotropy (FA) coefficient, relative anisotropy (RA) coefficient, index of anisotropy (IA) and so forth (Pierpaoli 1996). Diffusion tensor MRI (DTI) is used to visualise the anisotropy of water diffusion in the tissue.
7
In DTI, the line of nerve fibres forming the nerve tracts (paths) may be visualised via the diffusion ellipsoids’ orientation, by connecting the vectors of diffusion tensor (Fig. 1.4). Connection algorithms are relatively complex, and therefore the various methods of calculation like structural modelling (structural modelling involves following the main diffusion directions), connective models (anatomical and functional connectivity), methods of integrated transformations and spherical harmonics (Q-space spherical harmonics), stochastic models (probabilistic models) and so forth are utilised (Mori and van Zijl 2002; Sen and Basser 2005; O’Donnell 2006). These methods enable the tracing of multiple nerve fibres forming a neural tract; therefore, DTI is often called tractography—a demonstration of neural tracts visualisation. In the simple form, partial diffusion anisotropy is coded by colour, and visualisation of the direction of water molecule diffusion motion in tissue is carried out by colouring the pixels a certain colour, depending on orientation of their respective vector (red for the x axis, green for y and dark blue for z) (Fig. 1.5). DTI is a tool of detection of structural communications between brain departments. Establishing such communication is especially important in the case of volumetric processes and the diseases deforming the anatomic structure or destroying white matter, such as tumours, brain injury, arteriovenous malformations, epilepsy and demyelinating diseases.) (Hesseltine et al. 2007; Holshouser 2006).
Fig. 1.4a–e Orientation of diffusion ellipsoids in voxels (a), in the genu (b) and splenium (c) of corpus callosum, and in the brainstem (d). e MR tractography based on the obtained data
8
Chapter 1
Fig. 1.5a–d Colour maps of anisotropy. The white matter conduction tracts (pathways) are marked by colour. a Map of partial anisotropy, b map of relative anisotropy, c map of anisotropy index, d structural map of anisotropy (according to the directions of the diffusion tensor vectors)
1.3.1.1.2 Clinical Application of DWI and DTI Decrease in ADC speed in brain tissue is a sensitive indicator of presence and severity of ischaemic changes (Moseley et al. 1995). Today, DWI is one of the fastest and highly specific methods of early-phase ischaemic stroke diagnostics (within 6 h of onset), during which there is a therapeutic window for restoration of the affected brain tissue. In acute phase of stroke, the affected area on DWI typically has a high MR signal, whereas the surrounding tissues look dark. The ADC maps provide a reverse-in-brightness picture (Fig. 1.6). Diffusion ADC maps are a tool in ischaemia diagnostics and monitoring of stoke and subsequent chronic tissue degeneration caused by ischaemia. Gradually, by the end of second week, the isointense signal from the affected area(s) replaces hyperintense one. Then the signal becomes hypointense, reflecting the focus of encephalomalacia. The high ADC values are observed in areas of chronic and old lacunar strokes. Currently, this method is perhaps unique, capable of detecting the new ischaemic area on the periphery of an old stroke zone (or widening the stroke area) in patients with newly developed focal neurological signs. Generally, the DWI non-invasiveness and swiftness predetermine its leading role in primary diagnostics of ischaemic stroke. All diffusion-weighted examinations are performed without contrast administration. This is important for critically ill and restless patients, and especially for specialised examina-
tions of brain development in children, beginning with the prenatal period. In the last case, DWI enables obtaining both the additional qualitative (visualisation) and quantitative tissue characteristics; it offers new opportunities of microstructure examination in the process of brain development (Konovalov 2001). DWI and ADC maps provide additional diagnostic information for differentiation of neoplasms with similar signs on T1 and T2 MRI (glioma, tumours with ring-shaped contrast accumulation), peritumoral oedema (vasogenic or cytotoxic) and the presence or absence of intratumoral cysts, to name a few (Mulkern et al. 1999). At the same time, as our experience demonstrates, DWI data alone does not allow differentiation between benign astrocytoma and anaplastic tumours, or between anaplastic astrocytoma and glioblastoma (Kornienko et al. 2000). The information concerning the spreading of infiltrating and growing brain neoplasm is more interesting. In many observations, the peripheral part of tumour (as a rule in the case of malignant glioma) is hyperintense on DWI; presumably it is linked with more dense cellular arrangement in the most actively growing tumour area (accordingly, there is a limitation on diffusive proton motion in this area). We used these data for planning the stereotactic biopsy with obligatory tissue sampling from this peripheral part of an intracerebral tumour. DWI provides invaluable information for inflammatory lesion diagnostics of brain and spinal cord (abscesses, empyema) for the immediate time. Purulent abscess content has
Neuroradiology: History and New Research Technologies
9
Fig. 1.6a–c Superacute phase of stroke. a The affected area has a hyperintense MR signal on DWI (b = 1,000), while normal brain tissues
look dark. The regions of ischaemia in left and right hemispheres of cerebellum are violet (b). c T2-weighted image: there are no MR signal alterations Fig. 1.7a,b Purulent complication after
glioblastoma removal. a Wide operational defect MR T2-weighted image. b DWI: the purulent layers (thickening) on the edges of defect are visualised (hyperintense MR signal)
a typical hyperintense MR signal on DWI and can be easily visualised on pretreatment (before draining) and as well on postoperative images. In addition, DWI can be used in the assessment of drainage intervention effectiveness or in the case of verification of the purulent complication in incision wound (Fig. 1.7). The structural organisation properties of some new brain neoplasms—in particular, meningiomas and neurinomas— enable DWI to predict tumour histological type, with high reliability even before intervention. Based on this method data, the epidermoid and arachnoid cysts can be precisely differentiated. Recently, DWI and DTI methods have begun to be applied to visualisation of a neural tract lines—tractography, especially in diagnosing white matter diseases caused by congenital metabolic defects, traumatic (diffusive axonal lesions),
autoimmune, toxic and radiation damage (Lee et al. 2005) (Fig. 1.8). Tractography is a new and promising technique that enables non-invasive viewing of the brain neural tracts (Batchelor et al. 2006). Despite some technical problems, the first results in tractography application to neurosurgery seem promising (Chepuri 2002). It is possible to plan operational access and to estimate the scope of brain hematoma to be removed, taking into account neural tracts and their involvement in the pathological process (dislocation–deformation, invasion, damage), with an aim to maximise the radical tumour resection and to minimise the subsequent complications (Stadlbauer et al. 2007). The results confirm the value of a new diagnostic MR technique that enables increasing MRI specificity in establishing the correct histological diagnosis, and improves the accuracy
10
Fig. 1.8a–f MR tractography. a Axial projection, structural map.
b Coronal projection, structural map. c T2-weighted MRI, axial scan of patient with glioma. d Construction of the corticospinal tract in
of detecting the various components of tumour growth (tumour, infiltration and peritumoral oedema) and the borders of ischaemic lesion(s).
1.3.1.1.3 Perfusion Examinations Methods of perfusion examination are used to consider and make quantitative estimation of the blood movement that supplies each element of organ or tissue volume. It is widely known that, unlike the majority of parenchymatous tissue, brain tissue does not accumulate glucose, and brain cells can produce energy via anaerobic glycolysis only for several minutes. Meanwhile, the brain consumes about 25% of all glucose consumed in the entire body, and for neurons, the uninterrupted and sufficient supply of oxygen and glucose is necessary. There are complex mechanisms of autoregulation that manage brain perfusion to satisfy the demands of the nervous system for energy (released in a course of metabolic processes). There are several modern quantitative methods of brain haemodynamic examination: MRI, CT with contrast enhance-
Chapter 1
coronal plan in zone of tumour location. e T2-weighted MRI of a patient with metastasis in basal ganglia. f Splitting of the nerve fibres around metastasis
ment, CT with Xe, single-photon emission computed tomography (SPECT) imaging and positron emission tomography (PET). The obvious advantages of CT and MRI are minimally invasive, high sensitivity in tissue microcirculation assessment, high resolution, the short examination time (within the framework of standard protocols), and last, but not least, the reproducibility of results (Sorensen and Reimer 2000; TingYim 2002; Cha 2006; Waaijer 2007). The most widespread perfusion examination in neuroradiology is that performed based on intravenous bolus administration (CT and MRI). The dynamic studies of bolus passage demonstrate its distribution in tissue in each given image pixel, depending on time. The following main haemodynamic characteristics are used for quantitative assessment: cerebral blood flow (CBF), the cerebral blood volume (CBV) and mean transit time (MTT). The blood flow characteristics are measured in the ratio to 100 g of brain tissue. Accordingly, the value of CBV is measured in millilitres per 100 g of brain tissue, and CBF is measured in millilitres per 100 g per minute. The local (regional) CBV is defined as percentage of blood volume in a single element of brain tissue volume. MTT is measured in seconds.
Neuroradiology: History and New Research Technologies
Fig. 1.9 Perfusion CT. a Series of dynamic CT scans, b the concentration–time curve in an artery and vein
1.3.1.1.4 Perfusion CT The modern spiral CT scanners present new opportunities in tissue perfusion examination during the first passage of the iodide contrast bolus. This method has high resolution and provides quantitative assessments of tissue perfusion, and currently, it is one of the most perspective methods. Perfusion CT is based on analysing the CT density increase during contrast media passage through brain vascular structures. Contrast bolus (iodine agent with concentration 350–370 mg/ml, speed of administration is 4 ml/s) is administered intravenously. Spiral CT obtains a series of scans with 1-s intervals, within 50–60 s after contrast administration (Fig. 1.9).
1.4
Perfusion-Weighted Imaging
There are MRI methods of haemodynamic perfusion examination, aided by exogenous and endogenous markers: • Contrast media (theory of non-diffusing markers, or central volume theory) • Arterial spin labelling (kinetic theory of diffusing markers) • Obtaining the images that depend on blood oxygenation level (BOLD) The methods of perfusion assessment during contrast bolus passage are called perfusion-weighted MRI, or PWI. These examination methods are currently widely used in MR diagnostics, especially in combination with MR angiography and MR spectroscopy. PWI uses changes of T1 or T2 tissues contrast due to infusion of gadolinium into blood as a contrast agent. Normally, gadolinium does not pass through blood–brain barrier. It can pass into intracellular spaces only in cases of blood–brain barrier disruptions (Cha et al. 2007). The usual MRCM (MR contrast media) concentration in
11
bolus is 0.1 mmol/l—the same as in standard examinations with contrast enhancement. The CM bolus is administrated quickly (about 2–3 s); the speed of administration is 4–5 ml/s, and higher than in the standard infusion. After the bolus, a buffer solution is administrated. Ideally, the bolus envelope curve should have rectangular form. The bolus passage on consecutive (in time) scans corresponds with the sharp decrease of MR signal intensity. In the process of CM bolus passage through the vascular system, multiple registration of the image from the same location occurs (usually it is 10 different levels). The scanning takes place for 1–2 min. The graph of intensity decrease during CM bolus passage provides the curve “signal intensity–time” in each pixel of the scan (Fig. 1.10). The form of this curve for arteries and veins provides arterial and venous function data; with the help of these data, the haemodynamic tissue parameters are calculated. The regional CBV (rCBV) is estimated on the basis of area under curve “concentration–time”; the MTT calculation is performed on the basis of centre of gravity in CM distribution position, regional CBF (rCBF) = rCBV/MTT. The perfusion maps are built in “off-line” mode in the specialised workstations. PWI uses SE or gradient recalled echo (GRE) pulse sequences. The advantages of EPI-SE are the absence of geometrical distortions and good detection of arterial function in large arteries at the base of the skull. The main shortcoming is the echo time (TE) of 40–80 ms, necessary for maintenance of T2 weighting of the MR signal, which limits the time interval between scans. EPI-GRE provides time resolution of 1 s; however, it cannot obviate geometrical distortions. The method of dynamic T1 MRI is used in cases of examination of CM distribution in extracellular spaces. The time range of a dynamic curve in cases of T1 examination is 3–5 min from the moment of CM administration. The CM passage through the vascular net is accompanied by increase of MR signal intensity in areas of CM accumulation. Dependence S (t) is used for construction of the concentration–time curve, Ct. The steepness of the front of the CM accumulation curve (as well as in perfusion CT) characterises a local blood flow, maximum value of MR signal to local blood flow volume; the form of the concentration curve allows estimation of microvascular permeability of blood–brain barrier. The advantage of perfusion examination with the help of the arterial spin labelling (ASL) method is the possibility of perfusion assessment without CM administration (Chai et al. 2007). The method is based on the proximal labelling of water protons with the help of presaturation. The “labelled” spins (they get the additional phase shift) enter (with the blood flow) the vascular brain bloodstream and account for the decrease of MR signal from microvascular structures on dynamic MRI series. The second series is registered in the absence of saturating radiofrequency pulse. The local blood flow is calculated on the difference between the two series (with presaturation and without). Currently, two modifications of ASL are used, continuous (CASL) and pulsed (PASL). The duration of examination is 15 min in the field of about 1.5 T. The MR signal change due to spin labelling is lower than in the case of bolus CM admin-
12
Chapter 1
Fig. 1.10a–e Perfusion MRI. a Series of dynamic MRI and signal intensity–time curves in normal brain tissue. Patient with meningioma.
b The signal intensity–time curve in an artery (1) and vein (2). c–e CBV maps on different levels
istration, and reaches only 15% of the latter (Alsop and Detre 1998). This method could gain recognition in the clinic, probably with the spreading of high-field MRI with the induction of 3 T or higher. Functional MRI (fMRI) utilises the magnetic properties of blood as an exogenous marker in magnetic field 1.5–3 T (discussed below).
1.4.1 Clinical Applications of CT and MRI Perfusion Currently, perfusion examinations are performed to estimate the haemodynamic of brain tumours in cases of differential diagnostics of brain lesions; for tumour-state monitoring after chemo- and radiotherapy; in diagnostics of the tumour recurrence and radiation necrosis; and in cases of brain injury and CNS damage like ischaemia, hypoxia, large-arteries stenoses, blood diseases, vasculitis and moyamoya disease. Epilepsy, migraine, vasospasm various mental diseases (including dementia), autism, and so forth, are prospective in terms of perfusion methods application. CT and MRI perfusion allow building of parametric maps and quantitative characterisation of areas of hyper- and hypoperfusion, which is especially important in tumour and cerebrovascular disease diagnostics. Perfusion maps provide
important additional information about characteristics of normal and pathological tissues (in areas of tumour, oedema, necrosis, and so forth). In neurosurgery, PWI is used in primary differential diagnostics of malignancy levels of brain neoplasms, in particular gliomas. However, it is necessary to remember that perfusion CT and MRI do not allow specifically differentiating tumours according their histology, nor does it enable estimation of the tumour spreading into brain tissue. The hyperperfusion is focussed within the structure of astrocytoma; it can indicate increase of tumour malignancy because the perfusion level of tumour is related to the development of abnormal vascular net (angiogenesis) and thus, with the tumour’s viability. The abnormal vascular net in a tumour can be the evidence of its aggressiveness. In contrast, the decrease of perfusion in a tumour tissue under the influence of chemo- or radiotherapy can be a sign of response to treatment. Use of PWI in target selection for stereotactic intervention is helpful, especially in cases of gliomas that are characterised by full absence of contrast accumulation with the use of standard CT and MRI (Fig. 1.11). PWI potential is higher in assessment of histological type and spreading of extracranial neoplasms than of intracranial ones (Fig. 1.12). PWI successfully visualises meningioma and
Neuroradiology: History and New Research Technologies
13 Fig. 1.11a,b Glioblastoma of right tempo-
ral lobe. a CT with contrast enhancement does not reveal its pathological accumulation. b CBV (based on CT data) map visualises the area of elevated perfusion: the site of biopsy is marked by a circle (region of interest [ROI] 3); CBV in the tumour increased more than three times in comparison with normal white matter (ROI 4)
Fig. 1.12a–d Perfusion maps on the basis
of skull. CT in patient with cranio-orbital meningioma. a CBV, b CBF, c MTT, d TP (time to pike)
14
neurinoma of cerebellopontine corners according to the high haemodynamic parameters in meningioangiomatoses. In addition, it was demonstrated that there is a clear correlation between local blood flow (CBF, CBV) and direct angiography data in patients with meningiomas (Fig. 1.13). The tumours with radiopaque shadows in the early capillary phase of angiography have especially high perfusion, and such tumours are characterised by high risk of a intraoperational bleeding in the moment of extraction. CT PWI data are highly specific in demonstrating the blood supply of haemangiomas located in posterior cranial fossa; in this case, early and marked contrasting is combined with high perfusion. PWI is used successfully in differential diagnostics of postoperative continued tumour growth and radionecrosis.
Chapter 1
In both cases, standard CT and MR examinations can show the accumulation of contrast in tissues, and in both cases, blood–brain barrier disruptions are observed. Blood–brain barrier disruptions cause CM extravasation in pathological tissues, with subsequent contrast accumulation. However, the pathophysiological reasons in both cases are different. For tumorous tissues, the perfusion increase or the reaching of normal perfusion level are typical, as in necrotic tissues the blood supply is absent. Blood–brain barrier disruptions in cases of tumours are related to the invasive growth of tumour cells and vascular wall damage. In case of radionecrosis, the disruption of blood– brain barrier is an initial step, and it declares itself (unlike tumours) in the form of perfusion decrease (iso- or hypop-
Fig. 1.13a–c Meningioma of sphenoid wing. a CT scan with contrast enhancement, b CBV map demonstrates the large tumour with high
perfusion indicators, c direct angiography confirms the luxury meningioma blood supply in arterial phase
Fig. 1.14a–c Ischaemic stroke in left MCA territory. a ADC map (the stroke is coloured violet-blue and affects the basal ganglia), b CBF map:
area of deep nucleus damage with very low cerebral blood flow parameters (arrow), c MTT map (the area of penumbra is marked by ROI 1, with light blue)
Neuroradiology: History and New Research Technologies
erfusion). The areas of radionecrosis appear as areas of weak blood filling on CBV maps. The time of CM bolus passage is longer than normal, as in cases of ischaemia. Undoubtedly, ischaemic brain damage occupies first place in the frequency of PWI methods being used. Currently, PWI is an integral part of diagnostics in patients in whom cerebral ischaemia is suspected. The first clinical PWI application in brain lesion diagnostic in humans was performed for stroke diagnosis. At present, perfusion MRI is, perhaps, the sole method of early ischaemia verification, capable of diagnosing the haemodynamic decrease in certain brain areas (as the main mechanism of ischaemic damage), even in the first minutes after appearance of focal neurological signs. The combination of PWI and DWI in patients with brain ischaemia enables detection of the heterogeneity of the ischaemic area(s), to distinguish the nuclear lesion (the area of necrosis) and so-called penumbra (the area of ischaemic half-shadow), with only functional changes (Fig. 1.14). The new approach in PWI use is studying the haemodynamic shifts in brain substance in patients with severe stenosis and occlusion of large extracranial vessels. It turned out, for instance, that there is no clear correlation between stenosis level of internal carotid artery and perfusion decrease on the territory supplied by this artery. One of the main reasons for this is the development of collateral circulation with haemodynamic compensation. Generally, careful analysing of these data in vascular surgery leads to more accurate treatment selection for these patients; in particular it limits the indication for extracranial–intracranial shunting.
15
The use of perfusion CT and MR investigations in children for whom the vessels occlusions are rare (characterised by the small probability of vessels occlusion) is especially important. The hyperintense MR signal in T2 consequence in most cases is caused not due to stroke, but to other reasons (for instance, vasogenic oedema, hypomyelinogenesis). PWI could indeed reveal the ischaemic area in children, for whom the small probability of stroke exists (Konovalov et al. 2001). Another example of PWI use is arteriopathy studies in children. Reasons for this study include idiopathic (primary) and secondary vasculitis, the consequences of moyamoya disease, and sickle cell arteriopathy. For such diseases, perfusion MRI sensitivity is compatible with those of perfusion CT with Xe133, and radionuclide methods. PWI has several advantages in anatomical damage visualisation and in detection of pathological and anomalous blood flow, observed, for instance, in cases of collateral circulation. Revealing the pathological circulation in children is especially significant in situations of patient selection for surgical treatment of arteriopathy. The collateral circulation in children with arteriopathy can be extensive at the time of its primary detection. Dynamic perfusion MRI is used in cinema mode for perfusion-loop, revealing collateral circulation assessment, and time of CM passage to tissue estimation. All this makes this method highly informative in detecting and subsequent observation of patients with moyamoya disease. It is considered that, at an initial stage of this disease, perfusion parametrical imaging demonstrates the increased blood flow in the basal ganglia area, altered peripheral cortical perfusion, deficit, or change of the CM passage time. These signs are typical for this disease.
1.5
Fig. 1.15 Haemodynamic response of brain to the increase of neuronal activity for interchange of stimulus and rest periods
Functional MRI
Brain activity mapping enables revealing of the areas of neuronal activation in response to tests, motor, sensor, and other stimulus. Until recently, similar mapping was performed with the help of radionuclide methods: PET and SPECT imaging. Functional MRI (fMRI) is based on increase of brain haemodynamics in response to cortical neuronal activity due to certain stimulus (Ramsey 2002; Pouratian et al. 2003; Sunaert 2006). BOLD EPI-GRE registers hyperintense MR signal from active areas of the brain cortex. The registration time of one MR image is about 100 ms. fMRI signal intensity, registered by physiological load, is compared with the intensity, registered in the event of its lack. During MRI examination, the stimulation periods (duration of 30 s) alternate with control periods (without stimulation) of the same duration (Fig. 1.15). The total number of scans registered during the examination reaches 20,000. This method of stimulus presenting is called a block paradigm. The areas of statistically significant MR signal increasing during activation, revealed in the course of subsequent mathematical processing of images, correspond to areas of neuronal activity. They are marked with colour—this way the neuronal activity maps are built and these maps are im-
16
Chapter 1
Fig. 1.16a–c fMRI neuronal activity maps of cortical motor centre activation in different patients with intrinsic tumours of the paracentral
area, imposed on a T1 image
Fig. 1.17a–c fMRI maps imposed on 3D brain models. a Patient with a brain tumour of the right frontal lobe, b interrelation of Broca’s area in patient with glioma of the left temporal lobe, c interrelation of motor centres in the case of bilateral stimulation in patient with astrocytoma of the left posterior frontal lobe
posed on T1 MRI sequences (Fig. 1.16). Map construction methods (for instance, brain wave algorithms) subtract images obtained during neuron stimulation from control images obtained in the absence of stimulation. The subtracted image is imposed on a control scan according to its location, and areas of increased neuronal activity are marked with colour. The revealed functionally significant areas could be “imposed” on a T1 MRI sequence of the same section or on a three-dimensional (3D) brain model, and thus it is possible to estimate the ratio between the affected area (tumour) and functionally active brain areas, for example, motor, sensory or visual cortex (Fig. 1.17).
1.5.1 Clinical Application of fMRI Neuronal activity mapping enables planning the surgical approach and studying of the pathophysiological processes in brain. This method is used in neurosurgery in studying cognitive functions. Its perspective is in revealing the epileptic foci. Currently, fMRI is an integral part of MRI protocol in patients with brain tumours located close to the functionally important brain areas. In the majority of cases, the examination results adequately reflect the location of sensomotor, speech and acoustical areas of brain cortex. However, according to
Neuroradiology: History and New Research Technologies
Fig. 1.18 The calculation of the radiation dose to brain tumour depending on location of functionally significant cortical areas
literature and our own study, 8–30% of all observation are not informative due to motion artefacts, lack of precise tests execution by the patients and damage to the above-mentioned cortical centres by tumours. In cases in which fMRI can locate active cortical areas, in 87% of cases there is a correspondence with the results of intraoperational electrophysiological methods, within 1-cm limits, and in 13% of cases, within 2 cm. This is evidence of the high accuracy of the fMRI technique (Nennig et al. 2007). Performing fMRI (currently it is conducted for somatosensory and visual cortices) and tractography with mapping of the functionally active cortical areas, pyramidal or optic tracts. Imposition of these maps over 3D brain images is promising within the framework of one MRI examination for patients with brain tumours. Based on these data, neurosurgeons plan the interventional approach and estimate the volume of neoplasm resection, and radiologists assess the areas of radiation and its distribution in tumour (Fig. 1.18).
1.6
17
detected in vivo in the proton MR spectrum: N-acetylaspartate (NAA), 2 ppm; choline (Cho), 3.2 ppm; creatine (Cr), 3.03 and 3.94 ppm; myo-inositol (mI), 3.56 ppm; glutamate and glutamine (Glx), 2.1–2.5 ppm; lactate (Lac), 1.32 ppm; and a complex of lipids (Lip), 0.8–1.2 ppm. The MR spectrum contains the extensive information about a substance. The peaks’ positions determine a chemical composition, and their width reflects the T2 relaxation time. The area under resonant peak is proportional to proton density and allows calculation of the metabolite concentration. Proton MRS has grown from the high-resolution nuclear MRS. In adjusting of the MR spectrum, the adjusting of MR scanner during examination (prescan) plays a significant role. Currently in proton MRS, two basic methods are used, single voxel (SV) and multivoxel (MV, or chemical shift imaging). MRS is a single-stage detection of spectra from several brain areas. Multinuclear MRS, based on phosphorus, carbon and other element nuclei, are entering clinical practice (Rinck 2003). In the case of SV-MRS, only one brain element (voxel) is chosen for the analysis. The metabolite’s peak distribution on the chemical shift scale (in parts per million) is obtained based on analysis of the structure of frequencies in a signal registered from this voxel (Fig. 1.19). SV-MRS uses pulse sequences point-resolved spectroscopy (PRESS) or stimulated echo acquisition mode (STEAM). STEAM has higher resolution on frequency, but it is very sensitive to the patient’s motions. Resolution of PRESS is a bit lower than is STEAM; however, it is less sensitive to motion. The ratio between metabolites peaks in a spectrum, decrease or increase of the height of separate peaks in a spectrum, are like fingerprints of brain biochemistry: on their basis, it is possible to make a non-invasive assessment of the biochemical process in tissues.
Proton MR Spectroscopy
MR spectroscopy (MRS) is a non-invasive method of brain metabolism assessment. Proton (1Н) МRS is based on a “chemical shift”—the change of proton resonant frequency. This term was developed by N. Ràmsey in 1951, for defining a distinction between frequencies of separate spectral peaks. The chemical shift measured unit is in parts per million (ppm). Following are the main metabolites and corresponding values of the chemical shift; peaks of those metabolites are
Fig. 1.19 Single-voxel proton MRS of brain tissue in a normal volunteer. The peaks of main metabolites are marked on the image
18
MV-MRS simultaneously obtains MR spectra for several voxels, and thus it is possible to compare spectra from different elements in an examination area (Fig. 1.20). Processing of the MV-MRS data enables construction of a parametrical map of brain. The concentration of particular metabolites on this map is marked by colour, and thus it is possible to visualise the metabolite distribution in brain, i.e. to obtain an image weighed on the chemical shift. NAA is the most visible peak in the 1Н spectrum (at 2 ppm). In reality, this peak includes different combinations of macromolecules with NAA: N-acetylaspartylglutamate, glycoproteins, and amino acid residues, and thus this peak could be more appropriately termed “N-acetyl groups”. It is considered that in the adult brain, NAA plays at least two roles: (1) as a predecessor of brain lipids, and (2) as a participant in coenzyme A interactions. Some researchers believe that NAA is metabolically inert, and it participates only in maintenance of “deficiency anion” balance in neutral tissues, so it is the indicator of processes with neurotransmitter–neuromodulator participation, and its basic function is to be the form of free storage of aspar-
Chapter 1
tate (Ureniak et al. 1992). In an adult brain, the concentration of NAA in the cortex is higher than in white matter, as the majority of NAA is located in neurons and their branches. Acetyl-CoA-l-aspartate-N-acetyltransferase is a synthetic enzyme used for obtaining NAA in mitochondria. Acetoaspartase is an enzyme that decomposes NAA, and it is mainly located in astrocytes; thus, NAA decomposition occurs mainly in glial cells, and that explains the low NAA concentration in mature glia. Due to the mainly neuronal and axonal NAA location, the NAA peak decreases in cases of neurodegenerative diseases. Animal experiments have confirmed that decreased NAA correlate with neuronal necrosis. Absolute or relative (in relation to creatine) decrease of this peak is considered an indicator of neuronal and axonal damage. However, as NAA is synthesised in mitochondria, theoretically, the exhaustion of energy without permanent neuronal damages could lead to temporal NAA decrease. In children, the NAA concentration in grey and white matter is identical. Rather high concentration of NAA in immature white matter is related with very high activity of lipid synthesis; research of immature brain demonstrated that oligodendroglia predeces-
Fig. 1.20e–f Multivoxel proton MRS in a patient with a brain tumour. a Spectra presentation in each voxel; b enlarged image with measured
points placement; c spectrum of tumour’s tissue, with typical glioma metabolite changes; d–f colour map of different metabolite contents
Neuroradiology: History and New Research Technologies
sors have twice more NAA than do underdeveloped neurons. The choline peak at 3.21 ppm contains the cumulative contribution of trimethylammonium protons (–N(CH3)3+) in choline, betaine and carnitine plus Н5 protons of mI and taurine. The choline contribution is a sum of signals from several choline-containing chemical compounds (phosphoryl choline, glycerophosphoryl choline and free choline), and probably together with choline, which is present in a form of a polar head group in lipid membranes. MRS might not detect the compounds of choline embedded in a membrane; however, in the case of cell membrane destruction caused by the disease, choline is released, accumulated and may be detected. Choline is a structural component of cellular membranes, especially myelin membranes. The choline peak tends to increase in highly malignant tumours and neurodegenerative diseases. Focal inflammation, which leads to considerable local cellularity and often to significant cellular membranes damages, could also result in increasing of choline peak. The creatine peak at 3.03 ppm is caused by protons of methyl (CH3) group of creatine, phosphocreatine, lysine and glutathione. It appears that phosphocreatine is the basic molecule for maintenance of energy-dependent systems in all brain cells. Its concentration is maximal in a cerebellum, followed by grey, and then by white, matter. Usually, it is assumed that the general creatine level is stable in different situations; therefore, the height of creatine peak is often used as reference in comparison with the height of other metabolites peaks. MI that has two peaks at 3.56 and 4.06 ppm, and it is supposed it serves as storage of membranous phosphoinositides, which are the second messengers of the hormonal systems, and which participate in CNS enzyme regulation. It is one of major growth factors, and it is a predecessor of phosphatidylinositol, which in turn is a part of the lipid layers of cellular membranes. It is located primarily in glial cells and therefore could serve as a specific glial marker. Its other possible functions include osmoregulation, cellular nutrition and detoxication. The low combined peak at 3.56 ppm is from glycine and inositol-1-phosphate. Scyllo-inositol is an isomer of mI, which is not exposed to metabolic changes that could inhibit transport and mI (embedding) association with lipids. The singlet peak at 3.35 ppm is believed to originate from the six protons of methane in a molecule of cyclic alcohol of scyllo-inositol, not from taurine as was thought previously. The singlet nature of resonance is caused by a chemical shift, and it is in agreement with biochemical concentration levels of mI compounds, and elimination of the other metabolites of 1Н MRS spectra of mammalian brains in vivo as well as in vitro. The presence of glucose in brain tissues can be detected with MRS, with short TE time by a singlet at 3.43 ppm. The area under this singlet can be used for calculation of brain glucose concentration. It is possible to detect lactate, which is detected by its typical doublet located in 1Н MRS spectra around 1.32 ppm, in trace quantities corresponding to terms of pregnancy. It is believed that lactate, if found in greater quantities, especially in the first hours of life, is an indicator of brain damage. However, lactate presence in 1Н MRS is a normal finding in prematurely born
19
children. The small peak present in the fetus decreases toward 40 weeks’ gestation. Lactate concentration varies as the brain matures—in newborns, it is higher in less- matured areas of the brain, such as parietal, anterior frontal and temporal. In more mature brains, lactate concentration is higher in the basal ganglia and central gyri. In a case when 1Н MRS has a short TE, several small peaks appear in 1Н MR spectra at 2.1 and 2.4 ppm, corresponding to the protons in glutamine and glutamate. Unfortunately, in the case of a magnetic field induction of 1.5 T (usually used in the clinical setting), these peaks overlap, and their separation is difficult on a background of NAA peak. In all probability, with the use of higher magnetic fields, these peaks could become distinguishable, and their analysis could help with detection of metabolic brain damage (which is accompanied by a change of the glutamate peak). Currently, the following areas of proton MRS clinical application are being considered: injury, metabolic and mitochondrial damages, as well as inflammatory and volumetric disorders.
1.6.1 Brain Tumours MRS is now widely used in an estimation of various volumetric brain formations (Meng 2004; Hourani 2006). In spite of the fact that according to MRS data, it is impossible to predict with sufficient confidence the neoplasm histological type, nevertheless, the majority of researchers agree that tumoural processes as a whole are characterised by a low NAA–Cr ratio, increase in Cho–Cr ration, and in some cases, by the lactate peak (Fig. 1.21). In the majority of performed MRS examinations, proton spectroscopy is used in differential diagnostics of astrocytoma, ependymoma and primitive neuroepithelial tumors (PNET). It is noted that typical signs of astrocytoma and ependymoma are the decrease in the NAA–Cho ratio and increase in the ratio of Lac–Cho peaks in relation to those in a healthy hemisphere. In comparison with these tumours, PNET are characterised by an increase in the NAA–Cho ratio and a lower Lac– Cho ratio, which is related to a higher level of Cho in patients with PNET, as with malignant neoplasm. For astrocytoma, in general, the increase of the Cho peak, the change of mI peak (depends on the malignancy level), the significant reduction of the NAA peak and the appearance of a Lac peak are typical. (In some cases, the combination of Lac and Lip peaks is observed, representing single Lac–Lip complex.) For benign astrocytoma, the reduction of NAA peak is typical, and the increase of Cho peak is observed. The height of the mI peak can remain unchanged, or it can rise insignificantly in comparison with contralateral tissues not affected by tumours. The Lac peak is characterised by small elevation, and in rare cases, it cannot be detected at all (Fig. 1.21a). The Cho and Lac peak rise, while the mI peak falls with the increase of malignancy level—in particular, in cases of anaplastic astrocytoma (Fig. 1.21b). The NAA peak is reduced in comparison with its height in the spectrum of benign astro-
20
Chapter 1
Fig. 1.21a–c T2 MRI and proton MR spectra of gliomas with various malignancy levels. a Astrocytoma grade I–II, b anaplastic astrocytoma, c glioblastoma
cytoma. The marked or full reduction of NAA and mI peaks, and the sharp increase of the Lac peak, are observed in spectrum of glioblastoma, which is characterised by the presence of a necrosis area. At the same time, the Lip peak appears and overlaps the Lac peak, and visually, these peaks looks like single complex (Fig. 1.21c). Generally, the height of Cho peak is sharply increased. In clinical practice, it is important to use MRS during postoperational period for diagnostics of the continued neoplasm growth, tumour relapse or radiation necrosis. As a rule, treatment of brain tumours is a combination of surgery with chemo- and radiotherapy. However, current methods and doses of radiotherapy could cause the death of not only tumour cells, but also of healthy cells, especially in cases of lowered sensitivity threshold for radiotherapy. First, endothelium cells of vessels suffer, then brain oedema appears, and as a result, a zone of radiation necrosis could appear. According to statistics, in more than 5% of all patients who undergo radiotherapy because of a neoplasm, brain damage is diagnosed by the end of the first year near the tumour as well as in other areas. The differential diagnosis between the continued growth, tumour relapse and radiation necrosis is extremely complicated, even with functional CT and MRI examinations. The tumour and radiation necrosis both have the similar CT and MRI pictures. CM accumulation in radiation necrosis is almost the same as in an area of tumour growth. In such cases, 1Н MRS is a useful additional method in differential diagnostics. In a radiation necrosis spectrum, the so-called dead peak, a wide Lac–Lip complex in the range of 0.5–1.8 ppm on a background of a full reduction of other metabolites’ peaks, is a typical attribute. In some cases, the Cho peak can be observed, which complicates the differential diagnostics of radiation necrosis and relapse of tumour with necrotic component (glioblastoma, metastasis).
The diagnosis of lymphomas is an important neuroradiology problem. Differential diagnostics of these tumours based on only routine CT and MRI is complicated, and combined chemo- and radiotherapy treatment is more preferable than surgical removal (Kornienko 2004). Therefore, the correct diagnosis influences the tactic choice in treatment and the prognosis of disease. In the majority of cases, it is necessary to differentiate lymphomas with glial tumours and metastasis. The common trend of changes in peaks of Cho, Lac and NAA is observed in lymphoma spectrum as well as in that of astrocytoma. However, these changes are different. With the lymphoma spectrum, the changes of peak heights are not so expressed. The Cho peak increases moderately, and the increased of peak of the Lac–Lip complex is substantial, whereas the decrease in the NAA peak is insignificant.
1.6.2 Ischaemic Stroke Usually, clinical signs and the patient’s medical history provide the physician enough information for establishing the correct diagnosis in an overwhelming majority of the cases. Nevertheless, in an outpatient practice, it is sometimes necessary to differentiate ischaemic lesion from primary brain tumours (low-malignant astrocytoma). CM administration does not provide sufficient information since in an acute stroke phase, there is no brain–blood barrier damage, and CM might not accumulate in the affected area. The same is true of astrocytoma. Proton (1H) MRS use in such cases facilitates considerably differential diagnostics and an establishment of final diagnosis (Podoprigora et al. 2003). In addition, 1H MRS performed permits estimation of the efficiency of conservative treatment and prognosis. In the first hours after an ischaemia onset, anaerobic glycolysis begins in the affected brain area, i.e. Lac appears and its
Neuroradiology: History and New Research Technologies
21
normal values in repeated examinations (dynamic observation) is a favourable prognostic sign. The main metabolites' continued peak reduction combined with the appearance of the Lac peak indicates cell death in the ischaemic area. Another aspect of the use of MRS is differentiation of the primary and secondary lesions revealed in the initial infectious and demyelination processes. Results of infection diagnostics are the most indicative (Pronin et al. 2002). In an abscess spectrum, there is a peak of the Lip–Lac complex as well as peaks specific for abscess content, such as acetate and succinate (the products of anaerobic glycolysis of bacteria), and amino acids valine and leucine (proteolysis products) on a background of absent core metabolite peaks (Fig. 1.22).
1.6.3 Epilepsy Fig. 1.22 Proton spectrum from the central area of abscess (peaks of
metabolites revealed on the spectrum are marked)
level grows quickly, so the Lac peak is revealed in a spectra of acute and subacute ischaemic phases. Hypoxia leads not only to neurons’ dysfunction, but also to their death, which results in the decrease of neuronal mass in affected area. In the spectrum, it is reflected in the form of moderate reduction of the NAA peak. The behaviour of the Cho peak in the case of ischaemia is not so clear. Its decrease is observed in the majority of cases, but this peak increases in others. Possibly, in phases of acute and subacute ischaemia, the Cho peak increase could be related to damage of the integrity of myelin fibre membranes and release of metabolites. At later stages, the Cho concentration decreases, possibly caused by reduction of cell numbers due to their destruction, and accordingly, due to the reduction of total mass of cellular membranes containing Cho. The restoration of the main metabolite peak heights toward
Diagnosis of epilepsy includes numerous methods and examinations, and MRI is only one of them. At the same time, today MRI is the sole method that characterises anatomic changes in a targeted brain area, for example, in the case of medial temporal sclerosis or cortical dysplasia. MRS in such cases is an additional method of brain dysfunction detection since it reveals a decrease in the NAA peak and NAA–Cr ratio in the hippocampus and in an area of dysplastic changes in brain tissue.
1.6.4 Metabolic Disorders MRS is an informative method for estimation of metabolic damages and primitive lesions of white matter in children. Although MRS is not very specific in case of leukodystrophic and metabolic CNS damage, its results nevertheless narrow the pool of possible brain tissue diseases. The majority of the above-mentioned forms of brain damage lead to NAA peak decrease due to neuronal–axonal degeneration and brain tissue loss (Fig. 1.23). In the case of methochromatic leukodystrophy, MRS reveals the significant decrease of the NAA
Fig. 1.23a–c Leukodystrophy in a 6-year-old child. MRI in T2 (a) and T1 (b) reveals areas of pathological hyperintense MR signal of uneven
form behind the posterior horns of the left ventricles. MR spectrum from the pathological area demonstrates the decrease of the NAA peak and the increase of Cho and mI peaks (c)
22
Chapter 1
peak and moderate increase of the Lac peak. A decrease of the Glx peak and an increase of the mI peak are observed. In the case of Canavan’s disease, MRS detects increase of the ratio of NAA–Cho and NAA–Cr peaks. MRS is a useful method of the brain condition estimation in patients with adrenoleukodystrophy. In this case, MRS detects the marked decrease of NAA–Cr and NAA–Cho peak ratios, the increase of Cho–creatine ratio, and the rise of Glx, mI and Lip peaks in an area of maximal changes, revealed with the help of standard MRI. The MR spectral changes in several types of hyperglycaemia including with the increase of glutamine peak (3.55 ррm) are relatively specific.
1.7
Phosphorus MR Spectroscopy
Phosphorus (31Р ) MRS, which utilises resonant frequencies of phosphorus 31Р nucleus in various chemical compounds, is often performed on modern high-field MR scanners. The resonant frequency of 31Р is approximately 0.405 from resonant frequency of a hydrogen atom nucleus in water molecule. The main metabolites of phosphorus spectrum are: phosphomonoesters (PME); inorganic phosphate (Pi); phosphodiesters (PDE); phosphocreatine (PCr); and adenosine triphosphate (ATP), which has three peaks, α, β and γ, as each ATP molecule contains chemically variously three atoms of phosphorus. In Fig. 1.24, the phosphoric brain spectra of an adult with a normal brain (Fig. 1.24a) and patient with astrocytoma (Fig. 1.24b,c) are presented. In the normal brain, the highest central peak in a phosphoric spectrum is phosphocreatine (2.1 ppm). The PDE peak is the second highest, and it reflects the presence of lipid predecessors like phosphoryl Cho, phosphoryl ethanolamine and Lip. This peak is located to the left of the PCr peak, and then the Pi and PME peaks follow. The PME peak includes MR signals from phosphates of sugars: glucose6-phosphate, sucrose-6–phosphate, and hexose-6-phosphate, which partially overlap. To the right of the PCr peak there are three ATP peaks (γ, α and β). PCr and ATP play important
Fig. 1.24a–c Phosphorus MR spectra obtained in the magnetic field of 1.5 T. a 31Р spectrum of a normal adult brain. The main metabolites of the phosphorus spectrum are: phosphomonoesters (PME); inorganic phosphate (Pi) phosphodiesters (PDE); phosphocreatine
roles in brain tissue energy metabolism. Phosphorus spectra are quantitatively estimated according to the ratio of metabolite peak heights to αATP peak height. The homeostasis abnormality accompanied by the decrease of PCr and PDE peaks and increase of ATP peak is typical for tumour tissue (Maintz et al. 2002; Karsmar et al. 1991). Phosphoric spectra in patients with astrocytoma demonstrate visible decrease of PDE–αATP ratio in relation to normal spectra (Fig. 1.24). A meningioma phosphoric spectrum is often characterised by decrease of PCr–αАТР and PDE–αАТР (Maintz et al. 2002). A lymphoma spectrum shows substantial increase of the RME–αАТР ratio (Karsmar et al. 1991). According to some authors, radio- and chemotherapy leads to gradual restoration of the height of phosphoric spectrum peaks (Maintz et al. 2002; Karsmar et al. 1991), but this report requires additional investigations. Chemical shift between Pi and αATP peaks is used for the estimation of intercellular liquid acidity (pH), and the shift between Pi and PCr peaks for pH estimation in tumour tissue (Karsmar et al. 1991). According to Maintz et al. (2002), pH in brain tissue of an adult normally is 7.04 ± 0.01; in tumour tissue pH increases to 7.12 ± 0.02 in glioblastoma and to 7.16 ± 0.03 in meningioma. Changes of metabolite peak heights of the phosphoric spectrum are observed during brain development in children within first the 3 years of life (van der Knaap et al. 1990), in cases of degenerate diseases (van der Knaap et al. 1991), hydrocephaly (Braun et al. 1999), ataxia (Bluml et al. 2003) and creatinine deficiency syndrome (Bianchi et al. 2007). MR scanner adjustment (prescan) is often done manually, and 31Р MRS examination takes a long time. However, current work on the use of echo-planar pulse sequences for fast brain mapping based on 31Р MRS is being done (Ulrich et al. 2007). Fast mapping methods of products of phosphorus metabolism open the opportunities of visualisation of bioenergy changes during brain simulation, for example, the block stimulation in fMRI.
(PCr); and adenosine triphosphate (ATP), which has three peaks, α, β and γ. b T2-weighted image of a tumour. c 31Р spectrum of a patient with anaplastic astrocytoma, demonstrating the decrease of PDE–αATP peaks ratio
Neuroradiology: History and New Research Technologies
1.8
Neuroradiology and Information Technologies
As the volume of diagnostic information grows, network support and the use of specialised workstations for the expanded digital processing of examination data is becoming increasingly more necessary. Workstations and digital diagnostic devices use the same user interfaces, browser program for examination results, programs of СT and MRI data processing, and they are equipped with the programs for recording images on CD and other magnetic carriers which assures that the multimodal operations function well. The use of digital technologies in modern radiology is the standard for all developed countries, and it is taking root in Russia. The old film technologies of data presentation and storage of films are gradually become obsolete. The need for additional computer processing for obtaining more detailed information on the pathology in question is arising more often (Rodionov et al. 2002).
Fig. 1.25a–i 3D modelling based on CT and MRI for planning of neurosurgical intervention. a 3D superposition of 3D models of bones, brain vascular structures and tumour, with the use of CT (meningioma of posterior cranial fossa), b dural arteriovenous fistula of parietal region (CT angiography), c superposition of cortical surface and convex vein (based on MRI), d 3D superposition of bones, brain vascular structures and tumour (CТ angiography, volume ren-
23
Modern superfast spiral CT scanners and high-field MR scanners are constructed with the use of the newest technical achievements, modern hardware and the software. In diagnostically complex cases, after CT and MRI imaging, the neuroradiologist can continue to study the obtained data for making a diagnostic conclusion without the patient present. For this purpose, the diagnostic images can be digitally stored and transferred to a graphic computer station for the subsequent processing and analysis by a local network or by the Internet. Modern diagnostics requires additional postprocessing on special graphic computer stations equipped with powerful software packages with mathematical analysis and modelling, which can be performed, again, in the absence of the patient. Use of remote graphic stations for postprocessing is prompted by the necessity of 3D image construction, including the combined models of soft tissues of a head, skull, brain and its vascular system for neurosurgery intervention modelling (Fig. 1.25).
dering, petroclival meningioma), e 3D superposition of 3D models of the skin surface and tumour (falx meningioma), f 3D model of cervical part of vertebra (view from the internal surface of vertebral canal to the intervertebral foramens in the case of a removed section of vertebra in patient with spondylosis and intervertebral foramen compression at the C3–C4 level), g–i see next page
24
Chapter 1
Fig. 1.25a–i (continued) 3D modelling based on CT and MRI for planning of neurosurgical intervention. g 3D processing of volumerendered data of CT angiography of cervical vessels, h 3D process-
ing of CT data in patient with a fracture of a thoracic vertebra with dislocation, i 3D model of ventricular system in child with open hydrocephalus
The analysis of DTI (calculation of average and anisotropic diffusion speed, construction of parametrical maps of fibre tracing, and so forth), perfusion examinations (calculation of blood flow parameters, parametrical maps construction), and other such parameters, requires mathematical processing. As a rule, subsequent viewing of the obtained results, for example, in clinical conferences or directly in operation room of a surgical hospital, is also carried out on the graphic stations. The special unified data format Digital Imaging and Communications in Medicine (DICOM 3.0) developed by the American College of Radiology (ARC) and National Electrical Manufacturers Association (NEMA) is used for storage and transfer of medical images in modern radiology. In modern medical clinics, imaging results are often stored on
a short-term basis in the operative memory of the diagnostic device (CT, MRI, angiosystem) or in the operative memory of a graphic station. However, operative memory is limited and is not intended for the long-term data storage necessary in scientific work. As a rule, the archiving of examination results is necessary for long-term storage on any replaceable data carriers (for example, magneto-optical discs). Another variant is the use of Picture Archiving and Communication System (PACS), which requires the creation of special remote archives on servers in which rather large files can be stored for a long time in a “hot” state, and in this case, the interesting information is quickly accessible via network for search and viewing, and if necessary, for new data processing. The digital storage of medical data is more preferably in comparison with film archives. Films could be stored for about 10 years in cases of strict compliance with all storage rules, while digital archives could exist indefinitely. Images are accessible for repeated calculations and analysis, which is especially important in neuroradiology, due to frequent necessity of dynamic observation for the patient during long periods. Taking into account the high cost of film and significant expenses for service of photographic developing apparatus, it is no surprise that digital technologies of storage, transfer and representation of the medical information are increasingly coming into practice all over the world. The Neuroradiology Department of the Burdenko Neurosurgical Institute of Russian Academy of Medical Science developed a system to organise the information radiological system for obtaining, storage, transfer and postprocessing of diagnostic medical images. This system covers all diagnostic devices in the Neuroradiology Department. Moreover, it includes several graphic stations for viewing and postprocessing of medical images. The rooms equipped with digital diagnostic devices, and working and viewing graphic stations, have special connections to the network printers for image printing to film. Personal computers of scientific employees—engineers
Fig. 1.26 Schema of the computer radiological network for obtaining, storage, transmission and postprocessing of medical images in the Neuroradiology Department of Burdenko Institute of Neurosurgery
Neuroradiology: History and New Research Technologies
Fig. 1.27 Operating room with a navigational system for surgery
and researchers—located in the rooms of the Neuroradiology Department are connected to the network and equipped with the special software capable of working with DICOM images (Fig. 1.26). It is necessary to note that, for the past 10 years, the quantity amount of diagnostic examinations performed with use of digital methods has grown significantly, and image processing has become more complicated.
1.9
Navigation in Neurosurgery
Development of digital medical technologies, appearance of fast portable computers and successes in neuroradiology due to the advent of CTI and MRI paved the way for celebrated technological breakthroughs in stereotactic neurosurgery. This has led to development of modern navigating systems that enable surgeons to navigate quickly and precisely in the 3D space of a surgical incision during operation, with a 1- to 2-mm precision. Such systems allow surgeons to perform intervention with minimal injury to the surrounding tissues. Such systems use so-called frameless technology, unlike classical stereotaxis, which uses a frame-based navigating method. Navigation is based on “binding” of space coordinates to certain reference points that have static positions in geonavigating systems, e.g. stars or geodetic towers. Classical medical stereotactic devices use for these purposes a special frame fastened tightly to a patient’s skull before the operation. All further calculations are based on the mutual relation between intracranial structures and the reference points of a frame and its geometrical centre. Navigation of the surgical tool is made with the help of relatively large facilities such as various arches and guides fastened to a frame. Such technical decisions in classical stereotaxis limits the neurosurgeon’s actions in an incision and allows the carrying out of only simple manipulations (biopsy, implantation of electrode, catheter, cyst lancing).
25
The essence of frameless navigation is the following: Based on MRI and CT data, obtained before operation (as a rule, for 1–2 days), 3D images of the patient’s head are built with graphic station software. The surgeon, according to the 3D image, chooses accessible reference points (for example, a tip of a nose, teeth, curves of an auricle) on a surface of the patient’s head. Before the operation and after introduction of narcosis, the special small navigating frame [with a light-emitting diode (LED)], which, unlike classical stereotaxis, can be fixed practically any place on the head and in any way suitable for the given operation, is firmly fastened to the patient’s head at some distance from that area of interest. This frame, in the form of a partial arch, does not close the operational field and does not limit the surgeon in his or her actions. With the use of a special LED pointer, a preliminary “registration” is performed, i.e. the computer system “fuses” a 3D image of the patient’s head from its memory with real head position. All systems consist of the aerial receiver, LED pointer, reference arch and computer algorithm of work with the 3D image. This allows the neurosurgeon at any moment of operation to determine the position of his or her tool, with 1- to 2-mm precision, to plan an access trajectory, and to move toward the chosen target with the optimal and least invasive way (Fig. 1.27). Today, the optimal application for frameless navigation is the surgery of basal and small convex located tumours (Fig. 1.28) and for removal of foreign bodies from the skull cavity. Methods of combining CT, MRI and angiographic data into 3D models of the head (fusion algorithm) is especially advantageous in radiosurgery, allowing minimisation of pathological areas, with a 0.1-mm precision during the targeting of radiation to brain tissues (Fig. 1.29).
Fig. 1.28 Monitor of a workstation during preparation of removal of a brain tumour
26
Chapter 1
Fig. 1.29a,b Radiosurgical equipment. a Gamma knife device in the Burdenko Institute of Neurosurgery, b schema of target calculation (in
the planning stage) according to CT and MRI data
Refere n c e s 1. Alsop D, Detre J (1996) Reduced transit time sensitivity in noninvasive magnetic resonance imaging of human cerebral blood flow. J Cereb Blood Metab 16:1236–1249
14. Hourani R et al (2006) Proton magnetic resonance spectroscopic imaging to differentiate between non-neoplastic lesions and brain tumours in children. J Magn Reson Imaging 23:99–107
2. Aroutiunov A, Kornienko V (1971) Total cerebral angiography. Medicine Publishers, Moscow, p 167 (in Russian)
15. Karsmar G et al (1991) P-31 spectroscopy study of response of superficial human tumors to therapy. Radiology 179:149–153
3. Batchelor P et al (2006) Quantification of the shape of fibre tracts. Magn Reson Med 55:896–903
16. Knaap M van der et al (1990) Age-dependent changes in localised proton and phosphorus MR spectroscopy of the brain. Radiology 176:509–515
4. Bianchi M et al (2007) Treatment monitoring of brain creatine deficiency syndromes: a 1H- and 31P MR spectroscopy study. AJNR Am J Neuroradiol 28:548–554 5. Bluml S et al (2003) Membrane phospholipids and high-energy metabolites in childhood ataxia with CNS hypomyelination. Neurology 61:648–654 6. Braun K et al (1999) Cerebral metabolism in experimental hydrocephalus: an in vivo 1H and 31P magnetic resonance spectroscopy study. J Neurosurg 91:660668
17. Knaap M van der et al (1992) 1H and 31P magnetic resonance spectroscopy of the brain in degenerative cerebral disorders. Ann Neurol 31:202–211 18. Konovalov A, Kornienko V (1985) Computed tomography in neurosurgical clinic. Moscow Medicine Publishers, Moscow, p 290 (in Russian) 19. Konovalov A, Kornienko V, Ozerova V, Pronin I (2001) Neuroimaging in paediatrics. Antidor, Moscow. p 435 (in Russian)
7. Cha S (2006) Update on brain tumour imaging: from anatomy to physiology. AJNR Am J Neuroradiol 27:475–487
20. Konovalov A, Kornienko V, Pronin I (1997) Magnetic resonance imaging in neurosurgery. Vidar, Moscow, p 427 (in Russian)
8. Cha S et al (2007) Differentiation of glioblastoma multiforme and single brain metastasis by peak height and percentage of signal intensity recovery derived from dynamic susceptibilityweighted contrast-enhanced perfusion MR imaging. AJNR Am J Neuroradiol 28:1078–1084
21. Kornienko V, Pronin I, Fadeeva L et al (2000) Diffusion weighted imaging in study of brain tumours and peritumoural edema. J Vopr Neurochir 3:4–17 (in Russian)
9. Chai J-W et al (2007) Characterisation of focal brain lesions by gradient-echo arterial spine-tagging perfusion imaging. Neuroradiol J 20:149–158 10. Chepuri N, Yen Yi-Fen, Burdette J (2002) Diffusion anisotropy in the corpus callosum. AJNR Am J Neuroradiol 3:803–808 11. Feoktistov V (1938) The theory of tomography. Vestn Roentgenol Radiol 21:143–152 (in Russian) 12. Hesseltine S et al (2007) Application of diffusion tensor imaging and fibre tractography. Appl Radiol 1:8–23 13. Holshouser B et al (2006) Prospective longitudinal proton magnetic resonance spectroscopic imaging in adult traumatic brain injury. J Magn Reson Imaging 24:33–40
22. Kornienko V, Pronin I, Golanov A et al (2004) Neuroimaging of primary lymphomas of brain. J Med. Visualis 1:6–15 (in Russian) 23. Kornienko V, Pronin I, Pyanykh O et al (2007) Study of brain perfusion, using CT. J Med. Visualis 2:70–81. 24. Le Bihan D, Breton E (1985) Imagerie de diffusion invivo par resonance magnetique nucleaire. CR Acad Sc II Paris 301:1109–1112 25. Le Bihan D, Turner R (1991) Intravoxel incoherent motion imaging using spin echoes. Magn Reson Med 19:221–227 26. Le Bihan D, P van Zijl (2002) From the diffusion coefficient to the diffusion tensor. NMR Biomed 15:431–434 27. Lee S-K et al (2005) Diffusion-tensor MR imaging and fibre tractography: a new method of describing aberrant fibre connection in developmental CNS anomalies. Radiographics 25:53–68
Neuroradiology: History and New Research Technologies
27
28. Leemans A et al (2006) Multiscaled white matter fibre track coregistration: a feature-based approach to align diffusion tensor data. Magn Reson Med, 55:1414–1423
41. Rinck P (2003) Magnetic resonance in medicine. The basic textbook of the European Magnetic Resonance Forum. Blackwell, London, p 246
29. Maintz D et al (2002) Phosphorus-31 MR spectroscopy of normal adult human brain and brain tumours. NMR Biomed 15:18–27
42. Rodionov P, Serkov S, Fadeeva L (2002) Modern software in practice of functional diagnosis specialist. PC Mag 4:134–137 (in Russian)
30. Meng L (2004) MR spectroscopy of brain tumours. Magn Reson Imaging 15:291–313
43. Sen P-N, Basser P-J (2005) A model for diffusion in white matter in the brain. Biophys J 89:2927–2938
31. Mori S, van Zijl P (2002) Fibre tracking: principles and strategies. NMR Biomed 15:468–480
44. Serbinenko F (1974) Balloon catheterisation and occlusion of major cerebral vessels. J Neurosurgery 41:125–145
32. Moseley M, Butts K, Yenary M et al (1995) Clinical aspects of DWI. NMR Biomed 8:387–396
45. Sorensen A, Reimer P (2000) Cerebral perfusion imaging: principles and current applications. Thieme, Stuttgart, p 152
33. Mulkern R, Gudbjartsson H, Westin C еt al (1999) Multicomponent apparent diffusion coefficients in human brain. NMR Biomed 12:51–62
46. Stadlbauer A et al (2007) Changes in fibre integrity, diffusivity, and metabolism of the pyramidal tract adjacent to gliomas: a quantitative diffusion tensor fibre tracking and MR spectroscopic imaging study. AJNR Am J Neuroradiol 28:462–469
34. Nennig E et al (2007) Functional magnetic resonance imaging for cranial neuronavigation: methods for automated and standardised data processing and management. Neuroradiol J 20:159–158 35. O’Donnell L-J et al (2006) A method for clustering white matter fiber tracts. Neuroradiol J 27:1032–1036 36. Pierpaoli C, Jezzard P, Basser PJ et al (1996) Diffusion tensor MR imaging of the human brain. Radiology 201:637–648 37. Podoprigora A, Pronin I, Fadeeva L et al (2003) Proton MR spectroscopy in ischaemic brain disease. ZH Neurol Psikhiatr SS Korsakova 9(Suppl.):162 (in Russian) 38. Pouratian N, Sheth S, Bookheimer S et al (2003) Applications and limitations of perfusion-dependent functional brain mapping for neurosurgical guidance. Neurosurg Focus 15:1 39. Pronin I, Kornienko V, Podoprigora A et al (2002) Complex MR imaging of brain abscesses. J Vopr Neurochir 1:7–11 (in Russian) 40. Ramsey N, Hoogduin H, Jansma J (2002) Functional MRI experiments: acquisition, analysis, and interpretation of data. Eur Neuropsychopharmacol 12:517–526
47. Sunaert S (2006) Presurgical planning for tumour resectioning. J Magn Reson Imaging 23:887–905 48. Tanner J (1970) Use of stimulated echo in NMR diffusion studies. J Chem Phys 52:2523–2526 49. Ting-Yim L (2002) Functional CT: physiological models. Trends Biotechnol 20:1–8 50. Ulrich M et al (2007) 31P-1H echo planar spectroscopic imaging of human brain in vivo. Magn Reson Med 57:784–790 51. Ureniak J et al (1992) Specific expression of N-acetylaspartate in neurons, oligodendrocyte type-2 astrocyte progenitors, and immature oligodendrocytes in vitro. J Neurochem 59:55–61 52. Waaijer A et al (2007) Reproducibility of quantitative CNS brain perfusion measurements in patients with symptomatic unilateral carotid artery stenosis. AJNR Am J Neuroradiol 28:927–932 53. Zavoisky EK (1945) Spin-magnetic resonance in paramagnetics. J Phys Acad Sci USSR 9:211–245 (in Russian)
Chapter 2
2
Congenital Malformations of the Brain and Skull
in collaboration with V. Ozerova
2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9
Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . Organogenesis Impairment .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Impairment of Brain Diverticulation .. . . . . . . . . . . . . . . . . . . . . . . . . Impairment of Gyri and Sulci Formation .. . . . . . . . . . . . . . . . . . . . . Changes in Brain Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Destructive Brain Lesions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Histogenesis Impairment .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arachnoid Cysts .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Congenital Anterior Cranial Malformations . . . . . . . . . . . . . .. . . .
2.1
Introduction
29 29 41 46 53 53 60 69 80
Congenital brain malformations occur as a result of embryogenesis impairment and present as an anatomic defect or destructive brain lesion (Arendt 1968; Barkovich 2000; DeMyer 1971; Glenn and Barkovich 2006; Harwood-Nash et al. 1976; Polianker et al 1965; van der Knaap et al. 2006). It is very difficult to make a diagnosis of congenital brain malformation, based on clinical findings, and use of CT and MRI is essential in these cases. A child may have numerous brain malformations, frequently accompanied by congenital abnormalities of other organs and systems due to chromosomal balance impairment or noxious exposures during embryogenesis. Exogenous factors as well as hypoxia cause developmental defects of neural tissue, and focal and diffuse brain damage. CT and MRI allow distinguishing of changes that have occurred due to chromosomal abnormalities and due to noxious exogenous factors. There are several classifications of congenital brain malformations (DeMyer 1971; van der Knapp et al. 1988; Kornienko et al. 1993); however, there is a lack of united classification based on aetiology, pathogenesis and clinical findings at present. According to the Burdenko Institute of Neurosurgery of Russian Academy of Medical Sciences data, 22.6% children with hydrocephalus have brain malformations (nearly one in every fifth child), and 11.8% have numerous malformations.
2.2
Organogenesis Impairment
2.2.1 Impairment of Neural Tube Closure 2.2.1.1
Chiari Malformation Type I
Chiari malformation (Chiari type I) is caudal displacement of the cerebellar tonsils via the foramen magnum into the vertebral channel. In healthy children aged 5–15 years, the cerebellar tonsil are located a bit lower than in children aged 5 years and younger (and in adults). Hence, cerebellar tonsil displacement up to 5 mm below the foramen magnum in children aged 5–15 years should not be regarded abnormal (Altman et al. 1992; Barkovich 2000; Harwood-Nash et al. 1976; Kornienko et al. 1993). This malformation is more frequently isolated, but concomitants hydrocephalus and hydromyelia, craniocervical dysgenesia, platibasia, basilar impression, occipitalisation of the atlas and Klippel-Feil malformation are not infrequent in these patients (Barkovich 2000). Patients have the following clinical features: occipital headaches, cranial nerve palsies, and dissociated anaesthesia in limbs (due to hydromyelia). Precise diagnosis of Chiari type I malformation is possible only with MRI, which detects low positioning of cerebellar tonsils in relation to the foramen magnum (Fig. 2.1). Vertebral angiography reveals an indirect sign of this pathology: lowering of the caudal loop of the posterior inferior cerebellar artery into the vertebral channel, sometimes up to the С4 level. One should be more astute in suspicion of Chiari type I malformation if a patient has several of the above-listed signs. Such patients should undergo cervical spine MRI to exclude syringomyelia (present in 20–25% of cases).
2.2.1.2
Chiari Malformation Type II
Chiari malformation type II (Chiari type II) is a complex of malformations of the hindbrain, vertebral column and supratentorial structures. Almost all patients with Chiari type II have congenital myelomeningocele. According to
30
Chapter 2 Fig. 2.1a,b Chiari I malformation in a
5-year-old child. а MRI: the cerebellar tonsils are lowered down to С2, b Vertebral angiography: the caudal loop of the posterior inferior cerebellar artery is down to the vertebral canal below С2
Fig. 2.2a–f Chiari II malformation. Case 1: a 9-year-old child. CT (а,b) after a shunting operation. Transverse banding of cerebellar structures is visualised in the enlarged aperture of incisura tentorii; the tectum is elongated, and the massa intermedia is enlarged. Case 2: a 4-month-old child. MRI (с,d): The posterior surface pyramids of the os temporal is concave, cerebellar hemispheres extend anteriorly
and laterally to the pons, the fourth ventricle is small and the third and lateral ventricles are enlarged. There is breaking of the tectum on the image, the fourth ventricle is narrow and extends down into the foramen magnum and there is a cervicomedullary kink at the C2 level (e). PSIF (f): there is no CSF flow into the spinal canal
Congenital Malformations of the Brain and Skull
our data, Chiari type II is found in 0.1% of children with hydrocephalus. X-ray diagnosis of Chiari type II malformation is based on a group of different diagnostic procedures. Cranial X-ray reveals several manifestations of this malformation: holes on the most apical points of cranial vault bones, low placement of the inion, the more inferior attachment of tentorium cerebelli and very shallow posterior fossa, signs of hydrocephalus, enlargement of the foramen magnum, lumbar meningocele and spina bifida. Changes in the location of skull-base brain cisterns, ventricles and the aqueduct were detected before the CT era by ventriculography and myelography, using air or Xray-positive contrast media. These changes include changes in the location of tonsils and medulla in relation to the foramen magnum, elongations and/or ectopy of the fourth ventricle, Sylvian aqueduct narrowing or deformity, enlargement of the third and the lateral ventricles, and thickening of massa intermedia. Cerebral angiography is less informative. It only detects the extent of hydrocephalus, lower location of posterior inferior cerebral artery, and the confluens sinuum. CT and MRI can detail the intrusion of posterior fossa structures into the enlarged tentorium cerebelli foramen, displacement, deformity of the brainstem. Incorrect location of posterior fossa structures may be revealed on CT in children after a shunting operation for hydrocephalus, because enlarged ventricles mask impaired development of the tentorium cerebelli and pathological displacement of brain structures. After surgery due to regression of hydrocephalus, the enlarged foramen of the tentorium cerebelli is much better distinguished, as well as a beak-shaped tectum and lifted cerebellar vermis with transverse folds. The most complete picture of Chiari type II syndrome is obtained on МRI: enlargement of foramen magnum, and low placement of the tentorium cerebelli and brainstem. (The pons is usually narrowed in anteroposterior direction, and the medulla is elongated and sunk into the vertebral canal; Altman et al. 1992; Harwood-Nash et al. 1976; Kornienko et al. 1993; Naidich et al. 1983.) If the medulla is sunk below the dentate ligament, then the spinal cord is also lowered and forms a characteristic “knee” (Fig. 2.2). The fourth ventricle is narrowed, lowered and sometimes enlarged. The inferior and posterior elongated lamina tecti has a beak-like shape. In 80–90% of cases, dysgenesia of corpus callosum is revealed (hypoplasia or splenium agenesia, rostrum agenesia) along with extension of the massa intermedia.
2.2.1.3
Chiari Malformation Type III
Chiari Malformation type III is a very rare abnormality. The posterior fossa contains herniations (of the cerebellum and sometimes the brainstem) through a posterior spina bifida at the С1–С2 level (Barkovich 2000).
31
2.2.2 Cephaloceles (Craniocephalic Herniations) These abnormalities in impairment of neural tube closure present by way of developmental defect of the cranial bones and dura mater, with extracranial extension of brain structures (Delvert et al. 1982; Naidich et al. 1992; Polianker et al. 1965; Yokota et al. 1986). Based on the contents of a herniation, several types of craniocephalic herniations are distinguished: • Meningocele: isolated herniation of dura mater and CSF • Meningoencephalocele: herniation of dura mater, CSF and brain structures • Encephalon cystocele; meningoencephalocele contains a portion of the ventricular system • Atretic cephalocele: a tethered herniation containing dura mater, fibrous tissue and degeneratively changed brain structures • Gliocele: a glial cyst containing CSF Herniations are usually distinguished according to the location of the cranial bones through which they prolapse (Polianker et al. 1965; Naidich et al. 1992; Barkovich 2000): • Occipital • Of the cranial vault –– Interfrontal –– Of the anterior fonticulus –– Interparietal –– Of the posterior fonticulus –– Temporal • Frontobasilar –– Frontonasal –– Fronto-ethmoid (sincipital) –– Nasofrontal –– Naso-ethmoidal –– Naso-orbital • Basilar –– Trans-ethmoidal –– Spheno-ethmoidal –– Trans-sphenoidal –– Frontosphenoidal –– Spheno-orbital • Cranioschisis –– Cranial: superior facial fissure –– Basilar: inferior facial fissure –– Cervico-occipital fissure In occipital and cranial vault herniations, cranial bone junctions and fonticuli are the gates for herniation (Figs. 2.3, 2.4, 2.5). Frontobasilar herniations protrude through embryologically weak cranial regions. Frontonasal herniations protrude through the nasofrontal fonticulus, upper tip of nasal bones membrane, frontal bone and cartilage capsule (Fig. 2.6). Naso-ethmoid herniations protrude through the foramen cecum of the frontal bone (where the frontal and ethmoidal bones meet) into the nasal cavity (Fig. 2.7).
32
Chapter 2
Fig. 2.3a–c Occipital herniation. Case 1 (a): X-ray craniogram of an 8-day-old child. A finger-shaped defect in the squamous part of occipital bone confluent with the foramen magnum is seen along with
a soft tissue mass. Case 2 (b,c): 7-day-old child. The CT image shows a defect in the squamous part of occipital bone. Brain parenchyma, meninges and CSF cysts are present in the herniation
Fig. 2.4a–f Occipital herniation (meningoencephalocystocele) of an 18-day-old child. CT with 3D reconstruction: general appearance of head with occipital herniation (a). Axial FLAIR image MRI: defect in the squamous part of occipital bone, brain parenchyma with cystic cavities, and meninges are present the herniation (b). Sagittal Т2-weighted image (c) and fluid-attenuated inversion-recovery (FLAIR) image (d): posterior dislocation and traction of midbrain
and posterior fossa structures into a herniation, brainstem deformity with lowering downwards into foramen magnum, dilation of the interpeduncular cistern, ectopy of the fourth ventricle, and the third and the lateral ventricles are dilated with hydrocephalus. CTVG (e,f): contrast medium filling of the dilated third and the lateral ventricles, elongated Sylvian aqueduct, the fourth ventricle with ectopy
Congenital Malformations of the Brain and Skull
33
Fig. 2.5a–h Interparietal herniation (meningocele) in 5-month-old child. T1-weighted image (a–d), MR-venography (e,f) and CT with 3D reconstruction (g,h). There is a herniation of dura mater along with medially positioned bone defect in the posterior parietal region. The superior sagittal sinus is duplicated at the site of herniation
34
Chapter 2 Fig. 2.6a,b Frontonasal meningocele in a
3.5-year-old child. CT images (а,b)
Fig. 2.7a–c Naso-ethmoid herniation in an 8-month-old child. CT in sagittal and coronal planes (a,b) and CT with 3D reconstruction (c): internal surface of skull base
Fig. 2.8a–c Trans-ethmoid meningocele in a 1.5-year-old child. CT images (а–c)
Congenital Malformations of the Brain and Skull
35 Fig. 2.9a,b Trans-sphenoidal meningocele
in a 9-month-old child. a CT shows round defect in the body of the sphenoid bone. b Coronal CT shows soft-tissue herniation adjacent to the body of sphenoid bone, seen on a background of air in nasopharynx
Fig. 2.10a–c Leftward spheno-orbital herniation in a 2-month-old child. CT (а,b) and X-ray craniogram (c)
Naso-orbital herniations protrude through frontal, ethmoidal and lacrimal bones, and appear on the anterior and internal portions of orbits near the internal angle of the eye fissure. Basilar herniations protrude through the ethmoid or sphenoid bones. Trans-ethmoidal herniations perforate sieve-like lamina and prolapse into the anterior portion of the nasal cavity (Fig. 2.8). Spheno-ethmoidal herniations penetrate via the junction of the ethmoid and sphenoid bones and appear in the posterior portion of nasal cavity and nasopharynx. In trans-sphenoidal herniations, the cranial defect is located at the bottom of sella turcica or within the body of sphenoid bone. Herniation masses may be preserved in the sphenoid sinus or protrude into the nasopharynx (Fig. 2.9). Spheno-orbital herniations (of posterior orbital location) may have different gates. Herniation masses may protrude through the superior orbital (sphenoidal) fissure, optic nerve channel, or congenital abnormal fissure of the sphenoid bone, or through the sphenoid and frontal bones. Herniation mass-
es located near the apical part of the orbit cause unilateral exophthalmus (Figs. 2.10, 2.11). If CT or MRI are not available, then X-ray or linear cranial tomography may be used to detect herniation gates. However, 3D MRI or CT reconstruction allow detection of internal as well as external rings of herniation and intracerebral relationships of tissues including the arteriovenous system. Additionally performed CT or MR ventriculography aids in ascertaining how the contents of herniation communicate with the CSF space.
2.2.3 Agenesia of the Corpus Callosum Formation of corpus callosum, septum pellucidum and fornix begins at the 11th and terminates at the 16th week of intrauterine life, and so the extent of corpus callosum defects depends on the stage of fetal development at which corpus callosum development terminates. Primary agenesia occurs in the 12th week of fetal life as a consequence of vascular or inflammatory damage of commissural lamina and may be isolated
36
Chapter 2
Fig. 2.11a–c Leftward spheno-orbital herniation (meningocele) in a 14-month-old child. CT (а,b) and МRI (c)
or concomitant with other malformations, such as agenesia of septum pellucidum or holoprocencephaly. Secondary dysgenesia—complete or partial destruction of corpus callosum—is a result of encephalomalacia and occurs after completion of corpus callosum development in traumatic and toxic lesions, and anoxia in the anterior cerebral artery territory. Agenesia of corpus callosum prevalence, according to our data, is encountered in 2.9% of children with hydrocephalus, but only in 0.8% of them is it “pure”, and in the rest of cases, other brain malformations accompany it. Agenesia of corpus callosum has no characteristic clinical picture, and neurological signs are frequently caused by concomitant cerebral diseases (Arendt 1968; Castillo et al. 2000; Harwood-Nash et al. 1976; Kornienko et al. 1993). There are no X-ray craniography signs of this pathology. If
it coincides with other developmental abnormalities of brain and skull, then signs of the latter may predominate. CT semiotics of agenesia of corpus callosum presents as follows: widely expanded anterior horns of the lateral ventricles, and upward position of the third ventricle between them, medial walls of the lateral ventricles become oriented in parallel to each other, and the posterior horns are usually dilated (Fig. 2.12). MRI performed in three planes gives the most complete information about the extent of corpus callosum developmental defects: partial (hypogenesia), complete (agenesia), or partial developmental defect (dysgenesia) (Figs. 2.13, 2.14). Median sagittal slices are the most informative, as they allow distinguishing of the formation of all regions of corpus callosum— rostrum, genu, body, and splenium. Agenesia (hypogenesia)
Fig. 2.12a–c Agenesia of corpus callosum in a 1-year-old child. CT (а–c) images: the third ventricle is located upwards, between the sepa-
rated and moderately dilated lateral ventricles, and corpus callosum is not visualised
Congenital Malformations of the Brain and Skull
37
Fig. 2.13a–d Agenesia of the corpus callosum in a 1-year-old child. Т1- and Т2-weighted images in three planes (а–d). The corpus callosum is not visualised, and the lateral ventricles are asymmetrical and widely separated
Fig. 2.14a–c Marked hypogenesia of corpus callosum in a 3.5-year-old child. MRI in three planes (а–c): a part of genu of corpus callosum is
seen, the lateral ventricles are separated and their posterior portions are dilated
38
Chapter 2
Fig. 2.15a–c Lipoma of the genu of corpus callosum in a 4-year-old child. CT (а–c): round hypodense mass (–110 HU) with peripheral
calcinations Fig. 2.16a,b Pericallosal lipoma in a
6-year-old child. T1-weighted image in sagittal (а) and coronal (b) planes: a nutshelllike lipoma with a typical hyperintense signal is located above the body of corpus callosum, clear-cutting its splenium
Fig. 2.17a,b Pericallosal lipoma in a 6-year-old child. Т1-weighted image in sagittal (а) and T2-weighted image in axial (b) planes. At the site of hypogenesia of corpus callosum, there is a horseshoe-like mass with hyperintense signal typical for lipoma
Congenital Malformations of the Brain and Skull
39
Fig. 2.18a–b Lipoma of the quadrigeminal cistern. T1-weighted image in three planes (а–c): irregular-shaped mass with hyperintense signal located between the lamina tecti and the upper portion of the vermis
of the corpus callosum frequently accompanies the absence or hypoplasia of hippocampus, amygdala, heterotopia of grey matter or other brain malformations (Castillo et al. 2000; Glenn and Barkovich 2006). Lipoma of the corpus callosum always accompanies hypo, dys- or agenesia of the corpus callosum, although it is an intrahemispheric formation located near corpus callosum. X-ray craniograms may be useful in cases of giant interhemispheric lipomas with peripheral petrificates. On CT, lipoma is detected as a clear-cut hypodense lesion. Lipoma has even and clear borders, is calcinated in some places, and its CT density is significantly lower than that of CSF [–80 to -110 Hounsfield units (HU)] (Fig. 2.15). On MRI, lipoma appears as a structure of different shape and size, markedly hyperintense on Т1-weighted images. It may be located in any part of corpus callosum—above or below, or near the splenium, body or genu (Figs. 2.16–2.18). Giant lipomas are characterised by chemical shift artefacts due to differences in magnetisation characteristics of water protons and fat tissue.
2.2.4 Dandy-Walker Malformation This malformation is a cystic dilatation of the fourth ventricle, combined with agenesia of cerebellar vermis, upward location of tentorium cerebelli and hydrocephalus (Altman et al. 1992; Fitz 1983; Harwood-Nash et al. 1976; Irger 1981).
2.2.4.1
Dandy-Walker Malformation Type I
Dandy-Walker malformation type I (a true Dandy-Walker cyst) is a cystic dilatation of the fourth ventricle, with absence of Magendie and Luschka foramens, partial or complete agenesia of cerebellar vermis and upward location of tentorium cerebelli and hydrocephalus. Connection between the fourth ventricle and perimedullary space is absent. This malforma-
tion results from the abnormality of rhombencephalic vesicle cover and adjacent meningeal structures, which develop between the 7th and the 10th weeks of embryonic life. From the embryological point of view, the fourth ventricle cyst in true Dandy-Walker malformation is locked or half-locked. External foramina of the fourth ventricle are usually absent, but one of them may be preserved, as well as the connection with the third ventricle.
2.2.4.2
Dandy-Walker Malformation Type II
Dandy-Walker malformation type II is a partial agenesia of cerebellar vermis due to posterior dilatation of the tela chorioidea backwards and above the vermal rudiment. The connection between the fourth ventricle, perimedullary and subarachnoid space is retained. According to McLaurin (in 1985), in 65% of cases, DandyWalker malformation may be combined with other developmental CNS abnormalities: polymicrogyria, cerebral and cerebellar hemispheres heterotopia, incorrect brainstem position as well as developmental abnormalities in other organs and systems (polydactyly, syndactyly, congenital cardiac defects, cleft palate, and so forth). To our knowledge, classic Dandy-Walker cysts are found in 6.4% of children with occlusion hydrocephalus. Clinical signs of this malformation are presented in general with signs of hypertensive hydrocephalus and symptoms of posterior fossa involvement: gait and static disturbances, nystagmus and others. Progressive course of hydrocephalus is usually observed at birth or soon thereafter. Craniographic features are scanty. Predominantly, they are the signs of hypertensive hydrocephalus. Enlargement of posterior fossa is revealed by upward location of the transverse sinus. Sometimes posterior protrusion of occipital bone within the lambdoid suture is found, which is easily palpated during examination of a child.
40
Chapter 2
Fig. 2.19a–c Dandy-Walker malformation in a 4-month-old child. CT (а–c): the fourth ventricle is widely connected with a CSF cyst that almost totally occupies the enlarged posterior fossa, the vermis of cerebellum is absent, cerebellar hemispheres are hypoplastic, and the third and the lateral ventricles are markedly dilated
Fig. 2.20a–c Dandy-Walker malformation in a 3-month-old child. MRI (а–c) brainstem, vermis and cerebellar hemispheres hypoplasia. A
CSF cyst occupies the enlarged posterior fossa, the tentorium cerebelli is located upwards, and the third and the lateral ventricles are markedly dilated
CT and MRI reveal a characteristic picture: cystic dilatation of the fourth ventricle, which fills all the posterior fossa; the vermis is not seen or has marked hypoplasia; the cerebellar hemispheres have slid apart and decreased in volume, tentorium cerebelli is located upwards, and the third and lateral ventricles are hydrocephalically dilated (Figs. 2.19, 2.20). Communication of the subarachnoid space with the cystic dilated fourth ventricle may be detected by CT cisternography. In the absence of connection, contrast medium fills posterior fossa cisterns and chiasmal cisterns, but not the fourth ventricle. To detect connection between the fourth and the third ventricles, CT ventriculography is indicated. It may reveal intrusion of some contrast medium into the cystic dilata-
tion of the fourth ventricle (Fig. 2.21). MRI PSIF [a reversed form of fast imaging with steady state precession (FISP)] may also detect the CSF flow into the fourth and the third ventricles and further into cisterna magna, if the signal of CSF flow is absent.
2.2.5 Variant of Dandy-Walker Syndrome This malformation—according to our data—presents in 3.5% of cases among all children with hydrocephalus and 6.2% of children with open hydrocephalus. Clinical features of hydrocephalus are usually the manifesting signs. CT and MRI
Congenital Malformations of the Brain and Skull
41
Fig. 2.21a–c Dandy-Walker malformation in an 18-month-old child. а CT, b,c CTVG. A contrast medium introduced into the lateral ven-
tricle filled both lateral and the third ventricles, partially reaching the cyst-like dilated fourth ventricle (its density was increased to compare with native CT scans)
Fig. 2.22a–c Variety of Dandy-Walker malformation in an 8-monthold child. Т2-weighted image (а) and Т1-weighted image (b): hypoplasia of vermis, cerebellar hemispheres and brainstem; the fourth ventricle is widely connected with the CSF cyst in posterior fossa.
PSIF (c): the effect of flow void from excessive CSF movement in the Sylvian aqueduct, within the enlarged cisterna magna and craniovertebral junction
reveal wide communication between the fourth ventricle and cisterna magna. The cistern magna is enlarged in size; vermis and cerebellar hemispheres are hypoplastic to various extents (Fig. 2.22). The lateral and the third ventricles are hydrocephalic, and the extent of their dilation varies from mild to severe with periventricular oedema. To judge whether a connection between this CSF cyst and the ventricular system exists, and to distinguish it from a retrocerebellar arachnoid cyst, CT ventriculography, CT cisternography or MRI PSIF are indicated. This detects communication between the ventricular system and subarachnoid space of the spinal cord (Fig. 2.23).
2.3
Impairment of Brain Diverticulation
2.3.1 Holoprosencephaly The term holoprosencephaly was coined by W. Demyer and W. Zeman in 1960 to define a group of malformations in which the prosencephalon tends to remain as a whole, combined with facial malformations. Holoprosencephaly is a defect of separation of the primary brain vesicle, not completely transformed to di- and telencephalon by the fifth week of embryonic life. The etiological factors of holoprosencephaly are radiation exposure in the first half of pregnancy and chromosomal abnormalities (trisomies of chromosomes 16
42
Fig. 2.23a–f Variety of Dandy-Walker malformation and progressive
Chapter 2
open internal hydrocephalus in a 2-year-old child. CТ (а–c), CTVG (d–f): 10 min after CM injection into the right lateral ventricle, all
portions of ventricular system were enhanced to identical extents, as well as the CSF cyst in posterior fossa. Contrast failed to reach the area of periventricular oedema
and 18, Down’s syndrome, and so forth). This malformation is frequently combined with developmental defects of medial facial bones, and absence of olfactory bulbs, corpus callosum and falx cerebri. Holoprosencephaly may be alobar, semilobar or lobar (Fitz 1983; Harwood-Nash et al. 1976; Manelfe and Sevely 1982; Polianker et al. 1965; Smirniotopoulos et al. 1992) Alobar and semilobar are the most severe forms. According to our data, holoprosencephaly presents in 0.9% of cases among children with hydrocephalus. Clinical signs of hydrocephalus depend on the extent of brain damage. The alobar form has poor prognosis and cannot be treated surgically or pharmacologically. The brain is markedly reduced in size and contains a single large cavity with a dorsal sack instead of the third and the lateral ventricles, thalami are
united, and olfactory bulbs and tracts, corpus callosum and falx cerebri are absent (Fig. 2.24). Facial malformations are the obligatory component. They may appear as cyclopia, etmo- or cebocephalia and/or median or paired cleft palate. In all these facial malformations, hypo- or aplasia of medial facial bones (nasal bones, vomer) and skull (crista galli, sphenoid bone) are present. In semilobar holoprosencephaly, the brain is also small, with rudiments of occipital lobes, sole ventricular cavity and maldeveloped falx cerebri. Interhemispheric fissures are present in the anterior or posterior portions, the corpus callosum may be completely or partially absent, the thalami and basal ganglia are united, and olfactory bulbs and tracts are usually absent. Facial malformations are infrequent. Usually, they ap-
Congenital Malformations of the Brain and Skull
43
Fig. 2.24a–c Alobar holoprosencephaly. CT [according to Manelfe and Sevely (1992)]: а Posterior fossa structures are not changed. b,c The supratentorial space is occupied by the giant cavity, represented by a single ventricle and a dorsal sack. Basal ganglia and thalami are confluent, and the interhemispheric fissure is absent
Fig. 2.25a–c Semilobar holoprosencephaly in a 7-year-old child. CТ: the third and the lateral ventricles form a single cavity; large falx cerebri is visualised only in the anterior and posterior portions of the interhemispheric fissure
pear as cleft palate and orbital hypotelorism; true hypertelorism is rarely seen. CT and MRI reveal the sole cavity (but it is smaller than in the alobar form) and part of the falx cerebri (Figs. 2.25, 2.26). As corpus callosum is completely or partially absent, the dorsal sack rises upwards and forms the interhemispheric cyst. This cyst was termed diencephalic by G. Brocklechurst in 1973; later in 1979, F. Probst called it a primary interhemispheric cyst, distinguishing it from the secondary interhemispheric cyst found in agenesia of the corpus callosum, in which falx cerebri produces invagination in the third ventricle cover. The interhemispheric cyst may pass beyond the cranial vault borders, forming a herniation. To confirm a diencephalic cyst, CT ventriculography is indicated (Fig. 2.27).
The mildest form of holoprosencephaly is lobar. According to our data, lobar holoprosencephaly is found in children with open hydrocephalus, the signs of which were detected on X-ray craniograms. On CT, brain hemispheres are separated except for the anterior portions, the lateral ventricles are united, the septum pellucidum is absent, the inferior and posterior horns are well presented and the corpus callosum is absent (Fig. 2.28). Lobar holoprosencephaly is hard to distinguish from congenital agenesia of septum pellucidum or its rupture in severe hydrocephalus. The Y-shaped appearance of the third ventricle and marked flattening of the cover of anterior horns of the lateral ventricles are distinguishing features of holoprosencephaly.
44
Chapter 2
Fig. 2.26a–h Semilobar holoprosencephaly in a 4-year-old child. a,b CТ series of slices. c–h МRI in three planes: in the anterior and medial portions, hemispheres are not separated; the longitudinal fissure is visible only in the posterior portion. Only the splenium of corpus callosum is present
Congenital Malformations of the Brain and Skull
Fig. 2.27a–f Semilobar holoprosencephaly in an 11-month-old child. CТ (а,b) and МRI (c): a single ventricular cavity is located medially; the dorsal sack goes upward into the interhemispheric fissure, form-
45
ing a cyst, and then goes beyond the borders of skull via a bony defect having a herniation appearance. CTVG (d–f): CM infused into a herniation sack reached the ventricular system via the dorsal sack
46
Chapter 2
Fig. 2.28a,b Lobar holoprosencephaly in a 5-year-old child. CТ images (a,b): posterior fossa structures are not changed. The ventricular cavity is divided into the third and the lateral ventricles, septum pel-
lucidum is absent, there is hypoplasia of corpus callosum (only its posterior portion is seen) and the posterior third of the interhemispheric fissure is not visible
2.3.2 Septo-Optic Dysplasia
and, therefore, are more marked in children with complete lissencephaly. Microcephaly and muscle hypotonia are typical for complete lissencephaly. Infantile spasms are frequent. Refractory epilepsy develops in the early age. The majority of patients have regions of agyria and pachygyria—the former are frequently found in parieto-occipital regions, the latter in frontal and temporal regions. CT and MRI reveal these changes: the brain surface is weakly striated, has a smoothened picture of grey and white matter, and vertically oriented Sylvian fissures, which gives the whole brain a figure-8 appearance. The thin external layer of cortex is separated from the thicker deep cortical layer by a zone of white mater (the “zone of disseminated cells”), which seems normally myelinated. It is suggested that the internal layer is represented by young neurons, the migration of which was delayed. This appearance resembles a brain in the 23rd to 24th weeks of development, when sulci start to form (Barkovich 2000). Cases of severe agyria may be combined with hypogenesia of corpus callosum, dilatation of posterior horns of the lateral ventricles and brainstem hypoplasia (Figs. 2.31, 2.32). Pachygyria regions are also represented by thickened cortex, but wide sulci and small gyri are present. In focal pachygyria, the changes may be detected in any area of the brain, and in diffuse pachygyria, which is frequently combined with agyria. Predominating changes are found in the parieto-occipital regions.
Septo-optic dysplasia is a hypoplasia of optic nerves, combined with hypoplasia or absence of the septum pellucidum. It is thought that septo-optic dysplasia is a result of different genetic abnormalities and intrauterine ischaemic events during the first two trimesters of pregnancy. Clinical features of this syndrome are variable and depend on the degree of vision impairment and presence of pituitary–hypothalamic dysfunction, which are seen in two thirds of cases. Diagnosis is confirmed by optic discs hypoplasia, absence of the septum pellucidum and optic nerves atrophy detection on CT and MRI (Fig. 2.29).
2.4
Impairment of Gyri and Sulci Formation
2.4.1 Lissencephaly Lissencephaly (from the Greek words liss and enkephal, meaning literally “smooth brain”) is related to impaired development of gyri and sulci (Byrd 1988, 1989). Agyria is absence of gyri on the brain surface; it is synonymous with complete lissencephaly, whereas pachygyria means presence of wide and flat gyri and is synonymous with incomplete lissencephaly (Barkovich 2000; Byrd et al. 1988, 1989) (Fig. 2.30). Clinical features depend on the extent of retarded brain development
Congenital Malformations of the Brain and Skull
Fig. 2.29a–e Septo-optic dysplasia, dysgenesia of corpus callosum and interhemispheric arachnoid cyst in the left occipital region in a 2-year-old child with blindness and epilepsy. MRI in two planes (а–c) and study of optic nerves in a T2 fat-saturated sequence (d,e).
47
The cystic cavity is seen in the left occipital region, the septum pellucidum is absent, there is dysplastic corpus callosum and excessive accumulation of CSF in the chiasmatic region, and chiasma and optic nerves are thinned
Fig. 2.30a,b Lissencephaly in a 2-year-old
child with psychomotor impairment and infantile spasms. МRI, Т1-weighted (а) and Т2-weighted (b) images: wide and flat gyri and small sulci in frontal and temporal regions, almost complete absence of gyri and sulci in posterior parieto-occipital regions of cerebral hemispheres, cerebral white matter is underdeveloped and the lateral ventricles are dilated
48
Chapter 2
Fig. 2.31a–f Lissencephaly in a 2-year-old child. MRI in axial (а–c) and sagittal (d) planes and in 3D reconstruction (e,f): weakly outlined sulci and gyri in all brain regions, weak differentiation of white and grey matter, and CSF spaces are dilated
Fig. 2.32a–c Agyria and agenesia of corpus callosum in a 4-month-old child. MRI: Т2-weighted images in three planes. Gyri and sulci are
hardly outlined, the cortex is wide, white matter is underdeveloped, the corpus callosum is not differentiated, the lateral ventricles are separated and the Sylvian fissures are widened
Congenital Malformations of the Brain and Skull
49
2.4.2 Schizencephaly Schizencephaly (agenetic porencephaly) is a congenital (unior bilateral) cleft that usually passes along the primary brain fissures (lateral, central) up to the lateral ventricle. Yakovlev and Wadsworth (1946) distinguished schizencephaly with detached (open) and closed (stuck) borders. In type I, the borders of fissure are slid widely apart, and the space between them is filled with CSF. In type II, the borders of fissure are locked, tightly adjacent to each other, separated only by deep and narrow sulcus and lined with ependyma and arachnoid membrane. Destruction of cortex in schizencephaly is accompanied by heterotopia of grey matter on the fissure borders. Diagnosis of schizencephaly with open borders by CT and MRI is simple: fissures in brain parenchyma of various sizes are revealed, which go towards the external wall of the lateral ventricle and join it (Fig. 2.33). CSF in fissures possesses the same features on MRI and CT as does ventricular CSF. Schizencephaly with closed borders is difficult to detect by CT, whereas MRI gives a complete picture about connections between fissures and the lateral ventricle and the structure of its walls (Fig. 2.34). Some-
Fig. 2.33 Schizencephaly with opened borders in a 4.5-year-old
child. CT: the fissure borders are separated and filled with CSF
Fig. 2.34a–f Schizencephaly with closed (locked) borders in a 2-year-old child. CT (а,b) and МRI (c–f): narrow fissure in parietal region leftwards goes up to the lateral ventricle; its borders are covered by grey matter
50
times, a papillary with a porencephalic channel may be found on the internal side of the lateral ventricle.
2.4.3 Heterotopy
Chapter 2
There is no area of perifocal oedema in heterotopy, in contrast to brain tumours (Fig. 2.35). Subependymal nodules have smooth surfaces and narrow the lumen of lateral ventricles (Fig. 2.36). Subcortical nodules sometimes contain vessels or CSF resembling a tumour. Diffuse (ribbon-like) heterotopy looks like striae of grey matter located deeply and separated from cortex by a layer of white matter (Fig. 2.37). Sometimes several types are combined, i.e. mixed heterotopy (Fig. 2.38).
Heterotopy is a cluster of grey matter cells in atypical places, due to retardation of radial neuronal migration (Barkovich et al. 1992; Byrd et al. 1989). Grey matter heterotopy may be combined with other structural abnormalities. Almost all patients with grey matter heterotopy have epilepsy and may have motor or mental deficits. Subependymal, focal (nodular) and diffuse (ribbon-like) heterotopy are distinguished. MRI is more sensitive than CT is in diagnosis of this abnormality. Heterotopy appears as nodules or wider areas isodense and isointense in grey matter without contrast enhancement in the subependymal, periventricular spaces or subcortically.
Polymicrogyria (cortical dysplasia) is a migration abnormality in which neurons reach the cortex, but formation of the latter is impaired, and this causes the development of many small gyri. Most or least part of the hemisphere is affected. The Sylvian fissure is a predominant area of location; how-
Fig. 2.35a–f Nodular heterotopy of grey matter in a 12-year-old child with focal epilepsy. CT (а,b): focal accumulation of grey matter in the right parietal lobe, appearing as a clear-cut nodule on a border
of the sulcus. Т2- and Т1-weighted images (c–f): the signal of foci is isointense to those of grey matter CSF in the right parietal lobe. The lateral ventricles are of usual size
2.4.4 Polymicrogyria (Cortical Dysplasia)
Congenital Malformations of the Brain and Skull
Fig. 2.36a–c Subependymal heterotopy of grey matter. Case 1. CT
(a): external walls of the lateral ventricles are scalloped, they are isodense with cerebral grey matter and the ventricular lumen is un-
51
evenly narrowed. Case 2, MRI (b,c): a 12-year-old child with multiple subependymal nodular masses of grey matter lining lateral ventricles
Fig. 2.37a–c Ribbon-like heterotopy (double cortex) in a 2-year-old child with epilepsy. Т1- and Т2-weighted images: the second grey matter layer is located between cortex and main part of white matter, which duplicates the shape of gyri, being separated from cortex by a thin striae of white matter
52
Chapter 2
Fig. 2.38a–f Mixed diffuse-nodular and subendymal heterotopy of grey matter in a 7-year-old child with epilepsy. Т2-weighted images (а,b), proton-density images (c,d), and Т1-weighted images (e,f). Extensive area of signal change in the right temporo-occipito-pari-
etal region isointense with grey matter is seen. The adjacent portion of the lateral ventricle is narrowed, and there are subependymal nodules on its external wall
Fig. 2.39a–c Polymicrogyria in a 6-month-old child with epilepsy, mental retardation and motor deficits. CТ (а–c): uneven and incorrectly formed brain surface with many small gyri, the anterior por-
tion of the interhemispheric fissure and the lateral cerebral fissures are markedly increased in size, the latter are located vertically and the third and the lateral ventricles are dilated
Congenital Malformations of the Brain and Skull
ever, frontal lobes may be affected, sometimes bilaterally (Fig. 2.39). Severity of clinical symptoms (epilepsy, failure to thrive and motor deficits) depend upon the length of lesion. CT and MRI appearance of cortical dysplasia vary: uneven, incorrectly formed surface or, vice versa, exceptionally smooth due to adhesion of the external cortical (molecular) layer on micro-fissures. It may appear as pachygyria with uneven wide gyri or normal. The polymicrogyria cortex is isodense on CT and isointense on MRI in comparison with normal cortex; however, sometimes part of it may be calcinated.
2.4.5 Rhombencephalosynapsis Rhombencephalosynapsis (RS) is the absence of separation of the cerebellum in the vermis and hemispheres. It is a rare malformation, and the diagnosis cannot be made without MRI. The incidence of RS is 0.13% (Barkovich 2000; Toelle et al. 2002; van der Knapp et al. 1988). The age of incidence varies greatly—from fetuses to 39-year-olds. The aetiology is unknown, as there are no specific symptoms of this malformation. Rhombencephalosynapsis is frequently combined with other brain malformations: Chiari type II, corpus callosum dysgenesia (up to agenesia), developmental defects of gyri and sulci, hydrocephalus and absence of septum pellucidum. Other abnormalities can include cardiovascular, renal and limb (hypoplasia of phalanxes, syndactyly) (van der Knapp et al. 1988). MRI in T1- and T2-weighted sequences reveals the absence of demarcation between hemispheres and the vermis, and the downward location of tentorium cerebelli (Figs. 2.40, 2.41).
2.4.6 Lhermitte-Duclos Disease (Dysplastic Cerebellar Gangliocytoma) Lhermitte-Duclos disease (dysplastic cerebellar gangliocytoma) is characterised by a separated area of cerebellar cortex enlargement, which sometimes extends into the vermis and contralateral hemisphere. Microscopy reveals thickening of abnormal ganglionic cells in the granular cortical layer, thickening of excessively myelinated marginal layer and thinned layer of Purkinje cells. Clinically, this pathology may manifest itself with cerebellar signs in any age, or may be asymptomatic and revealed only in autopsy. On CT, an area of moderate volume enlargement with deformity of adjacent tissues is seen without changes in density. On MRI, a clear-cut area of changed signal intensity on T1- and T2-weighted images is seen, which cause fourth ventricle deformity. Some contrast enhancement may be seen in the pathological area on CT and MRI (Fig. 2.42).
53
2.5
Changes in Brain Size
2.5.1 Unilateral Megalencephaly Unilateral megalencephaly is a hamartoma-like—local or total enlargement of a cerebral hemisphere with defects of neuronal migration. Clinically, it presents with refractory epilepsy, hemiplegia and failure of development mental and physical. On CT and MRI, enlargement of a part or the whole hemisphere is seen, cortex is dysplastic and thickened, with uneven gyri and small fissures, and some gyri may be normal or smooth. The lateral ventricle is dilated on the affected side; its anterior horn is elongated and straightened. Sometimes the corresponding part of brain (or hemisphere) has a peculiar hamartoma-like appearance (Figs. 2.43, 2.44).
2.5.2 Microcephaly The term microcephaly is related to different sporadic and genetic disorders. In children, head circumference lags behind the age-adjusted normal value, and marked failure to thrive is seen without focal neurological signs. The brain usually has a thin cortex and smoothened sulci. On X-ray craniogram, the skull is small in size, cranial vault bones are thickened, no fingerprint seen and cranial sutures are closed and thickened. CT and MRI usually reveal small brain with smoothened gyri and sulci (Fig. 2.45).
2.6
Destructive Brain Lesions
2.6.1 Porencephaly Porencephaly is a CSF-filled cavity within the brain tissue (Barkovich 2000; Harwood-Nash et al. 1976; Kornienko et al. 1993). Aetiological factors of porencephaly are anoxia, massive haemorrhage and traumatic or inflammatory process to which developing brain was exposed in the intrauterine or early postnatal period. In closed porencephaly, the cavity is connected neither with ventricles nor with subarachnoid space. Yakovlev and Wadsworth (1946) distinguished agenetic porencephaly, developed before 6 months of intrauterine life, and encephaloclastic porencephaly, formed within the last trimester of pregnancy or after birth. Histology of the internal walls is a distinguishing feature of these variants. Agenetic porencephaly is infrequently accompanied by agenesia of the corpus callosum. According to our data, porencephaly is seen in 4.5% of cases in children with hydrocephalus. Porencephaly is caused by other developmental brain abnormalities in almost half of the cases. The clinical picture depends on location and size of the cavity.
54
Fig. 2.40a–c Rhombencephalosynapsis in a 1.5-month-old child
with Chiari II malformation, obstructive hydrocephalus and lumbosacral meningomyeloradiculocele. MRI in sagittal and coronal planes (а,b): downward location of tentorium cerebelli, the pons is
Fig. 2.41a–c Multiple malformations in a 5-year-old child: Chiari II, rhombencephalosynapsis, dysgenesia of corpus callosum and cortical dysgenesia. MRI Т1- and Т2-weighted images: the cerebellum is not divided into vermis and hemispheres, medulla and cerebellar tonsils are sunk into foramen magnum, the fourth ventricle is not
Chapter 2
situated at the level of low margin of clivus and the cerebellum is not divided into vermis and hemispheres. MRI (c) of lumbosacral spine reveals the meningomyeloradiculocele
differentiated, tectum is elongated and beak-shaped, corpus callosum is underdeveloped (only splenium and a part of body are differentiated), the lateral ventricles are separated and asymmetrical, and the gyri of medial surfaces of cerebral hemispheres has a peculiar appearance (elongation–stenogyria)
Congenital Malformations of the Brain and Skull
Fig. 2.42a–f Lhermitte-Duclos syndrome in a 1-year-old child. CT
(a) reveals a mildly hyperdense area in the right cerebellar hemisphere, and (b) after contrast medium enhancement accumulated to a mild extent in the pathological area. The Т2-weighted image (c)
Fig. 2.43a–c Leftward megalencephaly in a 12-month-old child with
severe psychomotor retardation, epilepsy, severe rightward hemiparesis. CT (а–c): the left cerebral hemisphere is enlarged, sulci and gyri are smoothened and the left lateral ventricle is greater than the
55
reveals an area of unevenly increased signal intensity in the right cerebellar hemisphere and vermis. The fourth ventricle is deformed. MRI with contrast enhancement (d–f): slight hyperintensity in the pathological area is seen
right one—its anterior horn is elongated in the anterior direction. A markedly hypodense focus in the interhemispheric fissure (–25 HU) indicates possible lipoma
56
Fig. 2.44a–f Rightward megalencephaly in a 9-month-old child with epilepsy and severe leftward hemiparesis. CT (а,b), Т1-weighted images (c,d), and Т2-weighted images (e,f): enlargement of the right hemi-
Chapter 2
sphere is seen, the right lateral ventricle is greater than the left one, its anterior horn is narrowed and elongated in the anterior direction, and gyri and sulci in the parietal and occipital regions are smoothened
Fig. 2.45a–c Microcephaly in a 18-month-old child with psychomotor retardation (skull circumference is 42 cm). MRI (а–c): the skull is small, signal from brain parenchyma is unchanged, there is dysplasia of corpus callosum and ventricular system is not dilated
Congenital Malformations of the Brain and Skull
Porencephaly has no typical picture on X-ray craniogram. Signs of hydrocephalus may be seen, and rarely, thinning and protrusion of cranial vault bones on the affected side. On CT, a hypodense (CSF isodense) area is seen, with clear-cut borders and connection with the lateral ventricle and/or subarachnoid space (Fig. 2.46). Intravenous contrast enhancement does not increase density of the cavity walls, which allows differentiation from cystic brain tumours and abscesses. CT ventriculography reveals simultaneous filling of ventricular system and the porencephalic cyst, with contrast medium. On MRI, the porencephalic cavity appears as a clearly delineated area of changed signal, isointense with CSF in all sequences (Fig. 2.47). It is easy to define the quality of these cavities margins (grey or white matter), which allows estimation of the time when the cavity was formed.
57
Porencephaly is always defined as a developmental defect of amiculum cerebri. Raybaud (1983) distinguished porencephaly of posterior fossa as a histogenetic defect of the cerebellum, infrequently combined with defects of supratentorial structures. CT and MRI reveal wide CSF cavity connected with the fourth ventricle (Fig. 2.48).
2.6.2 Hydranencephaly Hydranencephaly is an anencephalic hydrocephalus. Yakovlev and Wadsworth (1946) suggest that hydranencephaly is a brain infarction developed during the embryonic period, due to occlusion of internal carotid arteries. Massive brain destruction has been described after neonatal viral infection
Fig. 2.46a–c Closed porencephaly in a 10-month-old child. MRI (a,b): sharply delineated cavities that are isointense to CSF in frontal lobes. PSIF (c): thin septa are present between cavity and ventricle
Fig. 2.47a–c Porencephaly of the left lateral ventricle in a 5-year-old child with epilepsy and rightward hemiparesis. МRI (а) in axial (Т2)
and (b,c) sagittal (Т1) planes: the CSF cyst is widely connected with the left lateral ventricle
58
Chapter 2
Fig. 2.48a–e Posterior fossa porencephaly in a 4-month-old child. Т2- weighted images (а–c) and Т1-weighted images (d,e): the CSF cyst in the left half of posterior fossa is connected with the fourth ventricle and subarachnoid space of the cervical portion of vertebral column. The third and lateral ventricles are dilated
and toxoplasmosis. Children may have micro-, normo- or megalencephaly. They markedly fail to thrive in both physical and mental development. Cerebral angiography in hydranencephaly often reveals thrombosis of supraclinoid portions of internal carotid arteries. According to our own institute's data, hydranencephaly is seen in 1.34% of cases among children with hydrocephalus. In most cases, CT and MRI pictures of hydranencephaly is typical: posterior fossa structures are correctly formed, thalami and basal ganglia are hypoplastic and the cerebral hemispheres consist of thin-walled vesicles filled with CSF. Sometimes islands of brain tissue are detected, which are located in different hemispheric regions. The falx cerebri, albeit incorrectly formed, is always seen on CT and MRI (Figs. 2.49, 2.50), which is what distinguishes it from alobar holoprosencephaly.
2.6.3 Multicystic Encephalomalacia Multicystic encephalomalacia is a result of a diffuse stroke that occurred during the intrauterine period, con- or postnatally. It appears as numerous cysts of various sizes and shapes, separated from each other by glial septi. Location of the lesions
depends on the stroke’s origin. After thrombosis or embolism, brain regions are affected by the vascular territories involved. Asphyxia damages cortex and peripheral white matter; in severe cases, only periventricular white matter remains intact. If the cause of encephalomalacia is infection, then location of lesions is not specific and depend on location of the inflammatory process. On CT, cystic hypodense lesions of various sizes and shapes, and separated by septi, are seen. These lesions are located in different affected brain regions, sometimes with calcification. On MRI, areas of encephalomalacia correspond to CSF signal on T1 and T2 sequences. Sometimes, the MR signal is heterogeneous due to glial septi and CSF components. The ventricular system may be variably dilated, depending on the severity of lesions (Fig. 2.51).
2.6.4 Hypoxic (Hypoxic–Ischaemic) Brain Lesions Hypoxic (hypoxic–ischaemic) brain lesions manifest themselves by different changes, depending on timing and location of lesions. Clinical signs in neonates include seizures, hypotonia in extremities and lethargy. Neonatal asphyxia decreases blood oxygen content (hypoxia), increases content of carbon
Congenital Malformations of the Brain and Skull
59
Fig. 2.49a–c Hydranencephaly in a 11-month-old child with severe psychomotor retardation. CT (а–c): posterior fossa structures are correctly formed, and the cerebral hemispheres appear as thin-walled vesicles filled with CSF. A large falx cerebri is partially present with islands of brain tissue alongside it
Fig. 2.50a,b Hydranencephaly in a
11-month-old child with severe psychomotor retardation. Т1-weighted (а) and Т2-weighted (b) images: cerebral hemispheres appear as thin-walled vesicles filled with CSF. Brain tissue appears as thin striae between CSF and cranial vault bones
Fig. 2.51a–c Multicystic encephalomalacia in a 3-year-old child. Т1-weighted (а,b) and Т2-weighted (c) images in axial and sagittal planes: cerebral hemispheres possess many cystic cavities filled with CSF that are separated by thin septi, and the ventricular system is dilated
60
Chapter 2
Fig. 2.52a–c Periventricular leukomalacia in a 1-year-old child with psychomotor retardation (placental detachment in his mother during labour). Т1-weighted (а) and Т2-weighted (b,c) images: white matter is underdeveloped, chains of hyperintensity in T2 images of various sizes within superior portions of the lateral ventricles bodies
dioxide, and causes systemic hypotension. Increased carbon dioxide and decreased oxygen content cause loss of autoregulation of brain vessels. Systemic hypotension combined with loss of vascular autoregulation causes brain hypoperfusion. On CT, hypodensity of white matter in periventricular areas, basal ganglia and thalami is seen. On MRI, foci of changed signal identical to CSF signal (periventricular leukomalacia) are revealed (Fig. 2.52).
2.7
Histogenesis Impairment
2.7.1 Neurocutaneous Disorders (Phakomatoses) Neurocutaneous disorders (phakomatoses) are congenital neurocutaneous disorders affecting numerous structures of neuroectodermal origin: nervous system, vessels, skin, retina, eyeball and sometimes viscera (Barkovich 2000; Gomez 1988; Hart et al. 2000; Kornienko et al. 1993; Smirniotopoulos et al. 1992). “Classic” syndromes include the following: neurofibromatosis types 1 and 2 (von Recklinghausen’s disease) Bourneville-Pringle disease, von Hippel-Lindau disease, Sturge-Weber syndrome (encephalotrigeminal angiomatosis) and neurocutaneous melanosis.
2.7.1.1
Neurofibromatosis (von Recklinghausen’s disease)
2.7.1.1.1 Neurofibromatosis Type I Neurofibromatosis type I (NF I) is one of the most frequent autosomal-dominant disorders of CNS, the locus for which is on chromosome q17 (Barkovich 2000; Bilaniuk et al. 1997;
Smirniotopoulos et al. 1992). Its incidence is 1 case per 3,000– 5,000 in the general population. Criteria of neurofibromatosis type 1 are as follows: over five café-au-lait spots on skin over 5 min in diameter in children and over 15 min in diameter in postpubertal period; two or more neurofibromas of any type or a single plexiform one; freckles in subaxillary and inguinal regions; optic nerve, chiasm and optic tract glioma (uni- or bilateral); two or more pigmented hamartomas of the iris (Lisch nodes); sphenoid crest dysplasia; thinning of cortical layer of long tubular bones; and NF type I in consanguine relatives. Clinical features of NF type I are café-au-lait spots on skin appearing during the first year of life, two or more neurofibromas, optic pathways glioma (and other intracranial astrocytomas), kyphoscoliosis, sphenoid crest dysplasia, vascular dysplasia, peripheral myelin sheath tumours, epilepsy and mental disorders. Optic pathway glioma is the most frequent sign of NF type I. One or both optic nerves chiasm and optic tracts may be affected, which is easily revealed on CT with contrast enhancement and MRI (Fig. 2.53). Fat-saturation sequences in MRI are useful for examination of the orbits. Astrocytomas may be located sub- as well as supratentorially. In NF type I, hydrocephalus is usually caused by Sylvian aqueduct stenosis, midbrain tegmentum or tectum glioma. The tumour is not detected by CT but always found on MRI. Vascular dysplasia may be presented by stenosis or occlusion of internal carotid artery or its major branches (due to proliferation of intima), or arterial aneurysm. Dysplasia of the sphenoid crest is the most frequently observed bony abnormality, which may cause intraorbital protrusion of temporal lobe and, hence, exophthalmus.
Congenital Malformations of the Brain and Skull
Fig. 2.53a–f NF I in a 5-year-old child with complete blindness and
café-au-lait spots on the skin. Т2-weighted (а–c) and Т1-weighted (d–f) images: glioma of the optic chiasm with a cystic component in the third ventricle cavity. The tumour expands alongside optic tracts.
61
Glioma of the right optic nerve, as well as multiple foci of hyperintensity in thalami, brainstem, and cerebellar hemispheres are seen, along with obstructive hydrocephalus at the foramina of Monroe level
62
Chapter 2
Fig. 2.54a–c NF II in an 8-year-old child. МRI with contrast enhancement: multiple tumours in sub- and supratentorial spaces, and nodular
tumours under the skin of the scalp
2.7.1.1.2 Neurofibromatosis Type II Neurofibromatosis type II (NF II) is also an autosomal-dominant disorder, the locus for which is on chromosome 22. The incidence is about 1 case per 5,000 in the general population (Castillo et al. 2000). Diagnostic criteria of NF type II are as follows: bilateral eighth cranial nerve neurinomas (confirmed on CT on MRI) or NF II in consanguine relatives; unilateral eighth cranial nerve neurinoma; or one of two signs of brain neurofibroma, meningioma, glioma or schwannoma; or two signs unilateral eighth cranial nerve neurinoma, multiple brain neurofibroma, meningioma, glioma, schwannoma or calcifications into the brain. Clinical features are caused by eighth cranial nerve tumours or neurofibroma, meningioma, glioma or schwannoma; the latter may be numerous. If NF II is suspected, then CT or MRI should be performed with contrast enhancement to define multifocal character of lesions (Figs. 2.54–2.56).
2.7.1.2
Sturge-Weber Syndrome (Encephalotrigeminal Angiomatosis)
Sturge-Weber syndrome (encephalotrigeminal angiomatosis) is a congenital sporadic disorder, but familial cases have been described. The type of inheritance is unknown (Barkovich 2000; Wasenko et al. 1990). Diagnostic criteria of Sturge-Weber syndrome are facial angioma, retinal angioma, meningial angiomatosis with atrophy of adjacent brain tissue, calcifications in affected brain regions, secondary glaucoma and generalised seizures. As usual, on craniograms peculiar calcifications alongside cerebral gyri are visualised. Frequently they are located in parieto-occipito-temporal regions (Fig. 2.57). On CT, calcifi-
cations of various sizes are found in cortical parts of hemispheres, sometimes markedly extended (Fig. 2.58). MRI may reveal hypointense periventricular veins. After intravenous contrast enhancement, meningeal angiomas accumulate contrast medium, repeating the picture of sulci and gyri. An enlarged choroid plexus of the ipsilateral lateral ventricle and periventricular veins are well contrasted. On MRI, small calcifications may be less discernible. The affected hemisphere is atrophic due to ischaemic change.
2.7.1.3 Bourneville-Pringle Disease (Tuberous Sclerosis) Bourneville-Pringle disease (tuberous sclerosis) is an autosomal-dominant disorder. Two genes are responsible for this disorder, TSC1 (located on chromosome 9q34), and TSC2 (located on chromosome 16p13/3). The incidence is 1 case per 100,000 in the general population (Gomez et al. 1988; Kinglsey et al. 1986). Barkovich (2000) outlined the following diagnostic criteria of Bourneville-Pringle disease. First-line histologically confirmed signs: facial angiofibroma, multiple fibromas, cortical tuberculi, subependymal nodules or giant-cell astrocytoma, multiple retinal astrocytomas and multiple calcified subependymal nodules protruding into ventricular lumen (confirmed by CT and MRI). Second-line signs: the disorder in consanguine relatives, cardiac rhabdomyoma, retinal hamartoma or achromatic proliferations, cerebral tubercles (by CT and/or MRI), noncalcinated subependymal nodules (in CT or MRI), Sjögren’s patches, plaques on the forehead, lymphangiomyomatosis of lungs, angiomyolipoma of the kidney and kidney cysts. Third-line evidence: depigmented spots, multiple white nevus, pink and red papules (“confetti-like” skin lesions), kidney cysts, chaotic distribution of enamel on primary or permanent teeth, hamartoma-like rectal polyps, cysts of bones, liver
Congenital Malformations of the Brain and Skull
63
Fig. 2.55a–h NF II in a 13-year-old child. CT (а–e) and МRI (f–h) before and after contrast enhancement: bilateral neurinomas of both eighth cranial nerves are seen. On CT in the “bony window”, dilation of the internal acoustic meatus bilaterally is clearly seen. On MRI with contrast enhancement (h), homogeneous accumulation of contrast medium within the tumour tissue is seen
64
Chapter 2
Fig. 2.56a–f NF II in a 15-year-old child. Т1-weighted image before (а,b) and after contrast enhancement (c–f): giant neurinoma of the right eighth cranial nerve and multiple neurinomas in the vertebral canal
Fig. 2.57a,b Sturge-Weber syndrome in an
8-year-old child. X-ray craniograms: typical calcifications in the left occipital region
Congenital Malformations of the Brain and Skull
65
Fig. 2.58a–c Sturge-Weber disease in a 4-year-old child. CT (а): multiple calcifications lining fissures and gyri of right temporo-occipital regions. The right lateral ventricle is enlarged. MRI (b,c) shows foci of hypointensity (calcifications) in the right hemisphere, which is smaller than the left one
and kidney hamartomas, lymphangiomyomatosis of lungs, heterotopy and infantile spasms. Tuberous sclerosis may be diagnosed in a patient having a single first-line sign or two second-line signs, or a single second-line and two third-line signs. Tuberous sclerosis is probable if a patient has one secondline and one third-line sign, or three three-line signs. Tuberous sclerosis is suspected if a patient has one secondline and two third-line signs. The most frequent manifestations of tuberous sclerosis are myoclonic seizures since early childhood, psychiatric symptoms, adenomas of sebaceous glands and retinal hamartoma. Multiple calcifications are revealed within the walls of lateral ventricles and in brain parenchyma on X-ray craniograms. The walls of the third and the lateral ventricles sometimes contain subependymal nodules isodense with brain parenchyma (subependymal hamartomas that calcinate with disease progression), as well as calcinated foci, and are seen on CT (Fig. 2.59). On MRI, subependymal hamartomas are distinguished as nodules isointense with white matter that protrude into the lumen of the ventricle, and cortical nodules are hyperintense on Т2-weighted images. Infrequently (in about 15% of tuberous sclerosis cases) subependymal giant-cell astrocytomas are found within interventricular foramina. On CT and MRI, they are usually isointense and isodense, with good contrast enhancement (Fig. 2.60).
2.7.1.4
von Hippel-Lindau Disease
von Hippel-Lindau disease (angiomatosis of the central nervous system) is an autosomal-dominant disorder, the gene being located on chromosome 3p25–p26 (Barkovich 2000; Hart
et al. 2000). Its diagnostic criteria are its permanent signs, such as retinal angioma; cerebellar hemangioblastoma; spinal hemangioblastoma; and inconstant signs such as kidney carcinoma; pheochromocytoma; liver angioma; and kidney, liver and pancreatic cysts. Clinical features depend on the extent of cerebellar involvement, spinal cord and retina. CT reveals a cystic tumour, with contrast enhancement in the nodular part, which is less pronounced in the cyst walls. MRI reveals a cystic clear-cut tumour: MR signal from a tumour nodule markedly increases after intravenous contrast enhancement (Fig. 2.61).
2.7.1.5
Neurocutaneous Melanosis
Neurocutaneous melanosis is a very rare disease of this group, which was described for the first time by J. Rokitansky in 1861. The type of inheritance is not known. Diagnostic criteria are a large single or multiple small and moderate pigment nevi on skin, brain melanoma and/or meningeal melanosis. The disorder manifests by multiple congenital pigment nevi on the skin (more frequently on the posterior sides of trunk and extremities, brown or black in colour), which are often confluent into large fields, without signs of malignancy, and by intracranial brain and meningeal melanomas. Histology reveals accumulation of melanocytes on the ventral surface of the brainstem, in nuclei and cerebellar white matter, in cervical and lumbar vertebral regions, in the anterior portions of temporal lobes and in the amygdale, thalami and basal portions of dura and pia mater. The clinical picture is characterised by cerebral involvement and manifests as headaches, vomiting, dizziness and so forth. The characteristic MRI fea-
66
Fig. 2.59a–i Tuberous sclerosis in a 1-year-old child with epilepsy, manifested at 5 months of age. CT (а–c) reveals multiple calcinated foci of various sizes in the lateral ventricles walls, foci of heterogeneous density in the left frontal region and hypodense focus in the right temporal focus. Т2-weighted images (d–f) reveal hyperintense foci in the white matter of cerebral hemispheres and in subcortical
Chapter 2
brain regions bilaterally. MRI using Т1-weighted images (g–i) reveals hyperintense foci in the lateral ventricles walls and in white matters of both cerebral hemispheres. A large lesion in the left frontal region of cortical and subcortical location has a heterogeneous signal on both sequences
Congenital Malformations of the Brain and Skull
Fig. 2.60a–f Subependymal giant-cell astrocytoma in a 15-year-old
child with tuberous sclerosis. CT with contrast enhancement (a,b): a tumour with heterogeneously increased density with few peripheral calcifications within anterior horn of the right lateral ventricle. Various sizes of calcifications subependymally and in the white matter and hydrocephalus are seen. Т2-weighted (c,d) and Т1-weighted (e,f)
67
images: the tumour is isointense with cerebral grey matter. Small cysts (hyperintense lesions) appear in its stroma. There is hydrocephalus present. Hypointense calcification is seen in the right lateral ventricle wall. Calcifications in the white matter are weakly differentiated (to as compared with CT)
Fig. 2.61a–c Craniospinal hemangioblastoma in a 15-year-old child. Т2-weighted (а), Т1- weighted (b,c) images after contrast enhancement:
a small tumour nodule is seen within the cystic cavity, which intensely accumulates contrast medium
68
Fig. 2.62a–i Neurocutaneous melanosis in a 9-year-old child. MRI
before (a–d) and after contrast enhancement (e–i). The right occipital region melanoma on the Т1-weighted image (without contrast enhancement) is isointense; in the central part of the T2-weighted image. A small hyperintense lesion is located in the central part of the T2-weighted image, suggestive of melanin. Melanin deposits are
Chapter 2
found in amygdale nucleuses bilaterally. On the Т2-weighted image (d) in the sagittal plane, there is a hyperintense lesion (melanin deposits with hamartoma-like changes of brain stem tissue); after contrast enhancement, contrast medium accumulation is seen in pathological lesions and meninges
Congenital Malformations of the Brain and Skull
ture is hyperintensity of the amygdale and other affected regions of brain and spinal cord and their meninges (Fig. 2.62).
2.8
Arachnoid Cysts
An arachnoid cyst is a congenital extracerebral mass that contains CSF encircled by walls composed of arachnoid membrane. Internal and external walls of the cyst consist of thin layers of arachnoid cells and join unchanged arachnoid membrane at the margins. True (congenital) arachnoid cysts contain specific membranes and enzymes possessing secretory activity (Barkovich 2000; Galassi et al. 1982; Kornienko et al. 1993; Muhametjanov et al. 1995). According to the data of the Burdenko Institute of Neurosurgery, arachnoid cysts make up about 10% all masses of brain in children, 7.4% of cases are found in children with hydrocephalus, 4% of cases in children with open hydrocephalus and in 11.5% of cases in children with obstructive hydrocephalus. Clinical features of arachnoid cysts depend on their location, volume and relation to CSF spaces (Fig. 2.63). They may not cause neurological deficits for a long period. These cysts may develop in late childhood or adulthood. Cysts located close to CSF pathways manifest themselves by showing early signs of progressive hydrocephalus. This is explained by mechanical compression of CSF pathways as well as with impairment of venous flow due to CSF stasis in the basal cisterns. As a result, the asymptomatic period becomes shorter, and neurological signs are more severe due
69
to proximity of arachnoid cysts to brainstem, diencephalic structures, Sylvian aqueduct and the third and the fourth ventricles. The common feature is a predominance of progressive hydrocephalus signs that mask focal neurological signs—due to the significant ability of children to compensate for the neurological signs. Only in the stage of decompensation do signs of increased exposure of adjoining structures to mass of arachnoid cysts appear: In retrocerebellar cysts, there are cerebellar and brainstem signs. In cysts of the incisura tentorii and cerebellopontine angle, there are pyramidal signs due to brainstem compression. In suprasellar cysts, there is involvement of cerebral and oral portions of the brainstem, and chiasm and optic nerves, as well as presentation of hyperkinesis, endocrine and diencephalic signs. CT and MRI are the main diagnostic tools for arachnoid cysts. They reveal straightforward homogeneous masses isodense and isointense with CSF in all sequences, unevenly separated from walls of adjacent lateral ventricles. In contrast to tumours, arachnoid cysts do not show contrast enhancement and perifocal oedema. If a sub- or supratentorial suprasellar arachnoid cyst, or a cyst located in the cerebellopontine angle or incisura tentorii, is suspected, then it is necessary to perform CT ventriculography (CTVG) to distinguish a cyst from dilated ventricular system. CTVG reveals a defect of contrast accumulation where a cyst is present. Arachnoid cysts—irrespective of their location—may be completely or partially connected with the subarachnoid space or isolated. Connection between arachnoid cysts with the subarachnoid space (or its absence) may be revealed by CT cisternography
Fig. 2.63a,b Illustration of intracranial arachnoid cyst location (а lateral, b medial brain surface). 1 cyst of the lateral cerebral fissure, 2 cyst of convex brain surface, 3 parasagittal cyst, 4 suprasellar cyst, 5 intrasellar cyst, 6 tentorium cerebelli cyst, 7 superior retrocerebellar cyst, 8 inferior retrocerebellar cyst, 9 cerebellopontine angle cyst
70
Fig. 2.64a–c Retrocerebellar arachnoid cyst in a 14-year-old child. The cyst is situated near the internal occipital eminence, and compresses and produces deformity of the fourth ventricle (isodense to
Chapter 2
CSF). The third and the lateral ventricles are dilated. Periventricular oedema near anterior and posterior horns of the lateral ventricles is noted
Fig. 2.65a–d Retrocerebellar arachnoid
cyst in a 1-year-old child. МRI in axial (а,b) and sagittal (c) planes reveals a cyst occupying the most part of posterior fossa. Compressed posterior fossa structures are displaced in the anterior direction. PSIF (d) reveals CSF flow from the cyst into the subarachnoid space of the spinal cord
Congenital Malformations of the Brain and Skull
Fig. 2.66a–c Giant superior retrocerebellar arachnoid cyst in an
8-month-old child with progressive hydrocephalus. MRI in axial and sagittal planes: T2-weighted (а) and Т1-weighted (b) images. MR signal of the cyst is isointense to CSF. The cyst is located above and
(CTCG), MRI PSIF, or MRI and CT with intrathecal injection of contrast media mixture (Galassi et al. 1982).
2.8.1 Arachnoid Cysts of the Posterior Fossa Arachnoid cysts of the posterior fossa may originate from the cisterna magna, in which case they are called inferior retrocerebellar cysts. The area of hypodensity and MR signal changes in these cases is located in the posterior inferior portions of posterior fossa and expands into both cerebellar hemispheres (symmetrically or asymmetrically). The fourth ventricle is displaced upwards along with cerebellar hemispheres. Superior retrocerebellar cysts are located in the superior portions of cerebellum and expand into both cerebellar hemispheres. These cysts are regarded as an abnormality of lateral pontine cistern. Giant retrocerebellar cysts, taking up the major part of posterior fossa, cause obstructive hydrocephalus (Fig. 2.64). Retrocerebellar cysts, pervading posterior fossa structures, cause compression of CSF pathways and markedly dilate the ventricular system (Figs. 2.65–2.67). There are difficulties in distinguishing posterior fossa cysts from tumoral cysts and Dandy-Walker malformation. If contents of a mass are denser than CSF is, then tumour is more likely. Cerebellopontine angle arachnoid cysts, originating from the lateral pontine cistern, may be located only in the posterior fossa, sub- and supratentorial in middle cerebral fossa, which leads to suspicion of a dilated inferior horn of the lat-
71
behind cerebellum, more rightwards; it intrudes into the supratentorial space, compressing the third ventricle. The Sylvian aqueduct is visualised but narrowed; the fourth ventricle is compressed. PSIF images a turbulent CSF flow via foramina of Monroe
eral ventricle. A large amount of the supratentorial portion of an arachnoid cyst may cause compression of the lateral wall of the lateral ventricle. Local signs of this fraction of a cyst are thinning and protrusion of the cranial bones that form middle cerebral fossa, due to long-term exposure of still-notfirm cranial bones to compression by a mass. A subtentorial cyst (or a part of a cyst that is located sub- and supratentorial) displaces and compresses the fourth ventricle (Fig. 2.68). Arachnoid cysts of incisura tentorii originate from this group of cisterns and have sub- and supratentorial components of different or identical volume. They usually compress the brainstem markedly, as well as the Sylvian aqueduct, which causes marked dilatation of the third and the lateral ventricles. Quadrigeminal and circumferential cisterns are usually involved. The degree of their participation in cyst origin is variable. Cysts originating from lamina tecti cistern are positioned medially; they compress brainstem and cause deformity of the posterior portion of the third ventricle. Large and giant cysts expanding into the interhemispheric fissure dislocate and cause deformity of medial walls of the lateral ventricles. On the side of predominant cyst location, the lateral ventricle changes its shape, and the contralateral ventricle becomes dilated to a lesser extent, being exposed to milder compression (Fig. 2.69). CTVG reveals a defect of accumulation where the cyst is located; the lateral ventricles are well contrasted. Sagittal and coronal MRI allow judgement about the relationship of a cyst to adjacent structures of the middle cerebral fossa, midbrain and cerebral hemispheres.
72
Fig. 2.67a–f Giant retrocerebellar arachnoid cyst. CT (а,b) reveals a
large CSF cyst that occupies the major part of posterior fossa. Cerebellum and brainstem are deformed and pushed into the anterior direction. Т2-weighted (c,d) and Т1-weighted (e) images demonstrate
Chapter 2
that the cyst expands into oral and caudal directions. PSIF (f) reveals turbulent CSF flow in a cystic cavity. There is no CSF flow from the cyst into the subarachnoid space of the spinal cord
Congenital Malformations of the Brain and Skull
Fig. 2.68a–f Case 1. An arachnoid cyst in the cerebellopontine angle
in a 2-year-old child, sub- and supratentorial location. CТ (а–c): the cyst is isodense to CSF, and the third and the lateral ventricles are markedly dilated due to occlusion of the aqueduct of Sylvius. Case 2,
73
MRI (d–f): posterior fossa arachnoid cyst in left cerebellopontine angle. The fourth ventricle is compressed. The third and the lateral ventricles are very large
74
Fig. 2.69a–f Arachnoid cyst of tentorium cerebelli in a 2-year-old
child. CT (а,b): a cyst containing CSF is located in sub- and supratentorial spaces. Т1- and Т2- (c–e) weighted images in axial and sagittal planes: a cyst compresses and produces deformity of brainstem, and
2.8.2 Suprasellar Arachnoid Cysts Suprasellar arachnoid cysts are the most difficult in terms of diagnosis, as they may imitate dilated chiasmal cisterns and the third ventricle (Fig. 2.70). In most cases, the cavity of the third ventricle invaginated, causing its marked dilatation and occlusion of the Monroe foramina (Fig. 2.71). Sometimes they protrude through enlarged foramina of Monroe (uni- or bi-
Chapter 2
posterior portion of the third and the fourth ventricles—obstructive hydrocephalus. Series of CTVG (f): an accumulation defect within the arachnoid cyst is seen on the background of the contrasted part of the lateral and the third ventricle
laterally) into the lumen of the lateral ventricles. Suprasellar arachnoid cyst volume enlarges quite slowly, and hydrocephalus is well compensated in the initial stage. The main CT sign of a suprasellar arachnoid cyst expanding into the third ventricle is a balloon-shaped dilation of the latter and marked dilation of the lateral ventricle, which is sometimes asymmetrical. A follow-up CT after lateral ventricles shunting erases doubt of the presence of this arachnoid
Congenital Malformations of the Brain and Skull
75
Fig. 2.70a–c Suprasellar arachnoid cyst in a 9-year-old child. Т2-weighted (а) and Т1-weighted (b) images: a small arachnoid cyst located in the suprasellar area; its posterior border is in the interpeduncular cistern. The bottom of the third ventricle is lifted. The optic chiasm is pushed forward. PSIF in the sagittal plane (c) demonstrates a turbulent CSF flow via foramina of Monroe, the third and the fourth ventricles, and the Sylvian aqueduct. MR signal of the cyst is isointense to CSF
Fig. 2.71a–c Suprasellar arachnoid cyst expanding into the cavity of
the third ventricle in a 2.5-year-old child. CT (а): balloon-shaped dilation of the third ventricle; the lateral ventricles are dilated. MRI in
sagittal plane, Т1-weighted image (b) and PSIF (c): marked dilatation of the third ventricle; the lumen of the aqueduct of Sylvius is intact
76
Chapter 2
Fig. 2.72a–f Suprasellar arachnoid cyst expanding into the cavity of the third ventricle and via foramina of Monroe into the lateral ventricles in a 2-year-old child. CT (а–d): the third ventricle is balloonshaped and dilatated; the lateral ventricles are markedly enlarged.
The cyst borders are not visualised. CTVG (e,f): defects of its accumulation are clearly seen in the site of the cyst in the third ventricle cavity and adjacent portions of the lateral ventricles (near foramina of Monroe)
Fig. 2.73a–c MR cisternography in three planes of a 10-year-old
cyst within the third ventricle cavity, which goes via interventricular foramen into the left lateral ventricle. MR cisternography confirms the connection between arachnoid cyst and skull-base cisterns–communicating cyst
child with suprasellar arachnoid cyst, expanding into the cavity of the third ventricle and the left lateral ventricle. Contrast medium injected intrathecally filled the skull-base cisterns and suprasellar
Congenital Malformations of the Brain and Skull
cyst, as the dilated third ventricle does not dwindle in volume, retaining its balloon-like shape. Additionally, the diagnosis of a suprasellar arachnoid cyst may be confirmed by CTVG and CTCG. CTVG reveals defect of accumulation in the third ventricle, and if the cyst penetrates into the lateral ventricle(s), then the additional defect is seen within the Monroe foramina (Fig. 2.72). In cardiac-gated phase-contrast MRI (CG pcMRI), it is possible to detect connection between the arachnoid cyst and basal brain cisterns (Fig. 2.73). MRI PSIF is a reliable technique used to diagnose the connection between a suprasellar arachnoid cyst and basal brain cisterns. Pulsatile flow, not detected before surgery, becomes clear after a third
77
ventriculostomy, when signal from CSF flow from the third ventricle to the interpeduncular cistern is lost (Fig. 2.74).
2.8.3 Arachnoid Cysts of Lateral Cerebral Fissures Arachnoid cysts of lateral cerebral fissures are most frequently seen among supratentorial cysts. They may be uni- or bilateral, remain asymptomatic for a long time and infrequently are an occasional finding in CT or MRI. Clinical manifestation begins when a cyst reaches a large volume and causes displacement and deformity of ventricular system (Figs. 2.75–2.77).
Fig. 2.74a–d MRI in a 2-year-old child after the third ventricle’s ventriculostomy for
suprasellar arachnoid cyst expanding into the cavity of the third ventricle. Т1-weighted image (а): a cyst with polycyclic borders is located in the suprasellar area and the third ventricle. b PSIF: loss of signal from CSF flow in the interpeduncular, prepontine and premedullary cisterns. c,d Т2-weighted image: a focus of signal loss from CSF flow in the bottom of the third ventricle and the prepontine cistern
78
Chapter 2
Fig. 2.75a–c Lateral cerebral fissure arachnoid cyst leftwards in a 5-year-old child with epilepsy. CT: a mass with even, clear-cut borders,
isodense to CSF in the lateral cerebral fissure leftwards; the left lateral ventricle is compressed, and the ventricular system is displaced rightwards
Fig. 2.76a–c Lateral cerebral fissure arachnoid cyst leftwards in a 10-year-old child with epilepsy. Т2-weighted (а) and Т1-weighted (b,c) images: c see next page
Congenital Malformations of the Brain and Skull
79 Fig. 2.76a–c (continued) there is a large left lateral cerebral fissure arachnoid cyst isointense to CSF in the lateral ventricles. Adjacent brain structures are compressed, and the ventricular system is slightly displaced rightwards
Fig. 2.77a–c Lateral cerebral fissure arachnoid cyst rightwards in a 7-year-old child. CT without contrast enhancement (a): there is a mass isodense to CSF in the right temporal region. CTVG (b,c): a
contrast medium filled the skull-base cisterns and partially reached the cyst cavity and ventricular system (partially communicating arachnoid cyst)
80
Chapter 2
Fig. 2.78a–c Giant interhemispheric cyst of the left parietal region and agenesia of corpus callosum in a 6-year-old child. МRI: in axial and sagittal (а,b Т1-weighted) and coronal (c Т2-weighted image) planes. The cyst occupies the major part of the parietal lobe,
its medial border is adjacent to falx cerebri, and the corpus callosum is not visualised. MR signal of the cyst is identical to CSF on both sequences
2.8.4 Interhemispheric and Parasagittal Arachnoid Cysts
Forms of craniosynostosis derive their names from the prematurely fused suture(s) involved: coronal, sagittal, lambdoid and mixed. Craniosynostosis may also be accompanied by intracranial hypertension. Diagnosis is based on clinical signs, changes in skull shape and X-ray craniography findings; the latter reveal marked “fingerprints” in skull bones, absence of a single or many sutures and changes of cerebral fossa shapes. 3D CT may depict completely changes in the skull shape, its bones, density of brain tissue and size of the ventricular system (sometimes enlarged). If craniosynostosis is combined with facial bony abnormalities, then the case is classified as a craniofacial syndrome or craniofacial dysraphism. Crouzon syndrome (of autosomal-dominant inheritance) is a combination of coronal craniosynostosis with orbital hypertelorism, exophtalmus, a beak-shaped nose and micrognathism. Apert syndrome (of autosomal-dominant inheritance) is a combination of coronal craniosynostosis with orbital hypertelorism, hypoplasia of median facial structures (flat face), obliquity of eye fissures and syndactyly. Cloverleaf syndrome (of autosomal-recessive inheritance) presents with a trefoil-like head shape, low positioning of ear helices and facial deformity (Fig. 2.81). Platybasia is a flattening of skull base with dwindling of the basal angle (a junction of line from nasion to the tubercle of sella turcica or its centre, with the line going from this point to the anterior margin of foramen magnum). Normally, the angle is 125–140° (Fig. 2.82). Basilar impression is a protrusion of foramen magnum and superior cervical vertebrae into the cranial cavity, combined infrequently with developmental defects of superior cervical vertebrae. Changes in relationship between bony structures,
Interhemispheric and parasagittal arachnoid cysts are located in the interhemispheric fissure and are adjacent to the falx cerebri (Fig. 2.78). Usually, CT and MRI reveal a combination of these cysts with agenesia of corpus callosum, and infrequently with porencephaly. CTVG and MRI confirm the diagnosis of interhemispheric arachnoid cysts, as these procedures allow ascertainment of the relationship between ventricles and a cyst, the walls of which are poorly visualised on axial CT scans.
2.9
Congenital Anterior Cranial Malformations
2.9.1 Craniosynostosis Craniosynostosis is a premature fusion of one or more cranial sutures. In congenital craniosynostosis, clinical manifestations are more severe, as in almost all of these cases all sutures are fused. Due to premature closure of a single or many sutures, the growth of skull becomes limited. Compensatory skull growth causes changing in the skull’s shape. There are several types of skull deformities: • Scaphocephaly (sagittal suture synostosis) • Brachycephaly (bicoronal synostosis) • Oxycephaly (turricephaly and high-head syndrome) • Acrocephaly or “tower-like skull” (synostosis of all sutures; Fig. 2.79) • Trigonocephaly (premature fusion of the frontal metopic suture; Fig. 2.80) • Plagiocephaly or “askew skull” (unilateral coronal synostosis; frontal and occipital displacement due to premature fusion of the half of coronal and lambdoid sutures)
Congenital Malformations of the Brain and Skull
Fig. 2.79a–i Complete craniostenosis in an 11-year-old child. 3D CT
(а–c), appearance of cranial bones from inside (d,e): fingerprints in the cranial vault bones are markedly enhanced, sutures are not differentiated and the skull-base fossae are shortened. CT in three planes
81
(f–i): orbits are widely separated, density of brain parenchyma is not changed and the ventricular system is correctly located and not dilated
82
Chapter 2 Fig. 2.80a,b Trigonocephaly in a 9-month-
old child. MRI (a,b): The shape of posterior fosse is normal; there is pointed frontal region. There are no signal intensity alterations of brain tissue at sub- and supratentorial locations
Fig. 2.81a–c Cloverleaf syndrome with Chiari II in a 9-month-old child. CT (a–c): the head has an asymmetrical trefoil shape (cloverleaf);
herniation of cerebellar contents into the cervical canal to the C2 level is seen, and the tentorium is placed low. Marked hydrocephalus is present Fig. 2.82a,b Platybasia in a 10-year-old
child. МRI: Т1-weighted (a) and Т2weighted (b) images: flattening of skull base is seen, the basal angle is increased and the brainstem is deformed
Congenital Malformations of the Brain and Skull
83 Fig. 2.83a,b MRI in a 2.5-year-old child
with basilar impression and Chiari II malformation. On Т1-weighted (a) and Т2weighted (b) images, the pons and medulla are elongated with deformity, the lower pole of cerebellar tonsils is narrowed at the С3 level, the fourth ventricle is elongated and narrowed and the tentorium cerebelli is situated downwards. The cervical spine protrudes into the posterior fossa
posterior fossa structures and basal cisterns cause hydrocephalus (Fig. 2.83). Amniotic deformities (unequal conjoined twins) draw surgeons’ attention, as it is possible to separate them (Konovalov et al. 1991). Craniopagus parasiticus is an instance of twins, one of whom is a parasitic twin head (with an undeveloped or underdeveloped body) conjoined to the head of the developed twin. We observed three cases of craniopagus parasiticus. In all cases, selective cerebral angiography was performed to ascertain cerebral blood supply. Partial blood supply of
each child’s brain with vessels of the other child was found on angiography, and according to contemporary classification, these cases were related to the fourth group of craniopagus parasiticus. In the third case, CT and MRI were performed in addition to angiography, and no pathological changes of density or MR signal were revealed. Only a deformity due to enlargement and rotation of one child’s head against the other’s head was found. The first two twins were not separated, and the third pair of twins was successfully separated; since then, children developed relatively normally (Fig. 2.84).
84
Chapter 2
Congenital Malformations of the Brain and Skull
9 Fig. 2.84a–f Craniopagus parasiticus twins. Angiograms (а,b carotid, c vertebral) reveal crossed cerebral blood supply. Photo (d) and X-ray craniogram (e) of twins before surgery and photos (f) of children after surgery. g,h MRI of one of the girls 9 years after surgery: Structures of posterior fossa are not changed and correctly located. In the right parietal region, there is a clearly delineated area of high signal intensity, possibly due to ischaemia after surgery. The right lat-
85
eral ventricle is wider than the left one, and the subarachnoid spaces of a convex brain surface are dilated rightwards. i MRI of the second twin: a large area of changed signal isointense to CSF in a T1-weighted image in the right temporal hemisphere (porencephalic cavity). j MR angiogram (MRA): asymmetrical location of arteries of the right and the left cerebral hemispheres and branches of basilar artery
86
Chapter 2
Refere n c e s Altman N et al (1992) Posterior fossa malformations. AJNR Am J Neuroradiol 13:691–724 Arendt A (1968) [Fundamentals of paediatric neurosurgery.] Medicina, Moscow (in Russian) Barkovich A (2000) Pediatric neuroimaging, 3rd edn. Lippincott Williams & Wilkins, Philadelphia Barkovich A et al (1992) Gray matter heterotopias: MR characteristics and correlation with developmental and neurologic manifestations. Radiology 182:493–499
Kingsley D et al (1986) Tuberous sclerosis: a clinicoradiological evaluation of 110 cases with particular reference to atypical presentation. Neuroradiology 28:38–46 Knaap M van der et al (1988) Classification of congenital abnormalities of the CNS. AJNR Am J Neuroradiol 9:315–326 Knaap M van der et al (2006) Cerebral white matter abnormalities in 6p25 deletion syndrome. AJNR Am J Neuroradiol 27:586–588 Konovalov A et al (1991) [The successful separation of a craniopagus.] Zh Vopr Neirokhir Im N N Burdenko 2:3–10 (in Russian)
Bilaniuk L et al (1997) Neurofibromatosis type 1: brain stem tumours. Neuroradiology 39:642–653
Kornienko V, Ozerova V (1993) [Paediatric neuroradiology.] Medicina, Moscow (in Russian)
Byrd S et al (1988) The CT and MR evaluation of lissencephaly. AJNR Am J Neuroradiol 9:923–927
Manelfe C, Sevely A (1982) Neuroradiological study of holoprosencephalies. J Neuroradiol 9:15–45
Byrd S et al (1989) The CT and MR evaluation of migrational disorders of the brain. Part I. Lissencephaly and pachygyria. Pediatr Radiol 19:151–156
McLaurin RL (1985) Dandy-Walker syndrom. In: Neurosurgery Ed.Wilkins M, Rengahary S. MCGraw-Hill Book Company 215156
Castillo M et al (2000) Imaging of congenital abnormalities of the brain. In: Orrison W (ed) Neuroimaging. Saunders, Philadelphia, pp 1516–1536
Muhametjanov H et al (1995) [Congenital intracranial arachnoid cysts in children.] Almaty, Tylyn (in Russian)
Delvert J (1982) Anterior dysraphism. J Neuroradiol 1:71–89
Naidich T et al (1983) Chiari II malformation: part IV. The hindbrain deformity. Neuroradiology 25:179–197
DeMyer W (1971) Classification of cerebral malformations. Birth Defects 7:78–9
Naidich T et al (1992) Cephaloceles and related malformations. AJNR Am J Neuroradiol 13:655–690
Fitz CR (1983) Holoprosencephaly and related entities. Neuroradiology 25:225–238
Raybaud C (1983) Destructive lesions of the brain. Neuroradiology 25(4):265-91
Galassi E et al (1982) CT scan and metrizamide CT cisternography in arachnoid cysts of the middle cranial fossa: classification and pathophysiological aspects. Surg Neurol 17:363–369
Polianker Z et al (1965) [A combination of congenital craniocerebral hernia with other craniocerebral maldevelopment.] Vopr Okhr Materin Det 12:39–42 (in Russian)
Glenn O, Barkovich A (2006) MRI of the fetal brain and spine: an increasingly important tool in prenatal diagnosis: part 1. AJNR Am J Neuroradiol 27:1604–1611
Probst F (1979) The prosencephalies. Springer, Berlin Heidelberg New York
Glenn O, Barkovich A (2006) MRI of the fetal brain and spine: an increasingly important tool in prenatal diagnosis: part 2. AJNR Am J Neuroradiol 27:1807–1814 Gomez M (1988) Tuberous sclerosis, 2nd edn. Raven, New York Hart B et al (2000) Neurocutaneous syndromes. In: Orrison W (ed) Neuroimaging. Saunders, Philadelphia, 1717–1759
Smirniotopoulos J et al (1992) The phakomatoses. AJNR Am J Neuroradiol 13:725–746 Toelle S et al (2002) Rhombencephalosynapsis: clinical findings and neuroimaging in 9 children. Neuropediatrics 33:209–214 Wasenko J et al (1990) Sturge-Weber syndrome: comparison of MR and CT characteristics. AJNR Am J Neuroradiol 11:215–220
Harwood-Nash D et al (1976) Neuroradiology in infants and children. Mosby, St. Louis
Yakovlev P, Wadsworth R (1946) Schizencephalies: A study of the congenital clefts in the cerebral mantle, J.Neuropathol ExpNeurol 5:116-130
Irger I (1981) [Dandy-Walker syndrome.] Vopr Neirokhir 2:51–59 (in Russian)
Yokota A et al (1986) Anterior basal encephalocele of the neonatal and infantile period. Neurosurgery 19:468–478
Chapter 3
3
Cerebrovascular Diseases and Malformations of the Brain
3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20
Stenosis and Thrombosis of the Cerebral Vessels . . . . . . . . .. . Cerebral Ischaemia .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lacunar Infarction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Chronic Ischaemic Brain Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stroke in Children .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Non-Atherosclerotic Stenosis and Occlusion of Cerebral Arteries . . . . . . . . . . . . . . . . . . . . . . . . . . Thrombosis of the Venous Sinuses .. . . . . . . . . . . . . . . . . . . . . . . . . Haemorrhagic Infarction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Intracerebral Haemorrhages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Extracerebral Non-traumatic Haemorrhages .. . . . . . . . . . . . . . Intratumoral Haemorrhages .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hypertense Haemorrhages .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hypertense Encephalopathy .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rare Causes of Intracerebral Haemorrhage . . . . . . . . . . . . . .. . Intracranial Arterial Aneurysms .. . . . . . . . . . . . . . . . . . . . . . . . . .. . Intracranial Vascular Malformations .. . . . . . . . . . . . . . . . . . . . .. . Carotid–Cavernous Fistulas .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cavernous Angioma .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Capillary Telangiectasias .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Venous Malformations .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1
Stenosis and Thrombosis of the Cerebral Vessels
87 101 139 154 158 160 172 175 176 188 193 196 197 197 199 247 302 309 316 320
Atherosclerotic lesions of the vessels, leading to stenosis and occlusion of the epiaortic and cerebral arteries, are one of the main causes of brain infarction in adults (Seeger 1995). Atherosclerosis accounts for 90% of brain thromboembolisms in the developed countries.
3.1.1 Atherosclerosis of the Cervical and Cerebral Vessels The pathogenesis of atherosclerotic transformation of blood vessel wall is in fact a multifaceted process. The main reasons are alteration (or the response to the alteration of vessel’s wall) and abnormalities of cell proliferation, somewhat resembling that in a malignant transformation. The above-mentioned factors may work alone or in combination in atherosclerotic lesion development.
The first stage of plaque organization is likely to be linked to local changes of the vessel endothelium or minimal alteration of intima. Platelet aggregation starts at the site of such alteration. The damaged endothelium becomes permeable for large molecules such as lipoproteins. Phagocytes and smooth muscle cells migrate to the site of alteration, and they begin to proliferate and accumulate fat esters that slip through damaged wall. Their subsequent death leads to release of the cell’s detritus that in turn serves a main substratum for the cholesterol plaque. Further development of this process results in creation of a fibrous covering (which covers fat-containing cells that continue to accumulate detritus and cholesterol crystals). Secondary inflammatory changes are accompanied by growth of granulation tissue and neovascularisation. Atherosclerotic plaques often contain small haemorrhages and necrotic areas. The plaque damage leads to the disruption of the relatively smooth surface of internal artery wall, and ulcerations in the degenerated plaque are the sites where thrombi form—these are the main sources of the subsequent distal thromboembolism.
3.1.2 Classification of Artery Stenosis As a rule, the atherosclerotic process leading to stenosis is located in the bifurcations and ostia of big arteries. Atherosclerosis affects carotid arteries more frequently (the difference is 20%) than it does arteries of posterior circulation territory. Lesions of the extracranial parts of carotid arteries are found fourfold more frequently than are lesions of the intracranial parts of carotids. The degree of cervical artery stenosis is estimated as a ratio between the square of the functioning part of artery at the site of stenosis and square of the same artery in the site not affected by stenosis (Ferguson et al. 1999). The absence of blood-flow imaging means complete artery occlusion. The crucial point in treatment selection (conservative therapy or surgical–endovasal intervention) is the level of stenosis. In this regard, all stenoses are divided into two categories: (1) stenoses less than 50%—in these cases, surgical inter-
88
Chapter 3
Fig 3.1a,b CTA of cervical arteries. MIP reconstruction in frontal (a) and axial projections (b). Atherosclerotic plaque with heterogeneous structure is visualised within the ostium of the right internal carotid artery
vention should not be performed; and (2) stenosis more than 70–75%—in these cases, surgical intervention is preferable. It is important to assess the consistency (using CT) and echo characteristics (using ultrasound) of the atherosclerotic plaque, which narrows the artery, in order to define the strategy of surgical intervention. The following plaque classification is based on the CT data: • Homogeneous (low density in comparison with the artery itself) • Heterogeneous (includes areas of low and high density) (Fig. 3.1) • Partly or totally calcified (contains calcium in the plaque structure) In terms of atherosclerotic lesion spreading (on the artery wall), all plaques are divided into local (length less than 1.5 cm) and prolonged (length exceeds 1.5 cm). In terms of location, there are local plaques (occupy part of the artery wall), semi-concentric plaques (occupy half of the artery wall perimeter) and concentric plaques (occupy more than half of the artery wall perimeter). In assessing plaques by the type of surface, one can detect plaques with a smooth surface and plaques with uneven surface, which contain ulcerations and haemorrhages.
3.1.3 Pathological Deformities and Abnormalities of the Epiaortic Arteries Among all cases of cerebral vascular insufficiency, not the least role is played by pathological deformations and congenital abnormalities of the epiaortic arteries. They account for about 12% of all ischaemic stroke cases. In 40% of all cases, the pathological deformation of the carotids coincides with
atherosclerotic lesions of the same artery, which significantly increases the risk of stroke in the area of that artery. The following types of pathological deformation are defined: • C- and S-shaped coiling (Figs. 3.2–3.5) • Artery twisted at a sharp angle (kinking) (Fig. 3.6) • Formation of pathological loops and spirals (coiling) (Fig. 3.7) • Combination of various types of deformations (Fig. 3.8) The main criteria for surgical treatment of pathological deformations in extracranial segments of cerebral arteries are the presence of clinical signs of brain disorder due to circulation dysfunction and the haemodynamic significance of deformation (maximum systolic velocity = 200 cm/s or more). Currently, numerous methods are being used in diagnosing of atherosclerotic changes in cervical and brain vessels. Important among the methods is digital cerebral angiography, which identifies of the degree and spread of vessel narrowing and revealing collateral blood flow (Wolpert 1992; Osborn 1999). It is necessary to mention the increased role of various noninvasive methods such as ultrasound Doppler, duplex scanning, and spiral and multispiral CT and MRA (Furst 1996; Shier et al. 1997; Callida 1999; Shakhnovich 2002). Ultrasound method. Transcranial Doppler reveals linear speed asymmetry of blood flow between intracranial magistral arteries in the case of stenosis, and it assesses collateral circulation reserves and their compensatory ability, and transcranial Doppler helps to detect microemboli in the area of intracranial arteries. Colour duplex scanning of the extracranial segments of carotid and vertebral arteries reveals of the presence of artery stenoses, estimating their degree and haemodynamic significance (Geroulakos 1996; Calliada 1999).
Cerebrovascular Diseases and Malformations of the Brain
89
Fig. 3.2a–c MRA of cervical arteries. Marked coiling with a twist of the right vertebral artery and hypoplasia of the left vertebral artery are
seen. 2D TOF regimen
Fig.3.3a–c Coiling of extracranial segment of the internal carotid artery. CT angiography [(CTA) a,b] and MRA (c)
with contrast enhancement (different patients)
90
Fig. 3.4a–i Coiling of vertebral arteries in the V1 segment. MRA (a)
with contrast enhancement, MIP reconstruction (b,c), MRA in 2D TOF regimen (d), and 3D reconstruction with application of “Navi-
Chapter 3
gator” algorithm (e,f). S-shaped coiling of initial segments of both vertebral arteries is seen. CTA (g–i) of another patient’s cervical arteries coiling combined with a twist of left vertebral artery ostium
Cerebrovascular Diseases and Malformations of the Brain
91
Fig. 3.5 Coiling of the right and the left common carotid arteries on DSI
Fig. 3.6a–c MRA with contrast enhancement of cervical arteries. MIP reconstruction (a–c). A marked twist is visualised within the ostium of the left vertebral artery
92
Chapter 3
Fig. 3.7a–c 2D TOF MRA of cerebral arteries. MIP reconstruction (a) and 3D reconstruction with application of “Navigator” algorithm (b,c)
of loop of the right internal carotid artery
Fig. 3.8a–c Combination of coiling and twist of the V1 segment of the left vertebral artery. MRA with contrast enhancement: MIP
reconstruction (a,b) and 3D (c) reconstruction (a view from behind) Fig. 3.9 Ultrasound duplex scanning at the level of bifurcation of the common carotid
artery. Stenosis of carotid artery lumen is seen
Cerebrovascular Diseases and Malformations of the Brain
93
Fig. 3.10a–c Thrombosis of cerebral arteries in different patients. Digital angiogram: thrombosis of internal carotid artery ostium (a,b) and
stenosis of supraclinoid segment of internal carotid artery (c)
Duplex scanning also assesses the plaque’s morphological structure (Fig. 3.9). Digital subtraction angiography. Direct infusion of the contrast into the artery is still considered the gold standard by many researchers in terms of diagnostics of different disorders of brain circulation system (Fig. 3.10). It is noteworthy that in the diagnosis of stenosis, cerebral angiography pursues three main goals: (1) to define the degree of stenosis, (2) to identify concomitant changes in blood vessels, and (3) to estimate current and (more importantly) the potential collateral circulation. The main indication for vascular surgery is a severe stenosis of more than 70% of initial vessel diameter. Taking that into consideration, the exact measurement of stenosis degree is an extremely important task. At least two projections are necessary for adequate estimation of stenosis degree. The percent of stenosis is calculated on a basis of comparison between vessel diameter at the site of stenosis and vessel diameter at the site located distally to the site of stenosis, with subsequent multiplication by 100. It is very important to distinguish the full occlusion from the so-called pseudoocclusion, as patients with the stenoses (even with very severe cases) remain candidates for thromboendarterectomy, unlike patients with full occlusion. In these cases, the modified procedure with prolonged imaging of a vessel and with slow contrast infusion is appropriate. CT and CT angiography. Unlike direct angiography, which adequately identifies only an internal part of the vessel, CT has bigger potential as an assessment of atherosclerotic lesions on the vessel wall. CT with contrast enhancement allows us not only to estimate the blood flow in the vessel, but, and what is especially important, also to visualise degenerative (atheromatous) changes of the vessel wall, and it distinguishes between calci-
fied plaques and non-calcified (“soft”) plaques. CT is highly sensitive, even to the minimal calcifications (Fig. 3.11). Spiral CT angiography has even greater potential. Use of thin slices (1 mm and less) in the examination of a large anatomic volume and single-stage bolus contrast infusion yields high-quality images of the main vessels after subsequent megaframe initialisation packet (MIP) processing (Link 1996). Thus, depending on the type of used program, it is possible to obtain the image of arteries only, or the simultaneous image of arteries and veins. The subsequent mathematical processing on a workstation raises the quality of vessel images, especially with use of 3D colour reconstruction of the vessel (Goddard 2001; Marcus et al. 1999). It also performs quantitative analysis of the site of stenosis (Figs. 3.12–3.14). One of the big advantages of CT angiography is the ability to examine a large anatomic volume, as the subsequent processing and 2D and 3D reconstruction of vessels provides a unique opportunity to reconstruct a vessel’s trajectory in the background of cervical vertebra or skull bones (Fig. 3.15). MRT. The estimation of vessel patency with the use of standard MR scanning modes can involve certain complexities, due to various factors. In standard Т1 and Т2 modes, normal vessels have a low MR signal that is caused by a so-called flow–void phenomenon. Presence of an iso- or hyperintense signal from an arterial vessel in these modes is suspicious with regard to thrombosis, stenosis or occlusion (Fig. 3.16). However, the slow blood flow in certain vessels’ segments (in the sites of widening or coiling) and the effect of “saturation” on extreme scans of T1-weighted imaging can lead to increase of the signal from vessels and hence can resemble vessel stenosis and partial thrombosis. Moreover, presence of typical effect of signal loss from a vessel on Т1- and Т2weighted imaging is still not the confirmation of the stenosis absence. Therefore, the appropriate MRI estimation of intra-
94
Chapter 3
Fig. 3.11a–c CTA of cervical arteries in patients with atherosclerosis of cerebral arteries. MIP reconstruction in axial (a), frontal (b), and sagittal (c) projections reveals small calcinated plaques in ostium of the left internal carotid artery and right vertebral artery (near bifurcation). Different patients
Fig. 3.12a–f CTA in patients with atherosclerosis of cerebral arteries. CTA of cervical arteries: MIP reconstruction (a,b), 3D reconstruction (c,d), and virtual endoscopy (e,f). In the ostium of the left
internal carotid artery, atherosclerotic plaque with heterogeneous structure with soft-tissue and calcinated components is visualised. The plaque causes marked stenosis of carotid arteries bilaterally
Cerebrovascular Diseases and Malformations of the Brain
95
Fig. 3.13a–c CTA in patient with atherosclerosis of cervical arteries: MIP reformation in coronal plane (a) and 3D reconstruction (b) and virtual endoscopy (c). Calcinated plaques are visualised in ostium of the internal carotid arteries
Fig. 3.14a–f Techniques for quantitative assessment of stenosis of an artery: MIP reconstruction in coronal projection (a) and calculation
of lumen square at the level of stenosis and above a plaque (b,c). Another example: calculation of maximal size and of lumen square at the level of stenosis (d–f)
96
Chapter 3 Fig. 3.15a,b CTA of cervical arteries. MIP (a) and 3D (b) re-
construction of vertebral artery trajectory at the level of cervical vertebrae
Fig. 3.16a–f Thrombosis of the left internal carotid artery: MRI in T2-weighted images (a–c) and FLAIR (d). Hyperintensity is seen within the internal carotid artery at the level of pyramid of temporal bone and sinus cavernosus. A small infarction is seen in the left basal ganglia on Т2- (e) and Т1- (f) weighted images
Cerebrovascular Diseases and Malformations of the Brain
97 Fig. 3.17a–c Thrombosis of the right internal carotid artery. Т2-weighted imaging (a) and 3D TOF MRA (b,c) demonstrate that (a typical image) the right internal carotid artery is absent. Blood supply of the right middle cerebral artery must proceed via the anterior communicating artery of the left internal carotid artery area
Fig. 3.18a–c Thrombosis of the left internal carotid artery. Т2-weighted imaging (a) and 3D TOF MRA, MIP reconstruction in axial (b) and
coronal (c) projections. A typical image—the left internal carotid artery is absent
and extracranial vessels should be performed with the use of special MRA software. MRA. Currently, several methods with the application of time-of-flight (TOF) and phase-contrast (PC) techniques are being used in MRA of cranial and cervical arteries. The use of the PC technique is limited by the required length of the examination and relatively smaller resolution in comparison with TOF. It is necessary to emphasise the use of different approaches and MR techniques in the imaging of cranial and cervical arteries. In order to maximise the visualisation of extracranial segment of carotid and vertebral arteries, it is preferable to scan in coronal and sagittal planes, because they have an advantage over the axial plane in maximising the visualisation of artery length. On the other hand, it is always necessary to remember that axial orientation of scans receives a higher signal from an artery and therefore achieves greater difference in signals between stationary tissue and moving blood. Considering the fact that the duration of vessel examination remains relatively long, it is preferable to maximise the visible
length of arteries, clarifying the image quality. In the imaging of cranial arteries, we prefer an axial orientation of scans, thus obtaining high-quality images of vessels, with enough capture of anatomical space. The different sets of techniques are used in an examination of cranial and extracranial arteries. In our institute, 3D TOF angiography is used mainly in examination of cranial segments of the carotid arteries (within the boundaries of a skull). The combination of magnetization transfer pulse sequences and saturation of MR signal from vein produces high-quality images of cerebral arteries in both hemispheres. A stenosis is visible in the form of local loss of signal from the vessel, with the restoration of an artery image distal to the site of stenosis. Occlusion leads to full disappearance of high MR signal from the vessel, then the absence of respective artery distally, and finally the site of occlusion (Figs. 3.17–3.19). As a rule, various ischaemic changes of the brain tissue— depending on the stage of ischaemia—are visualised in the area of occluded artery supply. In our opinion, the potential of the 3D TOF technique is limited by the low sensitivity of this
98
Chapter 3
Fig. 3.19a–c Thrombosis of the left vertebral artery. Т2-weighted imaging (a,b) and 3D TOF MRA (c) do not depict the left vertebral artery
in cervical region (arrow), and post-ischaemic changes are seen in the left cerebellar hemisphere. MRA demonstrates a small fragment of the left vertebral artery (arrow)
Fig. 3.20a–c Stenosis of ostium of the right internal carotid artery. 2D TOF MRA (a) and virtual endoscopy (b,c) reveal stenosis of the affected artery (arrows)
Fig. 3.21a–c MRA of cervical arteries, with contrast enhancement. MIP reconstruction (a): coronal projection. 3D reconstruction (b): cervical arteries branching from the arch of aorta (common branching of brachiocephalic trunk and the left internal carotid artery),
and their characteristics at cervical level (stenosis of distal segment of the left common carotid artery). Virtual endoscopy at the level of stenosis (c)
Cerebrovascular Diseases and Malformations of the Brain
99
Fig. 3.22a–f MRA of cervical arteries, with contrast enhancement (3D reconstruction). Forward (a) and backward (b) view and in different
angles (c–f). Coiling of the V1 segment of the left and hypoplasia of the right vertebral arteries
method to the visualisation of streams with low-velocity flow, for instance, at the site of stenosis. This can be the reason of overestimation of stenosis length and degree. 2D TOF angiography is used mainly for examination of extracranial segments of carotid and vertebral arteries from the arch of the aorta up to the point of their entry into the cranium. The capture of anatomical space with the use of this technique is greater than with the use of 3D TOF, which visualises the large segment of an artery in a short time (about 10–12 min). An obligatory condition is simultaneous use of saturation volumes for the suppression of the MR signal from the veins (Fig. 3.20). Although 2D TOF technique better visualises the lowvelocity blood flow than does the 3D TOF method, it nevertheless has many disadvantages that decrease the quality of blood flow estimation. In the case of severe stenosis due to out-phasing of spins, observed when the blood flow through the narrowed artery at the site of stenosis becomes turbulent and complex, this technique can overestimate the length of artery affected by stenosis. At the same time, our vast experience in MR diagnostics of epiaortic vessels stenoses revealed a high degree of correlation between data obtained from the
usage of 2D TOF method and from selective angiography. 3D MRA with the bolus infusion of contrast medium is a relatively new, minimally invasive method of cerebral vessel visualisation (Borisch et al. 2003; Roberge 2003; Alvarez-Linera et al. 2003; Lombardy and Bartolozzi 2004). It is still less used for cranial vessels examination, due to lower resolution than that of usual 3D TOF. The method uses high-speed impulse sequence based on the gradient-echo technique. With a large anatomical capture, the quick examination time of 30–60 s occurs during breath holding, thus preventing occurrence of artefacts from breathing and swallowing. MR contrast medium is administered intravenously at a rate of 4–5 ml/s. The usage of new, highly concentrated contrast medium (like Gadovist, with a concentration 1 mmol/ ml) decreases the quantity of infused solution for MRA of cervical vessels from 20 to 10 ml. The subsequent mathematical 2D or 3D postprocessing yields images in any projection and under any visual angle (Figs. 3.21–3.24). The main limitation of this program is insufficient visualisation of arteries with a low-velocity flow, for example, in
100
Chapter 3
Fig. 3.23a–d MRA without contrast enhancement of ostium of the internal carotid artery (a–c different patients) reveals stenosis of the initial artery segment. Thrombosis of the internal carotid artery: the small “stump” of the carotid artery with thrombosis is visualised (d)
Fig. 3.24a–f Thrombosis of ostium of the internal carotid artery. The first observation (a,b): occlusion of ostium of the right internal carotid artery (arrow); virtual endoscopy (c) confirms the complete
occlusion of the artery. Another case: thrombosis of ostium of the left internal carotid artery. 3D reconstruction (d,e) and virtual endoscopy (f)
Cerebrovascular Diseases and Malformations of the Brain
prolonged hypoplasia of the vertebral artery. It is possible to compensate this disadvantage by performing beforehand 2D TOF MR examination (Fig. 3.25). Comparison of the data obtained at complex examination obviates diagnostic mistakes (Lell 2007). As a whole, according to the opinion of the majority of researchers this method of MRA, especially in combination with CT angiography, can replace direct angiography of cervical vessels in case of suspicion of atherosclerotic narrowing of an artery.
3.2
Cerebral Ischaemia
The term stroke is widely used; however, it is not a precise term for a definition of the sudden beginning of neurological deficiency. Clinically, this condition is often called cerebrovascular accident. Stroke, or cerebrovascular accident, is a blood supply disturbance of the brain. A set of pathological conditions, including atherosclerosis, thrombosis, embolism, hypoperfusion, vasculitis and venous
Fig. 3.25a–f 2D TOF: MIP reconstruction (a) and bolus contrast enhancement MRA (b,c) illustrate stenosis of ostium of the left vertebral artery. 2D TOF regimen reveals that the length of stenosis is greater than was seen in a study with contrast enhancement. Another
101
stasis, can affect brain vessels and lead to a stroke. Neuroimaging methods always played the important role in stroke diagnosis; nevertheless, their main role was in excluding other brain pathology or in estimation of surgically accessible lesions. In clinical and diagnostic medicine development, stroke treatment has undergone certain changes, and now the main studies in this area are focused on early diagnostics of brain changes occurring just after blood circulation disruption and treatment strategies of the patient’s category based on obtained data. Wider use of the latest CT and MRI protocols, such as DWI/PWI in clinical practice, vastly expanded treatment options for already-occurred ischaemic changes. What is particularly important is that it became possible to prevent further development of brain damage resulting from the pathological chain of reaction, which starts after a critical decrease of brain perfusion. Frequently, cerebrovascular disease results from decrease or termination of blood supply, glucose and other metabolites
patient: 2D TOF (d) and bolus contrast enhancement MRA and 3D reconstruction (e,f). 2D TOF regimen visualises hypoplasia of the right vertebral artery better
102
Chapter 3
Fig. 3.26a–i Global cerebral ischaemia. Т2-weighted imaging (a–c), FLAIR (d–f), and Т1-weighted imaging (g–i) reveal areas of signal change
in periventricular regions in occipital and parietal lobes, and basal ganglia. Ventriculomegaly and foci of haemorrhagic transformation in basal ganglia are seen bilaterally (Т1-weighted image)
Cerebrovascular Diseases and Malformations of the Brain
103
Fig. 3.27a–f Global cerebral ischaemia. FLAIR (a–c), T1 (d) WI and MRAG (e,f). Post-ischemic changes in occipito-parietal regions and basal ganglia bilaterally along with astrophy and ventriculomegaly are seen
as well as from insufficient excretion of biological products. As an outcome, neural tissue cannot function properly under conditions of decreased blood flow. Another term synonymous with stroke is brain ischaemia. As a whole, brain ischaemia is divided into two main categories: global brain ischaemia, or ischaemia in which different regions of the brain are involved, can result in severe cardiac dysfunction, systemic arterial hypotension, or cardiac arrest (Figs. 3.26,–3.28); and local brain ischaemia, which results from limited disruption of brain circulation in the area of one artery (Fig. 3.29). The latter type of brain ischaemia occurs more often, and this chapter is dedicated to it. Three main aetiological reasons lay at the foundation of stroke symptoms: brain infarction, cerebral haemorrhage and subarachnoid haemorrhage. In clinical practice, the most common is an ischaemic infarction developing due to inadequate blood flow in certain vascular area. It is necessary to note that a good deal of literature is dedicated to the problem of stroke both in Russia and abroad. The process of understanding of pathophysiological changes
occurring during the stroke underwent substantial modifications. During the past several years, much new data concerning stroke diagnostic as well as treatment have been obtained. Nevertheless, the foundations of the stroke theory were outlined at the end of past century by the work of Russian scientists such as N.K. Bogolepov (1971), I.V. Gannushkina (1973, 1975), E.V. Shmidt (1976), E.I. Gusev (1979) and N.V. Vereshchagin (1986).
3.2.1 Pathophysiology of Cerebral Ischaemia A clear understanding of pathophysiological reactions developing in the background of critical cerebral blood flow reduction is an important point of any diagnostics of ischaemic cerebral insult, correct interpretation of the obtained data and correct assessment of diagnostic changes on CT and MR images of the affected brain in the course of the ischaemic process.
104
Chapter 3
Fig. 3.28a–f Global cerebral ischaemia. Т2-weighted (a), FLAIR (b,c), Т1-weighted (d) images and DWI (e). Post-ischaemic changes in frontoparietal-temporal regions with haemorrhagic transformation in basal ganglia bilaterally. МR spectroscopy reveals marked decrease of the NAA peak, and a two-humped lipid–lactate peak appeared (f)
Fig. 3.29a–c Ischaemia in the right middle cerebral artery area. Т2-weighted (a), Т1-weighted (b) images and DWI (c) clearly demonstrate the area of signal change in the right temporal region
Cerebrovascular Diseases and Malformations of the Brain
The consequences of acute focal ischaemia and degree of its damaging influence crucially depend on the severity and duration of such blood flow decrease. Experiments with biological models demonstrated that neuronal electrical activity loss happens within seconds after arterial occlusion (Garcia 1983). In general, loss of function of the affected site of a brain develops when the brain blood flow decreases to a level of 15–20 ml/100 g/min (Mies 1991; Hossmann 1994). A brief picture of the experimentally established cascade of the metabolic reactions occurring in brain tissue as a result of blood flow decrease is presented in the Table 3.1. Blood flow decrease to 70–80% of normal levels (below 50 ml/100 g per minute) is accompanied by the reaction of albumin synthesis inhibition (Hossmann 1994). This level is considered the first critical level of a cerebral ischaemia. Further blood flow decrease to 50% of normal levels (approximately 35 ml/100 g/min) leads to anaerobic glycolysis activation and increased lactate concentration, development of lactic acidosis and cytotoxic oedema. Progressive brain ischaemia and further blood flow decrease (to 20 ml/100 g/ min) is accompanied by decrease of ATP synthesis, development of energy insufficiency, destabilization of cellular membranes, the release of amino acidergic transmitters, and by the function impairment of the active ion transport canals. Blood flow decrease below the critical level of 10 ml/100 g/min leads to cell membrane depolarization, currently considered the main criterion of irreversible cell damage (Hossmann 1994). In addition, it is necessary to note that blood flow decrease in an ischaemic area has heterogeneous character. The heterogeneity has been clearly proved in experimental as well as in clinical studies. The central ischaemic core has the lowest perfusion, which leads to prompt (within several minutes) cell death. The peripheral ischaemic area retains higher perfusion level, and irreversible cell changes develop for a period more prolonged. This peripheral ischaemic but alive area is called the area of penumbra (Astrup et al. 1981; Fisher and Garcia 1996). This area retains energy metabolism, and it has only functional changes. Further development of ischaemia leads to exhausting of local perfusion reserve (for instance, in the case of inadequate treatment or orthostatic hypotension), and neurons become highly sensitive to any further blood flow de-
105
Fig. 3.30 Schematic representation of temporal lobe infarction components after thrombosis of the middle cerebral artery. Arrows show areas of irreversible changes (core of infarction) and area of ischaemic penumbra
crease; the core can undergo irreversible structural changes because of this. The ischaemic core expands at the expense of the penumbra’s continuing necrosis. The penumbra, however, can be salvaged by blood flow restoration and use of neuroprotective agents. The penumbra is a main target for early diagnostics with the use of modern neuroradiological methods and early treatment (Fig. 3.30).
Table 3.1 Brain tissue reactions to blood flow decrease
a
Local blood flow (ml/100 g/min)
Brain tissue reactions
55–80a
Normal state
Below 50–55 (the first critical level)
Albumin synthesis inhibition Selective genes expression
Down to 35 (50% decrease; the second critical level)
Anaerobic glycolysis activation. Increase lactate, cytotoxic oedema
Down to 20 (the third critical level)
Energy deficiency (decrease ATP synthesis)
10–15
Anoxic membrane depolarization, cell death
Normal blood flow limits vary, depending on examination time and location of sites where measurement is taking place (in the same person) from 45 to 110 ml/100 g/min. (Astrup et al. 1981; Obrenovitch 1995; Ueda et al. 1999)
106
3.2.1.1
Chapter 3
Pathology
Macroscopic brain examination in the acute phase of ischaemia might not reveal any pathological changes. However, microscopic examination can detect neuronal changes like mitochondrial swelling and disorganization (neurons are more sensitive to ischaemia than are astrocytes and oligodendroglia) that are visible 20 min after ischaemia onset. Such changes can be the sole mark of ischaemia during the first 6 h. Then, microscopic examination reveals neuronal corrugation cytoplasmic eosinophilia, ribosomal aggregation and synaptic “encrustation”. Macroscopic changes become visible after 6 h from ischaemia onset. The time of maximum expression of focal brain oedema, which represents cytotoxic oedema, is the interval between 24 and 48 h; this leads to brain gyri thickening and to the blurring of boundaries between grey and white matter. The duration of acute ischaemia is the first 2 days. Then, subacute infarction phase starts. During this phase, the processes of further brain thickening and softening unfold. This period lasts 7–10 days (after stroke onset). Brain oedema in the ischaemic area is maximally expressed at 3–5 days after stroke onset. At this stage, vasogenic and cytotoxic brain oedema take place. At this time, the reparation processes are active. Microglia cells, neutrophiles and macrophages begin to phagocytise necrotic tissue. This process leads to cystic cavity formation. Reparation processes are more actively unfolding at the peripheral infarction area. The chronic phase can extend to several weeks or even months. In this period, damaged necrotic tissue is resorbed with the formation of the areas of encephalomalacia, surrounded by gliosis of adjacent brain tissue. The wrinkled gyri and the dilatation of adjacent parts of ventricular system can be found in cases of relatively large infarction areas. The above-mentioned pathological changes appear in almost any type of infarction; however, the specific condition of the damaged tissue site varies, depending on the location, size and cause of the ischaemia.
3.2.1.2
Epidemiology
During the past decade, statistical observations revealed the considerable growth of the morbidity of cardiovascular diseases, which in turn translated into the increased number of stroke cases and cases of chronic brain circulation disorders. Annually, about 6 million people worldwide suffer from stroke, and about 450,000 suffer from stroke in Russia. This means that every 1.5 min, someone in Russia develops stroke symptoms for first time (Gusev and Skvortsova 2001; Gusev et al. 2003). The same data on frequency of new stroke cases are reported for the United States population, and it was mentioned that 80% of all these cases are ischaemic stroke as opposed to haemorrhagic stroke (which accounts for the remaining 20%). According to data of the joint studies that were conducted in the United States and Europe, ischaemic stroke morbidity is
about 130–200 cases in a year per 100,000; however, it reaches 550 cases per 100,000 in seniors (64–75 years old). It is necessary to note that according to the international epidemiological studies, 4.7 million people die annually from stroke. In the majority of countries, including the United States and Europe, stroke is the second or third leading cause of death. In Russia, this disease occupies second place, after cardiovascular disease. Stroke mortality at 30 days is close to 35%, and in the course of a year, 50% of stroke patients die— every second one (Gusev and Skvortsova 2001). Stroke is the main cause of disability, and the increase of stroke morbidity is observed in persons of working age (<64 years of age) Among the patients who survived the acute stroke phase only, 10–20% return to their jobs, and the others become disabled with visible neurological deficit. Heavy financial burdens can fall on the shoulders of stroke patients and their families. It is necessary to note that throughout the world, huge sums are spent annually for treatment and rehabilitation of stroke patients. According to World Health Organisation (WHO) data, the average expenditure for diagnostics, treatment, and rehabilitation of one stroke patient is about US $55,000–73,000 per year. In the United States, the annual expenditures amount to US $7.5–11.2 million. The most common cause of stroke is stenosis and occlusion of carotid and vertebral arteries (Vereshchagin et al. 2002). The frequency of carotid arteries lesions exceeds 20% of the frequency of posterior circulation area involvement. Atherosclerosis affects extracranial arteries four times more often than it does cranial arteries. The vast majority of studies dedicated to the aetiology of stroke demonstrated that about 50% of ischaemic strokes result from thromboembolism due to atherosclerosis of big and middle-sized arteries. About 25% of all cases are related to the pathology of small cerebral arteries, roughly 20% are linked to cardiac embolism, and only 5% of all stroke occurs due to other, more rare reasons (for instance, haemodynamic stroke related to myocardial infarction, vasculopathy, injury, dissecting aneurysm, blood diseases, infections or drug intoxication).
3.2.1.3
Clinical Signs of Cerebral Ischaemia
Despite the presence of universal patterns in the course of ischaemic stroke, clinical manifestations are individual in each patient, and these depends on many factors including pre-stroke condition of brain metabolism, reactivity of various neurohumoral systems, anatomical variants of circulation (presence of collateral circulation reserve) and many others (Vereshchagin et al. 2003). As a whole, the clinical picture of a cerebral ischaemia can be divided into the following types of clinical manifestation: • Asymptomatic course of disease. • Chronic cerebral ischaemia with the presence of clinical manifestation of chronic ischaemic brain disease, without the presence of neurological focal signs. • Transitory ischaemic attack (TIA) or transient brain circulation disruption. This is a clinical syndrome characterised by the acute development of neurological focal signs that
Cerebrovascular Diseases and Malformations of the Brain
appears because of acute disruption of cerebral perfusion, with full recovery within 24 h. • Ischaemic infarction, which is a clinical syndrome characterised by the acute development of neurological focal signs and loss of consciousness up to coma, with the persistence of these symptoms for more than 24 h, or it leads to death without other evident reasons except the vascular pathology. Stroke is divided into:
• Minor stroke, a clinical neurological syndrome resulting
from acute brain circulation disruption. This type manifests in a form of neurological focal and general cerebral signs, with the recovery of disturbed function within 2–4 weeks. • Stroke with persistent neurological focal signs and general brain signs, which persists without visible recovery. According to its clinical course, stroke is divided into: • Stroke with progressive clinical course, in which the acute phase of the ischaemia is accompanied by neurological focal signs and general brain signs. • Completed stroke, the final phase of ischaemic stroke development. Clinical manifestations of stroke in the carotid artery area are variants of motor and sensitive disorders in upper and lower extremities, dysarthria, aphasia, visual impairment, etc. If stroke affects the posterior circulation area, then the main clinical manifestations are cerebellar signs in the form of dizziness, often with nausea and vomiting, and gait and coordination disorders. In the case of brainstem stroke, signs and symptoms include various types of nystagmus, motor, and sensitive disorders in upper and lower extremities, cranial nerves palsies and various types of visual impairment (if the stroke affects occipital lobe). Depending on the severity of chronic brain ischaemia, cerebrovascular pathology is categorised into the following stages: 1. Stage of compensation. This stage is represented by periodic TIA on the background of general indications of chronic ischaemic brain disease. 2. Stage of subcompensation. Frequent TIA occurs during this stage, complicated by minor strokes. 3. Stage of decompensation. This stage can have three main variants of clinical course: a. Severe encephalopathy with the prevalence of mental disorders b. Severe pyramidal and extrapyramidal disorders, with the minimal mental disorders c. Severe mental disorders in combination with focal neurological signs
3.2.1.4
Pathogenetic Subtypes of Ischaemic Stroke
Currently, there are several different ischaemic stroke classifications. As an example, we present the classification de-
107
veloped at the Scientific Research Institute of Neurology of the Russian Academy of Medical Science (Vereshchagin et al. 2002; Suslina 2002).
3.2.1.4.1 Atherothrombotic Stroke This type of stroke is characterised by being multigraded, beginning with the gradual increase of clinical manifestations in the course of hours or days. Often it begins during sleep. It is characterised by the presence of atherosclerotic lesions in extra- and/or cranial arteries on the side of the stroke. TIA often precedes stroke onset. The stroke size varies from small to large. Atherothrombotic stroke together with of the artery– artery embolism constitutes about 47% of all stroke cases.
3.2.1.4.2 Stroke Due to Cardiac Embolism Characterised by an acute beginning, this stroke, as a rule, affects patients in the wakened state. The focal neurological signs are most visible at the beginning of the disease. The most frequent location is the area of the middle carotid artery, usually cortical–subcortical, and of medium or large size. According to CT data, a haemorrhage component is typical for this stroke type. The history of multiple “silent” cortical strokes is present, heart pathology (the source of embolism) or thromboembolism of other organs. Usually, severe atherosclerosis of the appropriate vessel is absent. This type of stroke accounts for 22% of all cases.
3.2.1.4.3 Haemodynamic Stroke This form of stroke is characterised by acute onset. The most frequent sites are areas of boundary blood supply (including cortex strokes in periventricular areas and white matter of the semi-oval centres). The size may vary from large to small. The pathology of extra- and cranial arteries (atherosclerosis, deformations, vessel’s abnormalities, dissociations and hypoplasia) is typical for this type of stroke. A haemodynamic component is also present in the form of sudden drop of blood pressure and cardiac output. Haemodynamic stroke accounts for less than 15% of all strokes.
3.2.1.4.4 Lacunar Infarction Lacunar infarction is a “microstroke”, with a size up to 1–1.5 cm. As a rule, arterial hypertension precedes stroke. It is characterised by an intermittent beginning; the most frequent locations are subcortical nuclei, the brainstem, internal capsule and surrounding white matter of the semi-oval centres. There are typical focal neurological signs, and in some cases just one symptom is present (motor, sensitive), with absence of general brain signs. Lacunar stroke accounts for 20% of all cases.
108
Chapter 3
Fig. 3.31a–f Ischaemic infarction in the right basal ganglia. CT of the acute phase: day 2 (a–c), day 20 (d–f). Smoothened borders of globus
pallidus and putamen rightwards are seen. The follow-up CT demonstrates the area of formed infarction within the putamen, external capsule and a part of caudate nucleus head (hypodense area)
Fig. 3.32a–c Acute ischaemia in the left middle cerebral artery area due to thrombosis. CT images (a,b) of the acute phase show a hypodense
area within in the insular cortex of the temporal lobe. Arrows show “phenomenon of the middle cerebral artery”. MRA confirms the absence of blood flow in the left middle cerebral artery (c)
Cerebrovascular Diseases and Malformations of the Brain
3.2.1.4.5 Stroke Due to Haemorheological Micro-Occlusion Severe haemorheological disorders, haemostasis, and fibrinolysis abnormalities with the absence of vessel’s lesions (atherosclerosis, etc.), and haematological pathology (coagulopathy, erythraemia), are main features of this type of stroke. In addition, depending on the main aetiological reason, strokes are divided into strokes involving microangiopathy in vessels and microangiopathy. The first group includes stroke on the defined arterial area (thromboembolism), and strokes in the so-called marginal zone and in the area of “watershed” (cortex–subcortex area). The main components of this stroke are haemodynamic changes in the arteries located far from the site of stenosis/occlusion. Deep lacunar strokes and subcortical atherosclerotic encephalopathy due to pathology of the small perforating arteries belong to the second group.
3.2.2 Diagnosis CT and MRI changes through the course of a stroke are traditionally divided into three stages: acute, subacute and chronic. There are some inconsistencies between them and pathological changes in the brain tissue. However, in general, changes diagnosed with the use of CT and MRI are similar to the main macroscopic changes; the latter has the same character, and their development in the course of disease corresponds with the three main stages mentioned above.
3.2.2.1
Superacute and Acute Stages of Stroke
Usually cerebral selective angiography, with the exception of cases with local thrombolysis, is not used in the diagnostics of the acute stroke stage. Artery occlusion is the most frequent finding in the examinations performed within the first hours after the stroke onset (in up to 50% of cases) (Horowitz 1991). In these cases, the delays of contrast washout from the artery below the occlusion and the absence of corresponding circulation net are seen. In addition, among other findings in the first hours after stroke onset the visualisation of the collateral circulation through small cortex arteries to the ischaemic area and venous-arterial shunting to the cortical veins (luxury perfusion syndrome) are observed. CT plays a far more significant role in stroke diagnostics than does MRI, because the majority of stroke patients are being admitted to intensive care units of the multifield hospitals, where it is easier to conduct a CT scan than MRI. Although the standard CT examination detects acute ischaemic changes, the main task of such examinations is to rule out cranial haemorrhage and other brain pathology (like tumours, malformation and haemorrhage, all of which can have the same clinical manifestations as ischaemic stroke). The acute stroke phase has a certain time limit (up to 2 days). The CT potential depends on the amount of time passed since stroke onset. During the first hours, standard, without-con-
109
trast CT displays a normal brain picture in more than 50% of cases. The first pathological signs that are visible in the first 12 h after stroke onset are increased density along the affected artery (such a hyperdensity more often is visualised in the branches of middle cerebral artery, or MCA, the so-called MCA symptom or phenomenon), the blurring of the boundaries of lentiform nuclei, the absence of the subarachnoid fissures and blurring of the boundaries between grey and white matters (Figs. 3.31, 3.32). Hyperdensity of MCA is a sign of thrombosis. This symptom is observed in up to 25% of cases of ischaemic stroke and in up to 50% in patients with stroke in the MCA area (Tomsick 1992). Within the first 24 h, the process of ischaemic area demarcation takes place. The ischaemic area becomes hypodense in comparison with the surrounding tissues (Fig. 3.33). The hypodensity is seen during the first 3 days, and the hypodense area expands into white as well as grey matter. In the case of a large stroke, at the end of acute phase, perifocal oedema develops, and a mass effect on the surrounding tissues and ventricles forms (Figs. 3.34, 3.35). CT with the contrast enhancement does not detect areas of contrast medium accumulation. Arterial vessels of the affected area, especially small, often seem more dense than those on the opposite side of the head. The use of CT angiography and CT perfusion is more informative. CT angiography with subsequent reconstruction visualises the site of occlusion because the distal segment of vessel (below occlusion) is free of contrast (Shier et al. 1997). However, this method is more useful in the examination of large, especially extracranial vessels. The potential of contemporary CT models in the blood flow estimation of small arteries (for instance, thalamoperforating arteries in case of subcortical stroke) is limited. However, the best method of early visualisation of circulation disruption is CT perfusion. This method is based on the estimation of the contrast bolus passage through microcirculation of the vessel’s net and building the digital maps based on the obtained data. With the help of these maps, it is possible to evaluate the CBV and regional cerebral blood flow. The sensitivity of CT perfusion is very high, even when the examination is conducted within the first minutes (and hours). In these moments, it is possible to detect a significant decrease of the blood flow in the affected brain area (Fig. 3.36). At the same time, it is possible to calculate the quantitative indicators of brain perfusion. This may play an important role in treatment selection and patient management. Numerous researchers demonstrated that this method is more sensitive in the first hours after stroke onset than even MRI perfusion. The main limitation of modern CT tomographs is the small number of the examined levels; however, the invention of multispiral devices (these devices can simultaneously obtain 16 and more slices) made CT perfusion the method of choice of CBF assessment. In the acute phase of an ischaemic stroke, the pathological signs of brain disorder can be better detected with the use of MRI (the sole exception is CT perfusion). The area of increased MR signal is visualised on T2-weighted images and in
110
Chapter 3
Fig. 3.33a–c Acute ischaemia (24 h after onset) in the left middle cerebral artery area. CТ (a–c) without contrast enhancement: a hypodense
area and enlargement of the left temporal lobe, compression of Sylvian fissure and subarachnoid spaces in the sited location
Fig. 3.34a–c Infarction in the left middle cerebral artery area (day 3).
CT without (a,b), and after contrast enhancement (c) demonstrates a hypodense within the insula of left temporal lobe with involvement
of basal ganglia. Dislocation and compression of ventricular system and subarachnoid spaces of temporal region are seen. Infarction area does not show contrast enhancement
Cerebrovascular Diseases and Malformations of the Brain
111
Fig. 3.35a–c Ischaemic infarction in the middle cerebral artery area. CT (day 1) does not reveal focal changes in brain tissue density (a,b).
Colloid hyperdense microcyst is seen near the foramina of Monroe. Three days later CT reveals the hypodense area with mass effect on the adjacent lateral ventricle (c)
FLAIR mode even in the first 24 h (however, not earlier than 8 h). This area spreads in accordance with the area of the affected artery and usually covers grey matter (Fig. 3.37). The above-mentioned changes are observed in 80% of all cases. However, standard MRI does not detect any changes in the superacute phase. The absence of typical MRI images of main vessels that normally have low signal (more information can be obtained with the use of T2-weighted imaging) is suspicious and can point to occlusion. Such a situation requires conducting additional examinations (including MRA and intravenous contrast medium administration). MRA with the use of 3D TOF technique visualises the occlusion site in cases of presence of artery breaks on the MIP reconstructed images (Fig. 3.38). T1 mode with use of intravenous contrast injection allows observation of increased MR signal from affected arteries; such a phenomenon can be never observed in normal arteries (the arteries are always hypointense). The latter changes may be visualised within the first minutes and hours after stroke onset. In the acute phase with further stoke progression, the signs of brain swelling start to appear. They are detected with the help of T1 mode (the thickening of gyri, the compression of subarachnoid space, etc). Within the first day, contrast enhancement of the meningeal membranes in the areas surrounding the infarction zone is observed. The mass effect on the brain structures and ventricular system appears and quickly progresses in cases in which the affected area is large. However, it should be remembered that standard MRI does not detect any structural changes in the acute stroke phase in 10–20% of all cases. DWI revolutionised MR assessment of early stroke phases. Based on the detection of microscopic movement of water
molecules, DWI is extremely sensitive to minimal changes of movement and minimal increases of water concentration in the brain tissue. Cytotoxic oedema developing in the acute phase leads to cell swelling, diminishing of the extracellular space and severe limitation of water molecule movement within cells and outside them. Water concentration in the affected area increases (3–5%). All these developments lead to sharp DWI signal increase from the affected area in comparison with other brain areas. The diffusion coefficient in the acute ischaemic area is sharply decreased, which translates on the colour map as an area with dark colour compared with rest of the brain. It is widely belived that DWI depicts sees changes within first hour after stroke onset (Warach et al. 1995). However, in some studies the DWI does not reveal typical stroke changes of the MR signal during the first 2–3 h; perfusion examinations favour the ischaemia presence. Repeated DWI after 6 h reveals cytotoxic oedema area in all cases (Lefkowitz et al. 1999; Wang 1999). In our observations, the earliest use of DWI in diagnostics of brain ischaemia was examination conducted after 3 h since embolism of the posterior circulation area. These images, contrary to routine T1 and T2 MRI (which displayed a normal picture), revealed multiple sites of increased signal. Follow-up DWI allows assessment of the character and the severity of the clinical course of stroke as well as a response to treatment (Figs. 3.39, 3.40). Another very important DWI advantage is clear and precise—even in comparison with FLAIR—visualisation of small deep and multiple cortical–subcortical strokes (Fig. 3.41).
112
Fig. 3.36a–i Ischaemia in the right middle cerebral artery area (acute
phase, day 1). Т2-weighted imaging (a,b) demonstrates lacunar (old) infarction in the right putamen; other changes are absent. 3D TOF MRA (c) reveals thrombosis of ostium of the middle cerebral artery. CT without contrast enhancement (d) also shows lacunar infarction.
Chapter 3
CT perfusion: “raw” data (e,f) and colour digital map calculation (h,i) demonstrate the area of changed blood flow in the right temporooccipital region (arrows). Graphic image (g) of cerebral blood flow change with decreased parameters in the ischaemic area (curve 3)
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.37a–c Acute ischaemia in the right half of genu corpus callosum (24 h after ischaemic attack). Т2-weighted (a) and Т1-weighted (b) images and DWI (c) demonstrate a focus of signal change. Mild dislocation and compression of anterior horn of the right lateral ven-
113
tricle is seen. Old lacunar infarction is seen in the right external capsule. Diffusion study (c) reveals a characteristic high signal, which rules out a tumour
Fig. 3.38a–c Thrombosis of the right middle cerebral artery. 3D TOF MRA: MIP reconstruction in axial (a) and coronal projections (b) and 3D reconstruction (c) demonstrate that the middle cerebral artery is not visualised in any segment of its total length
Currently, the most widespread spectroscopy method employed in a clinical practice is 1H MRS. The potential of this method in the early diagnosis of the ischaemic stroke is being actively studied. It is possible to observe a Lac peak of a different intensity in the spectrum of the affected brain area. Such peaks are not visible in the spectrum of normal brain tissue (Fig. 3.42). Moreover, in the ischaemic area, the decrease of peaks of main brain metabolites like NAA, Cho and Cr are observed (Barker et al. 1994; Podoprigora 2003). In addition, although proton spectroscopy reveals the ischaemic changes earlier than routine MRI does, its main limitations are the small volume of the area of interest and the relatively long length of the examination, especially taking into consideration the severe state of many patients.
These limitations do not allow adequate assessment of various sites in the affected area (ischaemic core, penumbra). Perhaps the introduction of multivoxel and multinuclear MR spectroscopy into clinical practice can amend the situation and improve this method’s effectiveness in stroke diagnostics and study. Perfusion MRI as well as perfusion CT is based on the estimation of the contrast medium bolus passage through microcirculation of a vessel’s net. Also, perfusion MRI estimates parameters of the regional blood flow (rCBV, rCBF, MTT); however, unlike CT methods, perfusion MRI deals with relative blood flow indicators in comparison with the unaffected side.
114
7 Fig. 3.39a–u A follow-up observation of ischaemic infarction in the left middle cerebral artery area. Т2-weighted (a,b) and Т1-weighted (c,d) images, performed 3 h after ischaemic attack, reveal only the marked enlargement of subarachnoid spaces and weakly outlined borders of the left putamen. On DWI at the same levels (e,f) a hyperintense area in the posterior part of the left frontotemporal region with involvement of putamen and cortical areas of frontotemporal regions are seen. 3D TOF MRA (g) and 3D PC (h) do not depict the middle cerebral. Twenty-four hours later, hyperintensity is detected in Т2-weighted imaging (i,j) and hypointensity in (k,l)
Chapter 3
Т1-weighted imaging in the area of ischaemic infarction. On DWI (m,n), the hyperintense area acquired more clear-cut borders. The follow-up study on day 3 signal changes increased in T2-weighted imaging (o–r) and on DWI (s,t). The area of ischaemia expanded onto the head of caudate nucleus and frontal cortex, and a haemorrhagic component appeared within putamen and globus pallidus, hypointense on T2-weighted imaging and DWI (arrow). 3D TOF MRA demonstrates that the image of the left middle cerebral artery area was restored (u)
Cerebrovascular Diseases and Malformations of the Brain
115
116
Chapter 3
Cerebrovascular Diseases and Malformations of the Brain
9 Fig. 3.40a–o A follow-up observation of ischaemic infarction in cerebellum. Т2- (a) and Т1- (b) weighted images at the level of posterior fossa done 4 h after the ischaemic attack reveals smoothening of cerebellar gyri without focal changes. On DWI (c), there is a large area of hyperintensity in the left cerebellar hemisphere along with small focal changes in the right one. Twenty-eight hours later hyperintensity is seen on Т2-weighted imaging (d) and hypointensity on T1-weighted imaging (e), which correspond to DWI changes (f). On day 8, the area of signal change became enlarged on Т2-weighted
117
imaging (g) with increased heterogeneity on Т1-weighted imaging (h) and DWI (i). On day 15, the area of signal change decreased on Т2-weighted imaging (j) and foci of haemorrhagic transformation appeared in both cerebellar hemispheres on Т1 (k). On DWI (l), decreased signal intensity is seen in the infarction area in the left cerebellar hemisphere. On a series of MRI performed 3 months later on T2-weighted imaging (m) and DWI (n b = 500, o b = 1,000) further decrease of signal intensity in the area of infarction and formation of the area of encephalomalacia are seen
118
Chapter 3
Fig. 3.41a–c Ischaemic infarction of cortical and subcortical location rightwards (day 3). On a series of Т2-weighted imaging (a), FLAIR (b), and DWI (c b = 500), a hyperintense area is seen in the right temporal region, better visualised on FLAIR and DWI
Cerebrovascular Diseases and Malformations of the Brain
119
Fig. 3.42a–c Acute ischaemia in the left middle cerebral artery area. Т2-weighted imaging (a) demonstrates the area of signal change corresponding to infarction. A quadrant outlines the site at which MR spectroscopy was performed. MRS acquired on days 2 and 9 after
ischaemia (b,c). In the acute stage, there is a marked decrease of the NAA peak on the background of a two-humped lactate peak. MRS on day 9 revealed that the NAA peak increased and the lactate peak decreased, which correlated with clinical improvement
According to the data of different studies, MR perfusion is one of the most informative methods, especially during the superacute and acute stages (Figs. 3.43–3.45). The area of decreased flow is clearly visible on the colour perfusion maps, and indicators of perfusion change depending on point of measurement from centre towards the periphery. It is necessary to mention that despite the above-mentioned limitation (in comparison with the CT), this method is more informative: the capture area of the MR perfusion is significantly larger than those of CT, and this carries out blood flow assessment on multiple levels. An important point in studying the dynamics acute in the brain tissue is comparison between perfusion data and those of DWI. It was found that in superacute stage (less than 6 h), the affected area according to DWI methods is far less than those assessed by perfusion (Provenzale et al. 2000). Such a mismatch was observed in about 70–80% of patients. In addition, the majority of studies have emphasised that in patients with such difference, the area of increased signal on DWI later expands into the hypoperfused areas (Barber et al. 1998). It is necessary to note that DWI signal changes typical for cytotoxic oedema are not indicators of irreversible changes (Fig. 3.46–3.48). Patients who underwent early arterial thrombolysis with the subsequent restoration of the perfusion in the affected area have good clinical recovery, and the area of final changes of the DWI signal was far less than the initial one was (Kidwell et al. 2000).
3.2.2.2
Subacute Phase of Ischaemia
Brain ischaemia is a dynamic process. CT and MR images undergo certain changes over the course of disease. In the case of stroke caused by blood flow disruption of large arteries, CT identifies the demarcation of decreaseddensity areas that expand into the white as well as grey matter of the appropriate arterial area (Figs. 3.49, 3.50). The mass effect, growing during the first 3 days, gradually regresses at the end of the subacute stage. In 15–20% of cases, the signs of haemorrhage are visible on the without-contrast CT images performed during the subacute stage. Such signs are visualised in the form of local areas of increased density primary located in basal ganglia and alongside the gyri (Fig. 3.51). In most cases, the haemorrhagic transformation is observed within the first 4–6 days. Considering the fact that by this time, in the course of ischaemia development, the structural integrity of the blood–brain barrier is broken, it is possible to visualise the pathological contrast enhancement of focal character as well as such enhancement along the brain gyri (Fig. 3.52). The first foci of contrast enhancement in the affected area can be visible 3–4 days after stroke onset, and they remain over a relatively long period, up to 8–10 weeks. MRI reflects the severity of brain oedema in the subacute phase. The ischaemic area is characterised by the increase of MR signal on the T2 and FLAIR images. The affect on white and grey matter is clearly visible in the appropriate circulation area. This area has hypointense signal on T1-weighted imaging (Figs. 3.53–3.55). The subarachnoid space is compressed. The affected brain gyri are thickened. The meningeal and intravessel contrast enhancement visible within the first 3 days signifi-
120
Chapter 3
Cerebrovascular Diseases and Malformations of the Brain
9 Fig. 3.43a–o Ischaemic infarction of the right cerebellar hemisphere. DWI on day 1 at the level of posterior fossa (a–c) and on Т2-weighted imaging (d) reveal a large hyperintense area. MR perfusion with rCBF (e) and МТТ (f) maps calculation revealed that perfusion parameters are decreased, and the time of contrast transition is increased in the area of infarction (arrow)—the light area in the right cerebellar hemisphere. A follow-up MRI on day 7: clinical improvement was observed and MR signal decreased on DWI (g–i)
121
and on Т2-weighted imaging (j) in the right cerebellar hemisphere. MR perfusion with rCBF maps (k,l) demonstrate the restoration of perfusion in the affected cerebellum. MRI on day 20 on Т2-weighted imaging (m) and DWI (o) reveal the restoration of signal intensity in the right cerebellar hemisphere. On Т1-weighted imaging (n), small foci of haemorrhagic transformation in the residual areas of infarction are revealed (arrows)
122
Chapter 3
Cerebrovascular Diseases and Malformations of the Brain
9 Fig. 3.44a–o A follow-up observation of ischaemic infarction in the left basal ganglia and temporal lobe. Т2-weighted imaging (a) and DWI (b–d), performed by the end of day 1, demonstrate the hyperintense area within the left putamen and head of caudate nucleus, better visualised on DWI. MR perfusion with rCBF (e) and МТТ (f) maps calculation reveals the area of changed blood flow in the left temporal region (arrows), better visualised on МТТ map. On day 7 there was no clinical improvement, and MRI revealed expansion of
123
MR signal change in the left basal ganglia, detected on Т2-weighted imaging (g) as well as on DWI (h–j). МR perfusion with rCBF (k) and МТТ (l) demonstrate preservation of the area of changed blood flow in the left temporal lobe. On day 20 after the stroke, Т2-weighted imaging (m), Т1-weighted imaging (n) and DWI (o) reveal haemorrhagic transformation in the area of infarction with formation of focal encephalomalacia
124
Fig. 3.45a–f Acute ischaemia in the area of terminal branches of the left middle cerebral artery 12 h after onset. Т2-weighted imaging (a) and DWI (b) reveal the areas of signal change in the left parietal lobe (arrows). Diffusion imaging depicts the volume of lesion better. MR
Chapter 3
perfusion with rCBF (c), TP (d) and МТТ (e) maps calculation reveal a large area where blood flow parameters are changed (arrows). Graphic representation (f) of perfusion parameters in the pathological area (3) and on the opposite side (2)
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.46a–f Acute ischaemia in the left middle cerebral artery area. DWI (a) reveals the hyperintense area in the posterior frontal and temporal region leftwards. Putamen and globus pallidus are involved. ADC map (b) demonstrates the area with low parameters of diffu-
125
sion represented by darker colour (arrow). CT perfusion (c), CBF (d), МТТ (e) and TP (f) maps show that changes in blood flow are heterogeneous with formation lesion of putamen (arrow). DWI and CT perfusion mismatch is seen. The penumbra is outlined by a square
126
Fig. 3.47a–f Acute ischaemia in the left middle cerebral artery area. Т2-weighted imaging (a), Т1-weighted imaging (b) and DWI (c) reveal the affected brain area within the cortical regions of insular lobule of the left temporal lobe. CT perfusion with CBF (d), МТТ (e)
Chapter 3
and ТР (f) maps calculation reveal the area of decreased blood flow within the temporal lobe (arrow). МТТ and ТР maps additionally depict the change of blood flow in the left parietotemporal region– penumbra (arrows)
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.48a–f A follow-up observation of ischaemic infarction in the left temporal lobe according to CT. CT with contrast enhancement 24 h after ischaemic attack (a) reveals the area of hypodensity within the left basal ganglia. CT perfusion with CBF (b) and MTT (c) map
127
calculation demonstrate the area of impaired blood flow in the left temporal lobe. On day 7, by the time neurological deterioration has occurred, CT reveals a novel lesion (arrow) of density changes (d) and the same changes of perfusion parameters (e,f)
128
Chapter 3
Fig. 3.49a–c Ischaemia in the right internal carotid artery area (day 6). CT (a–c) without contrast enhancement reveals an area of almost to-
tal hypodensity of the right cerebral hemisphere, along with foci of haemorrhagic transformation with increased density. Severe contralateral dislocation of ventricular system is observed
Fig. 3.50a–c Ischaemic infarction in the left frontotemporal region (day 10). On a series of CT scans (a–c), there is an area of hypodensity
within the infarction (arrow) along with severe atherosclerotic lesions of cervical cerebral arteries with calcifications of walls
Fig. 3.51a–c Ischaemic infarction in the left internal carotid artery
area day 12 after ischaemic attack. A series of CT scans (a–c) reveals an area of almost total hypodensity of the left cerebral hemisphere
with relative preservation of the left basal ganglia and the left occipital lobe. Foci of haemorrhagic transformation are seen in subcortical regions (arrows)
Cerebrovascular Diseases and Malformations of the Brain
129
Fig. 3.52a–f Ischaemic stroke in the left temporal lobe. CT on day 7 before (a–c) and after (d–f) intravenous contrast injection: a character-
istic enhancement along the affected cerebral gyri (the areas of hyperdensity) is seen in the left temporal lobe
Fig. 3.53a–c Ischaemic stroke in the right frontal lobe (day 4). On Т2-weighted imaging (a), there is a hyperintense area involving grey and white matter of the frontal lobe. On Т1-weighted imaging be-
fore (b) and after (c) contrast enhancement, an area of heterogeneous hypointensity is seen without focal contrast enhancement. The gyri of affected area are markedly thickened
130
Chapter 3
Fig. 3.54a–c Ischaemic stroke in the posterior portions of the right frontotemporal region (day 5). Т2-weighted imaging (a) reveals a hyperintense area involving temporal cortex, on Т1-weighted imaging, this area has a hypointense signal (b). DWI better visualises the distribution of brain damage (c), with high signal intensity
Fig. 3.55a–c Subacute ischaemic infarction in the left basal ganglia (day 6). Т2-weighted imaging (a) and DWI (c) demonstrate an area of
local hyperintensity. Changes in Т1-weighted images (b) are less pronounced; the affected area possesses hypointense signal
Cerebrovascular Diseases and Malformations of the Brain
cantly diminishes at the end of first week. Meanwhile, contrast enhancement appears and starts to grow in cortical and subcortical regions of the affected (as defined by a standard MRI) brain area. Unlike CT with the use of MRI, the expressiveness of such enhancement is greater; thus, it is better visualised (Figs. 3.56–3.58). In some observations, the degree and the form of contrast enhancement can look atypical and resemble a neoplasm such as glioblastoma or metastasis (Fig. 3.59). By the end of the subacute phase, the mass effect diminishes, thus reflecting the oedema reduction in the ischaemic area. The haemorrhagic transformation in the stroke area reveals itself in MRI with the use of T1-weighted imaging as the foci of increased MR signal (such increase occurs due to met haemoglobin formation) (Figs. 3.60–3.62). MR signal changes
131
caused by haemorrhage on T2-weighted imaging are less discernible and are characterised by decrease or increase of MR signal, and they are insufficiently differentiated in this mode from an oedemic area. On DWI, the certain changes in the MR signal that have important prognostic value for the final disease outcome are also observed. In the beginning of the subacute phase, a signal from the ischaemic area is very high, and at this time, even multiple small foci are precisely visualised (Figs. 3.63–3.65). Then, usually within the first 7–10 days, the high MR signal on DWI from an ischaemia area (cytotoxic oedema) is gradually replaced by the isointense phenomenon pseudonormalisation. Thus, the site of ischaemia cannot be practically visualised on DWI at the end of the second week. The important
Fig. 3.56a–c Subacute ischaemic infarction in the right occipital lobe (day 10). Т2-weighted image (a) and Т1-weighted image before (b)
and after (c) contrast enhancement reveal a focal lesion of blood–brain barrier destruction within the ischaemic area, which simulates a tumour
Fig. 3.57a–c Subacute ischaemic infarction of the right thalamus in a 3-year-old child. Т2-weighted image (a) and Т1-weighted imaging
before (b) and after intravenous contrast medium injection (c) reveal the peripheral contrast enhancement of the infarction area
132
Fig. 3.58a–c Ischaemic stroke in the right cerebellar hemisphere
(day 7). Т2-weighted image (a) Т1-weighted image (b) (the lower series is with contrast enhancement), DWI (c upper series) and FLAIR
Fig. 3.59a–f A follow-up observation of ischaemic infarction in the area of both anterior cerebral arteries. CT (a) with contrast enhancement (day 16 after infarction) visualises an area of focal heterogeneous accumulation of contrast medium in the left half of genu of corpus callosum. In Т1-weighted images after contrast enhancement in axial (b,c), sagittal (d), and coronal (e) projections, there are areas of heterogeneous accumulation of contrast medium within corpus
Chapter 3
(c lower series) reveal an area of typical for haemorrhagic transformation signal changes on Т1-weighted imaging with low contrast enhancement (b) along the affected gyri
callosum bilaterally, and the left cingulated gyrus along with small foci of hyperintensity in the frontoparietal region. Compression of lateral ventricles is minimal. Stereotactic biopsy did not find any tumour cells. MRI on day 28 with Т1-weighted imaging (f) demonstrates that pathological changes in the described area regressed, and focal haemorrhagic transformation of medial brain surface appeared
Cerebrovascular Diseases and Malformations of the Brain
133
Fig. 3.60a–c Subacute ischaemic infarction in the left middle cerebral artery area (day 11). MRI reveals a heterogeneous signal change on
Т2-weighted (a) and Т1 -weighted images (b,c). Focal hyperintensities in the Т1 sequence represents zones of methaemoglobin formation
Fig. 3.61a–f Subacute ischaemic infarction in the right frontotemporal region (day 12). Т2-weighted images (a–c), Т1-weighted images (d,e), and 3D TOF MRA (f). On Т1-weighted imaging, there is a heterogeneous hyperintense area, following the shape of frontal gyri in
several places. Haemorrhagic transformation within putamen and globus pallidus is seen on the affected side. MRA reveals the marked narrowing of the middle cerebral artery lumen with absence of the right internal carotid artery visualisation due to its thrombosis
134
Fig. 3.62a–f Ischaemic infarction of both thalami. Т2-weighted image (a), Т1-weighted images (b–d), and FLAIR (e) demonstrate two lacunar infarctions within the anteromedial thalamic nuclei, which occurred at different times. To the left is the “old” one, to the right is a
Chapter 3
subacute infarction. Hyperintense areas on periphery in Т1-weighted images is represented by methaemoglobin formation. DWI (f b = 500) did not reveal signs of acute ischaemic brain damage
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.63a–c Subacute ischaemic infarction of the right posterior
frontal region (day 8). Т2-weighted images (a), Т1-weighted images (b), and DWI (c) demonstrate a weakly hyperintense area on T2 in cortical and subcortical zone of the posterior frontal region
135
(arrows), and an area of haemorrhagic transformation in cortex on Т1-weighted images (arrow) is observed. DWI visualises the volume of affected brain area better (hyperintense signal)
Fig. 3.64a–f Subacute ischaemic infarction in the internal carotid artery area (day 9). Т2-weighted images (a,b), Т1-weighted images (c,d), and DWI (e,f) reveal multiple lesions of pathological signal changes in the left cerebral hemisphere. Small lesions are visualised only on DWI
136
Chapter 3
Fig. 3.65a–f Ischaemic infarction in the left middle cerebral artery area (day 12). Т2-weighted image (a), FLAIR (b), and DWI (c,d) reveal
a large hyperintense area in the left temporoparietal region, visualised with involvement of temporal cortex. ADC maps (e,f) show the dark ischaemic area (arrows)
point is the construction of maps based on ADC. In these maps, the stroke-affected area has brighter colour than normal bran tissues do. Further stroke progression with the resorption of the affected brain areas (transition to the chronic stage usually takes place in the first 1–3 months) leads to gradual decrease of MR signal intensity on DWI (at b = 1,000) and to digital parameters on ADC maps, which become close to values of CSF in the ventricular system (the stage of encephalomalacia) (Figs. 3.66, 3.67).
3.2.2.3
Chronic Phase of Ischaemia
Strokes in the chronic stage (more than 3 months) are visualised on CT as areas of CSF density (the areas of encephalomalacia). They can be accompanied by compensatory dilatation of the ipsilateral part of the ventricular system. This reflects the decrease of the brain tissue volume (Figs. 3.68, 3.69). Dystrophic calcification of the marginal zone of the gliosis of adjacent brain tissue is a rare phenomenon, and it more often occurs in children than in adults. The perifocal stroke area that represents the area of gliosis can have hypodense characteristics. Contrast enhancement on CT is no longer visualised because the process of blood–brain barrier reparation is complete.
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.66a–i A follow-up observation of ischaemic infarction in the
internal carotid artery area. Т2-weighted images (a), DWI (b), and 3D TOF AG (c) on day 10 after onset reveal a large hyperintensive area. On MRA several distal branches of the middle cerebral artery are not visualised, and focal stenosis is seen within its bifurcation. A
137
follow-up study on day 20 in Т2-weighted imaging (d), DWI (e) and Т1-weighted imaging (f), as well as on day 40 in the same regimens (g–i) reflect the process of encephalomalacia formation. Areas of hyperintense signal on DWI (e,h) correspond to the areas of preserving ischaemia
138
Chapter 3 Fig. 3.67 Graphic representation of dynamics of ischaemic infarc-
tion by MRI. Three curves on the graph reflect changes of signal and diffusion velocity, in Т2, DWI (b = 1000), and ADC maps: the point where curves of DWI and ADC parameters cross corresponds to the time when “pseudonormalisation” phenomenon occurs
Fig. 3.68a–c Ischaemic infarction in the left internal carotid artery
area due to thrombosis. On a series of CT scans with contrast enhancement performed 2 months after onset (a–c), there is a markedly hypodense area in the left frontoparietal-temporal region (region
of encephalomalacia), along with that the images of the left internal carotid artery, and the left middle cerebral artery are absent. The adjacent lateral ventricle is focally dilated (focal lesions of blood–brain barrier damage within the ischaemic area are seen; arrow)
Fig. 3.69a–c Variants of location of ischaemic lesions in chronic stage according to CT: the right occipital region (a), the left parietal region (b) and the right frontoparietal-temporal regions (c)
Cerebrovascular Diseases and Malformations of the Brain
139
Fig. 3.70a–c Ischaemic infarction of the left temporal lobe. Т2-weighted imaging (a), Т1-weighted imaging (b), and FLAIR (c) 2 months after the stroke. The area of encephalomalacia with gliosis of adjacent brain tissue are better depicted by FLAIR
The areas of cystic changes of the brain tissue in the stroke zone are clearly visualised on MRI as well as on the CT; the degree of the intensity of these changes depends on the time passed since the stroke onset by the time of examination. In the early stroke stage, there is heterogeneous increase of the MR signal on T2 and FLAIR images, on T1-weighted imaging the signal is decreased and contrast enhancement may be visualised longer than on CT (Figs. 3.70, 3.71). During the late period (usually after 3–6 months), the MR signal in the stroke area in T1 and T2 modes has characteristics similar to those of CSF. FLAIR sequence is more informative, and it better defines the areas of increased MR signal in the perifocal zone of post– ischaemic gliosis around the focus of encephalomalacia (Figs. 3.72–3.74). Similar changes can be retained for several months after the end of stroke. The parts of the ventricular system adjacent to the stroke area usually are dilated and tightened to the cystic transformation focus. However, this can be observed in cases of large stroke areas. A small stroke can be presented by just a CSF cavity in the brain tissue (Fig. 3.75), without the dislocation of ventricle. It is mentioned above that in the chronic stage, DWI defines the encephalomalacia focus, with typical signs like areas of decreased MR signal on DWI images. The main aim of DWI examination is assessment of the surrounding brain tissues and early diagnosis of repeated strokes (Figs. 3.76, 3.77). An important aspect of any MRI diagnosis of ischaemic strokes is not only the capacity to perform multiparameter cranial examination that includes DWI and PWI, but also an assessment of the aetiological reason of stroke.
Minimal invasiveness of neuroimaging methods, such as CT and MRI, lead to their wide application in diagnostics of associated lesions of cranial and especially extracranial segments of carotid and vertebral arteries. At the same time, it should be remembered that absence of brain changes or their minimal intensity cannot exclude arterial pathology (Figs. 3.78–3.80).
3.3
Lacunar Infarction
As a rule, the occlusion of small arteries leads to minor stokes or lacunar infarctions. Such infarction constitutes about 15– 25% of all stroke cases (Regli 1993). A lacunar stroke is a small focus of cerebral affection, usually located in the depth of grey matter—in the projection of the basal ganglia and thalamus, the brainstem, the internal capsule and the deep white matters of the cerebral hemisphere. The main reason for their development is an impact on small perforating arteries (more frequently lenticulostriatal and thalamoperforating arteries). The term lacunar stroke means the affected area is usually less than 1 cm in diameter; in rare cases, they reach 1.5 cm (Fisher 1979). The main factors contributing to their development are hypertension, diabetes mellitus, etc.; the most important aetiological factors are diseases such as atherosclerosis (the most frequent) and some relatively rare diseases such as vasculitis, vasculopathy and meningitis. The clinical course and clinical manifestation of the disease depends on stroke location. Fisher (1991) outlined up to
140
Fig. 3.71a–f Ischaemic infarction in the right middle cerebral artery
area (1 month). Т2-weighted imaging (a), Т1-weighted imaging before (b) and after (c) contrast enhancement reveal an area in the temporal region with gyri-like pathological accumulation of contrast medium.
Chapter 3
On Flair image (d) lesion has heterogeneous MR-signal. On DWI (e b = 500, f b =1000) the peripheral area of hyperintensive signal are found (persistent ischaemia)
Fig. 3.72a–c Six months after ischaemia in the right middle cerebral artery area. Т2-weighted images (a,b) and Т1-weighted images (c) reveal the area of focal encephalomalacia of the temporal lobe
Cerebrovascular Diseases and Malformations of the Brain
141
Fig. 3.73a–c Consequences of ischaemic infarction in the left internal carotid artery area. Т2-weighted images (a) and Т1-weighted images
(b) 13 months after stroke reveal a large area of encephalomalacia with relative sparing of occipital lobe. MRA in 3D TOF (c) shows the absence of the left internal carotid artery and its branches
Fig. 3.74a–e Ten months after stroke in the left middle cerebral artery area. Т2-weighted imaging (a), Т1-weighted imaging (b) and FLAIR (c,d) reveal a focal area of encephalomalacia of the left temporal lobe. Peripheral gliosis of brain tissue is better visualised on FLAIR images as hyperintense areas. 3D TOF MRA (e) shows absence of imaging of the distal branches of the left middle cerebral artery
142
Chapter 3
Fig. 3.75a–c Focal ischaemia in putamen and head of caudate nucleus. MRI 5 months after stroke reveals an area of signal change in the right
basal ganglia (a–c); its MR features are almost identical to CSF signal intensity in the lateral ventricles
Fig. 3.76a–d Ischaemic infarction in the left internal carotid artery area. MRI 3 months
later on Т2- (a), Т1- weighted images (b), and DWI (c). Along with old ischaemic changes there is a peripheral area of hyperintense signal on Т2 -weighted imaging and, especially, on DWI, corresponding to the area of recurrent ischaemia. 3D TOF MRA (d) shows absence of the left internal carotid artery image (thrombosis at the cervical level). Branches of the middle cerebral artery are partially filled with contrast medium due to reflow from the right internal carotid artery area and in posterior circulation system via the ACA and the posterior communicating artery
Cerebrovascular Diseases and Malformations of the Brain
143
Fig. 3.77a–c Lacunar infarction in the right basal ganglia. Т2- (a) and Т1- (b) weighted images demonstrate two microcysts filled with
CSF in the right putamen. On Т2-weighted imagine and, especially on DWI (c) (arrow), an area of changed signal is visualised behind (recurrent ischaemia)
Fig. 3.78a–c Thrombosis of the internal carotid artery at the cervical level without focal changes of brain tissue. Т2-weighted images (a,b) do not reveal pathological changes in brain tissue except for diffuse atrophy. 3D TOF MRA shows the absence of image of the right internal carotid artery and its branches (c)
144
Fig. 3.79a–f Variants of location and distribution of ischaemic cerebral infarction in different extent of cerebral arteries atherosclerosis. Case 1. Ischaemic infarction of temporal lobe due to stenosis of the middle cerebral artery (a,b). Case 2. Lacunar infarction in the right
Chapter 3
basal ganglia–occlusion of the middle cerebral artery (c,d). Case3. Ischaemic infarction (e) of the left parietal lobe–occlusion (f) of ostium of the internal carotid artery (arrow)
Fig. 3.80a–c Ischaemic infarction of the right temporal lobe. Т2-weighted image (a) visualises the area of focal ischaemia. CTA reveals severe atherosclerotic damage of the left (b) and the right (c) carotid arteries
Cerebrovascular Diseases and Malformations of the Brain
five classical clinical syndromes that can be present in lacunar infarction.
3.3.1 Diagnosis With the use of standard CT, the visualisation of small strokes is rather complicated. The thin slices and minimal step between them should be used for more precise diagnostics. In typical cases, the lacunar infarction is represented by a small area of decreased density. MRI is superior to CT in the detection of the site and the stage of stroke. DWI is the most informative method in the acute-stage diagnostics because it visualises minimal changes of water concentration in tissues. As a rule, the acute lacunar infarction has high MR signal, and it is located in the projection of basal ganglia (Figs. 3.81, 3.82). Lunar infarction is more frequently diagnosed in the chronic stage, when MRI in T1 mode reveals hypointense microlesions of decreased MR signal and the focus of increased MR signal in T2 mode. The stroke-area MR characteristics are
145
similar to those of CSF. The use of FLAIR helps to identify the perifocal area of brain tissue gliosis in the form of border of increased MR signal (Figs. 3.83–3.86). MRI with high spatial resolution reliably detects microscopic (1–2 mm) lacunar strokes. Such strokes can sometimes be characterised by focal symptoms (neurological signs), for instance, impact on the nucleus of the cranial nerves in the case of stroke localisation in the brain stem (Fig. 3.87). In the case of presence of multiple lesions, they should be differentiated from widened perivascular spaces (Virchow-Robin space) and sometimes from demyelinating process and multiple metastases (Figs. 3.88, 3.89). One of MRI’s advantages over CT in an estimation of stroke consequences is its ability to visualise descending Wallerian degeneration of axons, usually visible as atrophic changes in the brain stem and corticospinal pathway on the side of affection, with the increase of the MR signal in T2 and FLAIR modes. Any stroke has a link to this or that artery area (Fig 3.90). Based on the site, all strokes can be divided on supra- and infratentorial ones, depending on the affected artery area [in-
Fig. 3.81a–f Acute ischaemic infarction of the left thalamus (day 2 after onset of rightward hemiparesis). Т2- (a), Т1- (b) weighted images, Т1 with contrast enhancement (c), FLAIR (d) and DWI (e b = 1,000, f b = 500) demonstrate an area of focal signal change within the left thalamus. No signs of blood–brain barrier disruption were found
146
Chapter 3
Fig. 3.82a–c Acute ischaemic infarction of the right thalamus. Т2-weighted imaging (a), FLAIR (b) and DWI (c) reveal the clear-cut hyper-
intense area in pulvinar thalami (day 5 after onset of leftward hemiparesis)
Fig. 3.83a–c Chronic stage of lacunar infarction in the right basal ganglia. Т2-weighted imaging (a,b) and Т1-weighted imaging (c) reveal a microcyst within the thalamus
Fig. 3.84a–c Lacunar infarction in the left basal ganglia with microcyst. Т2-weighted image (a) and Т1-weighted image (b) of a 6-year-old-
child with nodular heterotopia of the right periventricular region (c)
Cerebrovascular Diseases and Malformations of the Brain
147
Fig. 3.85a–c Lacunar infarction in the right thalamus on Т2-weighted image (a), Т1-weighted image (b) and FLAIR (c)
Fig. 3.86a–c Lacunar infarction in the right cerebellar hemisphere. Т2-weighted image (a), Т1-weighted image (b) and FLAIR (c). Gliosis in the peripheral area of infarction–hyperintense signal on FLAIR images is seen
Fig. 3.87a–c Lacunar infarction in the bottom of fossa rhomboidea to the right (arrow). Т2-weighted image (a) and Т1-weighted image (b,c) in a patient with isolated abducens nerve palsy
148
Fig. 3.88a–f Multiple lacunar infarctions in a patient with chronic
ischaemic brain disease within the pons and white matter of parietal lobes, simulating multiple sclerosis. Т2-weighted imaging (a,b),
Chapter 3
Т1-weighted imaging (c,d) and FLAIR (e,f) demonstrate multiple lacunar infarctions in a stage of cystic transformation on the background of severe encephalopathy
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.89a–i Multiple lacunar infarctions of brainstem and basal
ganglia bilaterally, chronic ischaemic brain disease. Т2-weighted images (a–d) demonstrate multiple lacunar infarctions; their MR signal features are similar to those of CSF of the lateral ventricles.
149
Т1-weighted image at the level of the third ventricle–lacunar infarction in the right basal ganglia—a microcyst (e). A hyperintense area (f–i) along the corticospinal tract better detected on FLAIR–Wallerian degeneration
150
Fig. 3.90 Schematic representation of cerebral blood supply. 1 middle cerebral artery, 2 ACA, 3 posterior cerebral artery, 4 medial lenticulostriatal arteries, 5 lateral lenticulostriatal arteries, 6 perforating arterial branches of thalamus and midbrain (posterior choroidal and
Chapter 3
thalamic perforating arteries), 7 anterior choroidal and thalamic perforating arteries, 8 superior cerebellar artery, 9 perforating branches of the basilar artery, 10 posterior inferior cerebellar artery, 11 anterior inferior cerebellar artery
Cerebrovascular Diseases and Malformations of the Brain
ternal cerebral artery (ICA) and its main branches: MCA, anterior cerebral artery (ACA), and posterior circulation area (PCA)]. Based on the affected area, all strokes are divided into small, intermediate, large, and massive. The anterior cerebral artery area. Isolated strokes in this area is a rare phenomenon; they happen in no more that 5% of cases. In case of the ACA-area stroke, MRI identifies the change of MR signal from medial regions of frontal lobes with less sensitivity than CT does (Fig. 3.91). The gyri are thickened. Cerebral angiography can reveal the presence of collateral circulation in frontal lobes through leptomeningeal branches of the ICA and even through the posterior circulation area. The middle cerebral artery area. The strokes in this area are the most frequent (about 75% of all stroke cases). The stroke can affect the entire arterial are supplied by the MCA, includ-
151
ing basal ganglia, or only the cortical part may be affected. It largely depends on occlusion level and the state of compensatory collateral circulation from the branches of the ACA and the PCA. MCA thrombosis at the level of bifurcation in the case of sufficient collateral blood flow the damage is limited to the insula of temporal lobe. If occlusion occurs in one of the MCA branches, then ischaemic changes affect the area of blood supply of this particular artery. Strokes in the basal ganglia belong to the particular type of stroke in term of location. More often, they are striatocapsular strokes, which affect lentiform nucleus, external capsule, claustrum, the anterior genu of internal capsule and the head of caudate nucleus (Fig. 3.92). The reason for stroke is an occlusion of the lenticulostriatal arteries departing from initial MCA segment. This can be observed in case of the occlusion
Fig. 3.91a–c Ischaemic infarction in the anterior cerebral arteries area. Т2-weighted imaging (a,b) and FLAIR (c) demonstrate isolated
damage of cortex of medial regions of frontal lobes
Fig. 3.92a–c Ischaemic infarction of the right basal ganglia. Т2-weighted images (a,b) and FLAIR (c) reveal focal ischaemic changes in putamen and head of the caudal nucleus
152
of these arteries themselves or in case of the MCA occlusion. In these cases, the head of caudal nucleus, which is also supplied from Heubner’s artery, might not be affected. Separate strokes in the area of the anterior and posterior choroid arteries (posterior genu of internal capsule, part of globus pallidus, optic tract, part of uncus, amygdaloid body and vascular plexus of the lateral ventricle) are rare. In cases of occlusion of the thalamoperforating arteries (anterior and posterior), which participate in supply of the thalamus and hypothalamus, lacunar stroke develops in the respective areas. Strokes of the watershed zone affect areas of joint blood supply between long perforating arteries of white matter, descending from MCA, and deep pial branches of arteries of
Chapter 3
cortical brain surface. The typical location of such stroke is periventricular white matter of the brain hemispheres. These strokes are seen in MRI as plane elongated alongside affected area. The posterior cerebral artery area. The area of joint blood supply between the MCA and the PCA varies, and there are many variants of its possible development. In normal situations, the PMA supplies the posterior third of convex brain surface, part of lower surface of temporal lobe and also participates in supplying of posterior genu of internal capsule and, in part, of subcortical brain structures. The occipital lobe is the second most frequent stroke location after MCA area. In the majority of cases the affected areas
Fig. 3.93a,b Ischaemic infarction in the right posterior cerebral artery area (chronic stage). a Т2- and b Т1-weighted images
Fig. 3.94a–c Ischaemic infarction in left the posterior cerebral artery area (chronic stage). a,b T2- and c Т1-weighted images
Cerebrovascular Diseases and Malformations of the Brain
are cortex in the area of calcarine sulcus and the area of deep perforating arteries of thalamus, midbrain and the posterior genu of internal capsule (Figs. 3.93–3.96). The basilar artery area. The mortality in patients with basilar artery area thrombosis is 2.5 times more than in patients with carotid arteries occlusion. The main aetiological reasons for thrombosis development are thromboembolism, atherosclerosis, malformation, syphilis, tuberculosis and fungal meningitis. Basilar artery occlusion at the level of distal segment leads to affection of thalamus, the posterior genu of internal capsule and midbrain. In the case of affect on the short branches of basilar artery, the ischaemic focus is visualised in pons. The
153
clinical presentation develops according the two possible scenarios. In the first scenario, the acute thrombosis with the affection of the main pons structures leads to subsequent death. As a rule, such patients have no time to be investigated by CT and MRI. The main reason is thromboembolism. In the second scenario, thrombosis development is prolonged and neurological deficits grow gradually. Such patients have time for examinations and treatment. On CT in the case when acute thrombosis of the basilar artery is suspected, paramount attention is focused on the image of the basal artery. Increase of its density, defined on several scans, can lead to assumption of its thrombosis. MRI with DWI is a more preferable option because it visualises the
Fig. 3.95a–f Ischaemic infarction in the left posterior cerebral artery area (acute stage). Т2-weighted images (a–c) and Т1-weighted image
(d) demonstrate a large affected area in the left parieto-occipital region. MRI 3 months later reveals an area of focal encephalomalacia of the occipital lobe (e–f)
154
Chapter 3
Fig. 3.96a,b Bilateral ischaemia in the posterior cerebral artery area in a 12-year-old child. Chronic stage. Т2-weighted image (a) and Т2weighted image (b) demonstrate bilateral lesions of encephalomalacia with severe isolated atrophy of occipital lobes
area of ischaemic damage of the pons within the first hours since the stroke onset (Figs. 3.97, 3.98). MRA with the use of 3D TOF and 3D PC techniques can additionally establish the absence of basilar artery blood flow. The superior cerebellar artery area. As a rule, the superior cerebellar arteries descend from the distal segment basilar artery before its partition into the PCAs. These arteries supply the upper segments of the cerebellar hemispheres, upper vermis, and the major part of cerebellum’s white matter. Occlusion of the one of these arteries leads to stroke in the cortex of the superior portion of the affected cerebellar hemisphere, in the ipsilateral portion of the vermis and in the cerebellar white matter (Fig. 3.99). MRI is more informative in the assessment of the stroke in the cerebellum in all stages of the ischaemic process development. The anterior inferior cerebellar artery (AICA). The area and the length of the anterior inferior cerebellar artery can vary. Usually, the AICA supplies the flocculus, the anterior surface of cerebellum, the middle cerebral peduncle and part of the pons. Isolated stroke in this area is a rare phenomenon, and such strokes are observed in patients with diabetes mellitus and hypertension. MRI (CT is worse) visualises the affection of the lateral region of the cerebellar hemisphere in case of AICA artery occlusion (Fig. 3.100). Area of posterior inferior cerebellar artery (PICA). This area occupies the major part of the cerebellar hemispheres (the posterior inferior portions), cerebellar tonsils and inferior vermis. Strokes in this area are the most common among all
cerebellar stroke. Sometimes, isolated PICA stroke leads to development of the classical Wallenberg syndrome (the loss of pain and temperature sensitivity on the contralateral part of the body, ipsilateral loss of motor functions, ataxia and nystagmus) with involvement of the lateral portions of medulla oblongata and inferior cerebellar peduncles. However, the occlusion of the vertebral artery is the most frequent reason for the above mentioned scenarios. In these cases the typical lenticular affect inferior portions of cerebellum, with downward orientation of the convex side (Figs. 3.101, 3.102).
3.4
Chronic Ischaemic Brain Disease
Chronic ischaemic brain disease (CIBD) belongs to the group of chronic ischaemic brain disorders. Such disorders are observed in cases of protracted atherosclerosis and hypertension. Focal neurological signs are largely absent or presented by non-specific symptoms. Neuroimaging changes are observed during control examinations performed due to recurrent headache, memory loss, increased fatigability, etc. Diagnosis is based on the results of brain MRI (Averkieva 2003). In T2 and FLAIR sequences (the latter pulse sequence is preferable), multiple small foci are visualised in the white matter of the supratentorial location, in periventricular area and in the subcortical regions (Figs. 3.103, 3.104).
Cerebrovascular Diseases and Malformations of the Brain
155
Fig. 3.97a–f Ischaemic infarction in brainstem (day 3). Т2-weighted imaging (a), Т1-weighted imaging (b), FLAIR (c) and DWI (d) demonstrate two ischaemic lesions in the pons. 3D TOF MRA in coronal (e) and oblique lateral (f) projections visualises narrowing and deformity of the basilar artery
Fig. 3.98a–c Ischaemic infarction in pons to the left (chronic stage). Т2-weighted image (a) and Т1-weighted images (b,c) reveal an area of
heterogeneous signal changes with initial formation of the CSF cyst
156
Chapter 3
Fig. 3.99a–c Consequences of ischaemia in anterior inferior cerebellar artery area (chronic stage, 6 months). Т2-weighted images (a,b) and Т1-weighted image (c) reveal the area of focal encephalomalacia in the superior portion of the left cerebellar hemisphere
Fig. 3.100 Ischaemia in the posterior inferior cerebellar artery area. Т2-weighted image: a hyperintense area in the anterolateral region of the left cerebellar hemisphere with involvement of middle cerebellar peduncle and lateral portion of pons
Cerebrovascular Diseases and Malformations of the Brain
157
Fig. 3.101a–c Ischaemia in the posterior inferior cerebellar artery area. Т2-weighted image (a), FLAIR (b) and DWI (c) demonstrate an acute
ischaemic lesion in the deep structures of the left cerebellar hemisphere Fig. 3.102 Ischaemia in the posterior inferior cerebellar artery area. Т2-weighted images reveal an area of post-ischaemic changes in the posterior portions of the left cerebellar hemisphere
Fig. 3.103a,b Chronic ischaemic brain disease in a 65-year-old patient. Т2-weighted imaging (a) and FLAIR (b) demonstrate hyperintense areas in subcortical and periventricular white matter
158
Chapter 3
Fig. 3.104a–c Chronic ischaemic brain disease in a 72-year-old patient with arterial hypertension. FLAIR (a,b) and Т2-weighted imaging
(c) demonstrate hyperintense area in the brainstem and periventricular white matter of the frontotemporal region
The presence of atrophic brain changes in diffuse dilatation of CSF spaces are typical (Fig. 3.105). In uncomplicated cases, the changes of signal in T1-weighted imaging are absent. In the late stage, large areas of increased signal are detected in white matter (Figs. 3.106, 3.107). The presence of areas with CSF density on T1- and T2-weighted imaging may point to lacunar infarction. If pathological focuses are visualised in the periventricular white matter, then differential diagnosis with multiple sclerosis should be made. Multiple sclerosis is characterised by involvement of structures of subtentorial area and corpus callosum. MRI with contrast enhancement also helps to differentiate these two dis-
eases, because the contrast accumulation in the defend foci is not typical for CIBD. Nevertheless, young patients should be examined to rule out demyelinating brain disorders. In most cases, CT seems to be incapable detecting focal brain changes in the typical forms of CIBD.
3.5
Stroke in Children
It is thought that stroke in children constitutes not more than 3% of all strokes. Their aetiology differs from those of adult strokes. The most frequent cause of stroke in children is con-
Fig. 3.105a–c Chronic ischaemic brain disease in a 72-year-old patient with arterial hypertension and cerebral atherosclerosis. There are severe atrophic changes of brain tissue in temporal regions on Т2-weighted imaging (a), Т1-weighted imaging (b) and FLAIR (c), along with multiple hyperintense lesions
Cerebrovascular Diseases and Malformations of the Brain
159
Fig. 3.106a–c Chronic ischaemic brain disease. Т2-weighted image (a) and Т1-weighted images (b,c). Multiple local dilation of periventricu-
lar spaces with areas of MR signal change in basal ganglia and periventricular regions are seen. Severe brain atrophy is observed as well
Fig. 3.107a–c Chronic ischaemic brain disease in a 75-year-old patient with arterial hypertension and cerebral atherosclerosis. Т2-weighted images (a–c) reveal brain atrophy and ventriculomegaly along with large hyperintense areas in the frontotemporal white matter bilaterally
160
Chapter 3
genital heart anomaly with thromboembolism in brain arteries (Fig. 3.108). Less frequently, stroke occurs after injury of the extracranial arteries’ vascular wall, infectious disease (vasospasm at the time of the abscesses formation, meningitis, tonsillitis, sinusitis), overdose of medicines (for example, sympathomimetic agents), disorders of blood coagulation or birth trauma (Fig. 3.109). Some congenital diseases are the cause for the narrowing of the arterial vessels and stroke development (fibromuscular dysplasia, moyamoya disease, Marfan syndrome, NF I, tuberous sclerosis).
3.6
Non-Atherosclerotic Stenosis and Occlusion of Cerebral Arteries
Although atherosclerosis of vessel wall is the most frequent cause of narrowing of cerebral arteries and thus the most frequent cause of stroke, nevertheless, many congenital and acquired disorders can also lead to arterial stenosis. They can be the cause of stroke and chronic circulation disorders.
3.6.1 Congenital Pathology 3.6.1.1
Aplasia and Hypoplasia
True aplasia of the carotid artery is a rare phenomenon, and it is detected only by the absence of carotid artery osseous canal in the temporal bone projections on CT images, or with the help of angiography examination of aorta arch and cervical vessels. In these cases, the circulation reorganises and supplies
Fig. 3.108a–c Ischaemic infarction in a 7-year-old child in the left basal ganglia (chronic stage). CT scan (a) visualises an area with hypodensity identical to CSF in the lateral ventricles. MRI in Т2-weighted image (b): a cystic cavity with peripheral gliosis in the
the appropriate brain hemisphere from the vessels of the opposite side or from the posterior circulation area. Hypoplasia is no more frequent a phenomenon than aplasia. However, the diagnosis should be established with some caution, because while the artery narrowing can be a separate occurrence, the main reasons for narrowing differ. Unlike carotid arteries, the aplasia/hypoplasia of the vertebral arteries is a more frequent event. In these cases, it is feasible to apply CT angiography, which visualises asymmetrical narrowing of the osseous canals in the transverse processes of cervical vertebras (this should not be confused with acquired narrowing of one of the vertebral arteries due to atherosclerosis of the artery’s ostium).
3.6.1.2
Neurocutaneous Syndromes
Lesions of the vessel’s wall due to phacomatosis are a rare albeit striking phenomenon. NF I (von Recklinghausen’s disease) is one of the frequent syndromes that can lead to narrowing of the arteries. Large arteries are usually involved in the process (arch of aorta, celiac trunk vessels, mesentery vessels, kidney arteries). The involvement of cervical and cranial vessels is also observed. In the majority of cases, it is occlusion or stenosis; however, saccular aneurysm and malformations are also formed. Cases of arterial dysplasia are also observed in patients with tuberous sclerosis. It is a progressing degenerate disorder of a vascular wall, accompanied by stenosis and even by aneurysm formation. Such aneurysms are reported in the descending aorta; however, carotid artery stenosis is also observed in some patients with this disease. The carotid arteries aplasia,
same site. 3D TOF MRA (c) reveals absence of visualisation of the basilar artery, with a fairly good imaging of the posterior communicating and posterior cerebral arteries
Cerebrovascular Diseases and Malformations of the Brain
161
Fig. 3.109a–f Case 1. Ischaemic infarction in the middle cerebral artery area in a 5-year-old child. Т2-weighted image (a) and Т1-weighted image (b) of encephalomalacia of almost the entire lobe. The adjoining lateral ventricle is dilated, and hemiatrophy of the right hemisphere is seen. 3D TOF MRA (c) does not show the distal segment of the right middle cerebral artery. Case 2. Ischemic infarction in the
middle cerebral artery area in a 2-year-old child. Т2-weighted image (d) and Т1-weighted images (e,f) reveal areas of encephalomalacia in temporal regions more leftwards, with ventriculomegaly and incorrect form of skull (premature perforation of the lambdoid suture)
aneurysms and diverticular protrusions of the greater circulation vessels and cranial vessels can also accompany KlippelTrenaunay-Weber syndrome. Moyamoya disease belongs to a group of cerebrovascular diseases with unclear aetiology with progressing clinical course. It is characterised by stenosis of a cranial segments of ICA with formation of the net of basal pathological anastomosis. Initial segments of ACA and MCA and vessels of posterior circulation area can also be involved in the process. It is believed that the disease more frequently affects women than men (the ratio is 1.8:1.0) (Fukui 1997). Usually the disease presents in the first decade of life, however, adult cases are also observed. Two main peaks of this disease have been described: about 4 years and between 30 and 40 years (average 37.7 years) of
life. Ischaemic manifestations are common for the first peak and haemorrhagic foci for the second one. Ten percent of all cases are the family form of moyamoya disease. The term moyamoya is Japanese for “puff of smoke”. This name gained popularity in the literature; however, the official name adopted in Japan (where the first cases were reported) is spontaneous occlusion vessels of the circle of Willis. Another name of this illness derived from the names of authors who fully described its clinical and imaging presentations of the Nishimoto-Takeuchi-Kudo disease. Previously, this disease was considered a specific disease of Japanese island inhabitants; however, lately cases of moyamoya have been reported in other countries: China, Korea and Russia. The most detailed and convenient description of all disease manifestations belongs to Suzuki and Takaku (1983), who
162
Chapter 3
coined the term moyamoya. Suzuki 1986 described six stages of the disease development. 1. Narrowing of the distal segment of ICA 2. Narrowing of the distal segment of ICA, with the formation of the small net of basal anastomosis; the other arteries are widened 3. Clear net of basal anastomosis in the background of the stenosis of the supraclinoid segment of internal carotid artery and the absence of contrasting of proximal ACA and MCA segments, while their distal segments and branches are filled with contrast from distal external carotid artery (ECA) branches
4. ICA occlusion up to level of posterior communicating artery, ACA and MCA are partly filled with contrast medium from the basal anastomosis system, the formation of the ethmoidal anastomosis net, the expansion of the basal anastomosis net around the ICA and formation of the anastomosis from the ECA 5. Absence of main cerebral arteries of the ICA system, the spreading of the carotid arteries narrowing up to the C2 segment, decrease of the basal anosmosis net and increase of the anastomosis system from ECA 6. Absence of the ICA on all angiograms from the level of siphon and above, the disappearance of the basal anasto-
Fig. 3.110a–f Angiographic stages of moyamoya disease (Suzuki 1986). a Stage 1: narrowing of the terminal section of the internal carotid artery. b Stage 2: the terminal section of the internal carotid artery is narrowed, the rest cerebral arteries are dilated and there is a mild basal net of anastomoses near bifurcation of the internal carotid artery. c Stage 3: increments of stenosis in the supraclinoid segment of the internal carotid artery, initial segments of the anterior and the middle cerebral arteries are not visualised and a basal net of anastomoses are clearly seen. d Stage 4: occlusion of the internal carotid artery up to the posterior communicating artery with absence of contrast visualisation of the latter; the anterior and the middle cerebral arteries are partially filled via the basal net of anastomoses, intensity of the basal net of anastomoses is decreased, an ethmoidal net of anastomoses appears and vessels of the basal net
appear weaker and become larger near the terminal segment of the basal net of anastomoses. The number of collaterals from the external carotid arteries is increased. e Stage 5: the main cerebral arteries of the internal carotid artery area disappear. Occlusion is expanded onto the С2 or С3 segment of the internal carotid artery. The basal net of anastomoses is markedly decreased and is detected only near the internal carotid artery siphon. The number of collaterals from the external carotid arteries is increased, and hypertrophy of this arterial supply appears. f Stage 6: the internal carotid artery from siphon and more distally completely disappears, and the basal net of anastomoses partially disappears. Only the external carotid artery anastomoses provide blood supply. The brain is supplied with blood by the external carotid and vertebral arteries
Cerebrovascular Diseases and Malformations of the Brain
mosis net and the intense development of the anastomosis system from the ECA and posterior circulation area—the main sources for supply of ICA area (Fig. 3.110) Clinical presentations usually depend on the patient’s age. For children, ischaemic attacks with stroke-like manifestations with the involvement of one or another hemisphere are more common. Epileptic seizures are also observed. For adults, the development of cranial haemorrhages is more typical. In these situations, the clinical prognosis is always poorer, with possible fatal outcome. Diagnosis relies more on direct cerebral angiography data; this method more adequately identifies the pathology of brain circulation (Figs. 3.111–3.113). Other methods can be used to collect additional information as well as for the screening purposes. The above-mentioned classification of disease stages, invented by Suzuki and Takaku, is primarily based on angiography data. The disease’s signs on CT depend on primary changes. The ischaemic focuses have decreased density; on later stages, brain atrophy and dilatation of the ventricular system is visualised. The visualisation of cranial haemorrhages depends on time passed since the event onset. It is necessary to note that in moyamoya, ischaemic and haemorrhagic lesions have bilateral character. CT examination (performed in patients with moyamoya) (Suzuki 1986) reveals the foci of decreased density in subcortical white matter of the brain hemisphere (36% cases), the cortex (28%) and basal ganglia (6%). Three areas of increased density have been observed: in basal ganglia (11% of all cases, the most frequent location), subcortical area (10%) and intraventricular area (5%). CT angiography detects stenosis and occlusion of the carotid arteries, with the development of multiple small anastomoses on the basal brain surface. The sensitivity of CT angiography in moyamoya diagnostics is 88.5% (Fukui 1997).
Fig. 3.111a–c Moyamoya disease in a 5-year-old child. Cerebral angiogram of the right (a) and left (b) common carotid arteries and the left vertebral arteries (c). In the arterial phase, the net of small basal pathologically coiled vessels is revealed along with stenosis of the
163
MRI and MRA more precisely depict brain tissue changes occurring in the course of moyamoya disease than CT and spiral CT. They are able not only to define lesion location and the bilateral character of the process, but also to identify the age of the lesion development, which is importance in the process of differential diagnosis. In patients with moyamoya, especially children, MRA is an alternative to direct digital angiography in the diagnostics of cranial vessel pathology. 3D TOF technique simultaneously demonstrates the presence of occlusion and stenosis of cerebral arteries and detect multiple small anastomoses on basal brain surface (Figs. 3.114, 3.115). However, one should always remember the consequences of disease stages and subsequent structural reconstruction of brain circulation (according to Suzuki 1986) in making a diagnosis.
3.6.1.3
Sickle-Cell Anaemia
Stroke is one of the most severe complications for the patients with this disease (generally in patients with a severe form of sickle-cell anaemia). It occurs in 5–6% of all cases. Ischaemia prevails over the haemorrhage. Children are ill more often than adults. Pathophysiological mechanisms of stroke in patients with sickle-cell anaemia are unclear, remain controversial and are yet to be defined. On one hand, strokes are caused by the occlusion of capillaries, small arterioles and brain venules by the conglomerates of pathologically changed erythrocytes. On the other hand, strokes also result from blood stasis in the vasa vasorum system, the development of a progressing thickening of intima– media of the cerebral arteries, and their subsequent obliteration. The carotid arteries are more frequently involved than arteries of the posterior circulation area (about 17% of all cases). Stenosis and occlusion develops in the affected arteries that in
internal carotid artery at the level of the siphons. Collateral blood supply appears from the area of the external carotid arteries (stage 4; Suzuki 1986). The basal net of anastomoses is filled with blood from the vertebral arteries (c)
164
Fig. 3.112a–i Moyamoya disease in a 5-year-old child. The condition
after recurrent strokes in the left hemisphere. Angiogram (AG) of the right internal carotid artery in coronal (a,b) and lateral (c) projections, AG of the left internal carotid artery in coronal (d–f) and later-
Chapter 3
al (g,h) projections, and vertebral AG (i) reveal severe stenosis of the supraclinoid segment of the internal carotid artery bilaterally and presence of a large basal net of anastomoses. There is visualisation of collaterals from the external carotid artery (stage 5; Suzuki 1986)
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.113a–f Moyamoya disease in a 7-year-old child. AG of the
right internal carotid artery in coronal (a) and lateral (b) projections, of the left internal carotid artery in coronal (c) and lateral (d) projections, and vertebral artery (e,f) in coronal projection in the ar-
165
terial and venous phase demonstrate stenosis of the internal carotid artery siphons, absence of intracranial artery visualisation, presence of basal net of anastomoses and collaterals from the external carotid artery (stage 5; Suzuki 1986)
Fig. 3.114a,b Moyamoya disease in a 6-year-old child. 3D TOF MRA in axial and coronal planes (a,b) demonstrate asymmetrical stenosis of the internal carotid artery up to bifurcation and presence of pathologically coiled vessels on the basal brain surface
166
Chapter 3
Fig. 3.115a–f Moyamoya disease in a 3-year-old child. Т2-weighted image (a) and Т1-weighted image (b) reveal multiple bilateral infarctions in the chronic stage. 3D TOF MRA in coronal projection (c) and in MIP reconstruction (d–f) reveal stenosis of supraclinoid seg-
ments of the internal carotid artery bilaterally. The middle cerebral arteries are almost completely absent bilaterally; the net of small vessels is seen around the internal carotid artery siphons
advance stage together with the development of collateral circulation, leads to angiography picture, resembling moyamoya disease. Sometimes the multiple arterial aneurysms of atypical localisation may form. Cerebral angiography in sickle-cell anaemia reveals pathology of the brain arteries in 87% of cases. Angiographic signs of the first stroke can be insignificant, represented by uneven intravascular surface and moderate stenosis. If the examination is performed immediately after stroke onset, then it can reveal the more severe changes in a form of severe stenosis or occlusion of the artery. Subarachnoid haemorrhage is observed in 1–2% in patients with the manifestations of this disease, of which development in the majority of cases is related to the bleeding from arterial aneurysms or widened collateral vessels. It is necessary to emphasise that contrast substances can provoke an exacerbation of disease, and therefore the careful preparation and anaes-
thetic protection of patients during the examination is necessary, and some authors even recommend refraining from contrast administration, even at CT (Barkovich 2000). CT and MRI reveal the ischaemic brain areas with typical changes of density and signal, depending on time passed after stroke onset. Haemorrhages are observed in 20% of cases of brain involvement in patients with sickle-cell anaemia (Balkaran 1992). In some cases, the multiple foci of increased MR signal in T2 and FLAIR modes are revealed in the subcortical white matter of brain hemispheres; these foci are indistinguishable in appearance from multiple sclerosis. MRA is the most safe and undoubtedly highly informative method of the arterial vessel assessment in patients with suspicion of sickle-cell anaemia, as it identifies the sites of stenosis and the developed net of collateral circulation. The carotid arteries are involved more frequently than are arteries of the posterior circulation area.
Cerebrovascular Diseases and Malformations of the Brain
3.6.1.4
Other Congenital Disorders
Ehlers-Danlos (cutis hyperelastica) syndrome, Marfan syndrome and homocystinuria are rare forms of the congenital disorders that can be accompanied by cerebral artery stenosis. These disorders are characterised by the predominant involvement of large arteries, with development of stenosis and formation of parietal thrombosis in them. The venous system can also be involved.
3.6.2 Vasculitides Vasculitides, an acquired pathology of brain vessels that, accompanied by their stenosis or occlusion, consists of the heterogeneous group of relatively rare disorders like vasculitis, collagen diseases (systemic lupus erythematosus, polyarteritis nodosa, etc.), neurosarcoidosis necrotising respiratory (Wegener’s) granulomatosis. They all have primary inflammation of the vascular wall as a manifestation in common. Vasculitides are divided into infectious and non-infectious depending on their aetiology. Various vasculitides classifications exist. One of them is presented below. This one is based on the calibre of the affected cerebral arteries (Table 3.2). Among the infectious causes of the lesion of a vascular wall, the most frequent are bacterial diseases (meningitis), followed by tuberculosis, fungal and viral vasculitides, underlying rheumatic diseases, syphilis and some other forms. As a rule, the lesion of a vascular wall due to bacterial purulent meningitis is a severe complication, and it is more often observed in children. The infectious agent is Haemophilus influenzae. Ischaemic stroke develops in a quarter of all patients. The most frequent finding on the cerebral angiography is artery narrowing at the base of the brain; however, lesions of the distal segments of cerebral arteries are also observed. CT and MRI diagnose multiple strokes, especially in the projection of subcortical structures. Tuberculosis meningitis may be a cause of brain vessel pathology. The development of the generalised arteritis leads to
167
predominant involvement of the initial segments of the large arteries—supraclinoid segments of carotid arteries and M1 segments of MCA. Angiography reveals the stenosis of the above-mentioned arteries; however, in general the signs are not specific. CT and MRA demonstrate narrowing of brain arteries. Contrast enhancement supplements the angiography data by revealing the cranial tuberculomas and the involvement of arachnoid membranes at the base of brain. Various fungal lesions of the CNS can provoke arteritis development. Some of them, for example, actinomycosis, are characterised by direct invasion into that vascular wall, which can lead to its rupture and multiple brain haemorrhages. Angiography reveals non-specific narrowing of the brain arteries. The CT and MRI imaging depends on stage of blood resorption; however, presence of the multiple small foci is typical. In a clinical practice, the lesions of the brain arteries can be observed in certain types of viral encephalitis (more frequently herpetic encephalitis). Syphilis with the CNS involvement typically affects cortical veins and arteries. The MCA area is a common site for syphilitic arteritis. Non-infectious vasculitides are relatively wide group of diseases with different aetiology and different primary mechanism of vascular wall lesion. Polyarteritis nodosa and certain types of collagenosis (systemic lupus erythematosus) belong to a group of diseases with autoimmune mechanisms of vascular wall damage. In the course of disease, immune complexes accumulate in the arterial wall. Other vasculitides include such disorders as cranial (giant cell) arteritis, necrotising respiratory Wegener’s granulomatosis, and primary angiitis of the CNS. For these processes, the mononuclear cell infiltration of the vascular wall, with subsequent narrowing of the affected arteries with thrombosis, is typical. Diseases with vasculitis involving vessel lesions [Kawasaki and Bechçet’s diseases, medicinal angiitis, and some others (Menkes 2000)] are categorised separately. Periarteritis nodosa (Kussmaul’s disease) is a multisystem disease with necrotising lesions of arteries, mainly of the middle calibre. In later stages, the small arteries are also involved.
Table 3.2 Classification of vasculitides by the calibre of the affected cerebral arteries Arteries predominantly affected
Primary vasculitides
Secondary vasculitides
Large cerebral arteries
Takayasu arteritis, cranial (giant cell) arteritis (Horton-Magath-Brown disease)
Aortitis of rheumatic diseases, syphilis of an aorta
Arteries of middle calibre
Classical periarteritis nodosa, Kawasaki’s disease
Infectious origin (including hepatitis B)
Arteries of middle and small calibre
Wegener granulomatosis, Churg-Strauss syndrome, microscopic polyangiitis, idiopathic (essential) angiitis CNS
Vasculitides of rheumatic diseases, systemic lupus erythematosus, xerodermatosis of Sjögren’s syndrome, toxicoallergic medicinal vasculitis, at infectious diseases (including HIV)
Arteries of small calibre (arterioles)
Acute vascular (anaphylactoid, Henoch’s) purpura, essential crioglobulinemia, cutaneous leukoclastic vasculitis
Yatrogenic Vasculitides (including caused by sulphanilamide administration), infectious diseases (including hepatitis C)
168
As a whole, the affliction of vessels of CNS is observed in 45% of cases with the advanced stage of the disease. Typically, multi-organ damage (heart, joints, gastrointestinal tract, eyes) with necrosis of media of a vascular wall leads to formation of microaneurysms (including eye fundus). The latter form is diagnosed in 60–75% of all cases in the acute phase and is characteristic for periarteritis nodosa. Systemic lupus erythematosus (Libman-Sacks disease) is a complex multisystem disease, clinically characterised by multiple syndromes and a progressive course. Typical is systemic damage of the connective tissue and vessels, involving both the central and peripheral nervous systems. Histological examination reveals necrosis and fibrin accumulation in the walls of arterioles, proliferation of the endothelial cells, and thickening of the capillary walls. However, “true” vasculitis is not particular to systemic lupus erythematosus. In general, the vessels are affected in only about 7% of all patients with systemic lupus erythematosus. One clinical sign of CNS affection is stroke. Such strokes are observed in 50% of all patients. They are caused by a combination of several factors, among them heart valve diseases (Libman-Sacks endocarditis) and the increased inclination to formation of thrombi (or decreased thrombolysis), which is linked with the presence of antiphospholipid antibodies in these patients. The spectrum of brain vessel changes revealed by cerebral angiography is relatively wide from none or minimal changes to severe pathology of large arteries, with the formation of fusiform aneurysms. MRI, especially on T2 sequence, detects multiple foci of hyperintense signal in white matter, predominantly of cortical and subcortical locations. Periventricular substance remains rather intact, even in patients with widespread erythematosus of CNS, which helps to differentiate it from multiple sclerosis. The atrophic changes of the brain tissue supplied from the area of the most affected vessels can be found in patients with systemic lupus erythematosus. Cases of multiple subcortical haemorrhages and intense calcification of the basal ganglia structures detected by CT have been reported (Yamamoto 1992). One of the systemic lupus erythematosus characteristics is a presence of antiphospholipid antibodies in the blood. They also may be found in patients with some other diseases, for example, systemic infectious lesion, lung cancer, blood diseases (idiopathic thrombocytopenic purpura, haematological anaemia, etc.), primary immunodeficiency syndrome and also in a subgroup of patients with essential antiphospholipid syndrome. It is observed that venous and/or arterial thromboses are diagnosed in patients with antiphospholipid antibodies in 20–30% of cases. The clinical picture of the disorder may vary from dementia to ischaemic stroke. CT and MRI detect strokes of different age (Figs. 3.116, 3.117). Multiple hyperintensive foci are detected on T2-weighted and FLAIR images in periventricular and subcortical white matter. Brain atrophy can serve as a background for all these changes. Angiography reveals multiple progressive arterial thromboses.
Chapter 3
Primary angiitis of the CNS, known also as non-infectious granulomatous CNS angiitis, may progress quickly and lead to death. This vascular process results in multiple strokes and/ or focal changes in brain tissue, which are easily diagnosed with the use of MRI. Pathological sites are usually multiple, located supratentorially and affect both hemispheres. As a rule, these foci have precise correlation with angiography data. However, not every process that is visible on angiogram can be detected with the use of MRI. Angiography is the most sensitive method, and it is more sensitive than MRT in detecting the vessels lesions, revealing their changes in approximately 85% of cases. However, in 15% of cases the angiography data may be negative (if the lesion is localised at a level of precapillaries). Cranial (giant cell) arteritis (Takayasu arteritis, temporal arteritis) predisposes large-calibre arteries to damage. Histologically, it is characterised by granulomatous infiltration of a vascular wall. Cellular infiltrates contain leucocytes, mast cells, plasmatic cells and huge cells in various combinations with damage of mainly intima. Two subtypes are defined within the limits of disease and temporal arteritis (HortonMagath–Brown syndrome). Temporal arteritis mainly affects large arteries such as the aorta and its branches, especially the pulmonary arteries. Angiographic signs of disease are occlusion, stenosis, blood flow heterogeneity, ectatic widening or aneurysm-like out-pouching. Temporal arteritis is characterised by system lesion with multiple stenoses, especially of the external carotid artery branches (superficial temporal artery, etc.). Granulomatous angiitis (idiopathic, neurosarcoidosis, etc.) encompasses rare vasculitis forms, with lesions in the arteries of middle and small calibres. Their aetiology is not clearly known, and they often are found out in combination with tumours and CNS infections. There is essential angiitis with isolated CNS damage. Diagnostic findings are not specific. MRI detects multiple foci of increased signal in white matter of brain; digital subtraction angiography (DSA) identifies segmental stenosis of cranial arteries. Neurosarcoidosis is accompanied by CNS involvement in about 5% of all cases. In the cerebral arteries, severe other infiltration of the artery wall, without necrosis, is observed. Lesions of meningeal arteries are also observed. DSA detects nonspecific stenosis of the arteries. MRI with contrast enhancement identifies another manifestations of brain damage at the site of sarcoidosis. (As a rule, it causes intense contrast accumulation in the leptomeningeal membranes on the brain base.) Necrotising respiratory (Wegener’s) granulomatosis is a systemic disease with a chronic course that is characterised by the development of focal granulomatous arteritis of vessels of middle and small calibres (branches of the pulmonary and the renal arteries and of other internal organs). The involvement of CNS is observed in 15–30% of cases. Angiographic findings are not specific, and they include the sites of heterogeneity of the vascular wall and vessel occlusion.
Cerebrovascular Diseases and Malformations of the Brain
169
Fig. 3.116a–c Ischaemic infarction in a patient with antiphospholipid syndrome. CT (a) and MRI in FLAIR (b) and DWI (c) demonstrate the large area of ischaemia in the posterior cerebral artery area
Fig. 3.117a–f Multiple ischaemic infarctions in a patient with antiphospholipid syndrome. Т2-weighted image (a), Т1-weighted image (b), Т1 after contrast enhancement (c) and DWI (d–f) demonstrate multiple ischaemic lesions that occurred at different times in cortical areas of the left and the right posterior frontal regions
170
Fig. 3.118a–i Ischaemic infarction in the middle cerebral artery after Imovan overdose. Cerebral АG in coronal (a,b) and lateral (c) projections demonstrates the cloud-shaped shadow in the right temporoparietal region, vividly seen in the capillary phase of AG. On CT (d) without and with contrast enhancement (e), the large areas of pathological accumulation of contrast in the basal ganglia and the
Chapter 3
right temporal lobe are revealed. CTA (f) demonstrates pathological contrast enhancement of the putamen and the head of caudate nucleus in the arterial phase of the study. Т2-weighted image (g), Т1-weighted image (h) and Т1 with contrast enhancement (i): there is a large area of ischaemic brain damage with focal haemorrhagic component and marked pathological contrast enhancement
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.119a–d Schematic representation of variants of internal carotid artery damage in fibromuscular dysplasia. a normal, b narrowing and elongation of the internal carotid artery, c “bamboo-stick” strangulations, d stage of aneurismal ectatic protrusions along with lumen stenosis (Osborn 1999)
Rare forms of vasculitis exist; lesions of cranial and cervical arteries can be one of the manifestations of diseases such
Fig. 3.120a,b Fibromuscular dysplasia in different patients
171
as Kawasaki’s disease, thromboangiitis olbiterans (Buerger’s disease), BehÇet’s disease, and iatrogenic arteritis. Kawasaki’s disease (mucocutaneous lymph node syndrome) is characterised by multiple lesions of the middle-calibre arteries and formation of fusiform elongated ectasis and aneurysm-like out-pouching of the intracranial vessels. Thromboangiitis olbiterans belongs to the group of essential disorders with recurrent clinical course and segmental obliteration of vessels of middle and small calibres (including veins). The vessels of lower extremities are mainly affected; however, in some cases the thromboses of cortical veins are observed. There is a high correlation between the disease and smoking. Behçet’s disease is a rare form of system vasculitis that involves both, the arterial and venous systems. Aetiology as a whole is still not known; dependence on the immune status of an organism is supposed. Aphthous ulcerations in oral cavity and genitals, uveitis and cutaneous lesions are observed. Neural system involvement is reported in 10–45% of cases. Diagnosis is mainly based on MRI data. CT is not an adequate diagnostic tool for depicting this disease. T2-weighted imaging reveals the multiple foci of signal increase in a projection of a brainstem, diencephalon and white matter of the brain hemispheres. The focal lesion is thought to be related to the arterial occlusions, formation of aneurysms and vein thrombosis. Iatrogenic arteritis. Some medicines can cause this vasculitis. Their frequency has recently rapidly increased with the greater availability of medical products. The basic mechanism is the direct toxic trauma of a vascular wall or hyperergic reaction to the admixture in drugs. It is necessary to remember that vessel lesions can be caused by accessible medicines (for example, amphetamine, pseudoephedrine, oral contraceptives), as well as illegal drugs (cocaine, heroin, etc.). The spectrum of vascular changes includes vasospasm, stenosis and occlusion and as consequence, and epileptic seizures, ischaemic attacks and stroke (Fig. 3.118). Vascular wall necrosis with the subsequent haemorrhage forms in severe cases, which can lead to death. Other vascular lesions and stroke causes include rare but possible non-atheromatous, non-inflammatory and nontraumatic diseases, with the development of stenosis and occlusion of brain arteries (fibromuscular dysplasia, vasculopathy due to malformations and tumours, radiation vasculopathy and spontaneous rupture or dissection of arteries, CO poisoning, etc.). Fibromuscular dysplasia belongs to the group vasculopathies with high risk of stroke development.
172
Chapter 3
The aetiology is unknown. The widening of arterial wall with typical “string-of-pearls” appearance, according to the direct angiography data, occurs due to non-atheromatous fibrosis and thickening of the muscular layer. The most common locations are extracranial segments of carotid and vertebral arteries (Figs. 3.119, 3.120). The ICA is affected in three quarters of all cases; the involvement of a vertebral artery is no more than 25% of all cases. The most proximal segments of ICA and bifurcation remain relatively intact. One of the typical signs is bilateral lesions (up to 75% of all observations). Often the disease accompanies cranial saccular aneurysms. The rupture of the aneurysm wall is a rare but severe complication. Radiation vasculopathy. Radiation can cause structural changes in the vascular wall, such as endothelium degeneration, intima fibrosis and fibroplastic proliferation of middle layer. The progressive development of focal atherosclerosis, microangiopathy with calcifications and progressive occlusion of large arteries can develop because of these changes. Radiation may be considered as a direct cause for stroke months and years after treatment initiation. In rare cases, the occlusion of extracranial segments of the ICA is seen after neck radiation. Cerebrovascular lesions of the ICA and its main branches can be seen in patients who underwent radiation treatment with the beam directed to the base of brain. Brain MRI can additionally depict the areas of post-radiation necrosis and diffuse gliosis.
3.7
Thrombosis of the Venous Sinuses
Venous thrombosis belongs to a rare disease group that cannot be easily diagnosed, because with a severe clinical condition, the clinical manifestations have non-specific character. In children, thrombosis of venous sinuses leads to less intense neurological symptoms and is self-limiting. In adults, sinus occlusion has a more aggressive course, and the prognosis is often poor (Shroff and de Veber 2003; Lee and ter Brugge 2003; Berenstein et al. 2003). Thrombosis of the venous sinuses is observed in approximately 1% of all stroke cases. Thrombosis more often affects the superior sagittal sinus, then the transverse, sigmoid and cavernous sinuses. The internal brain veins, vein of Galen and sinus rectus are rarely affected. The aetiology of thrombosis of venous sinuses is diverse: • Non-infectious –– Essential (up to 25%) –– Pregnancy and delivery –– Dehydratation (the most frequent reason in children) –– Oral contraceptives –– Trauma –– Tumour (sinus invasion, systemic forms of tumours, paraneoplastic syndrome) –– Blood disorders (polycythemia, the increased blood coagulability, sickle-cell anaemia, Herrick’s anaemia, leukaemia, etc.) –– Changes due to malformations and dural arteriovenous fistulas
• Infectious –– Meningitis –– Inflammation in additional sinuses of the skull (sphenoiditis, mastoiditis, etc.)
–– Orbital cellulitis –– Subdural empyema –– Encephalitis –– Ulcerative colitis (Crohn’s disease) In the course of the disease, the majority of patients complain of headache, changes of mental faculties, vision impairments and epileptic seizures which, in some cases, can progress to come and lead to death. Brain oedema develops in the early stage of vein thrombosis; however, it can be reversed in cases of early beginning of therapy. This reversal, however, is possible only when correct diagnosis is made. The right therapy cannot only save the patient’s life, but in some cases, also obviate the development of severe complications as haemorrhagic infarction. Cerebral angiography can detect the absence of blood flow through affected sinus in cases of full thrombosis. Dilatation of cortical veins and the formation of additional branches of venous outflow from the cranial cavity may be observed in case of chronic process. CT without contrast enhancement reveals hypodense area (oedema) in brain tissue; the location of this area depends on the level of thrombosis: in frontoparietal areas in cases of superior sagittal sinus thrombosis, and in the basal ganglia in cases of the sinus rectus thrombosis. This area tends to remain stable during the first days of disease onset. Imaging of a clot inside of the dural sinus is possible only with the help of intravenous contrast enhancement, when the area with density lower than the density of contrast medium can be visualised on the background of a bright, functioning sinus. Some authors even describe a typical symptom for the thrombus presence, the so-called delta sign, seen as a dense triangle (from the hypointense clot) within the superior sagittal sinus. Imaging of haemorrhagic infarction, the complication of venous thrombosis, is an important diagnostic practice in CT imaging. It is believed that presence of the severe oedema and haemorrhages correlate with poor prognosis. MRI is a more effective method in diagnosis of a venous thrombosis than CT. MRI signs of a thrombosis depend on the disease stage. In the acute phase, MRI visualises the blood clot within the lumen of the vessel as a focus isointense, with the brain tissue in T1 mode, and as hyperintense focus in T2 mode (Fig. 3.121). In the subacute stage, the clot is characterised by increased MR signal in all modes, and it can be especially clearly diagnosed in sagittal T1-weighted imaging (in cases of superior sagittal sinus thrombosis). In this period, the most appropriate diagnostic is the MRI in T1 mode in parallel and in perpendicular projections towards the sinus (Fig. 3.121). In the chronic stage, the clot brightness in T1 mode decreases; this is related to partial fibrosis and possible recanalisation at the site of thrombosis. Additional information can be obtained with the use of intravenous contrast administration (Figs. 3.122, 3.123). The additional venues of blood outflow
Cerebrovascular Diseases and Malformations of the Brain
173 Fig. 3.121a,b Partial thrombosis of the right jugular vein. Т2-weighted image (a) and Т1-weighted image (b) with contrast enhancement demonstrate a thrombus within a lumen of initial segment of the right jugular vein (arrow)
Fig. 3.122a–c Thrombosis of the right transversal and sigmoid sinuses. Т2-weighted image (a) and Т1-weighted image with contrast enhancement in axial (b) and sagittal planes (c). There is a thrombus in the lumen of these sinuses (arrow)
Fig. 3.123a–c Thrombosis of sinus rectus and the superior sagittal
sinus, with partial recanalisation. Т1-weighted image in sagittal projection weighted image-contrast enhancement (a) reveals a thrombus in the superior sagittal sinus, sinus rectus and a mild thrombus
in the vein of Galen. 2D TOF (b) and 3D PC (c) regimes: there is a partial visualisation of the superior sagittal sinus in its posterior third (recanalisation). Prominent development of venous collateral blood supply in skull cavity is detected
174
Chapter 3
Cerebrovascular Diseases and Malformations of the Brain
175
Fig. 3.124a–l Thrombosis of the superior sagittal sinus, sinus rectus and the left transversal sinus. Т2-weighted image (a) and Т1weighted image (b): there is an area of heterogeneous signal change in the thalamus. After contrast enhancement (c), peripheral contrast accumulation resembling a cerebral tumour is seen. Sinus rectus produces a hyperintense signal on MRI—typical for thrombosis. A month later: MRI in Т2-weighted imaging (d), Т1-weighted imaging
(e) and FLAIR (f) reveal hyperintense signal in the left sigmoid sinus; residual haemorrhagic changes of pulvinar thalami are seen (g). In sagittal projection, the sinus rectus is visualised in a few separate segments (h). After contrast enhancement (i–k), the signal from the left sigmoid and transversal sinuses becomes more vivid. 2D TOF MRA in axial projection (l) does not depict the left transversal and sigmoid sinuses
can be formed on the base of neighbouring brain veins. The local oedema of brain tissue is better visualised in T2-weighted imaging and FLAIR, giving better indication as to the location of the thrombosis of vein or sinus. Thrombosis of the deep venous system of the brain occurs rarely in comparison with thrombosis of the large dural sinuses. The lesion of deep veins in children is observed more often than in adults. The bilateral involvement of basal ganglia is typical for the MRI picture. Basal ganglia are enlarged, and they have an increased MR signal on T2 and FLAIR sequences, while the third ventricle is narrowed (Fig. 3.124). Currently, MRA replaces direct cerebral angiography in diagnosis of sinus thrombosis. The most used techniques are 2D TOF and 2D PC (Fig. 3.125). 3D TOF technique is not effective due to its lesser sensitivity to slow blood flow. To make a diagnosis, it is necessary to discover the changes in MR characteristics of venous sinus in a routine examination and to establish the absence of the sinus in contrast venography (the vein system of the brain is greatly variable). As a rule, the prognosis for patients with sinus thrombosis is poor. The residual neurological deficiency depends on strokes localisation, the degree of sinus revascularisation, the reserves of collateral circulation and the formation of the additional venues for vein blood outflow. Hydrocephalus and— as a consequence—loss of vision, are frequent and delayed complications in patients who have suffered sinus thrombosis (Preter 1996).
3.8
Haemorrhagic Infarction
The term haemorrhagic infarction covers a wide spectrum of haemorrhages, from small petechial haemorrhage up to large cerebral ones, irrespective of source and location of bleeding. Unlike haemorrhages in patients with hypertension, initial bleeding is not typical for haemorrhagic infarctions, and they are characterised by the haemorrhagic impregnation that follows the ischaemic damage. Haemorrhagic transformation is observed more frequently in patients with strokes due to cardiac embolism than in patients with a stroke of atherothrombotic origin. The following position is one of the widely accepted standpoints in the study of haemorrhagic infarction. Embolism of the brain arteries is a starting point of haemorrhagic infarction development. Embolism leads to occlusion of the cerebral artery, with the subsequent development of ischaemic damage of the brain tissue. Then the emboli undergo lysis, the circulation is restored and blood cells start to infiltrate the brain tissue through the damaged endothelium of the vessels. Thus, a so-called haemorrhagic transformation of the ischaemic area occurs 6–12 h after stroke onset, peaking by approximately 48 h. Sometimes, however, it can happen after 1 week or more since the stroke onset (so-called late haemorrhagic transformation), when the process of restoration of collateral circulation is taking place. However, now this viewpoint is being challenged. Some studies (both clinical and experimental) have demonstrated that the blood flow through the artery with occlusion is not restored in the process of haemorrhagic infarction development (Horowitz 1991; Ogata 1989).
176
Fig. 3.125a–f Thrombosis of the superior sagittal sinus and sinus
rectus. Т1 images in axial (a) and sagittal (b) planes do not reveal a typically hypointense signal of blood flow in the mentioned venous
It is widely believed that the large infarctions are more inclined towards haemorrhagic transformation than small ones are. Approximately about 25% of all large infarctions have the signs of haemorrhagic transformation. In fact, petechial haemorrhages have been observed in the overwhelming number of strokes, and thus the difference between ischaemic and haemorrhagic infarction is small. The results of autopsies demonstrate that about 70% of all infarctions have haemorrhagic foci. However, according to neuroimaging, this percentage is much lower. Therefore, based on CT, the share of haemorrhagic infarction is about 5–15% of all infarctions. MRI shows the higher percentage. While haemorrhagic infarctions can be located anywhere, they are more often found in the basal ganglia and cortex. CT and MRI signs of haemorrhagic infarctions can vary; however, generally, they resemble the dynamics observed in intracranial haemorrhages. On T2-weighted imaging, acute haemorrhagic infarction in the cortex appears as an area of decreased signal intensity—around the focus, the area of oe-
Chapter 3
collectors. 2D TOF (c–e) and 3D PC (f) MRA demonstrate partial visualisation of the posterior portions of the sagittal sinus. The transversal sinus to the right and sinus rectus are not visualised
dema can be visualised (Fig. 3.126). On T1-weighted imaging, the blood cannot be easily distinguished from the brain tissue. On CT, the acute haemorrhage has high roentgen density (Fig. 3.127). The subacute infarction has increased signal on T1- and T2-weighted tomograms and becomes isodense on the standard CT image (Fig. 3.128). In the chronic stage, the MRI changes correspond with encephalomalacia.
3.9
Intracerebral Haemorrhages
According to the WHO classification, all haemorrhages are divided into cerebral, subarachnoid subdural and intraventricular. Some authors itemise by splitting the cranial supratentorial haemorrhages into lateral (outside the internal capsule), lobar, medial (medially from the internal capsule) and mixed, while the subtentorial haemorrhages are divided into the haemorrhages in cerebellum or in brainstem (up to 12% of all haemorrhages), and all membranous are split into subarach-
Cerebrovascular Diseases and Malformations of the Brain
177
Fig. 3.126a–c Haemorrhagic infarction of the left thalamus. Т2-weighted imaging (a) and Т1-weighted imaging (b), and FLAIR (c), reveal a
hypointense lesion in the left basal ganglia surrounded by perifocal oedema (day 1)
Fig. 3.127a–c Acute haemorrhagic infarction in the left frontotemporal region with rupture into the ventricular system. CT images (a–c) reveal a large intracerebral haemorrhage surrounded by perifocal oedema, with severe dislocation of ventricles
178
Fig. 3.128a–i Haemorrhagic infarction of the posterior frontotemporal region. CT images on day 3 reveal a heterogeneous area of density change, with foci of increased attenuation in the central zone (haemorrhage) without (a,b) and after (c,d) contrast enhancement. Т2-weighted image (e) and Т1-weighted image (f) and Т1 after contrast enhancement (g) on day 1 reveal a heterogeneous signal change on
Chapter 3
Т2-weighted imaging, which is hypointense on Т1-weighted imaging. The affected area does not show contrast enhancement. Т2-weighted imaging (h) and Т1-weighted imaging (i) on day 3; there is marked increase in signal intensity of subacute haemorrhage on Т1
Cerebrovascular Diseases and Malformations of the Brain
179
Table 3.3 Causes of non-traumatic cerebral haemorrhages Frequent
Rare
Hypertension
Thrombosis of venous sinuses (venous infarction)
Atherosclerosis of the brain vessels
Eclampsia
Arterial aneurysm rupture
Moyamoya disease
The rupture of AVM, cavernoma (cavernous angioma), dural arteriovenous fistula
Encephalitis
Amyloid angiopathy, coagulopathy due to anticoagulants and thrombolytic drugs administration
Condition after radiation therapy
Thromboembolism (heart diseases: endocarditis, congenital defects, long operations on heart)
Hereditary haemorrhagic telangiectasia, Rendu-Osler-Weber disease
Haemorrhagic infarction
Sturge-Weber-Krabbe syndrome
Haemorrhages in a tumour (metastasis, glioblastoma, etc.)
Vasculitis and arteritis
Alcoholism
Abscess
Premature delivery
noid, subdural and epidural haemorrhages (Vereshchagin et al. 1986; Okazaki 1989). Based on experience of examinations of patients with cranial haemorrhages admitted to the Burdenko Institute of Neurosurgery, identification of the aetiology is important in diagnostics. The two main reasons for haemorrhage are injury and causes of non-traumatic origin. The latter ones can be of different causes; more often, it is arterial hypertension, haemorrhages, rupture of saccular aneurysms, atrioventricular malformations (AVM), haemorrhage due to tumour, amyloid angiopathy and coagulopathy. Rarer reasons include vasculitis, venous infarction, eclampsia and encephalitis. Table 3.3 lists the main causes of cerebral haemorrhage. Usually haemorrhages have acute onset, they are massive and accompanied by intense oedema and mortality reaches 25% by the end of the first day and 50% by the end of the first month. As a whole, haemorrhages of non-traumatic origin constitute up to about 20% of all strokes. In younger people, the majority of haemorrhages occur due to arterial aneurysm rupture or AVMs, and their prevailing locations are subcortical and subarachnoid. For those aged 40–70 years, the main reason is hypertension, and the primary locations of haemorrhages are basal ganglia and temporal lobes of the brain. In cases of lobar, hemispheric haemorrhages in elderly patients, it is necessary to first consider amyloid angiopathy as the reason, and then atherosclerotic changes in the brain vessels. Clinical presentations of spontaneous intracranial haemorrhage (SICH) are diverse. Subarachnoid haemorrhages characterised by an acute and intense headache in combination with a meningeal syndrome and the complete recovery of the neurological deficit is possible. For SICH, acute headache
is less typical; however, the neurological deficiency is more severe and may remain for a long time after stroke. In general, the size and the location of the haemorrhage determines the severity of the patient’s state and focal neurological signs. Hemiparesis, sensory loss and speech disturbance prevail in cases of subcortical location. Deep haemorrhages lead to the secondary brainstem symptoms caused by brain dislocation and tentorial herniation. Stem haemorrhages are accompanied by severe neurological pathology, with impairment of consciousness and vital functions.
3.9.1 Course of Intracerebral Haemorrhage as Determined by CT and MRI Data Detection of a haemorrhage is the major task of each neuroimaging method. However, haemorrhage location, in addition to its anatomic aspect, has other important characteristics. Haemorrhages in the subarachnoid space resolve rather quickly, and they usually do not leave special traces on CТ performed after 1–2 weeks. Intracranial haemorrhages take much longer to resolve; they can be detected even several months after the stroke onset. The blood outside the vessel’s system undergoes liquefaction and resorption. This process follows certain stages, which are reflected by typical changes of the haemorrhage density on CT data and changes in signal intensity in MRI sequences. Knowledge about this dynamic permits making estimations about time passed since stroke onset on the basis of CT and MRI data. Based on time, all haemorrhages can be subdivided into the following stages: superacute (first 4 h), acute (up to 3 days),
180
Fig. 3.129a–i The follow-up observation of haemorrhage in the frontal lobe, with rupture into the ventricular system due to splitting of the sack aneurysm. CT: day 1 (a), day 3 (b), day 12 (c), day 15 (d), day 20 (e), 2 months (f), 3 months (g), 6 months (h) and 1
Chapter 3
year (i). Gradual resorption of the intracerebral and intraventricular haemorrhage with further development of encephalomalacia and ventriculomegaly is seen
Cerebrovascular Diseases and Malformations of the Brain
181
Fig. 3.130a–c Acute haemorrhagic infarction in the right parieto-occipital region (acute stage). CТ imaging (a–c) reveals a markedly hyper-
dense with small hypodense halo
subacute (3–14 days), and chronic (more than 14 days). Some authors split the subacute stage into early (3–7 days) and late (1 week to 1 month), and after 1 month, a haemorrhage is considered to be in the chronic stage.
3.9.1.1
Superacute and Acute Stages
According to experience with use of neuroimaging, CT with its clear visualisation of blood both in brain tissue and subarachnoid space remains the method of choice of early cerebral haemorrhage diagnosis. The acute extravasated blood has hypodense on CT scans (40–90 HU) (Figs. 3.129, 3.130). The reason behind this phenomenon is the increased concentration of protein in the haemoglobin molecule. It is noteworthy that in the first hours after a haemorrhage, the hematoma’s density can reach 60–80 HU. This happens because of the creation of the net of fibrin thread and globin molecules and the increase of the hematocrit to 90% (onset of retraction). In the larger haemorrhages in the superacute and acute stages on СТ, a horizontal level liquid–liquid junction may appear. This effect is called the “haematocrit effect”. The area with higher density represents cell elements that have undergone sedimentation: above them are located less dense substances—basically blood plasma. Contrast enhancement on the haemorrhage periphery usually does not appear during the acute phase. MRI. Changes of MR signal observed in the course of haemorrhage retraction are of a more complex and difficult character. Prior to describing the typical changes of the haemorrhage image on the MRI sequences, the basis of MR relaxation mechanisms, implicated in the process of haemoglobin oxidation, must be addressed. First, the structure of haemoglobin and its various combinations are discussed. Haemoglobin is involved in oxygen binding in the lungs: the haeme groups become oxygen saturated, and the haemo-
globin subsequently is transferred to tissues with low partial oxygen pressure. Then, the oxygen dissociates from the haeme and saturates the tissues. For oxygen transfer, the haeme iron component must be in the Fe2+ form. Iron in haemoglobin forms an octahedron structure with six ligands. Their interaction with the central metal leads to pair formations between the six external electrons of d orbital of the two-valency iron; therefore, the magnetic moment of molecules equals zero, and blood saturated with oxygen is diamagnetic. The loss of molecular oxygen changes the spatial structure of two-valency iron in haeme to a five-ligand system of dioxyhaemoglobin. In this system, the six d electrons redistribute, leaving four uncoupled electrons with parallel spins. The molecule now has its own magnetic moment. Therefore, dioxyhaemoglobin is paramagnetic. However, the hydrophobic sites of the globin protein protect the paramagnetic iron from water molecules. This leads to a decrease of its paramagnetic effect. The first studies, led by Gomori et al. in 1985, revealed that consecutive changes of signal intensity in a haemorrhage reflect both shortening of T1 and lengthening of T2 relaxation time. Within the first minutes or hours after a haemorrhage, only oxyhaemoglobin is present. Due to its diamagnetic nature, it does not have significant influence on the T1 and T2 relaxation times. During the superacute stage, haemorrhage is usually isointense in comparison with grey matter on T1-weighted tomograms and hyperintense on T2-weighted images, related mainly to the high concentration of water and protein in the haemorrhage (Fig. 3.131). Therefore, a haemorrhage less than 12 h old looks like a congestion of liquid on tomograms on T2-weighted imaging and thus cannot be distinguished from CSF in the subarachnoid space. In the acute stage of haemorrhage, dioxyhaemoglobin remains within the cells of the intact erythrocytes and reveals itself as a low signal on T2-weighted images. This happens be-
182
Chapter 3
Fig. 3.131a–c Acute intracerebral haemorrhage (15 hours). Т2-weighted image (a) and Т1-weighted images (b,c): fresh haemorrhage is isointense on Т1
cause of a difference in magnetic susceptibility inside erythrocytes and in the diamagnetic intercellular liquid, which leads to local heterogeneity of the magnetic field. Such heterogeneities declare themselves in proton out-phasing with the shortened T2 time, and in the decreasing of signal intensity on T2weighted imaging and especially T2*-weighted imaging. These changes have no special influence on the T1 relaxation time, and therefore acute intracerebral haemorrhage on T1-weighted imaging remains isointense with brain tissue (Figs. 3.132, 3.133). The above-mentioned effect of a magnetic susceptibility change (in the presence of dioxyhaemoglobin) is proportional to a square of the magnetic field strength; therefore, on lowmagnetic field MR systems (with magnetic field of up to 0.2 T), the decrease in the MR signal on T2-weighted imaging is not so intensive and can hardly be visualised. In the acute phase, the perifocal oedema expands quickly around the intracerebral haemorrhage. On T2-weighted images, it may be well defined as an area of increased MR signal surrounding the hypointense acute haemorrhage. On tomograms in T1 mode, the oedema is insufficiently differentiated from the brain tissue.
3.9.1.2
Subacute Stage of Haemorrhage
In this stage, the metabolic processes that support the stability of haemoglobin are disrupted, and this leads to its oxidation to methaemoglobin. Iron goes to three-valency condition and has five not-coupled d electrons. The erythrocytes undergo lysis, which starts from periphery to the centre of haemorrhage. On CT images in the subacute stage, haemorrhage density gradually decreases. First, on the periphery, the zone of density decreases due to globulin molecule disintegration and vasogenic oedema (Fig. 3.134). Then, density decrease extends on the central parts of a haematoma so that by the end of subacute phase, the haemorrhage becomes iso- or even hypodense.
Is is noteworthy that decrease in haemorrhage density in this stage is not accompanied by the mass effect reduction; the latter is manifests as an caused by the intense perifocal oedema that manifests as an area of low density around the haemorrhage. By the end of the first week, on CT with contrast enhancement, the area of additional contrast accumulation starts to appear around the haemorrhage due to the formation of capsule with neogenic vessels. The appearance of methaemoglobin, which has intense paramagnetic effect on the МRI, leads to predominant shortening of T1 relaxation time and corresponding increase of МR signal intensity on T1-weighted imaging. As on CТ, the process of methaemoglobin formation starts from the periphery and then gradually (and slowly) goes towards the centre. The longer the dioxyhaemoglobin is retained inside the erythrocytes in the internal areas of haemorrhage, the longer remains the signal decrease from its centre. In the early subacute stage, methaemoglobin is located inside the cells and characterised by short T1 and T2 relaxation times. On the MR tomograms in T2 mode by this time (the first 3–7 days), the haemorrhage still mainly remains hypodense. In T1 mode, the methaemoglobin influence manifests by way of the occurrence of a hyperintense MR signal on the haemorrhage periphery (Figs. 3.135, 3.136). In the late subacute stage (7–14 days), the ongoing haemolysis leads to release of methaemoglobin from cells. Free methaemoglobin has short T1 and long T2 relaxation times, and therefore the haematoma becomes hyperintensy on T1and T2-weighted images (Figs. 3.137–3.139).
3.9.1.3
Chronic Stage of Haemorrhage
At the end of the subacute and the beginning of a chronic stage, an area of low signal starts to take shape on the periphery of a haemorrhage, caused by iron deposition in the hydrophobic centres of the ferritin, the main ferruginous protein, and in the macrophages around the bleeding zone, in the form
Cerebrovascular Diseases and Malformations of the Brain
183
Fig. 3.132a–c Acute intracerebral haemorrhage (day 2). Т2-weighted image (a) and Т1-weighted images (b,c) demonstrate the area of hyperintensity of acute haemorrhage in the right temporal lobe
Fig. 3.133a,b Acute intracerebral haemorrhage in the temporal lobe. Т2-weighted image (a) and Т1-weighted image (b) on day 3 demonstrate an area of haemorrhage into the deep structures of the temporal lobe; the haemorrhage is surrounded by perifocal oedema
184
Chapter 3
Fig. 3.134a–c The follow-up observation of haemorrhage in the right temporal lobe by CТ: day 1 (a), day 3 (b) and day 25 (c). Gradual lysis
of haemorrhage, with changing of its density from high to low, is observed
Fig. 3.135a–c Subacute intracerebral haemorrhage in the right temporal lobe. Т1-weighted images (a,b) and Т2-weighted image (b) reveal a large haemorrhage, which causes dislocation of ventricular system, with typical initial formation of methaemoglobin of periphery (hyperintensity on Т1-weighted imaging)
Fig. 3.136a,b Subacute cerebellar haemorrhage. Т2-weighted image (a) and Т1-weighted image (b) reveal the intracerebellar haemorrhage.
Hyperintensity on Т1 is a sign of entering the subacute stage
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.137a–f Intracerebral haemorrhages. Case 1. CT reveals a large hypodense area in the right temporal lobe, with dislocation of ventricles (a), Т1-weighted image (b) and Т2-weighted image (c) reveal a homogeneously hyperintense signal of subacute haemorrhage. Case
185
2. Subacute intracerebral haemorrhages in the left temporal lobe: Т1weighted image (d), Т2-weighted image (e) and Т2*-weighted image (f) reveal a hypointense signal on the periphery of the haemorrhage, typical for initial haemosiderin formation (entering a chronic stage)
186
Fig. 3.138a–f Late subacute intracerebral haemorrhage in the left temporal lobe. On a series of CT scans on day 9 (a,b) there is an area of heterogeneous density change in the left temporal lobe, with hyperdense signal in the centre and hypodense signal on the haem-
Chapter 3
orrhage periphery. MRI (day 20) Т2-weighted image (c), Т1-weighted image (d) and DWI (f b = 500, e b = 1,000) reveal a typical high signal of haemorrhage in all sequences. Perifocal oedema has decreased compared with previous CT scans
Fig 3.139a–c Late subacute intracerebral haemorrhage in the left temporal lobe. Т2-weighted imaging (a), Т1-weighted imaging (b) and
FLAIR in coronal plane (c) reveal a mass of heterogeneous structure, and peripheral hyperintensity on Т2 and Т1 caused by extracellular haemoglobin diluted in the liquid component of the haemorrhage
Cerebrovascular Diseases and Malformations of the Brain
187
Fig. 3.140a–c Chronic haemorrhage (day 30) in the left temporal lobe. Т1-weighted imaging (a), Т2-weighted imaging (b) and DWI (c b = 500) demonstrate a homogeneous hyperintensity. Peripheral hypointensity is explained by initial haemosiderin deposition
Fig. 3.141a–f A follow-up observation of a subacute intracerebral
haemorrhage in the left temporal lobe. Т1-weighted imaging (a,b) and Т2-weighted imaging (b) on day 15 after onset show a large in-
tracerebral haemorrhage with initial formation of haemosiderin rim. MRI 2 months later reveals lysis of methaemoglobin within the haemorrhage cavity and perifocal oedema (d–f)
188
Chapter 3
Fig. 3.142a–c Chronic haemorrhage of the left temporobasal region. CT images before (a,b) and after (c) contrast enhancement reveal a
cyst in the left temporal lobe. A haemorrhage capsule shows no contrast enhancement. The haemorrhage simulates a CT picture of a cystic glial tumour
of haemosiderin. The central part of a haemorrhage is represented by the freely dissolved methaemoglobin. Around this time, the centre of the haemorrhage has increased МRI signal in all modes, while the degree of the signal from the periphery is decreased. By this time, as a rule, the oedema is significantly diminished or entirely disappears (Figs. 3.140, 3.141). Accumulation of haemosiderin in macrophages remains for a long time, and therefore the discovery of the above-mentioned findings on the MR images is a sign of an old haemorrhage. In the late chronic stage, the process of resorption of liquid and proteins is going to conclude with the formation of the brain tissue defect. The hypodense area at the site of former haemorrhage is visualised on CT. It has the density close to those of CSF in the lateral ventricle (Fig. 3.142). The finding of new areas of increased density can point to a repeated haemorrhage (usually from the capsule’s vessels). Contrast enhancement on a haemorrhage periphery can remain for a relatively long time (up to 6 months, according to several authors). The outcome of a haemorrhage can be the focus of low density (37%), slit-like defect (up to 25%) and calcinated area(s). In the remaining cases, CT cannot identify any residual changes in the brain tissue at the site of haemorrhage. Unlike CТ, MRI, especially in T2 and T2* modes, is more sensitive in the assessment of past intracerebral haemorrhage (Figs. 3.143, 3.144). The area of the decreased MR signal intensity, represented by the presence of haemosiderin and fer-
ritin in macrophages, typically is visualised for a long time (sometimes it takes years) around a haemorrhage periphery. On T1- and T2-weighted images, brain tissue defects of various form and shape appear at the site of intracerebral haemorrhage. As a result, the neighbouring part of the ventricular system dilates. Sometimes, in cases when the blood cuts its way into the ventricular system, it is possible to detect the site of ependymal defect.
3.10 Extracerebral Non-traumatic Haemorrhages Subarachnoid haemorrhages from aneurysms and AVM consist of about 90% of all non-traumatic haemorrhages. Despite all the MRI potential, CT remains the basic method in diagnosis of this disease. In the acute stage, the blood has increased density (Fig. 3.145). While the majority of arterial aneurysms are localised in the area of the cerebral arterial circle and the initial segments of MCAs, the blood first accumulates in the basal cisterns and in the Sylvian fissure. Then, it extends along the convex subarachnoid space, and into the interhemispheric fissure. CT performed in the early period, before the blood evenly distributes in the subarachnoid space, pinpoints the aneurysm location. The blood found in the chiasmal cisterns and interhemispheric fissure can be a sign of haemorrhage from the aneurysm of the anterior cerebral artery or anterior communicating artery.
Cerebrovascular Diseases and Malformations of the Brain
189
Fig. 3.143a–c Chronic intracerebral haemorrhage of the left temporal region (6 months after onset). Т2-weighted image (a), Т1-weighted image (b) and Т2*-weighted image (c) demonstrate a CSF-filled cavity in the external capsule; peripheral hypointense signal on Т2- and Т2*weighted images indicates of haemosiderin deposition
Fig. 3.144a–c Consequences of haemorrhage into central gyri, leftwards. The Т2-weighted image (a) and Т1-weighted images (b,c) reveal
the area of heterogeneous MR signal change, with residual methaemoglobin (hyperintense on Т1) and haemosiderin (hypointense on Т2) deposits
190
Chapter 3
Fig. 3.145a–f CT in acute subarachnoid haemorrhage due to rupture of aneurysm of the anterior cerebral–anterior communicating artery.
Case 1: (a–c), case 2: (d–f). A good deal of blood is seen at the base of middle and anterior cranial fossae
Blood presence in the Sylvian fissure can point to an aneurysm of the supraclinoid segment of the ICA, the MCA or the posterior communicating artery. The more time that has passed since the haemorrhage onset, the less informative the CT examination becomes for the confirmation of the subarachnoid haemorrhage diagnosis. After 1 week, the blood remains are revealed in less than half of all patients, and the presence of high density in the subarachnoid space after 7–10 days suggests repeated or new haemorrhage. Opinions on the efficiency of MRI and MRA in the acute subarachnoid haemorrhages diagnostics differs—some authors insist on their accuracy, high sensitivity and specificity, while others see serious limitations. The problem is that the fresh blood mixed with CSF slightly changes the signal on T1- and T2-weighted imaging. Pulse-se-
quence FLAIR seems to be a more informative mode, capable of revealing the changes of relaxation properties of CSF in case of blood cells. However, MRI is much more effective than CT in the diagnosis of subarachnoid haemorrhages in subacute and chronic stages, when blood (even traces) due to methaemoglobin presence plays a role of natural contrast and ensures a high signal on T1-weighted imaging (Fig. 3.146). If the patient underwent several intraventricular or subarachnoid haemorrhages, then it is possible to observe the haemosiderin deposits in pia mater of the cerebrum and cerebellum, around the brainstem and even in vertebral canal. This finds its reflection on T2-weighted images as a dark border, which separates the brain surface from the CSF cisterns. In the literature, this late sign of the subarachnoid haemorrhage is called “superficial siderosis”.
Cerebrovascular Diseases and Malformations of the Brain
191
Fig. 3.146a–f MRI in subacute subarachnoid haemorrhage after rupture of sack aneurysms of the right (a–c) and the left (d–f) internal carotid arteries. Haemorrhages are better visualised on Т1-weighted imaging in both cases as a hyperintense signal of blood in subarachnoid spaces due to methaemoglobin
Subdural and epidural haemorrhages pass through the same stages as intracerebral haemorrhage. The mass effect is more frequently caused by extracerebral haemorrhages. This mass effect can lead to impaction. However, the most frequent origin of these haemorrhages is a traumatic one. Among the non-traumatic disorders, the bleeding can be caused by the ruptures of malformations, arteriovenous dural fistulas, sinus thrombosis and coagulopathy, among others. The acute subdural haemorrhage is visible on the CT as an area of increased density in crescent form, located between internal bone lamellae and brain tissue. The most frequent cause of such haemorrhage is rupture of superficial veins. In the acute phase, the MRI visualisation of subdural blood accumulation is not very precise, especially in cases when the thickness is not great. On FLAIR images, “acute” blood is visible as a local area of increased MR signal on a
background of low signal from CSF and subarachnoid spaces free of blood. On CT, the subacute haemorrhage is usually isodense in comparison with the neighbouring brain cortex; it requires the certain skills in its identification. The signs of dislocation of the neighbouring gyri or (in case of a large haemorrhage) the dislocation of the brain midline structures can be helpful. Contrast enhancement can additionally facilitate haemorrhage identification, by the detection of the dislocation of arterial or venous vessels on the convex brain surface. A haemorrhage capsule, forming by the end of the first week, can also be visualised after contrast enhancement. Without a doubt, MRI in T1 mode is the method of choice for the visualisation of the subdural blood accumulation in the subacute stage. The blood typically has a high MR signal in T1 mode, and its presence is clearly detected in the suba-
192
rachnoid space. In T2 mode, the blood is usually hyperintense, and the signal level is close to those of normal CSF in the lateral ventricles. On this sequence, the subdural haemorrhage is defined as an area of uneven dilatation of the subarachnoid space in comparison with the opposite side. The epidural haemorrhage has a form of a biconvex lens, and it is clearly visualised on T1weighted images; the signs of haemorrhage on T2 are identical to those from the blood accumulation. In the chronic stage, subdural and epidural haematomas are mainly encapsulated extracerebral mass lesions. On CT, they have decreased density, and their form depends on location. The capsule intensively accumulates contrast medium. The intersections can be detected in the haemorrhage cavity.
Chapter 3
If non-contrast CT shows novel areas of increased density, it points to a repeated haemorrhage. The characteristics of the extracerebral haemorrhages on the MRI are close to the MR signal from CSF in lateral ventricles. The higher MR signal from a haemorrhage than CSF in T1 mode is a sign of continuing presence of protein elements in a haemorrhage cavity or a sign of the repeated haemorrhage. In the late stage, haemorrhages cannot be differentiated by their MRI characteristics from CSF in the subarachnoid space. Rarely in 0.3–2.7% cases (according to different data), the calcification of haemorrhage walls can be observed. Such calcification can be better detected with the use of CT. Intraventricular haemorrhages occur in cases of rupture of subependymal veins, or when the intracerebral haemorrhage cuts through ependyma to the ventricle’s cavity (more fre-
Fig. 3.147a–c Intraventricular haemorrhage. CT images (a–c) show a hyperdense area in the lateral and the fourth ventricles. Haemorrhage in the right basal ganglia is also visualised
Fig. 3.148a–c Intraventricular haemorrhage. Т1-weighted imaging (a), Т2-weighted imaging (b) and MRA in 3D TOF (c): tamponade of the
left lateral ventricle lumen with a blood clot
Cerebrovascular Diseases and Malformations of the Brain
quently to the lateral ventricle), with the subsequent spreading along the ventricular system in the descending direction. The most frequent reasons for intraventricular haemorrhages of non-traumatic origin are hypertonic haemorrhages in basal ganglia structures, rupture of AVM or deep cavernoma. In the acute phase, CT better identifies the blood clots in ventricles, due to their typical density increase (Fig. 3.147). The MRI clot characteristics are close to those of intracerebral haemorrhages; however, because of direct contact with CSF, the periods of the stages mentioned above are substantially changed. On MRI, the blood has an increased signal in the subacute phase (Fig. 3.148), and in this stage, it already is poorly visualised on CT. The chronic stage of intraventricular haemorrhage is absent, and there is no siderin accumulation at the site of a
193
blood clot that underwent lysis. Ventricular hydrocephalus is observed on late CT and MRI scans, due to intraventricular haemorrhage.
3.11 Intratumoral Haemorrhages The aetiology of intratumoral bleeding is not clear. The influence of several factors that facilitate the haemorrhagic impregnation of the tumour tissue and the formation of haemorrhage are assumed; among them are high-malignancy tumours with the development of pathologically deformed vessels (neoangiogenesis), fast tumour growth accompanied by the necrosis and direct invasion of the vessel wall. According to the statistical data, haemorrhages in brain tu-
Fig. 3.149a–c Haemorrhage into the metastasis in the left thalamus. CТ before (a,b) and after (c) contrast enhancement. Round heterogeneously hyperdense mass is seen in the thalamus, with marked contrast enhancement of capsule of the metastasis
Fig. 3.150a–c Haemorrhage into the metastases of melanoma. Т1-weighted images (a,b) and Т2-weighted image (c) reveal large tumour nodules with hyperintense signal in the centre due to haemorrhage (methaemoglobin). Hypointense signal on periphery (Т2-weighted imaging) is explained probably by the presence of haemosiderin
194
Chapter 3
Fig. 3.151a–c Haemorrhage into the metastasis of the right parietal region. CT with contrast enhancement (a), MRI in Т1-weighted images
(b) and Т2-weighted imaging (c) reveal a large intratumoral haemorrhage with hyperintense signal of methaemoglobin
Fig. 3.152a–d Glioblastoma of the left temporo-occipital region. There is a mass of heterogeneous structure hypodense in the centre on CT (a) with contrast enhancement. T2-weighted (b) and Т1-weighted images (c): there is a large area of heterogeneous signal intensity changes typical for subacute haemorrhage. On MRI after contrast enhancement (d) an additional area of hyperdense signal appears on periphery of the haemorrhage (arrow)—the infiltrative part of the tumour
Cerebrovascular Diseases and Malformations of the Brain
195
Fig. 3.153a–c Haemorrhage in the cavernoma of the right parietal region. Т2-weighted imaging (a), Т2*-weighted imaging (b) and Т1-weighted imaging (c) reveal haemorrhages in different stages within the structure of cavernoma
Fig. 3.154 Haemorrhage in the pituitary adenoma. On coronal MRI Т1-weighted imaging there is a hyperintense signal in the right half of sella turcica (due to methaemoglobin) within the intratumoral haemorrhage. The pituitary infundibulum is displaced to the left
mours occur in 1–15% of all cases (Osborn 1999). Among the malignancies, they are the most common in cases of glioblastoma, anaplastic astrocytoma and metastasis (bronchiogenic carcinoma, melanoma, hypernephroma and thyroid gland carcinoma) (Figs. 3.149–3.152). The growth of the majority of highly vascularised tumours (haemangioblastoma, ependymoma and lymphoma) is quite often accompanied by the development of intratumoral bleeding. The formation of intratumoral haematomas is typical for cavernoma and hypophysis (Figs. 3.153, 3.154). The haemorrhages can occasionally be visualised in meningioma, neurinoma and in several other benign tumours and cysts. CT and MRI pictures of intratumoral haemorrhage develop in different times and morphological frames than in cases of intracerebral haemorrhage of different aetiology. In cases of intratumoral haemorrhage, the stage of dioxyhaemoglobin existence (low MR signal in T2 and T2* modes) can be prolonged, and the hypointense area (on MRI) and area of
increased density (on CT) can be visible after more than a week. The ring-shaped accumulation of haemosiderin on the tumour periphery is not typical for intratumoral haemorrhages. The haemosiderin accumulation may be found in the form of spots or may be completely absent, and it is more frequently observed in intramedullary than in the intracerebral tumours. More intense oedema and mass effect occurs more frequently than in cases of intracerebral haemorrhage. Other signs are a multifocal character of haemorrhage in tumour and uneven contour. The analysis of location in some cases can help to differentiate the intratumoral haemorrhage, as the affection of corpus callosum is not typical for hypertonic haemorrhage. Hyperintense (on T2 MRI) and hypodense (on CT) areas due to oedema surrounding the non-tumoral haemorrhage usually disappear after 4–8 weeks. Moreover, by this time, the mass effect should disappear, and in most cases, the tissue defect is detected. The increase of
196
Chapter 3
Table 3.4 Location and frequency of hypertonic hemorrhages Location
Prevalence %
Basal ganglia
60–70
Thalamus
10–20
Brainstem
5–10
Cerebellum
2–5
Cerebral hemispheres
1
an area of brain tissue changes around the haemorrhage can point to tumoral origin. Contrast enhancement can be useful in case of suspicion on primary tumour (revealing the contrast accumulation on the periphery of haemorrhagic component) and in cases of metastasis (revealing the multiple foci).
3.12 Hypertense Haemorrhages Arterial hypertension is the most frequent non-traumatic cause of intracranial haemorrhages in adults. This type of haemorrhage is more common in men aged 60–80 years. The most frequent location is basal ganglia (Table 3.4). It is commonly considered that hypertensive haemorrhage (HH) accounts for 10% of all cases of strokes; its mortality is highest and reaches 50%. Degenerative changes of vessel walls with the consequent formation of microaneurysms and hyalinosis are the main steps of HH pathogenesis. These changes more frequently develop in small perforating arteries (with calibres of 50– 200 μm) of basal ganglia, brainstem and cerebellum. The sub-
sequent rupture of the walls of affected vessels leads to the formation of haemorrhage. This may explain the deep location of such haemorrhages in most cases. In approximately half of cases, HH in the area of deep subcortical structures is accompanied by a breakout into ventricular system, that, as a rule, is combined with poor disease prognosis. Almost all patients with blood in the deep subcortical structures have prolonged hypertension in their histories. However, to rule out the latter reason for haemorrhage, it is necessary to conduct examinations of brain vessels more detailed with the use of MR or CT angiography. The use of direct angiography is an exception. CT performed in the acute stage clearly depict a hyperdense area in the depth of brain, which is typical for acute bleeding. The mass effect on the neighbouring structures and ventricular system is visualised in cases of large haemorrhage. The use of MRI T2 and T2* modes is preferable because haemorrhage is hypointense to brain tissue. On T1-weighted imaging, the signal from blood is close to that from brain tissue. In the subacute phase, the blood becomes less dense on CT, and it is poorly separated from sur-
Fig. 3.155a–c Intracerebral haemorrhage in the right temporal lobe. Т2-weighted imaging (a), Т1-weighted image (b) and MRA (c) on day
25 after onset reveal an area of signal change containing methaemoglobin and haemosiderin on periphery. MRA did not detect signs of aneurysm
Cerebrovascular Diseases and Malformations of the Brain
rounding brain structures. The perifocal oedema that appears in the first hours after the haemorrhage peaks in the first 2–3 days and gradually diminishes in volume by the end of the subacute phase. After contrast enhancement, an area of peripheral contrast accumulation typically occurs, and this situation requires the conducting of differential diagnosis of tumours. The MRI signs of the subacute intracerebral haemorrhage are more typical, and there is no great difference between them and other intracerebral haemorrhages. Nevertheless, in these cases, thorough analysis of all data collected during the examinations is required to avoid diagnostic mistakes (Fig. 3.155). In the residual period, the brain tissue defect forms on the site of a haemorrhage. This defect of brain tissue is filled with CSF, and it can be of various forms and sizes, depending on the initial volume of the extravasated blood. Visualisation of the “crown” of low MR signal on the periphery of the mentioned defect, which corresponds with the sites of haemosiderin accumulation, is a typical sign of haemorrhage, and it persists for relatively a long time.
3.13 Hypertense Encephalopathy Hypertensive encephalopathy (HE) is a separate syndrome, with attributes of the systemic arterial hypertension and focal neurological signs (it is necessary to distinguish it from CIBD). The syndrome is clinically characterised by fast progression of neurological signs such as headache, epileptic seizures, vision impairment, change of mentality and focal neurological signs. One of the most frequent causes for HE is a toxaemia due to pregnancy; less frequent causes are other diseases like chronic renal insufficiency, thrombocytopaenic purpura, haemolytic uraemic syndrome and systemic lupus erythematosus (rare). HE aetiology in eclampsia and other types of diseases is relatively similar—the exhaustion of mechanisms of vascular tone autoregulation and severe increase of blood pressure; the arterioles are passively overstretched with the subsequent damage of the blood–brain barrier. The developing transudation of the protein-rich interstitial liquid causes the formation of multiple focuses of vasogenic oedema. The brain areas supplied by the posterior circulation area are the most affected by HE. It is widely believed that the possible reason can be lesser sympathetic innervation of walls of these arteries in comparison with the walls of carotid arteries.
197
in deep white matters and subcortical structures of the brain hemispheres, and multiple non-haemorrhagic foci, are most frequently visualised in occipital lobes. On CT, multiple hypo- and hyperdense lesions (haemorrhages) are observed in the basal ganglia. MRI visualises the multiple areas of increased MR signal in T2 and FLAIR images in the white matter of women with preeclampsia. Larger hyperintense foci (oedema) in white matter prevailing in the parieto-occipital lobes on MRI are found. The foci may also be observed in deep subcortical structures. In contrast to autopsy data, MRI signs of haemorrhagic component are not frequently observed in these areas. Chronic kidney diseases, vasorenal hypertension, and other systemic diseases such as thrombocytopenic purpura, haemolytic uraemic syndrome and systemic lupus erythematosus can have the symptoms of CNS affection with the presence of haemorrhagic and non-haemorrhagic foci in basal ganglia.
3.14 Rare Causes of Intracerebral Haemorrhage Amyloid angiopathy, infection, overdosing of some medicines (sympathomimetics), coagulopathy and the use of anticoagulant therapy are infrequent causes of intracerebral haemorrhage.
3.14.1 Amyloid Angiopathy The diagnosis of cerebral amyloid angiopathy is established based on histological examination. However, the presumed diagnosis can be made based several signs like old age with the absence of hypertension, and the presence of intracerebral (more frequently subcortical) haemorrhages. The deposition of the special fibrillar protein—called amyloid—in the walls of small, usually cortical leptomeningeal
3.13.1 Toxaemia Due to Pregnancy Preeclampsia and eclampsia are severe complications that can develop in the last trimester of pregnancy. They are accompanied by the abrupt rise of blood pressure, and they quite often lead to a lethal outcome. The symptoms of CNS affection are typical for these syndromes. According to published reports, the foci of petechiae, and bigger cortical and subcortical haemorrhages, haemorrhages
Fig. 3.156 Amyloid angiopathy. Intracerebral haemorrhage of corti-
cal and subcortical location in the right parietal region in a 65-yearold patient without arterial hypertension on (CТ)
198
Chapter 3
Fig. 3.157a–c Amyloid angiopathy. CT images reveal multiple haemorrhages of cortical and subcortical location in cerebral hemispheres
Fig. 3.158a–c Amyloid angiopathy. Т1-weighted imaging (a), Т2-weighted imaging (b) and Т1-weighted imaging in sagittal projections (c)
demonstrate subacute–chronic microhaemorrhage in the right parietal region in a 78-year-old patient without arterial hypertension
arteries, with the formation of insoluble crystallised complex, is one of the main attributes of this disease. Unlike the haemorrhages due to arterial hypertension, the presence of multiple but small haemorrhages in subcortical areas of the brain is typical for amyloid angiopathy. However, the deep subcortical structures remain largely intact. Therefore, the detection on CT and MRI of the multiple small haemorrhages of different stages in an elderly patient without signs of hypertension is a pathognomonic attribute of this disease. Nevertheless, single and relatively large haemorrhages also can be observed (Figs. 3.156–3.158).
3.14.2 Inflammatory Diseases The incidence of haemorrhage in the course of inflammatory disease is not an common phenomenon. There is some information in the literature about intracerebral haemorrhages around brain abscesses. Infectious endocarditis occurring when the infected blood clot meets the brain vessels, fungal vasculitis and necrotising haemorrhagic encephalitis, moyamoya disease, Rendu-Osler-Weber disease, etc., can be causes. Intracerebral haemorrhage can be a complication of some medications, such as amphetamine and its derivatives, ephed-
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.159 Schematic representation of location and incidence of sack aneurysms of the large arterial circle of skull base (based on the Burdenko Neurosurgical Institute’s statistics)
rine, cocaine and anticoagulants (in case of anticoagulant therapy).
3.15 Intracranial Arterial Aneurysms 3.15.1 Anatomy of the Cerebral Arterial Aneurysm Arterial aneurysms (AA) are local out-pouching of a blood vessel wall. The most frequent sites for the aneurysms are the sites of bifurcation, anastomosis of the basal arteries of the circle of Willis, and in rare cases, the aneurysm can form directly from the sidewall of the non-branching artery. The aneurysmal sack may have a narrow neck or wide base (or detach from an artery on a wide stalk).
3.15.2 Location and Frequency According to the statistics, 90% of all AA are located in the anterior segments of the circle of Willis and only 10% in the posterior segments (Dandy 1944; Zlotnik 1967). Twenty to 30% of all aneurysms are observed in the area of anterior cerebral–
199
anterior communicating arteries, 10–20% at the site where the posterior communicating artery descends from the internal carotid artery, 5–10% at the site of the internal carotid artery bifurcation, and 15–30% at the site of bi- or trifurcation of the middle cerebral artery. Three to 15% of all aneurysms are located in the intra cranial segment (siphon) of the internal carotid artery up to the site of bifurcation, at the site of bifurcation of the basilar artery in no more than 3–8% of all aneurysms, while about 2–5% of the share of aneurysms to vessels of posterior cranial fossa—the most frequent spot there is the posterior inferior cerebellar artery (Fig. 3.159). Single aneurysms as a finding are reported in 1% of all autopsies and in 7% of all patients that underwent digital angiography not related to the subarachnoid haemorrhage (Nakagawa 1994; Osborn 1994; Schumacher 2000, 2002). The incidence of multiple aneurysms varies from 14 to 45% of all observations. Thus, it is necessary to note that the revealing of multiple-vessel lesions depends on several factors, in particular, on the quality of the angiography equipment, the number of examined vessel territories and the qualification and experience of the radiologist. Multiple aneurysms are observed in a fifth to a third of all cases at intracranial locations of aneurysm (Orrison 2000). About 75% of patients have two aneurysms, 15% have three and in 10%, more than three aneurysms. In cases with multiple aneurysms, an association with gender (more frequently in women) has been observed. Multiple aneurysms are often observed in patients with diseases such as vasculopathy, fibromuscular dysplasia and polycystic renal disease. Among numerous AA classifications, the most comprehensive is the anatomosurgical one (Yasargil 1984) accepted by the Burdenko Neurosurgical Institute. 1. Aneurysms of the internal carotid artery a. Intracavernous b. Medial wall aneurysms–ophthalmic, distal c. Aneurysms of top wall d. Aneurysms of bottom wall e. Aneurysms of lateral wall—in the ostium of the posterior communicating artery, in the ostium of anterior choroid artery f. Bifurcation area 2. Aneurysms of the middle cerebral artery a. Proximal (M1) b. Bifurcation area c. Distal 3. Aneurysms of the anterior cerebral artery a. Proximal (A1) b. Area of the anterior communicating artery c. Pericallosal 4. Aneurysms of vertebral artery a. In the ostium of the posterior inferior cerebellar artery b. In the distal segment of the posterior inferior cerebellar artery c. In the trunk of the vertebral artery d. Fusiform dilatation of the vertebral artery
200
Chapter 3
5. Aneurysms of the basilar artery a. Bifurcation area b. Area of the superior cerebellar artery and the posterior cerebral artery c. Area of middle segments of the basilar artery trunk d. Fusiform dilatation of the middle segments of the basilar artery trunk e. The posterior cerebral artery: the peduncular area (P1), area of the circumferential cistern (P1–P2), P2 segment, distal (P3), the superior cerebellar artery (distal segments) According to their size, aneurysms are divided into small (2–6 mm), intermediate (6–15 mm), large (15–25 mm) and huge (more than 25 mm).
3.15.3 Age As a rule, aneurysms are a condition of adults. The peak occurrence of the beginning of clinical signs begins between the ages of 40 and 60 years. Intracranial AA are a rare phenomenon in children, and they constitutes less than 2% of all cases. There are some distinctive attributes distinguishing aneurysms in adults from those in children. In children, the incidence of aneurysms in boys is higher than that in girls. The ratio is about 3:1. About 20% of all aneurysms in children are diagnosed in the posterior segment of the circle of Willis or in the more distal vessels. The most frequent site in children in comparison with the adults is the bifurcation of the internal carotid artery. Its share constitutes (according to different data) from a quarter to half of all aneurysms in children. The so-called huge aneurysm (more than 2.5 cm) is often a phenomenon in children, while the incidence of multiple aneurysms is lower.
Fig. 3.160 Schematic representation of structure of arterial aneurysms originating from arterial bifurcations. 1 internal layer (intima), 2 internal elastic membrane, 3 muscle layer, 4 adventitia, 5 a vessel lumen, 6 the cavity of aneurysm (lines)
3.15.4 Clinical Manifestations
The majority of AA are true aneurysms, i.e. their wall contains (with some deficit) several layers also present in a normal arterial wall. Typically, an aneurysm is a round out-pouching of an artery wall, which protrudes through local defect in internal elastic membrane and media. Normal muscular and elastic membranes usually cover only the aneurysmal neck, and in the aneurysmal sack region, the wall usually contains only intima and adventitia (Fig. 3.160). The acute and organised blood clots are often found in the lumen of aneurysm.
As a rule, the first signs in the clinical picture of the disease are symptoms of subarachnoid haemorrhage. According to several authors, about 80–90% of non-traumatic subarachnoid haemorrhages are related to intracranial aneurysm rupture. However, in cases of large AA, the clinical course becomes “pseudotumoral”, and the symptoms resemble those typical for tumours. Therefore, aneurysms of the internal carotid– posterior communicating arteries can evidence themselves by the paresis of the oculomotor (third cranial) nerve, while for aneurysms located in the cavernous sinus the involvement of cranial nerves III–VI is typical. Sometimes headaches and seizures are observed. They may be accompanied by ischaemic attacks and strokes. The causes of disability and death after the rupture of a saccular aneurysm are brain haemorrhages and ischaemic damage due to arterial spasm. Primary haemorrhage from the ruptured aneurysm is fatal for a third of all patients, and
20–50% of those survivors have recurrent haemorrhage. The highest risk of recurrence is within the first 2 weeks. There is no statistically significant correlation between the size of aneurysm and the risk of its rupture. However, it is believed that with the increase of an aneurysm’s size, the risk of the attenuated wall rupture becomes higher.
3.15.5 Pathology
3.15.6 Aetiology The pathogenesis of the AA is still unclear. Nevertheless, the main factors in AA formation are acquired factors, namely haemodynamic stress (it plays one of the major roles), degenerative changes of the vessel wall and molecular genetic factors.
Cerebrovascular Diseases and Malformations of the Brain
201
Fig. 3.161a–c Variants of location of aneurysms within bifurcations of cerebral arteries. a Bifurcation of the internal carotid artery, b bifurcation of the ACA, c bifurcation of the middle cerebral artery
Fig. 3.162a–c Variants of aneurysms caused by changes in blood flow (hydrodynamic aneurysms), arrows
3.15.6.1 Degenerative AA
3.15.6.2 Aneurysms Related to the Changes of Blood Flow
Degenerative AA (according to the classification of Medvedev 1993) are considered a result of vascular injury of a bifurcation, due to haemodynamic factors. The reason for their formation is the vascular injury caused by haemodynamic changes (the most common cause). The artery wall at the bifurcation endures the biggest haemodynamic stress, which explains the fact that the majority of AA are located at the site of divisions of intracranial arteries. The initial intima damage probably serves as a starting point in the initiation of the aneurysmal protrusion (Fig. 3.161).
The second most frequent reason for AA formation is related to the acceleration of blood flow. The basic attribute of these aneurysms is a combination with AVM of brain vessels. Such malformations change blood flow, which facilitates the AA formation. It is believed that the combination of AA with malformation can reach 30% (on average, 8–12%). AA is typically located on the proximal and distal segments of the vessels that supplied the malformation. Haemodynamic changes are the reason for formation of the proximal aneurysms. As a rule, the distal aneurysms are located inside the malformation node. These aneurysms are protrusions that do not have the elastic and muscular layers typical for arteries (Fig. 3.162).
202
Chapter 3
Fig. 3.163a–e Traumatic aneurysms of cerebral vessels (arrows). Different patients
Fig. 3.164a–c Traumatic arteriovenous fistula of the right common carotid artery. 2D TOF MRA shows a fistula between the right common
carotid artery and the right jugular vein (arrow)
Cerebrovascular Diseases and Malformations of the Brain
203
Fig. 3.165a–e Variant of arterial aneurysms of
extracranial segments of the internal carotid artery. Case 1. Cerebral АG (a) of the carotid artery shows a sack of aneurysm heterogeneously filled with contrast medium (arrow). Case 2. MRI using Т2-weighted imaging (b,c) shows a giant aneurysmal sack of the internal carotid artery below the skull base to the left. Case 3. MRA with bolus contrast enhancement (d,e) reveals a small sack aneurysm of the С3 segment of the internal carotid artery (arrow)
204
Chapter 3
3.15.6.3 Traumatic Aneurysms These aneurysms constitute less than 1% of all AA; however, in children, this percentage is noticeably higher (5–15%). These aneurysms fall into two categories: (1) as a result of penetrating injury; and (2) as a result of non-penetrating injury. The most likely cause for the aneurysms of the penetrating injury is gunshot wounds to the skull. According to the statistical data, up to 50% of all patients with this type of injury have saccular aneurysms. However, early diagnosis is complicated by the presence of the huge foci of brain tissue damage and haemorrhage. The penetrating injury of extracranial vessels can be the cause of arterial and arteriovenous fistula, dissection and traumatic pseudo-aneurysms (Figs. 3.163–3.165). Carotid arteries are the most frequent area of lesions. Pseudo-aneurysms or false aneurysms are cavities inside of
the blood clot that surrounds the artery. Such a cavity is connected with the arterial lumen, and it does not have any layers typical for the arterial wall. Aneurysms that are consequences of non-penetrating injury are usually located at the skull base, and they are mainly caused by the fracture of bones of skull base adjacent to vessels. In addition, the aneurysms of the carotid artery can be observed in cases of heavy flexion–extension and rotation trauma, when the extracranial segments have undergone overdistension, which causes the ruptures at the site of the artery’s entry into the skull. Closed craniocerebral injury can cause the formation of aneurysms on the peripheral (distal, towards the arterial circle of cerebrum) arteries. There were reports about aneurysm formation on the pericallosal artery after the injury caused by the low edge of the falx cerebri.
Fig. 3.166a–d Mycotic arterial aneurysms. Multiple aneurysms (a,b) of the middle cerebral artery (arrows). Aneurysm (c,d) of the left superior cerebellar artery (arrow)
Cerebrovascular Diseases and Malformations of the Brain
205
Fig. 3.167a–f Fusiform aneurysm of basilar artery. CT before (a) and after (b) contrast enhancement, and a CTA in 2D (c,d) and 3D (e,f)
reconstruction demonstrate thickening and coiling of the basilar artery with multiple calcifications in its wall
3.15.6.4 Mycotic Aneurysms
3.15.6.5 Oncotic Aneurysms
Mycotic aneurysms are those that are formed because of the direct affect on the vascular wall by an infectious process, for instance, septicaemia and infection penetration from infected thrombi. Such process starts from internal vessel surface and goes towards the external surface. Infectious process penetrates the vasa vasorum system and gradually affects all layers including adventitia, which at the end leads to the weakening of the wall and subsequent aneurysm formation. It is thought that with the invention of antibiotics, aneurysms of this type became a rare phenomenon, and currently, their share is about only 2–4% of all AA (in children up to 15%). The most frequent location is a thoracic aorta; the involvement of intracranial vessels is observed much more rarely (Fig. 3.166).
This is one of the rarest types of aneurysms (less than 0.1% of all AA). They are caused by the tumoral invasion of the arterial wall, with the consequent protrusion of the affected wall. As a rule, the tumours that can facilitate the aneurysms’ formation are malignant (both primary and metastasis). There are reports about the findings of aneurysms in patients with the malignant glioma, pituitary adenoma and choroid carcinoma.
3.15.6.6 Aneurysms in Vasculitis, Vasculopathy and the Drug Overdose The arterial aneurysms of cervical and cerebral vessels are frequently combined with the following diseases: fibromuscular dysplasia, systemic lupus erythematosus and several forms of arteritis (Takayasu disease). The various forms of protrusions,
206
Chapter 3
Fig. 3.168a–f Fusiform aneurysm of ACA. CT images before (a) and after (b) contrast enhancement reveal the dilation of lumen of the ACA
with wall calcifications. CTA with 3D reconstruction (b–d) demonstrates irregular dilation and coiling of the А2 segment of the ACA. Direct cerebral AG confirms the acquired data (f)
including the aneurysmal ones, can be found in cases of overdosing of the several medicines (cocaine, heroin, ephedrine, methamphetamines).
MR signs of FA depend on the volume of thrombotic masses and their level of retraction and on the size of the functioning part of artery (Fig. 3.168).
3.15.6.7 Fusiform Aneurysms
3.15.6.8 Hereditary Diseases
The term fusiform aneurysm (FA) is synonymous with atherosclerotic aneurysm, since the main cause for their development is a severe atherosclerosis. Quite often, such aneurysms look like strange dilatation of the vessel lumen. The parietal formation of thrombi is possible in this type of aneurysm. The arteries of the posterior circulation area are affected more often. Usually FA originate from a lengthened, dilated and coiled artery, which is clearly visualised on CT. The areas of increased CT density in the aneurysm’s wall are formed by the thrombotic masses and calcifications. The intense density increase from the functioning part of vessel’s lumen and aneurysm’s cavity is observed after contrast enhancement (Fig. 3.167).
There are myriad hereditary diseases of connective tissue, which are frequently accompanied by AA. About 5% of patients with AA have some manifestations of connective tissue disease. The most important among these diseases are the following: Ehlers-Danlos (subtype IV), Marfan syndrome, NF I and autosomal-dominant polycystic renal disease.
3.15.6.8.1 Ehlers-Danlos Syndrome Ehlers-Danlos syndrome is actually a heterogeneous group of hereditary diseases of a connective tissue that is divided
Cerebrovascular Diseases and Malformations of the Brain
into subtypes, depending on clinical and genetic factors. The majority of them are characterised by the presence of the increased mobility, skin hyperelasticity and damage with the formation of the pathological scars. It is reported that EhlersDanlos (subtype IV) is one of the most frequent types of the specified disease, and it has high mortality. The reason for this is collagen deficiency (type III). Collagen is a main component of elasticity for structures such as arteries and veins, and also walls of intestines and visceral organs. Therefore, the rupture of arteries, wall of intestines and urinary bladder, along with the formation of AA and spontaneous carotid–cavernous fistulas, are the main complications of this disease. AA are typically located on large arteries.
3.15.6.8.2 Marfan Syndrome Marfan syndrome is characterised by pathological deformities and changes of skeleton and cardiovascular system, defects in eye tunics and spinal meninges. It is inherited as an autosomal-dominant type; however, features of the disease can be absent in 30% of relatives. One of the signs of this disease is AA formation in intracranial as well as in extracranial vessels; in the former, saccular aneurysms are observed more frequently, and in the latter, fusiform aneurysms are present.
3.15.6.8.3 NF I NF I is characterised by a mutation of the gene encoding neurofibromin, which plays the regulatory role in the development of a vascular connective tissue. A lesion of the vascular wall is not often an attribute in patients with neurofibromatosis; however, it can lead to formation of the stenosis of main cerebral arteries, rupture of the artery wall, AA and fistula formation. As a rule, arterial aneurysms in these patients are saccular, fusiform or dissecting.
207
3.15.6.8.4 Autosomal-Dominant Renal Polycystosis Autosomal-dominant renal polycystosis belongs to the group of monogenic diseases, the most frequent genetic diseases. Polycystine is a membrane protein that is coded by the PKD1 gene. Presumably, it plays a role in maintenance of the structural integrity of a connective tissue. Patients with this disease have a predisposition to polycystosis of kidneys and other visceral organs, as well as to different vascular lesions such as dissection of aorta and vessels, more often extracranial, and AA formation. On autopsy, intracranial AA were found in approximately a quarter of all patients with this disease, and in 20% of cases, rupture of AA was the reason of death. The so-called familial intracranial aneurysms are a separate group. They are diagnosed at least in first-degree relatives, and they are not related to any other known hereditary form of connective tissue diseases. Microscopic examination of vessel walls in patients with this form of disease reveals signs of antipathy, with damage to both extra- and intracranial vessels. It is thought that the first-degree relatives of patients with a presumably familial form of AA belong to a high-risk group, and they should have a follow-up examination of cerebral vessels (CT, MRI or cerebral angiography). Additional pathological conditions with a high risk of AA formation have been described in the literature; among them are congenital heart diseases, anomaly of vessels development (duplication of arteries), sickle-cell anaemia and some others. Some researches even found a link between AA formation and environmental factors, for instance, smoking.
3.15.7 Complications Due to AA Rupture 3.15.7.1 Intracranial Haemorrhage from AA CT is one of the most adequate methods in diagnostic of a haemorrhage caused by an AA rupture regardless of its loca-
Fig. 3.169a,b Variants of location of intracranial haemorrhages due to rupture of arterial aneurysms. CT after rupture of the ACA and the anterior communicating artery aneurysm (a), CT after rupture of the middle cerebral artery aneurysm (b)
208
Chapter 3
Fig. 3.170a–f Intraventricular haemorrhages after rupture of arterial aneurysms. a–c Case 1. d–f Case 2
Fig. 3.171a–c Day 2 after subarachnoid haemorrhage. Т2-weighted imaging (a), Т1-weighted imaging (b) and FLAIR (c) depict blood in basal cisterns, around brainstem and suprasellar region: haemorrhage has a hyperintense signal in FLAIR (arrow), not seen on Т1-weighted imaging
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.172a–i Variants of subacute haemorrhage after rupture of arterial aneurysms. Case 1. Т2-weighted imaging (a) and Т1-weighted imaging (b) show a subacute haemorrhage in the right mediofrontal region after rupture of aneurysm (arrow). c 3D TOF MRA does not depict the aneurysm due to phenomenon of pseudo-enhancement of haemorrhage. Case 2. The anterior cerebral–anterior communicating artery aneurysm (d–f), in contrast to standard sequences. Т2-
209
weighted imaging (d), Т1-weighted imaging (e) and 3D TOF MRA (f) almost fail to depict the aneurysm. Case 3. Intracerebral haemorrhage in the right temporal lobe due to rupture of arterial aneurysm of the middle cerebral artery. Т2-weighted imaging (g) and Т1weighted imaging (h): small aneurysm with subacute haemorrhage; the methaemoglobin signal makes depiction of the aneurysm in 3D TOF regimen difficult (i)
210
Fig. 3.173a–i Case 1. a–c Rupture of the right MCA aneurysm and
accumulation of blood in the Sylvian fissure. Large hypodense area within the internal carotid artery area, dislocation of the ventricular system and signs of tentorial impaction are seen along with the absence of the circumferential cistern. Case 2. d–f Intracerebral haemorrhage after rupture of aneurysm of the right internal carotid
Chapter 3
artery bifurcation. The area of perifocal oedema and focal ischaemia behind the haemorrhage are seen. Dislocation of the ventricular system, small amount of blood in the posterior horn of the lateral ventricle. Case 3. g–i Large ischaemia of the left hemisphere due to angiospasm of the middle and posterior cerebral arteries after rupture of aneurysm of the middle cerebral artery
Cerebrovascular Diseases and Malformations of the Brain
211
tion: subarachnoid, intracerebral or subdural. The accuracy of CT diagnosis of acute subarachnoid haemorrhage is close to 100%; however, it gradually decreases to 10% after 9–10 days due to relatively fast resorption of blood from the CSF (Figs. 3.169, 3.170). Intracerebral haemorrhages can, however, be easily revealed even after several weeks since the subarachnoid haemorrhage, as areas of decreased density. It should be noted that in superacute and acute phases, the use of MRI is limited by the low sensitivity of this method to blood identification in the subarachnoid space around this time. The FLAIR mode is more informative among standard pulse sequences in blood detection, due to suppression of MR signal from CSF in the tissues surrounding brain (Fig. 3.171). While CT sensitivity to detect blood in the subarachnoid space fails in the course of time, for MRI the process is more successful. With the appearance of methaemoglobin in the
subacute phase of subarachnoid haemorrhage, the location of blood and its distribution in the subarachnoid spaces of brain and spinal cord can be easily defined with the use of MRI (Fig. 3.172). Moreover, only MRI can detect the presence of haemosiderin accumulation in the periphery of an “old” haemorrhage. Superficial haemosiderosis due to recurrent subarachnoid haemorrhages may be visualised only on MRI as an area of markedly hypointense MR signal, especially on T2 and T2* sequences.
Fig. 3.174a–f Segmental angiospasm of cerebral vessels. Aneurysm
proximal segment (e) and aneurysm of the anterior cerebral anterior communicating artery–segmental spasm of the ACA proximal and distal to aneurysm (f)
of the basilar artery bifurcation (a,b), aneurysm of the middle cerebral artery bifurcation with spasm of its distal segment (c,d), aneurysm of the middle cerebral artery bifurcation with spasm of its
3.15.7.2 Vasospasm and Ischaemia The reactive narrowing of brain arteries after subarachnoid or intracerebral haemorrhage is a severe complication, and it is one of most important factors responsible for worsening
212
Fig. 3.175a–f Aneurysm of the middle cerebral artery. Cerebral AG
on the 12th day (a) reveals spasm of the middle cerebral artery at its total length, and the aneurysm is not seen in this moment. CTA in MIP reconstruction (b,c) reveals narrowing of the left middle cerebral artery lumen, and small aneurysm (arrow). MRA (MIP recon-
of the patient’s condition; sometimes it may even lead to a fatal outcome. In the majority of cases, the vessel spasm starts to develop after some delay (usually several days after, most frequently at 3–4 days) and does not immediately lead to a haemorrhage. Vasospasm can persist for several weeks. Thus, it is necessary to note that the degree of such a narrowing in many aspects depends on location of haemorrhage and the amount of extravasated blood. The diffuse spasm has the poorest prognosis, and it often leads to ischaemia and oedema (Fig. 3.173). Although there are several therapeutic regimens for vasospasm prevention at present, and these regimens are widely used, patients with huge subarachnoid haemorrhages should
Chapter 3
struction) in the same interval (d) clearly shows arterial angiospasm and the aneurysm. On MRA (MIP reconstruction) 20 days later, after intensive therapy, there is a restoration of the middle cerebral artery lumen with adequate imaging of the aneurysm (e,f)
undergo clinical and imaging examinations day after day as well as transcranial Doppler, the sensitivity of which in detection of the site and expansion of the cerebral vessels spasm reaches 80–90% according to most authors. Direct angiography is employed only in sensitive situations (Figs. 3.174, 3.175). In our opinion, CT angiography has the advantage over MRA in vasospasm diagnosis, due to its more accurate estimation of the narrowing of vessels in this period (Fig. 3.176). Recently, methods of direct and indirect estimation of local blood flow have gained popularity. They assess blood flow in any particular brain area. New methods like CT and MR perfusion, which combine the quickness of examination with less invasiveness, have started to compete successfully with such
Cerebrovascular Diseases and Malformations of the Brain
213
Fig. 3.176a–c Angiospasm of the left MCA and arterial aneurysm of the internal carotid artery siphon with haemorrhage. Axial CT image
shows a small haemorrhage in the medial region of the right temporal lobe (a). CTA (b,c) clearly shows the aneurysm as well as angiospasm of the middle cerebral artery (MIP reconstruction)
well-known techniques as CT with xenon, SPECT and PET (Binaghi et al. 2007; Yamada et al. 2007). In comparison with standard CT and MRI, CT and MR perfusion are much more sensitive to changes of local blood flow or volume (CBV and CBF), which allows their use in early diagnostics of vasospasm after subarachnoid haemorrhage (Figs. 3.177, 3.178).
3.15.7.3 Hydrocephalus Hydrocephalus is a relatively frequent sign after subarachnoid haemorrhage, and it is often responsible for the deterioration of a patient’s clinical condition. In the acute and the subacute stages, the most prevalent form is obstructive hydrocephalus, whereas in the chronic stage, the open form is observed more frequently (Figs. 3.179, 3.180). The incidence of hydrocephalus reaches 10–35% according to most authors. Therefore, the use of follow-up CT and MRI examinations images initial signs of ventricular system dilatation and resolves questions about shunting surgical interventions. Hydrocephalus also may occur in patients with non-ruptured arterial aneurysms. As a rule, these aneurysms are giant ones, and they cause intense dislocation with compression of the ventricular system (Fig. 3.181). The signs of AA on X-ray craniograms can be detected only when they have a huge size and their walls are partially calcinated, or when the aneurysms cause destruction of the adjacent bone (in cases of AA location on the skull base). Cerebral angiography is still the gold standard and is a reliable tool in AA diagnosis in acute and “cold” stages. However, with the introduction into clinical practice of methods such as spiral and multispiral CT angiography and MRA, indica-
tions for cerebral angiography have been revised. Recently, some reports have analysed interventions to “switch off ” the AA, based on CT an MRA. Our experience confirms such a possibility. Nevertheless, digital angiography still occupies one of the prominent places in the process of AA diagnosis (Fig. 3.182). Experience has proved that the use of standard examination sequences in cases in which CT and MRI scans lack special angiography software may reduce the risk of cerebral angiography, by verifying the haemorrhage and revealing the intracerebral bleeding in the particular site of the subarachnoid space and thus limiting the scope of angiography to the ipsilateral carotid or vertebral area. Cerebral angiography aims to achieve the following in AA diagnosis: First of all, it aims to achieve the following: to find the AA; to give the complete assessment of the intracranial circulation; to describe the AA anatomy, including the identification of the aneurysmal neck; to identify the perforating arteries that can be near the bottom of an aneurysmal; assess the collateral circulation; and to evaluate the accompanying pathology including vasospasm, mass effect, etc. After AA detection, one should perform the angiograms in such projections that allow clear imaging of the aneurysmal neck, body and bottom (Fig. 3.183). In addition, the cerebral angiography reveals the multiple characteristics of the affection, the vasospasm, its intensity and spread, and identifies the blood flow in anterior and posterior communicating arteries (collateral circulation, functioning of the arterial circle of cerebrum). These data are necessary for the neurosurgeon when he/she plans an intervention (Figs. 3.184, 3.185). Currently, the latter information cannot be obtained by any of the known diagnostic methods including CT and MRI angiography. Blood flow in the AA cavity is relatively com-
214
Fig. 3.177a–f Arterial aneurysm of the anterior cerebral and anterior
communicating arteries, intracerebral and intraventricular haemorrhages. CTA: at the level of clinoid processes there is a sack of aneurysm (a), and CTA in 3D reconstruction (b) ascertains the shape and location of the aneurysm (arrow). On CT perfusion image (c),
Chapter 3
circles outline those areas where estimation of cerebral blood flow was performed–perfusion maps (d CBV, e CBF). Digital imaging of cerebral blood flow parameters in time points corresponding to the figure (c). MRA was not efficient in showing the arterial aneurysm with the background of the haemorrhage (f)
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.178a–h Arterial aneurysm of the right middle cerebral artery 2 weeks after haemorrhage. CT image without contrast enhancement (a) on the level of lateral ventricles shows the changes of brain tissue density. There is mild ventriculomegaly. CT perfusion with reconstruction of CBV (b), CBF (c) and МТТ (d) maps shows a large area of impaired blood flow in the left frontal-temporo-occipital regions
215
(arrows). CT perfusion 1 week after reveals the zone of hypoperfusion in the right fronto-occipital region on CBV (f), CBF (g) and MTT (h) maps. There is restoration of temporal parameters of blood supply in the left hemisphere. CT image (e) demonstrates the small ischaemic infarction in the right medial temporal lobe laterally to the head of nucleus caudatus
216
Chapter 3
Fig. 3.179a–e Acute hydrocephalus after
the acute subarachnoid and intraventricular haemorrhage due to rupture of the internal carotid artery aneurysm (a,b). Observation in the “cold” period after subarachnoid haemorrhage from the arterial aneurysm of the anterior cerebral and anterior communicating arteries (c–e). A series of CT scans demonstrate the sack of aneurysm and severe hydrocephalic dilation of the lateral ventricles. Post-haemorrhagic changes in the left frontal lobe
Fig. 3.180a–c Open hydrocephalus after subarachnoid haemorrhage from the arterial aneurysm of the left vertebral artery. Direct cerebral AG (a): aneurysm is shown by an arrow. b,c MRI demonstrates severe ventriculomegaly with periventricular oedema around the lateral ventricles
Cerebrovascular Diseases and Malformations of the Brain
217
Fig. 3.181a–d Giant arterial aneurysm with partial thrombosis of the left vertebral artery in a 12-year-old child. CT images show a mass of heterogeneous density in posterior fossa. The functioning part of the aneurysm is hyperdense, thrombotic masses are isodense, and the third and the lateral ventricles are markedly dilated with periventricular oedema
218
Chapter 3
Cerebrovascular Diseases and Malformations of the Brain
219
9 Fig. 3.182a–i Variants of location of arterial aneurysms of cerebral vessels by DSA: of infraclinoid segment (a), of supraclinoid segment (b,c), of bifurcation of the internal carotid artery (d), of the anterior
cerebral and anterior communicating artery (e,f), of the middle cerebral artery bifurcation (g,h), of the ACA (i), of basilar artery (j,k) and of basilar artery bifurcation (l)
Fig. 3.183a–f Arterial aneurysm of supraclinoid segment of the in-
servation of the anterior cerebral–anterior communicating artery aneurysm (d–f) in oblique projection (f) improves detection of relationship between aneurysm and cerebral vessels
ternal carotid artery. Case 1. Digital AG in lateral (a), coronal planes of left carotid artery with compression of the right internal carotid artery (b) on the neck level and oblique (c) projections. Case 2. Ob-
220
Chapter 3
Fig. 3.184a–c Aneurysm of the right internal carotid artery bifurcation. The examination estimated the blood reflow with compression of the contralateral carotid artery on the neck (a–c)
Fig. 3.185a–c Examination of collateral blood flow in patients with arterial aneurysms. Left internal carotid artery aneurysm (a,b), anterior cerebral–anterior communicating artery aneurysm (c). The examination estimated the blood reflow with compression of the contralateral carotid artery on the neck
Fig. 3.186a–c Turbulent flow in large arterial aneurysms according to digital angiography data: the infraclinoid segment of the internal
carotid artery (a), supraclinoid segment (b), basilar artery (c)
Cerebrovascular Diseases and Malformations of the Brain
221 Fig. 3.187a,b Microaneurysm of the anterior cerebral–anterior communicating arteries. Digital angiography in lateral (a) and oblique (b) projections. The aneurysm is indicated by the arrow
plex, and therefore the important moment in angiography is estimation of the intra-aneurysmal blood flow, which is one of the factors in preoperational planning of the endovascular occlusion (Fig. 3.186). Furthermore, AA that are 1–2 mm in diameter are usually detected only with the use of cerebral angiography (Fig. 3.187).
Fig. 3.188 Arterial aneurysm of the internal carotid artery. 3D reconstruction of digital AG data
The new breakthrough in digital angiography was made with the invention of the 3D method of data collection and reconstruction with subsequent computer processing of obtained info (Ernemann et al. 2000; Hochmuth et al. 2002) (Fig. 3.188). However, it should be noted that even with use of digital angiography, the reason for subarachnoid haemorrhage remains unknown in 10–25% of cases. The control examination is preferably performed with the use of less invasive techniques like MR and CT angiography. Other important data obtained with the use of digital angiography are assessment of cerebral circulation and the AA “switching off ” after surgery. Employment of amagnetic clips and spirals after operational assessment is more frequently done with the help of non-invasive techniques such as CT and MRI angiography. CT is the method of a choice in the express diagnosis of AA in the majority of the diagnostic centres. In the acute phase, CT detects blood accumulation in subarachnoid spaces (subarachnoid cisterns, interhemispheric fissure, the lateral brain fissures and convex subarachnoid spaces) primarily on the side of the ruptured aneurysm. The CT data are especially valuable in cases of intracerebral and intraventricular blood clots. It is possible to identify the site of AA based on data of predominant blood accumulation in one of the segments of the lateral ventricle or subarachnoid space. In cases of the rupture of AA in the anterior communicating artery, blood and clots are located in the cistern of the terminal plate, interhemispheric fissure or septum pellucidum, in the third and fourth ventricles, and the inferior medial segments of frontal lobe (Fig. 3.189). After the rupture of AA in the initial segment of the pericallosal artery, blood accumulates in the distal part of interhemispheric fissure, in the corpus callosum or cingulate gyrus. In extremely rare cases, such blood accumulation can be observed with the help of CT in cases of rupture of anterior
222
Chapter 3
Fig. 3.189a–c CT in the acute stage of subarachnoid haemorrhage from aneurysm of the anterior cerebral and anterior communicating
arteries. Hyperdense areas in the frontomediobasal region are visualised, more leftwards
cerebral artery–anterior communicating arteries (Fig. 3.190). The rupture of AA in posterior communicating artery leads to diffusive blood accumulation in the basal cisterns, low horn of the lateral ventricle and haemorrhage forms in basal ganglia and the medial part of temporal lobe. Blood accumulation in the lateral brain fissure on the one side and the formation of haemorrhage in the temporal lobe with spreading to the inferior horn of the lateral ventricle are observed in cases of rupture of AA in the bifurcation of internal carotid artery or middle cerebral artery (Fig. 3.191). Bleeding from the basilar artery AA leads to diffusive blood accumulation in cisterns of base of brain, with clots in the interpeduncular cistern, midbrain and hypothalamus. Sometimes the blood ruptures into the third ventricle. Haemorrhage from aneurysms of the posterior inferior cerebellar artery can be detected when blood is found in the cisterns around brainstem, or clots in the fourth ventricle or haemorrhage in the cerebellar hemisphere is seen. CT potential in AA detection is limited by the size of aneurysm. It is difficult to diagnose aneurysms with the diameter less than 2.5 mm with CT. An aneurysm larger than 2.5 mm is visible with CT as a focus of slightly increased density adjacent to the cerebral vessel. Intravenous contrast enhancement increases the AA density (Figs. 3.192, 3.193). They often contain thrombotic masses that on CT look denser than surrounding circulating blood. Calcifications in the walls of giant aneurysms are denser in comparison with the parietal thrombi (Fig. 3.194). Contrast enhancement considerably increases the density of a functioning part of an aneurysm and, as a result, the latter gains appearance of a laminated structure that differs from that gained with standard CT (Fig. 3.195). CT identifies the areas of ischaemia caused by vasospasm. It is possible to make judgments regarding the particular vessels affected by vasospasm, based on the location of the ischaemic area. Follow-up CT examinations help to trace the development of the ischae-
mic process (regression or progression) under the influence of therapy. Giant AA quite often tends to grow, i.e. clinically, they behave like slowly growing tumours. In such cases, CT helps to differentiate a giant aneurysm from a tumour, based on location, appearance and density before and after contrast enhancement. Sometimes giant AA of the siphon or the supraclinoid segment of internal carotid artery are located in the medial part of middle cranial fossa or sella turcica area, and they can be mistakenly considered as tumours: meningioma, glioma of the optic chiasm, pituitary adenoma and craniopharingioma (Fig. 3.196). The use of an angiography mode on spiral CT (White et al. 2001; Yoon et al. 2007) with the subsequent mathematical processing locates not only the aneurysm itself and its interaction with the surrounding tissues (bone structures, brain tissue, vessels), but also defines its form, reveals the aneurysm’s neck, the orientation of the bottom and the presence of thrombotic masses in its cavity (Figs. 3.197–3.200). MRI picture of AA varies and depends on aneurysm sizes, speed and direction of blood flow in its cavity, presence or absence of blood clots in its sack and also on the residual signs of haemorrhages. Taking into account the variability of appearance of saccular aneurysms of brain vessels in standard MRI examination, we have found it appropriate to divide them into categories depending on the degree of aneurysm’s cavity filling by the thrombotic masses: functioning, partially and completely filled by the thrombi (Figs. 3.201–3.203). Undoubtedly, there is a correlation between the aneurysm presentations of standard SE sequences and in MRA that uses gradient-echo sequences. Such a subdivision—from our point of view—is justified because MRI, unlike CT, can better differentiate between the functioning part of aneurysm’s sack and the part filled with thrombotic masses. In standard modes that use the pulse SE sequence (T1- and T2-weighted images), signal loss is typical for fully function-
Cerebrovascular Diseases and Malformations of the Brain
223
Fig. 3.190a–c Acute haemorrhage around corpus callosum after rupture of the anterior cerebral and anterior communicating artery aneurysm. a Digital AG, b,c CT. The aneurysm is indicated by the arrow
Fig. 3.191a–f Variant of location of haemorrhages after rupture of aneurysms. DSA and CТ: the middle cerebral artery (a,b), the internal
carotid artery bifurcation (c,d), series of CТ after rupture of supraclinoid segment of the internal carotid artery (e), CT after rupture of the middle cerebral artery bifurcation (f)
224
Chapter 3
Fig. 3.192a–c Giant arterial aneurysm of the basilar artery. Cerebral АG (a), CT without (b) and with (c) contrast enhancement demonstrate
homogeneous hyperdensity of the aneurysmal sack
Fig. 3.193a,b Arterial aneurysm of the middle cerebral artery. A series of CT scans without (a) and after (b) contrast enhancement–increased hyperdensity of arterial aneurysm (arrow)
Fig. 3.194a–c Variants of arterial aneurysms of cerebral brain vessels with calcifications nations of walls. Aneurysm of the right vertebral artery detected by CTA (a,b), aneurysm of the right internal carotid artery detected by CT with contrast enhancement (c,d), d-f see next page
Cerebrovascular Diseases and Malformations of the Brain
225
Fig. 3.194d–f (continued) and giant aneurysm of the middle cerebral artery before (e) and after (f) contrast enhancement on CT images
Fig. 3.195a–f Aneurysm of the basilar artery. On CT before (a) and after contrast enhancement (b): a functioning part of the aneurysm is visualised (arrow). Giant aneurysm of the left middle cerebral ar-
tery: on CT before (c) and after (d) contrast enhancement a functioning part of the aneurysm becomes vivid, 3D reconstruction (e,f) with volume-rendering software in the same patient
226
Fig. 3.196a–f Arterial aneurysm of the right internal carotid artery. CТ (a,b) without contrast enhancement and CTA (c,d) reveal a round mass in the right laterosellar region resembling a cranio-
Chapter 3
pharingioma. Observation of the cavernous segment of the internal carotid artery aneurysm simulating meningioma of sinus cavernosus (e CT, f DSA)
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.197a–f CTA in different variants of arterial aneurysms. Case
1. The anterior cerebral and anterior communicating arteries: axial reformation (a), multiple aneurysms (b) of the circle of Willis: the anterior cerebral–anterior communicating artery, the left internal
227
carotid artery (arrows). Case 2. Reformation in coronal plane: aneurysm of anterior cerebral and anterior communicating arteries (c). Case 3. Axial and sagittal reformation in the anterior cerebral and anterior communicating artery aneurysm (d–f)
228
Chapter 3
Fig. 3.198a–d Aneurysm of the basilar artery. Digital AG (a,b), sagittal and coronal reformation in CTA (c,d). CT additionally shows a non-functioning part of the aneurysm (arrow)
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.199a–f Partial functioning of the left internal carotid artery
aneurysm in a 13-year-old child. Carotid (a) angiography: borders of the sack aneurysm are uneven due to partial thrombosis. CT reformation (b,c) in sagittal and coronal projections: large sack aneurysm of the posterior wall of the internal carotid artery suprasellar
229
segment, spiral CT (d) in 3D reconstruction (Navigator software): spatial relationships of the internal carotid artery aneurysm and the anterior clinoid process. Virtual (e) endoscopy: borders of the sack aneurysm are uneven due to thrombotic masses. MRI 3D (f) reconstruction (Navigator software)
230
Chapter 3
Fig. 3.200a–e Case 1. Arterial aneurysm
of the middle cerebral artery: CT without (a) and with (b) contrast enhancement, 3D reconstruction (c). d,e Case 2. Aneurysm of the basilar artery (MIP and 3D)
Fig. 3.201a–c Arterial aneurysm of the internal carotid artery supraclinoid segment. Т2-weighted imaging (a) and MRA (b,c). There is a
typically hypointense functioning part of the aneurysm. No signs of a part of aneurysm with thrombosis
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.202a–c Partial thrombosis of the anterior cerebral–anterior communicating artery aneurysm. Т2-weighted imaging (a), Т1-weighted imaging (b) and in sagittal plane Т1-weighted imag-
231
ing (c) show an area of signal change from the sack of aneurysm with concomitant peripheral subacute haemorrhage (arrow). Mural thrombus is seen on Т1-weighted imaging in the aneurysm
Fig.3.203a–f Giant partially filled arterial aneurysm of the left middle cerebral artery. Т2-weighted imaging (a) and Т1-weighted imaging
(b), CT before (c,d) and after injection of contrast medium (e), and DSA (f) reveal the pathology. MRI and CT are better than DSA in the demonstration of the aneurysm’s structure
232
ing aneurysms and also for the site in the arterial vessel from which the aneurysm originates. The heterogeneity of MR signal due turbulent blood flow in the aneurysm’s cavity is observed in large AA on T1- and T2-weighted images. On these images, the pulsatile artefact in the form of a strip of repeating aneurysm contours moving in the phase-encoding direction is a typical feature of a functioning aneurysm (Fig. 3.204). MRA with 3D TOF pulse sequence, which registers high signal from fast-moving blood, is the most sensitive technique in MRI imaging of AA. Subsequent computer processing of the set of raw data creates the reconstruction of the vessel net and makes possible its rotation under any angle; this helps the neurosurgeon to clarify almost all important features of
Chapter 3
the AA: the site the neck, and the orientation of the bottom (Bosmans et al. 1995; Atlas et al. 1997). It is especially evident in case of a marked aneurysm’s neck (Figs. 3.205–3. 207). The smallest aneurysm that we are able to detect with help of MRA is the aneurysm 1 mm in diameter. Additional computer processing (on the workstation) helped with this process (Figs. 3.208, 3.209). MR signal may be significantly decreased in cases of slow blood flow and in cases of turbulence inside of large or giant aneurysms. In these situations, paramagnetic contrast administration can greatly improve imaging of an aneurysm on standard T1 sequence, homogeneously amplifying its MR signal (Figs. 3.210, 3.211).
Fig. 3.204a–c Completely functioning arterial aneurysms (different patients). Т2-weighted imaging. Pulsatile artefacts in the phase-encod-
ing direction are clearly visualised (arrows) Fig. 3.205a,b Arterial aneurysm of the ACA. Т2-weighted imaging (a) and 3D TOF MRA raw data (b) show a completely functioning arterial aneurysm
Cerebrovascular Diseases and Malformations of the Brain
233
Fig. 3.206a–c Arterial aneurysm of the internal carotid artery. Т1-weighted imaging (a): subarachnoid haemorrhage in the left Sylvian fissure (hyperintense areas). Axial and sagittal (b,c) reformation of MRA data: small (3 mm) sack aneurysm (arrows)
Fig. 3.207a–f Arterial aneurysm of the anterior cerebral–anterior
communicating arteries. Cerebral АG in coronal projection (a) shows a small aneurysm. Т2-weighted imaging (b) and Т1-weighted imag-
ing (c): there is an intracerebral haemorrhage in the right frontobasilar region. On 3D TOF MRA (d–h), there is an irregular-shaped aneurysm (arrows). g–l see next page
234
Chapter 3
Fig. 3.207g–l (continued) 3D reconstruction gives a better spatial resolution (i–k), 3D PC MRA does not allow visualisation of the aneurysmal sack (l)
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.208a–f Variants of arterial microaneurysms. Case 1. Aneurysm of the anterior cerebral–anterior communicating arteries on Т2-weighted imaging (a). 3D reconstruction (b): aneurysmal sack is indicated by arrow. Case 2. MRA (c,d): microaneurysm of the ante-
235
rior cerebral–anterior communicating artery. Aneurysm is reliably visualised only after 3D (d) reconstruction (arrow). Case 3. Microaneurysm of the medial surface of the internal carotid artery siphon (2 mm in size), indicated by arrow. e,f MRA
236
Chapter 3
Fig. 3.209a–d Arterial microaneurysm of the internal carotid artery bifurcation. CT shows (a) acute basal subarachnoid haemorrhage. Т1-weighted imaging (b): acute subarachnoid haemorrhage is not visualised. MRA (c) in 3D TOF–small aneurysm (arrow) has sizes identical to those detected on direct AG (d)
Cerebrovascular Diseases and Malformations of the Brain
237
Fig. 3.210a–f Arterial aneurysm of the left internal carotid artery siphon. Т1-weighted imaging before (a–c) and after (d–f) contrast enhancement reveals marked hyperintense signal from the functioning part of the aneurysm after enhancement
238
Chapter 3
Fig. 3.211a–f Giant saccular aneurysm of the right internal carotid artery. Т2-weighted imaging (a,b), Т1-weighted imaging before (c) and
after (d) contrast enhancement. MRI detects a giant completely functioning aneurysm, and MRA 3D TOF (e,f) shows the aneurysm only partially due to marked turbulent flow within its cavity
It is noteworthy that contrast enhancement in AA diagnosis should be used in the last stage of MRI examination after MRA, because enhancement of the bloodstream in 3D TOF technique simultaneously increases the signal from arteries, and veins resemble each other. Therefore, subsequent 3D reconstruction of arteries is seriously complicated by a venous presence in the reconstructed picture. In MRI diagnosis of the completely functioning AA, 3D PC technique can be also used, and it better visualises large and giant aneurysms because it lacks the limitation peculiar to 3D TOF, in which heterogeneity of MR signal worsens imaging of the cavity. Moreover, 3D PC techniques enables conducting examinations with different encoding of the speed of blood flow in vessels of special significance in cases of slow circulation in the AA cavity. The main limitation of this technique is slow (in comparison with 3D TOF) spatial resolution (AA less than 10 mm in diameter are poorly imaged) and longer (two times) examination time for 3D mode. In cases of AA partially filled with thrombi, standard MRI reveals the heterogeneous signal related to the ratio of vol-
ume of the functioning part of an aneurysm and features of thrombotic masses. The part of aneurysm filled with thrombi has iso- or hyperintense MR signal on T1-weighted images, depending on the phase of clot formation. In T2-weighted imaging the thrombi may have hyper- or hypointense signal. The gradual formation of thrombi near the vessel wall leads to the phenomenon of laminated MR signal in the AA cavity (Figs. 3.212–3.215). Due to haemosiderin accumulation in the AA wall, it has a low signal on all sequences. (It is better visualised on T2- and T2*-weighted images.) It is difficult to differentiate the functioning part of AA and the part filled with thrombi on MRA (3D TOF); therefore, standard MRI data should be compared with the “raw” MRA data, or it is necessary to carry out the additional 3D PC techniques (Figs. 3.216, 3.217). AA, completely filled with thrombi (although it is an extremely rare phenomenon) may have the same MR characteristics as a tumour, and that complicates their differentiation. Meanwhile, in the overwhelming number of cases, MRI reveals the signs that point to AA. MRA plays a limited role in cases of AA completely filled with thrombi. In these situations,
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.212a–c Giant arterial aneurysm of the left middle cerebral artery bifurcation. Т2-weighted imaging (a), FLAIR (b) and Т1-weighted imaging (c) demonstrate a laminated character of thrombotic masses
239
into the aneurysmal cavity. The functioning part of the aneurysm is hypointense in all sequences. Perifocal oedema is also revealed
Fig. 3.213a–c Partial thrombosis of the right internal carotid artery bifurcation aneurysm. Digital angiography (a) in lateral projection, 3D TOF MRA (b) and Т2-weighted imaging (c) demonstrate an unusual appearance of the aneurysm with thrombosis in its central part
Fig. 3.214a–c Giant arterial aneurysm of the right internal carotid artery siphon. Т2-weighted imaging (a,b) and MRA 3D TOF (c) show the partial thrombosis of the aneurysm, the majority of its cavity being filled with thrombotic masses
240
Chapter 3
Fig. 3.215a–c Arterial aneurysm (with partial thrombosis) of the right vertebral artery. Т2-weighted imaging (a), and Т1-weighted imaging
before (b) and after (c) contrast enhancement: there is an aneurysm with small functioning part (arrow)
Fig. 3.216a–c Partial thrombosis of the giant aneurysm of the left
middle cerebral artery. Т2*-weighted imaging (a) reveals a large aneurysmal sack, preferably represented by thrombotic masses formed at different times. Peripheral zone is hypointense (haemosiderin de-
posits). 3D TOF (b) demonstrates the effect of pseudo-enhancement of methaemoglobin in the part with thrombosis. It was not possible to visualise the functioning part of the aneurysm by 3D PC (c)
Cerebrovascular Diseases and Malformations of the Brain
241
Fig. 3.217a–f Complete thrombosis of the posterior cerebral–posterior communicating artery aneurysm. Т2-weighted imaging (a,b), Т1-weighted imaging (c,d), 3D TOF MRA (e) and 3D PC (f) reveal an aneurysm with complete thrombosis, visualised on 3D TOF MRA due to methaemoglobin presence
242
there are signs of the influence of a mass lesion on neighbouring vessels (Fig. 3.218). In general, MRA, due to its high resolution, non-invasiveness and the possibility of 3D reconstruction and navigation, yields high-quality images of brain vessels and detects all variants of location and structure of saccular aneurysms (Figs. 3.219–3.222). In some cases—especially in situations with a multiple peripheral aneurysms and intense atherosclerosis that complicate the selective catheterisation of cerebral arteries—MR and CT angiography can replace total cerebral angiography (Fig. 3.223, 3.224). The presence or absence of changes that accompany aneurysm, such as acute and subacute haemorrhages, sequelae of
Chapter 3
the old haemorrhages with gliosis changes in the surrounding brain tissues, ischaemic foci and other vascular lesions, are features the imaging of which is extremely important for the precise diagnosis of AA (Figs. 3.225, 3.226, 3.227). The problems complicating CT diagnosis of arterial aneurysms in the acute phase are the intracerebral haemorrhages and massive subarachnoid bleedings with increased density that can hide aneurysm. Comparing CT and MRA, one can conclude that the use of MRA with 3D TOF and magnetisation transfer suppression (MTS) technique in acute subarachnoid haemorrhage is superior to CT angiography. However, considering the fact that as a rule, patients during this period are in a severe condition, appropriate sedation is
Fig. 3.218a–c Complete thrombosis of the right middle cerebral artery aneurysm. Т2-weighted imaging (a) and Т1-weighted imaging (b)
demonstrate the round area of signal change. Direct angiography failed to reveal the functioning part of the aneurysm (c). The presence of aneurysm was proved by surgery
Fig. 3.219a–c Arterial aneurysm of the anterior cerebral and anterior communicating arteries. 3D TOF MRA (a): axial reformation, 3D
reconstruction (b,c) under different angles. A thin neck of a sack aneurysm is clearly seen (arrow)
Cerebrovascular Diseases and Malformations of the Brain
243
Fig. 3.220a–c Aneurysm of the basilar artery. Т2-weighted imaging (a) and 3D TOF MRA (b,c) show arterial aneurysm with a wide neck
and partial thrombosis
Fig. 3.221a–f Aneurysm of the left vertebral artery at the site of origin of the posterior inferior cerebellar artery. Т2-weighted imaging (a) and 3D TOF MRA with subsequent reconstruction (b–f) demonstrate an arterial aneurysm in the ostium of the posterior inferior cerebellar artery (arrow)
244
Chapter 3
Fig. 3.222a–c Aneurysm of the right middle cerebral artery bifurcation. MRA MIP reformation (a) and 3D reconstruction (b,c) show the
aneurysm at the site of the right middle cerebral artery bifurcation (arrow). Relationship of the aneurysm and the artery is better demonstrated on 3D reconstruction
Fig. 3.223a–d Multiple aneurysms of cerebral vessels. Case 1. Т2-weighted imaging (a)
and 3D TOF MRA (b) demonstrate arterial aneurysms in the sites of the anterior cerebral–anterior communicating arteries and the middle cerebral artery bifurcation. Case 2. CTA 3D reconstruction (c) and MIP reconstruction (d) reveal the aneurysms of both middle cerebral arteries’ bifurcations (arrows)
Cerebrovascular Diseases and Malformations of the Brain
245
Fig. 3.224a–f Peripheral arterial aneurysm of the temporal branch of the middle cerebral artery. Т2-weighted imaging (a), Т1-weighted im-
aging (b) and 3D TOF MRA under different angles (c–f): there is a partially functioning aneurysm (arrow). Perifocal oedema is visualised around the aneurysm
Fig. 3.225a–c Aneurysm of the anterior cerebral–anterior communicating arteries. On Т2-weighted imaging (a–c) the aneurysm is hypoin-
tense. The hyperintense area in the right temporal lobe within optic tract and internal capsule indicates ischaemic change
246
Fig. 3.226a–c Arterial aneurysm of the right posterior cerebral artery. CT (a), Т2-weighted imaging (b) and 3D TOF MRA (c): there is a giant partially functioning aneurysm surrounded by perifocal oe-
Chapter 3
dema. There is a dislocation of median structures and compression of ventricular system. Visualisation of the aneurysm on MRA is due to phenomenon of pseudo-enhancement Fig. 3.227 Post-ischaemic changes in the left temporal lobe in a patient with multiple cerebral artery aneurysms. Т2-weighted imaging demonstrates a hyperintense area in the insular lobule of the temporal lobe
necessary to avoid motion artefacts. In our opinion, it is appropriate to use CT as a screening method for identification of a concomitant haemorrhage (Figs. 3.228, 3.229). The lysis of blood in subarachnoid haemorrhages passes through certain stages that are reflected on MRI and CT, in certain periods worsening the quality and precision of AA diagnosis. Methaemoglobin is formed in subacute haemorrhages. It has high MR signal and hides the contour of an aneurysm,
thus limiting the potential of this method in the given period (Figs. 3.230–3.232). Taking this into account and based on our experience in AA diagnostics, after the haemorrhage in the acute phase of subarachnoid haemorrhage, it is appropriate to use routine CT and 3D TOF MR angiography, and in the subacute stage, CT angiography in combination with MRA (3D PC). In the chronic phase, we prefer to use MRA in a 3D TOF technique as the non-invasive method, although the potential
Cerebrovascular Diseases and Malformations of the Brain
247
Fig. 3.228a–e Aneurysm of the anterior
cerebral and anterior communicating arteries in a patient with acute subarachnoid haemorrhage (day 2). CT (a) demonstrates blood in the brain-base subarachnoid spaces. Blood is detected on Т1-weighted imaging (b) and Т2-weighted imaging (c), and the aneurysm itself is seen (arrow). Relationship of the aneurysm and the ACA on MRA is better demonstrated in 3D TOF (e,d), than in 3D PC (e) regimen
of CT and MRA are practically identical. The use of MRA is undoubtedly more preferable in patients with an allergy to iodine contrast.
3.16 Intracranial Vascular Malformations Classically, vascular malformations are subdivided into four main categories: AVM, cavernous angioma, capillary telangiectasia and venous malformations. (Dural arteriovenous fistulas belong to a separate category.) The first attempts to create a classification of the brain vessel malformations were completed long ago; therefore, now there are a sufficient number of the classifications based on various principles and approaches. All of them to some extent reflect the completeness of the medical knowledge concerning diagnostics and treatment of the vascular malformation on the certain stage of development: pathological, demographic,
anatomic, haemodynamic, clinical, surgical and, finally, radiological aspects. Among all classifications, the most popular for neurosurgeons are those based on the information about malformation location, its size, sources of supply, ways of venous outflow and its interaction with the functionally important brain areas. According to these data, the question about the indications for treatment method, type of operational access and tactics of malformation excision is being solved. The best recognition was earned by the classification of Spetzler and Martin in 1986. In Russia, Matsko (1991) proposed dividing vascular malformations of brain and spinal cord into angiomatous, non-angiomatous and unclassified malformations. Recently, neuroradiologists (Valavanis 1996; Chaloupka and Huddle 1998; Osborn 1999) have offered a new classification that takes into consideration clinical, anatomical and histological data, biological behaviour and visual characteristics of vascular malformations. This classification is based on the
248
Fig. 3.229a–f Arterial aneurysm of the middle cerebral artery (day
2 after haemorrhage). CТ image with contrast enhancement (a) and Т1-weighted imaging (b) demonstrate a small sack aneurysm of the middle cerebral artery bifurcation (arrow), and a large intra-cerebral haemorrhage is seen behind the aneurysm. On 3D TOF MRA with
Chapter 3
MIP (c,d) and 3D reconstruction (e): there is a dumbbell-shaped aneurysm with a wide neck. The pseudo-enhancement effect of the haemorrhage does not prevent visualisation of the aneurysm. The shape of aneurysm according to cerebral AG (f) completely coincides with MRA data
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.230a–e Aneurysm of the anterior cerebral and anterior com-
municating arteries, 10 days after haemorrhage. Т1-weighted imaging (a) and Т1-weighted imaging (b): there is blood accumulation in frontobasilar region, more rightwards, and hyperintense signal in Т1-weighted imaging of methaemoglobin prevents visualisation of
249
the aneurysm. 3D TOF MRA (c) quality is not ideal. In 3D PC regimen functional part of aneurysm is well depicted (d). Digital AG (e) confirms the presence of irregular-shape aneurysm of the anterior cerebral and anterior communicating arteries
250
Chapter 3
Fig. 3.231a–c Aneurysm in the anterior cerebral–anterior communicating arteries, day 8 after haemorrhage. Т1-weighted imaging (a) and Т2-weighted imaging (b) reveal a small aneurysm (arrow), with hyperintense signal of a haemorrhage, however, aneurysm is seen on 3D TOF MRA (c), but its relationship with arteries is difficult to assess
Fig. 3.232a–e Aneurysm of the middle cerebral artery. The 9th day
after haemorrhage. Т1-weighted imaging (a): there is a markedly hyperintense area in the left temporal region (оf methaemoglobin), that almost completely prevents visualisation of the functioning part of aneurysm in 3DTOF (b,c). On CTA with further planar reformation
(d), it is possible to detect the functioning part of aneurysm (arrow) on the background of the old haemorrhage with calcinated walls. Digital AG (e) confirms the presence of a small aneurysm of the middle cerebral artery (arrow), and absence of this artery’s branches on imaging makes the case for thrombosis
Cerebrovascular Diseases and Malformations of the Brain
presence or absence of the vascular shunting in malformation; this can serve as the basis or indication for treatment (open surgical, endovasal, radiotherapy). 1. Malformations with arteriovenous shunting a. Arteriovenous malformations i. Plexiform node ii. Mixed plexiform–fistula node b. Arteriovenous fistula i. Single or multiple fistula(s) ii. Mono- or multipeduncular 2. Malformation without arteriovenous shunting a. Capillary (telangiectasia) b. Venous malformations i. Venous angioma ii. Venous varix (without relation with malformation and dural arteriovenous fistulas) c. Cavernous malformation
3.16.1 AVM AVM are congenital abnormalities of vessel development. The base of AVM is a tangle of pathological vessels in which the
251
direct dump of arterial blood into venous system is carried out. As a rule, in glomera of AVM, normal brain tissue is not detected, except for small islands of gliosis that can be found in AVM on light microscopy. Microscopic examination reveals that AVM has no capillary net, and the dilated arteries immediately pass to drainage veins. Walls of pathologically changed vessels can be irregularly thickened or thinned. In the arterial vessels, the most evident structural changes starting from uneven thickening of a muscular layer and vessel’s intima to marked attenuation or complete disappearance of the elastic membrane are observed. Vessels of the venous type, as a rule, are widened; the main layers of the vascular wall are attenuated. The secondary accompanying changes of a brain, such as the traces of old haemorrhages, gliosis and hyperplasia of glia, are often detected around the AVM. AVM are one of the frequent causes of repeated haemorrhages that can lead to haemorrhage. AVM are mainly located in the cerebral hemispheres (85%); only 15% are located in the posterior cranial fossa (Fig. 3.233). Thus, according to Lysachev (1988), 364 patients with supratentorial AVM who were examined and treated in the Burdenko Neurosurgical Institute had AVM in the follow-
Fig. 3.233a–f Arteriovenous malformation in the frontoparietal region. Digital AG (a–c). System of afferent and efferent vessels is fairly well visualised. Arteriovenous malformation of subtentorial region in the arterial and venous phases (d–f)
252
Chapter 3
Fig. 3.234a–c Rendu-Osler-Weber disease. A large arteriovenous malformation of the left parieto-occipital region
Fig. 3.235a–f Variants of cerebral arteriovenous malformations. Micromalformation of the posterior cerebral artery (a), small malformation
in the posterior circulation system (b), moderate size (c,d) and large (e, f) malformations of MCA
Cerebrovascular Diseases and Malformations of the Brain
253
ing locations: area of central gyri (38%), temporal–occipital lobes, (18%), basal ganglia (17%), corpus callosum (14%) and parietal lobe (13%). It is necessary to note that quite often the AVM occupy two or even sometimes three neighbouring brain areas. Despite the congenital character of the majority of AVM, they clinically manifest within the interval of 20–40 years. In the United States, about 2,500 new cases of brain AMV are diagnosed annually (Osborn 1999). AVM as a rule are single formations, and multiple aneurysms are observed only in 2% of all cases. In the majority of cases, they are signs of Rendu-Osler-Weber (ROW) or Wyburn-Mason (WM) syndromes. ROW syndrome is characterised by multiple capillary telangiectasias on the surface of skin and mucous membranes, an arteriovenous fistula in the lung and parenchymal intracerebral AVM. According to Berenstein et al. (1992), this complex of symptoms in patients with multiple AVM is revealed in 25% of cases. As a rule, these patients are young (more than 50% of them are less than 16 years old). Diagnosis is established based on skin and visceral signs of disease and not by angiography findings (Fig. 3.234). In patients with WM syndrome, brain AVM, multiple retinal AVM and skin nevi are observed. In some cases, the retinal AVM spread along optic nerve and affect the thalamus and hypothalamus. Some authors distinguish non-system multiple brain AVM as a separate form of pathology. By their size, all AVM are divided into micromalformations (less than 1 cm in diameter, the size of supplying arteries and draining veins are normal and often they are not revealed during the surgical interventions) and macromalformations; the latter, as opposed to the former, have arteries and veins that exceed typical sizes. If the node’s diameter is 2–4 cm, then they are considered as small, nodes with 2–4 cm are moderate, 4–6 cm are large and those exceeding 6 cm are categorised as giant (Fig. 3.235).
In AVM clinical manifestation, the most frequent sign is spontaneous intracranial haemorrhages; the incidence varies from 67% (Filatov 1973) to 78% (Yasargil 1987). The subarachnoid haemorrhages are diagnosed most frequently, then the intracerebral, and then the intraventricular ones (Figs. 3.236, 3.237). The risk of AVM rupture fluctuates by 2–4% during 1 year. However, analyses of large observations series demonstrates that frequency of disability and mortality after spontaneous intracerebral haemorrhages reach 50%. Predisposing factors of AVM rupture are past haemorrhages, AVM draining into deep brain veins, the presence of aneurysmal sacks in the structure of AVM, and hypertension. According to the opinion of the several authors, AVM size influences the possibility of vascular wall rupture and haemorrhage onset: with a smaller size, the percentage of spontaneous haemorrhages is higher (Langer 1998). Other researches, however, found no correlation between AVM size and the probability of its rupture (Pollock 1996). The second most frequent clinical sign is an epileptic syndrome of a various degree of intensity. According to different data, epileptic seizures in patients with AVM are observed in 25–50% of cases. In some cases, the gradual albeit steady progression of focal neurological signs is reported, and the symptoms actually depend on location (Lysachev 1988). These are motor function disorders (pyramidal and extrapyramidal), speech disturbances, and sensitivity, psychopathological, organic and visual impairments. In cases of small AVM located in the deep structures (caudate nucleus, thalamus, cingulate gyrus, corpus callosum, hippocampus), the impairment of mental functions is the most frequent type observed in such patients (180 observations with AVM; Buklina 2001). Selective cerebral angiography with the examination of territories of all cerebral arteries plays the leading role in AVM diagnostics. It reveals the AVM structure and accompanying
Fig. 3.236a–c Arteriovenous malformation of the pericallosal artery
the outflow proceeds into the internal cerebral vein. A series of CT scans (c) of the same patient demonstrate a large intracerebral haemorrhage of the right posterior frontotemporal region
with haemorrhage. Digital AG (a,b) in lateral projection demonstrates a micromalformation, supplied by the pericallosal artery, and
254
Chapter 3
Fig. 3.237a–c Arteriovenous malformation of the left ACA. Coronal and lateral DSA (a,b). A large malformation is seen in the arterial phase. The terminal branches of the ACA supply it with blood.
A series of CT scans (c) of the same patient reveals a large intracerebral haemorrhage of the right frontoparietal-temporal region with dislocation
Fig. 3.238a–f Examination of the brain blood-supply peculiarities in
projections in the venous phase on the side of aneurysm–efferent vessels of malformation are visualised. The study of posterior circulation when the common carotid artery is compressed on the side of aneurysm (f)
case of arteriovenous malformations. AG (a) of the side of aneurysm (lateral projection), carotid AG (b) of the contralateral arterial area (AVM also is filled with contrast), АG (c) in the capillary phase on the side of aneurysm (coronal projection), coronal and lateral (d,e)
Cerebrovascular Diseases and Malformations of the Brain
changes in brain circulation. The general examination describes the whole picture, while the detailed study of the AVM nodes are performed with the use of microcatheter technique (Figs. 3.238, 3.239). On cerebral angiograms, AVM look like pathological lesions of various forms, diameters and spatial orientation of the vessels. They consist of dilated arterial trunks that participate in supplying the main AVM node. The superselective angiography provides details about an AVM angio-architecture and reveals the accompanying vessel pathology (angiopathy of the supplying arteries and the presence of the saccular aneurysms). There are several types of AVM structure. Afferent arterial vessels sometimes can directly enter into one or more vascular cavities inside an aneurysmal node (Figs. 3.240, 3.241). However, more frequently, large arteries are divided into numerous smaller vessels, which surround a saccular vascular cavity and then enter into it from various sides, thus forming compact or loose vascular tangle plexiform types (Figs. 3.242, 3.243). Inside AVM, vascular cavities can be single or multiple; they can form saccular aneurysms, posthaemorrhagic arterial or venous pseudo-aneurysms, or venous ectasia. Berenstein et al. (1992) described two basic types of AVM arterial blood supply: (1) direct, in which the supplying artery enters into a shunting area and itself is a final brunch; and (2) indirect, in which an artery supplies the certain brain area, and only its separate branches take part in a supply of arteriovenous node (Fig. 3.244). The joint supply of cerebral AVM from intracranial arteries,
255
dural arteries and even extracranial ones is not an infrequent finding (Fig. 3.245). According to some authors, the share of such jointly supplied AVM reaches from 27 to 32% of all brain AVM (Newton 1969; Willinsky 1988). There are some explanations for this phenomenon. The postoperative changes with formation of defects and commissures in the neighbouring dural vessels with their subsequent involvement into pathological process are one such explanation. However, the theory of involvement of dural arteries into AVM after partial embolism of the main malformation node has more supporters. Such involvement is possible as a consequence of post-ischaemic changes in brain tissue, with subsequent angiogenesis stimulation. Subarachnoid haemorrhage can also facilitate the reorganisation of intracerebral AVM blood supply. The best way to assess AVM topography is to use a combination of direct angiography data and results of CT and MRI. It is obvious that AVM located in certain brain area is connected with arteries and veins supplying that area in norm. In the literature, it is acceptable to divide AVM into several types, based on their topography: • AVM that reaches the cortex • Deeply located AVM • AVM of choroid plexus The first group is the largest one; it contains cortical AVM, corticosubcortical AVM and corticoventricular AVM including shunts located in corpus callosum (Fig. 3.246). The most frequent location for deep AVM is deep cerebral grey matter, brainstem and grey matter of cerebellum. These
Fig. 3.239a–e Digital AG in AVM of the
right parietal region. Coronal and lateral (a,b) angiograms demonstrate hypertrophy of those arterial branches that supply mal formation from the anterior and middle cerebral artery territories, superselective study of separate AVM vessels (c–e)
256
Chapter 3
Fig. 3.240a,b The first structural type of AVM. AG of the right and the left carotid territories reveals the direct type of the afferent vessel
shunting into the dilated venous cavity
Fig. 3.241a–c The first structural type of AVM. DSA in lateral projection in the early arterial and late arterial and venous phases demonstrates an extensive AVM, supplied from the hypertrophied branch of the middle cerebral artery. This branch directly flows into the dilated venous cavity with further formation of numerous enlarged veins
Cerebrovascular Diseases and Malformations of the Brain
257
Fig. 3.242a–f The second type of AVM with fine vascular net (“plexiform” appearance). DSA reveals AVM in the posterior frontal (a,b) and temporal right regions (c–f) with supply from the middle and posterior cerebral arteries branches
258
Chapter 3
Fig. 3.243a–f AVM of the right posterior cerebral artery. Cerebral AG in coronal (a–c) and lateral (d–f) projections demonstrate prominent
hypertrophy of the posterior cerebral artery supplying a large AVM in the occipital lobe. Haemodynamic aneurysm of the same posterior cerebral artery is additionally seen
Fig. 3.244a,b Schematic representation of types of arterial blood supply in AVM: the first type–direct shunting (a), indirect shunting “en passage” (b). (Illustration according to A. Berenstein)
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.245a–c АVМ of the occipital lobe. Digital AG in the arterial
(a) and the venous (b) phases. AVM is mainly supplied from the carotid area, vertebral AG (c): the posterior cerebral arteries also par-
259
ticipate in AVM blood supply. The occipital branch of the external carotid artery is the additional source of blood supply. The outflow proceeds into the superior sagittal sinus
Fig. 3.246a–f Variants of AVM location: posterior frontoparietal region (a), frontobasilar region (b), temporal (c), occipital (d) and intra-
ventricular locations (e,f)
260
AVM are supplied mainly from perforating arteries and outflow proceeds via deep cerebral veins (Figs. 3.247, 3.248). The AVM of choroid plexus forms a separate group; they are supplied mainly via choroid arteries, have an extracerebral origin and surgical access to these arteries is relatively easy (Fig. 3.249). In some cases, the combination of congenital weakness of the vascular wall with the marked changes of haemodynamics in supplying and outflow AVM vessels and the general rearrangement of brain circulation system can lead to development of other accompanying vascular affections such as arterial aneurysms and varix dilatation within the AVM. Such aneurysms are called hydrodynamic aneurysms. They can be
Chapter 3
located close to AVM and at a distance, sometimes in the supplying and even distant arterial vessel (Figs. 3.250–3.252). Usually, the AVM node is drained by one big or several smaller veins, which can be easily identified. The main sign of arteriovenous shunt is the early filling of veins during the arterial phase of angiography examination (Fig. 3.253). Although arteriovenous shunting is a characteristic attribute for AVM, it can be observed in some other clinical situations, for example, during first 2 weeks after ischaemic stroke (luxury perfusion syndrome) or in patients with certain types of brain tumours (glioblastoma, metastasis, haemngiopericytoma, etc.). The veins that drain the AVM are thickened, ec-
Fig. 3.247a–c Intraventricular АVМ. Coronal and lateral AG (a,b) of the carotid area show a tangle of AVM, repeating the route of
choroids plexus of the lateral ventricle and supplied from the anterior choroid artery, vertebral AG (c): AVM is filled from the posterior choroid artery
Fig. 3.248a–c Deep-seated subtentorial АVМ in the cerebellar vermis. Vertebral AG in coronal (a) and lateral (b,c) projections. AVM is supplied from the superior cerebellar artery, the outflow is proceeded via the vein of Galen and sinus rectus
Cerebrovascular Diseases and Malformations of the Brain
261
Fig. 3.249a–c Intraventricular АVМ. Digital AG of the carotid area in coronal (a) and lateral (b) projections demonstrate a small AVM supplied from the anterior choroid artery (arrow), and vertebral AG (c) demonstrates imaging of veins of the malformation in the arterial phase
Fig. 3.250a–d Schematic representation of concomitant vascular lesions in AMS: haemodynamic aneurysm (a), dysplastic aneurysm (b), direct aneurysm–venous fistula within the AVM cavity (c), arterial ectasias within the AVM cavity (d). (Illustrations according to A. Berenstein)
Fig. 3.251a–c Haemodynamic aneurysm (arrow) in the ostium of the posterior inferior cerebellar artery in a patient with AVM supplied by the same artery
262
Chapter 3 Fig. 3.252 Multiple hemodynamic aneurysm of the posterior cerebral artery (arrow) in a
patient with AVM supplied by the same artery
Fig. 3.253a–c Hemodynamic aneurysm of the basilar artery bifurcation (arrow) in a patient with large parietooccipital malformation. MRI in T2 (a), T1 (b) WI, 3D TOF MRAG (c)
tatically changed and coiled, and sometimes dilated with the formation of saccular venous cavities. Ultrasonic Doppler is only an initial screening method of examination of patients with a proposed AVM; it reveals the increase of blood flow on the side of AVM in cases of large AVM and an intense arteriovenous shunting. However, locating the AVM with the help of Doppler is a complicated task. CT and MRI are methods that are more informative in the overall AVM picture in brain structures. CT remains a method of choice in diagnostics of acute intracranial haemorrhages (within the first week). CT without contrast enhancement reveals the area of increased density in case of an acute intracerebral haemorrhage (Fig. 3.254). The calcifications
located within the AVM structure can have high CT density (Fig. 3.255). Furthermore, CT is capable of delineating subarachnoid clots or blood after the rupture of superficially located AVM. Within 2 weeks after a haemorrhage, the density of blood decreases (Fig. 3.256), and the peripheral zone of increased density can appear after intravenous contrast administration, thus complicating the differential diagnosis between haemorrhage and other intracerebral mass lesions. In non-complicated cases, the AVM after contrast medium administration is defined as an area of increased density with the uneven contours; the hypertrophied vessels are coiled, and they have the sharply thickened form here and there.
Cerebrovascular Diseases and Malformations of the Brain
263 Fig. 3.254a,b Temporal lobe AVM. АG in lateral projection in the late arterial phase (a): filling of veins providing outflow from AVM. Another patient (b): occipital lobe AVM, early filling of veins in the arterial phase of vertebral AG
Fig. 3.255a–d AVM within corpus callosum with haemorrhage into medial regions of the right frontal region. CТ (a), AG (b) in lateral projection. Observation of another patient with AVM supplied by the posterior cerebral artery with haemorrhage into the parietal lobe (c,d)
264
Chapter 3
Fig. 3.256a–c AVM of the right temporal lobe. CТ images without contrast enhancement demonstrate calcified walls of AVM cavity
Fig. 3.257a–c AVM of the anterior and posterior choroid arteries. CT scan at the end of the first week after haemorrhage into the lateral
ventricle triangle shows a “withering” haemorrhage (a). DSA of the carotid and posterior circulation area (b,c)
Fig. 3.258a–c AVM of the left temporal region. A series (a) of CT: there is a heterogeneously hypodense area in the left temporal region. Contrast enhancement (b) helps to demonstrate vessels of AVM in the temporo-occipital region. c DSA in lateral projection
Cerebrovascular Diseases and Malformations of the Brain
265
The dilated veins can be revealed in the subarachnoid space (Figs. 3.257–3.259). Currently, CT angiography is rarely used in AVM diagnostics, and its potential in visualisation of AVM angio-architecture is not yet defined. This method has some advantages over a standard CE CT. CT angiography with subsequent 3D processing provides much more information about AVM blood supply and outflow; it also identifies the accompanied brain vessel pathology (Figs. 3.260, 3.261). Among all diagnostic methods of the brain vascular system examination (with the exception of cerebral angiography), the most informative is MR tomography and its modifications, based on the use of special angiography software. In standard MRI (T1- and T2-weighted imaging), an AVM looks like a compact area of heterogeneous signal changes, caused by the
numerous variegated and coiled vessels with typical effect of signal loss from fast blood flow (Figs. 3.262, 3.263). The sites of increased MR signal can be areas of partial thrombosis of malformed vessels or such decreased signal can be caused by the vessels with slow blood flow (for instance, dilated veins). MRI can simultaneously demonstrate not only the AVM vessels but also can evaluate changes in surrounding brain tissues, to identify the areas of ischaemia and/or atrophy, and haemorrhages (Figs. 3.264–3.266). In the latter case, depending on a stage of clot formation, MRI can demonstrate the areas of changed signal on T1- and T2-weighted imaging. Haemosiderin deposits are the signs of old haemorrhages. The perifocal oedema and then atrophic changes and gliosis in the neighbouring brain tissue are consequences of the steal phenomenon. These changes can be better revealed with
Fig. 3.259a–c АVМ of the right frontotemporal region. CТ image with contrast enhancement reveals a conglomerate of pathologically dilated vessels with small calcifications and consequences of haem-
orrhage in the frontal lobe (a), cerebral AG in coronal and lateral projections defines blood supply of the aneurysm from the frontopolar branches of the ACA (b,c)
Fig. 3.260a–c Extensive AVM in the right cerebral hemisphere. CТ images with contrast enhancement reveal multiple pathologically dilated vessels in the right occipitoparietal region. Hypertrophy of the
right posterior cerebral artery suggests its participation in the AVM blood supply
266
Chapter 3
Cerebrovascular Diseases and Malformations of the Brain
9 Fig. 3.261a–l AVM of the left parietal region. CT without (a–c) and with contrast enhancement (d–f). There is a tangle of pathologically dilated vessels with marked contrast enhancement. MIP reformations (g–i) of CTA data reveal pathologically dilated and coiled
267
vessels of АVМ supplied from the terminal branches of the middle cerebral artery, and 3D reconstructions (j–l) give additional information about peculiarities of venous outflow from AVM via convex veins
Fig. 3.262a–c Midbrain AVM. Т2-weighted imaging (a) and Т1-weighted imaging (b) show AVM vessels with typical flow–void phenomenon, 3D TOF MRA (c) demonstrates hypertrophy of the left posterior cerebral artery, AVM tangle and a draining vein flowing into the vein of Galen
Fig. 3.263a–c AVM of the occipital lobe. Т2-weighted imaging (a) and Т1-weighted imaging (b,c) demonstrate hypertrophy of posterior
cerebral artery and a tangle of pathologically dilated vessels of the AVM, hypointense in all sequences
268
Fig. 3.264a–f Haemorrhages in patients with AVM. Case 1. АVМ of
the right frontal region. Т2-weighted imaging (a) and Т1-weighted imaging (b) in the right frontal lobe reveal subacute intracerebral haemorrhage: there are pathologically dilated vessels of AVM near its medial border. c MRA: dislocation of the ACA to the left, additional vessel shadows are seen near haemorrhage. Case 2. Intracere-
Chapter 3
bral haemorrhage in the right parieto-occipital region. Т1-weighted imaging (d) and Т2-weighted imaging (e): hyperintense signal of the haemorrhage with dark rim on periphery in Т2 sequence. f Vertebral AG: a tangle of pathological vessels is filled from the posterior choroid artery
Fig. 3.265a–c Rupture of AVM of the right frontal lobe leads to a large intracerebral haemorrhage. Т2-weighted imaging (a), Т1-weighted imaging (b) and CT (c) demonstrate acute haemorrhage in the right frontal lobe with perifocal oedema
Cerebrovascular Diseases and Malformations of the Brain
269
Fig. 3.266a–c AVM of thalamus with ischaemia of the posterior parietal region. Т2-weighted imaging images (a,b) demonstrate a tangle of pathological vessels predominantly located in the thalamus with
the outflow proceeded into the vein of Galen. The lateral ventricles are dilated. 3D TOF MRA shows only the afferent vessels and the AVM tangle (c). Draining veins are not detected in this regimen
the help of T2-weighted imaging, in which they are visible as areas of increased MR signal. The use of DWI can give additional help to identify the nature of MR signal changes around the AVM, by differentiating ischaemic changes from perifocal oedema (Cronquist et al. 2006). In general, MRI provides the unique opportunity to identify the spatial location of the main AVM glomus and functionally important areas of cortex. Here functional MRI plays an important role. With its help, it is possible to assess the interaction between motor cortex and AVM located in the projection of the frontoparietal lobe (Fig. 3.267). Usually the AVM image according to the standard MRI data is relatively typical; however, in some cases for small
AVM, especially complicated by the haemorrhage, the differential diagnosis is not an easy task. A cavernous angioma on T2-weighted imaging may have the same appearance as a small AVM (Figs. 3.268, 3.269). The use of MRA software opens up broader opportunities in visualisation of the functioning AVM. Such software consists of numerous sequences; each of them has its own advantages. Both TOF and 3D PC sequences are used in diagnostics of patients with AVM. Like cerebral angiography, the use of presaturation volumes can identify the direction of blood flow in the AVM vessels. The 3D TOF, 3D TOF with MTS and 3D PC sequences are used to achieve the better imaging of the afferent vessels,
Fig. 3.267a–c Functional MRI in patient with a small parasagittal
shows a pathological tangle of vessels and clearly detects a drainage vein flowing into the superior sagittal sinus, 3D reconstruction of cerebral cortex and convex veins (c)
AVM of the right posterior frontal region MRI in Т1-weighted imaging (a) with imaging of motor area (white arrow), a site where AVM is located (black arrow). Venography (b) with contrast enhancement
270
Chapter 3
Fig. 3.268a–c Micro-AVM of the posterior frontal region. Т2-weighted imaging (a,b) demonstrates a haemosiderin deposit (a sign of old
haemorrhage) and pathologically dilated convex vein adjacent to this area. On 3D TOF MRA (c) there is a small hypertrophy of the one of branches of the middle cerebral artery on the affected side
Fig. 3.269a,b Micro-AVM within central gyri rightwards with haemorrhage. Т2-weighted imaging (a) shows a hypointense area, encircled by oedema. MIP reconstruction of MRA (with contrast enhancement) clearly shows that micro-AVM (b) is supplied with blood by a branch of pericallosal artery (arrow)
while 2D TOF and 3D with MTS with presaturation of arterial blood reveals the draining veins (Figs. 3.270–3.272). In our opinion, MRA with 3D TOF MTS sequence with presaturation of the arterial blood is a highly informative method in the assessment of the venous from AVM (Figs. 3.273, 3.274). Due to the limitation of the signal–noise ratio, PC MRA cannot always obtain a high-quality image of the arterial supply and venous drainage of the AVM; nevertheless, it can be useful in distinguishing between the stationary tissues (for example, AVM calcifications) and moving blood. Such distinguishing is difficult with the use of standard T1 and T2 scanning modes, in which they have almost identical hypointense signal. In rare cases, local dilation of AVM veins can have characteristics similar to those of arterial aneurysm in CT and standard MRI. In these cases, the use of presaturation with sup-
pression of the image of arterial or venous blood can establish the origin of a venous formation.
3.16.2 Malformations of Vena Cerebri Magna— Vein of Galen Malformations This pathology is a relatively small group of congenital defects of medially located intracranial vessels with the formation of a link between arteries (usually the thalamoperforating, the choroid and the anterior cerebral artery) and the vein of Galen or other primitive medially located veins (Osborn 1999; Barkovich 2000). There may be direct fistulas or a combination of small anastomosis and direct fistulas. The causes for malformations of the vein of Galen are still unclear. Some researchers assume the high interrelation with a venous cerebral pathology
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.270a–i Case 1. AVM of the left occipital lobe. Т2-weighted imaging (a) shows a pathological net of vessels of AVM, and 3D TOF MRA (b,c) shows the hypertrophied posterior cerebral artery. Case 2. АVM of the right frontal lobe. Т2-weighted imaging (d), 2D TOF MRA (e) and 3D TOF MRA (f): the AVM blood supply proceeds from branches of the anterior and the middle cerebral artery. Case 3.
271
AVM of the right parietal lobe: Т2-weighted imaging (g), Т1-weighted imaging (h) and 3D TOF (i) MRA (MIP reconstruction) demonstrate prominent hypertrophy of branches of the anterior and the middle cerebral artery, supplying aneurysm with blood, and venous collectors draining blood from the malformation
272
Fig. 3.271a–f Case 1. AVM of the occipital lobe. Т2-weighted imaging (a): there is a conglomerate of pathological hypertrophied vessels and dilated drainage branches. MRA 3D TOF (b) and 2D TOF (c) detect the hypertrophied left posterior cerebral artery. Venous drainage proceeds into sinus rectus and sigmoid sinus. Case 2. AVM of the
Chapter 3
left basal ganglia. Т2-weighted imaging (d), 3D TOF (e) and 2D TOF (f) demonstrate a large malformation of thalamus with abundant blood supply from the anterior choroid arteries. 2D TOF АG poorly demonstrates veins that drain the AVM
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.272a–f АVМ of the right frontal lobe. Т2-weighted imaging (a) and Т1-weighted imaging (b) demonstrate a compact tangle of pathologically dilated vessels. 3D TOF MRA demonstrates hypertrophy of the temporofrontal branch of the left middle cerebral artery
273
(c,d). MIP reformation, 3D reconstruction (volume-rendering software): view from below (e) and forward view (f) additionally contribute to resolution of spatial relationship of cerebral vessels and the AVM tangle
274
Fig. 3.273a–i AVM of the right frontotemporal region. a CT: there is an area of heterogeneous density without regular borders in the right frontotemporal region, and the right lateral ventricle is more narrow than the left. Т2-weighted imaging (b,c) and Т1-weighted imaging (d): there is an accumulation of different-calibre vessels in the frontotemporal region, and a small CSF cavity near its posterior border; 3D TOF MRA (e,f): vascular net of the AVM in the right frontotem-
Chapter 3
poral region: branches of the middle cerebral artery are hypertrophied as well as one of the lenticulostriatal arteries. 2D TOF MRA venography (g,h) shows venous drainage (into the superior sagittal, the right transversal sinuses and superficial cerebral veins), and 3D TOF MRA weighted image-contrast enhancement (i) demonstrates routes of inflow and outflow of blood to the AVM
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.274a–f AVM of the left temporal region. Т2-weighted imaging (a) and Т1-weighted imaging (b): there is a tangle of pathological vessels in the temporal lobe pole. 3D TOF MRA (c,d) reveals a hypertrophy of the temporal branch of the middle cerebral artery
275
supplying AVM, and the venous outflow from AVM is poorly demonstrated. 3D TOF MRA with contrast enhancement demonstrates blood supply and drainage of the AVM (e,f)
276
Chapter 3
(absence of a direct sinus, persisting sinuses of skull base) or prenatal sinus thrombosis with the subsequent recanalisation (Lasjaunias et al. 1996). Raybaud et al. (1989) demonstrated that dilated venous structure is not the vein of Galen, but is an embryonic medially located prosencephalic vein. They believe that preservation of such primitive veins can be the starting mechanism of a direct sinus obstruction. In addition, the combination of the vein of Galen malformation with cardiovascular anomalies, for example, with coarctation of aorta and defects in interventricular septum and interatrial septum, are observed. There are several classifications of vein of Galen malformations (Yasargil 1987; Berenstein et al. 1992). The second one is by far the most popular. According to this classification, all malformations are subdivided into two main groups: (1) true malformations of the vein of Galen; (2) the dilation of the
Galen vein that happens in the case of intense blood drainage to the vein of Galen from parenchymal AVM. In turn, true malformations are additionally divided into choroid and mural types. AVM of the first type are supplied through the dilated choroid, pericallosal and thalamoperforating arteries. This type is the most widespread (Fig. 3.275, 3.276). As a rule, in children with malformation of this type, signs of cardiac insufficiency are revealed. The frequency of mural-type malformation is much less (about 10%); such AVM are supplied from posterior choroid artery (Figs. 3.277, 3.278). The number of pathological shunts is less than in the AVM of choroid type, but their diameter is much larger. The development delay, hydrocephalus and epileptic seizures are typical for the patients with mural malformation type; however, cardiac failure is a rare phenomenon. The incidence of marked dilation of the vein of Galen in cases of the huge parenchy-
Fig. 3.275a–f Vein of Galen malformation. Cerebral AG of carotid artery territories leftwards (a,b), rightwards (c) and of posterior circulation area (d,e) shows a large malformation of the vein of Galen, supplied with blood from the terminal branches of pericallosal and
dilated choroid arteries. The venous drainage proceeds via a rudimentary venous outlet towards the superior sagittal sinus. A series of CT additionally shows hydrocephalic dilatation of the lateral ventricles and small calcifications in the periventricular area (f)
Cerebrovascular Diseases and Malformations of the Brain
mal AVM with drainage into this vein is even less frequent (Fig. 3.279). Clinically, the vein of Galen malformation may manifest in one of the three following types: • Newborns with severe heart diseases, stagnation and loud intracranial noise • Children with a hydrocephalus and/or epilepsy • Older children (children of 5 years and upward, adolescents) or young adults with haemorrhages Patients with the first type have the choroid malformation type, while the mural type is more often diagnosed in patients with the second and third types. Diagnosis of the vein of Galen malformation should be conducted as soon as possible after the birth, because the effectiveness of the treatment greatly depends on an early diagnosis. With improvement of quality and greater availability of ultrasonic examination, the majority of great vein malformations are revealed in the prenatal stage. Ultrasonic examination identifies a hypoechogenic formation with the high– blood flow parameters according to Doppler examination close to median axis. X-ray craniography data in cases of the vein of Galen aneurysms is not specific, and such malformations are mainly represented by the signs of progressive hydrocephalus. In rare cases the ring-shaped or half-ring-shaped calcifications can be observed in pineal gland area (Fig. 3.280). CT reveals the typical picture: circular or oval formation of the increased density is located above and behind the third ventricle, and from these ventricles, the dilated sinus rectus stretches like a wide dense band, and then it proceeds to the increased transverse sinus. The contours of this formation are clear-cut and polycyclic (Fig. 3.281). As a rule, the third and lateral ventricles are prominently dilated due to compression of the aqueduct of cerebrum. The calcifications in the aneurysm wall and in the brain tissue can be observed (Fig. 3.282). Intravenous contrast enhancement greatly increases the density of the pathological formations because of the fast entrance of contrast medium into dilated vessels (Fig. 3.283). Aneurysms can be partially affected by the thrombosis, and in these cases, the thrombi density does not change after contrast administration. MRI together with MR angiography, if performed with high-resolution MR equipment, as a whole, is equal with cerebral angiography in revealing the dilation of the vein of Galen, and in detection of the malformation type. However, the differentiation of the blood supply sources for the malformation based on MRI is complicated. T1- and T2-weighted imaging in cases of functioning malformations reveal severe hypertrophy of the vein of Galen, with the typical effects of signal loss from flowing blood and a pulsing artefact in the phase-encoding direction, sometimes so intense that it overshadows the MR signal from surrounding brain tissue (Fig. 3.284). MRA with use of 3D TOF, 3D TOF MTS and 3D PC sequences can identify the afferent vessels of the malformation,
277
while 2D TOF and 3D TOF with MTS sequences with arterial presaturation are more effective in imaging venous outflow (Figs. 3.285–3.287). The use of sequences with a matrix of 512 × 512 improves the quality of the image of small arterial vessels. In the case of a malformation affected by thrombosis, standard MRI on T1- and T2-weighted imaging reveals a round area of heterogeneous increase of the MR signal in the posterior zone of the third ventricle depending on the amount of time since the thrombosis. PC MRA confirms the absence of blood flow in this area (Fig. 3.288–3.290). Nevertheless, despite wide non-invasive opportunities of modern CT and MR scanners, only selective angiography can provide the full information about the afferent and efferent vessels and the haemodynamic changes in the vascular system. Quite often, angiograms reveal the retrograde filling of the dilated terminal and subependymal veins. The direct sinus and posterior part of the upper sagittal sinus, basal vein and sinus drainage are dilated.
3.16.3 Dural Arteriovenous Fistulas According to modern terminology, dural arteriovenous fistulas (DAVF) are pathological arteriovenous anastomoses with multiple arteries flowing into a single venous structure. More often, they are supplied by the dural arteries, and less frequently by the vessels of the pia matter. Usually DAVF are located in the walls of dural sinuses, and they can involve neighbouring cortical veins. Some authors consider such anastomoses as arteriovenous malformations. However, the term malformation addresses primarily the congenital character of the lesion. The majority of the facts confirm that this pathology is an acquired one. Therefore, the term fistula is preferable. Unlike intracerebral AVM, DAVF usually do not form a compact tangle, and they consist of hypertrophied dural arteries and the dilated veins. Based on the aetiology, they are divided into traumatic and spontaneous dural arteriovenous fistulas; the latter, in turn, are divided into congenital and acquired. Moreover, there is a subdivision of fistulas depending on locations of the most affected dural sinus and type of shunting, fistulas with fast or slow blood flow. There is an additional classification of dural arteriovenous fistulas based on the characteristics of venous outflow (Cognard et al. 1995; Borden 1995). The share of dural arteriovenous fistulas is about 10–15% of all intracranial arteriovenous malformations. Their incidence is lower among the supratentorial ones (6%) and higher among subtentorial AVM (35%) (Casasco and Biondi 1998). Dural fistulas are of acquired pathology. Their aetiology remains controversial. One of the assumptions is previous sinus thrombosis with subsequent formation of numerous shunts with the links between arteries and a sinus—DAVF. According to other data, the crucial aspect in the formation of an arteriovenous fistula is the presence of dural venous hypertension.
278
Chapter 3
Cerebrovascular Diseases and Malformations of the Brain
9 Fig. 3.276a–l Choroid type of the vein of Galen malformation. MRA of carotid (a,b) and posterior circulation territories demonstrate a large malformation of the vein of Galen, supplied from the anterior choroid and thalamoperforating arteries; the drainage proceeds into the superior sagittal sinus. CT images (d–f) demonstrate a marked hypertrophy of the anterior choroid arteries, dilation of the vein of Galen, dilation of the lateral ventricles and multiple calcifica-
279
tions in the periventricular regions and basal ganglia. Т2-weighted imaging (g,h) and Т1-weighted imaging (i,j) also demonstrate a large number of pathologically dilated vessels on the brain base with dilation of the vein of Galen. 3D TOF MRA (k,l) detects a marked hypertrophy of the choroid and thalamoperforating arteries. Only initial segments of the dilated vein of Galen are visualised
280
Chapter 3
Cerebrovascular Diseases and Malformations of the Brain
9 Fig. 3.277a–i Mural type of the vein of Galen malformation. Cerebral AG of the carotid and the posterior circulation territories (a–h) reveals the small dilated vein of Galen with hypertrophy of the posterior choroid arteries, supplying the malformation. Т1-weighted imaging (i) and Т2-weighted imaging (j,k) demonstrate local dilation
281
of the vein of Galen with pathological drainage by an outlet into the superior sagittal sinus. 3D TOF MRA (l,m) and 3D PC (n) reveal hypertrophy of the posterior choroid arteries, supplying the vein of Galen malformation, better visualised by the phase-contrast technique
Fig. 3.278a–c Mural type of the vein of Galen malformation. Т2-weighted imaging (a) and Т1-weighted imaging (b) reveal a giant dilation in the vein of Galen. MRA in sagittal projection (c) demonstrates the markedly dilated posterior choroid arteries, supplying the aneurysm
282
Chapter 3
Fig. 3.279a–c AV malformation of the left thalamus. Т1-weighted imaging (a,b) and 3D TOF АG (c) demonstrate a large AVM of thalamus
with drainage into the dilated vein of Galen in a 50-year-old patient
Fig. 3.280a–c Malformation of the vein of Galen. X-ray craniogram
(a) in lateral projection: prominent fingerprints in the cranial vault bones, two nutshell-like calcifications near the vein of Galen, AG (b) of the left carotid artery area: the ACA weakly accumulating contrast medium is turned in a way that it resembles a wide bow, and terminal branches of the anterior and the middle cerebral artery are elongated and rectified, typical for hydrocephalus. Branches of the
posterior cerebral artery are filled via the markedly dilated posterior communicating artery with hypertrophied thalamoperforating arteries supplying the aneurysm, confluens sinuum is dilated and the left vertebral artery AG–dilated thalamoperforating arteries supply the malformation, the external walls of which are outlined by calcifications (c)
Cerebrovascular Diseases and Malformations of the Brain
283
Fig. 3.281a–c Variants of the vein of Galen malformation by CT in three different patients
Fig. 3.282a–d An observation of the vein of Galen malformation in children aged 2 (a,b) and 3 years (c,d). CT in axial projection (d) with contrast enhancement. There are many calcifications within basal ganglia and cerebral subcortical white matter as well as in the dilated the of Galen walls
284
Chapter 3
Fig. 3.283a–f Vein of Galen malformation. CT without (a–c) and with contrast enhancement (d–f) reveal pathological dilation of the vein of Galen with prominent contrast accumulation, small calcified areas and marked dilation of the lateral ventricles
Fig. 3.284a–c Vein of Galen malformation. Т2-weighted imaging (a), Т1-weighted imaging (b) and MRA 3D TOF (c) demonstrate pathologi-
cal dilation of the vein of Galen. There is a marked artefact from pulsatile movements of the aneurysm walls in the phase-encoding direction
Cerebrovascular Diseases and Malformations of the Brain
285
Fig.3.285a–f Vein of Galen malformation. Choroid type in two patients (a–c) and (d–f). 3D TOF MRA (b) and 3D PC (c) demonstrate malformation with pathological dilation of the vein of Galen. 3D TOF MRA (e) and 2D TOF (f) show the main inflows and drainage of the vein of Galen malformation
286
Fig. 3.286a–f Vein of Galen malformation. Т2-weighted imaging (a,b) and Т1-weighted imaging (c) demonstrate pathological dilation of the vein of Galen with abnormal drainage in sinus rectus and in
Chapter 3
the superior sagittal sinus (via the additionally formed venous outlet in the latter case). 3D TOF MRA (d,e) and 2D TOF (f) show afferent and efferent vessels
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.287a–f Vein of Galen malformation, the choroid type. MRI using Т2-weighted imaging (a) and Т1-weighted imaging (b): there is a large number of pathologically dilated vessels of brain base and the dilated vein of Galen. 3D TOF (c), 2D TOF (d) and 3D PC (e,f) main
287
afferent and efferent vessels of the malformation are visualised. 3D PC technique turned out to be the most informative in the complex assessment of the malformation
288
Fig. 3.288a–f Vein of Galen malformation. Т2-weighted imaging (a) and CT with contrast enhancement (b–d) reveal marked dilation of the vein of Galen with homogeneous accumulation of contrast me-
Chapter 3
dium. Т2-weighted imaging (e) and Т1-weighted imaging (f) a week after endovascular occlusion of the dilated vein of Galen lumen, but the enlargement of lateral ventricles persists
Fig. 3.289a–c Vein of Galen malformation. Т1-weighted imaging (a), Т2-weighted imaging (b) and 3D TOF MRA (c) detect the complete thrombosis of the aneurysmal sack of the AVM, visualised on MRA due to methaemoglobin
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.290a–f Complete thrombosis of the vein of Galen malforma-
tion. On MRI in three projections in Т2-weighted imaging (a) and Т1-weighted imaging (b,c) in the posterior portion of the third ventricle and medial regions of the right cerebellar hemisphere, there is a round mass with clearly delineated borders separated by brain tissue. On Т1-weighted imaging the signal is homogenously increased,
289
on Т2 it is decreased on the periphery and increased in the central part of a mass. 3D TOF MRA (d) and 2D TOF (e) reveal hyperintense signal of malformation due to shortened Т1; the signal from a mass on 3D PC AG is not differentiated due to absence of blood flow within the malformation (f)
290
Chapter 3
Fig. 3.291a–f DAVF of superior sagittal sinus’s region. Selective AG of the right carotid artery in lateral (a) and coronal (b, c) projections reveals that the fistula is filled from branches of the external carotid artery (the occipital and superficial temporal branches). The
outflow proceeds into the superior sagittal sinus and convex veins of the left hemisphere. Branches of the left external carotid artery also partake in the blood supply of the DAVF (d–f)
DAVF are described in patients after the rupture of an arterial aneurysm of the base of brain, in patients with various angiodysplasia, for example, with fibromuscular dysplasia or Ehlers-Danlos disease. The most frequent locations for the DAVF are posterior cranial fossa and skull base. Thus, the sigmoid and transverse sinuses are affected more frequently, whereas the lesion of the cavernous sinus is a relatively rare phenomenon. The incidence of other locations is extremely rare (Fig. 3.291). As a rule, the dural arteriovenous fistulas manifest when patients are in the age range of 40–60 years. The clinical manifestations depend on the AVM site.
DAVF located in transverse and sigmoid sinuses had inflammatory processes in the middle ear and other intracranial locations, and they also underwent surgical interventions close to the above-mentioned area or some distance from it. In some cases, the data point to previous skull injury, especially linear skull fracture. However, most authors note that in the majority of cases, there is not any indication of previous injuries, infections or surgical intervention. In general, it is widely believed that the main aetiology of DAVF is sinus thrombosis with subsequent occlusion and fistula formation above the level of occlusion. However, other mechanisms of fistula formation cannot be ruled out (Picard et al. 1987). In particular, the questions about fistula development with underlying venous hypertension and the subsequent autoregulation disturbance in the microshunts located in the walls of dural sinuses have been discussed (Teràda 1994). X-ray craniography, while not a standard method in DAVF diagnosis, nevertheless can reveal the increase of the arterial
3.16.3.1 DAVF of the Transverse and Sigmoid Sinuses It is suggested that the transverse and sigmoid sinuses are the most frequent site for DAVF. According to the results of the studies conducted by Halbach (1989), a group of patients with
Cerebrovascular Diseases and Malformations of the Brain
sulci of the medial meningeal artery on the side of a fistula (Fig. 3.292a). CT is a more informative method in DAVF examination; it is capable of precisely identifying the presence of accompanying changes in brain tissue in the early phase in cases of rupture of the pathologically dilated vessels (subarachnoid, subdura and intracerebral haemorrhages), bone changes, and it demonstrates the pathological vessels (Fig. 3.292). Changes in brain tissue, such as accompanying venous hypertension, oedema and thrombosis of large sinuses, however, can be better assessed with the help of MRI (Fig. 3.293). The
291
use of CT and MRI improves the revealing of the lesion site— the presence of greatly dilated extra- and intracranial vessels (Figs. 3.294–3.296). Nevertheless, the potential of these methods in identification of the blood supply sources of DAVF and the ways of blood outflow from them is rather limited, and the majority of researchers prefer direct cerebral angiography. Selective angiography remains the gold standard in the diagnostics of DAVF with the involvement of sigmoid and transverse sinuses. The fistula’s arterial supply proceeds from the transmastoidal perforating arteries (branches of occipital Fig. 3.292a–g Case 1. DAVF of occipital region (a). The lateral
X-ray craniogram demonstrates a lot of venous canals in the cranial vault bones (initial phase of carotid AG). Case 2. DAVF of the parietal region (b–g). CТ images in bone regimen demonstrate a lot of markedly dilated bone canals. CTA data confirm the presence of fistula (e–g)
292
Chapter 3
Fig. 3.293a–d DAVF of the temporal region, supplied by the meningeal media artery. Т2-weighted imaging (a–c) reveals the hyperintense area (ischaemia) in the posterior parieto-temporal region along with a pathological meningeal net of vessels. 3D TOF MRA (d) clearly shows a supplying artery and the venous drainage of fistula
Fig. 3.294a–c DAVF of the parietal region. CTA, 3D reconstruction: view from behind (a) and lateral view from inside (b,c) reveal a lot of
pathologically dilated extra- and intracranial vessels
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.295a–f DAVF of the left occipital region. Т2-weighted imaging (a,b), Т1-weighted imaging (c) demonstrate pathological meningeal net of vessels in the occipital region. 3D TOF MRA in axial (d) and
293
sagittal (e) reconstruction, as well as MRA raw data (f) reveal that the fistula is supplied with blood from branches of the vertebral and external carotid arteries
294
Chapter 3
Fig. 3.296a–i A large DAVF of the skull base and upper neck. Т2-weighted imaging (a,b), Т1-weighted imaging (c–f) and 3D TOF (g–i) dem-
onstrate a giant conglomerate of vessels on the skull base; afferent and efferent vessels are hard to identify
Cerebrovascular Diseases and Malformations of the Brain
artery), medial meningeal artery, the posterior auricular artery, branches of the ascending pharyngeal artery, meningeal and muscular branches of the vertebral artery, and from the meningopituitary trunk of the carotid artery (Padalko 1974, 1977) (Figs. 3.297–3.302). Large fistulas can be supplied from neighbouring arteries of pia matter. An important aspect of angiography diagnosis of DAVF is an examination of the cerebral venous system in general and venous outflow from the fistula in particular (Kornienko 1981). General examination of the venous system may be used to confirm or reject the assumption about the presence of sinuses thrombosis, atypical venous blood flow, etc. (Fig. 3.303). The difference in venous outflow from DAVF is a basis of some classifications. Thus, R. Djindjian (1973) described three types of a venous drainage. According to our opinion the most interesting classification is the one offered by Ch. Cognard (1995) who proposed to divide DAVFs into five main types depending on venous outflow: • Type I and type IIa—the normal venous drainage, there are some difficulties of venous outflow, the retrograde or cortical outflows are absent; • Type IIb—with the presence of antegrade (no retrograde) venous drainage without the outflow through cortical veins, the difficulty of a venous outflow is present to certain extent;
295
• Type IIa+b—the retrograde and cortical drainages are present;
• Type III and IV—only cortical drainage is present, with vein ectasias in IV type;
• Type V—perimedullary drainage is present (Fig. 304). The careful analysis of venous outflow from DAVF is a starting point in the selection of the treatment tactics (endovascular and/or surgical). In general, any arterial dural vessels can be the potential source for DAVF. The majority of them have multiple sources of blood supply. Therefore, fistulas with superior sagittal sinus involvement are usually supplied bilaterally and symmetrical from the medial meningeal artery and the perforating final branches of occipital and superficial temporal arteries. Therefore, cerebral angiography of all vascular territories is appropriate (Fig. 3.305).
3.16.3.2 Deep-Seated DAVF Shunts with the involvement of deep-seated venous system of brain—the superior and the inferior petrous sinuses— cavernous sinus belong to this group (Figs. 3.306, 3.307). The carotid–cavernous fistula is the most frequently observed pathology from this group. It is divided into two types, direct and indirect.
Fig. 3.297a,b DAVF of the occipital region. Two different cases. Lateral vertebral AG shows small DAVF supplied from meningeal branches of vertebral arteries
296
Chapter 3 Fig. 3.298a,b A large DAVF in the occipital region, supplied from the occipital branch of the external carotid artery with formation of a large venous outlet, draining into confluence sinuum. Selective AG in coronal (a) and lateral (b) projections
Fig. 3.299a–c Variants of dural fistula supplied from branches of external carotid artery. Lateral AG of three patients
Cerebrovascular Diseases and Malformations of the Brain
297 Fig. 3.300 DAVF of the occipital region. Lateral AG of the external carotid artery area shows hypertrophy of the occipital branch and the branch of medial meningeal artery supplying the fistula
Fig. 3.301a,b Large extra- and intracranial DAVF. Selective AG of the internal carotid (a) and occipital (b) arteries in lateral projections
demonstrate multiple intra- and extracranial sources supplying the fistula
298
Chapter 3
Cerebrovascular Diseases and Malformations of the Brain
9 Fig. 3.302a–l Giant DAVF with multiple sources of blood supply in the occipitoparietal region. Selective AG before embolisation of the left internal (a) and external (b) carotid arteries, the right internal (c) and external (d) carotid arteries and vertebral (e,f) artery. AG shows a giant occipital fistula supplying from almost all arterial
299
territories. On AG after embolisation of the right internal (g) and external carotid arteries (h–j), the left vertebral artery (k,l) reconstuction of blood supply of the brain itself and the fistula is seen, and the function of the latter is persisting
Fig. 3.303a,b DAVF of the occipital region in two different patients. Selective cerebral AG of the occipital artery shows a fistula with intra- and extracranial drainage. Arterial phase (a) and venous phase (b). Peculiarities of the venous outflow from DAVF of the occipital region are demonstrated (duplication of the internal jugular vein)
300
Chapter 3
Fig. 3.304 Classification of intracranial dural AVFs according to venous drainage (offered by Ch. Cognard ,1995). Description is in the text
Cerebrovascular Diseases and Malformations of the Brain
301
Fig. 3.305a–f DAVF with different sources of blood supply. Superficial temporal branches of the external carotid artery (a), the occipital artery (b), the external and the internal carotid arteries (c,d), branches of the external carotid artery (e), superficial temporal and maxillary arteries (f)
Fig. 3.306a–c The deep-seated AVF supplied from branches of the external carotid. АG in coronal (a,b) and lateral (c) projections. Involvement of deep-seated dural sinuses (superior and inferior petrous)
302
Chapter 3 Fig. 3.307 The deep-seated AVF supplied from meningeal–pituitary trunk. Lateral AG demonstrates dilated venous outlets within the temporal bone pyramid draining into sinus rectus
3.17 Carotid–Cavernous Fistulas A carotid–cavernous fistula (CCF) is an abnormal arteriovenous connection between the cavernous sinus and the carotid artery. CCF fall into two types, direct and indirect.
3.17.1 Direct CCF A direct carotid–cavernous fistula (CCF) is an arteriovenous fistula between carotid artery and cavernous sinus. Usually it develops after skull injury, accompanied by the rupture of the wall of internal carotid artery in the site where it passes through the cavernous sinus, with subsequent blood shunting to venous system of the base of brain, orbits, cortex, or develops a combined system of venous outflow. Chemosis, exophthalmos and the presence of pulsing noise above the orbit and in the temporal lobe are typical for CCF. However, in some cases CCF can be without vascular noise, the disruption of venous circulation, and out-pouching and pulsating of eyeball. Thus, the CCF proceeds without exophthalmos in cases when orbital veins do not have links with cavernous sinuses; in cases of “loose” structure of the superior orbital vein, the exophthalmic eye might not pulsate (Serbinenko 1968). It is necessary to remember that arteriosinus fistulas formed by the arteries of dura mater and cavernous sinus, carotid–internal jugular vein and a basilar–basal anastomosis can have a clinical picture similar to that of CCF. Rupture of internal carotid artery is usually a single and ipsilateral event. Bilateral CCF is a rare phenomenon; it appears in cases of severe craniocerebral injury, when the rupture of internal carotid artery happens on the one side while the blood outflow proceeds through cavernous sinuses to the other side, with the development of the bilateral exophthal-
mos. There are no reliable data in the literature about the incidence of CCF. More than 900 patients with direct CCF have been examined at the Burdenko Neurosurgical Institute for the period 1975–1999. Their share among all patients with vascular neurosurgery pathology reached 21%. Spontaneous CCF (of nontraumatic origin) constituted only 2.8% of cases. Traffic accidents are one of the frequent causes of CCF. Direct CCF can result from iatrogenic trauma, for instance, the damage of a venous sinus wall. Sometimes the rupture of saccular aneurysm of the cavernous segment of the internal carotid artery leads to the cavernous fistula formation, especially in combination with a connective tissue disease. In all cases, selective cerebral angiography of all vascular territories should be performed for diagnosis confirmation and establishing the side of CCF. On the side of fistula, angiography should be made in direct and lateral projection with an early arterial phase (the identification of fistula, its sizes and ways of venous outflow). The opposite carotid and vertebral arteries with the compression of the carotid artery at the site of fistula may be examined in direct and lateral projections accordingly in order to assess the collateral circulation; to define the state of arterial circle of cerebrum, anterior and posterior communicating arteries; and to estimate the influence of the fistula on the cerebral blood supply (Fig. 3.308, 3.309). Serbinenko (1964) described six types of CCF, depending on shunting and hemispheric arterial blood supply, from complete to partial emptying of the internal carotid artery blood flow and its overflow to cavernous sinus, with the consideration of different variants of arterial circle of cerebrum dissociation. He studied and described more than ten ways of drainage from cavernous sinus. It is necessary to perform selective angiography of the internal and all branches of the external carotid arteries on the side of fistula for the clarification of the CCF type (direct
Cerebrovascular Diseases and Malformations of the Brain
303
Fig. 3.308a–f Carotid cavernous fistula (CCF). Cerebral AG in four different patients demonstrates pathological dilation of the cavernous si-
nus and abnormal drainage of blood into the superior ophthalmic artery area. Application of additional projections in cerebral AG improves visualisation of this pathology
Fig. 3.309a–c Indirect dural CCF. Cerebral carotid (a,b) and vertebral (c) АG in the arterial phase demonstrate a pathological net within
the projection of cavernous sinus, the superior ophthalmic vein and additional venous outlets of the skull base. Examination of reflows with compression of the ipsilateral carotid artery on the neck (b,c)
304
and indirect one), and to make the differential diagnosis with other cerebrovascular diseases. In some difficult cases, it is required to perform a selective angiography of all main arterial territories. MRI on the side of fistula identifies numerous sharply dilated meningeal vessels on the base of brain. The effect of signal loss is typical for them, due to the fast turbulent blood flow in dural anastomosis. The pathological vessels have low signal in all modes. Dilation of the affected cavernous sinus is observed (Fig. 3.310, 3.311). In case of CCF, MRI also identifies enlarged veins of an orbit. MRA supplements the information about location and spread of CCF with possible separation of the venous component (Fig. 3.312). In addition, MIP reconstruction of a pathological area improves the spatial anatomic perception of malformation (Fig. 3.313). However, CCF assessment with MRI is inferior in comparison with direct carotid angiography. CT angiography is gaining ground in DAVF diagnosis, especially the wealth of information that can be obtained with the use of subsequent 2D and 3D reconstructions. This can estimate intra- as well as extracranial component of DAVF and assess the accompanying bone changes in the skull base (Fig. 3.314).
Chapter 3
3.17.2 Indirect CCF Indirect CCF (Berenstein et al. 1992; Borden 1995) or an arteriosinus anastomosis in cavernous sinus (Serbinenko 1968, 1975) is a shunt between the dural intracavernous branches of the internal carotid artery, external carotid artery, or both of them, with cavernous sinus. In rare cases, the combination of arteriosinus anastomosis in cavernous sinus anastomosis and CCF is observed. The incidence of bilateral arteriosinus anastomosis in cavernous sinus is even less frequent. Usually, this type of pathology is a spontaneous one; much less often does it result from injury. The aetiology is still not clear. The disease more frequently (4:1) affects post-menopausal women with underlying hypertension, atherosclerosis and diabetes mellitus. The other risk factors are sinus thrombosis, hormonal disorders, infection and heavy physical activity. Its clinical picture is similar to that of direct CCF; however, because of disruption of venous outflow from an orbit cavity, the ophthalmic changes are usually more intense, which leads to visual impairments and even to blindness. Among other symptoms, it is necessary to note a headache, vascular noise synchronous with the patient feeling pulsa-
Fig. 3.310a–e Rightward CCF. АG in coro-
nal and lateral projections (a,b) demonstrate an abnormal drainage of blood into the dilated cavernous sinus and superior ophthalmic vein in early arterial phase. Т2weighted imaging (c), Т1-weighted imaging (d) and 3D TOF MRA (e) confirm the presence of the rightward CCF
Cerebrovascular Diseases and Malformations of the Brain
305
Fig. 3.311a–e Bilateral CCF. Т2-weighted imaging (a), Т1-weighted imaging (b–d) and 3D TOF MRA (e) reveal bilateral dilation of cavernous sinuses and ophthalmic veins. Sphenoparietal sinus is additionally visualised rightwards
Fig. 3.312a–c Bilateral CCF. Т2-weighted imaging (a), Т1-weighted imaging (b) and MRA (c) demonstrate pathological dilation of cavernous sinuses bilaterally with dilation of the superior ophthalmic veins, more to the right, and both cavernous sinuses
306
Chapter 3
Fig. 3.313a–f Leftward CCF. 3D TOF MRA (a,b) with contrast enhancement with subsequent 3D reconstruction (c,d) reach a complete
coincidence of data with that of AG (e,f)
Cerebrovascular Diseases and Malformations of the Brain
307
Fig. 3.314a–i Bilateral CCF. Axial CTA (raw data) shows a pathological dilation of cavernous sinuses and the superior ophthalmic veins (a–c). MIP reconstruction in sagittal and coronal projections better shows dilation of venous collectors (d–f). 3D reconstruction of the acquired data–forward view and view at the angle (g–i)
tions in the head, eyelid oedema, exophthalmos, projection of the episcleral vessels of the eyeball, oculomotor and pupillary abnormalities, visual impairment and changes in the fundus, with the increase of intraocular pressure. The clinical course of the disease can be progressive, undulating and regressive. The main method of CCF diagnosis is selective cerebral angiography of the external and the internal carotid arteries, in rare cases, conducted bilaterally. It reveals the sources of blood supply and ways of outflow from cavernous sinus. The most frequent afferent vessels are meningopituitary branches of the internal carotid and ophthalmic arteries, the terminal branches of the internal maxillary, medial meningeal artery
and the ascending pharyngeal arteries (branches of the external carotid artery) (Figs. 3.315, 3.316). The outflow proceeds to the petrous sinus, the opposite cavernous and sphenoparietal sinuses, veins of dura mater, and the orbital and convex veins (Figs. 3.317, 3.318). The CT and MRI potential is substantially limited in cases of smallsized indirect fistula. The pathologically dilated cavernous sinus (possibly bilaterally) and the presence of multiple ways of blood outflow (among them, the orbital veins are the best visualised) are the MRI signs of a large fistula. The high density of the bones of the skull base complicates the CT diagnostics of the DAVF sources of supply and ways of venous outflow.
308
Chapter 3
Fig. 3.315a–f Indirect dural CCF. Selective AG of the internal (a,b) and external (c,d) carotid arteries: a small fistula is supplied from small
intracavernous branches of the internal (arrows) and partially from the external carotid artery. Observation of another patient with bilateral indirect CCF (e,f)
Fig. 3.316 Indirect dural CCF. AG in lateral projection shows a small fistula supplied from the pituitary branch of the internal carotid artery (arrows)
Cerebrovascular Diseases and Malformations of the Brain
309
Fig. 3.317 Indirect dural CCF. AG: a pathological net of vessels within the cavernous sinus of branches of the external carotid artery (arrows)
Fig. 3.318a,b Indirect dural CCF. Selective AG (a,b) of the internal and external carotid arteries. Sources of fistula blood supply are multiple
3.18 Cavernous Angioma Cavernous angioma (CA) was subclassified in 1979, according to the WHO classification of tumours, into vascular congenital disorders together with arteriovenous malformations, capillary telangiectases and DAF.
3.18.1 Pathology Histologically, CA consists of sinusoidal, irregular vascular spaces (caverns), which are connected to each other and have various shapes and sizes. All of them are filled with blood and are separated by soft tissue membranes with different thicknesses. These partitions are mutual for a few adjacent caverns (Fig. 3.19). The walls of these caverns are lined by endothelium with papillary sprouts. The characteristic feature of these walls is the presence of separated argyrophilic matrix and the absence of elastic and muscular layers. Capillaries may be present between the caverns. Cysts, calcifications, as well as sclerotic and haemorrhagic changes may also be observed, but there is no neural tissue. The genesis of these changes in most cases is characteristic for CA thrombosis. Microhaemorrhages inside as well as outside are typical for CA. The perifocal region is characterized by reactive changes of glia with staining in yellow colour due to haemosiderin deposition in
macrophages. In comparison with AVM in CA, there are no large feeding arteries and vein, which are usually related to AV shunting. These lesions may vary in size from 1 mm up to 8 cm in diameter (Konovalov 2001). A large number of lesions are asymptomatic and very often are incidentally discovered on cranial MRI performed for the evaluation of related or unrelated symptoms. When CA provokes the neurological sings, they may induce seizures (37−69%), haemorrhage (8−24%), neurological deficit (21%) and headaches (8%) (Hsu 1993; Bicknell 1978; Horowitz 1995).
3.18.2 Diagnosis Cavernous angioma can be found in any part of the CNS, including the spinal cord, but supratentorial location of CA is more often (to 80%) visualized on MRI. There are some publications in the literature with subarachnoid, intraventricular and extracerebral (epidural) locations of CA (Krief 1990).
3.18.3 Incidence Cavernous angiomas are observed in approximately 8−16% of all brain vascular malformation. Wide use of MR imaging
310
Chapter 3
Fig. 3.319a−d The microscopic structure of cavernous angioma. Cavernous angioma (a)
of a typical structure: vascular cavities are filled with erythrocytes and the walls consist of fibrous tissue (Mallory stain, magnification ×100). Marginal zone of cavernous angioma (b) on the border of hypoplastic brain tissue [hematoxylin−eosin (H&E) stain, magnification ×100]. Large calcinates in walls (c), stroma and in the cavity of cavernous angioma (b/w, H&E stain, magnification ×100). Multiple telangiectasias (d) of cerebral tissue on the periphery of the cavernous angioma (b/w, Mallory stain, magnification ×100)
Cerebrovascular Diseases and Malformations of the Brain
in neurology and neurosurgery increases the frequency of CA identification. Nevertheless, there are no published precise statistical data; thus, the incidence of CA in different publications varies from 0.4 to 4% in all populations. Typically, CA is a solitary lesion, but multiple forms are also observed in onethird of all cases. Osborn (1994) reported about 50% of multiple forms of CA, especially in familial cases (to 80%). The latter feature is essential for familial cases and was confirmed by other investigators; thus, multiple CA are very common (from 15 to 80% ) among the nearest relatives of the patient. Supratentorial CA are usually diagnosed between the ages of 20 and 40 years. Infratentorial location of CA (especially brain stem) is more common for children and juveniles.
3.18.4 Diagnosis Cerebral angiography, as a rule, does not reveal any pathological changes in intracranial vessels. Some cases with large haemorrhages and vessel dislocation may be an exclusion. Clinically silent micro-CAs on CT could be an incidental finding. In these cases, on non-enhanced CT in comparison with white matter, it looks like a spherical or prolonged lesion with equivalent, or more often, increased density on the periphery. Microcalcifications are common. There are no mass-effect and perifocal oedema. Contrast enhancement varies from none to minimal (Fig. 3.20). Large-size CA, as a rule, have calcifications in their structure that are very well identified on non-enhanced CT. In some cases the calcifications may form the majority of the lesion (Fig. 3.21). Usually, CAs with clinical presentation due to haemorrhages into surrounding brain tissue change considerably their typical CT appearances. In these cases cysts and acute haemorrhages (hyperdense foci) could be found in the structure of CA. The rupture of one of the walls may lead to formation of intracerebral
311
haematoma with growing mass-effect and perifocal oedema (Figs. 3.22, 3.23). That makes the differential diagnosis by CT more difficult, especially with primary brain tumours. The MRI features of CA are more specific; thus, in any case of CA suspicion MRI is the gold standard for diagnosis. Recently, three types of CA imaging appearances according to MR features were classified: 1. Type I the presence of haemorrhage in cavernoma cavities; the hyperintense MR signal on T1-weighted images from the whole lesion structure. On T2-weighted images CA has hypo- or hyperintense signal from the central part of the lesion with low signal from the haemosiderin rim on the periphery (Fig. 3.24). 2. Type II “popcorn-like” lesion with a well-delineated, complex reticulated core with mixed MR signal intensities due to haemorrhages in different stages of evolution and calcifications. Hypointense rim from haemosiderin has a typical appearance on T2-weighted images (Fig. 3.25). 3. Type III the reflection of old haemorrhages; cavernous angioma has iso- or hypointense MR signal on T1-weighted images and diffuse hypointense signal on T2-weighted images (Fig. 3.26). This kind of MR appearance is seen very seldom and is possibly one of the type-II variants of CA, because in the majority of cases, on the background of the described signal changes, the typical appearance for type-II variants can be visualized. A volumetric lesions with typical hypointense signal on periphery on T1- and especially on T2-weighted images are generally characteristic for cavernous angiomas on MRI (Fig. 3.27). In central parts of the lesion regions with various MR signal intensity, representing foci with haemorrhages at different stages, and regions without thrombosis, can be identified. The MRI using thin slices with high spatial resolution can detect fluid levels inside the cavernoma’s cavities (Fig. 3.28). Sub-
Fig. 3.320a−c Microcavernous angioma of the parietal region. CТ before (a,b) and after (c) contrast enhancement demonstrates a small area
of hyperdensity (arrow) with microcalcinates in the centre. There is no additional contrast enhancement
312
Chapter 3
Fig. 3.321a−c Variants of cavernous angioma with different extents of calcification on CT of different patients
Fig. 3.322a−f Giant venous angioma of the right temporal region. A series of CT demonstrates a large mass with haemorrhage areas, cysts and small calcinates; anterior horn of the right lateral ventricle is partially compressed
Cerebrovascular Diseases and Malformations of the Brain
313
Fig. 3.323a−f Cavernous angioma of the left posterior frontal region. CТ (a−c) and МRI (d−f) show a round mass with areas of acute, subacute and old haemorrhages, with marked perifocal oedema
Fig. 3.324a−c Cavernous angioma of the temporal lobe. Т2 WI (a), Т1 (b) WI and Т1 with contrast enhancement (c) demonstrate a mass
with hypo- and hyperintense areas without increment of contrast enhancement
314
Chapter 3
Fig. 3.325a−f Cavernous angiomas of the left posterior coronal (a−c), and temporal regions (d−f). On MRI there is a typical ampullary form
of a cavernous angioma. The area of haemosiderin deposit is clearly visualised Fig. 3.326a,b Multiple cerebral cavernous angiomas. Т2 (a) and Т1 (b) WI of two hypointense areas (arrows) are seen with haemosiderin deposits
Cerebrovascular Diseases and Malformations of the Brain
315
Fig. 3.327a−c Cavernous angioma of the frontal lobe. Т1 (a) and Т2 (b,c) WI demonstrate a typical hypointensity on all sequences on the periphery of the tumour
Fig. 3.328a−c Cavernous angioma of the posterior portions of the right frontal lobe. On CТ (a) there is a heterogeneously hyperdense mass with small calcifications. On sagittal Т1 (b) and axial Т2 (c) WI there is a mass with heterogeneous structure with small haemorrhages which occurred at different ages (arrow)
316
acute phase of haemorrhages is characterized by hyperintense MR signal on T1-weighted images (Fig. 3.29). Haemorrhages into surrounding brain tissue have typical features of haematoma on MRI according to the stage of evolution (Fig. 3.30). It is noteworthy that MRI is the most sensitive method of brain haemorrhage estimation and demonstrates the microhaemorrhages in cavernoma structure better than CT. The MRI can easily identify malformations in small lesions (<1 cm), especially in cases with multiple forms. T2* imaging increases the MRI sensitivity in CA detection, and the new susceptibilityweighted imaging (SWI) has also proved its high sensitivity in identification of such lesions (Figs. 3.31–3.33). Contrast enhancement following IV contrast medium administration is not a typical feature of CA. It is observed in one-third of all cases. The degree of enhancement is better estimated on superconductive MR systems than on low magnetic field devices. Usually, the degree of the lesion’s contrast enhancement is low; moreover, CA enhances just partially (Figs. 3.34, 3.35).
Chapter 3
In some complex cases with large lesions (with intrinsic haemorrhages) it is very difficult to make a correct differential diagnosis by CT, as well as by MRI, between CA and primary tumours with haemorrhagic components. The absence of perifocal oedema and Gd-enhanced tumoral fragments, the typical MR features of haematoma evolution during time, and the haemosiderin rim, are helpful in correct assessment of vascular malformation diagnosis.
3.19 Capillary Telangiectasias Capillary telangiectasias are collections of dilated capillaries separated by normal brain tissue. They usually appear as small, more multiple than solitary, lesions. The pons is the most common location, but they are found virtually in any parts of the brain and spinal cord. Most lesions are clinically silent and are discovered on plain MRI or at autopsy in middle-aged and elderly patients. Capillary telangiectasias are second to venous
Fig. 3.329a−f Cavernous angiomas of the right posterior frontal region (a−c) and thalamus (d−f). Т1 (c,e) demonstrates areas of subacute haemorrhage (hyperintensity of methaemoglobin within cavities of the cavernous angioma)
Cerebrovascular Diseases and Malformations of the Brain
317
Fig. 3.330a−c Cavernous angioma of the frontal region. Т2 (a) and Т1 (b,c) WI reveal a subacute haemorrhage (arrows) behind the cavernous angioma. Combination of hypo- and hyperintense signal is a sign of repeated haemorrhages
Fig. 3.331a,b Multiple microcavernous angiomas. Т2 (a) and Т1 (b) WI show microangiomas (arrows) with typical perifocal hypointense signal on Т2 WI
Fig. 3.332a−c Multiple cavernous angiomas of thalami (arrows). Т2 (a,b) and Т1 (c) WI
318
Chapter 3
Fig. 3.333a−f Multiple cavernous angiomas in different patients (a−f). Visualisation of small angiomas is better (arrows) on Т2* WI (b−f)
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.334a−f Cavernous angioma of the left parieto-occipital re-
gion. Т2 WI (a,b), Т1 WI (c) and Т1 with contrast enhancement (d) reveal a large cavernous angioma with minimally present focal con-
319
trast accumulation (arrow); Т2* WI (e) and DWI (f) show a markedly hypointense signal on the periphery of the angioma. Two microcavernomas are additionally revealed in the right frontal area (e)
320
Chapter 3
Fig. 3.335a−c Cavernous angioma of the left posterior frontal region. On Т2 WI (a) there a heterogeneously hyperintense central part and
a hypointense peripheral halo which are typical signs of cavernoma. Cavernoma is isointense (b) and after contrast enhancement weakly accumulates in the affected zone (c)
angiomas and are the most common vascular malformation identified at post-mortem examination (Okazaki 1989). Occasionally, capillary telangiectasias may become symptomatic and be the cause of haemorrhage, but only in association with cavernous elements (Rigamonti 1991).
3.19.1 Diagnosis Capillary telangiectasias are usually invisible on cerebral angiograms and CT. On MRI this kind of vascular malformation appears as a very small lesion with hypointense signal on all sequences (Fig. 3.36). More obvious visualization of capillary telangiectasias can be achieved by gradient-echo imaging (Fig. 3.37). Nevertheless, in most cases with capillary telangiectasias there are no clinical sings, and in some cases there may be
a haemorrhage in the brain parenchyma (more often in the brainstem according to their typical location). In these conditions the signal from haematoma may overlap the signal from capillary telangiectasias on CT or MR imaging, leading to difficulties in correct diagnosis of the cause of haemorrhage. That is why the term “occult cerebral vascular malformation” was introduced in the literature towards the end of the twentieth century (Osborn 1991).
3.20 Venous Malformations 3.20.1 Venous Angioma Venous angioma (VA) consists of radially arranged, dilated medullary or subcortical anomalous veins that drain into single, dilated venous vessel. No arteriovenous shunting is
Fig. 3.336a,b Multiple capillary telangiectasias on Т2 (a) and Т1 (b) WI. It is possible to show telangiectasias only by use of Т2 WI
Cerebrovascular Diseases and Malformations of the Brain
321
Fig. 3.337a,b Capillary telangiectasias near the middle cerebellar peduncle. Т2 (a) and Т1 (b) WI demonstrate a small hypointense mass (arrow)
present. Venous channels are separated by normal brain parenchyma. Haemorrhages are uncommon, but the risk of their development exists.
3.20.2 Aetiology The precise aetiology of venous angiomas is unknown, but in the literature there are suppositions about congenital anomalies in the development of the brain venous system. Arrested venous development after the brain arterial system has been formed could result in retention of primitive embryological medullary veins. It may lead to formation of blood drainage into a single, dilated venous structure and form venous angioma (Lasjaunias 1986).
3.20.3 Location
tiple small veins with characteristic shapes of “lion tail brush” or “Medusa head” is very well depicted during the late venous phase of angiography. In 70% of cases the drainage is into the superficial venous system, and subependymal drainage occurs in 22% of cases. Non-enhanced CT is often normal or shows an ill-defined, slightly hyperdense area. After contrast enhancement, in cases with very large VA on CT scans, the linear dilated vessel near the wall of the ventricle is identified. The CT angiography is a very sensitive method in all VA-compartment visualization. Non-enhanced MRI as well as non-enhanced CT poorly depicts venous malformation in most cases. Small veins may not be visualized at all. Large veins usually have the appearance of linear hypointense structures on T1- and T2-weighted images (Fig. 3.40). Contrast enhancement dramatically increases the sensitivity of MRI in detection of VA. Large as well as small veins are clearly seen on post-contrast studies with a
Usually, venous angiomas are located in deep cerebral and cerebellar white matter, more often adjacent to ventricular walls (Fig. 3.38). The most common location of VA is the white matter around the frontal horn of the lateral ventricle, and the second one is the cerebellum. Venous angiomas located in the cerebral hemispheres rarely cause symptoms and are most commonly incidental findings discovered on MRI, especially after contrast enhancement. In rare cases clinical signs, such as headache, focal neurological deficit and seizures, could be caused by the rupture of CA. Venous malformations located in the brainstem or cerebellum have a slightly increased incidence of haemorrhage. The VA is a typical solitary lesion, but multiple forms have been described in the “blue rubber bleb nevus” syndrome (Osborn 1994).
3.20.4 Diagnosis Cerebral angiography reveals typical VA appearances (Fig. 3.39). As a rule, in the arterial phase there is no pathology on angiograms. Dilated veins in combination with mul-
Fig. 3.338 Schematic representation of venous angioma. Multiple
enlarged medullary veins (small arrows) in the deep white matter and periventricularly are drained into a single dilated transcortical vein (large arrow)
322
Fig. 3.339a−c Venous angioma in a 7-year-old child. The right carotid AG (a,b) in the arterial phase: no pathological changes of brain vessels. A lot of concentrically converging small venous ves-
Chapter 3
sels in the posterior frontal region are revealed in the venous phase. These small veins form a single vein draining into the superior sagittal sinus (c)
Fig. 3.340a−c Venous angioma of the left frontal region. Т2 (a) and Т1 (b,c) WI reveal a typical picture of angioma with small veins (small arrows) draining into a single drainage vein (large arrow)
Fig. 3.341a−c Venous angioma of the right frontal region. Т2 (a), Т1 (b) and Т1 WI after contrast enhancement (c) show an area of contrast medium accumulation stretched from the cortex to the anterior horn of the lateral ventricle
Cerebrovascular Diseases and Malformations of the Brain
typical shape – “brush” formation (Figs. 3.41–3.43). Contrastenhanced MR angiography with subsequent post-processing may yield additional helpful information about the special relationships between VA and drainage pathways, defining well the site of drainage into a dural venous sinus, or into the subependymal area (Fig. 3.44). Around VA the remains of old haemorrhages may occasionally be found as hypodense regions on CT, corresponding to CSF signal changes on MRI (Fig. 3.45). As mentioned previously, VAs may be associated with other vascular malformations, for example, with cavernomas as well as other brain pathologies (e.g. multiple sclerosis). The diagnostic possibilities of MRI in these conditions are always preferable to those of CT (Figs. 3.46, 3.47).
3.20.5 Venous Varix Varicose dilatation of cerebral veins are seen mainly in association with several other types of vascular pathology of the brain − AVM, malformation of Galen vein and, occasionally, with VAs (Vinuela 1987).
Fig. 3.342a−c Deep-seated venous angioma of the temporal lobe (arrow). Т1 WI (a): there is no obvious pathology. MRI with contrast enhancement reveals a pathological branched vascular net in
323
Varices are dilated, thin-walled venous channels that have a tendency to lead to thrombosis and rupture with subsequent subarachnoid bleeding. Cerebral varices are located in the brain parenchyma and leptomeninges, and they can be found with pial and dural vascular malformations.
3.20.6 Diagnosis Cerebral angiography, CT and MRI demonstrate fusiform enlargement of draining veins with saccular aneurysmal dilatations. These large veins are usually located in the subarachnoid space but may lie in the brain parenchyma also. Association with congenital vascular malformation, such as AVM, is typical. On CT with contrast enhancement venous varices are well depicted as a region with strong, uniform signal of increasing density. On MR images venous varices typically appear as well-delineated ovoid areas with variable signal. Fast flow inside the varices produces low signal. For better identification of venous flow into the varices, phase-contrast and 2D TOF МRA are helpful (Figs. 3.48–3.50).
the temporal lobe (b); 3D TOF МRA with contrast enhancement (c) demonstrates a drainage vein flowing into the deep cerebral vein system (arrow)
324
Chapter 3
Fig. 3.343a−f Venous angioma of basal ganglia. Т2 WI (a), Т1 (b) WI and FLAIR (c) show a hypointense area within the lateral aspect of the head of caudate nucleus with signal change on FLAIR: contrast enhancement (d−f) reveals a venous angioma of atypical structure at this site (arrows)
Cerebrovascular Diseases and Malformations of the Brain
325
Fig. 3.344a−f Venous angioma of the right frontal region. Т2 (a), Т1 (b) and Т1 WI after contrast enhancement (c,d) show a typical ve-
nous angioma and a drainage vein (arrow). 3D TOF АG with contrast enhancement (e,f) demonstrate angioma and its drainage into a convex vein
Fig. 3.345a−c Consequences of haemorrhage from the venous angioma in the right parietal region
326
Fig. 3.346a−f A combination of cavernous and venous angiomas of
the right cerebellar hemisphere. Т2 (a) sequence demonstrates a cavernous angioma (large arrow) and a drainage vein (small arrow). Additional projections on Т1 (b,c) and T2 (d) allow to obtain additional
Chapter 3
information about the location of cavernous angioma. On 3D TOF МRA with contrast enhancement (e,f) there is a pathological net of small veins flowing into a drainage vein
Cerebrovascular Diseases and Malformations of the Brain
Fig. 3.347a−f A combination of cavernous and venous angiomas of
the parietal region. On Т2 (a) and Т1 without (b) and after (c,d) contrast enhancement the drainage vein of venous angioma is indicated
Fig. 3.348a−c Varicose dilation of veins in AVM of the frontal re-
gion. CТ before (a) and after (b) contrast enhancement demonstrate an abnormal mass with marked and heterogeneous accumulation of
327
by an arrow (d). 2D TOF MRA with contrast enhancement confirms the presence of a pathologically dilated vein draining into the superior sagittal sinus (e,f)
contrast medium. АG in the venous phase (c) demonstrates a large dilated venous cavity (arrows) on the background of AVM
328
Chapter 3
Fig. 3.349a−f Varicose dilation of veins in AVM of the temporal region. Т2 (a−c), 3D TOF (d) and 2D TOF (e,f) MRA demonstrate a large
AVM supplied from branches of the middle cerebral artery. Abnormal varicose dilation of veins is seen
Cerebrovascular Diseases and Malformations of the Brain
329
Fig. 3.350a−f DAVF of the left temporal region. Т2 (a,b) and Т1 WI with contrast enhancement (c,d) demonstrate a lot of irregularly dilated and coiled vessels in the left temporal region. On 3D CTA (e,f) there is an irregular dilation of the drainage vein – the fistula
Refere n c e s Alvarez-Linera J, Benito-Leon J et al (2003) Prospective evaluation of carotid artery stenosis: elliptic centric contrast—enhanced MRA and spiral CT angiography compared with DSA24: Radiology 248:1012–1019 Astrup J, Simon L, Siesjo B (1981) Thresholds of cerebral ischaemia: the ischaemic penumbra. Stroke 12:723–725 Atlas S et al (1997) Intracranial aneurysms: detection and characterization with MRA with use of an advanced post processing technique in a blinded-reader study. Radiology 203:807–814 Averkieva EV et al. (2003) MRI in diagnosis of chronic cerebral circulation deficiency (review of literature). J.Med.Viz. pp. 3:40-48 Balkaran B et al. (1992) Stroke in a cohort of patients with homozygous sickle cell disease. J.Pediatr. 120:360-366 Barber PA, Darby DG, Desmond PM et al (1998) Prediction of stroke outcome with echo-planar perfusion- and diffusion-weighted MRI. Neurology 51:418–426 Barker P, Gillard J, van Zijl P et al (1994) Acute stroke: evaluation with serial proton MR spectroscopic imaging. Radiology 19:723–732
Barkovich A (2000) Pediatric neuroimaging, 3rd edn. Lippincott Williams & Wilkins, Philadelphia Berenstein A, Lasjaunias P (1992) Surgical neuroangiography. In: Endovascular Treatment of cerebral lesions. Springer Verlag Berlin pp. 267-317 Berenstein A, Lasjaunias P, ter Brugge KG et al (2003) Cerebral venous occlusive disease. In: The Neuroradiology Education and Research Foundation Symposium 2003: Vascular disease—diagnosis, therapy, and controversies. American Society of Neuroradiology, Oak Brook, Ill., pp 109–113 Bicknell JM et al. (1978) Familial cavernous angiomas. Arch Neurol. 35:746-749 Binaghi S, Colleoni M, Maeder P et al (2007) CT Angiography and perfusion ct in cerebral vasospasm after subarachnoid haemorrhage. AJNR Am J Neuroradiol 28:750–758 Borden J, Wu J, Shucart W (1995) A proposed classification for spinal and cranial dural arteriovenous fistulous malformations and implications for treatment. J. Neurosurgery 82:167-179
330 Borisch I et al (2003) Preoperative evaluation of carotid artery stenosis: comparison of contrast-enhanced MRA and duplex sonography with digital subtraction angiography. AJNR Am J Neuroradiol 24:1117–1122 Bosmans H et al (1995) Characterization of intracranial aneurysms with MRA. Neuroradiology 37:262–266 Brunereau L et al. (2000) De novo lesions in familial form of cerebral cavernous malformations: clinical and MR features in 29 non-Hispanic families. Surg Neurol. May 53(5):475-82 (discussion 482-483) Buklina SB (2001) The unilateral space neglect in patients with arteriovenous malformations of the deep brain structures. Zh Nevrol Psikhiatr Im S S Korsakova. 101(9):10-5 (in russian) Calliada F et al. (1999) Selection of patients for carotid endarterectomy: the role of ultrasound. J.Assist.Comp.Tomogr. 23(Suppl.):75-81 Casasco A, Biondi A (1998) Angiographic aspects and management of dural arteriovenous fistulas. Crit.Rev.Neurosurg. 8:103-111 Chaloupka J, Huddle D. (1998) Classification of vascular malformations of the CNS. Neuroimaging Clin N Am 8:295–321 Cognard C, Gobin Y, Pierot L et al (1995) Cerebral dural arteriovenous fistulas: clinical and angiographic correlation with a revisited classification of venous drainage. Radiology 194:671–680 Cronqvist M, Wirestam R, Ramgren B et al (2006) Endovascular treatment of intracerebral arteriovenous malformations: procedural safety, complications, and results evaluated by MR imaging, including diffusion and perfusion imaging. AJNR Am J Neuroradiol 27:162–176 Dandy W (1944) Intracranial arterial aneurysms. Ithaca N.Y. Camstock, p. 278 Djindjian R et al. (1973) Internal carotid-cavernous sinus, arteriovenous fistulae: current radio-anatomic aspects and therapeutic perspectives. Neurochirurgie. Jan-Feb 19(1):75-90 Ernemann U et al (2000) 3D angiography in treatment planning of cerebral aneurysms. In: [Syllabus.] Cerebral aneurysms: 10th advanced course of the ESNR. European Society of Neuroradiology, Oslo, Norway, pp 25–30 Ferguson et al (1999) The North American Symptomatic Carotid Endarterectomy Trial: surgical results in 1,415 patients. Stroke 30:1751–1758 Filatov JM (1973) Angiographic control during surgery and in the postoperative period in cerebral arteriovenous aneurysms. Vopr Neirokhir. Mar-Apr 37(2):13-6 (in russian) Fisher CM (1979) Capsular infarcts. Arch.Neurol. 36:65-73 Fisher CM, Curry B (1991) Lacunar infarcts – a review. Cerebrovasc. Dis. 1:311-320 Fisher M, Garcia J (1996) Evolving stroke and the ischaemic penumbra. Neurology 47:884–888 Fukui M (1997) Current state of study on moyamoya disease in Japan. Surg Neurol. Feb 47(2):138-43 (review) Furst G, Hofer M, Steinmetz H et al. (1996) Intracranial stenooclusive disease: MR angiography with magnetization transfer and variable flip angle. AJNR 17:1749-1757 Gannushkina I (1975) Physiology and pathophysiology of cerebral blood supply. In: Cerebrovascular diseases. Medicina, Moscow, Medicine, pp 66–105 (in Russian)
Chapter 3 Garcia J, Mitchem H, Briggs L et al. (1983) Transient focal ischemia in subhuman primates:neuronal injury as a function of local cerebral blood flow. J. Neuropathol. Exp.Neurol. 42:44-60 Geroulakos G et al. (1996) Ultrasonographic carotid plaque morphology in predicting stroke risk. Br.J.Surg. 83:582-587 Goddard A, Mendelow A, Birchall D (2001) Carotid stenosis in the investigation of carotid stenosis. Clin.Radiol. 56:523-534 Gomori J et al (1985) Intracranial hematomas: imaging by high-field MR. Radiology 157:87–93 Gomori J, Grossman R, Goldberg H et al.(1985) Intracranial hematomas:imaging by high-field MR. Radiology 157:87-95 Gusev EI, Skvortsova V (2001) Brain ischaemia. Medicina, Moscow (in Russian) Gusev EI et al (2003) Epidemiology of stroke in Russia. Zh Nevrol Psikhiatr Im S S Korsakova 8:4–9 Consilium Medicum, special issue, pp 5–7 (in Russian) Halbach V, Higashida R, Hieshima G et al. (1989) Transvenous embolization of dural fistulas involving the trasnverse and sigmoid sinuses. AJNR 10:385-392 Hochmuth A, Spetzger U, Schumacher M (2002) Comparison of three-dimensional rotational angiography with digital subtraction angiography in the assessment of ruptured cerebral aneurysms. AJNR Am J Neuroradiol 23: 1199–1205 Horowitz S, Zito J et al. (1991) Computed tomographic-angiographic findings within the first five hours of cerebral infarction. Stroke 22:1245-1253 Horowitz M, Kondziolka D (1995). Multiple familial cavernous malformations evaluated over three generations with MR. JNR 16:1353-1355 Hossmann K (1994) Viability thresholds and the penumbra of focal Ischemia. Ann.Neurol. 36:557-565 Hsu FPK, Rigamonti D, Huhn SI (1993) Epidemiology of cavernous malformations. In: Auad I.A.,Barrow D.L., eds. Cavernous malformations. American Association of neurological surgeons publications committee, p.13-24 Kidwell C, Saver J, Mattiello J et al (2000) Thrombolytic reversal of acute human cerebral ischaemic injury shown by diffusion/perfusion MRI. Ann Neurol 47:462–469 Konovalov A et al (2001) Haemorrhage and silent vascular malformations of the brainstem. J Med Visualis 213–18 (in Russian) Kornienko V (1981) Functional cerebral angiography. Medicine, Leningrad, p 216 (in Russian) Krief O et al. (1991) Extraaxial cavernous hemangioma with hemorrhage. AJNR Am J Neuroradiol. Sep-Oct 12(5):988-90 (review) Langer D, Lasner TM,Hurst RW et al. (1998) Hypertension, small size, and deep venous drainage are assosiated with risk of hemorrhagic presentation of cerebral AVM. Neurosurgery 42:481-489 Lasjaunias P et al. (1986) Developmental venous anomalies (DVA): the so-called venous angioma. Neurosurg.Rev. 9:233-244 Lasjaunias P, Alvarez H, Rodesch G et al (1996) Aneurysmal malformations of the vein of Galen. Interven Neuroradiol 2:15–26 Lee S, ter Brugge KG (2003) Cerebral venous thrombosis in adults: the role of imaging evaluation and management. Neuroimaging Clin N Am 13:139–152 Lefkowitz D, LaBenz M, Nudo SR et al (1999) Hyperacute ischaemic stroke missed by diffusion-weighted imaging. AJNR Am J Neuroradiol 20:1871–1875
Cerebrovascular Diseases and Malformations of the Brain Lell M, Fellner C, Baum U et al (2007) Evaluation of carotid artery stenosis with multisectional CT and MR imaging: influence of imaging modality and postprocessing. AJNR Am J Neuroradiol 28:104–110 Link J, et al. (1996) Spiral CT angiography versus DSA in detection of carotid stenoses. Zentralbl Chir. 121(12):1018–22 Lombardy M, Bartolozzi C (2004) MRI of the heart and vessels. Springer, Berlin Heidelberg New York Lysachev AG (1988) Intravascular embolization of brain AV-malformations. In book: VI congress of russian neurosurgions. M, B, pp. 123–131 (in russian) Marcus C, Ladam-Marcus V, Bigot J et al (1999) Carotid arterial stenosis: evaluation at with CT -angiography with the volumerendering technique. Radiology 211:775–780 Matsko DE (1991) Vascular malformations of brain and spinal cord. In: Pathological anatomy of the surgical diseases of CNS. Editor: Medvedev IA, St. Petersburg, pp. 104–120 (in russian) Medvedev YA, Matsko DE (1993) Aneurysms and congenital cerebral vessels desorders. Vol. I, St. Petersburg., Izd. RNSI by prof. Polenov AL, p. 136 Menkes J, Sarnat H (2000) Child neurology. 6th ed. Lippincott Williams&Wilkins, Philadelphia, p. 1280 Mies G, Ishimaru S et al. (1991) J.Cereb.Blood Flow Metab. II:753–761 Nakagawa T, Hashi K (1994) The incidence and treatment of asymptomatic, unruptured cerebral aneurysms. J. Neurosurgery 80:217–223 Newton T, Cronquist S (1969) Involvement of dural arteties in intracranial AV malformations. Radiology 93:1071–1078 Ogata J, Yutani C, Imakita M et al. (1989) Hemorrhagic infarct of the brain without a reopening of the occluded arteries in cardioembolic stroke. Stroke 20:876–883 Okazaki H (1989) Fundamentals of neuropathology: cerebrovascular disease. Fundamentals of neuropathology. Igaku Shoin Medical, pp 27–94 Orrison WW (ed) (2000) Neuroimaging, vol 1. Saunders, Philadelphia, p 943 Osborn A (1994) Diagnostic neuroradiology. Mosby, St.Louis, p. 936 Osborn A (1999) Diagnostic cerebral angiography, 2nd edn. Lippincott Williams & Wilkins, Philadelphia, p 462 Padalko PI, Serbinenko FA (1974) Clinical symptoms, diagnosis and surgical treatment of multiply arteriovenous anastomoses. In book: Neurosurgical pathology of cerebral vessels. M., pp. 334– 340 (in russian) Padalko PI, Kornienko VN (1977) Cerebral circulation in arterio-sinus anastomoses of the occipito-mastoid area. Zh Vopr Neirokhir Im N N Burdenko. Nov-Dec (6):12–7 (in russian) Picard L, Bracard S, Moret J et al (1987) Spontaneous dural arteriovenous fistulas. Semin Int Radiol 4:219–241 Podoprigora A.E, et al. (2003) H1 MR-spectroscopy in diagnosis of brain ischemia. Zh. Nevrol Psikhiatr Im S S Korsakova. 9(Suppl):162 (in russian) Pollock B, Flickinger J, Lundsford L et al. (1996) Factors that predict the bleeding risk of cerebral AVM. Stroke 27:1–6
331 Preter M et al. (1996) Long-term prognosis in cerebral venous thrombosis. Follow-up of 77 patients. Stroke. Feb 27(2):243–246 Provenzale J, Sorensen A, Yuh W (2000) Contemporary stroke imaging: early diagnosis, triage, and treatment. RSNA categorical course textbook in diagnostic radiology: neuroradiology. Radiological Society of North America, Oakbrook, Ill., pp 7–25 Raybaud CA, Strother CM, Hald JK et al. (1989) Aneurysms of the vein of Galen: embryonic considerations and anatomical features relating to the pathogenesis of the malformation. Neuroradiology 31:109–128 Regli L, Regli F, Maeder P et al. (1993) MRI with gadolinium contrast in small deep(lacunar) cerebral infarcts. Arch.Neurol. 50:175–180 Rigamonti D et al. (1991) Cavernous malformations and capillary telangiectasia: a spectrum within a single pathological entity. Neurosurg. 28:60–64 Rivera P, Willinsky R, Porter P (2003) Intracranial cavernous malformations. Neuroimaging Clin N Am 13:27–40 Roberge J (2003) 3D contrast-enhanced time-robust MR angiography of the supraaortic arteries. 13:8–10 Schumacher M (2000) Diagnostic workup in cerebral aneurysms. In: Syllabus.Cerebral aneurysms. 10th advanced course of the ESNR, Oslo pp.13–25 Schumacher M (2002) Aneurysms. In: Craniocerbral Diseases, pp. 170–175 Seeger M, Barratt B, Lawson G et al. (1995) The relationship between carotid plaque composition, morphology and neurological symptoms. J.Surg.Res. 58:330–336 Serbinenko FA (1964) Hemispheric arterial blood circulation of the brain and certain compensatory vascular reactions in carotidcavernous anastomoses. Zh Nevropatol Psikhiatr Im S S Korsakova., 64:205–11 (in russian) Serbinenko FA (1968) Carotid cavernous fistulas. In: Handbook in surgery. Neurosurgery. M., 2:651–660 Serbinenko FA (1974) Possibilities of catheterization method and cerebral vessels occlusion. In: Neurosurgical pathology of cerebral vessels. M., pp. 221–233 (in russian) Shakhnovich VА (2002) Brain ischemia. Neurosonography, M.: AST p.305 Shier D, Tanaka H, Numaguchi Y et al (1997) CT angiography in evaluation of acute stroke. AJNR Am J Neuroradiol 18:1011–1020 Shroff M, de Veber G (2003)Venous sinus thrombosis in children. Neuroimaging Clin N Am 13: 115–138 Sigal R et al. (1990) Occult cerebrovascular malformations: followup with MR imaging. Radiology. Sep 176(3):815–819 Suslina ZA, Vereshchagin NV, Piradov MA (2002) Subtypes of ischemic stroke: diagnosis and treatment. J. Consilium medicum 3(5):218–225 Suzuki J (1986) Moyamoya disease. Springer, Berlin Heidelberg New York, p 189 Suzuki J, Takaku A (1969) Cerebrovascular “moyamoya” disease. Disease showing abnormal net-like vessels in base of brain. Arch Neurol 20:288–299 Terаda T, Higashida R,Halbach V et al. (1994) Development of aquired arteriovenous fistulas in rats due to venous hypertension. J. Neurosurg. 80:884–889 Tomsick T, Brott T, Barsan W et al. (1992) Thrombus localization with emergency cerebral CT. AJNR 13:257–263
332 Ueda T, Sakaki S, Yuh W et al (1999) Outcome in acute stoke with successful intra-arterial thrombolysis and predictive value of initial single-photon emission-computed tomography. J Cereb Blood Flow Metab 19:99–108 Valavanis A (1996) The role of angiography in the evaluation of cerebral vascular malformation. Neuroimaging Clin N Am 6: 679–704 Vinuela F et al. (1987) Giant intracranial varices secondary to highflow arteriovenous fistulae. J Neurosurg. Feb 66(2):198-203 Vereshchagin NV et al. (1986) CT of the brain. M:Meditsina, p.251 Vereshchagin N et al (2002) Stroke: principles of diagnosis, treatment, and prevention. Internal Medicine, Moscow, p 208 (in Russian) Waaijer A, van der Schaaf I, Velthuis B et al (2007) Reproducibility of quantitative CT brain perfusion measurements in patients with symptomatic unilateral carotid artery stenosis. AJNR Am J Neuroradiol 28:927– 932 Wang P, Barker P, Wityk R et al. (1999) Diffusion-negative stroke: a report of two cases. AJNR 20:1876-1880 Warach S, Gaa J, Siewert B et al (1995) Acute human stroke studied by whole-brain echo planar diffusion-weighted magnetic resonance imaging. Ann Neurol 7:31–241 White P et al (2001) Intracranial aneurysms: CT angiography and MRA for detection—prospective blinded comparison in a large patients cohort. Radiology 19:39–49 Wolpert S, Caplan L (1992) Current role of cerebral angiography in the diagnosis of cerebrovascular disease. AJR 159:191-197
Chapter 3 Willinsky R et al. (1988) Brain AV malformations: Analysis of the angioarchitecture in relationship to hemorrhage. J. Neuroradiology 15:225-237 Yamamoto K, Nogaki H, Takase Y et al. (1992) Systemic lupus erythematosus associated with marked intracranial calcification. AJNR 13:1340-1342 Yamada N, Higashi N, Otsubo R et al (2007) CT Angiography and perfusion CT in cerebral vasospasm after subarachnoid haemorrhage, AJNR Am J Neuroradiol 28:750–758 Yasargil M (1984) Microneurosurgery. Georg Thieme Verlag, Stuttgart Yasargil М (1987) Microneurosurgery, AVM of the brain: history, embryology, pathologic conditions, hemodynamics, diagnostic studies, microsurgical anatomy. Vol. 3A. Thieme, New York Yasargil М (ed) (1987) Microneurosurgery—AVM of the brain: history, embryology, pathological conditions, considerations, haemodynamics, diagnostic studies, and microsurgical anatomy, vol 3. Thieme, Stuttgart Yoon DY, Lim KJ, Choi CS et al (2007) Detection and characterization of intracranial aneurysms with 16-channel multi-detectorrow CT angiography: a prospective comparison of volume-rendered images and digital subtraction angiography. AJNR Am J Neuroradiol 28:60–67 Zlotnik EI (1967) Cerebral vessels aneurysms. Minsk, Izd. Belarus, p.196
Chapter 4
4
Supratentorial Tumours
4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10
Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Supratentorial Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Neuroepithelial Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Neuronal and Mixed Neuronal–Glial Tumours . . . . . . . . . . . . . . Embryonic Neuroepithelial Tumours .. . . . . . . . . . . . . . . . . . . . . . . Primary Lymphoma of the CNS .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Metastatic Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Supratentorial Cysts .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eosinophilic Granuloma .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Myeloma (Kahler’s Disease, Plasmacytoma) .. . . . . . . . . . . . .. .
4.1
Introduction
333 333 335 418 425 432 440 464 476 481
Brain tumours are a relatively rare pathology, and their incidence is less than 1 case per 20,000 (Orrison and Hart 2000), or 7.9–13 cases per 100,000 (Greig 1990). The morbidity peak is in elderly and senile patients, while in children the incidence is much lower, about 2–4 cases per 100,000. According to U.S. statistical data, about 15,000 cases of newly diagnosed patients with primary brain tumours are reported annually (Berens and Rutka 1990). On the basis of studies performed in the Great Britain, Germany, Finland and several other counties, WHO estimates the incidence of approximately 4.5–13 new cases of brain tumours per 100,000. In St. Petersburg, this number is about 13.9 patients per 100,000 people annually (Ulitin 2005). Presumably, the minimal annual morbidity of primary brain tumours in Russia and Moscow is about 14,000 and 1,000 patients accordingly (Yartsev 1997).
4.2
Supratentorial Tumours
It is known that about 80% of all newly diagnosed intracranial tumours are supratentorial. Approximately half of them are metastases. Annually, up to 11 per 100,000 new cases of
secondary brain tumours are diagnosed (Percy 1972). According to incidence rate, the neuroepithelial tumours are second, among which glioblastoma prevails. Solid tumours, by far, are one of the most frequent brain tumours in children, and according to their incidence, they rank second place after leukaemia (in accordance with some data). In the majority of cases, these tumours are primary ones. Metastases in children, contrary to adults, are observed much more rarely. Excluding first-year children and adolescents, about 70% of all intracranial tumours have infratentorial location, among them 75% are located in hemispheres of cerebellum and 25% in brainstem (Farwell 1977). Taking into account the calculation of overseas experts, the morbidity of primary and secondary CNS tumours in Russia reaches 40,000 patients annually, in Moscow, 2,500 (Yartsev 1997). Below is the international classification of CNS tumours (with modification), accepted and approved in 2007 (Louis 2007).
Histological Classification of Tumours of the Central Nervous System 1 1.1 1.1.1 1.1.1.1 1.1.1.2 1.1.1.3 1.1.2 1.1.3 1.1.3.1 1.1.4 1.1.4.1 1.1.5 1.1.6 1.2 1.2.1 1.2.2 1.3 1.3.1 1.3.2 1.3.3 1.3.4
Tumours of Neuroepithelial Tissue Astrocytic tumours Low-grade astrocytoma (well differentiated) Fibrillary Protoplasmic Gemistocytic Medium-grade (malignant) astrocytoma (anaplastic) High-grade astrocytoma (glioblastoma) Gliosarcoma Pilocytic astrocytoma Pilomyxoid astrocytoma Pleomorphic xanthoastrocytoma Subependymal giant cell astrocytoma Oligodendroglial tumours Oligodendroglioma Anaplastic (malignant) oligodendroglioma Ependymal tumours Ependymoma Anaplastic (malignant) ependymoma Mixed papillary ependymoma Subependymoma
334
Chapter 4
Histological Classification of Tumours of the Central Nervous System
Histological Classification of Tumours of the Central Nervous System
1.4 Mixed gliomas 1.4.1 Oligoastrocytoma 1.4.2 Anaplastic (malignant) oligoastrocytoma 1.4.3 Others 1.5 Choroid plexus tumours 1.5.1 Choroid plexus papilloma 1.5.2 Atypical choroid PP 1.5.3 Choroid plexus carcinoma 1.6 Brain gliomatosis 1.7 Neuronal and mixed neuronal–glial tumours 1.7.1 Gangliocytoma 1.7.2 Dysontogenetic (dysplastic) gangliocytoma of cerebellum (Lhermitte-Duclos) 1.7.3 Desmoplastic ganglioglioma in children (infantile) 1.7.4 Dysembryoplastic neuroepithelial tumour (DNET) 1.7.5 Ganglioglioma 1.7.6 Anaplastic (malignant) ganglioglioma 1.7.7.1 Central neurocytoma 1.7.7.2 Extraventricular 1.7.7.3 Cerebellar liponeurocytoma 1.7.8 Paraganglioma 1.7.9 Olfactory neuroblastoma (esthesioneuroblastoma) 1.8 Parenchymatous tumours of the pineal body 1.8.1 Pineocytoma 1.8.2 Pineoblastoma 1.8.3 Papillary tumor of the pineal region 1.9 Embryonal tumours 1.9.1 Medulloepithelioma 1.9.2 Neuroblastoma 1.9.2.1 Ganglioneuroblastoma 1.9.3 Ependymoblastoma 1.9.4 Primitive neuroectodermal tumours (PNET) 1.9.4.1 Medulloblastoma 1.9.4.1.1 Desmoplastic medulloblastoma 1.9.4.1.2 Anaplastic medulloblastoma 1.9.4.1.3 Melanin-containing medulloblastoma 1.9.4.1.4 Medulloblastoma with extensive nodularity
Benign tumours 3.2.1 Osteochondral tumours 3.2.2 Lipoma 3.2.3 Fibrous histiocytoma 3.2.4 Other Malignant tumours 3.2.5 Haemangiopericytoma 3.2.6 Chondrosarcoma 3.2.6.1 Mesenchymal chondrosarcoma 3.2.7 Malignant fibrous histiocytoma 3.2.8 Rhabdomyosarcoma 3.2.9 Meningeal sarcomatosis 3.2.10 Others 3.3 Primary melanocytic lesions 3.3.1 Diffusive melanosis 3.3.2 Melanocytoma 3.3.3 Malignant melanoma 3.3.3.1 Meningeal melanomatosis 3.4 Tumours of not clear histogenesis 3.4.1 Gemangioblastoma (capillary gemangioblastoma)
2 Cranial and Spinal Nerve Tumours 2.1 Neurinoma 2.1.1 Melanin containing neurinoma 2.2 Neurofibroma 2.2.1 Plexiform NF 2.3 Malignant neurinoma 2.3.1 Malignant tumour of peripheral nerves with divergence of the mesenchymal and/or epithelial differentiation 2.3.2 Melanin containing malignant neurinoma 3 3.1 3.1.1 3.1.1.1 3.1.1.2 3.1.1.3 3.1.1.4 3.1.1.5 3.1.1.6 3.1.1.7 3.1.2 3.1.3 3.2
Meningeal Tumours Tumours from meningothelial cells Meningioma Meningotheliomatous meningioma Fibroblastic meningioma Transitional (mixed) meningioma Psammomatous meningioma Angiomatous meningioma Secretory meningioma Clear cell meningioma Atypical meningioma Anaplastic (malignant) meningioma Mesenchymal non-meningothelial tumours
4 4.1 4.2 4.3
Lymphoma and Tumours of Blood-Forming Tissue Malignant lymphoma Plasmacytoma Granulocity sarcoma
5. 5.1 5.2 5.3 5.4 5.5 5.5.1 5.5.2 5.5.3 5.6
Tumours from Germ Cells (Germinogenic) Germinoma Embryonic cancer Yolk sac tumour (tumour of endodermal sinus) Choriocarcinoma Teratoma Immature Mature Malignant teratoma Mixed germinogenic tumours
6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9
Cysts and Tumour-Like Lesions Cyst of Ratke’s cleft Epidermoid cyst Dermoid cyst Colloid cyst of the third ventricle Enterogenous cyst Neuroglial cyst Granularcell tumour (choristoma, pituicytoma) Neuronal hamartoma of hypothalamus Nasal heterotopy of glia
7 7.1 7.2 7.3 7.3.1 7.3.2
Sellar Tumours Pituitary adenoma Hypophysis cancer Craniopharyngioma Adamantinomatous Papillomatous
8 8.1 8.2 8.3 8.4 8.5
Tumours Growing into the Skull Paraganglioma (chemodectoma) Chordoma Chondroma Chondrosarcoma Cancer
9
Metastatic Tumours
Supratentorial Tumours
This section is based on the results of neuroradiological examination with subsequent verification by stereotactic biopsy in more than 30,000 patients treated at the N.N. Burdenko Neurosurgical Institute in Moscow. Sixty percent of all cases were tumours originated from neuroepithelial tissue. Primary brain gliomas constituted the largest group among neuroepithelial tumours, observed in around 80% of all cases.
4.3
Neuroepithelial Tumours
Glial cells are the most numerous among all cellular brain populations; their number exceeds several times those of neurons, and they form about half of all tissue in the CNS (Angevine 1988). However, the proportions of different neuroglial cellular types can vary in different brain tissues. For example, in the cortex, the proportion of astrocytes is 61.5% in comparison with 9.5% of microglia cells and 29% of oligodendroglia, while in corpus callosum, the ratio between these fractions is 54, 6 and 40% (astrocytes, microglia and oligodendroglia, respectively) (Zemskaya 1985). Glial cells have a potential for pathological transformation and therefore they are the main supplier of CNS neoplasm. So, according to statistical data, approximately two thirds of brain tumours are primary ones, and among them more than 50% are glial neoplasm. But histological structure of glial cells is not uniform, and they are divided into several cellular subtypes: astrocytes, oligodendrocytes and ependymocytes. In this regard, glial tumours are divided into three basic subgroups–astrocytic glioma, oligodendroglioma and ependymoma. The statistical data is interesting, because more than three quarters of all glioma are astrocytoma, and the proportion of malignant tumours (anaplastic astrocytoma) among them is the largest (more than three quarters). The first classification of neuroepithelial tumours belongs to Bailey and Cushing (1926). It is based on the histological similarity that is observed between some types of nervous system cells developing in the course of normal ontogenesis and tumour cells. The classifications taking into account other points of view were developed later on. Among them, the classifications of Kernohan and Sayre (1952), Smirnov (1962), Hominskyi (1969), Zulch (1965, 1986), and Russell and Rubinstein (1989) are the most known. During the past three decades, neurohistologists have obtained plenty of additional information about histogenesis of CNS tumours, membranous proteins, growth factors, oncogenes and growth kinetics. New morphological techniques, such as immunohistochemistry and molecular genetic analysis, have gained widespread usage. All these developments led to the changes in the WHO classification of brain tumours adopted in 1979. New data about tumour structure led to modification for several times and broadening of this classification in 1993, 2000 (Kleihues and Cavanee 2000) and Louis (2007). According to various estimates, neuroepithelial tumours make up 50% of all brain tumours, and this is the most representative group. In adults, these tumours mainly have supratentorial locations, while for children the lesions of the posterior cranial fossa are more typical. As in adults, in chil-
335
dren intracranial neoplasms of the supratentorial area also have mainly glial origin (more often they are astrocytoma and ependymoma). Unlike adults, tumours originating from neuroglia are seldom observed in children. Approximately two thirds of all intracranial neoplasms are benign forms. Among these neoplasms the astrocytoma is the most frequent form; its incidence is close to 30% of all supratentorial tumours. Then ganglioglioma (6%) and pleomorphic xanthoastrocytoma are diagnosed. Supratentorial ependymoma is a more frequent finding in children than in adults. Their proportion is from 20 to 40% of all ependymoma in children. Primary glioma is the largest group among all neuroepithelial tumours. According to their histological types the gliomas are divided into the following groups: (1) astrocytoma, (2) oligodendroglioma and (3) ependymoma. The last type also includes tumours of choroid plexus, which contain modified ependymal cells; the growth of such tumours has many common characters with others gliomas. In addition, in groups of neuroepithelial tumours there are mixed forms of gliomas (oligoastrocytoma and others), tumours of unknown origin (for instance, brain gliomatosis), and neuronal or neuroglial tumours. According to Russell (1989), about 40–45% of all intracranial tumours are gliomas, and they form the heterogeneous group of brain neoplasms that contain relatively benign forms as well as very malignant tumours.
WHO Classification of Brain Gliomas (2007) Astrocytic Tumours Low-grade astrocytoma The term benign astrocytoma is not used at present due to invasive growth and steady progression to malignancy in time by most of these tumours Anaplastic (malignant) astrocytoma Glioblastoma Variant: gliosarcoma Pilocytic astrocytoma Pleomorphic xanthoastrocytoma Subependymal giant cell astrocytoma Oligodendroglial Tumours Oligodendroglioma Anaplastic oligodendroglioma Ependymal Tumours Ependymoma Anaplastic ependymoma Myxopapillary ependymoma Subependymoma Mixed Glioma Oligoastrocytoma Anaplastic oligoastrocytoma Others Tumours of the Choroid Plexus Choroid plexus papilloma Choroid plexus carcinoma
336 WHO Classification of Brain Gliomas (2007) Brain Gliomatosis Neuronal and Mixed Neuroglial Tumours Gangliocytoma Dysplastic gangliocytoma of cerebellum (Lhermitte-Duclos) Desmoplastic ganglioglioma in children (infantile) DNET Ganglioglioma Anaplastic (malignant) ganglioglioma Central neurocytoma Olfactory neuroblastoma (esthesioneuroblastoma) Olfactory neuroepithelioma
4.3.1 Astrocytic Tumours Astrocytic tumours (ASC) are divided into two large categories. Tumours with diffuse growth, characterised by poor prognosis, belong to the first category. They make up about 75% of all astrocytic neoplasms. Tumours with increasing (different) degree of anaplasia from low-malignant astrocytoma to glioblastoma, characterised by the absence of clear macro- and microscopic borders separating tumour with surrounding tissue, belong to this category. The second category of tumours is delimited tumours, with better prognosis (pilocytic astrocytoma, pleomorphic xanthoastrocytoma and subependymal giant cell astrocytoma). They are characterised by a clear border between tumour and normal tissue. Astrocytic tumours are histologically a heterogeneous group of primary tumours, and they are the most frequently observed type of neuroepithelial tumours. They make up about 6–21% of all intracranial tumours and about 40% of all glial tumours. In children, the incidence of cerebrum astrocytoma reaches approximately 30% of all supratentorial brain tumours. Taking into account that fact that diffuse astrocytoma develops from neuroglia, they can be divided according to the histological criteria of malignancy and also according to the type of astrocyte (fibrillary or pilocytic one) for cellular proliferation. Such division has a prognostic value, because pilocytic astrocytoma seldom becomes malignant, and it can be totally removed, which is not the issue when infiltrative fibrillary astrocytoma is concerned. The incidence of diffuse astrocytomas is about 25–30% of all hemispheric gliomas, and approximately about 30% of all cerebellar gliomas are found in children. The incidence of supratentorial astrocytomas peaks between 20 and 50 years; that is about 10 years less than in cases of glioblastoma. These tumours can develop in any brain lobe; however, the occipital lobes are affected less frequently. Bilateral invasion can happen in the case of a tumour deeply seated. White matter as well as grey is involved into pathological process. Low-degree astrocytoma has better prognosis than does the malignant form. Unfortunately, the prognosis of such diseases is always poor. Life expectancy in cases of astrocytoma
Chapter 4
varies from 2.5 to 15 years. Moreover, it is known that about 10% of benign lesions can develop into more (sinister) malignant forms. According to Piepmeier (1987), 50% of surgically treated benign tumours transform into anaplastic astrocytoma or glioblastoma. The progressive growth of fibrillary astrocytoma can also be observed without increase of the level of anaplasia. Division of diffuse glioma depending on the grade of malignancy is an important point in treatment selection and subsequent prognosis. The WHO classification (2000) divides diffuse astrocytic glioma into three groups according to the degree of malignancy from low-grade astrocytoma (LGA) to anaplastic astrocytoma (AA) and then to glioblastoma (GB). The criteria include the presence of nuclear and cellular polymorphisms, proliferation of vessel endothelium, presence of mitosis, and foci of necrosis. It should be noted, however, that despite benign histological structure, all infiltrative low-malignant astrocytoma have poor prognosis. LGA in comparison with more malignant form is rare; its incidence is about 10–15% of all cases of glioma, it affects young patients and it is characterised by better prognosis. LGA is an infiltrative tumour; however, it can have clear radiological borders. Macroscopically it has grey colour, various consistency (from dense to gelatine-like) and it is difficult to separate it from brain tissue. The foci of cystic degeneration can be observed in tumour, while the foci of necrosis are never found. Microscopically, the fibrillar astrocytoma consists of mature tumour astrocytes, with a rare arrangement of cellular bodies and rather monomorphic nuclei. Mitosis, haemorrhages and proliferation of vessel endothelium are absent. In typical cases of LGA, cerebral angiography detects an area with a small quantity of vessels (sometimes an avascular area) without pathologically formed arteries or arteriovenous shunts. However, more often the angiography data are negative, or minimal in the form of an insignificant disposition of the cerebral arteries (more often anterior and middle cerebral arteries) from their typical location (Fig. 4.1). The CT image of LGA is a hypodense area without clear borders with surrounding brain tissue (Fig. 4.2). Sometimes, isodense types of tumour can be observed, leading to their late diagnosis if only CT examinations were conducted. Intravenous contrast administration usually does not lead to density change, or it can result in a separate hyperintense foci on a background of hypodense zone (Figs. 4.3, 4.4). Calcifications in the form of small or large hyperintense foci are diagnosed in 15–20% of cases (Fig. 4.5). Cyst formation is a rare albeit possible sign of tumour (Fig. 4.6). Radiological clearness of tumour borders varies and depends on the level of change of tumour tissue density. Borders are better visualised in cases of astrocytoma of low density, while isodense tumours are characterised by their much worse visibility (Fig. 4.7). After contrast administration, the density of astrocytoma, located in the bottom of the third ventricle, subcortical ganglia, and posterior cranial fossa, increases; the formation of cysts is also typical for these astrocytomas. However, as a rule, according to histological structure, these tumours are pilo-
Supratentorial Tumours
337
Fig. 4.1a–c Fibrillary astrocytoma. An area of pathologically changed MR signal (a) is visualised on MRI in right temporal lobe. Cerebral
angiography in direct projection does not reveal vascular net of the tumour; the vessels of middle cerebral artery underwent upward dislocation (b arterial phase, c capillary phase)
Fig. 4.2a,b Fibrillary astrocytoma of the
right posterior frontal lobe. a,b CT with contrast enhancement. The tumour is hypodense in comparison with brain tissue. Tumour does not show contrast accumulation
338
Fig. 4.3a–c Fibrillary astrocytoma of the left temporal lobe. CT before (a) and after (b,c) contrast enhancement. The spread hypodense area without clear borders is detected in the left temporal lobe. There
Chapter 4
are not any areas of contrast accumulation in the tumour. The density of vessels (middle and posterior cerebral arteries) on the periphery of astrocytoma increased
Fig. 4.4a–c Fibrillary astrocytoma of left parietal lobe. CT before (a) and after (b,c) contrast enhancement. The area of uneven density de-
crease without clear borders is observed in the left parietal lobe. Contrast enhancement is absent
Supratentorial Tumours
339
Fig. 4.5a–c Variants (a–c) of fibrillary astrocytoma of different locations. CT without contrast enhancement reveals the tumours of isodense
(a,b) and slightly hypodense (c) structure, with calcifications (foci of increased density) in the tumour stroma
Fig. 4.6a,b Cystic astrocytoma of the right
posterior frontal lobe. CT before (a) and after (b) contrast enhancement shows a hypodense area. The neighbouring gyri are compressed. The contrast enhancement of the tumour is absent
Fig. 4.7a,b Astrocytoma of right temporal–
occipital–parietal area. Axial CT images with contrast enhancement (a,b) demonstrate the wide area of uneven density change without clear borders. This area does not accumulate contrast. Compression and dislocation of the right lateral ventricle is detected
340
Chapter 4
Fig. 4.8a–c Fibrillary astrocytoma. T2-weighted image (a), T1-weighted image before (b) and after (c) contrast enhancement. The tumour with relatively homogeneous structure is visualised in the left frontoparietal area. Tumour does not accumulate contrast. The adjacent cerebral gyri are compressed
cytic astrocytomas (see below). The typical hemispheral LGA does not enhance contrast on CT examination. As mentioned above, with the use of CT it is difficult to identify isodense infiltrative tumours in cases in which they do not lead to substantial increase of the affected area volume or to accompanying dislocation of neighbouring brain, vascular or CSF formations. The neoplasms located in basal temporal area or in convex areas of frontal and temporal lobes are the most difficult for CT detection, due to various reasons (e.g. artefacts from neighbouring bony structures of a skull). It is reasonable to conduct an examination in a frontal projection in cases of even the slightest suspicion of brain change density or signs of dislocation of cerebrospinal spaces on the convex surface of a brain. However, this is not always helpful, especially if the patient has a metal pivot tooth, which forms strong artefacts on the image. On MRI, LGA is iso- or (more often) hypointense on T1-weighted images (Figs. 4.8, 4.9). As a rule, the tumour is hyperintense with relatively homogeneous signal on T2 sequences. FLAIR imaging leads to highly heterogeneous signal from tumour tissue. However, the certain heterogeneity of MR signal is peculiar to astrocytoma on any type of image (Figs. 4.10–4.12). Because these tumours are usually diagnosed at a stage of obvious clinical signs, they can reach relatively large volumes and can simultaneously affect several neighbouring brain lobes, without precise “binding” to any arterial territory (Fig. 4.13). This should always be kept in mind in cases of differential diagnosis with acute or subacute stroke, especially if MRI equipment lacks special diffusive software.
It is believed that perifocal oedema is not typical for this type of tumour. However, detecting an equivocal tumour from perifocal oedema by CT or MRI is not possible because of relatively similar densities and types of signal change. It is widely known that benign hemispheric astrocytoma with diffuse growth does not accumulate contrast agent in the overwhelming majority of cases (Fig. 4.14). Calcifications in the stroma of astrocytoma can be better detected by CT rather than by MRI (Fig. 4.15). The destruction of white as well as grey matter is typical for diffuse astrocytoma. This leads to blurring of the borders between them. The gyri look thickened, and the mass effect is detected as dislocation of neighbouring structures and narrowing of the subarachnoid spaces. The larger tumours cause brain and ventricular system dislocation accompanied by the development of different (the most frequent is descending tentorial herniation) impactions. Approximately 10–12% of all cases are cystic or atypical diffuse astrocytoma with focal or intensive contrast enhancement (Figs. 4.16, 4.17). In certain situations in cases of late diagnosis, tumour infiltration can spread to large and lengthy brain areas, sometimes causing total damage of one hemisphere and passing to the opposite part, even infiltrating inside ventricles and subarachnoid spaces (Figs. 4.18–4.21). In general, it is noteworthy that MRI is a method more sensitive for visualising all subtypes of astrocytomas (including low-grade ones) than CT due to its high image contrast. Meanwhile, T2 and FLAIR sequences are more informative (Fig. 4.22). However, even MRI poorly detects tumour borders. It should be noted that infiltrative growth leads to the
Supratentorial Tumours
Fig. 4.9a–f Fibrillary astrocytoma of the parietal–frontal lobes (7-year-old child). The hypodense area in the projection of precentral gyrus in the right hemisphere without contrast accumulation is observed on CE CT (a). T2-weighted image (b) and T1-weighted im-
341
age before (c) and after (d) contrast enhancement reveal astrocytoma of small size. On DWI (b = 500) a tumour has homogeneous hyperintense MR signal (e). MRS demonstrates decrease of NAA and appearance of Lac (f) peaks
342
Fig. 4.10a–c Fibrillary astrocytoma. On CT in the right posterior
frontal–temporal lobes, there is a hypodense area (a). T2-weighted image (b) and T1-weighted image (c) show the spread area of patho-
Chapter 4
logical change of MR signal intensity; the size of the lesion can be better evaluated on T2-weighted imaging; the MCA are partly included into the tumour’s stroma
Fig. 4.11a–c Fibrillary astrocytoma of right frontal lobe (upper frontal gyrus). T2-weighted imaging (a), FLAIR (b) and T1-weighted imaging with contrast enhancement (c) detect the tumour with microcysts in its central part; the latter look dark on T1-weighted imaging and FLAIR. Tumour does not accumulate contrast medium
Supratentorial Tumours
Fig. 4.12a–f Fibrillary astrocytoma of left frontal lobe. T1-weighted image in axial (a) and coronal (b) projections depicts an area of heterogeneous change of MR signal. Tumour does not accumulate
343
contrast (c). The heterogeneity of the tumour structure can be better observed on FLAIR (d) and T2 (e). DWI (b = 1,000) demonstrates the slightly limited diffusion in peripheral parts of tumour (f)
344
Chapter 4
Fig. 4.13a–c Fibrillary astrocytoma of left frontal–temporal lobes. T2-weighted image (a) and T1-weighted image (b) with contrast enhance-
ment. The widespread tumour with unevenly changed MR signal is visualised. Tumour does not accumulate contrast. Coronal FLAIR (c) clarifies basal and medial spreading of the tumour
Fig. 4.14a–c Fibrillary astrocytoma of right frontal–temporal lobes. T2-weighted image (a) and T1-weighted image before (b) and after contrast enhancement (c) demonstrates large tumour with point sites of contrast accumulation
Supratentorial Tumours
Fig. 4.15a–c Fibrillary astrocytoma of right parietal lobe (a 9-year-
old child). The tumour mass of uneven structure with calcifications is observed on CT (a) with contrast enhancement. The tumour
Fig. 4.16a–c Fibrillary astrocytoma of right frontal lobe (a 3-yearold child). a CT image with contrast enhancement. The tumour of uneven structure with intense contrast medium accumulation and peritumoral oedema is visible in the projection of right frontal lobe.
345
has heterogeneous structure on axial T2-weighted imaging (b) and T1-weighted imaging (c). In this case, the medially located cyst is detected better. Calcifications are not visible on MRI
On T1-weighted imaging, the tumour has an MR signal like grey matter has (b). The tumour structure and borders are better demonstrated after contrast enhancement (c)
346
Chapter 4
Fig. 4.17a–c Astrocytoma. An area of pathological change of signal is visualised on T2-weighted imaging (a) and T1-weighted imaging (b). The neighbouring brain sulci are compressed. After contrast enhancement (c), the focus of contrast accumulation is revealed (arrow) in the depth of lesion
Fig. 4.18a–c Astrocytoma with intraventricular, subarachnoid spreading (a 12-year-old child). T2-weighted imaging (a) with dilation of lateral ventricles detects the unevenly hyperintense tumour in the lumen of posterior horn of right lateral ventricle. The tumour blends with signal from CSF. T1-weighted imaging in sagittal
projection (b) demonstrates hypointense tumour spreading from right lateral ventricle into cisterns of brain base (the suprasellar, interpeduncular and ambient cisterns). FLAIR (c) sequence allows receiving more reliable information about the tumour’s infiltration
Supratentorial Tumours
347
Fig. 4.19a–c Astrocytoma of intraventricular subependymal spreading. T1-weighted image before (a,b) and with contrast enhancement (c) detects diffusive nodal tumour spreading along ependyma of lateral ventricles. In the projection of Monroe’s foramen in the left hemisphere, the contrast-enhanced part of tumour is observed
Fig. 4.20a–c Bilateral astrocytoma of thalamus (a 6-year-old child). T2-weighted imaging (a), FLAIR (b) and T1-weighted imaging with contrast enhancement (c) detect spread of bilateral lesion of basal ganglia with the involvement of the insular part of the cortex of left temporal lobe. Tumour does not accumulate contrast medium
348
Chapter 4
Fig. 4.21a–f Bilateral astrocytoma of basal ganglia (an 8-year-old child). T2-weighted image (a), FLAIR (b) and T1-weighted image before (c) and with contrast enhancement (d) reveal spread of bilateral lesion of basal ganglia with the involvement of putamen, head of caudate nucleus and the insular part of the cortex of right tem-
poral lobe. Tumour does not accumulate contrast. The elements of descending tentorial herniation are observed in sagittal projection (e). DWI (f) demonstrates the tumour with MR signal, which is close to that of grey matter
spreading of tumour tissue beyond the area of signal change visible on the T2-weighted image (FLAIR). On DWI (b = 1,000) LGA has isointense or slightly hypointense signal in comparison with normal white matter (Figs. 4.23, 4.24). This astrocytoma appears as a homogeneous hyperintense lesion with relatively clear borders separable from brain tissue. At the same time, the peripheral part of tumour has a transitional level of MR signal and an ADC that can correspond to marginal area of tumour infiltration. The average value of ADC for LGA is 1.52 ± 0.4 mm2/s according to our studies. Tumour cells have relatively random arrangement and monomorphic nuclei, and in such conditions, water molecules can easily diffuse within the structure of tumour tissue. This circumstance can possibly predetermine relatively high values of diffusion coefficient in the benign astrocytoma with diffuse growth. MR tractography provides additional information about the structure of nervous fibres of white matter in the area of astrocytoma. Tumour causes
the destruction of pathways in some cases and displacement in others (Fig. 4.25). Presemtly, CT and MR perfusion techniques are available in preoperative planning and estimation of sites of neoangiogenesis in tumour tissue (Fig. 4.26). The spectroscopic characteristics of LGA are not specific; nevertheless, MRS reveals decrease of ratio between peaks of NAA–Cr and Cho–Cr. Absence of a Lac peak in a spectrum is evident for benign character of a brain lesion; with CT and MRI, there are other signs for differentiation of malignancy degree (Figs. 4.27, 4.28). There is a gradual transformation of benign astrocytoma to anaplastic one, a well-known fact from the literature that can be demonstrated by follow-up CT and MRI examinations. In addition, the presence of an area of contrast enhancement in structure of LGA can point to the part of the tumour with more aggressive growth. The combination of several different diseases of CNS is a rare albeit possible phenomenon, especially if the fact of long-term growth of LGA would be taken
Supratentorial Tumours
349
Fig. 4.22a–c Fibrillary astrocytoma of left temporoparietal area. CT at the level of lateral ventricles bodies (a) demonstrates an uneven hypodense area without clear borders. The spreading of neoplasm with the involvement of white and grey matter can be better (in comparison with CT) evaluated on FLAIR (b) and T2-weighted imaging (c)
Fig. 4.23a–c Fibrillary astrocytoma in right central gyri. T2-weighted imaging (a) detects the area of pathological hyperintense MR signal in the projections of right central gyri. Tumour does not accumulate contrast on T1-weighted imaging (b). On DWI, tumour looks virtually identical to surrounding brain tissue (c)
Fig. 4.24a–c Fibrillary astrocytoma of left posterior frontal – temporal area. DWI b=1000 (a) reveals MR-signal decrease from anterior (cys-
tic) part of tumor. MR signal from whole tumor is close to those from non affected grey matter. On T2 (b) and T1 (c) WI tumor has uneven structure and signal characteristics typical for glioma
350
Fig. 4.25a–f Diffusive astrocytoma of left frontal lobe. Case 1.
T2-weighted image (a) reveals infiltrative tumour affected both white and grey matter. MR 2D tractography (b,c) detects disorganization of white matter tracts in an area of tumour growth (arrows). Case 2.
Fig. 4.26a–c Diffusive astrocytoma of right temporoparietal area. T2-weighted image (a) reveals spread infiltrative and growing tumour without clear borders, which compresses the right lateral ventricles. CT with contrast enhancement (b) does not detect the focal
Chapter 4
T2-weighted image (d) demonstrates small mass lesion into superior frontal gyrus. MR imaging: fractional anisotropy map (e) and 3D tractography (f) show dislocation of white matter tracts
contrast accumulation of the tumour tissue. Perfusion map (CBV) demonstrates the absence of changes of haemodynamic parameters in comparison with the white matter of the opposite hemispheres (c)
Supratentorial Tumours
351
Fig. 4.27a–c Fibrillary astrocytoma of the right frontoparietal area. FLAIR image (a) shows the infiltrative tumour with slightly hyperintense
MR signal. On T2-weighted image (b), the square indicates points out the site of spectra taking. MRS (c) demonstrates decrease of NAA and increase of Cho
Fig. 4.28a–f Fibrillary astrocytoma. On T2-weighted image, the lesion has a hyperintense MR signal, and the position of multivoxel MRS at the level of tumour’s location is seen (a). Spectra reveals high Cho peak, reduced NAA peak and small peak of Lac–Lip complex (b); distribution to concentrations of metabolites on colour maps
(c,d) is seen. On the spectra profile (e,f) changes in tumour and surrounding tissue are observed: a zone of tumour’s infiltration (medially from border of lesion), which is not detectable on T2-weighted imaging, is visualised
352
Chapter 4
into account (Figs. 4.29, 4.30). Thus, it is important in such cases not only to detect lesions, but also to distinguish their origin, or to establish identity of the presumable histological structure of tumours. It is especially required in cases of primarily multiple ASC (Figs. 4.31, 4.32). Nowadays using of MRI and 3D reconstructing is obliged component of any preoperative MR imaging for accuraty planning of surgical approach—with information about functionally important cortical centers and surface veins location in on site of proposed craniotomy (Fig. 4.33,4.34). DTI- and MR tractography provides additional information about the character of tumour growth. Thus, in an area of infiltrative growth, astrocytoma decomposes nervous fibres, while on the periphery the displacement of neighbouring pathways of white matter is mainly observed (Helton et al. 2006; Stadlbauer et al. 2007). AA occupies the intermediate position between benign astrocytoma ASC and glioblastoma. Inside this group there is certain heterogeneity of the degree of anaplasia. AA is an infiltrative tumour with poorly outlined borders. Cystic degeneration and haemorrhages are often observed, but necrosis at histological examination is absent. The incidence of AA is up to a third of all cases of astrocytoma and a quarter of all glioma. In the majority of cases (up to 75%), it develops from LGA. The congestion of densely arranged astrocytes with polymorphism and hyperchromatosis of the nuclei are typical for AA on microscopic examination. Stages of mitosis (mitotic division) are revealed in tumoral cells and in some vessels, i.e. proliferation of endothelium cells (Matsko and Korshunov 1998; Kleihues and Cavanee 2000). AA can be found in patients of any age; however, more frequently they are observed in elderly patients. The incidence peaks during the fifth and sixth decades of life. Epileptic
seizures and focal neurological signs prevail in the clinical picture of the disease. Like all glioma, AA can be detected in any area of brain hemisphere; however, lesions of frontal and temporal lobes are more common. The spreading of a tumour on the subcortical structures and on an opposite hemisphere is not an unusual phenomenon. Protoplasmatic AA is often located peripherally in cortical layers (protoplasmatic astrocytes are normal components of grey matter). AA is seldom observed in subtentorial structures. The prognosis for patients with such tumours is poor, and average life expectancy is about 2 years. AA is a non-homogeneous tumour, with mixed density on CT, although, according to the opinions of some researchers (Osborn 2004), AA does not accumulate contrast. In our studies after contrast administration, tumour heterogeneity increases. The areas of contrast accumulation are heterogeneous or have lumpy shapes. Ring-shaped contrast enhancement can point to the transformation of the tumour to glioblastoma. Oedema of various degrees is usually visible around the tumour; it has low density and a typical spreading in white matter. Calcifications and haemorrhages are seldom phenomena (Fig. 4.35). On MR scans, AA looks like poorly outlined (delimited) formations, which have heterogeneous signal on T1- as well as on T2-weighted images. On T1 scans, there are areas of mixed and hypointense signal. Haemorrhagic foci with their typical hyperintense signal can be observed. The presence of wide areas of heterogeneous hyperintensity of MR signal is typical for AA on T2 and FLAIR sequences. The foci of cystic degeneration can be detected in the tumour’s centre (Figs. 4.36, 4.37). Perifocal oedema, which has hyperintense signal and a typical form of divergent rays, can be better visualised with the use of the same sequences. Significant mass effect is detected in
Fig. 4.29a–c A combination of fibrillary astrocytoma of right the frontotemporal area and sarcoma of the tongue with metastases into neck lymph nodes. T2-weighted image in axial (a), coronal (b) and sagittal (c) projections visualises intracranial infiltrative hyperin-
tense tumour. In addition, the tumour node is detected in the projection of the tongue’s roots (arrows) and increased submaxillary lymphatic nodes (arrows)
Supratentorial Tumours
353
Fig. 4.30a–c The combination of diffusive glioma of right temporoparietal area and AVM in the territory of the MCA. T2-weighted image (a): the AVM vessels are visualised dorsally from tumour (arrows). The angiograms (b,c) reveal small AVM (arrows) in parietal area with blood supply from both the ACA and ICA
Fig. 4.31a–f Multiple astrocytoma of brain hemispheres. T2-weighted image (a,b) and FLAIR (c,d) show multiple hyperintense foci of subcortical location. On DWI (e), these mentioned foci are practically unrevealed. Foci have identical characteristics in all scanning
sequences. MRS (f) detects a decrease of NAA, and appearance of a Lac–Lip complex. The target biopsy of focus in the left frontal lobe established diagnosis of astrocytoma
354
Fig. 4.32a–f Multiple astrocytoma of right brain hemisphere.
T1-weighted imaging (a,b) and T2-weighted imaging (c) show two tumours that are hyperintense (on T2-weighted image) and hypointense (on T1-weighted image). On DWI (d), these tumours are slight-
Chapter 4
ly hypointense. Tumours have similar MRI characteristics. fMRI (e) shows a site of activation of left-sided motor centre located between revealed tumours. MRS (f) detects in both nodes the peak of Lac–Lip complex, and the increase of Cho
Fig. 4.33a–c 3D reconstruction of cortical surface of brain hemispheres with target-segmented virtual “removing” of brain tissue in an area of astrocytoma (a,b). T1-weighted image (c) with superposition of function examination data (1) demonstrates the interaction of tumour of precentral gyrus and left-sided motor centre
Supratentorial Tumours
Fig. 4.34a–f 3D reconstruction of cortical surface of brain hemi-
spheres with target-segmented virtual “removing” of brain tissue in an area of astrocytoma under different view angles: from above
Fig. 4.35a–c Variants of AA of cerebral hemispheres on CT: tumours
of the left frontal lobe are with uneven structure without contrast medium accumulation (a), the tumour of the cingulate gyrus and
355
(a–c), sagittal with 45° turn (d–f). MRI is performed with contrast enhancement, and reconstruction is done with visualisation of surface veins in an area of proposed craniotomy
the left frontal area with focus of contrast enhancement (b) and a tumour of the right temporofrontal area with intense contrast medium accumulation (c)
356
Fig. 4.36a–f AA of the left frontal lobe. T1-weighted image (a), T2-weighted imaging (b) and T1-weighted imaging with contrast enhancement (c,d) detect spread area of pathologically changed MR signal with intratumoral subcortical haemorrhage—hyperintense
Chapter 4
MR signal (a). Contrast accumulation has uneven focal character. On FLAIR (e,f), microcysts (zones of low signal) are visualised with an area of hyperintense MR signal
Supratentorial Tumours
357
Fig. 4.37a–f AA of the right frontal lobe. T2-weighted imaging (a), T1-weighted imaging before (b) and after contrast enhancement (c,d), and FLAIR (e,f) detect the tumour of uneven structure with microhaemorrhages. Tumour cysts are located on neoplasm convex surface
358
cases of larger tumour or marked oedema (Fig. 4.38). Signal strengthening is typical for the majority of AA after contrast administration. However, it does not improve the visualisation of an internal structure and macroscopic borders of a tumour. Contrast accumulation is stronger in comparison with CT. Nevertheless, more often the focal rather than diffuse contrast enhancement in tumour structure is visualised. In the AA with cystic changes, the MR signal from the cystic part is higher than from CSF, and the contrast accumulation on periphery is typical because the tumour tissue forms the walls of the cyst (Fig. 4.39, 4.40). Tumours without perifocal oedema and contrast enhancement can also be observed. According to our data, the incidence of this kind of tumour is up to 15% of all AA (Fig. 4.41). It is possible to suspect AA on the basis of CT and MRI data with respect to the following changes: the marked heterogeneity of density and MR signal on T1 and T2 (FLAIR) sequences, perifocal oedema, foci of contrast enhancement or marked enhancing (including cysts walls), the fast growth demonstrated on follow-up scans or haemorrhage in tumour (Figs. 4.42–4.44). Spreading along the tracts of white matter in the majority of AA cases leads to revealing, with the help of target biopsy, the tumour cells in brain areas surrounding the zones of contrast accumulation; also, such cells can be found outside the areas of hyperintense signal on T2 scans. Graff et al. (1992) noted that AA spreads on ependyma, pia matter and subarachnoid space. The involvement of cortical structures of the affected hemisphere is typical for the tumour. The increase in heterogeneity of MR signal and the appearance on DWI with b = 1,000 c/mm2 areas of hyperintensity usually not visible in cases of LGA are observed on DWI. Thus, the values of ADC are different in the tumour tissues accumulating or not enhanced by contrast (Figs. 4.45, 4.46). The average value of ADC fluctuates around 1.18 to 1.23 ± 0.32 mm2/s. The index of partial anisotropy decreases with the increase of anaplastic changes in tumours. Infiltrative growth leads to total destruction of the main structural elements of white matter, especially pathways (Goebell et al. 2006). In this situation, MR tractography is one of the unique methods of in-vivo examination, its role is especially important in cases of preoperational assessment of pathways state (Jellison et al. 2004). Usage of tractography improves the planning of operational access and revision of tumour resection. CT and MRI perfusion examinations provide an additional contribution in evaluation of structural changes occurring in a tumour tissue during anaplastic transformation (Sadeghi et al. 2007). The foci of anaplasia are characterised by the typical moderate increase of haemodynamic parameters, especially CBV It is necessary to note that hypoperfusion areas do not necessarily coincide with zones of contrast accumulation on postcontrast images. Moreover, the CT perfusion data obtained in the process of planning the target for stereotactic biopsy in patients with AA are more informative in comparison with the ordinary contrast enhancement. The foci of increased CBF in the structure of neoplasm become the target in these cases (Figs. 4.47, 4.48).
Chapter 4
MRS (Fig. 4.49a–c) in cases of AA reveals the increase of ratio between peaks Cho and Cr, and decrease of NAA peak height (Podoprigora 2000; Nelson et al. 2002; Ketonen et al. 2005; Goebell et al. 2006). MR tractography demonstrates mainly the destructive character of tumour growth, with destruction of neural fibres and loss of their typical orientation in the space. Pathway dislocation is mainly detected in cases of slow tumour growth in comparison with the primary LGA (Fig. 4.49d–f). GB is the most malignant of all glial tumours, and it occupies a great portion of the astrocytoma spectrum. It is the most frequent primary CNS tumour, whose incidence is about 10–20% of all intracranial tumours (Orrison and Hart 2000; Osborn 2004). GB makes up approximately half of all gliomas, and it is the most frequent supratentorial tumour in adults; usually it is observed in patients after age 50 years and is rare before 30 years. The tumour (insignificantly) prevails in men. According to Romodanova (1965), these tumours make up 5% of all brain neoplasms in children, while Dropcho et al. (1987) point out that their rate is higher, from 7 to 11%; in our observations, about 3% of all are childhood GB. Macroscopically, GB usually is a formation that has a heterogeneous structure with central necrosis and highly vascularised stroma. According to histological data, GB is a tumour with a high level of cytological atypia and mitotic activity. The multiple foci of necrosis with the presence of so-called pseudopalisade structures in the form of multinuclear palisade of hyperchromatic nuclei and marked proliferation of the endothelium cells are characteristics of GB (Matsko and Korshunov1998). As well, in cases of other infiltrative glioma, there are no clear borders between tumour, oedema and normal tissue. The rapid increase of clinical symptoms and sudden worsening due to increase of intracranial pressure and not infrequently, impaction, is observed in patients with this malignant tumour. Often less than 1 month passes from the disease onset to virtually total disability of the patient. In the majority of cases, GB affects cerebrum, and it more often is located in deep-seated areas of white matter of temporal, frontal and parietal lobes, and in the corpus callosum, with the spreading into one or two hemispheres in the form of a butterfly; rarely is it found in cortex and posterior cranial fossa, and in basal ganglia (Stark et al. 2005). Metastasis within CNS can be observed. Patients with GB have the poorest prognosis among all primary CNS tumours. The average life expectancy is about 8 months; 5-year survival is observed extremely rarely (Lacroix et al. 2001). Tumour density on CT is relatively heterogeneous. The central area of tumour is a zone of necrosis, with low density, seen in 95% of cases. Calcifications are very rarely found in GB, whereas haemorrhages of various ages are frequent findings. Usually the tumour is surrounded by intense perifocal oedema spreading into the white matter. After contrast administration is marked, although heterogeneous, contrast enhancement is observed, more often in a ring shape with uneven internal contour (Figs. 4.50–4.52). Sometimes GB does not have a separate node, but infiltrates and widely affects the entire hemisphere and has minimal radiological signs of
Supratentorial Tumours
359
Fig. 4.38a–h AA of left frontal-temporal area are spreading to the opposite side. T2-weighted image (a–d), FLAIR (e) and T1-weighted image before (f) and with contrast enhancement (g,h) show a widespread tumour of uneven structure that infiltrates corpus callosum and causes dislocation of lateral ventricles
360
Chapter 4
Fig. 4.39a–e AA of the left frontal-temporal area with large tumour cyst. T2-weighted image (a), T1-weighted image before (b) and with contrast enhancement (c–e) show a large tumour with uneven structure with intense contrast accumulation. The tumour compresses the adjoining lateral ventricle. Cyst walls accumulate contrast medium
Fig. 4.40a–c AA of right frontal-parietal area (an 8-year-old child).
CT with contrast enhancement (a) reveals neoplasm of a large size, which has solid node and large tumoral cyst. The lateral ventricles are compressed and dilated due to hydrocephalus. MRI: T2-weighted
image (b) and T1-weighted image after contrast enhancement (c) clearly reveal the tumour spreading and its structure. Cyst wall intensively accumulates contrast medium
Supratentorial Tumours
361
Fig. 4.41a–c AA of medial segments of the left frontal area with affected corpus callosum. T2-weighted image (a), T1-weighted image before
(b) and with contrast enhancement (c). The large tumour of uneven structure without obvious perifocal oedema and contrast accumulation is visualised
Fig. 4.42a–c AA of left frontotemporal area. T2-weighted image (a), T1-weighted image before (b) and with contrast enhancement (c) show the tumour of uneven structure with prominent perifocal oedema and foci of contrast accumulation. Structures of the tumour
with different characteristics of MR signal and contrast enhancement indicate possible malignant transformation of primary benign astrocytoma
362
Chapter 4
Fig. 4.43a–g AA of right frontotemporal area. CT before (a) and with contrast enhance-
ment (b) reveals large neoplasm with a solid node and a tumour cyst. The lateral ventricles are compressed. T2-weighted image (c), FLAIR (d,e) and T1-weighted image (f,g) with contrast enhancement show tumour of uneven structure with intense contrast accumulation and haemorrhagic/protein intracystic component
Supratentorial Tumours
Fig. 4.44a–f Dynamic of growth of AA of the right temporal area.
T2-weighted imaging (a) and T1-weighted imaging with contrast enhancement in axial (b) and coronal (c) projections detect wide operational defect in the right temporal lobe as a result of tumour excision 2 years prior. There are no data for the presence of tumour
363
that accumulate contrast. Control CT (d) and MRI (e,f) performed after 1 year reveal the tumour recurrence on the periphery of postsurgical cyst. The part of tumour that accumulates contrast medium is visualised clearly
364
Chapter 4
Fig. 4.45a–g AA of left temporal area. CT with contrast enhancement (a) reveals large
hypodense neoplasm. T2-weighted image (b), FLAIR (c) and T1-weighted image before (d) and with contrast enhancement (e) visualise the tumour of uneven structure with minimal contrast medium accumulation in central part. On DWI (f), the tumour’s periphery is hyperintense in comparison with central part. ADC map (g) is bright red from the central part of lesion (high values of ADC), and the peripheral part of the tumour is green (intermediate ADC values)
Supratentorial Tumours
365
Fig. 4.46a–c AA of frontotemporal area with lesion of genu of corpus callosum and spread to the opposite side. T2-weighted image (a) and T1-weighted image (b) reveal a tumour of uneven structure without
clear contours and massive affect on the left frontal and temporal lobes, and genu of corpus callosum. On DWI, an area of infiltration has hyperintense signal (c)
Fig. 4.47a–f AA of the left frontoparietal area (a 14-year-old pa-
tration is hyperintense on DWI (d). On the ADC map, astrocytoma has uneven structure (e). On the MR perfusion map (rCBV) the hyperperfusion foci are detected in the tumour (f)
tient). T2-weighted imaging (a), T1-weighted imaging before (b), and after (c) contrast enhancement detect a wide area of pathological MR signal and slight focal contrast accumulation tissue. An area of infil-
366
Chapter 4
Fig. 4.48a–c AA of the left circular gyrus with growth into the corpus callosum. CT without (a) and with contrast enhancement (b) reveals an initially hyperdense tumour with cyst in stroma and moderate additional contrast accumulation. Perfusion map (CBF) reveals intense increase of blood flow on the periphery of tumour (c arrowheads)
Supratentorial Tumours
Fig. 4.49a–i AA. Case1. On T2-weighted image tumour has a hyperintense MR signal; position of multivoxel MRS at the level of tumour’s location is seen (a). There are two different patterns of spectra in points of measurement : 1 increased Cho peak, decreased NAA peak, and small Lac–Lip complex (b); 2 more marked increase of Cho and decrease of NAA peaks is found, and there is a small Lac– Lip complex, which is a sign of tumour malignancy (c). Distribution
367
to concentration of metabolites on the colour maps is presented (d– f). Case 2. Tumour of the left temporoparietal region. T2-weighted image (d) and T1-weighted image with contrast enhancement (e) show mass lesion with heterogeneous structure. MR tractography (f) demonstrates the placement of cortical spinal tract, which is located medially to the tumour
368
Chapter 4
Fig. 4.50a–c Glioblastoma of right temporal lobe. CT before (a) and after (b,c) contrast enhancement reveals a small tumour with intense
contrast medium accumulation. There is a small area of necrosis in the centre of tumour. A hypodense area around tumour is oedema
Fig. 4.51a–c Glioblastoma of left temporoparietal area. CT after (a–c) contrast enhancement detects the large tumour with intense periph-
eral contrast accumulation and large central zone of necrosis. The ventricular system is dislocated; the hypodense area around tumour is oedema
Supratentorial Tumours
369
Fig. 4.52a–c Glioblastoma of frontal lobes and genu of corpus callosum. CT before (a) and after contrast enhancement (b,c) detects a large tumour with ring-shaped contrast accumulation and large zone of central necrosis
blood–brain barrier breakdown. Contrast accumulation in these cases is weak or altogether absent. However, this is an exception rather than the rule. Generally, MR signs of GB reflect pathological changes and demonstrate significant tumour heterogeneity. T1-weighted images reveal badly delimited volumetric formation with mixed (iso-, hypointense) signal and central area of necrosis, which usually has lowered signal in comparison with the rest of a tumour. The tumour’s characters on T2 and FLAIR scans also vary with the areas of hypo-, iso- and hyperintense signal from tumour stroma, necrotic focus, cysts and foci of haemorrhages. Even small tumours are often accompanied by the severe mass effect and oedema of white matter. Extensive mass effect and hypostasis of white substance often accompany small tumours. Borders of a tumour are indistinguishable with perifocal oedema; therefore, the peripheral area of GB is often called tumour oedema (Figs. 4.53–4.56). As in cases of AA, in GB tumour cells can be present outside an area of signal enhancement and perifocal oedema, revealed by MRI. GB spreads rapidly and widely alongside white matter tracts. The spreading to the opposite site through corpus callosum, anterior and posterior commissures is also typical; however, GB can also spread along internal and external capsules (Fig. 4.57). In cases of hemispheric lesion, GB sometimes spreads downward to chiasm–sellar area, cerebral peduncles and into posterior cranial fossa (Fig. 4.58). The separate tumour nodes that outwardly are distant from primary tumour but microscopically connected with it can be found in a patient with GB (Fig. 4.59). In the final stage, the tumour spreading into ependyma and the subarachnoid space of brain and spinal cord can be observed (Fig. 4.60). Haemorrhages of various sizes can be visualised in GB. The MR signal
in T1 sequences is increased in cases of subacute haemorrhage (Fig. 4.61). In some cases, intracranial haematoma can blur the neoplasm border (Fig. 4.62). MRI with contrast enhancement is better than CT for visualisation of ventricular system or pia or dura matter invasion in cases of tumour infiltration to the surface (Figs. 4.63, 4.64). The typical GB is a tumour of heterogeneous structure with peripheral (ring shaped) contrast enhancement, severe perifocal oedema, arteriovenous shunts, intratumoral haemorrhages, typical corpus callosum involvement and rapid growth in elderly patients, but in our practice we encounter cases with atypical clinical course and MRI characteristics (Figs. 4.65–4.68). The majority of GB considerably, albeit heterogeneously, accumulate contrast on MRI with contrast enhancement. The use of increased doses of contrast and delay of MRI investigation increases the visualisation of the infiltrative part of neoplasm entering the surrounding brain tissue (Fig. 4.69). Due to the often high vascularisation of these tumours, MR-scans (especially on T2 sequences) can demonstrate the tumour vessels in the form of coiled, elongated areas with the phenomenon of signal loss due to circulating blood (Fig. 4.70). Because of rich tumour vascularisation, in some cases it is necessary to perform direct angiography for clarification of surgery tactics (Figs. 4.71–4.73). Multiple GB are observed in 5% of cases; in these situations they can not be distinguished from metastases without paracentetic biopsy (Fig. 4.74). Even use of high-resolution MRI does not visualise the interrelation of separate tumour nodes. The presence of neoplasm in different brain hemispheres and a combination of supra- and subtentorial lesions is, in our opinion, one of the arguments in favour of an existing hy-
370
Fig. 4.53a–e Glioblastoma of the left posterior frontal area. CT be-
fore (a) and after (b) contrast enhancement detects tumour with intense contrast accumulation. An area of central necrosis does not accumulate contrast medium. Hypodense area around tumour is oedema. T2-weighted imaging (c), T1-weighted imaging before (d) and with (e) contrast enhancement reveal the tumour of uneven
Chapter 4
structure. The perifocal oedema is equally hyperintense with an area of central necrosis on T2-weighted imaging. T1-weighted imaging demonstrates the ring-shaped contrast accumulation typical for glioblastoma. The internal and external contours of the contrast accumulating part of tumour are uneven
Supratentorial Tumours
371 Fig. 4.54a–e Glioblastoma. Series CT demonstrates that tumour intensively accumulates contrast medium in the shape of a ring (a). MRI: T2-weighted image (b) and T1-weighted image (c) reveal an area of pathological change of MR signal intensity—the tumour tissue with central necrosis (hyperintense signal on T2-weighted image) is surrounded by prominent perifocal oedema. The neoplasm spread is better evaluated on axial (d) and coronal (e) images after contrast enhancement
372
Chapter 4
Fig. 4.55a–c Glioblastoma. T2-weighted image (a) and T1-weighted image (b) demonstrate wide area of pathological change of MR signal
intensity—the tumour with central solid necrosis. Tumour moderately accumulates contrast (c) in the form of a “ring”
Fig. 4.56a–c Glioblastoma. T2-weighted imaging (a) and T1-weighted imaging before (b) and after (c) contrast enhancement demonstrate the tumour spread widely, which has infiltrative and necrotic sections. There is intense peritumoral oedema and mass effect of the ventricular system. There are haemorrhagic foci in the tumour stroma (b)
Supratentorial Tumours
373
Fig. 4.57a–c Glioblastoma (variants of location) of corpus callosum. MRI with contrast enhancement: anterior part (a), middle part (b) and splenium (c)
Fig. 4.58a–c Glioblastoma of the left basal ganglia with growth into midbrain and chiasmal–sellar area. T1-weighted image in sagittal (a), axial (b) and coronal (c) projections with contrast enhancement Fig. 4.59a,b Glioblastoma (variants of
contrast accumulation). T1-weighted image with contrast enhancement: the first observation (a), the second observation (b). The multifocal type of neoplasm contrast accumulation is detected
374
Fig. 4.60a–c Intraventricular glioblastoma. T2-weighted image (a)
Chapter 4
and T1-weighted image (b) reveal tumour of uneven structure (with haemorrhages). Tumour fills the lumen of the third ventricle and an-
terior horns of lateral ventricles and spreads into the fourth ventricle. Contrast enhancement (c) improves the visualisation of tumour spread
Fig. 4.61a–c Glioblastoma of right temporal area. T2-weighted imaging (a) and T1-weighted imaging (b) detect tumour of uneven structure with acute (dark signal on T2) and subacute (high signal
on T1) haemorrhages. There is a wide peritumoral oedema. After contrast enhancement (c), the infiltrative part of tumour intensively accumulates contrast
Supratentorial Tumours
375
Fig. 4.62a–c Glioblastoma of the right parietal area with large intratumoral haemorrhage. FLAIR (a), T1-weighted image (b) and T2-weighted image (c) demonstrate the hyperintense MR signal from tumour on all sequences (subacute haematoma). The tumour tissue is visualised laterally to the haemorrhage
Fig. 4.63a–c Glioblastoma of left parieto-occipital area. a CT with contrast enhancement. The large mass lesion of heterogeneous structure with hypodense centre and intense contrast accumulation in the shape of a ring is detected. MRI: T1-weighted images with contrast
enhancement (b). An area of tumour invasion of the wall of adjacent lateral ventricle and tumour spread along ependyma are visualised additionally. Twenty-eight hours after the operation: MRI with contrast enhancement (c) detects that a small tumour remains (arrows)
376
Fig. 4.64a–c Glioblastoma of the right temporal area. CT (a) with
contrast enhancement detects mass lesion of heterogeneous structure with hypodense centre and intense contrast accumulation in the shape of a ring. T2-weighted image (b) and T1-weighted image (c)
Chapter 4
with contrast enhancement additionally shows an area of tumour invasion of wall of adjacent lateral ventricle and tumour’s spreading along ependyma
Fig. 4.65a–c Glioblastoma. T2-weighted imaging (a) and T1-weighted imaging (b) detect round tumour located in the projection of left pos-
terior frontal area. The tumour is surrounded by the prominent oedema. Contrast accumulation is intense and homogeneous (c)
Supratentorial Tumours
Fig. 4.66a–c Glioblastoma of occipital lobe. T2-weighted image (a) and T1-weighted image (b) with contrast enhancement. The mass lesion with intense contrast accumulation is detected. The spread of
377
tumour into the splenium of corpus callosum is clearly visualised. CT with contrast enhancement: tumour tissue is hyperdense due to contrast accumulation (c)
Fig. 4.67a–c Glioblastoma of corpus callosum and medial parts of both frontal lobes, with prevalence in the left. T2-weighted image (a) and T1-weighted image before (b) and after (c) contrast enhancement. The mass lesion with hyperintense MR signal on T2-weighted imaging and isointense on T1-weighted imaging is observed
Fig. 4.68a–c Glioblastoma of the left frontal area. T1-weighted imaging with contrast enhancement (a) and T2-weighted imaging (b,c) detect
a tumour—an area of pathological change of MR signal intensity with presence of round formation, with surrounding oedema. There are no signs of contrast accumulation in the tumour
378
Chapter 4 Fig. 4.69a–f Dynamics of contrast me-
dium accumulation in glioblastoma of the left temporal area. T2-weighted image (a) and T1-weighted images (b,c) after 5-min double dose of contrast enhancement. The tumour of uneven structure with central necrosis, ring-shaped contrast, accumulation and intense peritumoral oedema is visualised. After 20 min (d): increase of an area of pathological contrast accumulation due to widening of external as well as internal borders; also, the merging of separate foci of contrast accumulation with the main tumour’s mass is visualised. Repeated MRI 1 h later: spread of an area of contrast accumulation continues (e). MRI 24 h later (f) detects the remaining contrast accumulation in an area of oedema/ tumour infiltration and in the zone of central necrosis. The initial “ring” became hypointense in comparison with oedema and central necrosis
Supratentorial Tumours
Fig. 4.70a–f Glioblastoma of right occipital parietal area. CT (a) shows the tumour of heterogeneous structure, with peripheral contrast accumulation. T2-weighted image (b) and T1-weighted image (c,d) with contrast enhancement detect a large neoplasm with multiple arteriovenous shunts (coiled hypointense areas). MRA in 3D TOF technique demonstrates the vascular net of glioblastoma with main supply from branches of right PCA and distal branches of right MCA (e,f)
379
380
Chapter 4
Fig. 4.71a–g Glioblastoma. a CT. An intra-axial tumour with large central necrosis and
solid component; compressing of brain ventricles is detected at the level of lateral ventricles in the right posterior frontoparietal area. b,c Cerebral AG. The rich blood supply of the tumour with the presence of arteriovenous shunts (arrows) and drainage into deep brain veins and superior sagittal sinus is visualised. MRI: the large tumour of heterogeneous structure is revealed on T2-weighted imaging (d) and T1-weighted imaging (e). The necrotic area is hyperintense on T2-weighted imaging. Arrow points to arteriovenous shunts; the intense contrast accumulation of dense part of neoplasm is observed in coronal (f) and axial (g) projection on T1-weighted images after contrast enhancement
Supratentorial Tumours
381
Fig. 4.72a–f Glioblastoma in the projection of thalamus with sub-
tentorial growth. a CT with contrast enhancement. The intra-axial tumour of solid structure with laterally located cyst is detected at the level of triangles of bodies of the lateral ventricles. The right lateral ventricle is compressed. T2-weighted imaging (b) and T1-weighted imaging with contrast enhancement (c) improve the visualisation of glioblastoma spreading and structure. AG of right carotid (d) and left vertebral (e,f) arteries. The rich blood supply of tumour from meningial branches of ICA and branches of PCA with the presence of arteriovenous shunts and drainage into deep brain veins and direct sinus is demonstrated
382
Chapter 4
Fig. 4.73a–f Glioblastoma of the left occipitoparietal area. T2-weighted image (a–c), demonstrate the widespread tumour with hyperintense
foci of subacute haemorrhages. Angiography of left carotid artery (d–f) reveals the rich blood supply of tumour from MCA with the presence of arteriovenous shunts
Fig. 4.74a–c Primary multiple glioblastoma. T2-weighted image (a) and T1-weighted image (b,c) with contrast enhancement. The three separated tumour nodes affecting both right and left hemispheres are detected
Supratentorial Tumours
383
pothesis about the notion of glial brain disease as a single entity (Figs. 4.75, 4.76). The gradual transformation of LGA into AA and then to GB is a well-known fact. In such observations, it is possible to simultaneously visualise within the same tumour the density changes (on CT) and MR signal changes (on MRI), typical for separate nosological forms of glioma (Fig. 4.77), a combination of different forms of glioma (Fig. 4.78) or transformation of changes on follow-up scans (Fig. 4.79). MR perfusion or CT demonstrates the marked increase of the main haemodynamic indicators in the infiltrative GB, which are virtually not observed in AA. In the central necrotic parts of GB, the blood flow is decreased regardless of necrosis density (Figs. 4.80, 4.81). More heterogeneity for GB than for astrocytoma and AA is typical on DWI. In cases of ordinary GB structure, the central part (necrosis) usually has decreased MR signal and high ADC value. The peripheral infiltrative part of the tumour is characterised by moderately hyperintense MR signal and rela-
tively high ADC value (Gillard et al. 2005) (Figs. 4.82, 4.83). However, the ADC digital values calculated in GB and solid (contrast accumulating) areas of AA are widely overlapping, which does not enable determination of tumour type solely on the basis of DWI data. The average value of ADC in GB stroma that accumulates contrast is about substance 1.19 ± 0.29 mm2/s, and has an index of anisotropy of 0.06. The destructive tumour growth in brain tissue leads to total disintegration and destruction of neural tracts in white matter at the site of GB; these changes are revealed by MR tractography (Fig. 4.84). This is an important point that distinguishes GB from solitary metastasis, for which tract dislocation is typical. Single-voxel 1H MRS in the majority of cases demonstrates the presence of a large Lip–Lac complex, with underlying marked reduction of peaks from other brain tissue metabolites. GB MRS signs are not distinguished from those of any other tumour or abscess with an area of disintegration. The increase of the Cho peak and marked decrease of the NAA peak are observed in cases of atypical solid tumour
Fig. 4.75a–f Primary multiple glioblastoma. T2-weighted image (a), T1-weighted image before (b) and after (c,d) contrast enhancement and FLAIR (e) shows two tumour nodes located in different hemi-
spheres. The presence of central necrosis even in the small tumour node in the left parietal lobe is detected. Infiltrative part of tumour is slightly hyperintense on DWI (f)
384
Chapter 4
Fig. 4.76a–c Primary multiple glioblastoma. T2-weighted image (a,b) and T1-weighted image (c) demonstrate the multiple mass lesions, located supratentorially as well as subtentorially
Fig. 4.77a–c Glioblastoma of the frontal-temporal area. T1-weighted image with contrast enhancement (a) and T2-weighted image (b,c)
reveal widespread tumour with contrast-accumulating (the frontal lobe) section and non-contrast-enhancing (the temporal lobe) section. The mass effect on adjacent brain structures is prominent
Fig. 4.78a–c Glioblastoma of the left temporoparietal area and low-malignant astrocytoma in the right frontal lobe. Axial T2-weighted imaging (a) and T1-weighted imaging with contrast enhancement (b,c) detect two tumour nodes with different MR features
Supratentorial Tumours
385
Fig. 4.79a–g Dynamics of growth of glioblastoma of circular gyrus. CT before (a) and
after (b) contrast enhancement, FLAIR (c) and T2-weighted imaging (d) reveal tumour of a solid structure without perifocal oedema and with homogeneous contrast accumulation. One month later CT (e) and MRI (f,g) detect intense tumour progression with a formation of central necrosis and ring-shaped contrast accumulation
386
Chapter 4 Fig. 4.80a,b Glioblastoma of corpus cal-
losum. T1-weighted image (a) with contrast enhancement reveals tumour of uneven structure with intense contrast accumulation. MR perfusion (rCBV): the increase of blood flow into tumour tissue (b arrows)
Fig. 4.81a–c Glioblastoma of the right temporal area. a CT with contrast enhancement reveals the large tumour with ring-shaped contrast accumulation. CT perfusion reveals the intense increase of CBV and flow on CBV (b) and CBF (c) maps
Supratentorial Tumours
387
Fig. 4.82a–c Glioblastoma in the shape of a butterfly. DWI (b = 1000) demonstrates lesion with hyperintense central necrotic part (a). The neoplasm is characterised by uneven changes of diffusion coefficient
in infiltrative and necrotic parts (b) on the ADC map. MRI with contrast enhancement (c) demonstrates that bilateral spreading is typical for glioblastoma
Fig. 4.83a–c Glioblastoma of the left frontotemporal area. T2weighted imaging (a), DWI (b) and T1-weighted imaging with contrast enhancement (c) detect tumour with central necrosis and the
peripheral part that accumulates contrast. On DWI the signal from central necrosis is hypointense; from infiltrative section, it is slightly hyperintense
388
Chapter 4
Fig. 4.84a–e Glioblastoma of the left temporoparietal region. On T2-weighted image (a) and T1-weighted image (b) with CE a large tumour
with central necrosis is observed. Tumour destroys white matter tracts in the affected region, which is well demonstrated on FA map (c) and 3D tractography (d,e)
structure. The use of multivoxel MRS, with the possibility of positioning the area of interest in any site of the selected scan, provides new potential in the evaluation of the biochemical state of tumour tissue, perifocal area and surrounding oedema (Gillard et al. 2005; Stadlbauer et al. 2007) (Fig. 4.85). Superficial GB location, especially close to functionally significant cortical areas, makes obligatory the use of modern 3D modelling and navigational technologies in combination with fMRI for the best possible preoperational planning of surgical access. On one hand, this provides the neurosurgeon the preliminary knowledge of superficial reference points (convex brain veins), and on the other hand, the neurosurgeon realises the anatomical interrelation between tumour and functional brain centres (Tharin et al 2007). Taken together, this enables achieving maximum possible tumour resection with minimal neurological deficit (Fig. 4.86). This should be taken into account in the process of planning the radiotherapy for intracranial tumours. Gliosarcoma (GS) is considered a separate variant; it is a simultaneous combination of GB and angiosarcoma (or fib-
rosarcoma). Macroscopically, GS is a solid tumour with central necrosis. Sarcomatous parts are clearly separated from neighbouring brain tissue, and at the same time the astrocytic component has soft structure and is poorly separated from surrounding structures. GS histological diagnosis depends on identification of glial and mesenchymal tumour components; the latter is similar to typical fibrosarcoma or malignant fibrous histiocytoma (Matsko and Korshunov 1998). The infiltrative component of GS is almost always GB. Sarcomatous transformation is observed in less than 2% of all GB cases (Kleihues and Cavenee 2000). The majority of patients with GS are people 50–70 years old. The survival rate is similar to patients with GB. In 15– 30% of cases, GS has extracranial metastases. Metastases in visceral organs are also observed. The distant metastases do not influence the clinical prognosis, because the intracranial process is the main reason for death. The superficial location and spreading with possible dural invasion is typical for GS. The temporal lobe is affected more frequently.
Supratentorial Tumours
389
Fig. 4.85a–f Glioblastoma. T1-weighted imaging with CE (a) reveals the lesion that heterogeneously accumulates contrast medium in ring-shape form. On T2-weighted image (b), tumour has a hyperintense MR signal; the position of multivoxel MRS at the level of
tumour is presented (b). Spectra (c) shows increased Cho peak and Lac–Lip complex, with reduce peaks of other metabolites. Distribution to concentrations of metabolites on colour maps is seen (d–f)
GS CT signs are variable. The tumour may resemble meningioma or GB. Usually GS is less homogeneous than meningioma, it has no wide fastening to dura mater and it is always surrounded by perifocal oedema. Marked heterogeneity or uneven, ring-shaped contrast enhancement are typical for GS. T1- and T2-weighed MR images demonstrate non-homogeneous tumour with frequent necrosis and haemorrhages. Signal increase is observed after contrast administration; however, as a rule its structure on MRI has a heterogeneous character (Figs. 4.87, 4.88). Nevertheless, on the basis of MR characteristics, it is impossible to differentiate GS from GB. The role of hyperventilation with contrast enhancement in MRI diagnosis of glial brain tumours. The influence of hyperventilation (hypocapnia) on a brain–blood flow and level of tumour visualisation began to be intensively studied with cerebral angiography at the end of the 1960s. It was noted that tumour vessels were better revealed in cases of lesser pCO2. It was found that lessening of pCO2 in blood decreases blood flow in patients with normal circulation due to increase of cerebrovascular resistance. The controlled (with the help of
special device) ventilation and moderate spontaneous hyperventilation with рСО2 of 4–4.67 kPa were used for pCO2 decrease. We chose the spontaneous hyperventilation as the simplest method, which does not require special amagnetic equipment for supplying a respiratory mix. CT, before and after contrast administration, was used for selection of patients with glial tumours, without hypertension or with minimal changes on the eye fundus. The hyperventilation was performed in 2 min, at the rate of 30–40 breaths per minute [that means the mean blood flow velocity (MBV) was about 150–200%] directly before contrast administration. The relative contrasting of tumour image before and after the test was assessed according to the standard technique. The results were compared with MRI data with contrast enhancement performed earlier (but not less than 48 h before the hyperventilation test). In total, we examined 29 patients with glial brain tumours. Results of research demonstrated that hyperventilation with our technique does not improve tissue visualisation in patients with benign astrocytoma (i.e. contrast accumulation in
390
Chapter 4
Fig. 4.86a–f Variants of 3D reconstruction of hemispheric surface of brain in cases of virtual approach to the tumour in patient with glio-
blastoma of parietal area. The reference points—convex brain veins—are clearly visible on 3D MRI image. The tumour intensively accumulates contrast (a–f)
Fig. 4.87a–c Gliosarcoma. MRI demonstrates the heterogeneous
mass lesion affecting the right temporal lobe. On T2-weighted image (a) the tumour borders blended with perifocal oedema (which also is hyperintense) are seen. T1-weighted imaging (b) detects mainly only
mass effect, with the dislocation of neighbouring brain tissue. The visualisation of the process spreading is possible only with the use of contrast enhancement (c)
Supratentorial Tumours
Fig. 4.88a–f Gliosarcoma of the right frontal lobe. T1-weighted image (a), T2-weighted image (b) and T1-weighted images, and after contrast administration in three projections (c–e). The large neo-
391
plasm, hypointense on T2-weighted image and with intense contrast accumulation, is detected. On FLAIR (f) the tumour is also hypointense. The perifocal oedema is hyperintense
392
Chapter 4
tumour was not achieved), which can be related to the absence of tumour vascular net that can react to the decrease of pCO2 concentration in blood. In cases of ependymomal AA and GB, hyperventilation markedly improved tumour tissue visualisation (the difference in contrast accumulation in some observations reached 30%), which was characterised by the increase of relative neoplasm contrasting (Fig. 4.89, 4.90). In addition, the mentioned expansion of an area of signal increase in AA and GB after the test supports the theory of the presence of a “transitional” area of tumour invasion with subcompensated damage of the blood–brain barrier around the region of contrast accumulation (after standard contrast enhancement). Pilocytic astrocytoma (PA) is a subtype of astrocytoma. The age of affected patients, location and clinical prognosis for PA are substantially different from those for diffuse infiltrative fibrillary astrocytoma. This type of neoplasm consists of bipolar astrocytes with long processes and high concentration of glial Rosenthal’s fibres in the cytoplasm (Burger et al. 2000). The incidence of PA is about only 5–10% of all brain gliomas; however, they make up to a third of all glial tumours in children; among them, in supratentorial areas the most frequently observed tumours are located in the projection of the bottom of the third ventricle and chiasm, whereas among subtentorial locations, the most frequent are cerebellum hemispheres. The majority of PA in cerebellum are diagnosed in the first two decades of life, and their incidence peaks at the age of 10 years. Hemispheric PA are revealed 10 years later, with peak at the age of 20 years. Three quarters of optic tract tumours
are observed in patients before 12 years of age. PA is seldom diagnosed in adults before 40–50 years of age. Macroscopically, PA is a formation whose outward appearance depends on tumour location. Cerebellar PA is a clearly outlined formation that can have a large cyst with parietal node. Optic-chiasmal hypothalamic PA are also clearly outlined with nodal shape; however, on the microscopic level they can infiltrate walls and the bottom of the third ventricle. Mitotic activity in them is absent. Although PA often form cysts, tumour necrosis is not observed. PA is a slowly growing tumour whose clinical course and symptoms depend on location. In general, the postoperative survival at 5 years is close to 86–100%, at 10 years it is about 83% and at 20 years, 70%. The survival of patients with total resection is close to 100%. Even patients with incomplete resection of hypothalamic-optic-chiasmal tumour have long survival (Komotar et al. 2004). Life duration for 5 and 10 years in this group is 93 and 73%, respectively. On CT scans, PA usually has a round or oval formation and is well delimited with hypo- or isodense characteristics. Calcifications are observed in 10–20% of all PA cases (Osborn 2004). Contrast enhancement varies. Some tumours with solid structure are characterised by marked and homogeneous contrast accumulation, while the others have parietal node in big cysts (Figs. 4.91, 4.92). Obstructive hydrocephaly is observed in cases of PA located in the (a worm-like projection) cerebellum and fourth ventricle. The solid part of PA usually has hypo- or isointense signal on MRI T1-weighted imaging, whereas on T2-weighted imag-
Fig. 4.89a–c AA. T1-weighted imaging detects the tumour of right frontotemporal area and with spread through corpus callosum into left hemisphere (a). Contrast enhancement demonstrates the uneven
structure of tumour (b). The repeated MRI with contrast enhancement (c) performed after 2 days with hyperventilation reveals the increase of the area of pathological contrast accumulation (arrows)
Supratentorial Tumours
393
Fig. 4.90a,b Glioblastoma of the left temporoparietal area. MRI with contrast enhancement shows the neoplasm that accumulates contrast
in the left parietal area (a). MRI with 2-min hyperventilation performed after contrast enhancement (b) detects the increase of an area and intensity of contrast accumulation (arrows)
Fig. 4.91a–c PA of left basal ganglia. Axial CT (a–c) detects cystic mass lesion with peripheral solid tumour node
394
Chapter 4
Fig. 4.92a–e PA (a 14-year-old patient). T2-weighted imaging (a) and T1-weighted imaging (b) detect tumour of relatively homogeneous structure, without perifocal oedema in the projection of basal ganglia. The contrast accumulation (c,d) in tumour is heterogeneous; it mainly reveals solid structure. On axial CT (e), an area of contrast accumulation of solid part of neoplasm is somewhat lesser than on MRI
Fig. 4.93a–c PA of the left temporal lobe (a 11-year-old child). T1-weighted image before (a) and with contrast enhancement (b,c). The tu-
mour of mixed structure is visualised in medial parts of the left temporal lobe with contrast accumulation only in solid areas
Supratentorial Tumours
ing, this part of the tumour looks hyperintense. The cystic part of the neoplasm has high MRI signal on T2 and FLAIR. Administration of gadolinium-containing agents leads to mainly heterogeneous and pronounced intensive signal enhancement from the solid part of the tumour (Arslanoglu et al. 2003). The walls of tumour cyst in some cases can also accumulate contrast (Fig. 4.93). Cases of malignant transformation or tumour dissemination on the pia and dura matter are exceptions, although they are described in the literature and were observed in our series (Fig. 4.94). MRS detects the increase of the Cho peak, and decrease of NAA and lactate peaks. It is considered that MRS does not reflect the true biological behaviour of a tumour and resembles the attributes observed in cases of malignant astrocytoma (Hwang et al. 1999). In PET examinations, the tumour is characterised by the increase of a metabolism of 18F-fluorodeoxyglucose; however, that (as well as in the case of MRS) does not reflect the histological benign character of tumour structure. Differential diagnosis with medulloblastoma, ependymoma and hemangioblastoma is required if PA is located in posterior cranial fossa. Supratentorial tumours can have similar characteristics with ganglioma, atypical teratoma and acute pseudotumoros demyelination. Pleomorphic xanthoastrocytoma (pleoASC) is a rare tumour (less than 1% of all cases of astrocytoma), which represents histological and biologically delimited subtype of astrocytoma (Matsko and Korshunov 1998). It is located in cortex and neighbouring white matter. It can contain large cysts. In 50% of cases, the combination of cysts and parietal tumour node is observed. It can also have only solid infiltrative components. Histologically, the tumour is characterised by marked nuclei polymorphism, with the presence of giant nuclear and multinuclear “cell monsters”. PleoASC is almost exclusively diagnosed in young patients. The typical location (up to 98%) is a supratentorial one, with the most preferred site being the temporal lobe.
395
The solid part of the neoplasm has mixed density (hypo-, iso- and hyper-) on CT, and the cyst is hypodense. Oedema, calcifications, haemorrhage and bone erosion are not characteristic features for tumour growth and are seldom observed. The marked, sometimes heterogeneous, contrast accumulation is typical for this tumour. MRI better reveals the subtypes of a macroscopic structure of a neoplasm. Solid parts of PleoASC are hypo- or isointense in comparison with grey matter. Cyst component as a rule does not differ from CSF signal in subarachnoid spaces. Oedema is not typical for tumour growth. The infiltrative (solid) part and surrounding cyst(s) are better differentiated with the FLAIR sequence. Contrast accumulation is moderate, with relatively clear demarcation from brain tissue. The contrasting of neighbouring brain matters (the so-called dural tail) is a sign of their infiltration. Contrast enhancement of solid (mural) node usually reaches the cortex surface (Figs. 4.95, 4.96). The cases with the presence of calcifications in tumour stroma are described in literature (Jones and Patterson 1997). The differential diagnosis should usually be performed between gangliocytoma, PA, dysembryoplastic neuroepithelial tumours, oligodendroglioma and LGA, more rarely with meningioma in cases in which a cystic component is absent. Subependymal giant cell astrocytoma macroscopically looks nodal, located inside the lateral ventricles, more frequently close to the interventricular the foramen of Monroe. This tumour originates from astrocytes of the subependymal area and is typical for the patients with tuberous sclerosis (Bourneville’s disease). Microscopically, it consists of large cells with plentiful eosinophilic cytoplasm and eccentrically located nuclei. Slow growth is typical for this tumour; it reaches sizes of 2–3 cm. Usually, it causes occlusion hydrocephalus. This tumour is observed in up to 15% of all patients with tuberos sclerosis. It makes up 1.4% of all brain tumours in children. A combination of intracranial signs and those of Bourneville’s disease is typical (Cuccia et al. 2003).
Fig. 4.94a–c Subarachnoid spreading of PA. CT with contrast enhancement (a–c). A tumour structure with contrast accumulation in the region of brain cisterns is detected. The ventricular system is dilated due to hydrocephalus
396
Chapter 4
Fig. 4.95a–f Pleomorphic xanthoastrocytoma of left occipitoparietal area. CT with contrast enhancement (a–c) detects a tumour with cystic and solid components in the projection of left occipital area. T2-weighted imaging (d), T1-weighted imaging before (e) and after
(f) contrast enhancement reveal a tumour of uneven structure with cysts and a big solid node (with intense contrast accumulation). One cyst is protruded into the lateral ventricle
Fig. 4.96a–c Pleomorphic xanthoastrocytoma of left temporal area. CT (a,b) with contrast enhancement detects a tumour with heterogeneous contrast accumulation in the projection of medial parts of
the left temporal area. T2-weighted image (c) demonstrates a tumour of uneven structure with small cysts and infiltrative growth into left cerebral peduncle
Supratentorial Tumours
397
The structural heterogeneity of the tumour is reflected on CT and MRI (Figs. 4.97, 4.98). Calcifications can be found in the structure of a tumour. The mixed iso- and hyperintense signal is revealed on T1 and T2 sequences. The dilatation of lateral ventricles, and the sign of occlusion of interventricular foramen of Monroe, sometimes accompanied by perifocal oedema, can be better detected in FLAIR sequences. Contrast enhancement reveals moderate and heterogeneous contrast accumulation in the tumour tissue. Differential diagnosis should be performed between choroid papilloma, astrocytoma, subependymoma, neurocytoma and supratentorial primitive neuroectodermal tumour.
4.3.2 Oligodendroglioma
Fig. 4.97a–f Subependymal giant cell astrocytoma. CT with contrast enhancement (a,b). The hyperdense mass lesion with small calcifications is detected in the projection of anterior horn of the right lateral ventricle. In addition, there are multiple calcifications with subependymal and paraventricular locations. The tumour signal characteristics are close to the brain tissue on T2-weighted
image (c,d). The tumour compression to the foramen of Monroe causes the hydrocephalic dilatation of lateral ventricle bodies. The tumour is isointense in comparison with brain tissue on T1-weighted images without contrast enhancement (e,f). Calcifications are not visualised on this sequence
Oligodendroglioma (ODG) is a rather rare type of glioma. Moreover, “pure” ODG is an even rarer phenomenon. Mainly, mixed gliomas (oligoastrocytomas) are observed. The tumour originates from a specific type of glial cell, oligodendrocytes, and its incidence is about 2–10% of all primary intracranial tumours and 5–25% of all gliomas. ODG is an adult tumour. The ratio of adult patients to child patients is 8:1. The incidence peak is from 35 to 45 years old. The main clinical symptom is epileptic seizures. The overwhelming majority of ODG are slowly growing, benign, non-capsulated infiltrative tumours
398
Chapter 4
Fig. 4.98a–d Subependymal giant cell astrocytoma. Axial CT with contrast enhancement
(a) detects the hyperdense mass lesion in the projection of the anterior horn of the right lateral ventricle. The small calcifications are revealed on its periphery and in the left subependymal region. The tumour signal characteristics are close to those of unaffected brain tissue on T2-weighted image (b). The tumour’s spread into the foramen of Monroe causes the hydrocephalic dilatation of lateral ventricle bodies. The tumour has isointense signal with white matter on T1-weighted image before CE (c) and homogeneous accumulation of contrast medium after CE (d)
of white matter with mainly paraventricular locations. The foci of cystic degeneration are typical for this tumour, but necrosis and haemorrhages are not observed in cases of benign forms. Malignant transformation declares itself by cytotic atypia, mitoses and proliferation of vascular endothelium. Microscopically, the tumour consists of monomorphic cells with even distribution on different sites. Under small magnification the tumour has the characteristic structure of honeycombs (Matsko and Korshunov 1998). Eighty-five percent of all tumours are supratentorial ones, and the frontal lobe is more frequently affected. Primary ODG can spread to ventricles; however, ventricular arrangement is a rare phenomenon. In our studies, we examined 85 patients and in all cases, the tumours were of relatively large size and distribution; in one case it even exceeded 5 cm in size. ODG is the most frequently calcified tumour among all intracranial neoplasms. The presence of nodular or lumpy calcifications is revealed in 70–90% (Fig. 4.99). The tumour has mixed density. Two thirds of all ODG accumulate contrast.
MRI reveals a tumour with mixed hypo-and isointensity on T1-weighted images, and with foci of hyperintensity on T2weighted scans. Contrast enhancement is moderate and heterogeneous. Although MRI is a less sensitive method than CT in detection of tumour calcifications, it is, however, superior in diagnosis of the tumour distribution (Figs. 4.100, 4.101). It is better to use T2 and FLAIR sequences than T1-weighted imaging. Contrast enhancement of ODG on MRI is uneven, and it is observed in about 50% of cases and is more visible in cases of malignant transformation (Figs. 4.102, 4.103). MRS detects the increase of the Cho peak and decrease of the NAA peak. MRI and CT perfusion examinations demonstrate the presence of hyperperfusion foci within the structure of histologically benign ODG, similar to malignant astrocytoma (Lev 2004). PET with the use of 18F-fluorodeoxyglucose outlines the parameters of contrast accumulation, similar to those of white matter. Methionine-11 helps to make a differential diagnosis between benign and malignant forms of neoplasm.
Supratentorial Tumours
399
Fig. 4.99a–c Oligodendroglioma. Different types of calcifications in the structure of tumour
Fig. 4.100a–c Oligodendroglioma of left frontal area with the affection of corpus callosum. T2-weighted image (a), T1-weighted image before (b) and after (c) contrast enhancement demonstrate a large tumour. Calcifications are hypointense on T2-weighted image. Contrast accumulation is moderate and uneven
400
Chapter 4
Fig. 4.101a–c Oligodendroglioma of left posterior frontotemporal area. T2-weighted image (a), T1-weighted image (b), and CT (c) demonstrate a large tumour. Contrast enhancement is slight on CT. Calcified parts of tumour are hyperdense on CT. Their visualisation on MRI is complicated
Fig. 4.102a–c Oligodendroglioma of the right frontal-parietal area. T2-weighted imaging (a), and T1-weighted imaging before (b) and after
(c) contrast enhancement detects large tumour with intense contrast accumulation. Perifocal oedema is minimal
Supratentorial Tumours
401
Fig. 4.103a–c Oligodendroglioma of the left frontal area with involvement of the opposite side. T1-weighted imaging detects large tumour with intense contrast accumulation
In clinical practice, atypical radiological features of ODG without calcifications and contrast enhancement can be observed (Figs. 4.104, 4.105). The development of malignant ODG can originate from the tissue of benign tumour; also, a primary tumour can be malignant from the beginning. With the increase of anaplasia (cysts necroses, haemorrhages appear in the tumour structure), tumour heterogeneity grows, the perifocal oedema and brain dislocation increase and marked contrast accumulation observed (Figs. 4.106–4.108). With the absence of calcifications, it is really difficult to make differential diagnosis of ODG from astrocytoma and ganglioma. Less often, it is required to differentiate the tu-
mour from DNET, pleoASC, ischaemic stroke and local lobar herpetic encephalitis.
4.3.3 Ependymomas Ependymomas (EP) are tumours that originate from cells of ependyma, and they mainly have intraventricular or paraventricular locations (ventricular system, more often lateral ventricles, spinal cord and final thread). The extraventricular location (ectopic EP) is a rare albeit possible phenomenon. Recently, researchers began to consider EP as a separate his-
Fig. 4.104a–c Oligodendroglioma. T2-weighted image (a) and T1-weighted image (b) demonstrate tumour of heterogeneous structure which affects temporal and partly parietal lobes. Mass effect is not expressed. It is not possible to differentiate perifocal oedema from the tumour’s tissue. The tumour is hypodense on CT; calcifications are absent (c)
402
Fig. 4.105a–f Oligodendroglioma of right frontal area. T2-weighted imaging (a), FLAIR (b) and T1-weighted imaging before (c) and after (d) contrast enhancement detect the small tumour without contrast
Chapter 4
medium accumulation. On DWI (e) the neoplasm is slightly different from white matter. MRS reveals the decrease of NAA and minimal Lac (f) peaks
Supratentorial Tumours
Fig. 4.106a–f Anaplastic oligodendroglioma of left frontal area with
the affection of corpus callosum. CT without (a,b) and after (c) contrast enhancement detects a tumour of uneven structure with cysts and horizontal level inside. Solid areas of tumour intensively accumulate contrast. T2-weighted imaging (d) and T1-weighted imaging
403
before (e) and after (f) contrast enhancement better shows the tumour components both with and without contrast medium accumulation. The phenomenon of sedimentation inside tumoral cyst is detected
404
Fig. 4.107a–f Anaplastic oligodendroglioma of left frontal area with
the affection of corpus callosum and spreading into the opposite side. Cerebral AG reveals the tiny tumoral vascular net with blood supply from branches of left ACA (a,b); the latter is dislocated to the right. CT with contrast enhancement (c) shows a tumour of mixed struc-
Chapter 4
ture with a large cystic part. The ventricular system is compressed and dislocated to the right. MRI: T2-weighted imaging (d), FLAIR (e) and T1-weighted imaging (f) additionally clarify the neoplasm spreading into the corpus callosum and right frontal lobe. The phenomenon of sedimentation inside the tumoral cyst is detected
Supratentorial Tumours
Fig. 4.108a–h Dynamics of malignant transformation of benign oligodendroglioma of the left frontotemporal area. CT with contrast enhancement (a), T2-weighted imaging (b) and T1-weighted imaging after contrast enhancement (c) detect infiltrative tumour with calcifications and small foci of contrast accumulation. Diagnosis of
405
oligodendroglioma without signs of malignant transformation is established after stereotactic biopsy. Repeated MRI performed after 2 (d,e) and 3 (f–h) years reveals the increase of brain lesion, increase of perifocal oedema, an area of contrast accumulation in the structure of tumour and the formation of a necrotic area
406
tological subtype of neuroepithelial tumours, different from glioma. There are some histological variants of EP: “classic” or cellular-process EP, clear-cell EP, papillar and myxopapillar EP (Korshunov et al. 2004). The last EP variant is observed only in the areas of cauda equine and fillum terminale. EP belongs to a group of neoplasms that grow slowly. Calcifications and cysts are frequent findings in EP tissue. In cases of EP location in the fourth ventricle, it originates from the bottom of the rhomboid fossa, with typical bulging through Luschka’s foramen into neighbouring cerebrospinal spaces. EP makes up about 3–5% of all primary intracranial tumours, 15% of all tumours of posterior cranial fossa in children and it is the third most frequent tumour of subtentorial location in children. In children, EP is observed four to five times more often than in adults. The first peak of incidence falls between the ages of 1 and 5 years, the second peak, at 30 years. The total 5-year survival rate for infratentorial EP in children is 45%; in adults it reaches 60–70%. Distribution onto spinal cord is rarely observed. Thus, as a rule, the spinal ependymoma is one of the signs of type-II neurofibromatosis. Approximately 60% of intracranial EP is located in posterior cranial fossa and 40% above tentorium. The preferred location of infratentorial EP is the fourth ventricle—the affected area resembles that of pen quill—whence it can grow laterally or downward onto the posterior surface of medulla and spinal cord, quite often descending into the level of the C2–C3 vertebrae (Osborn 2004). In our series of observations, there were some cases when EP even reached the lumbar level. In the majority of cases, on CT EP looks as a moderately hyperdense tumour of the various forms with relatively even contours and hypodense areas (zones) inside (cysts), with small, as well as significant, sizes. Contrast administration in most cases leads to increase of tumour density. EP located in
Chapter 4
the projection of the fourth ventricle has a rounded shape and it typically grows to pontocerebellar and occipital cisterns. As a rule, intraventricular tumour is not surrounded by oedema. Its occurrence is observed mainly in cases in which EP invaded ependyma through to brain tissue. The calcified sites of different size are detected in an area of neoplasm in 50% of cases. As EP usually reaches large size at the primary stage (sometimes it completely occludes the lumen of one of the ventricles), it causes an occlusion hydrocephaly. Periventricular oedema is an extremely rare phenomenon; it is observed only in cases of EP of advanced stage. Periventricular oedema is observed extremely rarely, and only in late stages of hydrocephalus. When EP has homogeneous density, it is difficult to distinguish it from intraventricular meningioma. When performing differential diagnosis, it is necessary to take into account that EP has an ambiguous, uneven surface, whereas meningioma is usually of a clear, round form. It is important to remember differences in incidence and ages of patients as well as the clinical picture of disease. MRI differentiation of EP from other gliomas is mainly based on locations and topography, not on distinctions in signal intensity or degree of contrast enhancement. In cases of cysts presence, EP has hypointense signal on T1-weighted images and hyperintense (in comparison with brain tissue) on T2-weighted scans. Heterogeneity of tumour structure is caused by the presence of cysts, calcifications and tumour vascular net (Figs. 4.109, 4.110). Sometimes on T1 sequences, it is possible to visualise intratumoural haemorrhages. Signal from EP cysts is higher than signal from CSF. Contrast administration leads to non-homogeneous enhancement of moderate intensity. FLAIR sequence better visualises the border between tumour and ventricular wall. MRS demonstrates NAA peak decrease and Cho peak increase. A ratio between NAA and Cho peaks is higher than in cases of
Fig. 4.109a–c Ependymoma. T2-weighted image (a) and T1-weighted image (b) illustrate a tumour with mainly solid structure in the anterior
horn of right lateral ventricle. There is a small cyst in anteriolateral area of it. Contrast accumulation is heterogeneous (c); it demonstrates an area of infiltration of neighbouring brain tissue (arrows)
Supratentorial Tumours
407
Fig. 4.110a–c Ependymoma of the lateral ventricle. T2-weighted imaging (a) and T1-weighted imaging (b,c) with contrast enhancement. The
mass lesion of mixed structure, located in the lumen of body and anterior horn of lateral ventricle, is revealed. The contrast accumulation is not intense and heterogeneous
medulloblastoma. A Lac peak of various heights can appear. DWI reveals intraventricular formation with hyperintense MR signal. In atypical cases, it is possible to assume EP presence on the basis of many calcifications and cysts (Fig. 4.111). It is necessary to note that malignant forms (anaplastic EP) are observed more frequently than are benign EP. As a rule, they result from malignant transformation of typical EP (Fig. 4.112–4.114). It is necessary to perform a differential diagnosis of EP of the lateral ventricle from subependymoma, neurocytoma and astrocytoma. In cases of subtentorial location, EP should be differentiated from medulloblastoma, choroid papilloma, brainstem glioma and PA.
4.3.3.1
Subependymoma
Subependymoma (SEP) is a rare benign CNS tumour whose structure has histological features typical for ependymal glioma, and also for astrocytic glioma. SEP originates from tanicytes, the cells of subependymal plate (lamina) that can differentiate into astrocytes and ependymocytes. According to external examination, SEP is the dense, welloutlined tumour of white or grey colour, with poor blood supply. SEP is usually located inside ventricles, in an area of septum pellucidum or in the lower departments of the fourth ventricle (Chiechi et al. 1995). SEP is observed in patients of middle or old age; the majority of them are found at autopsy or in cases of CT (MRI) investigation performed for reasons not related to assumption of tumour. SEP has clinical presentations mainly when it causes disruption of CSF circulation. CT detects well-outlined tumour with hypo- or isodense
characteristics close to those of brain tissue. Sometimes calcifications and cysts can be observed in tumour. Contrast administration does not change tumour density. In some cases, the foci of parenchymal haemorrhage can be found. The majority of SEP has homogeneous hypo- or isointense MR signal on T1-weighted scans and slightly hyperintense in T2 sequences. MR signal from tumour is heterogeneous, reflecting the presence of multiple small cysts and calcifications in its stroma (Fig. 4.115); the latter are typically present in large-sized tumours. The oedema of the surrounding brain tissue is absent. On FLAIR images, the tumour is clearly identified as a hyperintense area on a background of dark signal from CSF in lateral ventricles. Typically, there is no contrast enhancement; however, there are cases with light, uneven accumulation of contrast. SEP located in the fourth ventricle is characterised by more intense contrast accumulation in comparison with SEP of lateral ventricles. First, the differential diagnosis should be done with ependymoma, and then with neurocytoma, subependymal giant cell astrocytoma, choroid papilloma, hemangioma and metastases.
4.3.4 Choroid Plexus Tumours Tumours of the choroid plexus originate from vascular plexus epithelium, which has neuroectodermal origin. Their incidence is no more than 0.5% of all tumours in adults, while in infants (before 1 year) they make up 10–20%. Macroscopically, the tumours of the vascular plexus look like nodes with granular and lobular surfaces. The prevailing location is inside the ventricle lumen. The tumour is closely related with
408
Chapter 4 Fig. 4.111a,b Ependymoma. CT (a,b) detects the tumour of a giant size in the right temporoparietal area with large cysts and calcifications of a various size
Fig. 4.112a–f Anaplastic ependymoma. T2-weighted imaging (a–c) and FLAIR (d) detect a large tumour with cysts in the right frontal area. There are hypointense foci in the tumour–calcifications. Tumour cyst severely compresses the lateral ventricle. Peritumoral
oedema is absent. The solid part of a tumour is isointense with brain tissue on the T1-weighted image (e). The tumour is hyperintense on DWI (f)
Supratentorial Tumours
Fig. 4.113a–f Anaplastic ependymoma of the left parietal area. Series T2-weighted imaging (a–c), T1-
weighted imaging before (d) and with contrast enhancement (e,f) detect the large tumour with cysts and sharply dilated vessels in its stroma. Peritumoral oedema is minimal. Contrast accumulation is intense, and it clarifies the internal structure of neoplasm
409
410
Fig. 4.114a–i Anaplastic ependymoma of the left frontal area (a
12-year-old patient). T2-weighted image (a) and T1-weighted images (b–d) reveal a large neoplasm of solid structure with MR signal characteristics close to grey matter. On T1-weighted images (c,d) a local increase of MR signal (microhaemorrhage) is detected in tumour
Chapter 4
stroma, and a cyst is revealed in the upper pole. MRA detects the sharp dislocation of left ACA and MCA (e). CT with contrast enhancement in coronal (f) and axial (g) projections reveals the intense contrast accumulation in the tumour. Cerebral AG shows the blood supply of tumour (h,i)
Supratentorial Tumours
Fig. 4.115a–i Subependymoma. Case 1. T2-weighted image (a), T1-weighted image (b,c). The round mass lesions well visualised in the projection of the anterior horn of left lateral ventricle and septum pellucidum. Hypointense areas on T1-weighted image are small cysts. Sagittal projection clarifies the tumour location in the lumen of left
411
ventricle. Case 2. T2-weighted imaging (d), T1-weighted imaging (e) and FLAIR (f) reveal intraventricular tumour with microcysts in its structure. Contrast enhancement (g,h) is absent. On DWI the signal is identical to the brain tissue (i)
412
Chapter 4
the vascular plexus. Among vascular plexus tumours there are choroid papilloma, anaplastic choroid papilloma and choroid carcinoma.
4.3.4.1
Choroid Plexus Papilloma
Choroid plexus papilloma (CP) is a nodal tumour with a cauliflower-like appearance. Although the majority of CP is located inside ventricular system, some large neoplasms can infiltrate brain tissue. Microscopically, these tumours are congestions of numerous papillae, which are very similar to a normal vascular plexus: the sole layer of cubiform or columniform epithelial cells surround a fibrovascular core (Sarkar et al. 1999). The sites of cystic degeneration can be found in papilloma. CP makes up about 1% of all primary brain tumours, from 0.5 to 0.6% in adults, and from 2 to 6% in children. About 85% of all such tumours are observed in the first 5 years of life. The clinical presentation of supratentorial papillomas is caused by hydrocephaly. The asymmetrical yet intense enlargement of the ventricular system is typical for these tumours. The precise origin of hydrocephaly remains unknown. The dilatation of ventricle and basal cisterns observed in 80% of cases does not relate to with disruption of CSF circulation and is most likely caused by resorption deficit. Haemorrhages and reactive ependymitis play certain roles in hydrocephaly development because they almost always accompany CP. Subtentorial CP, usually observed in adults, growing in an area of Magendie’s foramen, and eversions of the fourth ventricle cause occlusion hydrocephalus and damage of cranial nerves. In most cases, CP are benign, potentially treatable tumours, although relapses after their surgical removal are not uncommon. The 5-year survival rate after total resection is close to 100%. The overall prognosis does not necessary correlate with the level of tumour anaplasia. Outwardly, benign CP can behave like malignant neoplasm. As a rule, CP incidence in different parts of ventricular system is proportional to the volume of a vascular plexus, and therefore the tumour is more often (<50%) located in an area of the lateral ventricle triangle, less than 40% in the fourth ventricle, and 10% in other areas like the third ventricle and lateral eversion of the fourth ventricle. The most widespread CP locations in children are the lateral ventricles and then fourth ventricle; more frequent CP locations are found in adults. Bilateral or multiple tumours are an extremely rare phenomenon, they are observed in only 3–4% of all CP. They are almost never found outside of the ventricles. On CT about three quarters of all papillomas are iso- or hyperdense formations in comparison with a brain tissue. In approximately 25% of all cases, CP contains calcifications (Fig. 4.116). The intraventricular location is characteristic. The intensive relatively homogeneous contrast accumulation is typical for CP. The marked heterogeneity assumes the presence of choroid plexus carcinoma.
Hydrocephalus of all departments of the ventricular system is a frequently seen combination. In some observations, CT angiography can identify the dilated choroid artery that supplies tumour. In cases of marked dilatation of lateral ventricles and CP location in the area of a triangle, the picture of the “floating” tumour node on a vascular leg is seen. In a situation of typical location on MRI scans, the tumour has clear contours, lobular structure and it is isointense in comparison with the brain tissue (on T1-weighted images). CSF penetration between papillae gives the tumour a cauliflower-like appearance. CP are usually iso- or slightly hyperintense on T2 sequences. Sometimes, the phenomenon of signal loss from vascular structures inside of tumour can be observed. The signal from CP intensively amplifies after contrast administration (Fig. 4.117, 4.118). Hydrocephalus of all ventricular systems often accompanies CP. In some cases, there is a local invasion into brain matter; however, it is not a feature of malignant transformation. However, such invasion is more frequently observed in anaplastic forms (Fig. 4.119). Intratumoral haemorrhages are rarely visualised in CP. The tumour distribution into the subarachnoid space and walls of ventricular system is also a rare phenomenon. MRS reveals NAA peak decrease and Cho peak increase. Direct angiography detects dilation of the choroid artery, arteriovenous shunts and a vascular shadow in the venous phase of examination (Shin et al. 2001). Differential diagnosis should be performed with carcinoma of plexus, papillar EP, medulloblastoma, SEP and ASC. In adult GB, metastasis and meningioma can have similar features as CP.
4.3.4.2
Choroid Plexus Carcinoma
Choroid plexus carcinoma (CC) is primarily malignant tumour of vascular plexus epithelium, and almost always develops in the lateral ventricle. This tumour often infiltrates surrounding structures. Microscopically the tumour consists of wide fields of epithelial cells with hyperchromic nuclei and light cytoplasm. CC is not a frequent tumour; its incidence is from 10 up to 20% of all tumours of a vascular plexus. Almost all tumours are observed in adolescents and children of 2–4 years, and the average age of diagnosis is 26 months. The basic symptoms are related with hydrocephalus, and less often with brain invasion. The prognosis is favourable only in cases of total tumour resection. CT and MRI signs of carcinoma are not specific and in general they are not different from those of choroid papilloma. Both benign and malignant tumours of vascular plexus epithelium can have local brain invasion and metastasis on subarachnoid space. However, these two features are more typical for plexus carcinoma. The preoperative diagnosis is the most presumable in cases of intraventricular tumour with intensive uneven contrast accumulation on CT or MRI and wide invasion of lateral ventricular wall in a child less than 5 years old.
Supratentorial Tumours
Fig. 4.116a–i Choroid papilloma. Case 1. CT without contrast en-
hancement (a,b) and T2-weighted image (c) reveal tumour node with uneven surface that is cauliflower-like in appearance, and small calcifications. Case 2. CT without contrast enhancement detects virtually completely calcified intraventricular tumour (d,e). All parts of
413
ventricular system are dilated due to hydrocephalus. T2-weighted imaging (f,g), and T1-weighted imaging before (h) and after (i) contrast enhancement reveal tumour node with uneven surface with a cauliflower-like appearance. Contrast accumulation is minimal due to almost total calcification of tumour
414
Chapter 4
Fig. 4.117a–d Choroid papilloma of the third ventricle (a 7-year-old child). Axial CT before (a) and after (b) contrast administration detects a hypodense tumour in the projection of third ventricle with invasion into anterior horn of right lateral ventricle. The tumour’s MR characteristics are close to the brain on T2-weighted image (c) and T1-weighted image (d)
Fig. 4.118a–c Choroid papilloma. MRI before (a) and after (b,c) contrast enhancement. The tumour node with uneven surface and cauliflower-like appearance is clearly visualised
Supratentorial Tumours
Fig. 4.119a–c Anaplastic choroid papilloma (a 4-year-old child).
CT with contrast enhancement (a) shows the large tumour located in the projections of the right temporoparietal area. The ventricular
MRS in cases of CC detects NAA peak decrease, increase of the Cho peak and a high Lac peak (Figs. 4.120, 4.121, 4.122). When performing the differential diagnosis of intraventricular tumours one should remember that the following formations can be found inside ventricles: • Astrocytoma/including giant cell (Monroe’s foramen) • Meningioma (lateral ventricles) • Ependymoma/subependymoma (lateral and fourth ventricles) • Oligodendroglioma/neurocytoma (lateral ventricles, septum pellucidum) • Papilloma of choroid plexus, carcinoma (all ventricular systems) • Cysticercosis (in any place) • Metastases (in any place) • Hamartoma (ependyma of lateral ventricle) • Craniopharyngioma (third ventricle) • Medulloblastoma (superior medullary velum, fourth ventricle) • Colloid cyst (a Monroe’s aperture) • Heterotopia (subependymal area) • AVM of vascular plexus (lateral ventricles)
4.3.5 Cerebral Gliomatosis Cerebral gliomatosis (CG) is characterised by diffuse infiltration of several brain lobes by pathologically neogenic glial cells. According to WHO classification, CG belongs to neuroepithelial tumours of unknown origin. Some authors consider that CG is an extreme form of diffuse neuroepithelial glioma, while in WHO classification it belongs to the second and third levels of malignancy. The increase of brain hemispheres is observed in cases of CG; stem, cerebellum and even spinal cord can also be affected despite seemingly intact anatomical structure. The separate tumour nodes are absent; however, in some sites, the tumour
415
system is dislocated to the left. T2-weighted imaging (b,c) clarifies the tumour spreading and its location in relation to the wall of the lateral ventricle
can be more concentrated in comparison with other areas (Vates et al. 2003). Tumour glial cells of various degrees of differentiation diffusively infiltrate the brain. The main cytoarchitecture remains largely intact (Lantos 2000). Although the white matter is mainly affected, the grey matter can also be involved (20%); usually the neighbouring brain lobes are affected, and sometimes bilateral involvement can be observed. The involvement of basal ganglia (75%), corpus callosum (50%), brainstem and cerebellum (10–15%) are typical. The tumour infiltration spreads to perineural and perivascular spaces. CG is a rare tumour, and it may be observed at any age; however, it typically affects patients in the fourth and fifth decades of life. The clinical picture lacks specificity and focal signs. In the majority of cases, the neurological deficit is disproportionately and incredibly insignificant in comparison with the volume of focal lesion, personality changes and memory loss. Although any brain lobe can be affected, clinical signs are more often related with invasion of cranial (often optic) nerves and white matter pathways. The involvement of corpus callosum, fornix and peduncles of cerebellum is not a rare phenomenon. The primary gliomatosis of leptomeningeal membranes can also be observed. The disease is characterised by progressive clinical course which can last months or years; however, the final outcome is always unfavourable. The most general sign of CG is the presence of diffuse infiltrative and slightly hypodense lesion on CT, spreading into white matter. The lesion does not accumulate contrast after its administration. The subarachnoid spaces are compressed. The border between white and grey matter is blurred. Deformation and dislocation of lateral ventricles are observed in cases of asymmetrical lesion. In some cases, CT imaging can be negative (CT cannot reveal the signs of tumour). MRI detects a wide lesion of parenchyma, especially of white matter in the form of hyperintense areas on T2-weighted and FLAIR scans, without clear contours between these areas and unaffected brain. The dislocation of sulci and ventricular
416
Chapter 4
Fig. 4.120a–c Choroid plexus carcinoma (a 2-year-old child). T2weighted image (a), and axial and sagittal T1-weighted image (b,c) with contrast enhancement. The tumour on the vascular stalk is visualised in the projection of a vascular plexus of lateral ventricle.
The formation has uneven contours and intensively accumulates contrast. The dilation of all parts of ventricular system due to hydrocephalus is marked
Fig. 4.121a–d Choroid carcinoma of the left lateral ventricle (a 4-year-old child.). The large plexus neoplasm of heterogeneous structure with foci of intratumoral haemorrhages (hyperintense MR signal on T1-weighted image) and peritumoral oedema is detected (a–d)
Supratentorial Tumours
Fig. 4.122a–e Choroid plexus carcinoma (a 4-year-old child). CT series after (a) contrast enhancement detects the tumour of relatively homogeneous structure in the projection of vascular plexus of left ventricle with intensive accumulation of contrast medium.
417
The tumour MR signal characteristics are close to brain tissue on T2-weighted images (b) and T1-weighted images (c); the vascular stalk is well visualised. MRS (d,e) reveals high Cho peak with decrease of peaks of other metabolites
418
Chapter 4
system can be only slight. The difference between signals from white and grey matter weakens on T1-weighted images, the gyri are thickened and subarachnoid fissures are compressed (Figs. 4.123, 4.124). Contrast accumulation is absent. DWI MRI demonstrates wide areas of slightly limited diffusion. MRS reveals increase of the mI peak and moderate decrease of the NAA peak. The diffuse nature of CG lesion means that it must be differentiated from widespread demyelination (multiple sclerosis, progressive multifocal leukoencephalopathy), viral encephalitis, diffuse changes in patients with severe atherosclerosis, AA, lymphoma and metabolic encephalopathy. In this regard, biopsy of the most affected (according to MRI data) brain areas is necessary for establishing the diagnosis. In the advanced stage, areas of contrast accumulation can appear (Fig. 4.125). Leptomeningeal gliomatosis can be similar to meningeal carcinomatosis.
4.4
Neuronal and Mixed Neuronal–Glial Tumours
Neuronal and mixed neuronal–glial tumours comprise a group of relatively rare neoplasms, fully or partially built from cells of neuronal origin, with high level of tissue differentiation. Gangliocytoma, ganglioglioma, childhood desmoplastic ganglioglioma, dysembryoplastic neuroepithelial tumour and neurocytoma belong to this group. Unlike neurocytoma, which as a rule is observed in young age and has intraventricular location, the other neoplasms are mainly located in brain hemispheres or cerebellum. The difference between gangliocytoma and ganglioglioma consists of a degree of cell density and presence of certain glial elements. For instance, ganglioglioma is a bifaceted tumour that consists of gangliocytoma and PA elements.
4.4.1 Ganglioglioma Ganglioglioma (GG) belongs to highly differentiated CNS tumours of neuroepithelial origin, and it is characterised by slow growth and the presence of ganglionic and glial cells in its structure. GG frequently causes temporal epilepsy, because its preferred location is the temporal lobe. It can be found in other parts of the CNS; the following rare locations are observed: brainstem, cerebellum, pineal area, optic nerves and optic chiasm, intraventricular space and spinal cord. GG incidence is up to 1% of all intracranial tumours; it is the most frequent tumour among the neuronal and mixed neuronal– glial tumours. In children, the incidence of GG reaches 4%. It is believed that GG is the tumour of the young—about 80% of all patients are people less than 30 years. The peak of incidence falls between the ages of 10–20 years. In the clinical picture, chronic temporal epilepsy is a main symptom in more than 40% of all patients. In children, GG can reach considerable sizes and form cysts. The presence of small (up to 2–3 cm) tumour nodes of superficial location is typical for adults. Anaplastic transformation is a rare but possible feature (Nakajima 1998).
On CT, the solid part of a tumour has mixed density, and the presence of calcifications in GG stroma (35–50%) is typical. Contrast accumulation is observed in 50% of cases, and it has a heterogeneous character. MRI signs of the tumour vary. Its solid part is hypointense on T1-weighted imaging and hyperintense on T2 sequences (Fig. 4.126). Cysts are more visible on T2-weighed scans. Located superficially, GG often causes deformation of neighbouring gyri; additionally, signs of cortical dysplasia can be revealed. The calcified parts of the neoplasm have hypointense MR signal. The contrast accumulation shows on CT uneven character (Selch 1998). The differential diagnosis is usually performed with pleoASC, dysembryoplastic neuroepithelial tumour, PA, LGA and oligodendroglioma. Pure CNS GC is a rare phenomenon; its incidence is no more than 0.1% of all tumours. On CT, the neoplasm looks like slightly hyperdense structure. Cysts and calcifications are not typical for this tumour. Contrast enhancement is slight or absent. In some cases, CT does not demonstrate the pathological changes of brain tissue density (taking into account the superficial location). On MRI, the best visualisation can be achieved with T2 and FLAIR sequences that can identify the GC signal characteristics, which are virtually identical to those of grey matter.
4.4.2 Dysplastic Cerebellum Gangliocytoma Dysplastic cerebellum gangliocytoma is also known as Lhermitte-Duclos disease. It is a rare brain tumour with typical location in the projection of a cerebellum’s hemisphere. Usually the entire hemisphere is involved in the process. It is characterised by a mixed histological picture with the presence of hamartoma as well as tumour transformation (Nowak et al. 2002). It can be accompanied by the thickening of skull bone structures on the same side. Mainly, it is observed in patients of young age (average age is about 30 years). The symptoms of increased intracranial pressure with development of hydrocephalus, headache, oedema of optic nerves and symptoms of cerebellum damage (ataxia, dizziness) prevail in the clinical picture of the disease. CT detects slightly hypo- or isodense tumour without calcifications and contrast enhancement. Only mass effect with compression of the fourth ventricle can be visualised. The method of choice is MRI using T2 and FLAIR sequences. The typical picture of cerebellum is lost on T1-weighted images, the hemisphere is increased, and the fourth ventricle is dislocated. The dislocation of cerebellar tonsils into the occipital foramen with the development of early secondary syringomyelia is often observed in the sagittal projection. The uneven increase of MR signal, sometimes resembling the paths of cerebellar gyri and laminated structure, is a typical tumour feature on T2 and FLAIR sequences (Fig. 4.127). Some authors distinguish “striation” or “banding” as characteristic MRI symptoms of a tumour (Meltzer et al. 1995). Contrast accumulation is absent. MRS reveals the decrease of NAA, Cho and mI peaks. MR perfusion demonstrates increase of rCBV and rCBF values from tumour in comparison with
Supratentorial Tumours
Fig. 4.123a–f Cerebral gliomatosis. T2-weighted imaging (a), FLAIR
(b) and T1-weighted imaging (c) reveal the diffusive changes of MR signal intensity from medial departments of both frontal lobes, corpus callosum and the cortex of convexity surface of left frontal lobe. Sulci of affected area are narrowed, and subarachnoid fissures are not
Fig. 4.124a–c Cerebral gliomatosis. MRI at the level of bodies of the
lateral ventricles on T2-weighted imaging (a), T1-weighted imaging with contrast enhancement (b) and DWI (c) detect diffusive affection of the right temporal, part of the parietal and frontal lobes with
419
visible. The ventricular system is compressed in anterior areas. After enhancement (d,e), the foci of contrast accumulation in an area of pathology are not observed. T2-weighted imaging (f) clarifies the level of affection of middle brain structures
the involvement of corpus callosum and the left internal capsule. Contrast accumulation in an area of pathology is absent. On DWI the affected structures are slightly hyperintense in comparison with normal structures
420
Fig. 4.125a–i Cerebral gliomatosis. T2-weighted imaging (a–c) and FLAIR (d–f) reveal diffuse lesion of white and partly of grey matter of both hemispheres: sulci are narrowed, subarachnoid fissures are not visible and the anterior part of the ventricular system is compressed. After contrast enhancement (g), an area of uneven contrast
Chapter 4
accumulation is detected in the projection of genu of corpus callosum. On DWI, the signal from affected structures is close to those from normal brain tissue (h). MRS (i) reveals the decrease of NAA and Cho peaks, increase of the mI peak
Supratentorial Tumours
Fig. 4.126a–h Intraventricular ganglioglioma (10-year-old child). CT before (a) and after contrast enhancement (b,c) detects the widespread tumour that fills the lumen of posterior and inferior horns of bodies of lateral ventricles. Tumour has calcified sites (hyperdense). Tumour slowly accumulates contrast. On T1-weighted image (d)
421
and T2-weighted images (e,f) tumour has compact structure; calcifications in stroma are better visualised on T2-weighted imaging. Contrast accumulation is intense on MRI and it clarifies the lesion spreading (g,h)
422
Fig. 4.127a–c Dysplastic gangliocytoma of cerebellum (Lhermitte-
Duclos disease). T2-weighted imaging (a) and T1-weighted imaging after contrast administration (b,c) detect an area of slight change of
the opposite hemisphere. First, differential diagnosis should be performed for ischaemic stroke (in a territory of superior cerebellar artery or posterior inferior cerebellar artery), then follow infectious (bacterial and virus) lesions of cerebellum, then congenital anomalies (cerebellar dysplasia, rombencephalosynapsis), tuberous sclerosis and granulomatous lesions of posterior cranial fossa.
4.4.3 Desmoplastic Infantile Ganglioglioma and Desmoplastic Infantile Astrocytoma Desmoplastic infantile ganglioglioma and desmoplastic infantile astrocytoma CNS neoplasms have similar histological, radiological and clinical signs. They are volumetric formations of a child’s age, with the presence of much connective tissue. They reach relatively large sizes and have supratentorial and superficial location (Shin et al. 2002). They are most frequently diagnosed in an interval between the first and twentyfourth months of life; the incidence peaks between the ages of 3 and 6 months. In the literature, there are some rare reports about patients as old as 17 years. CT and MRI reveal a large-sized hemispheric neoplasm with cystic and solid components (Fig. 4.128). The tumour node is usually adjacent to cortical brain departments or has the paraventricular location. The marked contrast accumulation in the solid part is observed (Fig. 4.129), while the cystic part does not accumulate contrast. MRI demonstrates a solid component of a neoplasm with typical enhancement of neighbouring brain meninges better than CT does (Tamburrini et al. 2003). The differential diagnosis is conducted with primitive neuroectodermal tumour, supratentorial ependymoma, pleoASC, hemangioblastoma, PA and ganglioglioma.
Chapter 4
MR signal in the projection of the right hemisphere of cerebellum, with spread into vermis. Contrast accumulation in the area of pathology is absent
4.4.4 Dysembryoplastic Neuroepithelial Tumour DNET is a tumour of mixed structure with the presence of glial and neuronal elements. It belongs to a group of benign localised tumours situated in a projection of a brain cortex and often accompanied by cortical dysplasia. It makes up less than 1% of all primary brain tumours and approximately about 1–2% of all primary tumours in patients younger than 20 years. It is more frequently diagnosed in the temporal area (hippocampus, amygdaline nucleus), and is mainly observed in the first two decades of life. In the clinical picture, epileptic seizures predominate. Tumour macrostructure is characterised by precise borders and multiple cysts of various sizes from small formation within the limits of one gyrus up to huge forms (within the limits of one lobe). The hypointense area with clear contours in a projection of cortical and subcortical departments of the affected lobe is detected on CT. The excavation of internal bone plate in a site of tumour attachment is observed in 40–60% of cases. Calcifications are not an exception and are visualised in about 30% of all DNET. Typically, contrast accumulation of any sort is absent, although there are cases with point increase of density after intravenous contrast administration (Fig. 4.130). Direct angiography does not reveal the vascular net. MRI demonstrates a foam-like internal structure of a tumour, with multiple microcysts (Fig. 4.131). The tumour tissue has hypointense signal on T1 sequences and moderately hyperintense on T2 scans. FLAIR sequence better demonstrates the changes of brain tissue on the periphery of the cysts (Stanescu Cosson et al. 2001; Fernandez et al. 2003). Perifocal oedema is absent. DWI images are not specific, and they reflect only free character of diffusion in cystic areas of DNET. As a rule, the tumour does not accumulate contrast. The dot or ring-shaped
Supratentorial Tumours
423
Fig. 4.128a–f Desmoplastic infantile ganglioglioma (2-year-old child). T2-weighted imaging (a–c) and T1-weighted imaging (d–f) detect
widespread tumour that covers brain from all sides in a helmet-like fashion
Fig. 4.129a–c Desmoplastic ganglioglioma of the left occipital parietal area. FLAIR (a) and T1-weighted image with contrast enhancement
(b,c) detect tumour of a mixed structure with large solid and cystic component. The tumour has paraventricular location and partly passes to the surface of cortex of the left occipital lobe
424
Chapter 4
Fig. 4.130a–c DNET of left parietal area. CT without contrast enhancement detects a small hypodense tumour in cortical and subcortical
regions of left parietal area (a–c)
Fig. 4.131a–f DNET of the right frontal lobe. T2-weighted images (a,b) and T1-weighted images (c–f) without contrast enhancement demonstrate a tumour of small size with fume-like structure due to the presence of microcysts in cortical and subcortical regions of the right frontal lobe
Supratentorial Tumours
contrast accumulation on MRI series performed after contrast administration is seen in only in 20% of cases. The prognosis after surgical resection is favourable; cases of malignant transformation are not described in the literature. It is enough to perform control MRI investigation once a year.
4.4.5 Central Neurocytoma Central neurocytoma (CN) is a rare type of brain neoplasm. It makes up less than 1% of all primary tumours and about half of all intraventricular mass lesions of a brain in adults (Bigner et al. 1998). Now, about 300 observations of these tumours are described in the literature (Ashkan et al. 2000). This neurocytoma was recognized as an independent type of tumour of the CNS in 1982 when Hassoun with co-authors (1982) conducted an electronic microscopic study of two tumours of the lateral ventricles. In tumour structure alongside glial cells, they found cellular structures with neuronal differentiation and the presence of axons, microtubules, neurosecretory granules and synaptic vesicles (Hassoun et al. 1982). Earlier, these tumours belonged to oligodendroglioma or ependymoma. In the last edition of the international WHO classification of CNS tumours issued in 2000, hemispheral neurocytoma was included in the “Neuronal tumours” section (Kleihues and Cavenee 2000). Usually, these tumours are intraventricular, calcified neoplasms in young patients. They are characterised by a certain clinical, radiological and morphological similarity. Clinically, the tumour manifests by an increase of intracranial pressure, visual and mental impairments, and sometimes by endocrine and pyramidal symptoms. Brain neurocytoma is mainly located in the lumen of lateral ventricles, and its preferred locations are an area close to septum pellucidum and/ or Monroe’s foramen. The side does not play a role. Sometimes they reach gigantic sizes; they almost completely fill the ventricular system, obdurating both lateral ventricles and penetrating into the third and even fourth ventricles through the aqueduct of cerebrum and infiltrating the surrounding structures. According to direct cerebral angiography data, the level of blood supply of a tumour varies from full absence (30– 40% of cases) to moderate or poorly expressed vascular net (50–60%). In rare cases, the intensive blood supply of CN is observed. In cases of vascular net presence, blood supply is mainly conducted from anterior choroid artery, lateral, and medial lenticulostriatal arteries, and rarely from the branches of pericallosal artery or recurrent artery (Fig. 4.132). Venous outflow from neurocytoma passes through the hypertrophied drainage veins to an internal brain vein, then further to Galen’s vein and to a direct sinus. The dislocation of cerebral arteries and deep-seated brain veins is observed in cases of vascular net absence. On CT, central CN looks like delimited tumour of mixed (heterogeneous) density; it often contains solitary or multiple calcifications and cysts. In the majority of observations, the tumours are diagnosed when they reach relatively large size. According to our data based on investigations of 76 patients
425
with neurocytoma, in 50% of cases (38 patients) tumour has mixed structure, in 39% tumour is mainly hyperdense, in 4% is hypodense, and in 7% of cases, it is isodense. The presence of calcifications of various form and size are typical for neurocytoma (50–70%) (Fig. 4.133). The dilatation of lateral ventricles due to hydrocephaly is always observed in cases of neurocytoma. As a rule, the hydrocephaly is obstructive; tumour development leads to occlusion of Monroe’s foramen. In our series of observations, 95% of patients had hydrocephalus of various degrees. On MRI in the majority of cases, the main part of tumour is isointense with the brain cortex. On T2-weighed MR images, neurocytoma has a mixed signal (Figs. 4.134, 4.135). The presence of cysts is a special feature of this tumour, and cysts can be better visualised on T2-weighted MR scans in FLAIR sequence. Such cystic changes were registered in the majority of observations (69%). The degree of contrast enhancement varies (according the CT and MRI data); however, the moderate accumulation is most frequent, although cases with extremely high contrasting of tumour tissue have also been described. The contrast accumulation can be minimal (14%) or altogether absent (Nishio et al. 2000; Pronin et al. 2002). MRI estimates the distribution of the tumour into ventricular system, its relation to septum pellucidum and corpus callosum, and the degree of brain tissue invasion better than CT does. The latter information is extremely important in intervention planning. Our study demonstrated that tumour can infiltrate the wall of lateral ventricles in several sites (Fig. 4.136). Intratumoral microhaemorrhages (up to 20%) are better visualised on MRI. On CT, they were usually considered as cystic changes. Haemorrhages are better revealed on T1 sequences as areas of hyperintense MR signal, or on T2* sequence as zones of hypointense signal. MRS detects the high Cho peak and marked decrease of peaks of main brain tissue metabolites such as NAA and Cr. Also, the increase of ratios between Cho and Cr peaks, and Cho to NAA, is observed. In many cases a Lac peak appears. The solid parts of tumour tissue are characterised by a signal increase on DWI (i.e. the decrease of diffusion rate of water molecules in tumour tissue), reflected on colour maps built based on the measured diffusion coefficient. Intratumoral cysts have typical changes on DWI as MR signal decrease— the increase of diffusion rate (Fig. 4.137). The differential diagnosis of brain neurocytoma should be performed with tumours located inside the ventricular system, often with EP, SEP, choroid papilloma, and more seldom with giant cell astrocytoma, meningioma and PA.
4.5
Embryonic Neuroepithelial Tumours
Embryonic neuroepithelial tumours are a group of highly malignant neoplasms of neuroectodermal origin that consist of cells with a low tissue differentiation. It is widely believed that all embryonic tumours originate from a common source— primitive, multipotent cells—and they are considered as PNET. The majority of embryonic tumours are medulloblastomas,
426
Fig. 4.132a–f Neurocytoma. Case 1. Neurocytoma of the right lateral ventricle. Cerebral angiography: The slightly expressed vascular net of tumour is revealed. The blood supply is performed via the pericallosal artery (a). The hypertrophied lenticulostriatal arteries (b,c) participating in tumour blood supply are demonstrated (double arrows). The recurrent (Heubner’s) artery that supplies tumour is also visualised well. The slightly expressed vascular net is revealed in capillary phase. Case 2. Neurocytoma of the lateral ventricles, with
Chapter 4
prevalence on the left. Cerebral angiography: the abundant vascular net of tumour (d,e) in the projection of lateral ventricles. The blood supply is performed from multiple coiled branches of the pericallosal artery territory and from the thalamoperforating and the posterior choroid arteries (arrows). The drainage (f) from tumour is performed through hypertrophied vein to the internal vein, and then, into the great vein of Galen and straight sinus
Fig. 4.133a–c Neurocytoma of the lateral ventricles. CT of three cases. The small calcifications (a), the large ones (b) and calcifications of uneven structure (c)
Supratentorial Tumours
427
Fig. 4.134a–c Neurocytoma of lateral ventricles. T2-weighted image (a) and T1-weighted images (b,c) without contrast enhancement reveal a tumour of heterogeneous structure with multiple relatively large cysts. Hydrocephalus of lateral ventricles is present
Fig. 4.135a–c Neurocytoma of the lateral ventricles. T2-weighted images (a,c) and T1-weighted image (b). Tumour is isointense with brain tissue and has multiple small cysts. The hydrocephalus of lateral ventricles is observed
428
Chapter 4
Fig. 4.136a–e Neurocytoma of the lateral
ventricles. Case 1. T2-weighted image (a) and T1-weighted image (b). The tumour has heterogeneous structure and large cyst. There is a filling the anterior horn of right lateral ventricle by the tumour. Case 2. T2-weighted image (c) and T1-weighted images before (d) and after (e) contrast enhancement. Intensive contrast accumulation of the tumour is revealed. Arrows indicate a wide area of infiltration of a wall of the left lateral ventricle
Fig. 4.137a–c Neurocytoma of the lateral ventricles. On DWI the tumour has a high MR signal (a). ADC map (b) shows a low level of diffu-
sion coefficient compared with brain tissue. MRS (c) demonstrates high Cho, and decrease of NAA and Cr peaks
Supratentorial Tumours
429
which mainly have subtentorial location (they are described below). The tumour can only metastasize on brain membranes, with formation of supratentorial nodes (Fig. 4.138). The other neoplasms, such as medulloepithelioma, hemispheric neuroblastoma and ganglioneuroblastoma, and ependymoblastoma are observed extremely rarely.
4.5.1 Medulloepithelioma Medulloepithelioma is a tumour of early childhood (mainly before 5 years); congenital cases are described. As a rule, it is observed in supratentorial paraventricular areas of the lateral ventricles (Fig. 4.139). In comparison with neuroblastomas of the peripheral nervous system, the CNS form is an extremely rare phenomenon; according to statistics, it is observed in 0.5% of most cases. However, it is believed that their incidence can reach up to 20% of all brain neoplasm in newborns.
4.5.2 Ependymoblastoma Ependymoblastoma has features of ependymal differentiation; it is observed rarely, more often in children of up to 5 years. It is possible to suspect PNET in a child with large hemispheric neoplasm of complex structure, with minimal perifocal oedema. CT signs of this group of tumours are relatively typical. On scans without contrast enhancement, the tumour is usually hyperdense (a solid component) in comparison with brain tissue. As a rule, by the time it has been diagnosed, the tumour reaches large size. According to CT, calcifications are observed in about 50% of cases, and haemorrhage in a tumour tissue, in up to 10% of cases. Zones of necrosis or cysts look like hypodense areas. Non-homogeneous and moderate contrast accumulation is observed in the majority of cases. MRI indications of these tumours are similar to CT indications. Usually, there is a large neoplasm (≈5 cm) located in white matter close to ventricular system. PNET can also be
Fig. 4.138a–d Medulloblastoma of the posterior cranial fossa with metastases. T2-weighted images (a,b) and T1-weighted images (c,d). The tumour is placed in the projection of the fourth ventricle, and multiple metastases in subependymal area and left frontal area are seen
430
Chapter 4
Fig. 4.139a–c Medulloepithelioma (a 5-year-old child). T2-weighted imaging (a,b) and T1-weighted imaging (c) detect a neoplasm of heterogeneous structure with cysts in right posterior frontal area. The tumour spreading is better evaluated on T2-weighted imaging
observed in the pineal area, subcortical nodes and in the suprasellar region. Nodal forms of tumour are well separated from brain tissue according to MRI data. The solid component on T2 sequences is unevenly hyperintense (Fig. 4.140). Cystic–necrotic changes can be better detected on T2 images. In cases of intratumoral haemorrhage, MR signal changes depend on the stage of the bleed: for subacute stage, an increase of MR signal on T1 sequences is most typical. Characteristics of contrast enhancement are similar to those obtained from CT. PNET membranous metastases are better visualised with FLAIR sequence after intravenous contrast administration. Absent or minimal perifocal oedema despite the relatively large size of neoplasm is a distinctive feature of these tumours (Fig. 4.141). Differential diagnosis should be performed for astrocytoma, ependymoma, oligodendroglioma, teratoidrhabdoid tumour and choroid plexus carcinoma.
4.5.3 Teratoid–Rhabdoid Tumours Teratoid–rhabdoid tumours are rare brain tumours that are usually found in children. They consist of rhabdoid cells, PNET areas, as well as malignant mesenchymal and epithelial tissue (Lee 2002). They are rarely diagnosed in children older than 3 years. Teratoid–rhabdoid tumour makes up about 20% of all primitive malignant tumours in children younger than 3 years. In half of cases, they have infratentorial location away from the middle line, usually in the projection of the cerebellopontine corner. Also teratoid–rhabdoid tumours can be observed in hemispheres of the cerebellum and in the brainstem. In cases of supratentorial location, they are in a brain hemisphere or suprasellar area. In 15–20% of cases, the tumour spreads to other brain tissue.
On CT, the tumour looks like volumetric hyperdense formation. Cysts and haemorrhages are often found in tumour stroma, whereas calcifications are rare. Obstructive hydrocephaly is revealed in cases of marked mass effect. MRI using T1 sequence reveals an isointense tumour with areas of hyperintense signal. These areas correspond with subacute haemorrhages. The cystic site of the lesion can be better visualised on T2 and FLAIR sequences. DWI detects the diffusion decrease, while the signal from the solid part is increased (Meters et al. 2006). Contrast accumulation has uneven and usually marked character. Metastases in brain tissue are detected in a form of linear or nodal sites of contrast accumulation (Lee 2004). Differential diagnosis in cases of subtentorial location should be performed for medulloblastoma, PA, choroid papilloma, ependymoma and haemangioblastoma.
4.5.4 Neuroblastoma (Metastatic) Neuroblastoma (metastatic) is a malignant tumour of the sympathetic nervous system. Its primary location is the paravertebral area of inferior thoracic and lumbar departments of the vertebral column. Intracranial tumours have metastatic origin (typical for stage IV of disease). Neuroblastoma is one of the most widespread solid extracranial neoplasms in children, and it makes up about 8–10% of all cases of cancer in children. The average age of incidence is 22 months. Up to 79% of all cases are diagnosed in children less than 4 years old. The most typical clinical symptom is the “raccoon-eyes” sign, bilateral periorbital brightening and ecchymosis. CT is the best method of diagnosis of bone alteration. In cases of visceral cranium involvement, typical spicule formation (periostitis) in the projections of bone walls of the orbit and wings of sphenoid bone is seen—a “hair-on-end” appear-
Supratentorial Tumours
431
Fig. 4.140a–e Ependymoblastoma of left
frontal-parietal area (a 12-year-old child). CT (a) after contrast enhancement detects a large, moderately hyperdense tumour with unclear borders; the surrounding oedema is minimal. T2-weighted image (b) and T1-weighted image (c) reveal a solid neoplasm with multiple small vessels in its stroma in convexity of left frontoparietal area. The tumour intensively enhanced (d,e)
432
Chapter 4
Fig. 4.141a–c PNET (a 4-year-old child). T2-weighted imaging (a,b) and T1-weighted imaging (c) detect a neoplasm of heterogeneous structure with signs of subacute intratumoral haemorrhage in deep departments of right temporal area
ance (Fig. 4.142). Contrast enhancement helps in detection of soft tissue components, with typical intraorbital spreading (Matthay et al. 2003). MRI signs of neoplasm are uneven changes of MR signal. The tumour is isointense with brain tissue on T1 sequences, whereas on T2-weighted imaging, it has hypointense signal and hyperintense in FLAIR sequences. Intravenous contrast administration improves visualisation of soft tissue part of a tumour more precisely than on CT, demonstrating the degree of spreading (Fig. 4.143). The sequence with suppression of signal from fat should be used to estimate the intraorbital component. The presence of additional metastases in bones of calvarium is not an exception, and they can be diagnosed together with the lesions of the orbital bones. Differential diagnosis should be done for leukaemia, Langerhans cell histiocytosis, episubdural haematoma, Ewing’s sarcoma and osteosarcoma.
4.6
Primary Lymphoma of the CNS
Primary lymphoma of the CNS (PLCNS) belongs to tumours of haematopoietic tissue, with unknown pathogenesis. Until recently, PLCNS was a rare disease and made up about 1% of all brain tumours. However, during the past two decades, the number of patients with this disease has dramatically increased, according to some data more than threefold, from 0.8–1.5% to 6.6% of all primary intracranial tumours, which is mainly related to the drastic increase of number of people with various types of immunocompromise, e.g. AIDS.
According to a U.S. statistical commission recently, the number of patients with PLCNS has increased more than ten times, from 2.5 cases per 10 million in 1973 to 30 per 10 million in 1999. For AIDS patients this figure is in 3,600 times higher than for the general population: 2–12% of AIDS patients fall ill with lymphoma (Arbaiza et al. 1992; Grangier et al. 1994; Chiang et al. 1996). The quantity of patients under types of drug immunosuppression has grown, and figures include, for example, patients with organ transplants. Among other diseases that increase the risk of primary lymphoma of CNS are collagen diseases (systemic lupus erythematosus, rheumatoid arthritis, etc.) and chronic viral infections, in particular, virus-carrier state of Epstein-Barr virus. Histologically, PLCNS resembles non-Hodgkin’s lymphoma and B-cell lymphoma (Bergmann and Edel 1991). Primary T-cell lymphomas of CNS are also described; however, they are observed rarely. The question about the lymphoma origin is still being discussed. It is unknown whether primary lymphoma forms in the CNS or outside its borders, and why and how it appears in organs lacking a lymphatic system. There are three hypotheses trying to explain this: 1. B cells transform somewhere in the body and form adhesive molecules specific for brain vessels endothelium; this leads to development of the primary tumours directly inside the CNS. 2. Cells of lymphoma are regularly and systematically destroyed by and intact immune system; however, they can be relatively protected inside the CNS, and begin progressing here.
Supratentorial Tumours
433 Fig. 4.142a–f Metastatic neuroblastoma. Axial CT images (a,b) demonstrate the affection of skull base and calvarium bones in fronto-orbital region with typical spiculated periostitis—a “hair-on-end” appearance. On MRI (c–e) with contrast enhancement spreading of the tumour with affection of the bone structures is well seen
434
Chapter 4
Supratentorial Tumours
435
9 Fig. 4.143a–p Neuroblastoma. Case 1. CT before (a) and after (b) contrast enhancement shows a large tumour of compact structure with moderate contrast accumulation in the projection of the left lateral ventricle. T2-weighted image (c) and T1-weighted image (d,e) before contrast enhancement detect a large zone of haemorrhage in the tumour structure (hyperintense MR signal on T1-weighted imaging). The visualisation of neuroblastoma spreading both inside ventricles and outside the ventricular system improves after CE (f–i). Case 2. CT before (j,k) and after (l,m) CE. The tumour of heterogeneous structure with peripheral contrast accumulation and signs of a “blooming” intratumoral haemorrhage is detected in the projection of triangle of right lateral ventricle. T2-weighted imaging (n) and T1-weighted imaging before (o) and after (p) CE well visualise a tumour of round shape, located in the projection of triangle of right lateral ventricle. The hyperintense site on the T1-weighted image is an intratumoral haemorrhage (subacute stage). The tumour’s enhancement is intense; it improves the delimitation of tumour from brain tissue. In addition, the tumour metastases into left frontal parasagittal area and along subarachnoid spaces are revealed
436
3. Polyclonal intracranial foci of an inflammation can clone within the limits of a brain and progress into monoclonal neoplasm. Surgical intervention in cases of CNS lymphoma with attempts of its total removal does not influence the overall prognosis of the disease, and results of surgical treatment are unfavourable: high mortality and many complications in comparison with specific chemotherapy. It is reasonable to perform a stereotactic biopsy for verification of the histological diagnosis in cases of suspicion of brain lymphoma. Such verification is necessary for conducting chemo- and radiotherapies. Therefore, establishing the diagnosis is an extremely important task, which can substantially decrease the number of unreasonable surgical interventions. Regarding location, up to 90% of lymphomas are supratentorial lesions. In more than three quarters of all observations, the tumour is presented as a sole node; in the rest of cases,
Fig. 4.144a–f Lymphoma. Variants of CT images of tumours with
different structure and location: solid shape of tumour of right temporoparietal convex area (a), mixed with central necrosis of genu of
Chapter 4
multiple lesions are detected. The most frequent locations for lymphoma are the periventricular area, basal ganglia and oral departments of brainstem and cerebellum. There are reports about involvement of pineal and suprasellar areas and brain matters. Primary CNS lymphoma is usually located in brain tissue, while systemic lymphoma with CNS involvement usually has leptomeningeal and dural spreading; however, parenchymal location is also possible. Secondary meningeal distribution is observed in 30–40% of all primary lymphomas, while the incidence of primary leptomeningeal lymphoma is up to 8%. Primary dural and epidural lymphoma is an extremely rare phenomenon. Meningeal infiltration can declare itself by contrast enhancement in corticomeningeal structures, although CT and MRI cannot reliably detect lesions of the dura matter and orbit. The main clinical symptoms of the PLCNS are the following: general neurological symptoms (25%), focal neurological signs (60%), epileptic seizures (15%) and uveitis (12%).
corpus callosum (b), solid of splenium of corpus callosum (c), solid node of midbrain (d), multiple with mixed structure (e) and multiple convexity with haemorrhage (f)
Supratentorial Tumours
437
Tumour nodes look like clearly limited volumetric formations of different sizes; often they are round with precise contours. A compact solid tumour structure is observed in some patients, and in others, a small portion of tumour has in its stroma zones necrotic degeneration of a different volume. The latter symptom is typical for lymphoma in HIV-positive patients. According to routine CT data, in most cases the tumour is hyperdense; isodense tumour is diagnosed in only 20% of observations. The density of necrotic area in tumour stroma is less than the density of stroma itself. The intensive contrast accumulation in the stroma of lymphoma after intravenous contrast injection is a typical CT sign of tumour and is almost always observed. In our group of 65 patients, the nodal type of contrast enhancement was observed in 93% of cases, 6.5% of patients had ring-shaped contrast accumulation and only in 0.5% of cases (1 patient) was there no contrast enhancement. The oedema of surrounding brain tissue of varying degree
is detected as a hypodense area around hyperdense tumour mass (Fig. 4.144). According to MRI data, tumour stroma has an isointense or slightly hypointense signal on T1- and T2-weighted images in comparison with unaffected grey matter (Fig. 4.145). In cases of necrotic degeneration (as a rule in central parts of tumour), this area is characterised by high signal on T2-weighted imaging and low signal on T1-weighted imaging (Fig. 4.146). The perifocal oedema is hyperintense on T2-weighted imaging and hypointense on T1-weighted imaging. Such oedema is observed in 30–40% of cases. Contrast enhancement leads to homogeneous contrast accumulation in the tumour stroma; in cases of no contrast enhancement in the necrotic area (if tumour has such area), the ring-shaped contrast enhancement is detected (Fig. 4.147). Many authors report the absence or presence of slight peritumoral oedema around lymphomas (in our observations, only 32% of lymphomas have such oedema), which
Fig. 4.145a–f Multiple solid brain lymphoma with the lesion of genu
enhancement—the homogeneous character of contrast accumulation of lymphoma is seen, and DWI (b = 1000) signal from tumour is moderately hyperintense and blends with an area of oedema (e). ADC map (f): the lymphoma’s stroma has ADC value close to unaffected white matter; areas of vasogenic oedema have high ADC values
of corpus callosum and spread into the white matter of both frontal lobes, left parietal area and left thalamus. MRI T2-weighted image (a): the signal from tumour is slightly hypointense with unaffected white matter; T1-weighted images before (b) and with (c,d) contrast
438
Fig. 4.146a–f Multiple lymphomas with the presence of a large tumour node in the right parietotemporal area, adjacent to the triangle of lateral ventricle. a T2-weighted image: the tumour stroma with slightly hyperintense signal in comparison with white matter and which has an area of necrotic destruction in its central part is clearly
Chapter 4
visualised on a background of vasogenic oedema. T1-weighted image before (b) and with (c) contrast enhancement, DWI (b = 1000) (d), ADC map (e) and spectra from necrotic, central area of lymphoma (f) (reduction of NAA and high Lac–Lip complex peaks, which identify the processes of destruction)
Supratentorial Tumours
Fig. 4.147a–i Lymphomas of the CNS on the MRI with contrast
enhancement, variants of location: solid hemispheric (a), splenium of corpus callosum (b), septum pellucidum (c), lateral ventricle (d), hemispheric convex area with the impact on the tentorium of cer-
439
ebellum (e), multiple hemispheric solid (f), multiple paraventricular with necrosis (g), hemisphere of cerebellum (h) and the cisternal part of the left trigeminal nerve (i)
440
Chapter 4
together with the above-mentioned neuroimaging features distinguishes lymphoma from malignant glioma. However, it is widely known that hormone therapy leads to decrease of brain oedema. In addition, the use of steroids results in substantial decrease or disappearance of the lymphoma nodes, which does not happen with glial tumours. This caused some authors to call lymphoma the “ghost tumour” (Forbes 1992). On DWI, lymphoma has a hyperintense signal and is characterised by the value of ADC close to normal grey tissue or lymphoma can have slightly increased ADC (Fig. 4.148). The following data were obtained analysing DWI results (average values of ADC × 10–3 mm/s2) for 17 observations (Table 4.1). 1 H MRS reveals in lymphoma the spectrum similar to malignant glial tumours. However, unlike glioma, in the lymphoma spectrum the changes of peak sizes are less marked: the moderate increase of Cho peak and substantial growth of Lip–Lac complex (also observed in glioblastoma and to a lesser extent in AA) is noted; however, the decrease in the NAA peak is not intensive. The analysis of results of our spectroscopic examination allowed finding out the average values of the metabolite ratios in a spectrum, characteristic for brain lymphoma (Table 4.2). Thus, the main features of lymphoma’s spectrum are the moderate decrease of the NAA peak with increase of Cho and Lac (and Lip) peaks and a low mI peak. MRS values of lymphoma overlap those of malignant glioma to a certain degree, although MR/CT perfusion investigations demonstrate higher specificity for lymphoma. It appears the digital values detected in stroma of lymphoma at examinations performed by various authors are characterised by lower perfusion parameters, dissimilar to those of malignant tumours of the CNS with an identical degree of contrast enhancement on postcontrast images (Fig. 4.149). In Table 4.3, average values of perfusion parameters in stroma of lymphoma are presented. According to the analysis of results of lymphoma surgical removal in our institute, practically in more than half of cases the remains of a tumour are detected after operation. In addition, percent mortality in this group is higher than in surgery of all other intracranial tumours. The percent of complications of stereotactic biopsy performed for diagnosis verification is also higher (on the order of 50%). Mainly, it is haemorrhagic infiltration of the tumour stroma, provoked by stereotaxis. In these conditions, the diagnosis of CNS lymphoma on the basis of non-invasive methods of examination, such as MRI with contrast enhancement strengthening and CT perfusion, capable of a high degree of probability to assume the lymphoma presence and avoid direct surgical intervention, is an extremely important issue.
Recently, the conservative methods of chemotherapy or its combination with target radiotherapy have become more widespread. In many cases, their use achieves stable remission and tumour regression even if the original tumour is of large size (Figs. 4.150, 4.151). Nevertheless, there are some lymphomas with rare structure that are characterised by swift growth and are resistant to standard-scheme chemo- and radiotherapies (Fig. 4.152). Differential diagnosis should be performed between lymphoma and highly malignant glioma (first of all with glioblastoma and AA), abscess, toxoplasmosis, progressive multifocal leukoencephalopathy, metastases, neurosarcoidosis and system lymphoma.
4.7
Metastatic Tumours
Every year the number of patients in oncology steadily grows; thus, the death rate from malignant tumours occupies a steady second place in the world, after cardiovascular diseases. In Russia about 600,000 patients die annually from tumours. The incidence of intracranial metastatic lesions is relatively high. According to literary data, it fluctuates from 4 to 37%, making up about 24% of all patients who die from cancer, and according to some authors, its share reaches 50% of all intracranial tumours (Earle 1955; Osborn 2004). Although metastases can be observed at any age, more often they are found in elderly patients, and more than 75% of patients are in the age range of 45–70 years. Metastases are mainly located in subcortical areas but can be revealed in any department of white substance, both in supra-and infratentorial areas, the subarachnoid space, around the sellar area, ventricular system and they can have extracranial locations. The clinical symptoms depend on metastasis location, level of brain tissue destruction and the intensity of perifocal oedema. The histological characteristics of metastatic tumours are extremely varied. The microscopic picture of a metastasis can resemble a structure of a primary tumour, but sometimes it is not possible even to find any histological attributes that would enable classification of the process. Lung carcinoma is one of their most frequent sources of a brain metastases—up to 50% of patients with this tumour have such metastases. Skin melanoma is the second frequent source of brain metastases. According to radiological attributes, the patients with melanoma have brain metastases in 30–40% of cases, and according to autopsy results of this category of patients, brain lesions are found in up to 80% of all cases. Breast cancer is second (18–30%). Other tumours that can metastasise into the brain
Table 4.1 Average values of ADC for brain lymphoma b
Tumour stroma
Necrotic area
Area of oedema
Intact white matter
500
0.95 ± 0.23
1.81 ± 0.31
2.04 ± 0.19
0.83 ± 0.04
1000
0.83 ± 0.2
1.73 ± 0.28
1.87 ± 0.11
0.78 ± 0.02
Supratentorial Tumours
441
Fig. 4.148a–f Lymphoma of the right temporal lobe adjacent to cavernous sinus and greater wing of sphenoid bone imitates meningioma.
T2-weighted image (a), T1-weighted image (b) image with contrast enhancement and DWI (b = 500) (c), (b = 1000) (d). ADC maps: based on the value of b (e,f) Table 4.2 Average values of the ratios of main metabolites to the
value of the reference peak of Cr in lymphoma stroma
a
a
Metabolites
Ratio
NAA–Cr
1.75 ± 0.28
Cho–Cr
1.60 ± 0.20
mI–Cr
0.72 ± 0.16
Lac–Cr
1.95 ± 0.77
NAA–Cho
1.09 ± 0.11
Valus are ± standard deviation
Table 4.3 Average values of main parameters CT perfusion in the stroma of lymphoma Perfusion parameters
CBV (ml/100 g)
CBF(ml/100 g/min)
MTT (s)
Lymphoma
2.93 ± 0.91
16.38 ± 3.87
6.06 ± 3.70
Intact white tissue
2.0 ± 1.1
25 ± 11.3
5 ± 2.1
442
Fig. 4.149a–f Lymphoma of corpus callosum. CECT (a), MRI with
gadolinium (b) demonstrate a lesion with heterogeneous structure. CT perfusion (c–f) examination: CBV map (c), CBF map (d), MTT
Chapter 4
map (e) and permeability map (f) show low blood volume and blood flow parameters, elongation of MTT and the increase permeability values Fig. 4.150a,b Lymphoma of genu of corpus callosum. CT with contrast enhancement before (a) and after (b) chemo- and radio therapy course. The full regression of tumour is seen
Supratentorial Tumours
Fig. 4.151a–i Lymphoma of genu of corpus callosum. T2-weighted images (a), T1-weighted images before (b), and after (c,d) contrast enhancement detect typical for lymphoma MR signal characteristics. On DWI (e) the signal of a tumour is lower than those from
443
brain. After chemo- and radiotherapy T2-weighted image (f) and T1weighted image (g,h) image show complete improvement. The perifocal oedema remains on DWI on the site of tumour, and there is an area of gliosis (i)
444
Chapter 4
Fig. 4.152a–h Multiple lymphomas of the
left cerebral hemisphere. T2-weighted image (a) and T1-weighted image (b) with CE detect two tumour nodes; one of them is of large size and lies paraventricularly near the left posterior horn. CT (c) with contrast enhancement on the level of large node demonstrates its relatively homogeneous contrast accumulation. CT perfusion (CBF) (d) identifies low-blood-flow parameters in tumour tissue compared with grey matter. CT (e–h) 2 months since the beginning of repeated chemotherapy courses reveals the tumour increase, spreading of perifocal oedema, the increase dislocation of the ventricular system and appearance of metastases into the ventricle system
Supratentorial Tumours
445
are those of kidneys and thyroid gland, and the gastrointestinal tract (Osborn 2004). In most cases, metastases are multiple; however, a solitary node can be met in 30% of observations; the latter is inherent to metastases of melanoma, lung and breast cancer. The haematogenic dissemination is typical for intracranial metastases from visceral organs and the lymph system plays a certain role. Macroscopically metastases are well-outlined, round formations. Necrosis and haemorrhage in central parts are frequently observed. Perifocal oedema is a typical feature for the majority of metastatic foci; it can surround even small nodes. Relatively metastasis itself cannot be detected with the use of CT and MRI; however, it may be accompanied by intense oedema and dislocation of the middle structures. Diagnosis of intracranial parenchymatous metastases is mainly based on CT and MRI. Direct cerebral angiography now plays a much less significant role (Fig. 4.153). The majority of metastases are hypodense on CT images without contrast enhancement. Only in cases of the presence of haemorrhagic, and calcified and high protein inclusions are metastases hyperdense on CT (Fig. 4.154–4.157). Calcium deposits can
be detected in metastases originating from adenocarcinoma of the colon, stomach, ovaries, lungs, and osteosarcoma and chondrosarcoma. Often the density of a metastasis on CT is equal to brain density, but nevertheless, it can well be detected on a background of surrounding oedema. Often after contrast administration, the metastasis begins to look on CT like a ring (the so-called crown effect), with the hyperdense periphery due to presence of necrosis or a cyst in the tumour’s centre and a rich capillary net on the periphery. Different CT variants of the ring-shaped form metastases can be observed: round, oval, in the form of a spiral, half-spiral, of uneven form, and so forth, with sites of small haemorrhages inside necrotic area, which have higher density. Metastases with more homogeneous structure can also be observed (Figs. 4.158–4.161). The presence of the multiple metastases increases the possibility of setting the diagnosis of metastatic lesions. Fortyfive percent of the patients under our observation had multiple metastases. More frequently, they were scattered in the brain without any order. In almost every case, their densities increased after contrast administration. Metastases can be of
Fig. 4.153a–f Metastasis of melanoma in right temporal area. Carotid angiograms in arterial and capillary phases (a–c): the tumour node with abundant vascular net and draining vein is detected. CT (d) with contrast enhancement demonstrates the tumour of
ring-shaped form of a convex location. T2-weighted image (e) and T1-weighted image (f) with contrast enhancement provide the additional information about the structure of tumour node and the statement of neighbouring brain structures
446
Chapter 4
Fig. 4.154a–f Multiple brain metastases. CT before (a–c) and after (d–f) contrast enhancement. The multiple tumour nodes of solid structure with intense contrast accumulation are better detected with background of oedema after CE
Supratentorial Tumours
447
Fig. 4.155a–f Multiple brain metastases. CT after contrast enhancement (a–c) detects two mass lesions located in the occipital lobe. The structure of their metastases is better seen after contrast enhancement (d–f)
448
Chapter 4
Fig. 4.156a–f Brain metastases. CT (a–c) and after (d–f) contrast enhancement. The two metastatic nodes are detected with intense contrast
accumulation in the shape of a thin rim. Tumours have area of central necrosis with the sedimentation phenomenon
Fig. 4.157a–c Multiple brain metastases of pancreatic cancer. CT af-
ter contrast enhancement (a–c) shows the multiple tumour nodes in the form of cysts with capsules that slightly accumulate contrast, in which there are many small calcifications that require the differential
diagnosis with parasitic brain lesion. Perifocal oedema is absent, even around a large tumour cyst in the left hemisphere of cerebellum
Supratentorial Tumours
449
Fig. 4.158a–c Multiple brain metastases of lung cancer. CT with (a–c) contrast enhancement. Small tumoral nodes with intense contrast accumulation and perifocal oedema are detected
Fig. 4.159a–c The solitary metastasis in right occipital area. CT with contrast enhancement in three projections (a–c) revaels the small tu-
mour node with necrosis and surrounding prominent area of perifocal oedema
Fig. 4.160a–c The solitary metastases in the left frontal area. CT with contrast enhancement in three projections demonstrates a large tumour node with necrotic foci surrounded by wide area of perifocal oedema, with the dislocation of middle structures (a–c)
450
Chapter 4
Fig. 4.161a–c Metastases in frontal areas. CT with contrast enhancement in three projections shows two large tumour nodes with central
necrosis. Perifocal oedema is hypodense (a–c)
any size, from small plentiful, scattered ones, to large nodes of increased density or ring-shaped form. Not infrequently can a patient have metastases at various stages of development: hyperdense, homogeneous and with areas of necrosis. Studies have proved that MRI, especially with contrast administration, is a more informative method in comparison with CT. With the use of MRI, metastatic foci can be better visualised on T2 and FLAIR sequences. Despite the fact that it is isointense with the brain tissue on T1 and T2 sequences, perifocal oedema can well outline the lesion zone. On T1-weighted images metastases, with the exception of those originated from melanoma, are iso- or hypointense in comparison with the white matter, and they are virtually not visualised if their sizes are less than 1 cm. The central necrosis, hypointense on T1 sequence and hyperintense on T2-weighted scans, can be found in metastatic tumours regardless of their size (Figs. 4.162–4.165). Sometimes metastases can be without perifocal
oedema, or with minimal oedema in comparison with the size of the tumour itself (Figs. 4.166–4.168). In cases of melanoma, it is possible to reveal non-haemorrhagic metastasis in the form of a hyperintense area on T1-weighted scans or iso- and hypointense on T2 images, due to the paramagnetic effect inherent for tumour and caused by the presence of melanin. To prove this, we consider metastases of melanoma that do not contain melanin. The MR signs of these tumours are similar to other non-haemorrhagic metastases; they are hypointense on T1-weighted images and hyperintense on T2 (Figs. 4.169, 4.170). In the majority of observations, contrast enhancement leads to increase of signal from tumour, and that betters describes the number of nodes and their locations. The quality and reliability of metastases diagnosis located in posterior cranial fossa, and in basal departments of temporal and frontal lobes, improves. Contrast enhancement improves the specificity of
Fig. 4.162a–c Multiple brain metastases of breast cancer of supra-
mour nodes of solid structure with MR characteristics close to brain are visualised. Contrast medium accumulation is intense and homogeneous
and infratentorial locations. T2-weighted images (a) and T1-weighted images before (b) and after (c) contrast enhancement. The two tu-
Supratentorial Tumours
Fig. 4.163a–f Multiple metastases of uterus cancer of supratentorial location. T2-weighted images (a,b) and T1-weighted images before (c) and after (d–f) contrast enhancement. The tumour nodes of uneven structure with the presence of necrotic cavities in two small nodes are demonstrated. Metastases are hyperintense on T2- and hypointense on T1-weighted images. The contrast accumulation is intense and heterogeneous, with the exception of nodules in medial parts of left frontal area
451
452
Chapter 4
Fig. 4.164a–f Sole metastasis in the left frontal area. CT with contrast enhancement (a) detects tumour node with contrast accumulation in the shape of a thin ring; perifocal oedema is prominent. MRI: T2-weighted imaging (b), T1-weighted imaging (c) and FLAIR (d)
detect tumour nodes with thin capsules and central necrosis. MR signal from the solid part of metastasis is hyperintense on FLAIR. Contrast enhancement clearly demonstrates the structure of tumour node (e,f)
Fig. 4.165a–c Two metastases of lung cancer of supra- and subten-
surrounded by perifocal oedema; the second is located in superior vermis of cerebellum and has hyperintense signal on T2-weighted image due to intratumoral haemorrhage
torial location. T2-weighted image (a), FLAIR (b) and T1-weighted image with contrast enhancement (c). Tumour node in the left parietal area has solid structure, intense contrast accumulation and is
Supratentorial Tumours
453
Fig. 4.166a–c Multiple metastases of pancreatic cancer of supratentorial location. T2-weighted image (a) and T1-weighted images with contrast enhancement (b,c). The two tumour nodes of cystic structure with separate micronodes in walls are detected in both parietal areas. Contrast accumulation is moderate, perifocal oedema is absent
Fig. 4.167a–c Multiple metastases of sub- and supratentorial loca-
tions. T2-weighted images (a,b) and T1-weighted image with contrast enhancement (c). Multiple tumour nodes with central necrosis
regardless of size are detected. Contrast accumulation is moderate and has peripheral type; perifocal oedema is visualised only around the giant node in the left frontal area
454
Chapter 4
Supratentorial Tumours
455
9 Fig. 4.168a–l Solitary metastasis of uterus tumour in the right occipitoparietal area. T2-weighted images (a,b) FLAIR (c,d) and T1-weighted images before (e,f) and after (g–l) contrast enhancement demonstrate the tumour of a giant size with haemorrhagic and necrotic components. Perifocal oedema is virtually absent
Fig. 4.169a–c Metastasis of melanoma in the right frontal area. T2weighted image (a), T1-weighted image (b) and T2*-weighted image (c). The giant tumoral node with foci of subacute haemorrhages (hyperintense MR signal on T2- and T1-weighted image) is revealed,
perifocal oedema is moderate and the decrease of MR signal on T2*weighted image is observed due to the presence of melanin and acute haemorrhages
456
Fig. 4.170a–c Metastasis of melanoma in the left temporal area. T2-weighted image (a) and T1-weighted images before (b) and after (c) contrast enhancement. The tumour node with foci of subacute haemorrhages and melanin deposits (hyperintense MR signal on T1-
Chapter 4
weighted image) is revealed. A haemorrhagic cyst is on the anterior contour; the solid section of tumour is hypointense on T2-weighted image. The perifocal oedema is moderate
Fig. 4.171a–f Multiple metastases of sub- and supratentorial locations. T2-weighted images (a,b) and T1-weighted images before (c) and after
(d–f) contrast enhancement detect multiple tumoral nodes with central necrosis regardless of size. Contrast accumulation is moderate and of peripheral type
Supratentorial Tumours
MRI diagnosis in differentiation of solitary subcortical metastasis and lacunar strokes. The latter do not enhance contrast. The use of double- and triple-dose of MR contrast demonstarte additional metastatic lesions, wich are poorly visible at standard doses (Figs. 4.171–4.174). Sometimes haemorrhage can occur in metastasis, and it fills most of the tumour node. In these cases, differential diagnosis with haematomas is especially complex. Contrast accumulation helps to differentiate the neoplasm (on the basis of additional signal increase on T1 sequence) from haemorrhage (Figs. 4.175, 4.176). Moreover, metastases should be differentiated from malignant glioma, abscess, granuloma, parasitic cysts, meningioma, ischaemic stroke, neurinoma of third nerve, radiation necrosis, adenoma of hypophysis, progressive multifocal leukoencephalopathy (after chemotherapy or immunosuppressive therapy) and multiple sclerosis in the acute stage. At the same time, it is necessary to keep in mind that sometimes, especially in an initial stage, metastases do not have any clinical signs and symptoms. In fact, 8% of patients with the confirmed diagnosis of a lung cancer have so-called mute brain metastases (the metastases were not revealed with the
457
use of clinical and radioisotopic examinations) detected by MRI with contrast enhancement. Numerous attempts to develop classification of metastases on the basis of CT and MRI images depend on the primary sources of metastases; however, the presence of many exceptions and contradictions are typical for such classifications. On the basis of our studies and constant consultations provided to patients with oncology, we determined that a brain metastasis from practically any organ can have similar characteristics and configuration; therefore, to try to find the location and character of a primary tumour on the basis of the metastasis shape on standard CT and MRI is unfeasible (Fig. 4.177). It is possible that more informative methods of examination, such as proton and phosphorus MRS and CT perfusion, could partly solve the problem of finding the primary origin. MRI with 1H MRS and perfusion MRI in patients with metastases and glioma demonstrate that spectral values in an area of oedema in a border zone with a tumour are different in the aforementioned tumours; however, a convincing correlation has not been found (Law and Cha 2002). Many authors believe that the infiltration of tumour cells into brain tissue is possible, and this infiltration differs and has different signs in
Fig. 4.172a–f Multiple metastases of sub- and supratentorial location. T1-weighted images (a–f) with triple dose of contrast substance detects multiple tumoral nodes of solid structure. Even small nodes less than 5 mm in diameter are clearly visualised
458
Chapter 4
Fig. 4.173a–f Multiple metastases of breast cancer of sub- and supratentorial location. T2-weighted images (a–c) and T1-weighted image
(d–f) with double dose of contrast substance detect multiple tumour nodes. The small tumour nodes in white matter and arachnoids are clearly visualised
Fig. 4.174a–c Multiple brain metastases of breast cancer. T2-weighted image (a), T1-weighted images before (b) and with (c) contrast en-
hancement with triple dose of contrast medium detect multiple tumour nodes disseminated in white matter
Supratentorial Tumours
Fig. 4.175a–f Solitary metastasis in the left frontal area with massive haemorrhage. T2-weighted imaging (a) and T1-weighted imaging (b) detect large tumour node with haemorrhagic subacute component (hyperintense MR signal on T1-weighted image). After contrast
459
enhancement (c–e), the area of contrast accumulation around the haemorrhage is additionally visualised. On DWI (f) MR signal is heterogeneous—the hyperintense signal from acute haemorrhage
Fig. 4.176a–c Multiple metastases in subtentorial area. T2-weighted image (a) and T1-weighted images before (b) and with contrast enhance-
ment (c) detect multiple tumour nodes of cystic structure with a haemorrhagic component and the sedimentation phenomenon
460
Chapter 4
Fig. 4.177a–f Variants of MR images of brain metastases of lung cancer: cystic subtentorial (a), solid with minimal oedema (b), of mixed structure (c), multiple solid with prominent oedema (d), mixed structure without oedema (e) and multiple with central necrosis (f)
Table 4.4 Average values ± standard deviations for metabolite ratios
in MR spectrums of metastases
a
a
Metabolites
Ratio
NAA–Cr
1.71 ± 0.37
Cho–Cr
2.82 ± 0.37
mI–Cr
1.47 ± 0.37
Lac–Cr
8.82 ± 1.47
Values are ± standard deviation
Supratentorial Tumours
461
Fig. 4.178a–d Brain metastases of lung cancer. Case 1. Lung cancer metastasis in the parasagittal left frontoparietal area. T1-weighted image with contrast enhancement (a). MRS (b) demonstrates the increase of the Lac–Lip complex peak; the other peaks are reduced. Case 2. Metastasis of kidney cancer in right hemisphere of cerebellum. T1-weighted image with contrast enhancement (c). MRS demonstrates the identical spectral changes (d)
cases of glioblastoma and metastasis. The analysis of spectroscopic examination results of 22 patients demonstrated that in cases of absence of a solid tumour component, the ratio of metabolites in a disintegration zone is similar to those of a malignant glioma: a moderate decrease of NAA and mI peaks, sharp increase of Lip–Lac complex (peak) and moderate increase of the Cho peak (Table 4.4). Spectroscopic parameters of metastases of a various nature unfortunately have a high degree of overlapping, and as a whole they are not specific, which does not allow use of MRS (at least now) for identification of the primary source of a brain lesion (Fig. 4.178). MR perfusion of metastases of various aetiologies demonstrates that values of rCBV in metastases originating from melanoma are lower than in metastases originating from kidney cancer (5.35 ± 2.32 and 8.17 ± 2.39 ml/100 g, respectively); however, both of them considerably exceeded rCBV values of astrocytoma (2.61 ± 1.17 ml/100 g) and lung cancer (2.94±0.86 ml/100 g) (Kremer and Grand 2003). In our institute, after studying CT perfusion parameters in 26 patients with metastatic brain lesions, we obtained results that testify preliminarily about the higher specificity of this method in an evaluation of structure of metastasis and perifocal area that surrounds the lesion. The values of CBV in tissue of metastases of various origins are presented in Fig. 4.179.
Fig. 4.179 Parameters of rCBV in tissues of metastases of various
origins
462
Chapter 4
The highest values of CBV were observed in the solid potions of kidney cancer metastasis. They are often presented by a solid unit with homogeneous contrast enhancement, and they rarely have central necrotic changes; however, when present, the intensity of such changes prevails over a solid portion. Kidney metastases grow slowly; however, quite often they cause intense perifocal oedema. The visual picture of kidney cancer metastases is very similar to those of intestines—the thick cushion of a solid section and a small site of disintegration. In a diffusion examination, metastatic tumours are characterised by heterogeneous changes on DWI and ADC maps. Solid nodes usually have hyperintense and homogeneous MR signal on DWI and ADC values that are reliably lower than are ADC of glial tumours. In cases of the presence of necrotic centres, they are virtually identical to glioblastoma (Table 4.5). Unlike glial tumours, metastases have lower DWI signal in an area of oedema, which is most likely related to the more dense structure of a brain tissue, and less free movement of water molecules in extracellular space around a tumour node.
Table 4.5 Average values of DWI in brain metastases
a
Area of interest
Acquired ADC values
Tumour stroma
0.79 ± 0.24–1.15 ± 0.2
Peritumoral zone
1.28 ± 0.2
Area of vasogenic oedema
1.22 ± 0.2
a
Values are n × 10–3mm2/s
Fig. 4.180a–c Lung cancer metastasis into the left occipital lobe. T2-weighted image (a) shows an area of pathologically hyperintense MR signal in the projection of occipital lobe. After contrast enhancement, the small metastasis of a ring shape is detected in occipital lobe
DWI sometimes helps to differentiate concomitant brain disorders (Fig. 4.180) as well as to assess the extent and character of brain oedema (Fig. 4.181). Diffusion tensor imaging, according to Lu and Ahn (2003), may also be informative in diagnosis of metastases and gliomas. Differences in ADC in the perifocal oedema area were registered, confirming the different extent of diffusion of water molecules and of tumour infiltration of adjacent tissues. In addition, expansive growth of metastasis creates dislocation of adjacent pathways, whereas gliomas destroy them. PET is more widely used nowadays and may be included in the diagnostic algorithm in general oncology to better ascertain the location of primary tumour, to assess the extent of dissemination of tumour in the human organism and to detect brain metastases before operation. According to the Burdenko Neurosurgical Institute, in 2001–2005, precision of primary tumour diagnosis increased several times (Dolgushin et al. 2004). The complex approach of diagnosis decreases the percent of non-detectability of a primary tumour from 51 to 7% (Fig. 4.182). Despite of its overt averages, PET has a spectrum of limitations that do not allow to use it as a screening technique. First of all, the technique is costly—elaboration of radiopharmacological medium, its transport and usage require additional staff. The technique requires a long time; there are limitations for some concomitant conditions (diabetes mellitus), which also narrow the technique facilities. MRI of the whole body using standard sequences has similar limitations, and moreover, requires double scanning with contrast enhancement. One of the most rapid sequences of MRI is a DWI. Inflammatory tissue and malignant tumours have small ADC values due to larger sizes of cells and, hence, less diffusing molecules
(b). On DWI (c) an area of hyperintense MR signal on T2-weighted imaging corresponds to a focus of ischaemia in the territory of left PMA and is not an vasogenic oedema around metastasis focus
Supratentorial Tumours
Fig. 4.181a–f Solitary metastasis of kidney cancer into the left frontal area. T1-weighted imaging with contrast enhancement (a), FLAIR (b) and T2-weighted imaging (c) show the tumoral node of a solid
463
structure surrounded by prominent perifocal oedema. On DWI (b = 500) (d) and (b = 1000) (e) the perifocal oedema is of vasogenic origin. MRS (f) detects high a Lac–Lip complex peak
464
Fig. 4.182a,b Case 1 (a). Multiple brain metastases of colon cancer.
T1-weighted imaging with contrast enhancement detects tumoral nodes with intense and homogeneous contrast accumulation. PET examination of the entire body reveals multiple foci of pathological accumulation of radiopharmacological substance (18F-fluorodeoxyglucose): large focus in the projection of sigmoid colon and foci of lesser size in the projection of lung roots and mediastinum (me-
of water per time unit in the extracellular space (Takahara et al. 2004; Nemeth et al. 2007). On DWI, tumour cells are more hyperintense. After processing procedures of the acquired axial sections with 4- to 8-mm space reformers, MIP or MRP (multiplanar reformat) acquire 3D images. DWI of the whole body obtains PET-like images of suspected regions affected by the tumour. Taking into account the time needed to perform this investigation and its cost, DWI can be applied as a screening method. In addition, DWI allows monitoring the dynamic changes of the lesions previously revealed by PET (Fig. 4.183). One of the mechanisms of metastatic dissemination of cerebral and spinal tumours is dissemination via CSF pathways. In these cases, lesions may be solitary or multiple; the latter is characteristic for medulloblastomas, AA, glioblastomas and pineoblastoma. In addition, metastatic meningeal dissemination is typical for extracerebral tumours—lung adenocarcinoma, breast cancer, stomach cancer and melanoma; the latter is possible due to connections between earlier formed tumour nodes and CSF spaces (Figs. 4.184, 4.185). Metastatic dissemination may be selective (only brain or spinal cord are affected) or total (Fig. 4.186). It is important to detect precisely how metastatic dissemination is distributed throughout the body, as it determines treatment tactics in most cases. Contrast enhancement with gadolinium chelates in MRI of the spinal cord may be a novel helpful tool. In our opinion, MRI exceeds CT ant CT myelography in getting more reliable information about a metastatic process in spinal meninges.
Chapter 4
tastasis). Case 2 (b). Lung cancer metastasis in the posterior cranial fossa. T1-weighted image with contrast enhancement detects the tumour node with intense heterogeneous contrast accumulation. PET examination of the entire body reveals the wide focus of pathological accumulation of isotope in the root of left lung and small focus in mediastinum (metastases)
4.8
Supratentorial Cysts
Primary intracranial cysts include a group of mass cystic lesions of various aetiology and structure.
4.8.1 Cysts Considered a Normal Anatomical Variant Those cysts in dilatated perivascular Robin-Virchow spaces are considered normal variants.
4.8.2 Congenital Cysts Congenital cysts include dermoid, epidermoid, arachnoid, septum pellucidum (the fifth ventricle) and those of Verge’s ventricle (the “sixth” ventricle).
4.8.3 Cysts of Endoderm and Ectoderm Origin Cysts of endoderm and ectoderm origin include colloid, entodermal (associated with axial deformities) and those of Ratke’s cleft are included in this category.
4.8.4 Mixed Cysts Neuroglial, ependymal, porencephalic, choroid plexus (xanthogranulomas) and pineal gland cysts comprise this group.
Supratentorial Tumours
Fig. 4.183a–c Metastasis of lung cancer in the brain. CT image with
465
CE (a) demonstrates the lesion in the left temporal lobe, surrounded by perifocal oedema. Whole-body DWI reveals the large region of in-
crease diffusion in central part of left lung. There are multiple affected lymph nodes (metastases) in the lung’s root on the right (b). PET with 18F-fluorodeoxyglucose confirms the data obtained by MRI (c)
Fig. 4.184a–c Multiple lung cancer metastases of intracranial and intravertebral locations. T1-weighted imaging with contrast enhancement detects multiple tumour nodes spreading to the tentorium of
the cerebellum and cisterns at the base of brain (a,b). The examination of thoracic spine (c) shows the small foci of contrast accumulation along the subarachnoid membranes of spinal cord
466
Chapter 4
Fig. 4.185a–c Multiple brain metastases. MRI after contrast enhancement reveals small multiple tumour nodes (a–c), with the involvement
of the cisternal part of the left facial nerve
Fig. 4.186a–f Multiple intracranial and calvarium metastases. FLAIR
imaging (a) detects multiple tumour nodes of supra- and subtentorial locations, surrounded by perifocal oedema. The tumour lesion
of left parietal bone is visualised additionally. T1-weighted image with contrast enhancement in axial (b–e) and sagittal (f) projections demonstrates that the majority of metastases have cystic structure
Supratentorial Tumours
Several types of cysts will be discussed in the appropriate chapters. Below we discuss rare intracranial hemispheric cysts.
4.8.5 Dilatated Perivascular Robin-Virchow Spaces Perivascular spaces (PS) known also as Robin-Virchow spaces, are linear areas filled with interstitial fluid and accompany the penetrating cerebral arteries and arterioles. The aetiology is still unexplained. They may be encountered in arterial hypertension, migraine, seizures, parkinsonism and several storage diseases (mucopolysaccaridoses). Mostly, they are an occasional finding on cerebral MRI. Recent studies, including experimental ones, showed that PS are structurally and functionally complex cerebral units, more complex than was previously thought (Salzman et al. 2005). PS may dilatate, causing mass effect and acquiring of peculiar shapes. Differential diagnosis in these cases should be made between lacunar strokes, cystic tumours and infectious/inflammatory cysts. Dilatated PS are the most frequent intracranial cysts of non-tumour origin. They may be visualised in all patients on 3-T MRI. Dilated PS may be found in all age groups, and they may be identified in 25–30% of children. Typically, they are 5 mm in size. Marked dilatation of PS may sometimes occur; the latter are usually seen in adults in the projection of the midbrain. PS are localised along the lenticulostriatal arteries, above the superior perforated lamina and near the anterior commissure. Less often they are located along the arteries that penetrate grey matter, and they may penetrate deeply into the white matter. Subinsular PS have been described, as well as PS in dentate nuclei and cerebellar hemispheres, in midbrain, corpus callosum and cingulated gyrus. Neuroimaging features of PS are well described in the literature. Usually they are round-shaped masses with clear external and internal contours located along the cerebral perforating arteries. PS have neuroimaging patterns (CT and MRI) identical to ventricular and subarachnoid CSF (Figs. 4.187, 4.188). Contrast enhancement is absent; neither calcifications in the walls nor perifocal oedema are present. On T2-weighted imaging, mild hyperintensity within the brain tissue adjacent to PS may be seen (Fig. 4.189). Giant PS cause mass effect to surrounding brain. As the most frequent location of PS is midbrain, compression of CSF spaces and of the aqueduct of Sylvius may occur (Fig. 4.190).
4.8.6 Epidermoid Cyst (Cholesteatoma) Epidermoid cysts (EC) are rare mass intracranial lesions seen in 1.8% of cases. They are diagnosed six to eight times more frequently than are dermoid cysts. EC may be congenital or acquired. Congenital EC are usually intradural and are located at the brain base (up to 90%). In addition, 40–50% of EC are found in the cerebellopontine angle, taking third place in frequency after meningiomas and neurinomas for this site.
467
Other sites are the fourth ventricle (17%), and the parasellar region and the middle cerebral fossa (10–15%). Exceptionally rare (1.5%) EC are found in cerebral hemispheres, brainstem or temporal horn choroids plexus. Extradural EC (10%) may be located in the frontal, parietal, occipital and sphenoid bones; also they may be found intraventricularly. Acquired EC often have traumatic origin, when epidermis penetrates deeply, and that leads to formation of a cyst lined with desquamated epithelium. They are diagnosed less often than the congenital ones. The most frequent age of diagnosis is 40 years. X-ray craniograms reveal a clear-cut area of destruction which is round and has sclerotic borders. CT reveals a roundshaped mass lesion hypodense in 95% of cases, almost identical to CSF density. In some cases, density reaches 30 HU. In 15–25% of cases, calcifications are seen on the cyst periphery or in its stroma. If cranial bones are involved, a clear-cut area of bone destruction is seen. Reports exist about EC with high density on CT. Contrast enhancement is typically absent. MR features of EC are more variable than those of CT. In general, congenital or acquired EC resemble each other in their imaging features. On Т1-weighted imaging, EC have heterogeneous moderately increased signal, more intense on periphery than in the centre, compared with CSF. In some cases, the signal of EC may exceed that of brain tissue (so-called white epidermoids). This is explained by high triglyceride and fatty acids content (Fig. 4.191). On Т2-weighted imaging EC looks iso- or hyperintense in relation to CSF in subarachnoid spaces. Hypointense lesions are mostly represented by calcifications and areas with high-protein content. On FLAIR images, EC signal does not differ from that of CSF, and areas of hyperintense signal may be present. DWI is very sensitive in primary EC diagnosis. On DWI, cholesteatomas produce markedly hyperintense signal in all b values. DWI has become almost a singly reliable technique for postsurgical assessment of the extent of radical excision, as it clearly defines the cyst remnants on the background of postsurgical changes. The differential diagnosis should be made between arachnoid cysts, parasitic cysts (neurocysticercosis, echinococcosis, etc.), cystic tumours and dermoid cysts.
4.8.7 Colloid Cyst of the Third Ventricle Colloid cysts comprise 0.5–3% of all brain tumours and are dysembryonic in origin. They occur due to lacing of the socalled paraphysis elements—it is an embryonic structure that is represented by a strand between telencephalon and the anterior portions of diencephalon (Konovalov et al.1997). Colloid cyst is diagnosed mainly between the ages of 30 and 40 years. Observations in children comprise only 8% of cases. Colloid cysts are seen in 15–20% of all cases of intraventricular mass lesions. They are round-shaped masses with regular borders, located within the foramina of Monroe. Colloid cysts cause hydrocephalus, with signs of raised intracranial pressure. Clinical presentation is limited to signs of obstructive hydrocephalus. Initially, signs of recurrent occlusion of the
468
Chapter 4
Fig. 4.187a–c Perivascular brain spaces. T2-weighted imaging (a,b) and T1-weighted imaging (c) detect multiple small foci of hyperintense signal (T2-weighted imaging) and hypointense (T1-weighted imaging). On axial scans, the perivascular spaces in subcortical white matter are oriented along the course of perforating vessels
Fig. 4.188a–c Perivascular brain spaces. T2-weighted imaging (a,c) and T1-weighted imaging (b) demonstrate the small cysts in the projection of the temporal lobes with MR characteristics identical to those of the CSF in the lateral ventricles
Supratentorial Tumours
469
Fig. 4.189a–c Perivascular brain spaces. T2-weighted imaging (a) and T1-weighted imaging (b,c) detect multiple small foci of MR signal change in white matter, with the same signal in comparison with CSF. An area of hyperintense MR signal on T2-weighted image (arrows) is visualised around separate perivascular spaces
Fig. 4.190a–f Perivascular brain spaces in the projection of midbrain.
On T2-weighted images (a), T1-weighted images (b) and FLAIR (c) images, the multiple cystic formations blending into one large cyst are visualised in the projection of right peduncle of midbrain. MR
signal from cysts is identical to those from the CSF, including the myelography mode (f). Contrast accumulation is absent in cystic cavities and surrounding brain tissue (d,e)
470
Fig. 4.191a–i Epidermoid cyst of right temporal area. Craniograms (a,b) reveal an area of bone destruction, with clear contours. CT before (c) and after (d) contrast enhancement detects the hypodense lesion in right temporal area, without enhancement after contrast injection. The accompanying bone changes are visualised (e). The
Chapter 4
lesion is characterised by the relatively homogeneous hyperintense MR signal on the T2-weighted image (f). MR signal is more heterogeneous on the T1-weighted image (g)—the combination of areas of hyperintense and hypointense MR signal. The epidermoid cyst has bright MR signal on DWI (b = 500) (h) and (b = 1000) (i)
Supratentorial Tumours
CSF pathways are observed, such as hypertensive crisis, which may be severe and even fatal. On microscopy, a cyst appears as a thin-walled formation located near the fornix or the foramina of Monroe, or attached to choroid plexus or adjacent structures. The size of a colloid cyst varies from 0.3 to 3–4 сm. Among 51 patients who underwent surgery in the Burdenko Neurosurgical Institute, a cyst 52 mm in size was diagnosed. A colloid cyst has a viscous, greenish-yellow content. The internal wall consists of a single layer of cylindrical epithelium producing mucin. Colloid cysts are slowly growing mass lesions. After their total excision, no relapses are usually seen, the CSF circulation is restored and hydrocephalus improves. On CT and MRI colloid cysts are round shaped, which distinguishes them from tumours of other histology. On CT, colloid cysts are hyperdense. However, there exist cases of iso- or hypodense non-enhancing colloid cysts (Figs. 4.192–4.194). The reason for hyperdensity is iodine, present in high concentration in the cyst contents. On Т1-weighted imaging, colloid cysts are usually iso- or (more frequently) hyperintense compared with brain tissue. On Т2-weighted imaging, the signal intensity of colloid cysts varies from low (even less than that of brain tissue) (Figs. 4.195, 4.196) to high, depending on mucin content (Armao et al. 2000). No contrast enhancement occurs within the cyst content or its walls after administration of contrast medium. Enhancement of septal veins is sometimes mistaken for the intrinsic enhancement of the cyst walls (Figs. 4.197, 4.198). MRI exceeds CT in diagnosis of colloid cysts, as in MRI many examination parameters may be modulated. However, in some observations colloid cysts were characterised by variable density on CT and intensity on MRI, which confirms our opinion that there are no absolutely specific diagnostic criteria of any histological form of tumours. The absence of contrast enhancement is considered a more important differ-
471
ential criterion, as it is not seen in tumours of identical location (often, pilocytic astrocytomas) (Figs. 4.199, 4.200).
4.8.8 Entodermal (Neuroenterogenic) Cysts Entodermal (neuroenterogenic) cysts are mass lesions lined inside with cylindrical epithelium containing goblet-shaped cells (Matsko and Korshunov 1998). These cysts are an exceptionally rare finding, both intracranially and intravertebrally. Rarely, they have intramedullary location. MR signal depends on the content of the cyst (the quantity of mucus and cellular elements). On Т1-weighted imaging, the signal of the cyst is higher than that of CSF. On Т2-weighted imaging, it may not differ from that of the surrounding subarachnoid spaces, and is better seen on FLAIR images and after myelography. Contrast enhancement is absent.
4.8.9 Neuroglial Cysts Neuroglial (synonymous with glioependymal) cysts are benign cysts with internal epithelial lining located in the brain, frequently in the paraventricular region. Several authors distinguish neuroglial and ependymal cysts, depending on cellular origin of the epithelial lining (Osborn 2004). This question is not yet resolved, and these cysts are discussed jointly. Predominant location of a neuroglial cyst is the frontal lobe. The cyst is several millimetres to several centimetres in size (in the former case, the cyst is hard to differentiated from PS). Ependymal cysts are often located in the lumen of the lateral ventricle or subependymally. They may reach 8–9 сm. On CT, the cyst appears as a clear-cut and round-shaped hypodense area. Its density is identical to that of the CSF. Contrast enhancement and calcifications are absent. On MRI, the
Fig. 4.192a–c Colloid cyst of the third ventricle. CT detects a round, hyperdense lesion in the projection of Monroe’s foramen (a). The
cyst has characteristics of MR signal close to those of brain on the T2-weighted image (b). The lesion is hyperintense on the T1-weighted image (c)
472
Chapter 4
Fig. 4.193a–c Colloid cyst of the third ventricle. CT detects a small, round, hyperdense lesion of a in the projection of Monroe’s foramen
(a–c). The cyst has hypointense MR signal on the T2-weighted image (d,f). On T1-weighted image the cyst is isointense (e,f)
Fig. 4.194a–c The colloid cyst of the third ventricle. CT reveals
isodense mass lesion of round shape in the projection of Monroe’s foramen (a). T2-weighted imaging (b) and T1-weighted imaging (c)
detect the cyst, which is visible only on the T1-weighted image as a focus of hyperintense MR signal. The lesion is isointense with the brain on the T2-weighted image
Supratentorial Tumours
473
Fig. 4.195a,b Colloid cyst of the third ventricle. T1-weighted imaging (a) and T2-weighted imaging (b) detect the mass lesion of a round
shape in the projection of Monroe’s foramen. The cyst is hyperintense on T1-weighted imaging and has a hypointense signal on T2-weighted imaging
Fig. 4.196a–c Colloid cyst of the third ventricle. T2-weighted imaging (a) and T1-weighted imaging (b,c) detect a small mass lesion of a round shape in the projection of Monro’es foramen. MR signal from cyst is hypointense in comparison with MR signal from brain tissue on T2-weighted imaging and isointense on T1-weighted imaging
474
Fig. 4.197a–c Colloid cyst of the third ventricle. T2-weighted imaging (a) detects the mass lesion of a round shape with homogeneous hypointense MR signal in the projection of Monroe’s foramen. The cyst is hyperintense on the T1-weighted image (b). Contrast enhance-
Chapter 4
ment (c) does not lead to increase in cyst brightness. The enhancement of internal brain vein located on the upper cyst contour is well detected (arrow)
Fig. 4.198a–c Colloid cysts of the third ventricle. T2-weighted imaging (a,b) detects a round mass lesion with heterogeneous MR signal in the projection of Monroe’ foramen. Contrast enhancement does not lead to increase in cyst brightness (c). Enhancement of the septal vein on the cyst periphery is well detected
Supratentorial Tumours
Fig. 4.199a–f PA of septum pellucidum. T2-weighted images (a) and
475
T1-weighted images before (b,c) and after (d–f) contrast enhancement show the mass lesion of a round shape in the projection of
anterior parts of septum pellucidum. There is occlusion of Monroe’s foramen and dilation of lateral ventricles. Tumour intensively accumulates contrast
Fig. 4.200a–c PA in the projection of Monroe’s foramen. T2-weighted image (a) and T1-weighted image before (b) and after (c) CE detect the mass lesion of a round shape in the projection of the right side
of Monroe’s foramen. The lateral ventricles are dilated. The tumour has hyperintense MR signal on T2-weighted image and accumulates contrast heterogeneously
476
signal of the cyst is almost identical to that of the CSF. In extraventricular or subependymal cysts, a wall of the cyst may be seen (Fig. 4.201). Contrast enhancement is absent, as on CT. Suggestive diagnosis is made taking into account the cyst location and long-term asymptomatic course. Multiplanar MRI exceeds CT in diagnostic sensitivity. Differential diagnosis should be made between an arachnoid cyst, a cyst of choroid plexus, EC, porencephaly and an asymmetrically dilated lateral ventricle (as a developmental variant). If the cyst is located within the brain tissue, then dilated PS and parasitic cysts should be ruled out.
4.8.10 Porencephalic Cysts A porencephalic cyst is a CSF cavity in the brain tissue. The term was coined for the first time by R. Heschle in 1856 to determine intracerebral cysts formed due to impairment of embryonic development. It usually communicates with the lateral ventricle or a subarachnoid space. Etiological factors are anoxia, injuries and infections that influence the developing brain postnatally. W. Penfield and T. Erickson in 1941 described the “locked” porencephaly caused, as they thought, by thrombosis or embolism of the middle cerebral artery branches. In the locked porencephaly, the cavity is not connected with the ventricle or the subarachnoid space. P .Yakovlev and R. Wadsworth in 1946 distinguished agenetic (developed before 6 months of intrauterine life) and encephaloclastic cysts (developed in the last trimester of pregnancy or after delivery). They differ in histology of the walls. Agenetic porencephaly is often combined with agenesia of corpus callosum. Our data show that porencephaly is seen in 4.5% of children with hydrocephalus. In almost half of cases, porencephaly is combined with other developmental defects. Posttraumatic porencephaly is a separate form seen after primary brain tissue destruction (contusion, haemorrhage) with subsequent rupture of the ventricular ependyma. In the latter, concomitant posttraumatic pathological changes are frequently seen. Porencephaly has no typical picture on X-ray craniograms. Hydrocephalus features may be seen, and sometimes outpouching of cranial bones on the affected side. Before CT implication, the most informative tool in porencephaly diagnosis was pneumoencephalography, which demonstrates the cavity itself and its communication with the CSF spaces. Angiographic features of congenital porencephaly are specific and depend on the developmental defects of cerebral tissue formation of a cavity with invaginated borders. Opercular abnormal vessels (operculation is an invagination of vessels with simultaneously invaginated cortex) and areas with no vessels are the criteria for diagnosis of congenital origin of the cyst. Porencephaly formed in the adult brain manifests on angiograms by areas without vessels, absence of operculation and dislocation of vessels appropriate to the location of the cyst. CT reveals a hypodense area (CSF density) with clear-cut contours, communicating with the lateral ventricle and/or subarachnoid space (Fig. 4.202). Walls do not show contrast enhancement, which is a differential criterion for ruling out abscesses and cystic tumours.
Chapter 4
CTVG reveals that a porencephalic cyst fills with contrast medium simultaneously with the ventricular system. On MRI, a porencephalic cavity looks like a clear-cut area of changed signal with CSF intensity on all sequences (Figs. 4.203, 4.204). On MRI, it is easy to detect the quality of the walls of these cysts (white or grey matter), which can determine the time of formation of a porencephalic cavity.
4.8.11 Cysts of the Choroid Plexus Cysts of choroid plexus are also called xanthogranulomas of the choroid plexus. They are usually small cysts located within the choroid plexus of the lateral ventricles. They are asymptomatic, and before the CT/MRI era, they were diagnosed only on autopsy. At present, they are seen almost only in adults. In neonates, they may be seen on Doppler cranial examination. They are frequently located within the lateral ventricles triangle, but occationally in the third ventricle. They are usually bilaterally 2–10 mm in size; cysts that exceed 2 mm in size are rare. On CT, the cyst itself is iso- or mildly hypodense. Calcium deposits are seen on the cyst periphery (Fig. 4.205). On Т1weighted imaging, the content of the cyst has mildly hyperintense signal compared with the surrounding CSF; on Т2weighted imaging, it is usually hyperintense, and on FLAIR images, the signal is heterogeneous. On DWI, restricted diffusion is seen in 60% of cases inside the cyst (high signal). Contrast enhancement may be absent or prominent, and is heterogeneous. Differential diagnosis should be made between choroid papilloma, parasitic and inflammatory cysts, intraventricular EC, lipoma of the choroid plexus (Fig. 4.206) and the features of Sturge-Weber syndrome (angiomatosis of choroid plexus with enlargement).
4.9
Eosinophilic Granuloma
According to WHO classification, eosinophilic granuloma (EG) is related to tumours. They are a benign disorder from the group of reticuloendothelial tumours and have a mild course. EG are frequent, however, statistical data is lacking. They usually occur in children and adolescents. Involvement of bones may be solitary or multiple. In half of cases, bone lesions are multiple and are disseminated throughout the skeleton. On follow-up X-ray craniography, it is possible to pursue the sequential occurrence of foci and their development. In some patients, there are dozens of foci disseminated throughout the skeleton. Foci may be located anywhere in the skeleton. The most frequent locations are cranial bones, ribs, pelvic bones and proximal segments of femoral bones. Painful palpation and local pain are the only clinical signs. Oedema of adjacent tissues may be present if a lesion is located superficially. Pain is always mild, never intensive and tolerable. The course of the disease is slow. Asymptomatic courses for many years may be encountered, and in these cases, a pathological fracture may be the first manifestation. Mild neutrophilic leukocytosis and mild anaemia are typical in routine blood cell count. In EG of
Supratentorial Tumours
477
Fig. 4.201a–e Ependymal cyst of the left
lateral ventricle. T2-weighted imaging (a–c), FLAIR (d) and T1-weighted imaging (e) reveal a small cystic formation in the projection of triangle of left lateral ventricle, which has characteristics identical to those CSF MR. Arrows idicate the wall of the cyst, which separates it from the cavity of lateral ventricle
Fig. 4.202a,b CT of porencephaly of the anterior and posterior horns of right lateral ventricle in an 11-month-old child
478
Chapter 4
Fig. 4.203a–c Porencephaly of right lateral ventricle (a 5-year-old child). T2-weighted imaging (a), T1-weighted imaging (b) and PSIF (c)
reveal a cystic lesion with clearly evident link to the cavity of the lateral ventricle
Fig. 4.204a–c Porencephaly of the right lateral ventricle. T2-weighted image (a) and T1-weighted images (b,c) demonstrate the porencephalic
cavity with a wide link to the body of the right lateral ventricle
Supratentorial Tumours
479
Fig. 4.205a–f Cyst of vascular plexus of the left lateral ventricle. CT without contrast enhancement (a–c) detects the round mass lesion with a hypodense centre and calcified capsule in the projection of triangle of left lateral ventricle. T2-weighted images (d,e) and T1-weighted image (f) clarify the location and structure of the cyst
480
Fig. 4.206a–f Lipoma of a vascular plexus. Case 1. CT before (a,b) and after (c) contrast enhancement. A hypodense (–63 H U) focus with microcalcifications is visualised in the projection of choroid plexus. The contrast accumulation in the lipoma is absent. Case 2. T2-
Chapter 4
weighted imaging (d) and T1-weighted imaging (e) detect microlipoma, with typical hyperintense MR signal, especially on T1-weighted imaging. The use of T1 sequence with the suppression of signal from fat confirms the diagnosis lipoma (f)
Supratentorial Tumours
bones, patients do not typically a have high eosinophilic count in blood; it is usually 4–10%. In most cases, manifestations are scanty, even if dissemination is multiple. EG have typical pathological features—it is a separated granulomatous and osteolytic process, evident by yellowishbrown discoloration of tissue masses within the bone cavity. Reticular matrix with many scattered eosinophils is found on histology. X-ray picture of EG is very peculiar. Destruction focus lies in the centre, several centimeters in diameter. It leaves bone marrow with penetration of every osteal layer. Bone defects are round, egg shaped or irregular (Fig. 4.207). Becoming confluent, they retain initial shape. Confluent defects may retain remnants of bone septi, which gives a markedly cellular appearance. Reactive sclerosis of bone margins is very important for diagnosis. Neither cortical layer thickening nor periosteal out-groupings are seen. CT and MRI may ascertain the character of bone destruction and dissemination of granulomatous process (Fig. 4.208). CT in bone regimen reveals a lesion(s) of isolated bone destruction with typical X-ray features. The thickened dura matter may be hyperdense and shows contrast enhancement. On T2-weighted imaging, EG are hyperintense, and the surrounding dura matter is dark. On Т1-weighted imaging, EG look isointense to cortical grey matter. In all sequences, granuloma has clear-cut contours with hypointense signal of cranial bones. The extent of contrast enhancement inside a granuloma, as well as the dura matter involvement, is better assessed on postcontrast MRI (Fig. 4.209).
4.10 Myeloma (Kahler’s Disease, Plasmacytoma) Myeloma (Kahler’s disease, plasmacytoma) is a systemic disorder caused by pathological proliferation of the bone marrow plasmatic cells. The aetiology is still unknown. In 80–90% of cases, some kind of cytogenetic pathology is revealed; often it is a chromosome 13 deletion. Myeloma accounts for 1% of all human cancer diseases, contributing to 2% of cancer mortality. It is second among haemoblastoses, after leukaemia. Incidence increases with age. Fifty new patients per 100,000 are diagnosed before the age of 80 years annually. In the United States, 14,600 new cases are diagnosed yearly. Multiple skeleton involvements prevail. Solitary lesion is considered plasmacytoma and is seen very rarely, especially in cranial bones (not more than 0.7% of all myeloma cases). The highest prevalence is among people 65–70 years of age. It is diagnosed a bit more frequently in
481
males. Higher incidence was reported in African Americans and Oceania inhabitants. Flat bones are affected more frequently than are tubular bones. Ribs, cranial bones, pelvic bones, vertebral column and diaphyses of tubular bones are affected. The disease starts with general fatigue, pain in bones (70% of cases) and weight loss. A pathological fracture is a frequent sign. Less often shortage of inspiration, chest pain, cryoglobulinaemia, amyloidosis and arterial hypertension are seen. Diagnosis is made by laboratory and instrumental examinations: normochromic normocytic anaemia (60%), renal failure (55%), hypercalcaemia with simultaneous hypercalciuria (30–50%), proteinuria (up to 90%) and Bens-Jones protein in urine (50%). Diagnosis is made by sternal puncture: if over 10% of plasmocytes are found, then myeloma diagnosis is considered probable. Initially, structural changes are represented by disseminated osteoporosis. Later, multiple foci of osteolysis occur by way of small bone tissue defects. Large cavities form regardless of periosteal or endosteal location, due to confluence of smaller cavities. The disease disseminates further, and pathological fractures, compression of vertebral bodies and cachexia occur. No metastasis in other organs is seen. Prognosis is poor. The diagnostic criteria of the disease are multiple osteolytic lesions of cranial vault bones (Angtuaco et al. 2004). Multiple lesions in vertebrae are typical for multiple myeloma (50%); solitary lesions (plasmacytoma) also affect the vertebral column more often than the cranial vault. Final diagnosis is made at the stage of dissemination when all skeleton is affected. Cerebral invasion is not typical for myeloma; however, infiltration of dura mater is seen occasionally. Diffuse osteoporosis with small foci of osteolysis is seen on X-ray (Fig. 4.210). Osteosclerosis may be seen only after treatment. CT reveals multiple lytic foci in cranial vault bones, having the appearance of a perforated lamina. Heterogeneous contrast enhancement of lytic foci and meninges is seen (if meningeal myelomatosis is present). It should be noted that the risk of renal failure increases ten times after injection of contrast medium in myeloma patients compared with other conditions. Risk may be decreased if contrast administration is combined with hyperhydration. 3D CТ reconstructs the picture of cranial bone involvement. On T1-weighted images, lytic bone lesions are iso- or hypointense compared with brain tissue. On T2weighted imaging, the signal is usually hyperintense. Contrast enhancement is prominent in homogeneous within lesions. Meningeal myelomatosis is better seen on MRI than on CT (Figs. 4.211, 4.212).
482
Chapter 4
Fig. 4.207a,b Eosinophilic granuloma (10-year-old child). X-ray craniograms in a left parietal bone detect an round area of bone destruction, with the lesion involving internal and external compact layers of bone (a lateral projection, b direct projection)
Fig. 4.208a–c Eosinophilic granuloma. CT before (a) and after (b) contrast enhancement. The soft tissue lesion with destruction of pari-
etal bone and intensive and homogeneous contrast accumulation is detected in the left parietal area. The destruction of all bone layers is revealed (c)
Supratentorial Tumours
Fig. 4.209a–f Eosinophilic granuloma. CT in bone window before
(a) and after (b) CE. The soft tissue mass lesion with destruction of parietal bone and peripheral contrast accumulation is detected in the left parietal area. T2-weighted image (c) and T1-weighted images in axial (d) and coronal (e) projections reveal a soft tissue lesion, which
483
is hyperintense on T2-weighted imaging and predominantly isointense on T1-weighted imaging, in the left parietal bone close to the coronary suture. Dura matter that separates granuloma from brain tissue is well visualised. The contrast accumulation is relatively intense predominantly in peripheral parts of granuloma (f)
484
Chapter 4
Fig. 4.210 Myeloma. The multiple small foci of destruction in the bones of cranial vault are visualised on the craniogram
Supratentorial Tumours
9 Fig. 4.211a–l Myeloma. CT in axial (a,b), sagittal (c), and coronal (d) projections with the use of standard and bone window detects the multiple foci of bone destruction, with a tendency of formation of wide lesions, especially of internal bone plate. 3D reconstruction of skull surface (view from behind) demonstrates the spreading of bone destruction with the lesion involving all bone layers (e). MRI:
485
T2-weighted imaging (f) and T1-weighted imaging before (g) and after (h–l) contrast enhancement demonstrate the bilateral pathological thickening of parietal bones, changes in their structure, hyperintense signal on T1-weighted image and pathological heterogeneous contrast accumulation in affected area. Convex brain veins and superior sagittal sinus are pushed inside the cranial cavity
486
Chapter 4
Fig. 4.212a–g Myeloma. CT series in bone window (a) detects multiple foci of destruction of right frontal and parietal bones with their pathological thickening. MRI: T2-weighted imaging with fat saturation (b), and T1-weighted imaging before (c, d) and after (e, f, g) contrast enhancement reveal multiple mass lesions of bones of calvaria and the base of brain. Soft tissue component intensively accumulates contrast medium
Supratentorial Tumours
487
Refere n c e s Angevine J (1988) The neuroglia. BNI Quart 4:21–23 Angtuaco E et al (2004) Multiple myeloma: clinical review and diagnostic imaging. Radiology 231:11–23 Arbaiza D, Pujol M, Conde C et al (1992) Primary cerebral lymphoma in 10 patients with AIDS. Comparative clinico-radiologic study with cerebral toxoplasmosis, cerebral tuberculoma and primary cerebral lymphoma in non-immunodepressed patients. Med Clin (Barc) 99:128–131 Armao D et al (2000) Colloid cyst of the third ventricle: imaging– pathologic correlation. AJNR Am J Neuroradiol 21:1470–1477 Arslanoglu A et al (2003) MR imaging characteristics of pilomyxoid astrocytomas. AJNR Am J Neuroradiol 24:1906–1908 Ashkan K, Casey A, D’Arrigo C et al (2000) Benign central neurocytoma. Cancer 89:1111–1120 Berens M, Rutka J et al (1990) Brain tumour epidemiology, growth and invasion. Neurosurg Clin North Am 1:1–18 Bergmann M, Edel G (1991) Primary intracerebral non-Hodgkin’s lymphoma. Pathology 12:246–253 Bigner D, McLendon R, Bruner J (eds) (1998) Russell and Rubinstein’s pathology of tumours of the nervous system, 6th ed. Arnold, London Burger P et al (2000) PA. In: Kleihues P, Cavenee WK (eds) Tumours of the CNS. IARC Press, Lyon, pp 45–51 Cha S (2006) Update on brain tumour imaging: from anatomy to physiology. AJNR Am J Neuroradiol 27:475–487 Cha S, Lupo JM, Chen M-H et al (2007) Differentiation of glioblastoma multiforme and single brain metastasis by peak height and percentage of signal intensity recovery derived from dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging. AJNR Am J Neuroradiol 28:1078–1084 Chiang F, Miller B, Chang L et al (1996) Fulminant cerebral lymphoma in AIDS. AJNR Am J Neuroradiol 17:157–160 Chiechi M et al (1995) Intracranial subependymomas: CT and MR imaging features in 24 cases. Am J Neuroradiol 165:1245–1250 Cuccia V et al (2003) Subependymal giant cell astrocytoma in children with tuberous sclerosis. Child Nerv Syst 19:232–243 Dolgushin M, Kornienko, Pronin I et al (2004) Complex diagnostics of metastatic diseases of the brain. Med Visualis 3:89–96 (in Russian) Dropcho E, Wisoff J, Walker R et al (1987) Supratentorial malignant gliomas in childhood: A review of fifty cases. Ann Neurol 22:355–364 Earle K (1955) Metastatic brain tumours. Dis Nerv Syst 16:86–92
Goebell E, Fiehler J, Ding XQ (2006) Disarrangement of fibre tracts and decline of neuronal density correlate in glioma patients—a combined diffusion tensor imaging and 1H-MR spectroscopy study. AJNR Am J Neuroradiol 27:1426–1431 Graff PA, Albright AL, Pang D (1992) Dissemination of supratentorial malignant gliomas via the cerebrospinal fluid in children. Neurosurg, Vol. 30, pp. 64-71 Grangier C, Coucke P, Croisille P et al (1994) Primary cerebral lymphoma: a retrospective study of 27 cases. Strahlenther Onkol 170:206–212 Greig NH et al. (1990) Increasing annual incidence of primary malignant brain tumors in the elderly. J Natl Cancer Inst Oct 17;82(20):1621-1624 Helton K, Phillips N, Khan R et al (2006) Diffusion tensor imaging of tract involvement in children with pontine tumours. AJNR Am J Neuroradiol 27:786–793 Hwang J et al (1999) Proton MR spectroscopic characteristics of pediatric PAs. AJNR Am J Neuroradiol 19:535–540 Jellison B et al (2004) Diffusion tensor imaging of cerebral matter: a pictorial review of physics. Fibre tract anatomy and tumour imaging patterns. AJNR Am J Neuroradiol 25:356–369 Jones B, Patterson R (1997) In: Ball WS Jr (ed) Pediatric neuroradiology. Lippincott-Raven, Philadelphia, pp 369–440 Ketonen L, Hiwatashi A, Sidhu R and Westesson P (2005) Pediatric brain and spin: an atlas of MRI and spectroscopy. Springer, Berlin Heidelberg New York Kleihues P, Cavenee W (2000) Tumours of the nervous system; pathology and genetics: world health organization international classification of tumours. IARC Press, Lyon Komotar R et al (2004) Pilocytic and pilomyxoid hypothalamic/chiasmatic astrocytomas. Neurosurgery 54:72–80 Konovalov A, Gorelyshev S, Ozerova V (1997) The colloid cysts of the third ventricle. J Vopr Neurosurg 3:3–8 (in Russian) Kornienko V, Pronin I, Serkov S et al (2003) Neuroradiologic diagnosis of the primary brain lymphomas. J Med Visualis 1:6–15 (in Russian) Korshunov A et al (2004) The histologic grade is a main prognostic factor for patients with intracranial ependimomas treated in the microneurosurgical era. Cancer 100:1230–1237 Kremer S, Grand S (2003) Dynamic contrast-enhanced MRI: differentiating melanoma and renal carcinoma metastases from high-grade astrocytomas and other metastases. Neuroradiology 45:44–49
Farwell J, Dohrmann G et al. (1977) Central nervous system tumors in children. Cancer 40:3123–3129
Lacroix M et al (2001) A multivariate analysis of 416 patients with GMB: prognosis, extent of resection, and survival. Neurosurgery 95:190–198
Fernandez C et al (2003) The usefulness of MRI in the diagnosis of dysembryoplastic neuroepithelial tumour in children: a study of 14 cases. AJNR Am J Neuroradiol 24:829–834
Matsko D, Korshunov G (1998) Atlas of tumours of the central nervous system (the histological structure). A. Polenov Neurosurgical Institute, St. Petersburg (in Russian)
Forbes G, Cohen A (1992) Primary cerebral lymphoma: an association with craniopharyngioma or cadaveric growth hormone therapy? MedJAust. 157:27–28
Matthay K et al (2003) Central nervous system metastases neuroblastoma: radiologic, clinical, and biologic features of 23 patients. Cancer 98:155–165
Gillard J, Waldman A, Barker P (eds) (2005) Clinical MR neuroimaging: diffusion, perfusion and spectroscopy. Cambridge University Press, Cambridge
Meltzer C et al (1995) The striated cerebellum: an MR imaging sign in Lhermitte-Duclos disease (dysplastic cerebellar gangliocytoma). Radiology 194:699–703
488
Chapter 4
Lantos P et al. (2000) Pathology and genetics of tumours of the CNS:Gliomatosis cerebri. Lyon, IARC Press, pp. 92–93
Salzman K, Osborn A, House P et al (2005) Giant tumefactive perivascular spaces. AJNR Am J Neuroradiol 26:298–305
Law M, Cha S (2002) High-grade gliomas and solitary metastases: differentiation by using perfusion and proton spectroscopic MR imaging. Radiology 222:715–721
Sarkar C et al (1999) Choroid plexus papilloma: a clinicopathological study of 23 cases. Surg Neurol 52:37–39
Lee M et al. (2002) Atypical teratoid/rhabdoid tumor of the CNS: clinico-pathological study. Neuropathology 22:252–260 Lev M et al. (2004) Glial tumor grading and outcome prediction using dynamic spin-echo MR susceptibility mapping compared with conventional contrast-enhanced MR: confounding effect of elevated rCBV of oligodendrogliomas. AJNR Am J Neuroradiol Feb;25(2):214-21 Louis D, Ohgaki H, Weistler O et al: WHO Classification of Tumours of the Central Nervous System. 4th ed. Lyon, France: IARC Press 2007:309 Lu S, Ahn D, Johnson G, Cha S (2003) Peritumoral diffusion tensor imaging of high-grade gliomas and metastatic brain tumors. AJNR Am J Neuroradiol May;24(5):937-41 Meters S, Khademian Z, Biegel J et al (2006) Primary intracranial atypical teratoid/rhabdoid tumours of infancy and childhood: MRI features and patient outcomes. AJNR Am J Neuroradiol 27:962–971 Nakajima M et al. (1998) Anaplastic ganglioglioma with dissemination to the spinal cord: a case report. SurgNeurolo 49:445–448 Nelson S et al (2002) Characterisation of untreated gliomas: magnetic resonance spectroscopic imaging. Neuroimag Clin N Am 12:599–613 Nemeth AJ, Henson JW, Mullins ME et al (2007) Improved detection of skull metastasis with diffusion-weighted MR imaging. AJNR Am J Neuroradiol 28:1088–1092 Nishio S et al (2002) Tumours around the foramen of Monro: clinical and neuroimaging features and their differential diagnosis. J Clin Neurosci 36:137–141 Nowak D et al (2002) Lhermitte-Duclos disease (dysplastic cerebellar gangliocytoma): a malformation, hamartoma or neoplasm? Acta Neurol Scand 105:137–145 Orrison W, Hart B (2000) Intraaxial brain tumours. In: Neuroimaging. Saunders, Philadelphia, pp 583–611 Osborn A (1994) Diagnostic neuroradiology. Mosby, St. Louis Osborn A (2004) Brain diagnostic imaging. Amirsys, Salt Lake City Percy A et al. (1972) Neoplasms of the central nervous system. Epidemiologic considerations.Neurology Jan;22(1):40-8 Podoprigora A, Pronin I, Fadeeva L (2000) Proton magnetic resonance spectroscopy in diagnostics of tumorous and nontumorous lesions in brain. Zh Vopr Neirokhir Im N N Burdenko. JulSep;(3):17-20; Pronin I, Konovalov A, Marjashev S (2002) Neuroradiologic features of the brain neurocytomas. J Med Visualis 1:6–15 (in Russian) Romodanov A (1965) Brain tumors in children. Kiev. Zdorovie, p. 340 Russell DS, Rubinstein LS (1989) Pathology of Tumors of the Nervous System. Baltimore: Williams and Wilkins, p. 470 Sadeghi N, Salmon I, Decaestecker C et al (2007) Stereotactic comparison among cerebral blood volume, methionine uptake, and histopathology in brain glioma. AJNR Am J Neuroradiol 28, 455–461
Selch M (1998) Gangliogliomas: experience with 3 patients and review of the literature. AmJClinOnc 21:557–564 Shin J et al (2001) Choroid plexus papilloma in the posterior cranial fossa: MR, CT, and angiographic findings. J Clin Imaging 25:154–162 Shin J et al (2002) Neuronal tumours of the central nervous system: radiology findings and pathological correlation. Radiographics 22:1177–1189 Stadlbauer A, Nimsky C, Gruber S et al (2007) Changes in fibre integrity, diffusivity, and metabolism of the pyramidal tract adjacent to gliomas: a quantitative diffusion tensor fibre tracking and MR spectroscopic imaging study. AJNR Am J Neuroradiol 28:462–469 Stanescu Cosson R et al (2001) Dysembryoplastic neuroepithelial tumours: CT, MR findings and imaging follow-up: a study of 53 cases. J Neuroradiol 28:230–240 Stark A, Nabavi A, Mehdorn H et al (2005) Glioblastoma multiforme—report of 267 cases treated at a single institution. Surg Neurol 63:162–169 Takahara T, et al. (2004) Diffusion weighted whole body imaging with background body signal suppression (DWIBS): technical improvement using free breathing, STIR and high resolution 3D display. Radiat Med Jul-Aug;22(4):275 Takahara T, Imai Y, Yamashita T (2004) Diffusion weighted whole body imaging with background body signal suppression (DWIBS): technical improvement using free breathing, STIR and high resolution 3D display. Radiat Med 22, 4, 275–282 Tamburrini G et al (2003) Desmoplastic infantile ganglioglioma. Child Nerv Syst 19:292–297 Tharin S, Golby A (2007) Functional brain mapping and its applications to neurosurgery. Neurosurgery 60:185–202 Ulitin AY, Oliushin VE, Poliakov IV (2005) Epidemiology of primary brain tumors in Saint Petersburg. Zh Vopr Neirokhir Im N N Burdenko Jan-Mar;(1):6-11; discussion 11-12 (in russian) Vates G et al (2003) Gliomatosis cerebri: a review of 22 cases. Neurosurgery 53:261–271 Yakovlev P, Wadsworth R (1946) Schizencephalies: a study of the congenital clefts in the cerebral mantle. JNeuropathol Exp Neurol 5:116-130 Yartsev VV, Korshunov AG, Nepomniashiy V (1997) Some aspects of epidemiology and classification of CNS tumors. J Vopr Neurosurg by N.Burdenko 3:9-13 (in russian) Zemskaya A (1985) Brain tumours of astrocytic line. Medicine, Leningrad (in Russian) Zulch KJ (1965) Brain Tumors : their biology and their pathology. 2. ed., Springer Verlag ; New York, p. 326 Zulch K (1986) Brain tumors. Their biology and pathology. 3rd ed., Berlin, Springer Verlag, Berlin, Heidelberg, New York
Chapter 5
5
Pineal Region Tumours
5.1 5.2 5.3 5.4 5.5
Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Germ Cell Tumours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pineal Parenchymal Tumours . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Glial Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Other Histological Types of Tumours .. . . . . . . . . . . . . . . . . . . . . . .
5.1
Introduction
489 490 503 510 510
Pineal region tumours are relatively rare, accounting for 0.5– 1% among all intracranial masses, but in children, they are encountered in a higher percent of cases, roughly 3–8% (Burlutsky 1962; Ganti et al. 1986; Hoffman et al. 1991; Kornienko et al. 1993; Chiechi et al. 1995; Konovalov and Pitskhelauri 2004). It is thought that the pineal region is the second most frequent site where supratentorial tumours occur in children (Ganti et al. 1986; Edwards et al. 1988; Hoffman et al. 1991). Although this region is small (as are the brain structures that constitute it), the tumour histology in this region significantly varies—up to 17 forms of tumour have been described. According to modern histological classification, tumours and other masses of the pineal region can be subdivided into four groups: 1. Germ cell tumours a. Germinoma b. Teratoma i. Mature ii. Immature c. Malignant d. Choriocarcinoma e. Embryonal carcinoma
f. Yolk-sack tumour (endodermal sinus tumour) g. Mixed germ cell tumours 2. Pineal parenchymal tumours a. Pineocytoma i. Pineocytoma with intermediate differentiation b. Pineoblastoma c. Mixed tumours of the pineal gland (pineocytoma–pineoblastoma) d. Papillary tumour of the pineal region 3. Glial tumours a. Astrocytoma b. Anaplastic astrocytoma c. Glioblastoma d. Ependymoma e. Anaplastic ependymoma f. Oligodendroglioma g. Choroid papilloma 4. Mixed tumours and nontumoural masses a. Metastasis b. Dermoid, epidermoid c. Meningioma d. Lipoma e. Cysts of the pineal region f. Vascular malformations (cavernoma) Four main syndromes prevail among clinical features of tumours of the pineal region: intracranial hypertension due to compression of the Sylvian aqueduct, Parinaud’s syndrome (midbrain disorders), cerebellar signs, and endocrine pathology (premature sexual development, diabetes insipidus)(Winfield 1985; Sawaya et al. 1900; Bruce et al. 1993). Tumours of the pineal region account for less than 1%— (170 of 16,900 cases) of primary brain tumours reported annually in the United States (Boring 1992). The supposed number of new cases of tumours of the pineal region in Russia is about 100 cases per year (Konovalov and Pitskhelauri 2004). At present CT and MRI are the main diagnostic tools that may give a complete description of the pathological lesion located in the pineal region. MRI capabilities are much wider than those of CT: MRI is a study in multiprojections—;sagittal
490
and coronal images—may be acquired (however, multispiral CT devices are archieving results similar to MRI). In addition, MRI performs 3D imaging, which helps to determine location of the tumour relative to the third ventricle and adjacent tissues, predominant growth direction (supra- or subtentorial), relationship with venous and other structures of the pineal region, and the extent of invasion into the adjacent brain tissue. However, CT is the best tool to describe a petrified part of the pineal gland. It is noteworthy that in children younger than 6 years, calcification of the pineal gland is atypical, and at the age of 11–14 years, it may be revealed in approximately 11% of cases. Thus, calcification of the pineal gland in children is suggestive of tumour or other mass of the pineal region (Zimmermann et al. 1982). In addition, if there is displacement of calcification from the median axis and/or its location is a part of several tumours, is helpful in making precise preoperative differential diagnosis. According to classification adopted by the Burdenko Neurosurgical Institute (based on comparisons of clinical, CT, MRI, intraoperative, and autopsy data), tumours of the pineal region may be subdivided into five categories in relation to their size, location, and predominant expansion (Kоnovalov and Pitskhelauri 2004):
Chapter 5
1. Tumours predominantly located in the quadrigeminal cistern, with a diameter up to 2.5 cm (Fig. 5.1а) 2. Tumours predominantly located in the posterior portion of the third ventricle, with a diameter up to 2.5 cm (Fig. 5.1b) 3. Intermediate-size tumours (a combination of the first and the second variants), with a diameter up to 4 cm (Fig. 5.1c) 4. Large tumours completely occupying the quadrigeminal cistern and the posterior portion of the third ventricle, infrequently invading one of the lateral ventricles, with maximal size 6–7 cm (Fig. 5.1d) 5. Giant tumours totally or subtotally occupying the third and the fourth ventricles, and invading the lateral ventricles, >7 cm in diameter (Fig. 5.1e) Such a subdivision allows planning treatment approaches in patients with tumours of the pineal region—conservative, surgical (including the approach and plan of operation), radiation, or combination of the former.
5.2
Germ Cell Tumours
Germ cell tumours are dysembryonic tumours, most frequently affecting the reproductive organs, but may be revealed within the CNS, being usually seated midline. They are most
Fig. 5.1а–e Classification of tumours of the pineal region according to their size, location, and expansion
Pineal Region Tumours
491
Fig. 5.2a–c Germinoma of the pineal region. Axial CT scan with contrast enhancement within the pineal gland reveals a hyperdensive tu-
mour with small calcification in the depth of tumour. There is obstructive hydrocephalus
frequently encountered within the CNS in the pineal region (Jennings et al. 1985; Russell et al. 1989), less frequently in the suprasellar region, and least frequently in thalami and basal ganglia, the ventricular system, cerebellum, the frontal lobe, the septum pellucidum, optic chiasm, and exceptionally rarely, in the spinal cord (Tanaka et al. 1979; Stefanko et al. 1979; Jennings et al. 1985; Bjornsson et al. 1985; Masuzawa et al. 1986; Manor et al. 1990). Histologically, germ cell tumours are subdivided into several subtypes: germinoma, embryonal carcinoma, endodermal sinus tumour, choriocarcinoma, teratoma, and mixed tumours. It is noteworthy that embryonal carcinoma, endodermal sinus tumour, choriocarcinoma, and teratomas are considered nongerminomatous germ cell tumours. These tumours make up to a third of all tumours of the pineal region. They are thought more frequently encountered in males than in females, predominantly within the first three decades of the life, with the prevalence in the second decade. Usually their clinical manifestations are premature sexual development and hydrocephalus. The germ cell tumours usually grow expansively, but may have infiltrative growth also.
5.2.1 Germinoma Germinomas are observed in up to 67% of cases among germ cell tumours, and typically, they are in the pineal region; they make up 40% of all tumours of this region, but may be revealed in other parts of the brain (Sojima et al. 1987; Edwards et al. 1988; Russell et al. 1989; Chang et al. 1989; Huk et al. 1990; Smirniotopoulos et al. 1992; Matsutati et al. 1997). They are suprasellar in 25–35% of cases, and in projection to basal ganglia in 10% of cases. It isbelieved these tumours are more frequently encountered in boys than in girls, and their clinical manifestations are hydrocephalus, midbrain signs, and premature sexual development. The peak of incidence in children is in the second decade of life (Fetell et al. 1986; Smirniotopoulos et al. 1992). These tumours are sensitive to radiation
and chemotherapy, and 10-year-survival may reach 95% after irradiation with doses of 50–55 Gy (Borden et al. 1973). Germinomas are non-encapsulated tumours that usually have expansive growth pattern, but can also grow infiltratively; infrequently they become calcified or contain haemorrhages. Germinomas are identical to seminoma histologically and consist of strands or fenestrae, with large glycogen-containing tumour cells and large vesicular nuclei, encircled by fibrous connective tissue with accumulations of lymphocytes between fenestrae (Matsko 1998). On CT germinomas are typically located within the posterior portions of the third ventricles, sometimes with tamponade of the quadrigeminal cistern, and usually they have occluded CSF pathways at this level. Large tumours expand in the anterior direction into the third ventricle cavity, with infiltration of thalami, and subtentorial growth is also noted. Pineal gland calcification is usually located within the tumour along the midline, but may be also located eccentrically. However, it is always encircled by the tumour tissue (Chang et al. 1981; Ganti et al. 1986; Kornienko et al. 1993). Typically, a germinoma looks like a homogenous (except calcification) mass isodensive to brain tissue; its density increases after contrast enhancement up to 50–65 НU (Fig. 5.2). MRI reveals a relatively homogenous mass iso- or hypointensive to brain tissue on Т1-weighted images (Kilgore et al. 1986; Karnaze et al. 1986), and iso- or hyperintensive on T2weighted images (Figs. 5.3, 5.4). Pineal gland petrificates are better detected on Т2- and Т2*-weighted images than on Т1weighted images, but only if they are large in size (Fig. 5.5). If a tumour is large, then small or large cysts may be present in its stroma (Figs. 5.6, 5.7). Around the tumour on T2-weighted images an area of increased signal is frequently seen, which reflects perifocal oedema of brain tissue caused by tumour invasion. Rarely, germinomas may have atypical structure with multiple cysts and haemorrhages (Fig. 5.8). Contrast enhancement is usually prominent and allows ascertaining location and expansion of the tumour (Tien et al. 1990; Zee 1991; Liang et al. 1992) (Figs. 5.9, 5.10). MRI visualises the quadri-
492
Fig. 5.3a–c Germinoma of the pineal region. T2-weighted image in the axial projection (а) shows the tumour is weakly hyperintensive to brain tissue, whereas on axial (b) and sagittal (c) projections T1-
Chapter 5
weighted MR images the tumour is hypointensive to brain tissue. The ventricular system is dilated, and the third ventricle is deformed. The lamina tecti is pushed backwards Fig. 5.4a,b Germinoma of the pineal
region. T2-weighted image (а) in the axial projection the tumour is hyperintensive to brain tissue and hypointensive on the T1-weighted image (b). Perifocal oedema is better demonstrated on the image with prolonged TR/TE (а), appearing as a hyperintensive area. Small cysts hyperintensive on the T2-weighted image (а) and hypointensive on the Т1-weighted image (b) are seen in the depth of the tumour. Calcification of the pineal gland is located in the anterior inferior portions of the tumour (arrow)
Pineal Region Tumours
Fig. 5.5a–c Germinoma of the pineal region. On Т2-weighted (а) and T1-weighted images in axial (b) and sagittal (c) projections, there is a small tumour in the posterior portions of the third ventricle. Cal-
493
cification of the pineal gland is visualised in the depth of the tumour (hypointensive area). Metastasis is seen on the bottom of the third ventricle near tuber cinereum
Fig. 5.6a–c Germinoma of the pineal region. а,b Axial Т2-weighted image and T1-weighted image. The tumour has a heterogeneous structure, with many small cysts. Perifocal oedema is seen around the tumour. Sagittal T1-weighted image (c) gives additional information about expansion of the tumour
494
Chapter 5
Fig. 5.7a–e Germinoma of the pineal region. а,b Axial Т2-weighted images. The tumour has a heterogeneous structure, with a large cyst leftwards. The area of tumour invasion into basal ganglion rightwards is clearly seen. The tumour intensively but heterogeneously accumulates contrast medium (c–e)
Fig. 5.8a,b Germinoma of the pineal
region. T1-weighted image (а) and Т2weighted images (b). The tumour is hyperintensive on the T1-weighted image. Hyperintensive areas on T1-weighted images are intratumoural haemorrhages. On Т2-weighted images, the tumour has multicystic structures resembling honeycombs
Pineal Region Tumours
Fig. 5.9a–f Germinoma of the pineal region. Т2-weighted images
(а,b) and T1-weighted image (c) demonstrate a small tumour in the posterior portions of the third ventricle. The area of oedema/invasion is hyperintensive on T2-weighted images and hypointensive on
495
Т1-weighted images. Prominent and homogenous contrast enhancement of the tumour is seen. Initial signs of obstructive hydrocephalus are revealed (d–f)
496
Chapter 5 Fig. 5.10a,b Germinoma of the pineal
region. T1-weighted image before (а) and after (b) enhancement. The solid part of the tumour intensively accumulates contrast medium, improving visualisation of expansion of the tumour and its internal structure. The area of tumour-related oedema/invasion is hypointensive and does not enhance
Pineal Region Tumours
497
geminal plate and the internal cerebral veins better than CT does. MRI signal is characteristically changed if there is a haemorrhage into the tumour. Germinomas frequently present as metastases along the subarachnoid spaces, and subependymally along the ventricular system and the spinal cord. An atypical picture, metastasis of germinoma along the anterior portions of the lateral ventricles is characterised by a feature called “the ear sign” (Kornienko et al. 1993) (Fig. 5.11). Metastasis into the chiasmal–sellar region may resemble a primary tumour of this region (Figs. 5.12, 5.13). When a tumour disseminates along the subarachnoid space, nodes of atypical shape and structure may form, which have no certain differences, for example from metastasis other origin (Figs. 5.14, 5.15). Germinomas are very sensitive to radiation. After 20 Gy, marked decrease in the tumour size may already be seen. It is a feature of germinomas that allows presuming tumour histology merely by its reaction to irradiation (handa et al. 1981). Such a technique is called the biological biopsy of the
pineal region tumours. At present, not only CT, but also MRI allows assessment of efficiency of irradiation of germinomas (Fig. 5.11, 5.16).
5.2.2 Teratoma Teratomas are the second frequently encountered tumour (Huk et al. 1990; Atlas 1991) (up to 22% of cases) among germ cell tumours. Mainly they develop within the first decade of life—earlier than germinomas develop. As this type of tumours originates from three embryonic layers, they may contain hair, fat, bones, and teeth in different proportions. Teratomas may be mature, consisting of completely differentiated tissues, or immature (malignant), which are represented by immature tissues or with malignant transformations. Clinical manifestations vary and depend on the size and the histological maturity of tumours. Variability of tumour composition predetermines variabil-
9 Fig. 5.11a–j Germinoma of the pineal region in a 6-year-old child. CT (a) with enhancement: hyperdensive tumour of the pineal region and calcification of the pineal gland are located within the tumour stroma. Т2-weighted MR image (b) reveals the tumour with compact structure isointensive to cerebral gray matter. c–e Prominent enhancement with signs of metastases along ependyma of the ventricular system. MRA in axial (f) and oblique sagittal (g) projections determines the interrelation of the tumour with vessels of the pineal region. On CT (h) after radiation (30 Gy) the size of tumour looks markedly reduced. MRI enhancement (i,j) done at the same time: the remnants of tumour intensively accumulate contrast medium, and ependyma of the lateral ventricles is also slightly enhanced
498
Chapter 5 Fig. 5.12a,b Germinoma of the pineal
region in a 9-year-old boy with metastasis into the chiasmal–sellar region. T1-weighted image (а) and Т2-weighted image (b). The tumours have similar MR features
Fig. 5.13 Germinoma of the pineal region
with metastasis into the chiasmal–sellar region. Postcontrast Т1-weighted image
Fig. 5.14a,b Metastasis of germinoma in
the right frontal lobe. T1-weighted image (а) reveals a large, mildly hypointensive area in the right frontal lobe. Oedemarelated signal intermingles with a signal from the affected tissue. Postcontrast, the T1-weighted image (b) shows tumour tissue enhancement, and becomes vivid, emphasising the expansion of the tumour in the frontal lobe
Pineal Region Tumours
499
Fig. 5.15a–c Germinoma of the left basal ganglions. Т2-weighted imagees (а–c) demonstrates a tumour with multicystic structure with par-
tial occlusion of the left foramen of Monro
Fig. 5.16a,b Germinoma of the pineal
region. There is seen a marked reduction of tumour size on a series T1-weighted image before (а) and after (b) irradiation. MR signal of the solid part of the tumour became more hyperintensive to brain tissue after irradiation
500
Fig. 5.17a–f Teratoma of the pineal region. X-ray craniogram in the lateral projection (а) re-
veals calcifications and tooth germ at the site of tumour location. Axial CT (b) shows a tumour in the pineal region and the third ventricle, with fatty and calcified inclusions and obstructive hydrocephalus. Т2-weighted image (c) and T1-weighted image (d,e) demonstrate a giant tumour of the posterior portions of the third ventricle with dissemination of fatty inclusions (hyperintensive on T1-weighted image) along the ventricular system and subarachnoid spaces of brain and spinal cord. f Photo of the part of the tumour after excision: developed tooth with fragment of jaw bone is seen
Chapter 5
Pineal Region Tumours
501
Fig. 5.18a–c Teratoma of the pineal region in a 4.5-year-old child. а,b Axial T1-weighted image and Т2-weighted image reveals a tumour with heterogeneous structure in the posterior portions of the third ventricle. On the sagittal image (c) it is seen that the tumour partially
penetrates with its cystic parts into the fourth ventricle. High MRI signal on T1-weighted image is represented by fatty inclusions within the tumour
ity of CT and MRI picture of teratomas. CТ frequently reveals fat (low density) and structures more dense (petrificates or structures resembling teeth). On CT, teratomas are usually clearly demarcated from the brain tissues, without contrast enhancement. On MRI, high signal on T1-weighted images is typical for the accumulation of fat; calcifications look dark in all sequences (Fig. 5.17). Cysts are typical for teratomas (Fig. 5.18). There are cases of spontaneous rupture of the capsule of the teratoma with dissemination of its various fragments (fats) along the ventricular system (Fig. 5.19). There are several reports of a ring-like appearance of contrast enhancement in teratomas. Malignant teratomas have a propensity to invasion,
and metastases along subarachnoid spaces of brain and spinal cord may be found (Fig. 5.20). Intracranial nongerminomatous germ cell tumours are rare malignancies of the brain. Their characteristic feature is a production of specific tumour markers: alpha-fetoprotein and beta-human chorionic gonadotropin.
5.2.3 Choriocarcinoma Choriocarcinoma is the rarest tumour among germ cell tumours of the pineal region. It is highly malignant and has invasive growth, which is why it has a very poor prognosis. CT
Fig. 5.19a–c Teratoma of the pineal region. Т2-weighted image (а) and T1-weighted images (b,c) reveal a tumour with heterogeneous structure in the posterior portions of the third ventricle, with dissemination of fatty inclusions (hyperintensive on T1-weighted image) along the ventricular system
502
Fig. 5.20a–f Malignant teratoma of the pineal region. Axial CT scan
with contrast enhancement (а) shows a tumour of the pineal gland with cystic and solid components. The follow-up MR study in Т2 sequence (b) and CT (c) after radiation demonstrates that the tumour
Chapter 5
size was reduced. The follow-up MR study a year later reveals the continued growth of the tumour with many newly formed calcifications on CT (d) and large invasion of the brain tissue on MRI (е,f)
Pineal Region Tumours
503
Fig. 5.21a–c Choriocarcinoma of the pineal region with the intratumoural and the intraventricular haemorrhage. Axial CT scan (а) reveals a hyperdensive tumour in the posterior portions of the third ventricle. The lateral ventricles are enlarged, and accumulation of
fresh blood is seen along the falx cerebri and in the posterior horn of the lateral ventricle. T1-weighted image (b) and Т2-weighted image (c) demonstrate a tumour with signs of acute and subacute haemorrhage
and MRI signs of the tumour are nonspecific. However, these tumours are highly vascularised and have typical MR features of subacute haemorrhages (Fig. 5.21). Elevation of chorionic gonadotropin level in serum and CSF is an important differential diagnostic marker of the tumour.
heterogeneous signal intensity (Osborn et al. 1994). Invasion of adjacent structures is sometimes observed. In our series of observations, this type of tumour had homogenous, predominantly solid structure, with prominent contrast enhancement (Fig. 5.22).
5.2.4 Embryonal Carcinoma
5.2.6 Mixed Germ Cell Tumours
Pure embryonal carcinoma is rarely seen; it is usually a component of mixed germ cell tumours. The maximum incidence occurse at 15 years of age, and it is prevalent in the male population. In typical cases, it is represented by strands of epithelial cells, glandular structures with signs of anaplasia, and multiple necrotic foci. It is observed in less than 5% of all germ cell tumours. On CT, the tumour has high density, with calcified inclusions and prominent contrast enhancement.
Mixed germ cell tumours are more frequently encountered than are the above-mentioned subgroup, and they contain elements of these tumours. CT and MRI pictures are nonspecific and have no differential signs within this histological group of tumours. Cysts, petrificates, and haemorrhages are frequently seen. Contrast enhancement is prominent and heterogeneous. Typical features are rapid growth, extensive invasion of adjacent brain structures, and metastases (up to 30%) along ependyma of the lateral ventricles as well as subarachnoid spaces (Figs. 5.23, 5.24). However, in the initial stages of the disease, small tumours may be also seen (Fig. 5.25).
5.2.5 Yolk-Sack Tumour Yolk-sack tumour (or endodermal sinus tumour) is a highly malignant germ cell tumour with histology close to that of embryonic cancer. That is why they it is also known as infantile-type embryonic cancer. The distinguishing features of these tumours are Schiller-Duvall bodies and intracytoplasmic eosinophilic inclusions, containing alpha-fetoprotein. That is why elevation of alpha-fetoprotein is highly specific for this type of tumour. On CT according to reports in literature, these tumours are usually heterogeneous in density, with foci of calcification and cysts, and on MRI they also have
5.3
Pineal Parenchymal Tumours
Tumours of the pineal gland parenchyma are not so frequent, and compose 13–32% of cases among patients with tumours of the pineal region (Smirniotopoulos et al. 1992). In contrast to germ cell tumours, they are located predominantly in the pineal region. The maximum incidence is within the fourth decade of life, and they are seldom found in children (less than 11%).
504
Chapter 5
Fig. 5.22a–f Non–germ cell tumour with high alpha-fetoprotein content in blood serum in a 3-month-old child. CT scans before (а) and
after (b) contrast enhancement demonstrate a large solid tumour causing obstructive hydrocephalus. On MRI the tumour is characterised by a homogenous structure (c,d) and contrast enhancement (e,f)
Pineal Region Tumours
505
Fig. 5.23a–c Mixed germ cell tumours of the pineal region with metastases. Case 1. Axial Т1-weighted MR image (а) reveals a tumour within the site of the pineal gland with infiltration of the adjacent parts of thalami. There are suspicious areas of MR signal changes in the periventricular areas of the anterior horns of the lateral ventricles. Postcontrast T1-weighted image (b) shows extensive dissemi-
nation of metastases along ependyma of the ventricular system and subarachnoid spaces of brain. Case 2. Postcontrast T1-weighted image (c) demonstrates a tumour of the pineal region with prominent enhancement and dissemination of metastases along ependyma of the anterior horns of the lateral ventricles
Fig. 5.24a–e Malignant mixed germ cell tumour. T1-weighted image (a), DWI with b = 500 (b), and b = 1000 (c), and T2-weighted image (d) reveals multiple tumour nodes (in the lateral ventricles and
the pineal region), with prominent peritumoural oedema. There is a prominent contrast enhancement of tumour nodes (a). d,e see next page
506
Chapter 5
Fig. 5.24a–e (continued) Malignant mixed germ cell tumour. T1-weighted image (a), DWI with b = 500 (b), and b = 1,000 (c), and T2-weighted image (d) reveals multiple tumour nodes (in the lateral ventricles and the pineal region), with prominent peritumoural oedema. There is a prominent contrast enhancement of tumour nodes (a). MRS shows a marked elevation of the Lac peak (e)
Fig. 5.25a–c Malignant mixed germ cell tumour. T1-weighted image (а) after enhancement, Т2-weighted image (b), and PSIF (c) shows
a small tumour in the posterior portions of the third ventricle with signs of partial compression of the anterior part of the aqueduct of Sylvius
There are four main subtypes of these tumours histology: pineocytoma, mixed pineocytoma/pineoblastoma, pineocytoma with intermediate differentiation, and pineoblastoma.
5.3.1 Pineocytoma Pineocytoma is a benign tumour. This tumour consists of differentiated pineocytes of the pineal gland. The tumour contains monomorphic cells with round nuclei and light nucleoplasm. These cells have processes that form so-called pseudorosettes. A large number of vessels and petrificates are seen. Pineocytoma is characterised by slow growth and rarely gives rise to metastases along the subarachnoid spaces. It is seldom encountered in children; these tumours up to account for only 11% of all tumours of the pineal region in children.
On CT the tumour is usually well delineated from the adjacent brain, is iso- or hypodensive, and sometimes it possesses calcifications located on periphery. The contrast enhancement in most cases is heterogeneous. MR features are nonspecific—pineocytoma appears as a well-delineated structure that does not infiltrate adjacent brain structures (Nakagawa et al. 1990). If small, such a tumour may have a cystic structure. If large, a pineocytoma may not differ by its features from other, more aggressive tumours of the pineal region (Figs. 5.26–5.29). When anaplastic changes develop within a pineocytoma, then dense cellular areas with mitoses and proliferation of vascular endothelium appear. Foci of intratumoural haemorrhages and areas of adjacent tissue infiltration appear (Figs. 5.30, 5.31).
Pineal Region Tumours
507
Fig. 5.26a–d Pineocytoma. Axial CT (а) reveals a hypodensive tumour in the posterior
portions of the third ventricle with additional hyperdensity in its dorsal parts. Т2-weighted image (b) in the same plane demonstrates that the tumour consists of two parts with different MR signal—high in the anterior and low in the posterior part. This transition is clear-cut and linear, which speaks for the cystic nature of the tumour structure. Axial (c) and sagittal (d) T1-weighted images confirm that. The differences in MR signal intensity in the anterior and the posterior portions of the tumour are caused by the sedimentation phenomenon of protein components (probably those of blood), settling when the patient’s head lies supine
Fig. 5.27a–c Pineocytoma. Т2-weighted image (а), T1-weighted image (b), and FLAIR (c) reveals a tumour with cystic structure in the posterior portions of the third ventricle. MR signal of the cyst contents is high in all sequences
508
Chapter 5
Fig. 5.28a–f Pineocytoma. Т2-weighted image (а), T1-weighted image (b), and MR myelography (c) reveals a tumour of solid structure in the
posterior portions of the third ventricle. The tumour accumulated contrast medium homogenously after intravenous injection (d–f)
Fig. 5.29a–c Pineocytoma. Postcontrast CТ (а) reveals a large tu-
mour in the posterior portions of the third ventricle. The tumour has a solid structure. T1-weighted image (b) and Т2-weighted image (c)
additionally reveals a hypointensive signal on the tumour periphery and along the subarachnoid spaces—a sign of old haemorrhage (hemosiderosis)
Pineal Region Tumours
509
Fig. 5.30a–c Anaplastic pineocytoma. T1-weighted image (а,c) and Т2-weighted image (b) reveals a large tumour with heterogeneous MR signal characteristics Fig. 5.31 Anaplastic pineocytoma. Sagittal
T1-weighted image reveals a large tumour with the intratumoural haemorrhage (the area of hyperintensive MR signal)
Fig. 5.32a,b Pineoblastoma in a 4-year-
old child. CT before (а) and postcontrast (b) shows a large tumour in the posterior portions of the third ventricle with massive calcification. The soft tissue component of the tumour intensively enhanced after intravenous contrast medium injection
510
Chapter 5
5.3.2 Pineoblastoma Pineoblastoma is a primary malignant tumour consisting of undifferentiated cells. Histological features of the tumour completely correspond to those of embryonic-type tumours. Pineoblastoma has a structure resembling retino-, medullo-, and ependymoblastomas. On light microscopy, the tumour resembles neuroblastoma and consists of small monomorphic cells with hyperchromatic nuclei, among them Homer-Right rosettes and accumulations of true rosettes of Flexner-Wintersteiner are seen. Many vessels are seen in pineoblastomas, and endothelial proliferation is found sometimes. Foci of necrosis are typical for this type of tumour. In contrast to pineocytomas, pineoblastomas are mostly seen in younger patients or children. In almost all cases, metastases along the subarachnoid spaces of brain and spinal cord are observed. When CT or MRI primarily diagnose a tumour, it is usually large with occlusion of CSF cerebral pathways on the level of aqueduct. On conventional CT, a tumour is usually slightly hyperdensive. Calcifications are rarely seen. Contrast enhancement may be heterogeneous or homogenous. However, atypical tumours with multiple calcifications may be found (Fig. 5.32). On MRI, tumour masses are iso- or hypointensive on T1-weighted images, and relatively have iso- or slightly hyperintensive signal on T2-weighted images. Foci of necrosis and cystic degeneration may be found within pineoblastomas that have hyperintensive signal on T2-weighted images. Contrast enhancement is heterogeneous on MRI as well as on CT (Figs. 3.33–3.35).
5.4
Glial Tumours
Glial tumours expand into the pineal region from adjacent brain structures—such as the thalamus, midbrain, quadrigeminal plate, splenium of corpus callosum—and are mainly represented by astrocytomas and ependymomas. Among astrocytic gliomas, benign gliomas of the thalamus and quadrigeminal plate with diffuse growth are most frequently seen; malignant gliomas are rarely diagnosed. In cases of astrocytomas with unascertained maturity, there are areas of infiltration of the midbrain, and the tumour tissue grows out of the lateral part of the midbrain, causing compression of the Sylvian aqueduct. There is no contrast enhancement of the pathological lesion (Fig. 5.36). Pilocytic astrocytomas, conversely, are characterised by prominent and relatively homogenous contrast enhancement (Fig. 5.37). Typical deformity and enlargement of quadrigeminal plate, as a whole or separate colliculi, with compression of the aqueduct of Sylvius and absence of contrast enhancement on postcontrast series of MRI, are particular to benign glioma (Fig. 5.38). Malignant astrocytomas (including, glioblastoma) are characterised by heterogeneity of structure and type of contrast enhancement (Fig. 5.39). Ependymomas of the posterior portion of the third ventricle are relatively slow-growing tumours, with moderate inva-
sion of the surrounding brain tissues. Benign and malignant tumours are observed in this region (Figs. 5.40, 5.41).
5.5
Other Histological Types of Tumours
5.5.1 Dermoid Tumours Dermoid tumours are midline tumours, which contain fat structures, flat epithelium (as well as epidermoid tumours), hair follicles, and sebaceous and sweat glands. They usually have a thick capsule with areas of calcification. They are rarely seen in children. At present, we have had only a few observations of dermoid tumours located within the pineal region. On CT and MRI, this tumour has heterogeneous structure with multiple petrificates (hyperdensive on CT and hypointensive on MRI), and a focus of cystic degeneration of fat accumulation (hypodensive on CT and hyperintensive on MR T1-weighted images) (Fig. 5.42).
5.5.2 Epidermoid Tumours Epidermoids are usually located more eccentrically. They are frequently seen in the cerebellopontine angle, less frequently in the sellar region. Pineal location of an epidermoid tumour is rare. On MRI, an epidermoid tumour has a slightly hyperintensive signal in comparison with CSF and, often, a festoon, irregular border, in contrast to other glial tumours. DWI allows making a preoperative diagnosis with nearly 100% precision (Figs. 5.43, 5.44).
5.5.3 Lipoma Lipomas of the pineal region are rare. We often observed lipomas of the ambient cistern or the posterior portion of corpus callosum, which may locate below as well as above the splenium of corpus callosum and extend into the pineal gland region. CT and MRI of the pineal region lipomas reveal a picture typical for lipomas of any location (Fig. 5.45). On CT it appears as a mass with decreased density (up to –50 to –70 HU). On MRI it appears markedly hyperintensive on T1weighted images. MR signal change on T2-weighted images is more heterogeneous. As usual, on the periphery of a lipoma, there is a thin area of hypointensive signal—a chemical-shift artefact phenomenon.
5.3.4 Cavernoma Cavernoma (cavernous angioma) is a type of vascular malformation, frequently seen in the cerebral hemispheres and the brainstem. It is extremely rare in the pineal region (Dempsey et al. 1992; Konovalov et al. 2004). Its MR features are identical to those of elsewhere-located cavernomas (Fig. 5.46).
Pineal Region Tumours
511
Fig. 5.33a–e Pineoblastoma. Т2-weighted image (a) and T1-weighted image (b,c) reveals a tumour in the posterior portions of the third ventricle, with obstructive hydrocephalus. There is a small area of subacute haemorrhage within a tumour’s stroma. After intravenous gadolinium, enhancement the tumour intensifies, and it homogenously accumulates the contrast medium (d,e)
512
Fig. 5.34a–f Pineoblastoma. Т2-weighted image (а), T1-weighted image (b,c), and MR myelography (f) reveals a tumour with heterogeneous structure in the posterior portions of the third ventricle and obstructive hydrocephalus. There are areas of hyper- and hypointensity within the tumour’s stroma. Sagittal projections (c,e,f) ascertain the relationship between the tumour and the median brain axis. Postcontrast T1-weighted imaging shows the intensive accumulation of contrast medium (d,e)
Chapter 5
Pineal Region Tumours
513
Fig. 5.35a–f Pineoblastoma in a 3-year-old child. Т2-weighted image (а) and T1-weighted images (b,c) reveal a large tumour in the posterior portions of the third ventricle, almost isointensive to brain
tissue. The lateral and the third ventricles are dilated. After contrast enhancement (d–f), there is a heterogeneous and moderate accumulation of contrast medium in the tumour
Fig. 5.36a–c Midbrain astrocytoma in a 10-year-old child. CТ (а) shows a tumour of the left cerebral peduncle with obstructive hydrocephalus. Axial (b) and sagittal (c) T1-weighted images demonstrate
that the tumour has a relatively homogenous structure and weakly hypointensive signal. The tumour pushes lamina tecti backwards, penetrating the aqueduct of Sylvius
514
Fig. 5.37a–f Pilocytic astrocytoma in the posterior portions of the third ventricle. Т2-weighted image (а), T1-weighted image (b), and FLAIR (c) image demonstrate a small tumour causing obstructive hydrocephalus. The tumour’s MR signal is almost indistinguishable from that of brain tissue. Sagittal T1-weighted image (d), Т2-weighted image (e), and Т1-weighted (f) image with enhancement ascertains location of the tumour, the extent of compression of lamina quadrigemina, and the aqueduct of Sylvius
Chapter 5
Pineal Region Tumours
Fig. 5.38a–f Glioma of lamina quadrigemina. Axial Т2-weighted image (а), T1-weighted image before
(b,c), and after (d) enhancement reveals a small midbrain tumour with occlusion of the aqueduct of Sylvius and thickening of lamina quadrigemina. There is obstructive hydrocephalus. Sagittal T1weighted image (d), Т2-weighted image (e), and PSIF (f) ascertain the extent of lamina quadrigemina deformity
515
516
Chapter 5
Fig. 5.39a–f Glioblastoma of the right thalamus. Т2-weighted image (а) and T1-weighted image before (b) and after (c–f) enhancement
shows a tumour with necrotised core and infiltrating peripheral areas. The posterior portions of the third ventricle are deformed; initial signs of obstructive hydrocephalus are seen
Fig. 5.40a–c Ependymoma of the posterior portions of the third ventricle. Axial Т2-weighted image (а) reveals a tumour within the projection of the pineal gland. Sagittal T1-weighted image (b) and
MR myelography (c) ascertain topography and structure of the tumour. The colliculus superior is pushed downwards. The aqueduct of Sylvius is compressed
Pineal Region Tumours
517
Fig. 5.41a,b Ependymoma of the aqueduct of Sylvius in a 5-year-old child. Axial T1-weighted image (а) reveals a tumour of midbrain. Sagittal scan (b) ascertains the tumour topography. An intramedullary tumour node within the dorsal part of the spinal cord is seen at the level of С3–С6
Fig. 5.42a–c Dermoid tumour of the pineal region in a 5-year-old child. Т2-weighted image (а) reveals a heterogeneous hypointensive MR signal of the tumour’s stroma and hyperintensive MR signal from the peripherally located cysts. On axial (b) and sagittal (c)
T1-weighted images, the tumour also has a heterogeneous structure with small areas of hyperintensity in the solid part due to fatty inclusions. Concomitant changes of the shape of corpus callosum are also seen
518
Chapter 5
Fig. 5.43a–c Epidermoid tumour of the pineal region. Т2-weighted image (а) reveals a large tumour in the posterior portions of the third ventricle and the pineal region, expanding into the right lateral ventricle. The tumour has irregular and festoon-like borders. MR signal
of the tumour is isointensive to CSF in the ventricular system. The differences in signal intensity between the tumour and CSF are more obvious on axial (b) and sagittal (c) T1-weighted images
Fig. 5.44a–f Epidermoid tumour of the pineal region. Axial Т2weighted image (а) and sagittal T1-weighted image (b,c) reveals a large tumour located in the posterior portions of the third ventricle and the pineal region with expansion into the left lateral ventricle. The tumour has irregular and festoon-like borders. MR signal of the
tumour is isointensive to CSF in the ventricular system. The differences in signal intensity between the tumour and CSF are more obvious on DWI (d,e). A high and double-humped peak of lipids is seen on the MR spectrogram (f)
Pineal Region Tumours
519
Fig. 5.45a–e Lipoma of the pineal region. Axial CT (а) shows a small hypodensive area (less than –75 HU) with polygonal borders in the pineal region. On the T1-weighted image in three orthogonal projections (b–d) the tumour is markedly hyperintensive. The tumour compresses the lamina quadrigemina. The pineal gland is located in front of lipoma. On the Т2-weighted image (e) the tumour has a homogenous mildly hyperintensive signal
5.3.5 Meningiomas It is hard to estimate incidence of pineal region meningiomas. That is because by the time of diagnosis, the tumour has usually reached such a size that makes it difficult to define the site of its origin. However, only those masses that grow of the pineal region and velum interpositum are regarded as true meningiomas. Those masses that have dural attachment or expansion (such as meningiomas of the falx–tentorial angle) are not considered those of the pineal region. It is suggested that 4–8% among all tumours of the pineal region of tumours are located in this site (Konovalov et al. 1986; Konovalov and Pitskhelauri 2004). CТ and MRI features of the pineal region meningiomas resemble those of elsewhere-located meningiomas. Pineal gland calcification—better seen on CT—is usually located laterally to the tumour, not in its parenchyma, as, for instance, in cases of germinomas (Fig. 5.47). Direct digital angiography is indicated for the pineal region meningiomas, as it helps to determine the best surgical access to the tumour (Fig. 5.48). There were no cysts or perifocal oedema despite the giant size of tumours in any of our observations (Fig. 5.49). Additional contrast enhancement on MRI allows ascertaining borders and size of the tumour, and helps to determine relationships
between meningioma, tentorium cerebelli and falx cerebri, as well as to determine the extent of brainstem dislocation (Fig. 5.50). MRA provides additional information about vessels of the pineal region (arteries, veins, and sinuses).
5.3.6 Pineal Gland Cysts Despite the fact that cysts of the pineal region are revealed in 25–40% of cases at autopsy, they are rarely diagnosed during one’s lifetime. According to Lee et al. (1987), MRI detects a cystic transformation of the pineal gland only in 4.3% of cases. Even large pineal cysts rarely manifest clinically; however, when compression of the Sylvian aqueduct occurs, hydrocephalus may develop. A nontumour pineal cyst is a mass lined with collagen fibres, glial cells, and normal pineocytes. There are several explanations why these cysts form, such as degenerative changes in the pineal gland parenchyma, unification of several small cysts into a single large one, separation of the pineal recessed of the third ventricle, and impairment of normal development of the pineal gland (Mamourian et al. 1986; Wisoff et al. 1992; Klein et al. 1989; Todo et al. 1992; Stern et al. 1993).
520
Fig. 5.46a–f Cavernoma of the pineal region. Т2-weighted images
(а,b), MR myelography (c), and T1-weighted image (d) demonstrate a tumour in the posterior portions of the third ventricle, with heterogeneous structure and microhaemorrhages. The area of hypointen-
Chapter 5
sive signal on T2-weighted image is seen on the periphery of the tumour. The lateral and the third ventricles are dilated. Heterogeneous contrast enhancement of cavernoma is seen (е,f)
Fig. 5.47a–c Meningioma of the pineal region. Axial CT (а–c) reveals a large tumour with prominent homogenous enhancement. Calcification of the pineal gland is located along the anterior border of the tumour (arrow)
Pineal Region Tumours
Fig. 5.48a–f Meningioma of the pineal region. Case 1. Direct carotid
(а) and vertebral (b,c) angiography (see CT scans in Fig. 5.47) shows prominent blood supply of the tumour from the posterior circula-
521
tion area. Case 2. d Sagittal MRI visualises a large tumour with hypointensive signal and solid structure. The tumour is supplied from carotid (e) as well as of posterior circulation (f) areas
Fig. 5.49a–c Meningioma of the pineal region. MRI shows a large tumour with homogenous structure, hyperintensive signal on the
Т2-weighted image (а) and isointensive signal on the T1-weighted image (b). Sagittal T1-weighted image (c) demonstrates the extent of brainstem compression
522
Chapter 5
Fig. 5.50a–c Meningioma of the pineal region. Postcontrast T1-weighted image in axial (а), sagittal (b), and coronal planes (c). Clear-cut, in-
tensive, and homogenous contrast enhancement of the tumour allows precise differentiating between pathological and normal brain tissue
MRI reveals a round, clearly delineated mass with smooth walls, which does not differ from CSF by its intensity or has a slightly hypointensive signal in comparison with CSF, especially on T2-weighted images (Lee et al. 1987; Atlas 1991)(Figs. 5.51, 5.52). Different signal intensity between cyst and CSF is not considered pathological, as it may reflect several factors: relative separation of the cyst contents from the flowing CSF (in this case, the influence of CSF, of which decreased signal intensity becomes less prominent on T2-weighted images), higher level of protein, or remnants of old haemorrhage into the cyst (Fig. 5.53). A cyst of the pineal region is difficult to differentiate from cystic pineocytomas. Calcifications of the pineal gland are usually located within the wall of a cyst and are better vi-
sualised on CT. On MRI, there is no contrast enhancement of cyst walls. However, if tissue of the pineal gland is partially preserved, then contrast enhancement may be seen due to absence of blood–brain barrier in the pineal capillaries, which is typical for brain vessels (Sage et al. 1994). Myelographic regimens can ascertain the extent of the aqueduct of Sylvius compression and the presence of CSF flow impairment (Fig. 5.54). It is very important for the neurosurgeon to know the exact size, location of the tumour, and its relation to the quadrigeminal plate, revealed by dynamic investigations, to choose the most appropriate access to a tumour. Analysis of MRI data distinguishes the following types of interrelation of a pineal region tumour and quadrigeminal plate:
Fig. 5.51a–c Cyst of the pineal region. T1-weighted image (а) and Т2-weighted images (b,c). A small cyst of the pineal gland with regular border is seen in axial and sagittal projections. There is mild compression of the superior colliculus, but the aqueduct of Sylvius looks normal
Pineal Region Tumours
523
Fig. 5.52a-c Cyst of the pineal region. Т2-weighted images (а,b) and T1-weighted image (c). A cyst of the pineal gland with a regular border
is seen in axial and sagittal projections. Compression of the superior colliculus and (partial) of the aqueduct of Sylvius is seen
• The tumour lies on quadrigeminal plate, pushing it against • •
•
•
the midbrain tectum (Fig. 5.55а.). The tumour grows out from quadrigeminal plate, the latter is undifferentiated (or its remnants are seen). There are no severe lesions in the tegmentum of midbrain (Fig. 5.55b). The tumour grows into the stoma of the aqueduct of Sylvius, causing dislocation of the anterior portion of quadrigeminal plate into the quadrigeminal cistern. The diameter of the caudal portion of the aqueduct is almost within normal parameters (Fig. 5.55c). The tumour is predominantly located within the aqueduct of Sylvius and displaces quadrigeminal plate towards the quadrigeminal cistern along its entire length. Caudal portions of a tumour reach the fourth ventricle (Fig. 55d). The tumour is located in the posterior portions of the third ventricle, and the posterior portion of a tumour is adjacent to the oral part of the aqueduct of Sylvius (Fig. 5.55e).
Despite the fact that MRI is of great value in diagnosis of the pineal region tumours, CT plays the main role in postsurgical assessment of the extent of radical excision of tumours. That is because of difficulties of MRI data interpretation due to products of haemoglobin oxidation. However, according to our experience, blood escapes from the pineal subarachnoid space and from the bed of excised tumour rather quickly, which allows application of MRI 2–3 weeks after surgery (Fig. 5.56). However, in contrast to CT, only MRI in a phase-contrast myelography regimen can distinguish CSF flow via newly formed pathways after shunting operations, when artificial drainage pathways are created in patients with inoperable midbrain tumours (Fig. 5.57). As already mentioned, it is difficult to perform differential diagnosis of tumours of the pineal region with different histology. MR signal features and extent of attenuation on CT
are often identical in different types of tumours. Dermoid tumours, teratomas, and lipomas are those exceptions that possess specific distinguishing features. Glioma of the quadrigeminal plate causes its thickening and deformity, with signs of occlusion of the Sylvian aqueduct, and contrast enhancement is not typical for them. Gliomas growing into the pineal region tend to displace structures of the posterior portions of the third ventricle and are asymmetrically located in relation to median axis. If a calcification of the pineal gland is revealed, then it does not allow making a differential diagnosis, as that may be encountered in germ cell tumours as well as in pineal parenchymal tumours. Only in germinomas are there calcifications more dense, which are revealed in 80% of observations. It is important to determine how a calcinate is located in relation to a tumour to make differential diagnoses from meningiomas. The latter cause displacement of calcification, but not the inclusion of it into the tumour stroma, as, for instance, in germinomas. Meningiomas are typically larger and have a relatively dense structure with intensive contrast enhancement on CT and MRI. Moreover, meningiomas are usually encountered in adults. Intratumoural haemorrhages cannot serve as an additional criterion, as they are observed in benign (germinomas, ependymomas), as well as in malignant tumours (pineoblastomas, mixed germ cell tumours etc.). Multiple subependymal metastases cannot be a 100% differential criterion, even if one of the nodes is located in the pineal region (Fig. 5.58). Detection of different serum blood markers is the important test in differential diagnosis. In particular, when a patient has a tumour of the pineal parenchymal tumour, melatonin level is found to be elevated in serum; in choriocarcinoma, human chorionic gonadotropin is elevated; and in endodermal sinus tumour, alpha-fetoprotein is elevated.
524
Chapter 5
Fig. 5.53a–c Cyst of the pineal region. Т2-weighted image (а), T1-weighted image (b), and FLAIR (c) demonstrate a cyst of the pineal region. Compression of the superior colliculus and the aqueduct of Sylvius is seen
Fig. 5.54a–d Cyst of the pineal region. T1-weighted images (а,b), FLAIR (c,) and PSIF (d)
demonstrate a cyst of the pineal region. Compression of the superior colliculus and the aqueduct of Sylvius is seen
Pineal Region Tumours
525
Fig. 5.55a–e Schematic representation of relationships between tumours of the pineal region and lamina quadrigemina
Fig. 5.56a,b Germinoma of the pi-
neal region in a 14-year-old child. Sagittal T1-weighted image before surgical extraction of the tumour (а) and 2 months after surgery (b) reveals small remnants of the tumour
526
Chapter 5
Fig. 5.57a–g A midbrain tumour in a 12-year-old child. The tumour hampers CSF flow
via the aqueduct of Sylvius, which is compressed and displaced. There was an installation of a drainage system into the aqueduct. Axial (а) and reformatted sagittal (b) CT images: the drainage tube is located within the cavity of the third ventricle, and passes from the foramen of Monro via the aqueduct of Sylvius, which displaced leftwards into the fourth ventricle. Sagittal T1-weighted image (c) and Т2-weighted image (d) visualises a drainage tube within the cavity of the third ventricle, the aqueduct, and the fourth ventricle. Phasecontrast MRI detects CSF flow via the drainage tube: in asystole (e) the signal of CSF is high, and in diastole (f) it is low. g Graphic representation (pulse sinusoid) of CSF flow via the aqueduct of Sylvius
Pineal Region Tumours
527
Fig. 5.58a–c Multiple brain lymphomas. T1-weighted image with contrast enhancement demonstrates multiple tumour’s nodes located in the posterior portions of the third ventricle, within the foramina of Monro, and the bottom of the third ventricle
Refere n c e s Atlas S (1991) Intra-axial brain tumours. IN: Atlas S (ed) MRI of the brain and spine. Raven, New York, pp 223–326 Bjornsson J, Scheithauer B, Okazaki H et al (1985) Intracranial germ cell tumours: pathobiological and immunohistochemical aspects of 70 cases. J Neuropath Exp Neurol 44:32–46 Borden S, Weber A, Toch R et al (1973) Pineal germinoma: long term survival despite hematogenous metastases. Am J Dis Child 126:214–219
Fetell M, Stein B (1986) Neuroendocrine aspects of pineal tumours. In: Zimmerman E, Abrams G (eds) Neurologic clinics: neuroendocrinology and brain peptides, vol 4. Saunders, Philadelphia, pp 877–905 Ganti S, Hilal S, Stein B et al (1986) CT of pineal region tumours. AJR Am J Radiol 146:451–458 Handa H, Yamashita J (1981) Current treatment of pineal tumours. Neurol Med Chir (Tokyo) 2:147–154
Boring CC, Squires TS, Tong T (1992) Cancer statistics. Cancer 42:190-198
Hoffman J, Otsubo J, Hendrick E et al (1991) Intracranial germ cell tumours in children. J Neurosurg 74:545–551
Bruce J, Stein B (1993) Complications of surgery for pineal region tumours. In: Post K, Freidman E, McCormick P (eds) Postoperative complications in intracranial neurosurgery. Thieme, Stuttgart, pp 74–86
Huk W, Gademann G, Friedmann G (1990) MRI of central nervous system diseases. Springer, Berlin Heidelberg New York
Burlutsky A (1962) Tumours of the pineal gland. Medicine, Moscow (in Russian) Chang C, Kageyama T, Yoshida J et al (1981) Pineal tumours: clinical diagnosis, with special emphasis on the significance of pineal calcification. Neurosurgery 8:656–668 Chang T, Teng M, Guo W-Y et al (1989) CT of pineal tumours and intracranial germ cell tumours. AJNR Am J Neuroradiol 153:1039–1044 Chiechi M, Smirniotopoulos J, Mena H (1995) Pineal parenchymal tumours: CT and MR features. J Comput Assist Tomogr 4:509–517 Dempsey P, Kondziolka D, Lunsford L (1992) Stereotactic diagnosis and treatment of pineal region tumours and vascular malformations. Acta Neurochir (Vienna) 116:14–22 Edwards M, Hudgins R, Wilson C et al (1988) Pineal region tumours in children. J Neurosurg 68:689–697
Jennings M, Gelman R, Hochberg F (1985) Intracranial germ cell tumours: natural history and pathogenesis. J Neurosurg 63:155–167 Karnaze M, Sartor K, Winthrop J et al (1986) Suprasellar lesions: evaluation with MR imaging. Radiology 161:77–82 Kilgore D, Strother C, Starshak R et al (1986) Pineal germinoma: MR imaging. Radiology 158:435–438 Klein P, Rubinstein L (1989) Benign symptomatic glial cysts of the pineal gland: a report of seven cases and review of the literature. J Neurol Neurosurg Psychiatr 52:991–995 Kоnovalov А, Pitskhelauri D (2004) Treatment of tumours of the pineal region. Medicine, Moscow pp. 278 (in Russian) Konovalov A, Spallone A, Pitzkhelauri D (1996) Meningioma of the pineal region: a surgical series of 10 cases. J Neurosurg 85:586–590 Kornienko V, Ozerova V (1993) Pediatric neuroimaging. Medicine, Мoscow pp. 448 (in Russian) Lee D, Norman D, Newton T (1987) MRI of pineal cysts. J Comput Assist Tomogr 11:586–591
528 Liang L et al (2002) MRI of intracranial germ cell tumours. Neuroradiology 44:382–388 Mamourian A, Towfighi J (1986) Pineal cysts: MR imaging. AJNR Am J Neuroradiol 7:1081–1086 Manor R, Rar-Ziv J, Tadmor R et al (1990) Pineal germinoma with unilateral blindness: seeding of germinoma cells with optic nerve sheath. J Clin Neurol Ophthalmol 10:239–243 Masuzawa T, Shimabukuro H, Nakahara N et al (1986) Germ cell tumours (and yolk sac tumour) in unusual sites in the brain. Clin Neuropathol 5:190–202 Matsko D, Korshunov G (1998) Atlas of tumors of the central nervous system (the histological structure). Polenov A. neurosurgical institute. St.Petersburg, pp. 200 (in Russian) Matsutati M, Sano K, Takakura K et al (1997) Primary intracranial germ cell tumours: a clinical analysis of 153 histologically verified cases. Neurosurgery 3:446–555 Nakagawa H, Iwasaki S, Kichikawa K et al (1990) MR imaging of pineocytoma: report of two cases. AJNR Am J Neuroradiol 11:195–198 Osborn A, Rauschning W (1994) Brain tumours and tumour-like masses: classification and differential diagnosis. In Osborn A (ed) Diagnostic neuroradiology. Mosby, St. Louis Pitskhelauri D, Konovalov A, Azizian V et al (2004) Iatrogenic metastasis of pineal tumours. Vopr Neirokhir Im N N Burdenko 4:28–33; discussion 33–4 (in Russian) Russell D, Rubinstein L (1989) Pathology of tumours of the nervous system, 5th edn. Williams and Wilkins, Baltimore Sage M, Wilson A (1994) The blood–brain barrier: an important concept in neuroimaging. AJNR Am J Neuroradiol 4:601–622
Chapter 5 Sawaya R, Hawley D, Tobler W et al (1990) Pineal and third ventricular tumours. In: Youmans J (ed) Neurological surgery. Saunders, Philadelphia, pp 3171–3203 Smirniotopoulos J, Rushing E, Mena H (1992) Pineal region masses: differential diagnosis. Radiographics 12:577–596 Soijima T, Takeshita I, Yamamoto H et al (1987) CT of germinomas in basal ganglia and thalamus Neuroradiology 29:366–370 Stefanko S, Talerman A, Mackay W et al (1979) Infundibular germinoma. Acta Neurochirurg (Vienna) 50:71–78 Stern J, Ross D (1993) Stereotactic management of benign pineal region cysts: report of two cases. Neurosurgery 32:310–314 Tanaka R, Ueki K (1979) Germinomas in the cerebral hemisphere. Surg Neurol 12:239–241 Tien R, Barkovich A, Edwards M (1990) MR imaging of pineal tumours. AJNR Am J Neuroradiol 11:557–565 Todo T, Kondo T, Shinoura N et al (1992) Large cysts of the pineal gland: a report of two cases. Neurosurgery 29:101–106 Winfield J (1985) Pineal region tumour. In: Long D (ed) Current therapy in neurological surgery 1985–1986. Decker, Philadelphia, pp 31–69 Wisoff J, Epstein F (1992) Surgical management of symptomatic pineal cysts. J Neurosurg 77:896–900 Zee C, Segall H, Apuzzo M et al (1991) MR imaging of pineal region neoplasms. J Comput Assist Tomogr 15:56–63 Zimmerman R, Bilaniuk L (1982) Age-related incidence of pineal calcifications detected by CT. Radiology 142:659–662 Zulch K (1986) Brain tumours: their biology and pathology, 3rd ed. Springer, Berlin Heidelberg New York
Chapter 6
Sellar and Parasellar Tumours
6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11 6.12 6.13 6.14 6.15 6.16 6.17 6.18 6.19 6.20
Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Anatomy .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pituitary Anomalies .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . “Empty” Sella Turcica .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Pituitary Adenomas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Craniopharyngioma .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Gliomas of the Optic Nerves, Chiasm, and Hypothalamus . Germinomas .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Teratoma, Epidermoid Tumours, and Dermoid Tumours ... . Chordoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hamartomas of the Tuber Cinereum .. . . . . . . . . . . . . . . . . . . . .. . Langerhans Cell Histiocytosis .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ratke’s Cleft Cysts .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Meningioma .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Neurinoma of the Fifth Cranial Nerve .. . . . . . . . . . . . . . . . . . . .. . Metastases .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Paragangliomas .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Arachnoid Cyst .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vascular Disorders: Aneurysm .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Inflammatory Disorders .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .
6.1
Introduction
529 529 531 531 535 556 573 579 580 585 585 591 592 594 594 598 598 598 605 605
The sellar region encompasses the sella turcica with adjacent structures, the CSF spaces located nearby, hypothalamus, the bottom of the third ventricle, and cavernous sinuses (Fig. 6.1).
6.2
Anatomy
The sella turcica (literally, “Turkish saddle”) has a spherical shape and is located in the depression of the upper surface of the sphenoid bone, which resemble a saddle in sagittal projection, hence its name. The sella turcica is delimited by the prechiasmal sulcus, tuberculum sellae, and by the anterior clinoid processes. The posterior border of the sella is its dorsum, from where the posterior clinoid processes extend, and to which tentorium is attached. The clivus is situated at the back of the dorsum sellae. The sphenoidal sinus is located beneath. It is
6
usually separated by a vertical bony septum. If high-resolution CT is performed with multiplanar reformation, then even the thinnest bone structures and septi are clearly visualised. The bone margin of sella is difficult to visualise on MRI. Its thin cortical bone is practically indistinguishable from the sphenoidal sinus, which contains air and is situated forwards and beneath. Its posterior aspect becomes visible due to hyperintensive signal of bone marrow inside the back of sella. The exit from sella turcica is delimited by dura mater—the sellar diaphragm. The suprasellar cistern is located above it. This cistern contains the circle of Willis with the anterior cerebral arteries, the anterior and the posterior communicating arteries, and bifurcation of the basilar artery. In the anterior aspect, the cistern is delimited by the basal brain surface and the interhemispheric fissure; from the medial aspect it is delimited by the internal surface of the temporal lobe and from the posterior aspect, it is delimited by the prepontine and interpeduncular cistern. In the centre of the suprasellar cistern, the optic chiasm is situated, which is in front of infundibulum. In the normal state, the chiasm is situated above the sella turcica. In some cases, it may be situated above the tuberculum sella (the anterior location of the chiasm seen in 9% of cases) or above the dorsum of the sellae (the posterior location of the chiasm seen in 11% of cases). The knowledge of these anatomic variants is important for correct interpretation of visual signs and for the correct choice of surgical approach to the sellar pathological processes. The hypothalamus forms the ventral and the rostral part of the wall of the third ventricle in which the chiasmal and the infundibular exfoliations exist. Mamillary bodies are located backwards to the infundibulum. The tuber cinereum is situated between them. Tuber cinereum is a lamina of grey matter of the third ventricle. The tuber infundibulum lies opposite of the tuber cinereum in the inferior direction. To the lateral aspect, the paired cavernous sinuses lie. They are represented by multichamber venous cavities in which the following structures are situated: the cavernous segment of the internal carotid artery, the sixth, third and fourth cranial nerves, and branches of the trigeminal nerve (in the lateral walls of the sinus). The pituitary gland consists of two anatomically delineat-
530
Fig. 6.1a,b Relationship between anatomic structures of the sellar
Chapter 6
and the parasellar regions by Baron and Mayorova (1982). а Anatomic relationships between the carotid arteries, the cavernous sinus, and the sphenoid bone. b The diaphragm of the sella turcica and the pitu-
itary capsule. 1 Dura mater, 2 internal carotid artery, 3 diaphragm of the sella turcica, 4 pituitary, 5 pituitary capsule, 6 ophthalmic nerve, 7 oculomotor nerve, 8 sphenoidal sinus, 9 trigeminal nerve, 10 cavernous sinus, 11 abducens nerve
ed lobes. According to the commonly accepted concept, the anterior lobe, or adenohypophysis, has an ectodermal origin and develops from the so-called Ratke’s pouch (a process of nasopharyngeal tissue that is formed in the embryonic period). Alternatively, some researchers believe that the adenohypophysis may originate from neuroectoderm. The posterior lobe, or neurohypophysis, originates from the diencephalic neuroectoderm. The anterior lobe loses its connections with nasopharynx and develops in to a pure neuroendocrine gland. The posterior lobe retains its connections with the hypothalamus throughout life, via the pituitary stalk (the hypothalamic pituitary tract), and becomes a site where hormones accumulate, are synthesised in the hypothalamus, and transported via axons of the pituitary stalk. The anterior lobe of the pituitary gland fills the anterior parts of the sella turcica, occupying 75% of the entire pitu-
itary gland volume. It has two lateral wings that go backwards, frequently up to the dorsum sellae. In rare cases, the lateral wings of the anterior lobe completely encircle the posterior lobe in a way that occupies the central potion of the gland, filling only 10–25% of the sella turcica volume, and in this case, it is always located along the median axis being adjacent to the dorsum sellae. The anterior and the posterior lobes of the pituitary are clearly distinguished by MRI (Fig. 6.2). The anterior lobe resembles cerebral white matter in signal intensity in all pulse sequences, whereas the posterior lobe is clearly hyperintensive on Т1-weighted imaging and less hyperintensive on T2-weighted imaging. The entire gland and the pituitary stalk accumulate contrast medium intensively after intravenous contrast enhancement (CE). The substrate responsible for hyperintensive signal in the posterior lobe is not yet elucidated. Fig. 6.2a,b MRI of the sellar and the
parasellar region of a 28-year-old healthy volunteer in the coronal (а) and the sagittal projections (b) on T1 -weighted images identifies clear difference in MR signal between the adeno- and the neurohypophyse. The infundibulum lies along the median line. 1 Adenohypophysis, 2 neurohypophysis, 3 infundibulum, 4 optic chiasm, 5 cavernous sinus, 6 intracavernous segment of the internal carotid artery, 7 sphenoidal sinus, 8 mamillary bodies
Sellar and Parasellar Tumours
However, presence of hyperintensive signal is certainly connected with the functionally intact posterior lobe, e.g. in diabetes insipidus, hyperintensity of signal is absent. Whatever the origin of hyperintensive signal is, the posterior lobe of the pituitary gland is a clearly visible landmark. The anterior lobe of the pituitary gland is subdivided onto the tuberal, the intermediate, and the distal sections. Тhe tuberal section consists of a layer of pituitary tissue, that is a part of the medial process of the hypothalamus and the anterior section of the infundibulum. In humans, the intermediate section is very small and may contain small cysts (cysts of the intermediate section or colloid cysts) and be an origin of Ratke’s pouch (fissure) cysts. The distal section forms a large intrasellar part of the anterior part of the pituitary gland. Adenohypophysis produces prolactin (of lactotrophs), somatotropic hormone (of somatotrophs), follicle-stimulating hormone, and luteinising hormone (gonadotrophs), corticotropin (adrenocorticotropic hormone [ACTH]), and melanocyte-stimulating hormone precursors (of corticotrophs). The posterior lobe, the infundibulum, the supraoptic, and the paraventricular nuclei of the hypothalamus form the so-called neurohypophysis. The posterior lobe contains pituicytes, which are non-secreting cells, as well as cells accumulating antidiuretic hormone and oxytocin. The posterior lobe of the pituitary is supplied with blood from the inferior pituitary artery and from the branch of the meningeal pituitary gland trunk originating from the cavernous segment of the carotid artery. On lateral carotid angiograms, the posterior part of the pituitary gland may be seen. The superior pituitary arteries originating from the supraclinoid segment of the internal carotid artery and the posterior communicating arteries (they are not usually visualised on angiography) supply the plexus around the base of the pituitary stalk and the median eminence, and then supply the anterior part of pituitary gland, but indirectly via the portal the pituitary system. Such a sophisticated blood supply leads to rapid contrast medium accumulation by the posterior part of the pituitary and the infundibulum (due to their direct blood supply), which is seen on fast dynamic MRI, whereas the anterior part of the pituitary gland accumulates it after a delay due to the portal pituitary system. The adenohypophysis is more vulnerable in ischemic events, which leads to infarction of the anterior part of the pituitary gland in different pathological conditions, for instance, in the postnatal period (Sheehan’s syndrome). Venous drainage from the pituitary proceeds via veins with inlets into the cavernous sinuses. The diaphragm of the sella turcica is a layer of dura mater covering the pituitary gland. The central aperture exists in its upper part, through which the infundibulum passes. The pituitary gland weights 0.5 g in adults, and is the only important structure located in sella turcica. Dimensions of the pituitary are variable, especially its height. On average, it is 10–12 mm in width, 8 mm in the anterior-posterior direction, and 3–8 mm in height. In children younger than 12 years of age, sizes of the pituitary gland in the sagittal projection are about 6 mm or less, and the gland has a flat or mildly convex surface (Dietrich 1995). The pituitary gland is largest
531
in adolescents and pregnant women, due to its physiological hypertrophy (Elster et al. 1990, 1991). In female adolescents, the pituitary gland may reach 10 mm in height and may have prominent external margins. The prominence of the upper margin is also seen in children with premature sexual development (Horvath et al. 1999). Several changes may be seen in male adolescents, but they are less obvious. In conclusion, the pituitary gland should fill the whole sella turcica, but height may be variable.
6.3
Pituitary Anomalies
The pituitary gland and hypothalamus anomalies frequently coexist with other anomalies of structures located along the medial axis such as those of optic nerves, septum pellucidum, and bones of skull base and palate, etc. (Naidich 1983). Pituitary gland and hypothalamus dysfunction are most often clinically manifested by growth retardation (Hoyt 1970).
6.3.1 Pituitary Gland Hypoplasia In many cases, routine X-ray craniography and CT shows a small and flattened sella turcica. A hypoplastic pituitary gland may be smaller than a normal one on CT, but it occupies the usual location. MRI can better visualise the pituitary gland and the pituitary stalk. The other group of congenital anomalies may be identified only with the help of MRI. Thus, in patients with congenital nanismus, in whom growth hormone is deficient or other hormonal deficits of the adenohypophysis (Fujisawa 1987; Kelly et al. 1988) are found, a small sella turcica, a small anterior part of the pituitary gland, absence of normally hyperintensive signal of the posterior part of the pituitary gland, absence of the distal part of the pituitary stalk, or the abnormal hyperintensive area in tuber cinereum of the hypothalamus may be identified. Almost all patients have a history of complicated or traumatic delivery. It is suggested that the connatal trauma causes rupture of the pituitary infundibulum and its vascular membrane. This causes isolation of the pituitary gland from the stimulating effects of the hypothalamus; it also causes impairment of its blood supply and decrease of secretion of hormones of the adenohypophysis. The function of the posterior part of the pituitary gland usually remains intact (Fig. 6.3). It should be distinguished from lipoma of the bottom of the third ventricle (Fig. 6.4). In the latter cases, the hyperintensive signal of the neurohypophysis remains in the sella turcica cavity.
6.4
“Empty” Sella Turcica
The term empty sella turcica in a certain sense is a radiological definition: the sella turcica is always filled with CSF, and it contains remnants of the pituitary gland as well as the chiasm and optic nerves from time to time. Dilated subarachnoid space combined with congenital and acquired diaphragm in-
532
Fig. 6.3a–c MRI of a 4-year-old child with clinical picture of nanism. On Т1-weighted images (а,b) and Т2-weighted images (c), a small sella turcica is seen and the small and flattened anterior lobe of the pituitary. The commonly hyperintensive signal of the poste-
Fig. 6.4 МRI of an 8-year-old child. A small lipoma is seen on the bottom of the third ventricle. Hyperintensive MR signal of the neurohypophysis is preserved in the cavity of the sella turcica
sufficiency is characteristic for the “empty” sella turcica (Carmel 1985). Mizetskaya (1984) distinguished two variants of the empty sella turcica: “complicated” and “noncomplicated”. The latter does not manifest clinically and usually is an occasional neuroimaging finding. Complicated empty sella turcica manifests itself with certain clinical signs. Primary and secondary empty sella turcica are distinguished. Primary empty sella turcica develops due to several physiological or pathological conditions that lead to reduction of the pituitary volume: climax, infarction or necrosis of
Chapter 6
rior lobe of the pituitary and the distal part of the pituitary stalk are absent. Abnormal area of hyperintensive signal in tuber cinereum of the hypothalamus is seen
the pituitary gland, infarction or autolysis of the pituitary adenoma, and rupture of the nontumour intrasellar cyst. Primary empty sella turcica is mainly encountered in females after frequent pregnancies or long-term hormone use. The most typical clinical manifestations of primary empty sella turcica are intermittent vision disturbances (changes in the fields of vision, amblyopia, and optic disc abnormalities), the combination of refractory arterial hypertension with obesity, reduction of the pituitary-associated sexual function, and pituitary–suprarenal and pituitary–thyroid functions, etc. Secondary empty sella turcica develops after surgery, irradiation, or combined treatment of different conditions of a chiasmal–sellar region, due to destruction of the pituitary diaphragm and descending of the suprasellar cisterns into the sella turcica. The clinical picture of secondary complicated sella turcica is variegated, and is mainly determined by the syndrome that has taken place before treatment of pituitary adenoma. On CT, dilated and deepened sella turcica is usually seen. On rare occasions after quantitative reformation in sagittal and coronal planes, the pituitary stalk may be visualised within the sella turcica cavity (Fig. 6.5). On MRI, changes of the pituitary gland are better seen as the gland flattens, or in cases when it acquires a shape of a thin rim that repeats contours of the bottom of the sella turcica (Figs. 6.6, 6.7). Differential diagnosis should be made from intrasellar cysts. Position of the pituitary stalk is the pivotal sign in these cases. In cases of empty sella turcica, the stalk is normally positioned; if cysts are present, then the stalk is compressed or displaced. In complicated cases, CT cisternography with water-soluble contrast media is helpful in empty sella turcica diagnosis (Fig. 6.8).
Sellar and Parasellar Tumours
533
Fig. 6.5a–c “Empty” sella turcica. Axial CT (а) with subsequent reformation in sagittal (b) and coronal (c) planes reveals widened and deepened sella turcica. The pituitary infundibulum is seen along the median axis in the central part of the sella turcica. The density of the sella content is identical to that of the CSF
Fig. 6.6a–c “Empty” sella turcica. T2-weighted imaging in axial (а) and coronal planes (b), and sagittal T1-weighted imaging (c) reveals the markedly deepened sella turcica. In all sequences, the pituitary
infundibulum along the median axis in the central part of the sella turcica is seen. On the bottom, the hypoplastic tissue of the adenohypophysis is observed
534
Fig. 6.7a–f “Empty” sella turcica. On axial T2-weighted images (а) and sagittal Т1-weighted images (b), the markedly deepened and widened sella turcica is revealed. On the bottom, the hypoplastic tissue of the adenohypophysis is seen. The pituitary infundibulum is
Chapter 6
pushed against the dorsum of the sella turcica. Coronal Т1-weighted imaging (c), T2-weighted imaging (d), FLAIR (e), and on myelography (f): clear connection between the content of the sella turcica and the CSF of the suprasellar cistern is seen
Sellar and Parasellar Tumours
535
Fig. 6.8a–c “Empty” sella turcica. CТ cisternography in axial (а) and coronal (b), and in sagittal reformation (c) reveals wide connection between the CSF of the sella turcica content and the CSF of the suprasellar cistern. The pituitary infundibulum is clearly seen. On the bottom, the hypoplastic tissue of the adenohypophysis is demonstrated
6.4.1 Proximity of Siphons Proximity of siphons of the carotid arteries is a rare abnormality of the parasellar region, which is characterised by medial displacement of siphons of the internal carotid arteries at the level of the cavernous sinuses, with possible compression of the adenohypophysis in the sella turcica cavity. On sagittal MRI, it may resemble the endosellar pituitary adenoma. Diagnosis is made based on the coronal scans and angiography (Fig. 6.9). This anatomic variant of the internal carotid arteries location should be taken into account when transnasal approach is planned in surgery of the sella turcica cavity to avoid injury to vascular walls.
6.5
Pituitary Adenomas
Pituitary adenomas rank third among tumours of the CNS and make up (according to most authors) 4–17% of all brain tumours (Kadashev 1989, 2007). In nonselective pathological studies in multiprofiled hospitals, the incidence varied from 2.7 to 27% (Russell and Rubenstein 1989; Schwartzberg 1992). These are mainly adult cases; these tumours are rarely seen in children (Osborn 2004). The peak incidence is between 20 and 40 years. Pituitary adenomas are usually well delineated and separated from the normal pituitary gland by a pseudocapsule of thick tissue containing reticulin. In some cases, margins of adenoma are hardly visible, the pseudocapsule is weakly formed, and adenoma cells expand into the normal glandular tissue adjacent to a tumour (Scheithauer et al. 2006). Usually the pituitary adenomas are classified according to their size: less than 10 mm (microadenomas), greater than 10 mm (macroadenomas). Clinicians subdivide adenomas according to presence, absence and, if present, type of hormonal activity. Such terms as prolactinoma and nonfunctioning mac-
roadenoma are common in clinical language. Electronic microscopy and immunocytology allowed construing a classification more ideally based on the type of hormone produced by a tumour, the origin of tumour cells, and their histological ultrastructure. Clinical manifestations of adenomas depend on the size of a tumour, presence, absence, and, if present, the type of a hormone produced and the extent of extrasellar expansion. In approximately 75% of patients with adenomas, there are clinical signs caused by secretion of various hormones; the remaining 25% of cases tumours are nonfunctioning (Kovacs et al. 1985). The most frequently seen tumour of the pituitary gland that is hormonally active is prolactinoma—a tumour originating from the adenohypophysis cells that secret prolactin (lactotrophs), which constitutes approximately 40–50% of hormonally active adenomas and about 30% of all adenomas (Osborn 2004). Prolactin hypersecretion may cause amenorrhea, galactorrhea, infertility, reduction of libido, or impotence. In males and females in the postclimax period, effects of elevated prolactin level are less conspicuous. These tumours often produce clinical manifestations if they reach a large size and begin to compress optic pathways and cause impairment of pituitary function. It should be mentioned that elevated prolactin level is not an obligatory sign of prolactinoma. It may be elevated in the suprasellar tumours that compress the hypothalamus or the pituitary stalk (the “stalk dissection effect”). The same may be seen after use of several drugs (especially phenotiazines) and in primary hypothyroidism. However, hyperprolactinemia caused by these conditions is not severe. Only if plasma prolactin reaches 100–150 ng/ ml it is considered typical for prolactinoma. The normal level of plasma prolactin is <20 ng/ml (Hemminghytt 1983; Singer 1990). Among all patients with pituitary adenomas, children and adolescents account for 2–6%. The most frequent tumours in children are prolactinomas, then corticotropinomas, soma-
536
Chapter 6
Fig. 6.9a–d Close location of the internal carotid artery siphons, “kissing siphons”. Sagittal Т1-weighted image (а) shows that the adenohypophysis is probably enlarged in the anterior–posterior direction. Axial Т2-weighted imaging (b) and coronal Т1-weighted imaging (c) reveals the deformity of the pituitary by the medially displaced siphons of the internal carotid arteries. MRA confirms the anatomic variant of the internal carotid artery siphons location (d)
totropinomas, thyroprolactinomas, and finally adenocarcinomas. Corticotropinomas and prolactinomas are more frequent in girls (2:1 and 3:1, respectively), аnd somatotropinomas are more frequent in boys (5:1). Other frequently encountered and hormonally active tumours are somatotropinomas and adrenocorticotropinomas (the latter produce ACTH). The tumours originating from cells producing the growth hormone (somatotrophs) cause acromegaly in adults and gigantism in children. The tumours originating from cells that produce ACTH (corticotrophs) cause Cushing’s disease, which is the most severe endocrine disorder. It is more frequently seen in females (75%). Nelson’s syndrome is also caused by ACTH hypersecretion and is the result of continued growth of ACTH-producing adenoma in patients after adrenalectomy. Continued secretion of ACTH causes stimulation of skin melanocytes with subsequent hyperpigmentation. Adenomas that cause Nelson’s syndrome often reach large size and expand beyond the sella turcica. Rarely adenomas originating of thyrotrophic do occur (they produce thyroid-stimulating hormone [ТSH]) or gonadotrophs (they produce follicle stimulating hormone [FSH] and/ or luteinising hormone [LH]). In approximately 10% of cases,
the pituitary adenomas secrete more than one hormone. Adenomas secreting prolactin and the growth hormone are the most frequent among the multihormonal adenomas. Adenohypophysis cells producing different hormones are characterised by certain topography within the pituitary. Cells that secrete prolactin and the growth hormone are laterally positioned; ACTH-, TSH-, and FSH/LH-secreting cells are centrally positioned. These findings are of certain importance, as they indicate the sites of initial growth of various types of adenomas. In contrast to hormonally active tumours, which manifest by signs of a certain hormone hypersecretion, the cause of clinical manifestations of a nonfunctioning adenoma is compression or invasion of the adjacent structures. Hormonally inactive adenomas usually reach large size by the time of clinical signs appear. They expand upwards into the suprasellar cistern, laterally into cavernous sinuses, or downwards into the sphenoidal sinus. Compression of optic nerves causes vision impairment. The continued upward growth causes compression of the third ventricle and occlusion of the foramina of Monro, which contributes to obstructive hydrocephalus. Expansion into cavernous sinuses causes compression of cranial nerves that pass there, which may lead to diplo-
Sellar and Parasellar Tumours
537 Fig. 6.10a,b Tumour of the posterior lobe
of the pituitary. Sagittal (а) and coronal (b) Т1-weighted imaging reveals that the neurohypophysis is enlarged, but its image is still vivid. The adenohypophysis is compressed
Fig. 6.11a,b X-ray craniogram of the sella
turcica in cases with pituitary tumours. а Moderate enlargement of the sella turcica, depression of its bottom. b Balloon-shaped sella turcica: the entry is widened, the bottom is depressed, the dorsum is thinned, and the sella has two contours
pia and anaesthesia of the face. Compression of the rest of the pituitary gland mainly causes anterior lobe dysfunction. Involvement of neurohypophysis and the pituitary stalk may cause diabetes insipidus, which is a rare and late manifestation of adenomas of the posterior part of the pituitary gland (Fig. 6.10). In rare cases, the pituitary adenoma may be manifested by the infarction of the pituitary gland due to intratumoural haemorrhage. A large clinical study (136 patients) allowed Kadashev (1989) to subdivide adenomas as follows: • According to size –– Normal sella turcica, small (16–25 mm) –– Intermediate (26–35 mm) –– Large (36–59 mm) –– Giant (>60 mm) • According to the direction of growth –– Infrasellar: into the sphenoidal sinus or nasopharynx –– Antesellar: towards the platform of the sphenoid bone, into the ethmoid labyrinth –– Retrosellar: behind the dorsum sellae, onto clivus, with destruction of the dorsum sellae, or passing by and onto the clivus, beneath dura mater
–– Laterosellar: into the cavernous sinus or under dura mater of the middle cranial fossa
–– Suprasellar
Results of pituitary adenoma treatment depend on many factors, mostly on timely diagnosis, stage of development, and the type of disease. Neuroimaging findings of pituitary tumours in children as well as in adults are identical, but the most prominent changes are seen in prolactinomas and hormonally inactive tumours, and the less prominent in corticotropinomas. On craniograms, changes of the sella turcica depend on the size of a tumour: in microadenomas, its size remains normal, or certain deepening of its bottom and asymmetry are seen. In large and giant tumours the size of the sella turcica increases; it bottom descends and often becomes bilevel, the dorsum sellae becomes thinned and rectified, and the entrance widens (Fig. 6.11). On CT, the destruction of walls of the sella turcica is demonstrated. Pituitary tumours may expand in the parasellar space into the middle cranial fossa or forwards onto the bottom of the anterior cranial fossa, into the sphenoidal sinus
538
cavity, and onto the cells of the ethmoid bone. Cysts are found in prolactinomas in 73% of cases, and intratumoural calcifications in 80% of cases. The latter often look like dot-like foci on the tumour margins. The sellar tumours with different components of growth are better seen when the study is performed in the coronal plane or when using coronal and sagittal reformations (Figs. 6.12–6.14). After CE, the density of adenomas increases markedly (Figs. 6.15, 6.16). However, the extent of tumour CE depends on the combination of the solid and the cystic parts (Fig. 6.17). CT use significantly widens the capacities to diagnose pituitary tumours at different stages of the disease, and acquires more precise data about the size and the expansion of the tumour, especially when 2D and 3D reconstruction modalities are used (Figs. 6.18–6.20). Advancements in presurgical assessment of patients with large pituitary tumours that grow around the siphons of the internal carotid arteries appeared when a complex CT approach
Chapter 6
was implied. To this end, we used the combination of preliminary standard intravenous CE, which was followed by delayed CT angiography. That allowed visualising simultaneously the structure of a tumour and the arteries within and outside of the lesion (Fig. 6.21). More invasive imaging techniques such as CT cisternography became adopted for large pituitary tumours that cause destruction of the skull base bones and concomitant liquorrhea (Fig. 6.22). However, even with modern CT scanners, diagnosis may be established only in 87.7% of all cases (including micro- and macroadenomas). At present MRI has become the pivotal technique for the diagnosis of pituitary adenomas and for the differential diagnosis from other tumours. Our data of diagnoses with CT (over than 300 patients) and MRI (over 600 patients) allow us to state the undoubted advantages of MRI, especially in cases of microadenomas. The most informative are images of the sella turcica in sagittal and coronal projections, which pre-
Fig. 6.12a–c Pituitary adenoma. Axial CT with CE in axial (а,b) and coronal planes (c): a homogenously hyperdensive tumour is revealed
that fills the cavity of enlarged sella turcica and grows into the suprasellar space. The contours of a tumour are clear-cut and even
Fig. 6.13a–c Pituitary adenoma. CT with CE in axial (а,b) planes and with sagittal reformation (c) reveals a homogenously hyperdensive tumour that fills the cavity of enlarged sella turcica, with suprasellar, laterosellar, and infrasellar growth
Sellar and Parasellar Tumours
539
Fig. 6.14a–c Pituitary adenoma. On CT with CE in axial (а,b) planes and with coronal reformation (c), a homogenously hyperdensive tu-
mour is revealed, which fills the cavity of enlarged sella turcica, with suprasellar, laterosellar, and retrosellar growth
Fig. 6.15a–c Pituitary adenoma. A series of axial CT (а–c) reveals a heterogeneously hyperdensive tumour that fills the cavity of enlarged sella turcica, with suprasellar and retrosellar growth
540
Chapter 6
Fig. 6.16a–c Pituitary adenoma. On CT before (а) and after CE (b,c) a hyperdensive tumour is revealed that fills the cavity of enlarged sella
turcica and grows into the suprasellar space. Its density increases after CE
Fig. 6.17a–c Pituitary adenoma. CT before (а) and after CE (b,c) a tumour with endo- and suprasellar growth is revealed. The density of its solid component increases after CE
Sellar and Parasellar Tumours
541
Fig. 6.18a–f Pituitary adenoma. Axial CT before (а,b) and after CE (c,d): a tumour is revealed that fills the cavity of enlarged sella turcica,
with suprasellar and laterosellar growth. Its density increases after CE. Sagittal (e) and coronal (f) reformation give additional information about the tumour growth
542
Fig. 6.19a–f Pituitary adenoma. Axial CT (а,b) reveals a skull base tumour that markedly destroys the sphenoid bone and sella turcica elements. Sagittal (c) and coronal (d) reformation give additional
Chapter 6
information about the tumour growth. 3D CT of skull base bones ascertains the extent of bone destruction: view from above (e) and from beneath (f)
Sellar and Parasellar Tumours
543
Fig. 6.20a–f Pituitary adenoma. Axial CT with CE (а–c) reveals a skull base tumour that markedly destroys the sphenoidal bone and sella turcica elements. Sagittal reformation (d) ascertains the tumour growth in sagittal plane. 3D CT of skull base bones ascertains the extent of bone destruction: view from beneath (e) and from above (f)
544
Chapter 6
Fig. 6.21a–f Pituitary adenoma. Axial CT with CE (а–c) reveals a tumour with supra-, latero-, and retrosellar growth. CT AG visualises a tu-
mour and the brain base cerebral arteries simultaneously and ascertains their spatial relationships. d,e 2D reformation, f 3D reconstruction
Fig. 6.22a–c Pituitary adenoma. Coronal CT with CE (а) reveals a tumour with supra- and laterosellar growth. CT cisternography done for nasal liquorrhea (b,c) reveals how a tumour grows in relation to the CSF spaces and the ventricular system
Sellar and Parasellar Tumours
545 Fig. 6.23a,b Pituitary microadenoma.
Sagittal (а) and coronal (b) Т1-weighted images reveal enlargement of the anterior lobe of the pituitary. In the left half of the pituitary, a hypointensive area is seen. The infundibulum is displaced rightwards. Partial compression of the adjacent portion of the cavernous sinus is detected
Fig. 6.24 Pituitary microadenoma. On the coronal Т1-weighted imaging, a round, hypointensive area roughly 5 mm in size is seen in the right half of the adenohypophysis, with an evaginated superior margin
cisely differentiates tumour expansion in relationship to the pituitary itself (Fig. 6.23). Diagnosis of pituitary microadenomas (<10 mm in size) should be based on mainly clinical and endocrinological data, and neuroimaging techniques help additionally to confirm or to rule out the diagnosis. As the sizes of hormonally active microadenoma may comprise only a few millimetres (Fig. 6.24), MRI should be done with high spatial resolution. If microadenoma is suspected, then slice thickness should be 2–3 mm for spin echo pulse sequence, and 1–1.5 mm for spoiled gradient recalled (SPGR) or less. Neuroimaging of adenomas takes into account the direct features of a tumour as well as indirect signs. “Indirect” features of microadenoma are asymmetry of the upper adenohypophysis contour, asymmetrical descent of the bottom, and displacement of infundibulum (Fig. 6.25). At present, we do not perform CT to diagnose pituitary tumour in the case of the clinical picture of adenoma if the sella turcica has normal size on a craniogram.
On MRI, the normal tissue of the adenohypophysis is homogenous and isointensive to brain tissue. Microadenomas are usually characterised by prolonged relaxation times and appear on T1-weighted images as hypointensive areas compared with the surrounding tissue of the adenohypophysis (Fig. 6.26). On T2-weighted images, these areas are hyperintensive (Figs. 6.27, 6.28). However, these changes may sometimes be mildly pronounced (Fig. 6.29). According to our data, the sensitivity of T1-weighted imaging in imaging of the tumour is higher than that of T2-weighted imaging. It is explained by close location of the CSF spaces, hyperintensive in this sequence, and frequent artefacts of carotid siphons pulsation in the phase-encoding direction. Prominent characteristic hyperintensity appears on T1-weighted images if a haemorrhage into the tumour tissue develops (Figs. 6.30, 6.31). After CE, the majority of microadenomas accumulate and expand into the adenohypophysis tissue. That is why borders between the tumour and the pituitary may smoothen on postcontrast images (Fig. 6.32). In these cases bolus dynamic scanning becomes effective, as it differentiates between microadenoma and the pituitary issue more precisely—the former shows slower enhancement (Figs. 6.33–6.35). Especially informative is dynamic scanning in isointensive tumours (Huk et al. 1990; Sakamoto et al. 1991; Rang et al. 2002). It is noteworthy that if an MR picture of microadenoma is present, then the history should always be taken into account as well as clinical manifestations and endocrinological tests. Only this complex approach allows differentiating between Cushing’s disease, Nelson’s syndrome, etc. Tumours >10 mm in size are related to macroadenomas. It is easy to visualise them on modern CT and MR scanners. Less easy is the differential diagnosis from other mass lesions of the chiasmal–sellar region. If a tumour is relatively small, then it fills only sella turcica. However, in most of our observations, tumours had extrasellar growth. In such cases, the distribution of the process should be ascertained as well as its spatial relationship to parasellar structures, i.e. the chiasm, optic nerves, the internal carotid artery, the cavernous sinus,
546
Chapter 6 Fig. 6.25 Pituitary microadenoma. Coronal
Т1-weighted imaging shows an adenoma of the right half of the adenohypophysis with growth into the right cavernous sinus. The infundibulum is displaced leftwards
Fig. 6.26a,b Pituitary microadenoma.
Coronal (a) and sagittal (b) Т1-weighted images reveal an adenoma of the left half of the adenohypophysis
Fig. 6.27a,b Pituitary microadenoma.
Т2-weighted imaging (а) and Т1-weighted imaging (b) reveals an area of MR signal change in the left lobe of the adenohypophysis, hyperintensive on Т2-weighted image and hypointensive on Т1-weighted image
Sellar and Parasellar Tumours
547
Fig. 6.28a–c Pituitary microadenoma. Т1-weighted images (а,b) show a hypointensive tumour. On the Т2-weighted image, the microad-
enoma is hyperintensive (c)
Fig. 6.29a–c Intrasellar tumour of the pituitary. T1-weighted images (a,b) show a hypointensive tumour. The infundibulum of the pitu-
itary is displaced rightwards. On the Т2-weighted image (c), there are less obvious differences between the tissue of a tumour and the adenohypophysis
Fig. 6.30a–c Haemorrhage into the adenoma of the pituitary. Т2-weighted image (а) and Т1-weighted images (b,c) show a heterogeneous signal change in the tissue of and intrasellar tumour of the pituitary. Т1-weighted imaging visualises signal changes typical for haemorrhage
548
Chapter 6
Fig. 6.31 Haemorrhage into the adenoma
of the pituitary. Coronal T1-weighted image shows a hyperintensive area in the right half of the sella turcica (due to methaemoglobin) in the zone of intratumoural haemorrhage. The infundibulum of the pituitary is displaced leftwards
Fig. 6.32a,b Pituitary microadenoma. Т1-
weighted image (а) before CE shows a microadenoma of the left lobe of the adenohypophysis (arrow). The infundibulum of the pituitary is displaced rightwards. After CE (b), intensive accumulation of contrast medium is seen in the microadenoma as well as in the normal tissue of the pituitary. Borders between the pituitary and the tumour are smoothened. Cavernous sinuses intensively accumulate contrast medium
Fig. 6.33a–d Pituitary microadenoma. Coronal Т1-weighted images
before (а) and after CE (b) reveal a small tumour in the left lobe of the adenohypophysis. The infundibulum of the pituitary is displaced to the side where the tumour is situated. After CE, borders between the tumour and the pituitary became less clear. Dynamic MRI before
(c) and 35 s after (d) bolus CE demonstrates the borders between the tumour (which accumulates contrast medium slower than pituitary does) and the intact part of the pituitary (which has already accumulated contrast medium)
Sellar and Parasellar Tumours
Fig. 6.34a–h Pituitary microadenoma. A series of coronal MR images before (а,b) and after (c,d) CE: a small tumour is revealed in the right lobe of the adenohypophysis. The tumour is isointensive with the pituitary tissue on images before CE. The tumour accumulates
549
contrast medium slower than the adenohypophysis does. Dynamic MRI before (e) and 35 s after bolus CE: diagnosis of microadenoma becomes more obvious (f–h)
550
Chapter 6
Fig. 6.35a–f Microadenoma of the right lobe of the adenohypophysis. Sagittal (а) and coronal T1-weighted images (b) before and after CE (c) do not reveal any significant differences in the MR signal of the two lobes of the adenohypophysis. The infundibulum of the pituitary is situated along the median axis. On a series of the dynamic MRI before and 30 s (d) and 60 s (e) after bolus CE, a microadenoma
is seen in the right lobe of the adenohypophysis as a small area of low enhancement. f Diagram of enhancement in the points of measurement in the adenohypophysis tissue, with a characteristic delay of the accumulation of contrast medium in microadenoma within the first minute after CE
and others. Optimal surgical access to the tumour is required: transcranial, transnasal, or combined. Most of macroadenomas are iso- or hypointensive signal on T1-weighted images, and mildly hyperintensive on T2-weighted images (Fig. 6.36). The tumour structure is usually heterogeneous. Cysts are frequently seen in its stroma, which are more hypointensive on T1-weighted images in comparison with the solid areas and are hyperintensive on T2-weighted imaging (Fig. 6.37). In rare cases, pituitary adenomas may be completely represented by cystic mass lesions (Fig. 6.38). MR signal of the cystic part may vary from markedly hypointensive to markedly hyperintensive on T1-weighted images, depending on the protein content in the cystic content (Fig. 6.39).
It should be noted that the differential diagnosis of different types of the pituitary tumours in relation to the produced hormone is impossible by MRI. In typical cases, MRI reveals a mass lesion originating from sella turcica, iso- or mildly hypointensive on Т1-weighted images, compressing the normal pituitary tissue, which has more intensive signal. In many cases, adenoma fills the sella turcica completely. In some cases, the normal pituitary tissue is so compressed that it may not be visualised at all. Nowadays MRI has become a crucial technique in the diagnosis of macroadenomas of the pituitary gland, due to its facility as a multiplanar examination, absence of bone artefacts, and imaging of arteries and veins of this region. Moreover, immediate neuroimaging of cavernous parts of the internal carotid arteries as well of the middle
Sellar and Parasellar Tumours
551
Fig. 6.36a–c Pituitary macroadenoma. Т1-weighted images (а,b) and Т2-weighted image (c) reveals a tumour within the cavity of enlarged
sella turcica with supralaterosellar growth. MR signal of the tumour is isointensive on T1-weighted images and mildly hyperintensive on T2 -weighted images
Fig. 6.37a–c Pituitary macroadenoma. Т1-weighted images (а,b) and Т2-weighted image (c) reveals a large tumour within the cavity of enlarged sella turcica, with supra-, latero-, and infrasellar growth. MR signal of the cystic part of the tumour is hypointensive on T1 -weighted images and hyperintensive on T2 -weighted image
Fig. 6.38a–c Pituitary macroadenoma. Т1-weighted images (а,b) and Т2-weighted image (c) reveals a large cystic tumour within the cavity of enlarged sella turcica, with suprasellar growth. MR signal of the cystic part of the tumour is hypointensive on T1-weighted images and hyperintensive on T2 -weighted image
552
Chapter 6 Fig. 6.39a,b Cystic pituitary macroadeno-
ma. Sagittal (with the patient lying supine) Т1-weighted image (а) and Т2-weighted image (b) reveals a hyperintensive MR signal of the content of the cystic cavity, due to high protein content in the cystic fluid. Sedimentation effect seen as a level of fluid well demonstrated in the cystic cavity
Fig. 6.40a,b Pituitary macroadenoma.
Sagittal T1-weighted image (а) and coronal T2-weighted image (b) reveals the intrasupralaterosellar pituitary tumour. The cyst in the tumour stroma is hypointensive on T1-weighted images and hyperintensive on T2 -weighted images. The effect of signal void of blood in arteries makes them well identified in relation to tumour tissue
and anterior cerebral arteries strictly delimits performance of presurgical direct angiography to identify location of these vessels (Figs. 6.40, 6.41). Upward growth into the suprasellar cistern is better seen on sagittal Т1-weighted imaging, due to high CE of adenomas and hyperintensive signal from CSF. A tumour with suprasellar growth has a typical figure-eight shape (Fig. 6.42). On frontal and axial T1-weighted images, the passage of optic nerves, and location of chiasm and optic tracts and their spatial relationship with a tumour are optimally seen (Fig. 6.43). A frequent phenomenon is laterosellar growth of adenomas into cavernous sinuses, but, in contrast to suprasellar growth, it is less clearly identified by MRI. The main reason for this is that the medial wall of the sinus is very thin and thus is not visualised in most cases. In many cases, coronal MRI scans show how a tumour grows above and beneath the cavernous part of the internal carotid artery, but it is not possible to identify simultaneously whether an adenoma invades the cavernous sinus or it just compresses it. On the other hand, the lateral wall of the cavernous sinus is a reliable landmark—it is relatively thick and is clearly identified on MRI. The growth of a tumour between the lateral wall of the cavernous sinus and
the internal carotid artery is the most reliable sign of cavernous sinus invasion. Asymmetrical enlargement of one of the cavernous sinuses as well as the high plasma level of prolactin should lead one to suspect sinus invasion. Prolactin levels greater than 1,000 ng/ml is a sign of the cavernous sinuses involvement in almost all cases (Ahmadi 1985). It is important to note that despite the fact that lateral invasion of cavernous sinuses is a frequent event, compression and occlusion of the cavernous segment of the internal carotid artery rarely occurs. This has diagnostic significance in the differential diagnosis between adenomas and meningiomas (Fig. 6.44). Direct cerebral angiography is adopted if a giant pituitary adenoma and mass lesions with intratumoural haemorrhages are present. The arch-shaped displacement of the anterior cerebral artery, rectification, and lateral displacement of the internal carotid artery siphon are the typical features of these tumours (Figs. 6.45, 6.46). The novel approach in diagnosis of invasion of the cavernous sinuses by adenomas is contrast MR venography with suppression of blood flow signal in arteries (Fig. 6.47). The infrasellar growth of a tumour is easily identified on sagittal and coronal T1-weighted images when the adenoma’s
Sellar and Parasellar Tumours
553
Fig. 6.41a–c Pituitary macroadenoma. Т2-weighted images (а,b) and Т1-weighted images (c) reveal a large tumour on the skull base, which
fills the sella turcica and both cavernous sinuses. The tumour partially grows in the retrosellar direction. The internal carotid artery siphons are included in the tumour structure, without their narrowing
Fig. 6.42a–d Intrasuprasellar pituitary tumour. On CT, the adenoma intensively accu-
mulates contrast medium (а). On a series of Т1-weighted images (b–d), a large tumour originating from the cavity of the sella turcica is seen. The tumour is homogenously isointensive. A concomitant hydrocephalus of the lateral ventricles is seen
554
Chapter 6
Fig. 6.43 Pituitary macroadenoma.
Coronal Т1-weighted imaging well defines intra-infralaterosuprasellar growth of the tumour. The optic chiasm is compressed and displaced upwards (arrow)
Fig. 6.44a–f Pituitary macroadenoma. Т2-weighted imaging (а) reveals a tumour within the cavity of enlarged sella turcica, with laterosellar rightward growth. 3D TOF (b,c) and 2D TOF MRI (d) after CE identify the lumen of cavernous sinus on the side of the tumour
growth, and there is no even dislocation or narrowing of the internal carotid artery. Direct angiography findings confirm the absence of compression of the internal carotid artery at the level of the cavernous sinus (е,f)
Sellar and Parasellar Tumours
555
Fig. 6.45a–c Pituitary macroadenoma. Т2-weighted imaging (а,b) shows a tumour within the cavity of enlarged sella turcica with suprasellar growth. Direct angiogram (c) visualises a typical bow-
shaped upward displacement of the A1 segment of the anterior cerebral artery, the vascular net of the tumour is absent, and there is no compression of the internal carotid artery siphon
Fig. 6.46a–f Pituitary macroadenoma. Т1-weighted imaging (а,b) demonstrates a large infrasuprasellar tumour with hemorrhagic foci. On direct angiograms in coronal (c,d) and lateral projections (е,f), a
typical bow-shaped upward displacement of the A1 segment of the anterior cerebral artery and rectification of the internal carotid artery siphon are seen. Mild vascular net of the tumour is seen (arrows)
556
Chapter 6
Fig. 6.47a–c Pituitary macroadenoma. Т2-weighted imaging (а) reveals a tumour within the cavity of enlarged sella turcica, with laterosellar leftward growth. On 3D TOF MRA (b,c) after CE and suppression of arteries, the tumour invasion of the left and partially the right cavernous sinus is seen
tissue is revealed in the sphenoidal sinus containing air. Tumour invasion into the depth of clivus is also well visualised on T1-weighted images if the disappearance of hyperintensive signal of bone marrow is found at this site. Large pituitary adenomas are often complicated by cystic degeneration and haemorrhages. Cystic degeneration of adenomas is demonstrated as regions of hypointensive signal on T1-weighted images and markedly hyperintensive signal on T2-weighted images. The signal of cystic fluid usually differs from that of the CSF in the suprasellar cistern. This is due to the high protein content in the cystic fluid, which shortens T1 relaxation time. Sometimes the sedimentation phenomenon may be observed in the cavity of a cyst, which is a specific sign of cystic degeneration (Fig. 6.48). One of the serious problems in the diagnosis of pituitary adenomas is the identification of whether the diaphragm of the sella turcica was ruptured by a tumour. Presurgical diagnosis of these exophytic tumours is of utmost importance to plan tactics of surgical approach—transnasally or transcranially. On CT, even after CE these areas of exophytic tumour are often missed. MRI without CE visualises them in almost all cases (Figs. 6.49, 6.50). However, it has not been yet explained how the remnants of diaphragm, dura mater, different tumour regions, and the adjacent dislocated structures may be correctly visualised or enhanced. Haemorrhage into macroadenomas is common. They are represented on MRI by a typical picture. Thus, subacute haemorrhage shows hyperintensive signal on Т1-weighted images and on T2-weighted images (Fig. 6.51). In some of these patients, clinical manifestations of the pituitary apoplexy may be the first sign of the disease (Ostrov et al. 1989; Bills 1993). As noted above, pituitary adenomas are rarely found in children. However, in contrast to adults the percentage of malignant tumours in children is high. Malignant tumours are
characterised by rapid growth, frequent haemorrhages, and extended invasion of the surrounding structures (Fig. 6.52). On CE CT and MRI, macroadenoma intensively and rapidly accumulates contrast medium. CE is markedly heterogeneous and helps to better visualise the internal structure of a tumour. After intravenous CE, the suprasellar component of a tumour and the optic chiasm are more easily identified, whereas the lateral expansion of a tumour may be missed due to simultaneous enhancement of the cavernous sinuses and a tumour’s tissue. Gadolinium-chelate injection is feasible in large pituitary tumours when it is necessary to differentiate the tumour and the adjacent brain structures (Figs. 6.53, 6.54). In conclusion, it should be mentioned that the diagnosis of pituitary tumours has to resolve the following issues: to determine the location of a tumour in relation to the sella turcica, to visualise different directions of growth, to estimate the size of a tumour (Figs. 6.55, 6.56), to identify rupture of the sella turcica diaphragm, to identify invasion of the cavernous sinuses and the extent of involvement of the internal carotid artery siphons into the tumour structure, to characterise the structure of a tumour (presence of cysts and haemorrhages), and to perform the differential diagnosis from other tumours and nontumour mass lesions of the sellar region. Treatment tactics and optimal choice of surgical accesses or their combinations depend on the resolution of questions mentioned above.
6.6
Craniopharyngioma
Craniopharyngiomas (CPH) account for 2.1–4.6% of all brain tumours, and they are more frequently found in children (17– 21%, and 7% of all cases of brain tumours in children), 4% of all supratentorial tumours, and up to 56% of all tumours of
Sellar and Parasellar Tumours
557 Fig. 6.48a,b Pituitary macroadenoma.
Cysts with hyperintensive signal on T1-weighted imaging (a) and T2 -weighted imaging (b) are seen within the solid part of the pituitary tumour. In each cyst, sedimentation effect is observed as a level of fluid. The patient lying supine
Fig. 6.49a,b Pituitary adenoma with
rupture of the sella turcica diaphragm. Coronal (а) and sagittal (b) Т1-weighted image shows the dumbbells-like shape of the tumour. There are a few exophytic tumours of adenoma through the rupture of diaphragm of the sella turcica upwards
Fig. 6.50a–c Pituitary adenoma with multiple ruptures of the sella turcica diaphragm. Coronal (a Т2-weighted images, b Т1-weighted image) and axial (c Т1-weighted image) MR images reveal a large
pituitary adenoma with parasellar growth, rupture of the sella turcica diaphragm, and enveloping of the right internal carotid artery segment by the tumour
558
Chapter 6
Fig. 6.51a–c Variants of haemorrhages into pituitary adenoma in different patients
Fig. 6.52a,b Pituitary adenoma in an
11-year-old child. Sagittal (a) and coronal T1-weighted imaging (b): a tumour fills the cavity of enlarged sella turcica and the left half of the sphenoidal sinus, and has a suprasellar growth with invasion of the left cavernous sinus. The optic chiasm is lifted and thinned. Along with the isointensive signal of the tumour a hyperintensive focus of haemorrhage is seen in the left half of it
Fig. 6.53a–c Pituitary adenoma (prolactinoma) in a 12-year-old child. Т1-weighted images without (а,b) and with CE (c). The tumour is revealed, which fills the cavity of the enlarged sella turcica, and grows upwards, lifting the anterior–inferior part of the third ven-
tricle, and infiltrates the cavernous sinuses. The signal of the most of tumour is isointensive to brain tissue; cystic components are hypointensive. After CE, the signal intensity markedly increased
Sellar and Parasellar Tumours
Fig. 6.54a–d Pituitary macroadenoma. MRI before (а–c) and after CE (d). A large, widely expanded pituitary tumour is revealed. The internal carotid artery siphons are included in the tumour’s stroma. The node on the upper pole of the tumour displaced the optic chiasm upwards
559
560
Chapter 6
Fig. 6.55a–i Variants of pituitary adenoma growth in different patients on MRI: а,b infrasellar, c laterosellar, d suprasellar, e laterosuprasellar
into the temporal area, f suprainfrasellar into the sphenoid bone, g laterosuprasellar into the temporal region, h,i suprainfra-antesellar
Sellar and Parasellar Tumours
561
Fig. 6.56a–c Giant pituitary adenoma. Т2-weighted images (а,b) and Т1-weighted images (c) show a large and extended tumour with su-
pratentorial growth and invasion of the maxillary sinus
the chiasmal–sellar region. The distribution of CPH according to age is characterised by two peaks: between 5 and 10 years, and (the smaller group) on the sixth decade of life (Carmel et al. 1982; Hoffman et al. 1992; Van Effenterre 2002). The origin of CPH is the cells of the embryonic epithelium located along the pharyngeal–pituitary passage,—from the bottom of the third ventricle up to the walls of pharynx. Kоnovalov (1985) distinguishes intrasuprasellar, “stalk” (infundibular), intraventricular, and giant (intra-extraventricular) types of CPH (Fig. 6.57).
Intrasuprasellar CPH first compress the pituitary tissue and the sella turcica as they originate from epithelial cells located within the adenohypophysis. Along with the tumour growth, the optic nerves, the internal carotid arteries, and their branches are displaced upwards and laterally; the third ventricle becomes fissure-like due to its upward lifting. Miscommunication between the pituitary tissue and its stalk occurs. Infundibular CPH originate from the epithelial cells located along the pituitary stalk in the space between the sella turcica diaphragm and the bottom of the third ventricle. These tu-
Fig. 6.57a–h Schemes of anatomic variants of craniopharyngiomas (coronal and sagittal planes). а,b intrasuprasellar; c,d infundibular CPH; е,f intraventricular; g,h intra-extraventricular
562
mours are usually located along the brain base—ante-, para-, and retrosellarly—and they lift up the bottom of the third as well as the previously discussed group of meningiomas do; however, the pituitary tissue remains intact. Infundibular CPH cause the most severe changes in the location of arteries of the brain base; infrequently, segments of the optic nerves are included into the tumour stroma. Intraventricular CPH that originate from the epithelial cells of the bottom of the third ventricle invade the ventral and the dorsal folia. The bulk of the tumour lies within the cavity of the third ventricle; the pituitary stalk and the pituitary tissue remain intact under these circumstances. Intraventricular CPH has been observed spreading into the lateral ventricles or along the brain base—intra- and extraventricular tumours. Giant CPH are a special group. CPH of all topographic types are related to this group. The typical features of CPH are their wider expansion, penetration into the ventricular system, and development of hydrocephalus, often obstructive. The blood supply of CPH proceeds via the posterior cerebral arteries and the internal carotid arteries. In some cases, arteries follow the tumour capsule and supply it with blood, in other cases, arteries that are located within the tumour stroma take part in the tumour and the adjacent structures blood supply, and in some instances arteries are situated on the surface of the CPH capsule but do not supply it with blood. CPH are a biologically heterogeneous group of tumours and are represented by two main histological variants, adamantinomatous and papillomatous types, which are not only pathologically, but also clinically different. The most frequent is the adamantinomatous variant of CPH. Typical features of this variant are polymorphism of pathological structure, invasive growth, glial capsule, and marked degenerative events. Calcifications in the solid part of adamantinomatous CPH (from small to coral shaped) are seen in more than in 90% of cases. The cystic components of the tumour have different content: opalescent or xanthochromic fluid in the thin-walled cysts, or brownish-green, fritterlike masses with thick walls with many calcifications in their depth. Papillomatous CPH have mainly a compact structure; rarely they are represented by small, uni-chambered cysts with thick walls. Their viscous consistency includes a good deal of cholesterol, detritus, and fats. The usual location of these CPH is intra-extraventricular; the type of growth is expansive with clear borders with even structures. Calcifications are seen much less frequently than with adamantinomatous CPH. Clinical manifestations of CPH depend mainly on the anatomic variant of the location of a tumour and involve the following: ophthalmological signs, hydrocephalus with raised intracranial pressure, the hypothalamus–pituitary–suprarenal axis, the cranial nerves, the cerebral hemispheres, and if a tumour invades the posterior cranial fossa, the brainstem. The extent of these symptoms and their sequence of their development depend on the anatomic variant of the tumour. The latter are not hormonally active tumours, but as they compress the pituitary or the hypothalamus, they cause symptoms such as growth retardation, hypothyroidism, and diabetes insipidus.
Chapter 6
Postsurgical relapses of CPH depend on the histological type of tumour. A high percentage of relapse is typical for adamantinomatous CPH after subtotal as well as after total removal with relatively short period of remission. A relatively long remission and rare relapses are typical in cases of papillomatous CPH. Over the last 15 years, we have performed over 250 surgical removals of CPH in children in the Paediatric Clinic of the Moscow Burdenko Neurosurgical Institute. Neuroimaging findings depend on the type and anatomic variant of a tumour. X-ray craniography reveals typical signs of CPH such as changes in shape, size of the sella turcica, and calcifications in the chiasmal–sellar region. Calcifications are found in 75–95% of cases. The shape and the size of calcifications vary, from small, crumb-like, and poorly distinguishable to large, lump-like, and vivid coral-like ones. Laminar calcifications are frequent, which are usually situated in the tumour capsule. Intrasuprasellar CPH cause changes in the sella turcica: increase in size, deepening of the bottom, widening of the entry, and deformity (thinning, lifting, shortening) of the anterior clinoid processes. Calcifications are usually found within the cavity of sella and above it. Intraventricular CPH do not usually cause severe changes of the sella turcica; its size remains almost intact. However, in the majority of cases the dorsum sellae turcica shortens. Being situated close to the CSF circulation pathways, CPH cause changes in the ventricular system and increase of intracranial pressure, which is observed on X-ray craniograms by way of “fingerprints” on the cranial vault bones, widening of cranial sutures, and changes in the sella turcica elements. Calcifications of CPH may be found in the third and in the lateral ventricles. The navicular shape of the sella turcica, which is sometimes combined with shortening of its dorsum, is typical for stalk CPH. Calcifications are usually located in the chiasmal and adjacent regions. Lifting the bottom of the third ventricle, these CPH cause hydrocephalus and rise of intracranial pressure, which can be seen on X-ray craniograms (Figs. 6.58–6.60). CT and MRI identify the precise size of a tumour, the ration between the cystic and the solid part of a tumour, and their sizes and location, and the condition of the ventricular system (the extent of concomitant hydrocephalus and in most cases, the level of occlusion of the CSF pathways) and spatial relation of the tumour to the third ventricle cavity; the extent of expansion beyond the ventricular system is seen. On coronal CT scans with or without reformation, the upward displacement of the third ventricle is detected clearly. In intrasuprasellar CPH, the size of the sella turcica is usually larged. The intrasellar part of a tumour is usually nodular with calcifications. Growing upwards, the tumour fills the region of chiasmal cisterns (partially or completely), with upward displacement of the bottom of the third ventricle. The suprasellar part of a tumour is usually cystic, but may be solid. Cysts may be located on the base of the anterior cranial fossa, in the paraventricular region (giant CPH), and be identified in the depth of the nodular part.
Sellar and Parasellar Tumours
563 Fig. 6.58 Intrasuprasellar craniopharingioma in a 4-year-
old child. “Fingerprints” are more vividly seen, the bottom of the anterior cranial fossa is depressed, the coronal suture is pulled aside and yawns, and the sella turcica has a deepened bottom, widened entry, and shortened dorsum. Calcification of irregular shape is located above the anterior clinoid process of the sella turcica
Fig. 6.59 Target X-ray craniogram of the sella turcica in a
13-year-old child with CPH. The sella turcica is deepened, the entry is mildly widened, the sella is thinned. A coralshaped calcification is seen in the sella turcica cavity
Fig. 6.60 X-ray craniogram of the sella turcica in a
12-year-old child with CPH: the bottom of sella is depressed, its dorsum is not visible, and many calcifications of various signal intensity are seen in the cavity of sella and in the suprasellar space
564
Chapter 6
On CT, a tumour is well delineated from the adjacent brain tissue. The density of certain components of CPH is different. The nodular part is almost isodensive to brain tissue, and CE increases its density on 8–10 HU only in a half of patients. Calcifications are found on CT in 95% of cases (in the tumour, stroma, capsule, or walls of cysts). Intraventricular CPH are predominantly cystic and are located in the third ventricle cavity, they penetrate into the lateral ventricles, and often reach giant sizes. The density of cystic areas of CPH is usually higher than that of brain tissue, but isodensive or mildly hyperdensive cysts may be found. After CE, the walls of cysts moderately accumulate contrast
medium. Intraventricular CPH in most cases cause hydrocephalus. Infundibular CPH has typical asymmetry, marked sizes, and expansion along the brain base with frequent invasion into the lateral ventricles cavity. If cysts are situated in the cavity of the third ventricle, then they usually completely fill its anterior portion. Sometimes cystic tumours are represented by a system of cysts, which are hardly differentiated and may be distinguished only on axial images (Figs. 6.61−6.65). It should be emphasised again that all the three anatomic variants of CPH may be giant. Many calcifications are typical for adamantinomatous CPH in the solid areas as well as in the
Fig. 6.61a–c CT in an 8-year-old child with CPH, a series of scans: a intrasellar calcifications, calcifications in the optic chiasm and in the wall of cyst that fills the third ventricle cavity; b small cysts are located in the chiasmal region, behind the dorsum sella, in the su-
prasellar space, which are hyperdensive; and c a small hypodensive cyst in the anterior superior pole of the tumour (note that the lateral ventricles are not dilated)
Fig. 6.62a–c CT in an 8-year-old child with an infundibular CPH. Cysts are hypodensive; many calcifications of different size are inside their
walls. The tumour produces a deformity of the anterior inferior part of the third ventricle
Sellar and Parasellar Tumours
Fig. 6.63a–i CT in a 9-year-old child with an infundibular CPH. a–c Tumour with heterogeneous density with calcifications is located in the chiasmal region, the retrosellar space, more leftwards, beneath the frontal lobes, and in the third ventricle. Т1-weighted images in coronal (d–f) and sagittal (g,h) planes: MR signals of the cystic parts of the tumour are heterogeneous from hypo- to hyperintensive; the
565
nodular part of the tumour is isointensive. The tumour produces deformity and displaces the brainstem, and invades the cavity of the third ventricle. The lateral ventricles are dilated, more leftwards. Т2-weighted image shows that the signal of all cysts is high, and calcifications appear as hypointensive foci (i)
566
Fig. 6.64a–c A cystic CPH in an 8-year-old child. Patient complained of headaches, growth retardation, diabetes insipidus, vision loss up to 0.5 on the right and 0.4 on the left, and bitemporal hemianopsia. CT shows the hypodensive tumour with peripheral calcifications in the cavity of the third ventricle (a). The lateral ventricles are asymmetrically dilated. Т2-weighted image (b), and Т1-weighted image (c): the
Chapter 6
tumour located in the cavity of the third ventricle and the chiasmal region is hyperintensive in both sequences. Calcifications are well identified with a background of the cystic contents, as hypointensive foci. Sagittal image reveals sedimentation phenomenon of the cystic content
Fig. 6.65a–c MRI of a 10-year-old child with an intra-extraventricular CPH in sagittal and axial planes before (а) and after CE (b,c). The tumour has mixed structure, and the small part of its solid component is located in the chiasmal region. Intensive CE is seen in the wall of cyst and in the solid part of the tumour
Sellar and Parasellar Tumours
567
Fig. 6.66a,b A 10-year-old patient with
intrasuprasellar CPH: growth retardation, hypogonadism, thirst, polyuria, and bitemporal hemianopsia are the signs and symptoms. Т1-weighted imaging in sagittal (a) and coronal (b) planes: a polycystic mass lesion is located in the sella turcica cavity and above the sella, the signal of the intrasellar cysts is hyperintensive, the signal of the upper third of the suprasellar cyst is isointensive and of the lower two thirds is hyperintensive, the optic chiasm is lifted upwards more to the right, the bottom of the third ventricle is compressed from beneath, and the lateral ventricles are not changed
Fig. 6.67a–c Intrasuprasellar CPH a 15-year-old patient. a CT shows
a round tumour in the chiasmal region with hypodensive structure and calcified walls. b,c Sagittal (Т1-weighted imaging) and axial (Т2-weighted imaging) planes: a cystic tumour in the chiasmal and
walls of cysts. In papillomatous CPH, calcifications are rarely found. On Т1-weighted imaging, the nodular part of the tumour is isointensive; the signal of cysts may be hypo- or hyperintensive (this depends on the protein content, cholesterol, and blood decay products within). On T2-weighted imaging, the signal of the nodular part is isointensive, and the signal of cysts may be hypointensive or markedly hyperintensive (Figs. 6.66−6.73). The extent of hydrocephalus depends on the spatial relation between the tumour and the ventricular system. Intravenous CE causes heterogeneous hyperintensity in the compact part of the tumour. CPH with many calcifications in the nodular part located in the sella turcica and in the suprasellar space (predominantly adamantinomatous) are well differentiated on 3D CT (Fig. 6.74). The spatial relationship between the tumour and the adjacent bone structures can be seen. The cystic CPH located only in the sella turcica cavity (hypointensive on T1-weighted images and hyperintensive on T2-
the suprasellar regions with hyperintensive in both sequences, calcifications in the walls of cyst appear as hypointensive signal on the cyst periphery are seen
weighted images) should be differentiated from the mucocele of the sphenoidal sinus, the signal of which may be similar to the CPH. Apart from differences in clinical manifestations and course, there are differences in their locations. Mucocele lies under the bottom of the sella turcica inside the sphenoidal sinus cavity, which appears enlarged and as if inflated, whereas the intact pituitary is located above the cystic mass lesion (Fig. 6.75). On cerebral angiography, the vascular net of a tumour is not usually detected; only displacement of vessels may be seen—the arteries of the circle of Willis, and the anterior and middle cerebral arteries, which depends on tumour location (Fig. 6.76). At present, direct angiography is almost never performed as a method of identificating the location of vessels in cases of CPH. The information presented by CT and MRA is sufficient for presurgical planning. In the early postsurgical period, remnants of tumour, blood clots in the tumour bed, the extent of brain atrophy, accumulations of air, blood, or CSF in the subdural space may be
568
Fig. 6.68a–f Infundibular CPH in an 8-year-old child. CT. a A hypodensive tumour with calcifications in the third ventricle and the left thalamus compresses the foramen of Monro from beneath; the lateral ventricles are mildly dilated and asymmetrical. Sagittal reformation: a hypodensive tumour in the chiasmal region and the third ventricle with a large calcification (b); coronal and sagittal
Chapter 6
T1-weighted images reveal a polycystic tumour, the signal of cysts is hypointensive to variable extent, and the posterior contour of a tumour displaces the cerebral peduncles (c,d). T2-weighted images (е,f). The signal of cysts is hyperintensive, and is hypointensive in calcifications
Fig. 6.69a–c Intrasuprasellar CPH in an 8-year-old patient. Sagittal and coronal T1-weighted images (a,b): the intrasellar solid part of the tumour is isointensive, and the signal of cysts varies from hypointensive to hyperintensive. Axial T2 -weighted image (c): hyperintensive signal of cysts in the chiasmal region
Sellar and Parasellar Tumours
569
Fig. 6.70a–c Intraventricular CPH in a 6-year-old child. Т1-weighted images (а,b) and Т2-weighted image (c): a cystic tumour located in the
cavity of the third ventricle is hyperintensive in both sequences. The foramen of Monro is compressed, and the lateral ventricles are dilated
Fig. 6.71a–c Intra-extraventricular CPH in a 5-year-old child. а,b Т1-weighted image: the tumour is located in the cavity of the third ventricle is and the chiasmal region, with homogeneously hypoin-
tensive signal. c Т2-weighted image: the signal of the tumour is homogenously hyperintensive, and the lateral ventricles are dilated and have asymmetrical shape
570
Fig. 6.72a–f Intrasuprasellar CPH in an 8-year-old child. Coronal CT (а–c): the solid part of the tumour is located in the cavity of the sella turcica and the chiasmal region, and there are calcifications within it. A hypodensive cyst with calcified walls is located in the suprasellar space, more in the left. The bottom of the third ventricle
Chapter 6
is compressed from beneath, and the lateral ventricles are deformed. MRI: T2-weighted image (d) and Т1-weighted images (е,f) show a nodular part of the tumour, which is isointensive to brain tissue; the signal of the cystic part is high, and calcifications in the walls of cyst are hypointensive
Sellar and Parasellar Tumours
Fig. 6.73a–f Intrasuprasellar CPH in a 7-year-old child. а,b Т1-weighted image: the tumour is isointensive to brain tissue, with even and clear-cut contours. c,d Т2-weighted images: the signal of the tumour is homogenously hyperintensive. e МRА: the prominent bow-shaped upward and posterior displacement of the initial segments of the anterior cerebral arteries. f MRS: marked decrease of NAA, Lip–Lac complex elevation peaks
571
572
Chapter 6
Fig. 6.74a–f Adamantinomatous CPH in an 8-year-old child. а,b CT reformation from axial tomograms in the sagittal and coronal planes: many calcifications form an irregular confluent conglomerate of intra- and suprasellar location; the cystic component are mildly hyperintensive and located along the contour of the calcified mass lesion. c–e 3D reconstruction reveals the relationship between the
calcified part of the CPH—resembling stalagmites—and adjacent bone structures. f Sagittal T1-weighted image: a tumour with many calcifications, with intrasuprasellar location and invasion of the third ventricle. The cystic parts of the upper and lower poles are isointensive with brain tissue; the cystic parts located near the posterior upper pole are hyperintensive
Fig. 6.75 Mucocele of the sphenoidal sinus in a 12-year-old child. Т2-weighted image of a hyperintensive cystic lesion located in the inflated sphenoidal sinus
Fig. 6.76 Rightward carotid angiography (coronal projection) in a
7-year-old child with CPH. The supraclinoid segment of the internal carotid artery is irregularly narrowed and laterally inclined. A typical bow-shaped upward displacement and narrowing of the A1 segment of the anterior cerebral artery is seen
Sellar and Parasellar Tumours
found on CT. In the late postsurgical period, CT may detect the absence or the presence of a tumour relapse and progression or reduction of hydrocephalus. Control MRI early in the first days after surgery does not usually reveal any additional changes compared with CT. Later after surgery, MRI reveals presence or absence of cysts (the signal of cysts may differ, to compare with preoperative findings) and the solid section of tumour, changes of the ventricular system, residual accumulation of the CSF, or blood in the subdural space.
6.7
Gliomas of the Optic Nerves, Chiasm, and Hypothalamus
These gliomas account for 3–5% of all intracranial tumours, and 25−30% of the chiasmal–sellar region tumours in children. In 20–50% of cases, these tumours are found in NF I (von Recklinghausen’s disease) (Menor 1991). Tumours of the optic chiasm frequently involve the hypothalamus and the third ventricle. Histologically, they are pilocytic astrocytomas in 75% of cases, but despite their benign nature, they are often unfavourable in terms of location and expansion. Tumours originating from the hypothalamus grow towards the chiasm, affect it, and expand into the third ventricle. On the other hand, tumours originating from the chiasm may expand not only along optic tracts, but also into the third ventricle. As it is difficult to identify the origin of these tumours' growth
573
according to neurological examination or neuroimaging, we discuss them together. Clinical findings are as follows: progressive visual loss, hypothalamic–pituitary dysfunction, and increase of intracranial pressure. According to clinical, neuroimaging, and surgical data five groups of tumours are distinguished: 1. Tumours of the anterior angle of the chiasm and one of the optic nerves, with predominant anterior growth 2. Antechiasmal gliomas invading into the cavity of the third ventricle; the origin of their growth is the lateral part of the chiasm 3. Tumours of the posterior parts of the chiasm, growing predominantly into the third ventricle 4. Tumours of the optic tract 5. Tumours of the third ventricle, growing into its lumen and causing occlusion of the CSF pathways (Fig. 6.77) Cases of optic nerve tumour with dilatation of the optic canal on the ipsilateral side occur. If both optic nerves are affected, then the dilatation occurs bilaterally (symmetrical or asymmetrical). If the chiasm is affected—changes of the sella turcica may be found in giant tumours—changes of the sella turcica and rise of intracranial pressure are the typical signs (Figs. 6.78–6.80).
Fig. 6.77a–e Schematic representation of different forms of tumours of the optic tract and the hypothalamus—the origin and predominant location of tumours: a type 1, b type 2, c type 3, d type 4, and e type 5
Fig. 6.78a,b X-ray craniography. а A 5-year-old child with right optic nerve glioma: mild enlargement of the right optic canal and the left optic canal is intact. b A 6-year-old child with glioma of optic nerves: asymmetrical enlargement of optic canals (D > S) (arrows)
574
Chapter 6
Fig. 6.79a,b Glioma of the optic chiasm
in a 4.5-year-old child. а Lateral X-ray craniogram, b enlarged X-ray craniogram of the sella turcica: the skull is enlarged and hydrocephalic in shape, fingerprints are vivid on the cranial vault bones, margins of the coronal suture are pulled apart, and the sella turcica is pear shaped due to excavation of the chiasmal sulcus region
Fig. 6.80a,b Glioma of the optic chiasm and optic nerves in an 8-year-old child. а X-ray craniogram of the sella turcica: the sella turcica is enlarged and W shaped, its bottom is depressed, the entry is
widened, the dorsum of sella is rectified, and there is osteoporosis of the anterior clinoid processes. b X-ray craniogram of orbit: marked dilatation of optic canal bilaterally (S > D)
The involvement of the orbital portion (on CT) leads to thickening of the optic nerve of variable shape and size. The most frequent variants are fusiform, cylindrical, or oval enlargements of the optic nerve. A tumour of the optic nerve expanding into its canal part and then intracranially causes dilatation of the optic canal and is clearly identified on CT. The density of optic nerve gliomas on CT is within the range of 25–60 НU. After CE, their density mildly increases (5–8 HU). CE is necessary in cases in which tumour expansion into the intracranial part of the optic nerve is suspected. In these cases, the solid part of the tumour originating from the orbit is seen, with involvement of the chiasmal cistern. If the chiasm, optic nerves, and the hypothalamus are affected, then an iso- or hypodensive mass lesion that mildly accumulates contrast medium is seen. In cases with widely expanded tumours, CE is observed along the optic tracts up to the lateral geniculate bodies and often within the third ventricle. Several observations were made in our institution when the tumour reached the optic cortex. Obstruction of the CSF pathways caused hydrocephalus of various extents (Figs. 6.81–6.85). In several cases, calcifications could be seen within the stroma of hypothalamic gliomas, which is what makes them resemble CPH.
On MRI, the tumour signal is isointensive or hypointensive on T1-weighted images and moderately hyperintensive on T2-weighted images compared with that of brain tissue. Cysts often form within tumours or nearby, which is more typical for giant gliomas. The density of cystic components on CT and their signal intensity on MRI is equal to that of the CSF. Expansion of tumours along the optic tracts is well seen with T2-weighted imaging, whereas CT sometimes fails clearly to identify these changes. Intravenous CE reveals the accumulation of contrast medium in the tumour stroma, which may be mild or homogenously intensive (Figs. 6.86–6.91). Moreover, when MR fat saturation and paramagnetic contrast media are used, the intraorbital and intracanalicular portion of the affected optic nerve are well demonstrated. Angiography is helpful in those case in which there are giant and rapidly growing tumours with signs of malignant transformation. Displacement of cerebral vessels and enhancement of the abnormal vascular tumour net are seen on angiography in these cases. Giant tumours of the optic chiasm in children should be differentiated from CPH, arachnoid cyst, epidermoid/dermoid teratoma, chordoma, carcinoma, giant aneurysm, vascular malformations, inflammatory disorders (abscess, granuloma), and pituitary tumour. CT and MRI are the most informative
Sellar and Parasellar Tumours
575
Fig. 6.81a–e Fibrillary astrocytoma of the left optic nerve in a 4-year-old child. а CT: leftward exophthalmos, the left orbit is enlarged, and mace-shaped enlargement of the left optic nerve. Axial and sagittal T1-weighted images (b–d). T2-weighted images: on axial scans the optic nerve is thickened and deformed is mace shaped (e) Fig. 6.82 Glioma of the optic chiasm and the left optic nerve in a 3-year-old child. CT:
leftward exophthalmos—the left optic nerve is markedly enlarged due to the tumour growing towards the chiasm. The tumour density is identical to the brain tissue. The left optic canal is prominently dilated
Fig. 6.83a,b Glioma of the optic chiasm
and the left optic nerve in a 4-year-old child. CT with CE (а,b): the left optic nerve is hyperdensive, thickened and coiled; a tumour is seen in the chiasmal region with even and polycyclic contours, and a small CSF cyst is seen in the left mediobasal temporal region
576
Chapter 6
Fig. 6.84a–c Glioma of the optic chiasm, the optic nerves, and the optic tracts. CТ with CE (а–c): a hyperdensive tumour fills completely the
region of the optic chiasm, affects the left and partially the right optic nerves, and grows along the optic tracts
Fig. 6.85a–f Astrocytoma of the optic chiasm in a 4-year-old boy.
а CT without CE: a mildly hypodensive tumour in of the optic chiasm is seen, partially located behind the sella turcica dorsum; the region of chiasmal sulcus is deformed. b CТ with CE: the density of tumour increased markedly, its contours became clear, and the up-
per pole is visualised at the level of the third ventricle. c–e Axial and sagittal MRI: the signal of the tumour is heterogeneously hypointensive on T1-weighted imaging. It fills most of the third ventricle, and deforms the brainstem and displaces it backwards. f On T2-weighted images, the tumour has hyperintensive signal
Sellar and Parasellar Tumours
577
Fig. 6.86a–c Anaplastic pilocytic astrocytoma of the optic chiasm and the left optic nerve in a 3-year-old child. The child presented with headaches, leftward exophthalmos, visual loss up to 0 left and up to 0.01 right, primary optic nerve atrophy, and diabetes insipidus. A series of Т2-weighted images in axial (а) and coronal (b) planes and
T1-weighted image (c): the tumour is hyperintensive on Т2-weighted imaging, and is homogenously hypointensive on T1-weighted imaging; the orbital part of the tumour is clearly differentiated; the large part of the tumour fills the third ventricle, and the lateral ventricles are enlarged
Fig. 6.87a–c Pilocytic astrocytoma of the optic chiasm and the right optic nerve in a 10-year-old child. а On CТ, the tumour looks like a homogenously hypodensive mass in the chiasmal region and the anterior cranial fossa; its contours are uneven, partially calcified. A series of MR images: the tumour is hyperintensive on Т2-weighted
imaging (b), and hypointensive on T1-weighted imaging (c). It affects the right optic nerve, filling the region of enlarged sella turcica– chiasmal region, the platform of the sphenoid bone, and the adjacent areas of the frontal and temporal lobes
578
Chapter 6
Fig. 6.88a–c A giant cystic chiasmal tumour in a 3-year-old child. T1-weighted images (а,b): the solid part of the tumour is heterogeneously hypointensive, and the cystic part is hypointensive. Т2-weighted image (c): the solid part of the tumour is heterogeneously and predominantly hyperintensive, and the cystic part is hyperintensive Fig. 6.89a,b Glioma of the optic chiasm
in a 5-year-old child. а Т1-weighted image: a tumour of the chiasmal–sellar region is mildly hypointensive. b T2-weighted image: the tumour has a hyperintensive MR signal
Fig. 6.90a–c Anaplastic astrocytoma of the hypothalamus and the
optic chiasm in a 12-year-old child. Т2-weighted image (а): the signal of a tumour is heterogeneous along the optic tracts. MRI after CE
T1-weighted images (b,c): intensive accumulation of contrast medium by the tumour in the chiasmal region and mild accumulation of contrast medium along the optic tracts is observed
Sellar and Parasellar Tumours
579
Fig. 6.91a–c Malignant glioma of the third ventricle in a 12-year-old child. а Т2-weighted image: the tumour is heterogeneously hyperintensive and fills the cavity of the third ventricle. b Т1-weighted im-
age: the tumour is heterogeneously hypointensive. c MRI with CE: intensive accumulation of contrast medium in the tumour tissue; the ostium of the aqueduct of Sylvius is filled with tumour
in the differential diagnosis of all tumours of this location. If vascular lesions are suspected, then cerebral angiography is the obligatory method.
Germinomas are tumours of children and young adults (5–30 years). They are manifested by endocrinological dysfunction such as diabetes insipidus or panhypopituitarism. Such manifestation confirms that the tumour involves the walls of the lateral ventricles. Defects of visual fields and optic nerve atrophy are usual. If the CSF pathways are blocked, then hydrocephalus occurs. Oculomotor signs may develop if a tumour grows into the parasellar space. On CT without CE, germinomas are hyperdensive, which is homogenously enhanced after intravenous injection of contrast medium (Figs. 6.92, 6.93). Calcifications are not usual for tumour here. Primary germinoma of the pineal region may be identified. Most of suprasellar germinomas are clearly detected on MRI, as their sizes are usually large by the time clinical manifestations occur. They are typically located along the median axis in the bottom of the third ventricle. In contrast to CPH, the structure of germinomas is homogenous, and only in rare
6.8
Germinomas
Germinoma is one of the most frequent tumours of the pineal region, and only in 20% of cases are they found in the suprasellar cistern and much less frequently, in the pituitary fossa. Suprasellar germinomas may be primary and originate from the suprasellar cistern, or they may be metastases from the pineal region germinomas (Takeuchi 1978). Germinomas consist of large polygonal embryonic cells, accumulations of lymphocytes, and thick connective tissue stroma. The suprasellar germinomas are nonencapsulated tumours with infiltrative growth; they may embed metastases into the walls of the lateral ventricles and the basal cisterns.
Fig. 6.92a,b Germinoma in a 15-year-old
patient. CТ with CE in the axial plane (а) (a series of slices). b Coronal scan: there is a hyperdensive mass lesion in the chiasmal region
580
Chapter 6
Fig. 6.93a–f Metastases of germinoma of the pineal region into the chiasmal region, the bottom of the third ventricle, and subependymally. CT with CE before treatment (а–c) and after radiation (d–f)
cases are small cysts revealed in tumour stroma. The signal of germinomas moderately differs from that of brain tissue. Germinomas are iso- or mildly hypointensive on T1-weighted images and are iso- or hyperintensive on T2-weighted images. Usually, germinomas intensively accumulate contrast medium, and metastases may be revealed in the subarachnoid space (Figs. 6.94, 6.95). In conclusion, if a primary tumour of the pineal region is present, then a certain structure of tumours is observed, which is better visualised on MRI.
6.9
Teratoma, Epidermoid Tumours, and Dermoid Tumours
These tumours of the sellar region are mainly seen in young children, predominantly in boys. Teratomas are mass lesions covered by a connective tissue capsule that contains ectodermal elements (layers of exfoliated epithelium, sebaceous and sweat glands, hair, crystals of cholesterol, amorphous fat), as well as elements of neural, muscle, and bone tissue. Epidermoid tumours (dermoid tumours) are the result of division
of ectoderm during the neural tube closure. Epidermoid and dermoid tumours are benign and slowly growing tumours, which may have intracranial and intraspinal locations. Epidermoid tumours make up approximately 0.2–1.5% of all primary intracranial tumours; dermoid tumours are found five times less frequently (0.04–0.06%). Epidermoid tumours are tumours of adults, usually diagnosed in patients aged 20–60 years, and they are mainly located in basal cisterns and laterally. The walls of these cysts are lined with simple, multilayer, flat epithelium, which covers the external layer of connective tissue. The internal part of the cyst is formed from a wax-like material of exfoliated keratin derivates of its wall and of solid cholesterol crystals. In contrast to dermoid tumours, epidermoid tumours do not contain hair follicles and sebaceous glands. It is suggested that the epidermoid tumour is not a tumour, but a benign cyst. Dermoid tumours are most frequently diagnosed within the age range of 30–50. They are usually located along the medial axis, frequently in the parasellar region, and less frequently in the posterior cranial fossa (Wilms et al. 1991). A dermoid tumour is a lesion in the walls, which
Sellar and Parasellar Tumours
581 Fig. 6.94a,b Germinoma of the sellar
region. Sagittal (а) and coronal (b) Т1weighted images visualise a tumour with intrasuprasellar growth
Fig. 6.95a–c Germinoma of the sellar region. MRI in T2-weighted imaging (a) and T1-weighted imaging (b,c) modes reveal the tumour,
which has similar signal intensity to brain tissue
may include the dermal germ cells such as hair follicles, and sweat and sebaceous glands. Slow, expansive growth is typical for these tumours. Besides visual symptoms, headaches, (less frequently) hypopituitarism, cranial neuropathies, and diabetes insipidus are typical for suprasellar tumours. On X-ray craniograms, many calcifications and/or dentlike bony elements may be revealed in teratomas and dermoid tumours, with an enlarged sella turcica (Fig. 6.96). On CT, these tumours are characterised by heterogeneous density with many calcifications, bony elements, and hypodensive fatty inclusions. Dermoid tumours on CT are typically round, well delineated from brain tissue, and have heterogeneous density (–20 to –60 НU). Calcification of the capsule is frequent. In cases in which the capsule of a dermoid tumour is ruptured, small hypodensive areas, which represent fat globules, may be seen in the ventricular system and the subarachnoid space. Hyperdensive dermoid tumours are rare. Dermoid tumours are typically characterised by increased signal intensity of fat on T1-weighted imaging (Fig. 6.97). On T2-weighted imaging,
a tumour has variable signal, hypo- or heterogeneously hyperintensive (Wilms et al. 1991; Smith et al. 1991). If hair is present in a tumour, then thread-like areas of hypointensive signal are seen on MRI (Markus 1993). When a tumour ruptures, hyperintensive signal of fat-containing lumps is seen in the subarachnoid space and the ventricles. Intravenous CE mildly increases tumour intensity. On MRI, teratoma has a heterogeneous structure due to bone elements, fat, and soft-tissue components (Fig. 6.98), whose signal intensity may increase after CE. Epidermoid tumours have variably density on CT from –30 HU to that close to the CSF. In 10–25% of them, calcifications are seen within (Tatler 1991). Sometimes epidermoid tumours may be hyperdensive on CT due to high protein content or deposition of iron-containing pigment (Gualdi et al. 1991). In most cases, epidermoid tumours do not enhance on CT, but exceptions exist. On MRI, these cysts are well identified due to prolonged T1 and T2 relaxation times. The signals are similar to the CSF in the subarachnoid space (Figs. 6.99, 6.100). There are also cysts that are hyperintensive to CSF on T1-weighted
582
Chapter 6
Fig. 6.96a,b Teratoma in a 5-year-old child. X-ray craniograms in coronal (а) and lateral projections (b): the sella turcica is enlarged, its bot-
tom is depressed, and its entry is widened. Many bone density inclusions resembling teeth are in the cavity of sella and above it
Fig. 6.97a–c Dermoid cyst of the suprasellar region. Т1-weighted image (а) and Т2-weighted image (b) reveal a mass lesion in a patient lying supine. The tumour has heterogeneous structure: its posterior portions are represented by a cyst, and the anterior portions contain
fat-like globules forming a level of fluid in the cyst. MRA ascertains the relationship between the tumour and cerebral arteries of the skull base (c)
Sellar and Parasellar Tumours
583
Fig. 6.98a–e Teratoma in a 5-year-old child. CT (а,b) accumulation of many calcifications in the cavity of the sella turcica and above it. c–e Т1- and Т2-weighted imaging: the tumour is moderately hyper intensive on Т2-weighted images and is hypointensive on T1-weighted images, with hypointensive foci along the posterior contour (fragments of bone). Т1-weighted imaging shows a small hyperintensive lesion (fat inclusion) in the depth of the tumour
Fig. 6.99a–c Epidermoid cyst of suprasellar region. MRI: Т1-weighted images (a,b) and Т2-weighted image (c) shows an encapsulated mass lesion in the suprasellar region, with relatively heterogeneous signal inside, hyperintensive on Т2 -weighted images, and hypointensive on T1-weighted images. The pituitary gland is compressed in the sella turcica cavity
584
Chapter 6
Fig. 6.100a–d Epidermoid cyst of the chiasmal–sellar region. Т1-weighted images (а–c)
and Т2-weighted image (d). A large and widely extended mass lesion is seen hyperintensive on Т2-weighted images, and hypointensive on T1-weighted images, with a festoon-shaped contour. The volume of the tumour is better assessed with Т2-weighted imaging
Fig. 6.101a–c Epidermoid cyst of the chiasmal–sellar region.
Т-weighted images (а) and Т1-weighted image (b). A large and widely extended mass lesion is seen hyperintensive on Т2-weighted images, and hypointensive on T1-weighted images, with a festoon-
shaped contour. The volume of the tumour is better assessed with Т2-weighted imaging. Tumour is characterised by a markedly high MR signal on DWI (c)
Sellar and Parasellar Tumours
imaging. This is due to high fat content in the cyst (Horowitz 1990). Hyperintensive signal on DWI is typical of chiasmal– sellar region epidermoid tumours (Fig. 6.101).
6.10 Chordoma Chordomas of the sellar region are rare intracranial tumours, originating from the remnants of primary notochord and accounting for less than 1% of all intracranial tumours. Chordomas are rare in children. About 35–40% of chordomas are found intracranially (the peak of incidence is between 20 and 40 years), 50% of chordomas are located in sacrum (the peak of incidence is between 40 and 60 years, frequently in males), and 15% of cases are in the vertebral column. Among intracranial chordomas, the most frequent site is the clivus (near the spheno-occipital synchondrosis); much less frequently, chordomas are encountered in the sellar region or laterally to the pyramid of temporal bone. These tumours are soft, lobular, grey mass lesions with locally invading growth and destruction on macroscopy. They consist of large cells with intracytoplasmic vacuoles and thick strands of fibrous connective tissue, which give the mass lesion its lobular structure. Chordomas of the chiasmal–sellar region are manifested by visual symptoms and pituitary deficiency. When invading the cavernous sinuses, oculomotor signs and signs of trigeminal nerve involvement occur. Complete removal of chordoma is possible in rare cases, which is why partial resection with consequent radiation is performed. Radiation with proton beams or linear accelerator therapy is suggested, as chordomas are resistant to radiation done with standard protocols. CT and MRI are complimentary in neuroimaging of these tumours. CT reveals a soft tissue mass lesion with bone destruction and ossification (approximately 50% of cases). On MRI, chordomas are characterised by the variability of signal intensity on T1-weighted images (Figs. 6.102, 6.103) (Sze et al. 1988). Expansion of the tumour into the bone mar-
585
row of the clivus leads to replacement of normal signal of the bone marrow fat by the hyperintensive signal of tumour (Fig. 6.104). On T2-weighted images, moderate or marked hyperintensive signal may be seen. Septi of fibrous connective tissue appear as hypointensive stripes on T2-weighted images, which separate hyperintensive lobular areas of a tumour (Fig. 6.105). MRI exceeds CT in identification of a tumour expansion and its spatial relationship with brain structures, craniobasal nerves, and vessels. However, destruction of skull base bones and ossifications in the depth of the tumour are better seen on CT (Figs. 6.106–6.108). CE on MRI improves neuroimaging of tumour expansion, but may be rather mild (Figs. 6.109, 6.110).
6.11 Hamartomas of the Tuber Cinereum Hamartoma of the tuber cinereum is a rare congenital mass lesion more frequently seen in boys, is well delimited from the adjacent tissues, and is located in the suprasellar region or the interpeduncular cistern, adjoining the mamillary bodies or tuber cinereum by a thin stalk. Hamartoma is not a proper tumour but a congenital, nontumour heterotopia. On histology, a hamartoma consists of accumulations of small and large cells, astrocytes, and oligodendrocytes, which are in correct ratio with tuber cinereum tissue (Matsko 1998). The most frequent and early clinical manifestation occurs approximately at the age of 2 years: isosexual precocious puberty. Other signs such as epileptic seizures and behavioural changes occur later when a hamartoma acquires a diameter of about 10 mm. Neuroimaging in hamartomas is possible only by CT or MRI. On CT, hamartoma is a mass lesion isodensive to brain tissue and located in the chiasmal–sellar region or in the interpeduncular cistern, clearly delineated by CSF. Intravenous CE does not change its density. On Т1- and T2-weighted imaging, a lesion looks like an isointensive mass in the tuber cinereum or the mamillary bodies regions, clearly revealed in all the three scanning planes. After intravenous CE the signal
Fig. 6.102a,b Chordoma of the skull base. Sagittal (a) and coronal (b) T1-weighted images show a heterogeneously hyperintensive tumour filling the sphenoidal sinus, cavities of the ethmoid labyrinth, and extending into the chiasmal and parasellar region
586
Chapter 6
Fig. 6.103a–c Chordoma of clivus of the skull base and the chiasmal region. Т1-weighted images (а–c) reveal a large and widely extended
skull base tumour with heterogeneous MR signal. The tumour destroys the clivus and grows into nasopharynx
Fig. 6.104 Chordoma of the skull base. Т1 (а,b) and Т2-weighted images (c). The tumour destroys the sphenoid bone, filling the sphenoidal sinus and the ethmoid labyrinth. Small intracranial component of the tumour present compresses the brainstem
Sellar and Parasellar Tumours
Fig. 6.105a–f Chordoma of the skull base. Т2-weighted images (а–c,f) and Т1-weighted images (d,e). The
tumour destroys the sphenoid bone, filling the sphenoidal sinus and the ethmoid labyrinth. Small intracranial component of the tumour is present that compresses brainstem. T2-weighted imaging visualises the connective tissue septi in the tumour as well as T1-weighted imaging does
587
588
Fig. 6.106a–f Chordoma of the skull base. Т2-weighted images (а–c) and Т1-weighted images (d–f). A tumour with
heterogeneous structure is seen. Its soft tissue component is hyperintensive on Т2-weighted images, and is hypointensive on T1-weighted images. Calcifications in the tumour stroma are dark in all sequences
Chapter 6
Sellar and Parasellar Tumours
589
Fig. 6.107a–e Chordoma of the skull
base and clivus. Axial (а) and coronal CT (b). A large tumour with calcifications massively destroys bones of the skull base. Т1-weighted images (c,d) and Т2-weighted image (e) better identify the tumour expansion
590
Chapter 6
Fig. 6.108a–d Chordoma of the skull base with malignant transformation. a CT with CE. A large tumour with many calcifications dislocates the adjacent brain structures. Т2weighted image (b) and Т1-weighted images (c,d). A tumour with heterogeneous structure is seen. Its soft tissue component is hyperintensive on Т2-weighted imaging, and is hypointensive on T1-weighted imaging. Calcifications in the tumour stroma are dark in all sequences
Fig. 6.109a–c Chordoma of the clivus. CT: a small tumour of the sella turcica dorsum and of the upper third of the clivus is seen, with calcifications (а). MRI: Т2-weighted image (b) and Т1-weighted image with CE (c). A tumour with heterogeneous structure and enhancement is observed
Sellar and Parasellar Tumours
Fig. 6.110a–c Chordoma of the chiasmal–sellar region in a 10-year-
old child. CT without CE (а) reveals a large tumour with many calcifications. Т1-weighted images with CE (b,c) visualise a tumour with
591
heterogeneous structure. Its soft tissue component is characterised by accumulation of contrast medium. Calcifications in the tumour are dark
remains unchanged, which is a differential marker that allows distinguishing hamartoma from, for instance, pilocytic astrocytoma (Figs. 6.111, 6.112). It is typical for hamartomas that their sizes and invasiveness do not increase on follow-up examination for a long period. In patients with hamartomas of the hypothalamus, other cerebral malformations may be revealed: agenesia/hypogenesia of the corpus callosum or cortical disgenesia. Sometimes a tumour may reach such a large size that it causes deformity of the adjacent structures (Fig. 6.113). The differential diagnosis should be made from glioma of the bottom of the third ventricle.
6.12 Langerhans Cell Histiocytosis
Fig. 6.111a–c Hamartoma of the hypothalamus in a 7-year-old girl.
larged). Sagittal (а), axial (b), and coronal (c) T1-weighted images: a small round lesion of the hypothalamus is seen isointensive with brain tissue
Premature sexual development (menses since the age of 2, hair in subaxillary fossae, pubic hair is present, and breast glands are en-
Langerhans cell histiocytosis is a group of disorders characterised by proliferation of histiocytes (macrophages). Solitary or multiple lesions are encountered. In cases of a single mass lesion, involvement of cranial vault bones is typical, and in these cases, the hypothalamic–pituitary system is usually not involved. Multifocal granulomatosis is a more aggressive disorder, occurring in childhood. In 25% of cases, the classical triad of clinical manifestations is seen: diabetes insipidus, exophthalmos, and foci of lysis of cranial bones (Hand-Schull-
592
Chapter 6
Fig. 6.112a,b Giant hamartoma of the hypothalamus in an 8-year-old boy. Premature sexual development, partial epileptic seizures, forced laughter, aggressiveness, and visual loss up to 0.7 were the manifestations of the tumour presence. Т2-weighted imaging (а) and Т1-weighted imaging (b) in axial and sagittal planes: a tumour of the hypothalamus is seen isointensive with brain tissue, which goes down behind the dorsum sellae and deforms the brainstem
Fig. 6.113a–c Giant hamartoma of the hypothalamus. Т2-weighted image (а) and Т1-weighted images (b,c) after CE. A tumour isointensive
to cerebral grey matter with clear-cut contours is seen in the chiasmal–sellar region, with infratentorial growth behind the dorsum sellae with deformation of brainstem. CE in tumour tissue is absent
er-Christian syndrome). In these cases, granulomas may be observed in the hypothalamus or in the pituitary stalk. CNS involvement is usually found if histiocytosis started in other organs and systems. Skull base and cranial vault bones, the posterior fossa structures such as brainstem, and the cerebellar hemispheres are usually affected; the chiasmal–sellar region is much less frequently involved. Granulomatosis in the CNS starts with involvement of the subarachnoid space with subsequent invasion of the hypothalamus and pituitary. CT demonstrates thickening and increase of contrast accumulation of the pituitary stalk. On MRI, hyperintensive signal in the hypothalamus on T2-weighted images may be seen and more frequently, thickening of the pituitary stalk is observed (Tien et al. 1990; Maghnia et al. 1992). These changes are better identified in sagittal and coronal planes (Fig. 6.114) than
on CT; however, CT with CE in the coronal plane may also be helpful. Diagnosis is made after biopsy of one of the abnormal areas of bone.
6.13 Ratke’s Cleft Cysts Ratke’s cleft cysts (RCC) are well-delineated structures that vary in size from several millimetres to 1–2 cm. They are found in less than 1% of primary brain tumours. In most cases RCC are small, asymptomatic mass lesions located in the intrasellar or the intrasuprasellar space (Voelker et al. 1991). RCC may be seen in any age; however, they are more frequent in adults. The wall of the cyst consists of cylindrical, cubic, or flat epithelium, located on the basal membrane. Epithelium is
Sellar and Parasellar Tumours
593
Fig. 6.114a–e Histiocytosis in a 9-year-
old child. Т2-weighted image (а) and Т1-weighted image (b): isointensive tumour of the chiasmal–sellar region. c–e MRI with CE: prominent accumulation of contrast medium is seen in pathological area
often ciliary and may contain bowl-shaped cells. The content of a cyst is usually mucous and less frequently, it is filled with exudate or remnants of exfoliated cells. Calcifications of the cyst walls are rarely observed. Clinical manifestations appear in those cases when a large cyst compresses the pituitary or the optic chiasm. These are headaches, visual loss, and various endocrine dysfunctions, including hypopituitarism and diabetes insipidus (Kim et al. 2004). On CT, round or lobular intra- or suprasellar hypodensive mass lesions that do not accumulate contrast medium are seen. On MRI, a round or oval mass lesion is usually seen, which is located between the anterior and the posterior lobes of the pituitary or in front of the pituitary. The signal of such a mass
lesion is homogenous, iso-, or hyperintensive on T1-weighted images and iso- or hypointensive on T2-weighted images compared with CSF, which allows making the differential diagnosis from CPH. In cases of intracystic haemorrhages or inflammatory processes, the signal becomes heterogeneous. Cysts with mucous fluid are not distinguishable from cystic CPH on MRI—both lesions may be hyperintensive on Т1- and T2-weighted images (Fig. 6.115) (Ross et al. 1992). The cyst with exudate has identical MR signal characteristics with that of the CSF. The cysts containing exfoliated areas are the most difficult entities in terms of the differential diagnosis, as they are difficult to distinguish from solid tumours. However, in contrast to solid tumours, these cysts do not enhance contrast medium.
594
Chapter 6 Fig. 6.115a–d Ratke’s cleft cyst in a 15-year-old boy. Visual loss up to 0.5 bilaterally, and bitemporal hemianopsia were the manifestations. Т2-weighted imaging (а) and Т1-weighted imaging in sagittal (b,c) and coronal (d) planes. A round mass lesion with a clear capsule hyperintensive in both sequences is seen in the sella turcica cavity. The upper margin of a mass lesion is evaginated and the optic chiasm is compressed from beneath. The cyst compresses the pituitary
6.14 Meningioma Meningioma is the second-frequent suprasellar tumour in adults. Meningiomas of the sellar and the parasellar regions usually originate from dura mater of the sphenoid bone crest, the diaphragm of the sella turcica, the anterior clinoid processes, tuberculum sellae, and the walls of the cavernous sinus. The most frequent complaint of patients with meningiomas of the sellar and the parasellar regions is progressive visual loss due to compression of optic nerves, optic chiasm, and optic tracts. Visual loss may be combined with oculomotor nerve deficit. CT reveals hyperostosis of the tuberculum sellae, of the sphenoid bone crest, erosion of the dorsum sellae turcica, and hypertrophy of the sphenoidal sinus or other bone abnormalities. Meningioma on standard CT looks like a hyperdensive mass lesion. However, calcifications of various size and shape are often found. CE is marked and relatively homogenous (Fig. 6.116). On T1-weighted imaging meningiomas are iso- or mildly hypointensive. On T2-weighted imaging a tumour may have variable MR signal intensity: iso- or moderately hyperintensive to brain tissue (Figs. 6.117, 6.118). A common sign of meningiomas of the cavernous sinuses is uneven narrowing of the siphon of the internal carotid ar-
tery, which is often enshrouded by a tumour. It is a rare sign in other tumours, for instance, in pituitary adenomas with parasellar growth (Fig. 6.119). Meningiomas demonstrate marked CE and become hyperintensive on T1-weighted imaging. After CE, the wide base of the tumour becomes more clearly defined at the site of attachment (Figs. 6.120, 6.121).The perfusion parameters differ with pituitary adenomas.
6.15 Neurinoma of the Fifth Cranial Nerve Schwannomas (neurinomas and neurilemmomas) account for approximately one third of primary tumours of the trigeminal nerve and tumours of Meckel’s cavity (Yuh et al. 1988). Specifically, they make up less than 0.4% of all primary brain tumours. Neurinomas of the third, fourth, and sixth cranial nerves are less frequently observed. More frequently, neurinomas affecting the central part of the skull base and the cavernous sinus are tumours of the trigeminal nerve. As these tumours may originate from any part of the nerve between the root and the terminal extracranial branches, their clinical manifestations and neuroimaging findings differ depending on the direction and the growth of a tumour. The most frequent clinical manifestation is sensory loss within the innervation area of the affected cranial nerve.
Sellar and Parasellar Tumours
595
Fig. 6.116a–c Meningioma of the tuberculum of the sella turcica. Axial (а) and coronal CT (b) after CE. A hyperdensive tumour of the tuberculum of the sella turcica is seen (hyperostosis of the tuberculum of the sella turcica is present). Sagittal reformation (c) ascertains the expansion of meningioma
Fig. 6.117a–c Meningioma of the tuberculum of the sella turcica. Sagittal (а) and coronal (b) Т2- and Т1-weighted images (c). An isointensive
tumour is seen (hyperostosis of the tuberculum of the sella turcica is present)
596
Chapter 6
Fig. 6.118a–f Meningioma of the tuberculum of the sella turcica.
Т1-weighted image (а) and Т2-weighted images (b–d). A tumour of the cavity of the sella turcica is seen (hyperostosis of the tuberculum of the sella turcica is present), and hyperpneumatisation of the sphe-
noidal sinus is revealed. 3D TOF MRA reveals a typical bow-shaped upward displacement of the A1 segment of the anterior cerebral arteries (e,f)
Fig. 6.119 Meningioma of the tuberculum of the sella turcica and the right clinoid process, invading the cavernous sinus. Coronal Т1-weighted image. Enveloping of the right internal carotid artery siphon by the tumour tissue is seen as well as its narrowing (arrow)
Sellar and Parasellar Tumours
597
Fig. 6.120a–c Meningioma. Т1-weighted images before (а) and after (b,c) CE reveal a tumour, with invasion of the sella turcica. Meningioma is characterised by a homogenous accumulation of contrast medium
Fig. 6.121a–c Meningioma of the anterior clinoid process.
Т2-weighted image (а), and Т1-weighted images before (b) and after (c) CE. The tumour’s matrix originating from the anterior clinoid
process of the sphenoid bone is seen. Meningioma is characterised by a homogenous and intensive accumulation of contrast medium. Here it envelopes the internal carotid artery siphon
598
Chapter 6
Fig. 6.122a–c Relapse of neurinoma of the right trigeminal nerve. MRI reveals a tumour with heterogeneous structure on Т2-weighted image (а), and Т1-weighted images (b,c). Foci of cystic degeneration are present in the tumour. Postsurgical changes of the temporal lobe are seen laterally to the tumour
Weakness of mastication muscles and facial pain are less frequently found. Due to compression of the adjacent cranial nerves, diplopia may ensue. The most typical growth of neurinomas is a growth along an affected nerve. Neurinomas are isodensive on routine CT scans, and hyperdensive after CE, and on MRI they are hypo- or isointensive to brain tissue on T1-weighted imaging and hyperintensive on T2-weighted imaging (Fig. 6.122). Small tumours are homogenous, and larger ones usually have heterogeneous signal intensity. Multiplanar MRI is helpful to identify a tumour expansion. However, CT, especially with bone window, is more helpful in the assessment of erosion of the pyramid apical part. As with meningiomas, neurinomas intensively accumulate contrast medium (Fig. 6.123), but have lower values of blood flow and volume on perfusion maps compared with meningiomas.
6.16 Metastases In 1–5% of cancer patients, symptomatic metastases in the pituitary are found (Kucharczyk and Montanera 1991). Prostate, lung, and breast cancers spread metastases to the skull base more frequently. Metastases from prostate cancer are osteoplastic and may mimic meningiomas, whereas metastases of lung cancer and breast cancer are usually osteolytic. Metastases in the pituitary affect the posterior lobe and infundibulum more frequently than the anterior lobe, which may be due to the direct blood supply of the neurohypophysis. Pathological studies reveal high incidence of pituitary involvement—up to 28.1% of all brain metastases; however, these lesions are small and often asymptomatic.
There are no certain signs of metastases; however, bone destruction is a feature of utmost importance (Figs. 6.124–6.126).
6.17 Paragangliomas Paragangliomas are rarely found in this region, but if present, they demonstrate sellar and parasellar growth. Differential diagnosis by CT or MRI is difficult. On MRI these tumours are clearly delimited from the adjacent tissues, they are round, and moderately homogenously hypointensive on Т1-weighted imaging and hyperintensive on T2-weighted imaging. The pivotal distinguishing features are homogenous and marked CE and abundant vascular net on direct angiograms (Figs. 6.127– 6.129). Nowadays, CT perfusion may be helpful in identification of paragangliomas of this region. The proximity of frontal and temporal lobes may explain why glial tumours of the latter structures may grow into the chiasmal–sellar region (Fig. 6.130) or disseminate along the CSF system, which is especially typical for the few highly malignant tumours of the CNS (Figs. 6.131, 6.132).
6.18 Arachnoid Cyst Arachnoid cysts are benign, congenital, intra-arachnoid mass lesions, which are filled with fluid and have CSF-like properties. They are often an occasional finding on CT or MRI in the cranial cavity, but more frequently, they are seen in the anterior third of the temporal fossa, making up about 1% of all intracranial nontraumatic mass lesions (Ciricillo et al. 1991).
Sellar and Parasellar Tumours
599
Fig. 6.123a–e Neurinoma of the left tri
geminal nerve. The tumour hyperintensive on Т2-weighted image (a), and hypointensive on T1-weighted image (b) is observed. The tumour compresses the optic chiasm (arrow). After CE, the signal intensity of the tumour increases, which helps to ascertain the tumour borders (c,d). MRA in a venous regimen identifies compression of the left cavernous sinus (e)
Fig. 6.124a–c Metastasis of lung cancer into the sphenoidal bone. Т1-weighted images before (а) and after (b,c) CE. A tumour of the sphe-
noidal bone clivus is seen. Accumulation of contrast medium in the intact pituitary tissue allowed ascertaining the upper margin of the tumour
600
Chapter 6
Fig. 6.125a–f Metastasis into the chiasmal–sellar region. Т2-weighted image (а) and Т1-weighted images (b,c) in the bottom of the third ventricle: a small tumour isointensive to brain tissue is seen. After CE (d–f), the tumour with intensive accumulation of contrast medium was revealed above the sella turcica
Sellar and Parasellar Tumours
601
Fig. 6.126a–c Cancer metastasis into the chiasmal–sellar region. CТ (а) reveals a tumour with intensive accumulation of contrast medium in the suprasellar cistern. Т1-weighted image before (b) and after CE (c). The intrasuprasellar tumour with prominent but heterogeneous CE is seen
602
Chapter 6
Fig. 6.127a–c Paraganglioma of the sellar and the parasellar region. Axial (а) and coronal
(b) T1-weighted images before and after CE. A dumbbell-shaped tumour with clear-cut contours, moderately hypointensive before and hyperintensive after CE, is seen (c,d). The image of internal carotid artery is the border between the two nodes
Sellar and Parasellar Tumours
603
Fig. 6.128a–c Paraganglioma of the sellar and the parasellar region. Sagittal (а) and coronal (b,c) T1-weighted images. A large, dumbbell-
shaped tumour moderately hypointensive to brain tissue is observed. Supratentorial and retrosellar growth as well as tumour invasion of the skull base is found
Fig. 6.129a–c Paraganglioma of the sellar and the parasellar region. Т1-weighted images (а,b). A large tumour moderately hypointensive to brain tissue is seen. Supratentorial, ante-, and retrosellar growth are demonstrated. Small haemorrhages are present in the tumour stroma. CT (c) ascertains the extent of skull base bones destruction
604
Chapter 6
Fig. 6.130a–c Malignant glioma of the frontotemporal region with suprasellar growth. MRI before (а) and after (b,c) CE
Fig. 6.131a–c Lymphoma of the suprasellar region. Т2-weighted image (а) and Т1-weighted images after CE (b,c) visualise a tumour with marked perifocal oedema along both optic radiations and CE
Sellar and Parasellar Tumours
605
Fig. 6.132a,b Metastatic dissemination of a germ cell tumour of the pineal region along the ventricular system. FLAIR (а) and Т1weighted images (b) after CE reveal a small tumour of the pineal region and metastases in the lateral ventricles, and the chiasmal exfoliation of the third ventricle
In 10–15% of cases, they are located in the chiasmal–sellar region (Wiener et al. 1987) and more frequently (in 75% of cases), they are found in children (Wester 1992). It is supposed that arachnoid cysts are developmental abnormalities of meninges; however, their precise aetiology is unknown. During the development of meninges, impairment of their cleavage may occur, and a pouch or a diverticulum may form with subsequent “lacing” from the subarachnoid space and formation of a separate cyst. Arachnoid cysts may be small and asymptomatic (Fig. 6.133), but may reach giant sizes and lead to according clinical manifestations (Fig. 6.134). On CT a well-delineated and nonenhancing hypodensive mass lesion is usually observed. MRI reveals a homogenous and well-delineated area of signal isointensive to CSF in all sequences. Changes of signal intensity are absent in the adjacent structures. A suprasellar arachnoid cyst existing for a long time may lead to deformation of the skull base. The walls of cyst do not accumulate contrast medium. Arachnoid cyst is isointensive compared to CSF, which makes it different from other cystic mass lesions (epidermoid tumours, CPH). MR myelography may help to identify the borders of a cyst more precisely by differentiating the CSF spaces where signs of pulsation are present.
6.19 Vascular Disorders: Aneurysm Saccular aneurysms in the chiasmal–sellar region may originate from the cavernous segment of the internal carotid artery as well as from its supraclinoid segment of it. Sometimes aneurysms of the anterior and posterior communicating and basilar arteries may invaginate into the suprasellar cistern. Giant aneurysms located there have clinical manifestations identical to tumours. Differential diagnosis should be made from tumours of the chiasmal–sellar region. Misinterpretation of an aneurysm as a tumour may lead to a surgical accident. Fortunately, MRI allows performing the differential diagnosis clearly.
Aneurysms are well delineated and give the so-called signal void effect on T1- and T2-weighted imaging, due to rapid blood flow. In addition, rapid blood flow causes marked artefacts on images, which are manifested by multiple shadows in the phase-encoding direction, which are important diagnostic feature themselves. CT or MRA may add information about an aneurysm (Figs. 6.135–6.138). It is noteworthy that thrombosis in the cavity of an aneurysm markedly changes its signal characteristics. Thrombi that fill aneurysms usually have laminar structures. They are hyperintensive on T1-weighted images (Fig. 6.139). Thrombosis of an aneurysm may be complete or partial. Haemosiderin deposits may be seen in the adjacent tissues because of old haemorrhage from an aneurysm. These deposits appear as rims of hypointensive signal on T2-weighted images or on gradient echo images. CT before and after CE is less specific than MRI findings are. That is why it is always feasible to add MRA or even direct angiography to CT, especially in doubtful and atypical cases (Figs. 6.140, 6.141).
6.20 Inflammatory Disorders Infections. Infectious disorders of the pituitary are exceptionally rare. There is an opinion that cases of acquired diabetes insipidus may be a result of viral infection of the supraoptic and the paraventricular nuclei of the hypothalamus (Daughaday 1985). Tuberculosis and syphilis that were frequently encountered in the chiasmal–sellar region in the past due to high incidence in the common population are now rare. Even bacterial infections are now rare and become symptomatic only after abscess formation. Nevertheless, two cases of mycotic abscesses of the parasellar region have been followed-up in the Burdenko Neurosurgical Institute. Pituitary abscesses are rare. Infection may disseminate into the sella turcica via a haematogenous route or directly from the infected sphenoidal or cavernous sinuses. The following
606
Chapter 6
Fig. 6.133a–d Arachnoid cyst of the suprasellar region. Т2-weighted image (а) and
Т1-weighted image (b) in the sagittal plane reveal the arachnoid cyst of the suprasellar region, which deforms adjacent brain structures. There is no difference between the signal intensity of the CSF spaces and the arachnoid cyst as well as an accumulation of contrast medium in the cyst walls (c,d)
Sellar and Parasellar Tumours
607
Fig. 6.134a–c Arachnoid cyst of the third ventricle. a CT: balloon-shaped dilatation of the third and the lateral ventricles. b Т1-weighted im-
age reveals marked dilatation of the third ventricle; the aqueduct of Sylvius is open (arrow). The bottom of the third ventricle is better seen in MR myelography (c)
Fig. 6.135a,b Saccular aneurysm of the right internal carotid artery. Т1-weighted image (а) and MRA (b). Giant saccular aneurysm of the sellar and suprasellar region is seen
608
Chapter 6
Fig. 6.136a–e Large saccular aneurysm
of the supraclinoid segment of the right internal carotid artery. Т2-weighted imaging (а,b) reveals a signal void effect and the pulsatile artefact of blood flow in the phase-encoding direction typical for saccular aneurysm. 3D TOF MRA (c) demonstrates an aneurysmatic sack, and its peripheral part is better visualised. CT before (d) and after CE (e). Saccular aneurysm shows prominent and homogenous CE
Fig. 6.137a–c Saccular aneurysm of the supraclinoid segment of the right internal carotid artery. Т2-weighted image (а) and Т1-weighted image (b). A signal-void effect typical for saccular aneurysm is seen on the medial wall of the siphon of the internal carotid artery. 3D TOF MRA (c) visualises the sack less clearly
Sellar and Parasellar Tumours
Fig. 6.138a–c Large saccular aneurysm of the supraclinoid seg-
ment of the left internal carotid artery. Т1-weighted image (а) and Т2-weighted image (b). There is a typical flow-void phenomenon
Fig. 6.139a–f Giant saccular aneurysm of the supraclinoid seg-
ment of the left internal carotid artery. Т2-weighted image (а) and Т1-weighted image (b). The aneurysm with prevalent thrombosis is seen in the left cavernous sinus; it has a hyperintensive signal on
609
(from sack of aneurysm) in chiasmal–sellar region. The aneurysm has a dumbbell shape. MRA in 3D PC mode (c) clearly identifies the functioning part of aneurysm
Т1-weighted imaging. 3D TOF MRA (c,d) and 3D PC (e,f) identify the relationship between the functioning part of the aneurysm and the part of aneurysm with thrombosis. d–f See next page
610
Fig. 6.139a–f (continued) Giant saccular aneurysm of the supraclinoid segment of the left internal carotid artery. The aneurysm with prevalent thrombosis is seen in the left cavernous sinus; it has a hy-
Chapter 6
perintensive signal on Т1-weighted imaging. 3D TOF MRA (c,d) and 3D PC (e,f) identify the relationship between the functioning part of the aneurysm and the part of aneurysm with thrombosis
Fig. 6.140a–c Intrasuprasellar pituitary adenoma. CT: a hyperdensive mass lesion is seen in the cavity of enlarged sella turcica with supra-
sellar expansion, and contours of the suprasellar part of the tumour are similar to a saccular aneurysm
Sellar and Parasellar Tumours
611
Fig. 6.141a–h Large saccular aneurysm of
the supraclinoid segment of the left internal carotid artery. CТ: intrasuprasellar hyperdensive mass lesion is revealed (а–c). The sella turcica is enlarged. Т1-weighted image (d), PD-weighted images (e,f), and FLAIR (g). A hypointensive mass lesion is seen in the sella turcica and in the suprasellar region on PD-weighted and FLAIR images. Direct angiogram clearly identifies a large functioning aneurysm (h)
612
Chapter 6 Fig. 6.142a,b Abscess of the pituitarygland. T1-weighted images before (а) and after (b) CE: a mass lesion in the right half of the cavity of the sella turcica is seen, and the pituitary infundibulum is displaced rightwards. Increase of signal intensity of the walls of abscess is revealed after CE (b); remnants of the pituitary are displaced rightwards
causes of infections in the sella turcica may be seen also: pituitary adenoma, Ratke’s cleft cyst, and CPH (Daningue 1977; Selosse 1980; Gupta 1989). The most common clinical manifestations are headaches and visual loss, as abscesses clinically often are similar to hormonally inactive pituitary adenomas. Diagnosis of the abscess of the sella turcica is an exceptionally rare occasion. MRI without CE reveals a mass lesion of the sella turcica indistinguishable from adenoma. After CE, a rim of enhancement is seen on periphery, and the hypointensive area remains in the centre (Fig. 6.142). Parasellar infection. Infection of the suprasellar cistern and the cavernous sinuses is usually a part of a disseminated process and is encountered in cases of intracranial dissemination of the extracranial infection. Brain base meninges and meninges covering the suprasellar cistern are sensitive to tuberculosis and other forms of granulomatous meningitis. Parasitic cysts may also be situated in the cistern, especially cysticercosis. Infection of the cavernous sinuses with their secondary thrombosis is a dangerous complication of periorbital or the others inflammatory disorders (furunculosis, abscesses, etc.) Mucocele is a mass lesion located in the paranasal sinuses (Delfini 1993). If located in the sphenoidal sinus the differential diagnosis should be made from tumours of the chiasmal– sellar region. It is seen in children younger than 10 years but may be encountered in adults also. Mucocele is an accumulation of mucus developing after occlusion of a sinus, usually due to inflammatory origin. Trauma or tumour may also be accompanied by secondary mucocele. If the content of mucocele is infected, it is then called a mucopyocele. Mucocele appears as a well-delimited structure filling the sinus. Frequently it is the sphenoid sinus, which may markedly enlarge in size. On CT, mucocele appears as a hypodensive structure (Fig. 6.143). On MRI, the signal of mucocele varies. In our observations, mucocele had hyperintensive signal on T1- and T2-weighted images, which was probably connected with high protein level and elements of blood decay in its content (Fig. 6.144).
Non-infectious inflammatory disorders. Lymphocytic inflammation of the pituitary is a rare inflammatory disorder. It is usually seen during late pregnancy or the postnatal period. It is probably an autoimmune disorder connected with other autoimmune endocrinological disorders such as Hashimoto’s thyroiditis. In some cases, circulating autoantibodies to prolactin are revealed. The disorder is characterised by diffuse infiltration of the adenohypophysis by lymphocytes and sometimes by plasma cells. Females complain of headache, memory loss, postnatal amenorrhea, lactation impairment, or the combination of the above-mentioned symptoms. The level of pituitary hormones is decreased. CT and MRI demonstrate a diffuse enlargement of the anterior lobe of the pituitary, without any focal changes (Quencer 1980; Levine et al. 1988). Sarcoidosis is a chronic polysystemic inflammatory disorder of unknown aetiology. The pulmonary lymphatic nodes are most frequently affected, which are followed by the skin and eyes. CNS involvement is seen in approximately 5% of cases of sarcoidosis. This disorder affects both sexes and may be seen a little more frequently in females than in males. Any part of the CNS may be involved. Involvement of the hypothalamic–pituitary system is usually manifested by diabetes insipidus, or by deficiency of a single or many other hormones of the anterior part of the pituitary. Clinical manifestations of the disease completely depend on the affected site. The onset is usually painless, but the course is progressive. This disorder usually responds well steroid treatment. MRI reveals thickening of infundibulum of the pituitary and the bottom of the third ventricle, and thickening and deformation of cranial nerves and meninges (Scott 1993). There are no characteristic features of pathological lesions on MRI, which is why precise differential diagnosis is difficult, unless systemic sarcoidosis is proven. Multiple disseminated intraparenchymal and meningeal lesions suggest such a diagnosis. Tolosa-Hunt syndrome is an idiopathic inflammatory disorder of the cavernous sinus. Its clinical manifestations are prominent retro-orbital pain, and neuropathies of the third, fourth, and sixth cranial nerves and the first branch of the
Sellar and Parasellar Tumours
613
Fig. 6.143a–e Mucocele of the sphenoidal
sinus. Axial (а,b) and coronal CT (c–e). The sphenoid bone is filled with a hypodensive structure, with elements of partial bone destruction of the lateral walls. The pituitary gland and cavernous sinuses are displaced upwards
614
Chapter 6
Fig. 6.144a–d Mucocele of the sphenoidal sinus. Т1-weighted images (а–c) and
Т2-weighted images (d). Abnormal hyperintensity is seen in the left half of the sphenoidal sinus due to high protein content in the cyst
fifth cranial nerve, with less frequent involvement of the optic nerve and the sympathetic ganglions around the cavernous segment of the internal carotid artery. Symptoms may persist for several days or weeks both, with spontaneous remissions and relapsing. Pathologically the process resembles an orbital pseudotumour. CT usually fails to reveal any changes in this condition (Aron-Rosa et al. 1978,) or insignificant changes are found such as asymmetrical enlargement of the cavernous sinuses, CE in the prepontine cistern, or abnormal density of the soft tissues in the orbital apex (Kwan et al. 1987). Enlargement of the cavernous sinus on the affected side is revealed along with MR signal isointensive to orbital muscles on T1weighted imaging and isointensive to fat on T2-weighted imaging. The expansion of changes onto the apex of the orbit is seen, which suggests the similarity of this syndrome to orbital
pseudotumour in aetiology (Yousem et al. 1989). The disorder is responsive to steroid therapy. The differential diagnosis of Tolosa-Hunt syndrome should be made from sarcoidosis, meningioma, lymphoma, metastasis into the cavernous sinus, and actinomycosis. Sheehan’s syndrome. It is known that after pregnancy the pituitary undergoes marked structural changes. This leads to marked decrease of its sensitivity threshold to influence of different pathological factors, such as to ischemia in complicated delivery. As a result, some females develop ischemic necrosis of the adenohypophysis in the early postnatal period, with possible haemorrhage into the necrotic area and a shock-like reaction (Sheehan 1961). On MRI, enlargement of the adenohypophysis is revealed, and if a haemorrhage is present, then the picture resembles that of infarction of the pituitary.
Sellar and Parasellar Tumours
615
Refere n c e s Abe T et al (2002) Evaluation of pituitary adenomas by multidirectional multislice dynamic CT. Acta Radiol 43:556–559 Ahmadi J (1985) et al. Cavernous sinus invasion by pituitary adenomas. AJNR 6:893-899 Bills DC et al. (1993) A retrospective analysis of pituitary apoplexy. Neurosurg. 33:602-609 Aron-Rosa D, Doyon D, Salamon G, Michotey P (1978) Tolosa-Hunt syndrome. Ann Ophthalmol 10:1161–1168 Carmel P (1985) The empty sella syndrome. In: Wilkins R, Reganchary S (eds) Neurosurgery. McGraw-Hill, New York, pp 884–888 Carmel P, Antunes J, Chang C (1982) Craniopharyngiomas in children. Neurosurgery 11:382–389 Ciricillo S et al (1991) Intracranial arachnoid cysts in children: a comparison of the effects of fenestration and shunting. J Neurosurg 74:230–235 Daningue J, Wilson C (1977) Pituitary abscesses: report of 7 cases and review of the literature. J. Neurosurg. 46:601-608 Daughaday W (1985) The anterior pituitary. Willian’s textbook of endocrinology. Ed. by Wilson J., Foster D. 7th ed. Philadelphia: Saunders pp. 568-612 Delfini R et al. (1993) Mucoceles of the paranasal sinuses with intracranial and intraorbital extension: report of 28 cases. Neurosurg., 32:901-906 Dietrich R et al. (1995) Normal MR appearance of the pituitary gland in the first 2 year of life. AJNR. 7:1413-1419 Elster A et al. (1990) Pituitary gland: MRI of physiologic hypertrophy in adolescence. Radiology 174:681-685 Elster A et al. (1991) Size and shape of the pituitary gland during pregnancy and post partum: measurement with MR imaging. Radiology 181:531-535 Fujisawa I et al.(1987) Transection of the pituitary stalk: development of an ectopic posterior lobe assessed with MRI. Radiology 165:487-489 Gualdi G et al (1991) Unusual MR and CT appearance of an epidermoid tumour. AJNR Am J Neuroradiology 12:711–772 Gupta R (1989) Sellar abscess associated with tuberculosis osteomyelitis of skull: MR findings. AJNR Am J Neuroradiology 10:448–454 Hemminghytt S et al. (1983) Computed tomographic study of hormone-secreting microadenomas. Radiology 146:65-69 Hoffman H et al (1992) Aggressive surgical management of craniopharyngiomas in children. J Neurosurg 76:47–52 Horowitz B et al. (1990) MR in intracranial epidermoid tumors: correlation of in vitro imaging with in vitro 13C spectroscopy. AJNR 11:299-302 Horvath E еt al (1999) Pituitary hyperplasia. Pituitary 1:169–179 Hoyt W et al. (1970) Septo- optic dysplasia and pituitary dwarfism. Lancet 1:893-894. Huk W, Cademann G, Friedmann G (1990) MRI of central nervous system diseases. Springer, Berlin Heidelberg New York, pp 229–276 Kadashev BA ed. (2007) Pituitary adenoma. Meditsina pp. 368
Kadashev BA et al. (1989) Topographo-anatomic classification of hypophyseal adenomas. Zh Vopr Neirokhir Im N N Burdenko. Sep-Oct (5):7-10 ( in Russian) Kelly W et al (1988) Posterior pituitary ectopia: an MR feature of pituitary dwarfism. AJNR Am J Neuroradiology 9:453–460 Kim J et al (2004) Surgical treatment symptomatic Ratke’s cleft cysts: clinical features and results with special attention to recurrence. J Neurosurg 100:33–40 Konovalov A, Kornienko V, Ozerova V, Krasnova T (1983) Modern X-ray diagnostics of craniopharyngiomas. Vestn Rentgenol Radiol 3:5–12 (in Russian) Konovalov AN, Kornienko V.N. (1985) CT in neurosurgical clinic. Мeditsina pp. 293 Konovalov A, Kornienko V, Pronin I (1997) Magnetic-resonance tomography in neurosurgery clinics. Vidar, Moscow (in Russian) Konovalov A, Kornienko V, Qzerova V, Pronin I (2001) Pediatric neuroradiology. Antidor, Moscow (in Russian) Kovacs K, Horvath E, Asa S (1985) Classification and pathology of pituitary tumours. In: Wilkins RH, Reganchary SS (eds) Neurosurgery. McGraw Hill, New York, pp 834–842 Kucharczyk W, Montanera W (1991) The sella and parasellar region. In: Atlas SW (ed) MRI of the brain and spine. Raven, New York Kwan E, Wolpert S, Hedges T (1987) Tolosa-Hunt syndrome revisited: not necessarily a diagnosis of exclusion. AJNR Am J Neuroradiology 8:1067–1072 Levine S et al (1988) Lymphocytic hypophysitis: clinical, radiological, and magnetic resonance imaging characterisation. Neurosurgery 22:937–941 Maghnia M et al (1992) MR of the hypothalamic-pituitary axis in Langerhans cell histiocytosis. AJNR Am J Neuroradiology 13:1365–1371 Markus H, Kendall BE (1993) MRI of a dermoid cyst containing hair. Neuradiol. 35:256-257 Menor F et al. (1991) Imaging consideration of central nervous system manifestations in pediatric patients with neurofibromatosis type 1. Pediatr. Radiol. 21:389-394 Mizetskaya EA, Snigireva RI (1984) Endocrine disorders in “empty” sella turcica . Zh Vopr Neirokhir Im N N Burdenko. Nov-Dec (6):7-12 ( in Russian) Naidich T et al. (1983) Midline craniofacial dysraphism: midline cleft upper lip, basal encephalocele, callosal agenosis, and optic nerve dysplasia. Concepts Pediatr. Neurosurg. 4:186-207 Osborn A et al. (2004) Diagnostic Imaging. Brain. Amirsys Inc, Manitoba pp. 910. Ostrov S et al (1989) Hemorrhage within pituitary adenomas: how often associated with pituitary apoplexy syndrome? AJNR Am J Neuroradiology 10:503–507 Quencer R (1980) Lymphocytic adenohypophysitis: autoimmune disorder of the pituitary gland. AJNR 1:343-349 Rang T et al (2002) Evaluation of pituitary microadenomas with dynamic MRI. Eur J Radiol 41:131–135 Ross D A, Norman D, Wilson CB (1992)Radiologic characteristics and results of surgical management of Rathke’s cysts in 43 patients. Neurosurgery 30:173–179
616
Chapter 6
Russell D, Rubinstein L (1989) Pathology of tumours of the nervous system, 5th edn. Williams & Wilkins, Baltimore
Tatler G, Kendall B (1991) The radiological diagnosis of epidermoid tumors. Neuroradiol. 33(suppl):324-325
Sakamoto Y et al (1991) Normal and abnormal pituitary glands: gadopentetate dimeglumine-enhanced MR imaging. Radiology 178:441–445
Tien R D et al (1990) Thickened pituitary stalk on MR images in patients with diabetes insipidus end Langerhans cell histiocytosis. AJNR Am J Neuroradiology 11:703–308
Scheithauer B, Gaffey T, Lloyd R et al (2006) Pathobiology of pituitary adenomas and carcinomas. Neurosurgery 59:341–353
Van Effenterre R et al (2002) Craniopharingioma in adults and children: a study of 122 surgical cases. J Neurosurg 97:3–11
Schwartzberg D (1992) Imaging of pituitary tumours. Semin Ultrasound CT MR 13:207–223
Voelker J, Campbell R, Muller J (1991) Clinical radiographic and pathological features of Rathke’s cleft cysts. J Neurosurg 74:535–544
Scott T (1993) Neurosarcoidosis: progress and clinical aspects. Neurology 43:8–12
Wester K (1992) Gender distribution and sidedness of middle fossa arachnoid cysts: a review of cases diagnosed with computed imaging. Neurosurg. 31:940-944
Selosse P, Mahler M, Klaes R (1980) Pituitary abscess: report. J. Neurosurg. 53:851-852 Sheehan A, Stanford J (1961) The pathogenesis of post-partum a pituitary necrosis of the anterior lobe of the pituitary gland. Acto Endocrinol. 37:479-510
Wiener S N, Pearlstein AE, Eiber A (1987) MRI of intracranial arachnoid cysts. J Comput Assist Tomogr 11:236–241 Wilms G et al (1991) CT and MRI of ruptured intracranial dermoid tumours. Neuroradiol 33:149–151.
Singer W (1990) Does pituitary stalk compression confuse hyperprolactinemia? Endocr. Pathol. 1:65-67
Yousem D et al (1989) MR Imaging of Tolosa-Hunt syndrome. AJNR Am J Neuroradiology 10:1181–1184
Smith A et al (1991) Diagnosis of ruptured intracranial dermoid cyst: value of MR over CT. AJNR Am J Neuroradiology 12:75–180
Yuh W et al (1988) MR imaging of primary tumour of trigeminal nerve and Meckel’s cave. AJNR Am J Neuroradiology 9:665–670
Sze G et al (1988) Chordomas: MR imaging. Radiology 166:187–191 Takeuchi J, Handa H, Nagata I (1978) Suprasellar germinoma. J. Neurosurg. 49:41-48
Chapter 7
7
Infratentorial Tumours
7.1 7.2 7.3 7.4 7.5
Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Intra-Axial Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Extra-Axial Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Brainstem Lesions .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Меtastases .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
617 617 651 680 705
Extra-axial tumours are more frequent in adults; neurinomas and meningiomas, and epidermoid cysts follow them. Only 15–20% of all intra-axial masses in adults are infratentorial (Atlas 1991). Among them, hemangioblastoma and brainstem glioma predominate. Up to 20% of intracranial metastases seen in adults are in the posterior fossa (Lizak and Woodruff 1992; Lavaroni 1993).
7.2
Intra-Axial Tumours
7.2.1 Medulloblastoma 7.1
Introduction
Infratentorial tumours account for 50–55% of all brain tumours in children (Russell and Rubenstein 1989; HarwoodNash 1994; Atlas 1996; Ball et al. 1997; Barkovich et al. 2000; Osborn 2004). Infants (children younger than 1 year of age) are the exception, in whom supratentorial tumours predominate. The highest frequency of posterior fossa tumours is seen between 2 and 5 years of age (>60%). In the second decade of life, the incidence of the infratentorial tumours decreases and, conversely, the incidence of supratentorial tumours increases. The ratio is almost equal. Most of the infratentorial tumours are represented by tumours of the cerebellar hemispheres and brainstem; the tumours of the fourth ventricle rank in third place, and then follow meningeal tumours, and tumours of cranial nerves and of skull base structures (Gusnard 1990; Bilanuik 1990; Atlas 1991; Orrison 2000). Tumours of the cerebellar hemispheres and brainstem are represented by glial tumours of various tissue differentiations. Gliomas (astrocytomas of cerebellar hemispheres and brainstem, ependymomas of the fourth ventricle) are related to the most frequent infratentorial tumours in children neuro-oncological disease. Primary neuroectodermal tumours are second most common (medulloblastoma, ependymoblastoma, neuroblastoma), and are followed by choroid plexus tumours (papilloma, carcinoma), metastases, and cranial tumours (rhabdomyosarcoma, chordoma, chondrosarcoma).
Medulloblastoma is the most frequent infratentorial tumour in children (30–40% of all infratentorial tumours, according to different statistical sources), and it takes second place among all tumours of the CNS in this age group (up to 20%) (Meyers et al. 1992). Peak of incidence is the first decade of life, with predomination in boys (2:1 to 4:1). Medulloblastoma is a rapidly growing tumour—clinical manifestations develop within several weeks, and rarely, over more than several months. Symptoms are caused by compression of the CSF pathways and obstructive hydrocephalus. Medulloblastoma is an embryonic cerebellar tumour. Its histological origins are cells of the external granular layer of cerebellum and of the posterior cerebellar velum. Two histological variants are distinguished, medulloblastomas of “classic” structure and desmoplastic medulloblastomas. The latter are related to mesenchymal tumours and were called “cerebellar sarcoma” up until the 1970s. Most medulloblastomas, regardless of histology, grow through the cerebral pia matter into the subarachnoid space (SASP). Metastases of medulloblastomas along the CSF pathways are seen in 60% of cases. The most typical are small metastatic nodes in the cerebral and spinal SASP, in the walls of the lateral ventricles; however, large, solitary metastases may form within the chiasmal cistern and basal surface of the frontal lobes (Meyers et al. 2000). Despite the fact that medulloblastoma does not have a capsule, its stroma is compact, having clear-cut margins and a round shape; if a tumour is small, then its dorsal position in
618
relation to the cavity of the fourth ventricle is clearly seen. Most of medulloblastomas are solid, greyish-pink tumours, with small cysts and zones of haemorrhages inside. Three quarters of medulloblastomas affect the cerebellar vermis; medial parts of cerebellar hemispheres are also affected, and a tumour, displacing the fourth ventricle ventrally and obstructing its lumen, may infiltrate the dorsal surface of brainstem. The caudal pole of a tumour usually expands into the cisterna magna (Fig. 7.1). In contrast to ependymoma, medulloblastomas typically do not expand into the lateral cistern; however, this may occur in some cases (Fig. 7.2). Lateral location of medulloblastomas is more typical in older children (Fig. 7.3), and tumours usually have less clear-cut margins and more frequently (15–20%), formation of cysts is seen. In typical cases, medulloblastomas are identified on CT as oval or round masses, with heterogeneous CE. They are situated within the cerebellar vermis and medial parts of the cerebellar hemispheres, and they displace or fill the fourth ventricle. Frequently (but less often than on MRI) cysts are found (up to 65%); also, microcalcifications are identified (Fig. 7.4). In most cases, hydrocephalus of the superior parts of the ventricular system is present as well as peritumoural oedema (90–95%). CE is seen in more than 90% of cases and is prominent; however, tumours with absence or minimal CE are reported too. Sometimes, haemorrhages into a tumoural tissue or a necrotic cavity do occur (Fig. 7.5). On MRI medulloblastomas have heterogeneous abnormal signal, usually low (to some extent) on T1-weighted imaging, and on T2-weighted imaging, the signal may be hypo- or hyperintensive (Koller et al. 2003) (Figs. 7.4, 7.6). On sagittal scans, superior and inferior poles of a tumour are well seen; the latter is usually located in the cisterna magna. Complete MRI of the brain and spinal cord with CE, which is always recommended when medulloblastoma is suggested, allows seeing whether a tumour produced metastases along the SASP (Fig.
Fig. 7.1 Medulloblastoma. MRI demonstrates a mass lesion with-
in the inferior portions of the fourth ventricle and the cerebellar vermis
Chapter 7
7.7). The type of accumulation of contrast medium is variable; frequently it is heterogeneous (Meyers et al. 1992) (Fig. 7.8). A few cases are reported in which medulloblastomas spread metastases into bones, including vertebrae (where metastases cause osteolytic changes), as well as to the abdominal cavity after shunting operations for obstructive hydrocephalus that a tumour has caused. Differential diagnosis should be made from PA, EP, choroid papilloma, rhabdoid–teratoid tumours, and brainstem glioma with exophytic growth.
7.2.2 Cerebellar Astrocytoma Astrocytoma is one of the most frequent infratentorial tumours (after medulloblastomas) in children. Astrocytoma accounts for 30–40% of all infratentorial tumours in children. Histologically, they present as PA (juvenile, in 75–85% of cases) and fibrillary astrocytoma with diffuse growth (15– 20%). Malignant tumours such as anaplastic astrocytoma and glioblastoma, or oligodendroglioma, are rarely encountered. Astrocytomas usually grow in the cerebellar hemispheres (40% of cases) and brainstem (20% of cases). In adults diffuse brainstem gliomas are diagnosed; pilocytic and fibrillary astrocytomas of the cerebellar hemispheres are seen less often.
7.2.2.1
Pilocytic Astrocytoma
PA are a benign form of astrocytoma. Largely, the form and the type of growth of PA are determined by their location and patient age. In particular, PA of the cerebellar hemispheres forms a small solid node in the wall of large tumour cyst. Typical cerebellar PA in children is a cystic tumour (60–80%), whereas in adults solid PA of the cerebellar hemispheres is typical. PA frequently occurs within the first decade (that is why it is termed juvenile PA). If radically removed, then prognosis of the tumour is favourable; the 5-year survival rate is 86–100%, and the 20-year survival rate is 70% (Fernandez et al. 2003). In most cases PA are medially located, thus originating from the cerebellar vermis and medial parts of the cerebellar hemispheres (85%). Lateral parts of the cerebellar hemispheres are less frequently affected (15% of cases). Usually, a tumour consists of a large cystic portion with a clearly delineated node near one of the cyst walls. A cyst appears hypodensive on CT, often mildly hyperintensive on T1-weighted imaging, and strongly hyperintensive on T2-weighted imaging (Fig. 7.9). Appearance of a solid component, its shape, and size are variable, as well as type of CE (Figs. 7.10–7.12). CE is observed in 95% of cases. CE of cystic walls is variable; it may be absent or prominent (Figs. 7.13, 7.14). Pure, solid PA are rarely encountered (10%). On CT, calcifications may be found in 10–20% of tumour stroma (Fig. 7.15). If a tumour is located in the cerebellar vermis or medial parts of the cerebellar hemispheres, then hydrocephalic dilation of the superior parts of the ventricular system is seen on MR examination (Fig. 7.16).
Infratentorial Tumours
619
Fig. 7.2a–d Medulloblastoma (a 5-year-old child). CT (а) with CE reveals a hyperdensive
tumour of the cerebellar vermis, the fourth ventricle, and how a tumour extends through the foramen of Luschka into the pontocerebellar cistern. MRI (b–d) adds to CT findings giving important information about the distribution of tumour
Fig. 7.3a,b Medulloblastoma. Т2-weighted image (а) and Т1-weighted image (b) after CE reveal a large tumour in the lateral portions of the left half of the posterior fossa, which intensively accumulates contrast medium. The brainstem and the fourth ventricle are compressed
620
Chapter 7
Fig. 7.4a–f Medulloblastoma (a 6-year-old child). On a series of axial CT with CE (а,b), a hyperdensive tumour is revealed into the fourth ventricle. A microcalcification within the tumour is seen. MRI shows a heterogeneous mass lesion hyperintensive on T2-weighted imaging (c) and hypointensive on T1-weighted imaging (d). A tumour heterogeneously accumulates contrast medium (е,f)
Infratentorial Tumours
621
Fig. 7.5a–d Medulloblastoma (a 2-year-old child). On CT (а) within the left half of the
posterior fossa, a large tumour with many calcifications is revealed. On Т2-weighted image (b) and Т1-weighted images (c,d), a tumour occupies most of the left half of the posterior fossa, with craniospinal and supratentorial spread. Cystic degeneration and haemorrhages are seen in the tumour stroma
622
Chapter 7
Fig. 7.6a–c Medulloblastoma. MRI shows a homogenous mass lesion into the fourth ventricle, hyperintensive on Т2-weighted imaging (а)
and hypointensive on Т1-weighted imaging (b,c)
Fig. 7.7a,b Medulloblastoma. On Т2weighted imaging (а) and Т1-weighted imaging (b–d) tumour nodes (metastases) are seen in the walls of the lateral ventricles and in the left frontal region beside a tumour in the cerebellar vermis and the fourth ventricle. c–f see next page
Infratentorial Tumours
623
Fig. 7.7c–f (continued) Medulloblastoma. On Т2-weighted imaging (а) and Т1-weighted imaging (b–d) tumour nodes (metastases) are seen in the walls of the lateral ventricles and in the left frontal region beside a tumour in the cerebellar vermis and the fourth ventricle. MRI of brain and spinal cord with CE (f) reveals diffuse metastatic dissemination in the subarachnoid spaces
Fig. 7.8a–c Medulloblastoma. On Т1-weighted imaging before (а) and after CE (b,c), a tumour within the fourth ventricle and the cerebellar vermis is seen. CE is prominent and heterogeneous
624
Chapter 7
Fig. 7.9a–d PA (a 6-year-old child). CT image (а) shows a hypodensive mass lesion into
the fourth ventricle. Tumour on Т2-weighted imaging (b) and Т1-weighted imaging (c,d) is filling the fourth ventricle cavity and protruding from the right foramen of Luschka. The margin between the tumour and brainstem is clear
Fig. 7.10a–e PA. On CT (а), Т2- and Т1-weighted images (b,c) and Т1-weighted images after CE (d,e): a tumour of mixed structure in the fourth ventricle is seen. d,e See next page
Infratentorial Tumours
625
Fig. 7.10a–e (continued) PA. On CT (а),
Т2- and Т1-weighted images (b,c) and Т1weighted images after CE (d,e): a tumour of mixed structure in the fourth ventricle is seen
Fig. 7.11a–d PA. On Т2-weighted imaging (а) and Т1-weighted imaging before (b) and after (c,d) CE, a tumour of mixed structure in the fourth ventricle and the right cerebellar hemisphere is observed, and lesion accumulates contrast medium intensively
626
Chapter 7
Fig. 7.12a–d PA. Т2-weighted imaging (а,b) and Т1-weighted imaging (c,d) shows a tumour with mixed structure in the left cerebellar hemisphere, with predominantly solid components
Fig. 7.13a–c PA of the left cerebellar hemisphere and the cerebellar vermis. MRI before (а,b) and after (c) CE. A tumour of heterogeneous
structure is seen, with clear borders. The cystic part of a tumour is hyperintensive on Т2-weighted imaging. CE has heterogeneous character
Infratentorial Tumours
627
Fig. 7.14a–d PA of the right cerebellar hemisphere and the cerebellar vermis. The cystic
part of a tumour is hyperintensive on Т2-weighted imaging (a). On T1-weighted imaging before (b) and after (c,d) CE, a tumour with heterogeneous structure is seen; the walls of the tumour’s cyst intensively accumulate contrast medium
Fig. 7.15a–c PA of the cerebellum. СT (а) reveals a tumour with calcification and a cyst component in the cerebellar vermis and both hemispheres. On Т2-weighted imaging (b,c) an area of MR signal
changes is more extensive than on CT. The cystic part of the tumour is hyperintensive on Т2-weighted imaging, the solid part does not differ much from brain tissue
628
Chapter 7
Fig. 7.16a–c PA of the cerebellar vermis and the left cerebellar hemisphere (an 8-year-old child). There is a tumour of heterogeneous structure with a large cystic component on Т2-weighted imaging (а)
and Т1-weighted imaging (b,c) after CE. The walls of the cyst do not accumulate contrast medium, and dilatation of the third and the lateral ventricles was found
Differential diagnosis should be made from medulloblastoma, ependymoma, hemangioblastoma, ganglioma, and atypical demyelinative disorders. Among fibrillary (diffuse) astrocytomas of low-grade (LGA) are distinguishable, as are anaplastic astrocytomas (AnA) and glioblastomas (GB). However, the latter two types (especially GB) affect the posterior fossa rarely. These tumours are characterised by diffuse growth and unfavourable prognosis as a rule.
gel-like. Intratumoural cysts may form; haemorrhages are not typical. On CT, these tumours look like iso- or hypodensive masses, poorly delineated from adjacent brain tissue. If the density of a tumour is identical to that of brain tissue and mass-effect is absent, then tumours may not be identified at all. Calcifications are rarely found in the tumour stroma (<20% of cases). CE is heterogeneous or absent. Expansion of involvement is better seen on MRI. On MRI, LGA are iso- or hypointensive on Т1-weighted images and have heterogeneously hyperintensive signal on T2-weighted images. Abnormal area has unclear contours; perifocal oedema is minimal (Figs. 7.17, 7.18). Cystic forms of tumours are frequent (Fig. 7.19). CE varies from prominent to negligible (Figs. 7.20, 7.21). However, as a rule, fibrillary LGA do not show CE, and it is one of the differential features that distinguishes them from PA. Haemorrhages in the solid or the cystic parts of a tumour are rare exceptions.
7.2.2.2
Low-Grade Astrocytomas
LGA largely represents a tumour that only slightly differs from the brain tissue by it colour and density; it is characterised by infiltrative growth, and its contours are lost in the intact structures. Tumour consistency varies from solid to
Fig. 7.17a,b Fibrillary astrocytoma of the
cerebellar vermis and the left cerebellar hemisphere. On sagittal (а) and axial (b) MRI, there is a large tumour with heterogeneous structure. The cystic part of the tumour is hypointensive on Т1-weighted imaging (a) and hyperintensive on Т2-weighted imaging (b)
Infratentorial Tumours
629
Fig. 7. 18a,b Fibrillary astrocytoma of the
cerebellum. On Т2-weighted imaging (а) and Т1-weighted imaging (b), a tumour with a predominant cystic component is seen in the medial parts of the cerebellar hemispheres, without perifocal oedema
Fig. 7.19a–d Fibrillary astrocytoma of the cerebellum. Т2-weighted imaging (а) and
Т1-weighted imaging (b) shows a tumour with heterogeneous structure in the medial parts of the cerebellar hemispheres. CE (c,d) improves visualisation of the tumour structure and location
630
Chapter 7 Fig. 7.20a,b Fibrillary astrocytoma of the
left cerebellar hemisphere. On Т1-weighted images before (а) and after (b) CE, a tumour is revealed, which intensively accumulates contrast medium. The area of low signal corresponds to the cystic component within the tumour
Fig. 7.21a–d Fibrillary astrocytoma of the right cerebellar hemisphere. On CT (а), a
tumour with heterogeneous structure is revealed, with a cystic component and expanding onto the brainstem. On Т2-weighted imaging (b), and Т1-weighted imaging before (c) and after (d) CE, a large and widely expanding tumour of the right cerebellar hemisphere is seen. The tumour has infiltrative features because there are no clear margins between neoplasm and brainstem
Infratentorial Tumours
631 Fig. 7.22a,b AnA of the right cerebellar
hemisphere. There is a large area of abnormal MR signal, with involvement of the right half of pons on Т2-weighted images (а,b)
7.2.2.3
Anaplastic Astrocytomas
AnA occupies an intermediate position between LGA and GB. Largely, AnA are tumours with cysts, haemorrhages, and infiltration of adjacent brain tissue at the periphery. Heterogeneous density on CT and intensity on MRI T1- and T2-weighted imaging is typical for AnA (Fig. 7.22). Marked peritumoural oedema is more typical for this type of tumour. Areas of hyperintensive MR signal on Т1-weighted imaging and hypointensive MR signal on Т2-weighted may point out haemorrhagic components. Heterogeneous CE of the tumour stroma is typical; peripheral CE may also be identified (Fig. 7.23). In rare cases, CE is absent.
7.2.2.4
Glioblastoma
GB is a rare infratentorial tumour. More frequently, GB is situated in the cerebellar hemispheres or vermis, rarely in the brainstem. CT and MRI features of GB are nonspecific (Kuroiwa et al. 1995). Differential diagnosis from metastasis is difficult. Nevertheless, its heterogeneous density on CT and intratumoural haemorrhages seen on MRI, heterogeneous ring-shaped CE, wider area of infiltration, and marked peritumoural oedema suggest this type of tumour (Figs. 7.24, 7.25).
7.2.2.5
Ependymoma
EP make up 8–10% (or up to 16% according to several reports) of all primary intracranial tumours in children and 15% of all infratentorial tumours. The peak of incidence in children is below the age of 5 years. EP are more frequently infratentorial (70%), and in 30% of cases, they are supratentorial. In adults, they are rarely seen (Hendrick and Raffel 1989). Infratentorial EP originate from ependymal cells lining the fourth ventricle, which is why they may grow out of its bottom or cover (the latter is less often), and they may grow along the
tela chorioidea, which goes from the lateral exits of the fourth ventricle, into the cerebellopontine cistern. This explains why EP lateral expansion into the cerebellopontine cistern is typical. Often (up to 60%) a tumour expands through the foramen of Magendie, into cisterna magna and even into the superior part of the vertebral canal. Such growth is typical for EP. EP has a soft and lobular consistency. Along with this, in 30–40% of cases, EP infiltrate adjacent brain tissue. In addition, tumours usually tend to grow around vessels and cranial nerves, which makes its radical removal difficult (Korshunov et al. 2004). In most cases, infratentorial EP are benign, but anaplastic EP exist (Korshunov et al. 2003). On routine CT, EP is isodensive relative to brain tissue and is mainly represented by solid masses. Formation of cysts is seen in 20% of cases. Small calcifications are seen in 50% of cases, which makes EP the most frequent type of infratentorial tumours with calcifications. CE on CT is moderate, and as a rule, heterogeneous, improving imaging of a tumour structure and margins mildly. On MRI, typical EP appear as heterogeneous structures with uneven surface filling, or they completely occupy the cavity of the fourth ventricle and expand into the cisterns magna or the lateral pontine cistern. The solid part of EP appears hypointensive on Т1-weighted images and hyperintensive on T2weighted images (Figs. 7.26–7.28). Cysts give more hyperintensive signal than that of the CSF on T1-weighted images and look brighter on Т2-weighted images relative to tumour tissue. The signal heterogeneity of the tumour stroma is due to cysts, microcalcifications, foci with newly formed vessels, and less often, microhaemorrhages (Fig. 7.29). Such EP show moderate and heterogeneous CE on CT (Figs. 7.30–7.34). Nevertheless, a small per cent of EP do not enhance. If a tumour is large and occludes the fourth ventricle and foramen of Magendie, then hydrocephalus often develops. Malignant EP have structure more heterogeneous and produce more prominent CE; however, exceptions are possible (Figs. 7.35–7.37).
632
Chapter 7
Fig. 7.23a–c Ana. On Т2-weighted imaging (а), and Т1-weighted imaging before (b) and after (c) CE, a tumour without clear margins and
hyperintensive signal on Т1-weighted imaging was found. CE is moderate and improves visualisation of the tumour expansion
Fig. 7.24a–c GB (a 7-year-old child). On CТ (а), there is a tumour with heterogeneous structure in the left cerebellar hemisphere and the
fourth ventricle. On Т1-weighted images before (b) and after (c,d) CE, a tumour with heterogeneous structure is seen. The infiltration of pons is visible. d See next page
Infratentorial Tumours
633
Fig. 7.24d (continued) GB (a 7-year-old child). On CТ (а), there is a tumour with
heterogeneous structure in the left cerebellar hemisphere and the fourth ventricle. On Т1weighted images before (b) and after (c,d) CE, a tumour with heterogeneous structure is seen. The infiltration of pons is visible
Fig. 7.25a–f GB of the cerebellum. On a series of CT (а–f) with CE, a large tumour is seen affecting the left cerebellar hemisphere, brainstem,
and giving metastatic dissemination in ependyma of the lateral and the third ventricles
634
Chapter 7
Fig. 7.26a–d EP of the fourth ventricle (a 5-year-old child ). CT (а) shows a tumour with
heterogeneous structure and density in the fourth ventricle and the cerebellar vermis. On Т2-weighted imaging (b,c) a tumour is hyperintensive and hypointensive on Т1-weighted imaging (d). It has clear borders with brain tissue. The aqueduct of Sylvius is dilated, and CSF pulsation is observed
Fig. 7.27a–c EP of the fourth ventricle. On Т2-weighted imaging (а) and Т1-weighted imaging (b), a tumour is seen, which fills the cavity of
the fourth ventricle. Brainstem is compressed. Sagittal projection (c) ascertains the longitudinal aspect of the tumour
Infratentorial Tumours
635 Fig. 7.28a,b EP of the fourth ventricle. On
axial Т1-weighted imaging (а) and sagittal Т1-weighted imaging (b), a large tumour with heterogeneous structure fills the whole lumen of the fourth ventricle. A cystic part of the tumour is seen on T1-weighted imaging
Fig. 7.29a–c EP of the fourth ventricle (an 18-year-old patient), which was diagnosed for the first time at the age of 12. On axial (а) and sagittal (b) T2-weighted images, a large tumour of the fourth ventricle, expanding onto the superior portions of the vertebral ca-
nal is seen. Areas of hyperintensive signal in the tumour stroma are microcysts. A tumour is mildly hypointensive on Т1-weighted imaging (c)
636
Chapter 7
Fig. 7.30a–e EP of the fourth ventricle. MRI shows a solid tumour in the inferior parts of the fourth ventricle and descending into the vertebral canal to the level of С2. On axial Т2-weighted imaging (а), expansion of the tumour through the foramen of Luschka leftwards into the pontocerebellar cistern is visible. The tumour does not differ from the brain tissue on Т1-weighted imaging g (b). CE (c,d) does not improve the tumour visualisation in this case due to weak focal accumulation of contrast medium in the abnormal tissue. On a series of CT with CE (e), the tumour is clearly visualised only in the lumen of the fourth ventricle
Infratentorial Tumours
637
Fig. 7.31a–e EP of the posterior fossa (a 6-year-old child). On CT with CE (а), a tumour with heterogeneous structure that intensively accumulates contrast medium is seen in the projection of cerebellar vermis and fourth ventricle. Only the cystic component of the tumour is clearly seen. Heterogeneous structure of the tumour is seen on MRI also. The cyst in the upper pole is hyperintensive on Т1-weighted imaging (b) and Т2-weighted imaging (c). After CE (d,e), visualisation of the tumour borders and its structure is improved
Fig. 7.32a–c EP. On Т2-weighted imaging (а) and Т1-weighted imaging (b) before (upper image) and after CE (lower image), a tumour with relatively homogenous structure that intensively accumulates
contrast medium is seen in the lateral angle of the fourth ventricle. Coronal MRI (c) also identifies the descending growth of the tumour
638
Fig. 7.33a–d EP. On Т2-weighted imaging (а) and Т1-weighted imaging (b) before CE, a tumour with heterogeneous structure is seen in the fourth ventricle. The microcysts in the tumour stroma are hyper-
Chapter 7
intensive on Т2-weighted imaging. The neoplasm intensively accumulates contrast medium (c,d). Sagittal image (d) demonstrates that the tumour grows into the vertebral canal
Infratentorial Tumours
Fig. 7.34a–f EP. On Т2-weighted imaging (а) and Т1-weighted imaging (b) before CE, a tumour with heterogeneous structure is seen in the fourth ventricle and the cerebellar vermis. The cysts in the tumour stroma are hyperintensive on Т2-weighted imaging and hy-
639
pointensive on T1-weighted imaging. The tumour moderately accumulates contrast medium (c–f). Sagittal and frontal images demonstrate the tumour growth into the cisterna magna
Fig. 7.35a,b Anaplastic EP. Sagittal Т1-
weighted imaging before (а) and after (b) CE reveals the mass lesion occupying a space from the aqueduct of Sylvius to the С2 level. Reliable data about the expansion of tumour and of the extent of brainstem invasion are acquired only after CE. Accumulation of contrast medium has heterogeneous characters; multiple small foci of necrosis are observed in tumour tissue
640
Chapter 7
Fig. 7.36a–c Anaplastic EP. T1-weighted imaging before (a) and after (b,c) CE reveals the mass lesion around of fourth ventricle and aqueduct of Sylvius
Table 7.1 Differences between infratentorial medulloblastoma, ependymoma, and astrocytoma Feature
Medulloblastoma
Ependymoma
Astrocytoma
Location
Median line
Median line
Eccentric
Origin
Superior cerebellar velum
Ependyma of the fourth ventricle Cerebellar hemispheres
Age of onset (years)
8–15
2–10
10–20
Formation of cysts
Rare
Often
Typical
Growth through foramina of fourth ventricle
Rare
Often (Luschka, Magendie)
No
Metastases in SASP
25–50%
Rare
Rare
CT without CE
Hyperdensive
Isodensive
Hypodensive
Calcifications
10–15%
40–50%
<10%
Т2-weighted imaging
Moderate intensity
Moderate intensity
Hyperintensity
CE
Moderate
Moderate
Depends on degree of malignancy
Infratentorial Tumours
Fig. 7.37a–f Anaplastic EP. Cerebral angiography in coronal (а,b) and lateral (c) projections show the superior and inferior cerebellar arteries are displaced upwards. The anterior and posterior inferior cerebellar arteries are displaced downwards. In the capillary phase (b), mildly developed vascular net of the tumour is seen. On CT be-
641
fore (d) and after (е,f) CE, an area of heterogeneous density change is seen in the left lateral half of the posterior fossa. The brainstem is compressed. The tumour shows heterogeneous accumulation of contrast medium; necrotic changes are better seen within it
642
Fig. 7.38a–i Variants of blood supply of hemangioblastomas of the posterior fossa. Case 1 (а–c). A tumour in the inferior pars of the cerebellar vermis, and a prominent vascular net with arteriovenous shunts in the arterial phase is seen on angiography. Case 2. von Hippel-Lindau disease (d–f). Vertebral angiography reveals multiple tu-
Chapter 7
mour nodes in both cerebellar hemispheres (S > D). Case 3 (g–i). A tumour of dorsal parts of the right cerebellar hemisphere. Abundant vascular net is visualised with arteriovenous shunts and marked venous drainage into confluence sinuum
Infratentorial Tumours
Table 7.1 gives the most typical neuroimaging findings of the most frequent infratentorial tumours. Differential diagnosis should be made from medulloblastoma, PA, subependymoma, hemangioblastoma, brainstem glioma, and metastasis.
7.2.2.6
Subependymoma
Subependymomas are soft tissue well-delineated tumours originating from the inferior parts of the fourth ventricle. They are typically small (<2 сm in diameter); however, sizes >5 cm have been described. They are represented in not more than 0.7% of intracranial tumours; so they are very rare. They are more frequently diagnosed between the ages of 50–60 years; in children, they are rarely seen (Wistler et al. 2000). On CT, subependymomas are initially iso- or hypodensive, and CE is minimal or absent. On T1-weighted images, most subependymomas are iso- to hypointensive relative to the white matter. On T2-weighted images, a tumour is hyperintensive, and its structure is heterogeneous due to microcysts and microcalcifications within the tumour stroma. The tumour is better visualised on FLAIR images as a hyperintensive mass that grows into the lumen of the CSF spaces. It is thought that CE is more typical for subependymomas of the fourth ventricle rather than for supratentorial tumours (Chiechi et al. 1995; Furie et al. 1995; Silverstein et al. 1995; Osborn 2004). Differential diagnosis should be made from EP, neurocytoma (growing into the fourth ventricle), choroid papilloma, medulloblastoma, hemangioblastoma, ganglioglioma, brainstem glioma with exophytic growth, cavernous angioma, and metastasis.
7.2.3 Hemangioblastoma Hemangioblastoma (HMB) are rarely seen benign tumours, the histological origin of which is debatable. HMB are represented in 1–2.5% of all intracranial tumours. Up to 20% of all HMB are seen in children. Up to 10% of cases are found as manifestation of von Hippel-Lindau syndrome (Conway et al. 2001, Wanebo et al. 2003). Among the primary infratentorial tumours, HMB are diagnosed in 8–12% of cases.
643
It is believed that HMB originate from primitive vascular mesenchymal cells or haemopoietic stem cells. On microscopy, HMB represents the accumulations of thin-walled vessels of different calibre. Interstitial cells with light cytosol rich with lipids are located in the intervascular spaces. There were distinguished four variants of HMB: 1. Solid tumour appearing as a soft, dark-cherry–coloured, encapsulated node, with a characteristic spongy picture on microscopic slice (25–30%) 2. Large, smooth-walled cyst with transparent-yellow content, with a mural nodulus on one of the walls (55–65%) 3. Mixed tumour: a large node with small cyst (4%) 4. Primitive cystic tumour appearing as a cyst with smooth walls without mural nodulus (6%) Cerebellar hemispheres are a common location of HMB (80– 85%), less often it is cerebellar vermis. They may affect the spinal cord (3–13%) and medulla oblongata (2–3%); rarely, they have supratentorial location. Rarely necrosis and haemorrhages are seen within HMB. A solid HMB nodulus is well contrasted on direct angiography, and its vascular net is observable until the late venous phase. In solid HMB, large abnormal arteries and veins are demonstrated; arteriovenous shunts may be identified (Fig. 7.38). CT and MRI data may help diagnose any of the distinguished types of the tumour (Elster et al. 1988). The cystic HMB is usually oval or round and is hypodensive on CT (8– 14 HU), and after CE, the density of the cyst and its walls do not change. The tumour node is seen on noncontrast CT as a mass homogenously hyperdensive relative to brain tissue. It is located on one of the walls of cyst, intruding in its lumen; it is intensively enhanced after administration of contrast medium (60–85 HU). In cases of solid forms, the HMB lesions become completely hyperdensive after CE (Ho et al. 1992) (Fig. 7.39). With the cystic form of HMB, MRI clearly reveals a cystic component that is hypointensive on T1-weighted imaging and hyperintensive on T2-weighted imaging. A solid node of tumour is seen in the background, and it is intensively enhanced (Figs. 7.40–7.42). With the solid form of HMB, round and curved areas of signal loss are seen in the tumour stroma, due to effect of large vessels within the tumour structure. Many vessels within HMB
Fig. 7.39a,b HBM. CT before (а) and
after (b) CE. An accumulation of contrast medium in the tumour is heterogeneous and intensive
644
Chapter 7
Fig. 7.40a–c HBM. A cystic mass lesion is seen in the right cerebellar hemisphere with the mural nodulus better identified on Т2-weighted imaging (а) than on Т1-weighted imaging (b). After CE (c), a tumour node intensively accumulates contrast medium
Fig. 7.41a–c HBM. MRI (a–c). In the medial parts of the right cerebellar hemisphere, a cystic mass lesion with a mural nodulus is found. The
latter is situated near foramen magnum and better identified on Т1-weighted imaging with CE
Infratentorial Tumours
Fig. 7.42a–c HBM. MRI (a–c). A large tumour with heterogeneous structure in the lateral parts of the left cerebellar hemisphere is seen. It has a cystic component that is situated medially to the tumour node and is clearly visualised on Т2-weighted imaging (а) and Т1-
645
weighted imaging (b). After CE (c), hyperintensive signal of the tumour is seen; the wall of the cyst does not accumulate contrast medium
Fig. 7.43a–c HBM. MRI (a–c). A large solid tumour is identified in the dorsal parts of the left cerebellar hemisphere. On Т2-weighted imaging (а), and Т1-weighted imaging before (b) and after (c) CE, many arteries are visualised within and around the tumour. The tumour node intensively accumulates contrast medium
646
Chapter 7
Fig. 7.44a–f HBM. MRI (a–f). A tumour with heterogeneous structure is seen in the right cerebellar hemisphere. On Т2-weighted imaging (а) and Т1-weighted imaging (b), many arterial vessels are seen around and inside the tumour. 3D TOF MRA (c,d) shows a prominent vascular net of the tumour with blood supply from intra- and
extracranial posterior circulation arteries. MR venography (e) identifies the venous net of the tumour. On MRS (f), elevation of the Lip–Lac complex peak is seen, and other brain metabolite peaks are almost absent. g–l see next page
better visualised on T2-weighted images is a pathognomonic feature of this type of tumour (Figs. 7.43, 7.44). In all such cases, especially in the craniospinal location, direct angiography is required to ascertain how multiple large vessels are situated and to determine the tactic of operation (Fig. 7.45). It should be noted that in von Hippel-Lindau disease, multiple HMB may be found intracranially as well as into the intravertebral canal. It is feasible to perform a complex MRI study of the CNS with mandatory CE, as small tumour nodes may not be visualised without intravenous enhancement (Fig. 7.46). Perfusion CT study is helpful in improving of preoperative differential diagnosis of HMB, especially in cases of solid tumour. CBV and CBF values estimated in the tumour are the highest
among all intra- and extra-axial infratentorial tumours (except paragangliomas) (Figs. 7.47, 7.48). However, the latter have typical location in skull base.
7.2.4 Choroid Plexus Tumours Choroid plexus tumours (ChP) are represented by three histological types: choroid papilloma, anaplastic choroid papilloma, and choroid carcinoma. Up to 40% of all ChP are infratentorial. The usual location is the inferior parts of the fourth ventricle and its lateral portions. Infratentorial ChP are more typical in adults, and supratentorial tumours are more
Infratentorial Tumours
647
Fig. 7.44g–l (continued) CT before (g) and after (h) CE visualises a mass lesion with prominent accumulation of contrast medium. 3D CT
AG reconstruction (i) adds information about relationship vascular and bone structures of posterior fossa. DSA (k,l) demonstrate blood supply of neoplasm
648
Fig. 7.45a–f HBM. On MRI at the level of the fourth ventricle, a tu-
mour of solid structure is seen, hyperintensive on Т2-weighted imaging (а) and isointensive on Т1-weighted imaging (b,c). Spot-like and tortuous areas of signal loss are dilated arteries supplying a tumour.
Chapter 7
The borders of a tumour become more distinguished after CE (d). Vertebral angiography confirmed abundant vascularisation of the tumour (е,f)
Infratentorial Tumours
Fig. 7.46a–f von Hippel-Lindau disease. Multiple HBM. MRI reveals
a large tumour with solid structure in the fourth ventricle and the cerebellar vermis. On Т2-weighted imaging (а) and Т1-weighted imaging with CE (b,c) many arteries are visualised within and around
649
the tumour, and prominent CE of tumour masses is seen. MRI of cervical and thoracic spine (d–f). A small additional tumour node are visualised with a large syringohydromyelia of the spinal cord
650
Chapter 7 Fig. 7.47a,b HBM. On CT with CE (а), a
small, round hyperdensive mass lesion in the fourth ventricle is seen. CТ perfusion map (CBF) shows an intensive blood flow almost identical to arterial blood flow (b)
Fig. 7.48a–c HBM. On axial CT with CE (а) a hyperdensive tumour with heterogeneous structure is seen in the right cerebellopontine angle. CТ perfusion maps (CBV, CBF) show intensive blood flow in the tumour stroma (b,c)
Fig. 7.49a–c Choroid plexus papilloma. A tumour with subacute haemorrhage inside with hyperintensive foci on Т2-weighted imaging (a) and Т1-weighted imaging (b,c) is seen in the lateral angle of the fourth ventricle. The tumour has a characteristic lobular structure
Infratentorial Tumours
typical in children. They account for not more than 1% of all intracranial tumours, but may reach 5% incidence in children (Hendrick and Raffel 1989). Differential neuroimaging diagnosis of ChP of the fourth ventricle with various histology is difficult and based on common signs of invasive growth (typical for more malignant tumours). Choroid papilloma is diagnosed more frequently than are other types. The tumour presents as a round mass lesion with a tuberous surface. In most cases, it is located in the cavity of the fourth ventricle and may partially invade the brainstem or medial parts of the cerebellar hemispheres. The most frequent clinical manifestation of the tumour located in the fourth ventricle is hydrocephalus and raised intracranial pressure. On CT as well as on MRI, the tumour appears as a mass lesion with large, lobular contours. On T1-weighted imaging, tumours are usually isointensive with the brainstem, and on T2-weighted imaging, they are moderately hyperintensive and may be confluent with the CSF signal. Microhaemorrhages may be visualised within the tumour stroma (Fig. 7.49). Calcifications of the fourth ventricle may be seen as rare exceptions. After CE on CT and MRI, prominent enhancement of the tumour is detected (Fig. 7.50). Perfusion studies reveal moderately increased perfusion parameters, which differentiate the tumour from other tumours localised in the fourth ventricle cavity, such as medulloblastomas and ependymoma.
7.3
Extra-Axial Tumours
7.3.1 Neurinoma (Schwannoma) Neurinomas (also known as schwannomas, neurilemmomas) are benign tumours originating from Schwann cells of cranial and spinal nerves. Neurinomas account for approximately 6–8% of all intracranial tumours. According to the Burdenko Neurosurgical Institute data, this tumour is seen in 7.2% of patients. Neurinomas more frequently are seen in the middle and the elder age group, with slight predominance in females (1.5−2:1). In children, neurinomas makeup about 2% of infratentorial tumours, often in patients with neurofibromatosis. Largely, neurinomas are round, sometimes-lobular masses, with marked connective tissue capsule. In some neurinomas, many vessels are seen, frequently with a thickened, hyalinated capsule; sometimes even venous lacunes are found. Infratentorial neurinoma often originates from the root of vestibulocochlear nerve (vestibular portion), being situated in the cerebellopontine angle; less often it originates from the trigeminal nerve root (in the Gasserian ganglion) and in on extremely occasion, of roots of glossopharyngeal and vagal nerves (in NF II usual). Two types of the tumour histology are distinguished, Antony type A and Antony type B. Elongated bipolar cells with unclear borders and elongated nuclei are typical for Antony type A tumours. These cells form palisade-like structures, with parallel, oriented rows of nuclei, which are alternated with noncellular areas of fibrous structure. This structure,
651
if isolated, is seen in spinal neurinomas. Reticular structure with dispersed cells having lymphocyte-like nuclei is typical for Antony type B. The cytosol as seen under optic microscopy is empty due to xanthomatosis (Matsko 1998). A combination of microscopic structural types is typical for these tumours.
7.3.1.1
Eighth Cranial Nerve Neurinoma
These tumours usually originate from the vestibular portion of the nerve; however, hearing loss is the primary symptom. Vestibular portion signs develop later. The extent of brainstem deformity and hydrocephalus determines the clinical picture as well. According to location the following three categories of eighth nerve neurinomas are distinguished: 1. Intrachannel: located within porus acousticus internus (Figs. 7.51, 7.52) 2. Intra- and extrachannel: they expand into porus acousticus internus as well as into the cerebellopontine cistern 3. Extrachannel neurinomas: they originate from the nerve portion that passes through the cerebellopontine cistern Neurinomas are benign and slowly growing tumours, and rarely undergo malignant transformation (Fig. 7.53). CT features of the eighth nerve neurinoma depend to a great degree on the size of a tumour. Neurinomas <1 cm in size are not usually identified. Even large neurinomas isodensive to brain tissue can be missed on CT without CE (Fig. 7.54). Cystic parts of a tumour are hypodensive. An important component of CT diagnosis of neurinomas is the analysis of images in the bone window regimen—most neurinomas dilate the meatus acousticus internus, which is clearly identified on CT (Figs. 7.55, 7.56). After CE, the density of neurinomas increased mildly or moderately. The structure of a tumour is better seen under these circumstances (Figs. 7.55–7.58). On MRT, neurinoma is isointensive on T1-weighted images and hypointensive on T2-weighted images. Its contour is even, and a rim of signal on the periphery (the so-called CSF fissure) is seen as well as cerebellar deformity and compression of the brainstem (Fig. 7.59). Most neurinomas of the eighth nerve follow the direction of meatus acousticus internus, and the part of the tumour located within meatus comprise its minor part. In this case, a tumour acquires a teardrop-like shape (Figs. 7.60, 7.61). Areas of heterogeneous signal changes including cysts are typical for large neurinomas (usually exceeding 3 cm in diameter) (Figs. 7.62, 7.63). All neurinomas have prominent CE, heterogeneous in of 70% cases. Multiple neurinomas, including bilateral neurinomas of the eighth cranial nerve, usually are due to neurofibromatosis and account for up to 5% of all neurinomas (Figs. 7.64, 7.65). On DWI, neurinomas are hyperintensive in relation to brain tissue and have relatively high ADC values due to wide extracellular spaces and high water content there. In most cases in perfusion studies, neurinomas give moderate heterogeneous increase of CBV and CBF parameters (Fig. 7.66).
652
Chapter 7
Fig. 7.50a–f Choroid plexus papilloma. A
large tumour with microcalcifications is seen in the fourth ventricle on CT (а). After CE (b), the tumour density became higher, and the visualisation of borders between the tumour and brain tissue improved. CT CBV perfusion map (c) shows heterogeneous increase of blood flow in the tumour tissue. On Т1-weighted imaging before (d) and after (e,f) CE, a tuberous contour of the tumour is seen with invasion of the fourth ventricle
Infratentorial Tumours
653
Fig. 7.51a–c Microneurinoma of the left eighth cranial nerve. On FIESTA sequence in axial projection (а) and on T1-weighted imaging with
CE (b,c), a small tumour with intensive accumulation of contrast medium is seen in the meatus acousticus internus
Fig. 7.52a–c Microneurinoma of the right eighth cranial nerve. On Т2-weighted imaging (а) and Т1-weighted imaging before (b) and after (c) CE, a small tumour that intensively accumulates contrast medium is seen in the meatus acousticus internus rightwards
654
Fig. 7.53a–f Malignant neurinoma of the left eighth cranial nerve (a
14-year-old patient). On Т2-weighted imaging (а) and Т1-weighted imaging (b), a tumour in the left half of the posterior fossa with marked dilatation of meatus acousticus internus is visualised. The
Fig. 7.54a–c Neurinoma of the left eighth cranial nerve. On CT without CE (а), a tumour is almost indistinguishable from the surrounding brain tissue. Displacement and deformity of the fourth
Chapter 7
tumour is encircled by dilated vessels—tortuous hypointensive areas. CE (c–e) of the tumour is prominent. MR venography (2D TOF) ascertains the location of vessels around the tumour (f)
ventricle is identified. After CE (b,c), the size and structure of the tumour is possible to determine due to intensive accumulation of contrast medium
Infratentorial Tumours
655
Fig. 7.55a–c Neurinoma of the right eight cranial nerve. CT in bone-window regimen (а) allows identification of mild asymmetrical dilatation of meatus acousticus internus rightwards. After CE (b,c), a tumour is weakly differentiated from brain tissue due to poor accumulation of contrast medium in its tissue
Fig. 7.56a–c Neurinoma of the left eighth cranial nerve. CT in the bone-window regimen (а) allows identification of mild asymmetrical dilatation of meatus acousticus internus leftwards. After CE (b,c), the tumour acquires higher density and is clearly distinguished from the brain tissue
656
Chapter 7
Fig. 7.57a–c Neurinoma of the left eighth cranial nerve. CT with CE (а,b) shows a predominantly cystic large neurinoma of the left cerebellopontine angle. CТ in the bone-window regimen (c) reveals dilatation of meatus acousticus internus leftwards
Fig. 7.58a–c Neurinoma of the right eighth cranial nerve. CT in the bone-window regimen (а) allows identification of mild asymmetrical
dilatation of meatus acousticus internus rightwards. CТ with CE (b,c) shows a predominantly solid neurinoma in the right cerebellopontine angle
Infratentorial Tumours
657
Fig. 7.59a–c Neurinoma of the left eighth cranial nerve (a 9-yearold child). On Т2-weighted imaging (а,c) and Т1-weighted imaging (b), there is a large tumour with a relatively homogenous structure in
the lateral part of the posterior fossa leftwards, causing partial dilatation of meatus acousticus internus. The tumour is clearly delineated from the brain tissue
Fig. 7.60a–c Neurinoma of the left eighth cranial nerve. On MRI,
most indistinguishable from the brain tissue. T1-weighted imaging with CE (c) shows peculiarities of the tumour shape and their relationships with the meatus acousticus internus
a tumour of the left cerebellopontine angle is seen. On T2-weighted imaging (a), the signal of the tumour is moderately hyperintensive, whereas on T1-weighted imaging (b) the tissue of neurinoma is al-
658
Fig. 7.61a–c Neurinoma of the right eighth cranial nerve. On Т2-weighted imaging (а), Т1-weighted imaging with CE (b), and Т1-weighted imaging with fat-saturation signal technique (c), tumour
Chapter 7
is seen in the left cerebellopontine angle. On T2-weighted imaging, tumour is isointensive compared with brain tissue. CE helps to determine the anatomic peculiarities of the tumour shape
Fig. 7.62a,b Neurinoma of the right eighth
cranial nerve. MRI reveals a tumour with heterogeneous structure of the right cerebellopontine angle with a cystic component. On T2-weighted imaging (а), the right meatus acousticus internus is prominently dilated, and tumour is seen in its lumen. The cyst looks dark compared with the brain tissue on Т1-weighted imaging (b)
Infratentorial Tumours
659
Fig. 7.63a–c Neurinoma of the left eighth cranial nerve. There is a tumour node with a small arachnoid cyst on periphery in the lateral parts
of the posterior fossa leftwards. On Т2-weighted imaging (а) and Т1-weighted imaging (b), the tumour has heterogeneous signal. After CE (c), the tumour intensively accumulates contrast medium
Fig. 7.64a,b Bilateral neurinomas.
Т2-weighted imaging (а) and Т1weighted imaging (b) visualises bilateral neurinomas of the eighth cranial nerve. Small cysts in the tumour stroma are better seen on Т2-weighted imaging (hyperintensive signal)
660
Chapter 7
Fig. 7.65a–d von Recklinghausen’s disease (a 14-year-old patient). Bilateral neurinomas of
the eighth cranial nerve. On MRI before (а,b) and after (c,d) CE, large bilateral tumours of the vestibulocochlear nerves are seen. The meatus acousticus internus is dilated bilaterally. The brainstem is compressed. Tumours intensively accumulate contrast medium. Additionally, a meningioma is seen in the left sinus cavernosus
Fig. 7.66a–c Neurinoma of the left eighth cranial nerve. On CT (а) with CE, a round tumour in the left cerebellopontine angle is seen. CT
perfusion maps: CBV (b) and CBF (c) shows moderately increased blood supply in the tumour with heterogeneous structure
Infratentorial Tumours
7.3.1.2
Neurinomas of the Fifth Cranial Nerve
According to Burdenko Neurosurgical Institute classification, the following types of neurinomas of the fifth cranial nerve are distinguished: • Gasserian ganglion neurinoma, located often extradurally, and in the posterior cranial fossa, with dumbbell-shaped formation • Neurinomas of the fifth cranial nerve root, located infratentorially (often intradurally) • Neurinomas of the first branch of the fifth cranial nerve, which located the middle cerebral fossa, and often grow through the superior orbital fissure into the orbit Trigeminal nerve neurinomas are characterised by different clinical manifestations according to the site of origin. Gasserian ganglion neurinomas cause pain, paraesthesia, weakness of masticator muscles, and usually have a typical dumbbell-shaped appearance (Figs. 7.67, 7.68). As a rule, imaging features of trigeminal neurinomas are analogous to that of neurinomas of the eighth nerve. Involvement of the first branch of the trigeminal nerve causes diplopia and exophthalmos (Fig. 7.69). Trigeminal neurinomas originated distally to Gasserian ganglion are located in the posterior cranial fossa and cause ataxia and involvement of the facial and the vestibulocochlear nerves (Fig. 7.70). Atypical neuralgias, bulbar cranial nerves involvement, pyramidal signs, and raised intracranial pressure are seen in 40% of patients. In these cases, neurinomas should be differentiated from primary tumours of the skull base. The facial nerve neurinomas are very rare and cause palsy irrespective of site of origin along a nerve. Neurinomas of other cranial nerves are exceptionally rare (Gentry et al. 1991) (Fig. 7.71, 7.72). Our experience shows that MRI exceeds CT in diagnosis of neurinomas, especially of giant trigeminal neurinomas, and in assessment of their relationship with intracranial structures (Fig. 7.73).
661
7.3.2 Meningiomas Meningiomas are the most frequent infratentorial tumours of the cerebellopontine angle, after neurinomas. They make up 5% of all intracranial tumours (Beutow et al. 1991). As it is seen in neurinomas, the average age of patients with meningiomas is 45–55 years. This tumour often is found in patients with NF II. On routine CT, a tumour usually has isodensive or mildly hypodensive characteristics similar to that of the adjacent brain tissue and is poorly delineated from the it (Fig. 7.74). As a rule, calcified meningiomas (psammomatous type) are exception (Fig. 7.75). After CE, meningiomas become hyperdensive. A typical feature of this kind of tumour is a wide attachment of a tumour to the medial surface of pyramid of the temporal bone and clivus (Fig. 7.76). On Т1-weighted imaging, most meningiomas (60%) are isointensive to brain tissue and are situated in the lateral parts of posterior fossa. In the rest of cases, meningiomas have hypointensive MR signal. On T2-weighted imaging, the tumour’s signal may be variable—hypointensive, more inherent in psammomatous meningiomas (Fig. 7.77), or moderately hyperintensive, inherent in meningotheliomatous meningiomas (Fig. 7.78). Calcified areas of the tumour in contrast to CT may not be visualised. If large tumours of the cerebellopontine angle or of craniovertebral junction are present, then compression of the spinal cord may occur, and a clear border between a tumour and the compressed brainstem is seen on standard scanning regimens. On T2-weighted imaging with high resolution, vascular matrix of a tumour is detected in most cases, and in several cases (as in supratentorial meningiomas), cysts adjacent to a tumour may be identified (Figs. 7.79, 7.80). After CE, the intensity of tumour tissue increases to 60– 100%, and application of vascular MR programs ascertains the tumour size in its relation to arteries and veins of the skull base (Fig. 7.81). More than in half of cases, CE of meninges is identified on the tumours periphery (“tail ring”), which is a criterion for differential diagnosis from neurinomas. How-
Fig. 7.67a,b Neurinoma of the left fifth
cranial nerve. On Т2-weighted imaging (а) and Т1-weighted imaging (b) in the medial parts of the middle cranial fossa, the tumour is revealed, with relatively a homogenous structure
662
Chapter 7
Fig. 7.68a–c Neurinoma of the left fifth cranial nerve. Case 1. CТ with CE (а) shows a dumbbell-shaped tumour that expands along the right
fifth nerve root. Cases 2 and 3. MRI with CE (b,c) reveals a shape and distribution characteristic to neurinomas of the fifth cranial nerve
Fig. 7.69a–d Neurinoma of the left fifth cranial nerve. On Т2-weighted imaging (а) and
Т1-weighted imaging (b), the tumour is revealed, which is situated in the middle cranial fossa and is expanding along the first branch of the fifth cranial nerve into the left orbit. CE (c,d) is prominent and delineates the tumour well
Infratentorial Tumours
663 Fig. 7.70a,b Neurinoma of the left fifth
cranial nerve. On Т2-weighted imaging (а) and Т1-weighted imaging (b), a large tumour is revealed, which is located supra- and infratentorially. Small cysts in the tumour stroma are better seen on Т2-weighted imaging
Fig. 7.71a–c Neurinoma of the seventh cranial nerve. CT before (а) and after (b,c) CE
664
Chapter 7
Fig. 7.72a–f Neurinoma of the tenth cranial nerve. On Т2-weighted imaging (a,c) and Т1-weighted imaging (b), a tumour is identified near
the foramen jugulare. Partial invasion of the tumour into the foramen is seen. CE (d–f) ascertains the tumour location and its relationship with skull base structures
Fig. 7.73a–c Neurinoma of the right fifth cranial nerve. MRI (a–c) visualises a tumour with wide spread, which affects medial parts of the middle cranial fossa rightwards and the pyramid of temporal bone. The brainstem is compressed and displaced leftwards. The lateral ventricles are dilated
Infratentorial Tumours
665
Fig. 7.74a–c Meningioma of the right cerebellopontine angle and the petroclival region. CT before (а) and after (b,c) CE demonstrate a
tumour with homogeneous structure, which is widely attached to the medial surface of pyramid of the right temporal bone and partially involving the clivus
Fig. 7.75a–e Calcified meningiomas of the posterior fossa. Case 1. On CT before (а) and after (b) CE, a predominantly calcified tumour attached to the occipital bone leftwards is revealed. The soft part of meningioma is seen only after CE. CT in the bone-window regimen (c) shows heterogeneity of calcified components of meningioma. Case 2. CT image with CE shows the large tumour placed in right cerebellopontine angle. On 3D CT reconstruction (e), the relationship between meningioma and basilar artery is well seen
666
Chapter 7
Fig. 7.76a–c Variants of location of infratentorial meningiomas: а Tumour on the surface of the occipital bone, b in the cerebellopontine angle, and c in the petroclival region Fig. 7.77a,b Meningioma. On Т2-weighted
imaging (a) and Т1-weighted imaging (b), a large tumour is revealed in the lateral part of the posterior fossa. The tumour is almost isointensive to brain tissue. The cerebellar hemisphere, brainstem, and the fourth ventricle are displaced rightwards
Fig. 7.78a,b Meningioma of the right
petroclival region. On Т2-weighted imaging (а) and Т2-weighted imaging (b), a tumour with heterogeneous structure is identified. It is widely attached to the medial surface of pyramid of the right temporal bone and clivus. The border between the tumour and the brain tissue is clear. A vascular net of the tumour is identified on T2-weighted imaging
Infratentorial Tumours
667 Fig. 7.79a,b Meningioma of the right cer-
ebellopontine angle. Т2-weighted imaging (а) shows a solid tumour with clear contour that displaces brain structures contralaterally with dilatation of CSF spaces laterally to the tumour. There are no signs of tumour invasion into meatus acousticus internus on the coronal scan (b)
Fig. 7.80a–c Meningioma of the right cerebellopontine angle. On axial Т2-weighted imaging (а) and Т1-weighted imaging (b), a tumour is seen that is widely attached to the medial surface of pyramid of the right temporal bone. The tumour does not invade into the
meatus acousticus internus. A “CSF fissure” sign between the tumour and the brain tissue is seen. On CT (c), the tumour is hyperdensive; however, the borders between the tumour and the brain tissue are not so clearly seen as on MRI
668
Chapter 7
Fig. 7.81a–d Meningioma of the right petroclival region. On axial (а) and sagittal (b)
MRI, a tumour with homogeneous structure is seen with large vessels in its stroma. The tumour compresses brainstem and displaces it backwards. On Т1-weighted imaging after CE (c), the tumour intensively accumulates contrast medium. MRA (d) ascertains the relationship between the tumour and large veins of the brain base
Fig. 7.82a–c Meningioma of the right cerebellopontine angle. On Т2-weighted imaging (а) and Т1-weighted imaging (b), a large tumour in the lateral parts of the posterior fossa is seen. The tumour has heterogeneous structure with foci of cystic degeneration in the
medial part. The brainstem and the fourth ventricle are displaced leftwards. The tumour expands into meatus acousticus internus. After CE (c), the tumour intensively accumulates contrast medium
Infratentorial Tumours
ever, it should be remembered that intrusion of a inner tissue into the meatus acousticus internus may be seen in cases with large meningiomas, which makes differential diagnosis more complicated (Zee et al. 1992) (Fig. 7.82). On DWI, meningiomas have a heterogeneous MR signal and ADC that differs between benign, atypical, and anaplastic forms of the tumour (ADC values: 0.83 ± 0.11, 0.91 ± 0.16, and 0.97 ± 0.19, respectively). As a whole, MR signal on DWI is higher in meningiomas than in vestibulocochlear neurinomas. This may help to differentiate tumours according to their histology. Spectroscopic features of infratentorial and supratentorial meningiomas are identical according to our data (Figs. 7.83, 7.84). On perfusion-weighted CT imaging, three types of haemodynamical patterns of meningiomas can be distinguished, which correlate with the results of digital cerebral angiography (DSA):
Fig. 7.83a–f Meningioma of the right cerebellopontine angle. On Т2-weighted imaging (а) and Т1-weighted imaging (b), a large tumour is seen in the lateral part of the posterior fossa. The tumour has a homogenous structure and well-defined matrix located near the meatus acousticus internus. The brainstem and the fourth ventricle are displaced leftwards. The tumour does not spread into the meatus
669
• Type I: low CBV (2.5–5 ml/100 g) and CBF (25–30 ml/100 g/
min) values, tumour vascular net is absent or minimal on DSA • Type II: moderate elevation of CBV and CBF (up to 10– 11 ml/100 g and 70–80 ml/100 g/min, respectively) values, moderate vascular patch in the capillary phase in DSA • Type III: prominent increase of a meningioma haemodynamical parameters (CBV: 21–24 ml/100 g, CBF: 110– 125 ml/100 g/min), highly vascularised pattern of the tumour on DSA (Fig. 7.85) The most typical neuroimaging features of the eighth nerve neurinomas and meningiomas of the cerebellopontine angle are listed in Table 7.2.
acousticus internus. A sign of the CSF fissure is seen. On DWI with b = 500 (c) and b = 1000 (d), meningioma has a mildly hyperintensive MR signal compared with brain tissue. On DSA, the blood supply of the tumour is seen proceeding from the external carotid artery branches (е,f)
670
Chapter 7
Fig. 7.84a–f Case 1. Clivus meningioma. On Т1-weighted imaging
with CE (a,b), a tumour of irregular shape situated paramedullary and rightwards is seen. On DWI (c), the signal of meningioma does not differ from that of brain tissue. Case 2. Meningioma of the inferior part of pyramid of the left temporal bone. Т1-weighted imaging
with CE (d) shows a large meningioma with homogeneous structure. On DWI (e), MR signal of meningioma is identical to that of brain tissue. On MRS (f), the NAA peak does not differ from the Glx peak, high Cho peak is seen, and there is an alanine (Ala) peak
Table 7.2 CT and MRI features that differentiate infratentorial neurinomas and meningiomas Features
Neurinoma
Meningioma
Involvement of meatus acousticus internus
85%
Rare
Bone reaction
Rare
Osteolysis or hyperostosis
CT without CE
Hypodensive, isodensive
Isodensive, moderately hyperdensive
Calcifications
Rare
20%
Cysts/necrosis
Up to 30%
Rare
Haemorrhage
Rare
Rare
CE
Heterogeneous in 40% of cases, intensive
Homogeneous, intensive
Angle between a tumour and dura mater
Sharp
Obtuse
Dural tail (thickening of adjacent dura mater) Absent
Often (up to 50%)
MR signal on DWI
Isointensive
Hyperintensive
ADC
1.5–2.1 ± 0.15
0.83–0.97 ± 0.15
Perfusion
Moderately elevated
High
Infratentorial Tumours
Fig. 7.85a–f Perfusion patterns of posterior fossa meningiomas.
Case 1. CE CT (a) and CT perfusion (b) map (CBV) demonstrate a large tumour in the left cerebellopontine angle. Mild CE and slightly increased blood volume are found in tumour tissue. DSA in capillary phase shows displacement of the vessels. There is no tumour vascular
671
net Type Ι. Case 2. Petroclival meningioma. CT image with CE (d) and CBV perfusion map (e), and DSA (f) in the late arterial phase are demonstrate a lesion with high value of blood volume parameters and abundant vascular net Type ΙΙΙ
672
Chapter 7
7.3.3 Epidermoid Cysts (Cholesteatomas) Epidermoid cysts (EC) compose 0.2–1.8% of all intracranial tumours. They manifest in the elderly. Most EC are intradural and located on the skull base aside from median line. In 40–50% of cases, EC are located within the cerebellopontine angle, and they rank in third place after neurinomas and meningiomas among the cerebellopontine angle tumours. Congenital EC originate from fragments of ectodermal epithelial elements that remain within the cavity of closing neural tube when secondary brain vesicles are formed; acquired EC have traumatic origin, when epidermis is intruded into deeper lying tissues, where it forms a cyst lined with desquamated epithelium and gradual keratin accumulation occurs within their cavity. Intracranial EC are cystic mass lesions within the basal brain cisterns. In large part, they have tuberous surfaces and
lobular structures with a creamy content consisting of keratohyaline. EC tend to grow around cerebral vessels and cranial nerves. On microscopy, their walls are lined with multilayer desquamating keratinising epithelium, whereas their cavity contains a keratin-like content of crystals of cholesterol. In contrast to dermoid cysts, EC do not contain dermal germs such as hair follicles and sebaceous glands. In most cases on CT, EC appear as hypodensive (–30 HU) and nonenhancing lobular mass lesions (Figs. 7.86, 7.87). Calcifications within the cyst walls are seen in 10–25% of cases. Rarely are EC encountered that have density higher than that of the CSF, probably due to thickening of cyst content, old haemorrhages, and high protein content (Fig. 7.88). On MRI, EC look like mass lesions located in the basal cisterns inside which they expand. In typical cases, EC have prolonged Т1 and Т2 relaxation times, close to those of the CSF (Fig. 7.89). This is why EC are less clearly visualised within
Fig. 7.86a–d Cholesteatoma of the left pertoclival region. CT (а) image shows a hy-
podensive area in cerebellopontine angle without accumulation of contrast medium. On Т2-weighted imaging (b) and Т1-weighted imaging (c, d), a tumour is revealed, located in the anterior pontine cistern, and the cerebellopontine cistern leftwards. The brainstem is compressed. The tumour margins intermingle with the signal of the CSF in the brain base cisterns. The basilar artery is partially encircled by cholesteatoma
Infratentorial Tumours
673
Fig. 7.87a–c Cholesteatomas. Case 1. On CТ (а), a hypodensive area with thinning of the adjacent occipital bone is seen in the lateral parts
of the posterior fossa. Case 2. The basally located cholesteatoma expanding on the posterior fossa. CТ before (b) and after (c) CE shows a hypodensive tumour displacing brainstem backwards
Fig. 7.88a–f Cholesteatoma of the pyramid of the left temporal bone.
On postcontrast CT (а) in axial and coronal (b) planes, and on CT in the bone-window regimen (c), an area of bone destruction is seen in the pyramid of the left temporal bone; the density of tumour is iden-
tical to that of brain tissue. No CE is seen. On Т2-weighted imaging (d), a tumour is hyperintensive. On Т1-weighted imaging before (e) and after CE (f), a tumour has isointensive MR signal
674
Fig. 7.89a–c Cholesteatoma. On Т2-weighted imaging (а) and
Т2-weighted imaging (b), there is a tumour in the right petroclival region, which has relatively homogenous hyperintensive on Т1-weighted imaging and hypointensive signal to that of brain tissue
basal cisterns. Sometimes a cyst wall is hardly seen. Some EC are hyperintensive on T1-weighted imaging, due to high lipid content, which is confirmed by MRS, whereas EC isointensive to the CSF have low lipid content. As on CT, on MRI there is no CE inside the cyst (Gao et al. 1992) (Fig. 7.90). DWI is a new approach in EC neuroimaging (Tsuruda et al. 1990). On DWI, EC look markedly hyperintensive and are clearly delineated from the CSF spaces and brain tissue (Figs. 7.90, 7.92). DWI is informative in the follow-up assessment of EC in a delayed postoperative period.
7.3.4 Теratoma Teratomas are rare dysembryonic tumours found in the posterior portions of the third ventricle and the pineal region, where they are encountered in 15% of all tumours of that location in children in any age. They are rarely found infratentorially (Meyers et al. 2006). Teratomas may be mature or malignant. Mature teratomas consist of differentiated tissues (epithelium, cartilage, smooth muscles, etc.), located as organoids, for instance, in the shape of cysts lined with flat or other types of epithelium. Malignant forms are represented by tissues derived from any of the dermal layers. Diagnosis is based on complex neuroimaging using CT and MRI, on which tumours appear in a variable way, reflecting many tumour constituents. Cartilaginous and calcified fragments are hyperdensive on CT and hypointensive on MRI (especially on T2-weighted imaging). Conversely, lipid inclusions are hypodensive on CT and hyperintensive on T1-weighted
Chapter 7
on Т1-weighted imaging. The external margin of a tumour is festoon shaped. The brainstem is displaced, and the basilar artery is included in the tumour mass. Sagittal projection outlines the spread of the tumour (c)
imaging (Fig. 7.93). Cysts are a typical feature of teratomas. Large teratomas may cause hydrocephalus.
7.3.5 Tumours of the Jugular Glomus Tumours of jugular glomus are rare and related to the group of neuroendocrine tumours and paragangliomas. More frequently, they grow on the skull base and into the cranial cavity, originating from neural ganglia located along the carotid artery, from vagal ganglia, or a neural plexus situated around the sigmoid sinus and the jugular vein. These tumours are well vascularised (Figs. 7.94, 7.95). Neoplasms of jugular glomus are the most frequent tumours among all locations of paragangliomas. They originate near the middle ear, destroy bones of the pyramid of the temporal bone, intervene with the mastoid process, and grow extracranially into the cervical soft tissues. Intracranially, paragangliomas grow through the jugular foramen and surround bulbar cranial nerves and venous sinuses. A soft tissue mass lesion is well identified on MRI, whereas CT is preferable to obtain information about the extent of destruction of the bones (Fig. 7.96). On MRI, tumours have heterogeneous signal, with patchy appearance due to good vascularisation with different calibre of vessels, multidirectional blood flow, and partial thrombosis (Fig. 7.97). MRI also ascertains the extent of intracranial growth, the extent of brainstem deformity, and relationship between a tumour and cerebral arteries, in particular, the venous sinuses (Gerosa et al. 2006) (Fig. 7.98). However, DSA remains the main technique to assess full features of the tumour blood supply.
Infratentorial Tumours
675
Fig. 7.90a–c Cholesteatoma of the right cerebellopontine angle. On Т2-weighted imaging (а) and Т1-weighted imaging (b), there is a tumour hyperintensive on Т2-weighted imaging and hypointensive to brain tissue on Т1-weighted imaging. The tumour has an irregular external contour. On DWI (c), the cyst has a typically high signal
Fig. 7.91a–f Cholesteatoma of the right cerebellopontine angle. MRI
on Т2-weighted imaging (а,b), Т1-weighted imaging (c), and FLAIR (d). A tumour is revealed hyperintensive on Т2-weighted imaging and hypointensive to brain tissue on Т1-weighted imaging. On FLAIR
images, the tumour has a heterogeneous structure. The external margin of a tumour is festoon shaped and encompasses the basilar artery. On DWI (e,f), cholesteatoma has a typically high signal
676
Fig. 7.92a–d Cholesteatoma of the petroclival region. On Т2-weighted imaging (а) and Т1-weighted imaging
before (b) and after (c) CE, a mass lesion is seen on the ventral surface of the brainstem, displacing the latter backwards. The cyst is hyperintensive on Т2-weighted imaging and hypointensive to brain tissue on Т1-weighted imaging. CE is absent. On DWI (d), cholesteatoma has a typically high signal
Chapter 7
Infratentorial Tumours
677
Fig. 7.93a–h Teratoma of the posterior fossa (a 7-year-old child). On CT without CE, there is a large cystic mass lesion in the posterior fossa with many large calcifications spreading in cavity of the fourth ventricle (а–c). Т1-weighted imaging (d–f), Т2-weighted imaging (g), and DWI (h) also shows a predominantly cystic mass lesion compressing brainstem and invading the vertebral canal. On MRI, calcifications are less clearly seen than on CT
678
Chapter 7 Fig. 7.94a,b Paraganglioma. On angiogra-
phy (а), abundant blood supply of the skull base tumour is seen. Ascending venography (b) shows that the tumour occludes the internal jugular vein
Fig. 7.95a–f Paraganglioma (a 9-year-old child). On CT (а,b), destruction of the pyramid of temporal bone and the mastoid process is seen with soft tissue containing a tumour component. On Т2weighted imaging (c) and Т1-weighted imaging before (d) and after
(e) CE, tumour masses are seen in the base of the pyramid of the left temporal bone that intensively accumulate contrast medium. Abundant blood supply is seen on angiography (f)
Infratentorial Tumours
679 Fig. 7.96a,b Paraganglioma. On CE CT in
the axial (а) and the coronal (b) planes, a skull base tumour is seen rightwards, with homogenous density and with signs of bone destruction
Fig. 7.97a–f Paraganglioma. On Т1-weighted imaging with CE (а–c), a tumour that intensively accumulates contrast medium is seen in the pyramid of temporal bone and the mastoid process. On MRA (d–f), branches of the external carotid artery supplying the tumour node with blood are seen
680
Chapter 7
Fig. 7.98a–f Paraganglioma. Т2-weighted imaging (а) and Т1weighted imaging (b) shows a large tumour seen in the pyramid of the temporal bone and cerebellopontine angle of the right. A tumour
cyst is situated backwards. After CE (c–f), a tumour is seen that intensively accumulates contrast medium and is expanding along the jugular foramen intracranially
7.3.6 Chordomas
ty than normal bone does. However, both CT and MRI are required to assess involvement of the sphenoid bone and to assess relationships between the tumour and adjacent structures. In typical cases, chordomas have an intracranial component growing caudally with subsequent brainstem deformity, and an extracranial fragment that narrows the air column of nasopharynx with formation of separate paravertebral spurs (Fig. 7.103). The described location and growth pattern are main differential diagnostic criteria that distinguish chordomas from other tumours.
Chordomas are rare tumours, composing not more than 2% of primary tumours of the CNS in adults. In children, a few cases worldwide have been diagnosed. Chordomas originate from the polypotent tissue of chordomesodermal origin. The clivus and the body of occipital bone are the most frequent sites of origin, and these tumours may penetrate the nasopharynx or destroy the atlanto-occipital joint. Chordomas are located medially and extradurally; they grow laterally and destroy the pyramid of the temporal lobe passing beside the cerebellopontine angle. Chordomas often reach large size; they have smooth tuberous shape and soft elastic consistence (Al. Mefty and Borbe 1997). On CT, an area of expanded bone destruction in the skull base is seen within the site of origin of the tumour (Fig. 7.99). CE of a lesion is heterogeneous and is insufficient to ascertain the intracranial topography of chordomas. On T1-weighted imaging, chordomas may have variable signal (from hypoto hyperintensive). On T2-weighted imaging, chordomas are usually characterised by hyperintensive MR signal, but the extent of hyperintensity widely varies (Figs. 7.100, 7.101). Intensive CE is not typical for chordomas; it is often moderate but heterogeneous (Fig. 7.102). On sagittal and axial T1-weighted images, it is better seen how the body of sphenoidal bone is involved. When tumour infiltrates the bone, the latter acquires lower signal intensi-
7.4
Brainstem Lesions
7.4.1 Brainstem Tumours Brainstem gliomas account for 15–20% of all primary brain tumours and 20–30% of all infratentorial tumours in children (Konovalov et al. 1993; Rubin et al. 1998). The peak of incidence is between 5 and 6 years of age. According to the Burdenko Neurosurgical Institute’s data, children younger than 15 years represented 70% of patients operated on for brainstem tumours. Clinical manifestations largely depend on the site of origin and distribution along the longitudinal and transverse brainstem axis. It is thought that gliomas are more frequently seen in the pons (40–60%) than tumours that affect the medulla (20–25%) and midbrain (15–20%). Two adjacent
Infratentorial Tumours
Fig. 7.99a–g Chordoma of the skull base. On CТ (а,b) a tumour is seen causing wide destruction of the skull base, with a large intracranial component. Sagittal CT reformation (c) and 3D CT reconstruction (d) give additional information about the volume of tumour mass and the square of bone-destruction area. On Т2-weighted
681
imaging (e) and Т1-weighted imaging (f) with CE, a tumour of heterogeneous structures that intensively accumulates contrast medium and causes prominent brainstem dislocation is found. On sagittal MRA (g), a bow-shaped, backward displacement of the basilar artery is seen
682
Chapter 7
Fig. 7.100a–e Chordoma of the skull base
(a 4-year-old child). On Т2-weighted imaging (а–c) and Т1-weighted imaging (d,e), a large tumour of the inferior clivus is seen with intra- and extracranial expansion. The tumour hyperintensive on Т2-weighted imaging and hypointensive to brain tissue on Т1-weighted imaging. The brainstem is compressed by the tumour
Infratentorial Tumours
Fig. 7.101a–f Chordoma of the skull base. On Т2-weighted imaging (а–d) and Т1-weighted imaging (е,f), a large tumour of the inferior clivus is seen with intra- and extracranial expansion. The tumour hyperintensive on Т2-weighted imaging, with intratumoural septi,
683
is seen. It is hypointensive to brain tissue on Т1-weighted imaging. Microhaemorrhages are visualised (hyperintensive on T1-weighted imaging)
684
Fig. 7.102a–d Chordoma. On axial (a) and sagittal (b) Т2-weighted imaging, large and widely spread tumour destroying the inferior clivus and skull base is seen. The tumour has a large extracranial component in the projection of the naso-oropharynx. The tumour is hyperintensive on Т2-weighted imaging, with many connective tissue septi inside. On T1-weighted imaging (c), the tumour tissue is mildly hypointensive to brain tissue. CE (d) is prominent, but heterogeneous
Chapter 7
Infratentorial Tumours
685
Fig. 7.103a–f Chordoma of the skull base (a 5-year-old child). Sagittal CT reformation (а) reveals a tumour of the inferior clivus, with bone destruction and expansion into nasopharynx. On Т1-weighted imaging (b,c) and Т2-weighted imaging (d–f), the distribution of tumour and the extent of brain tissue compression are outlined
686
Chapter 7
brainstem levels are frequently affected. Prognosis is variable; however, it is unfavourable in general, as it depends on the extent of brainstem involvement as well as on tumour histology (Guillamo et al. 2001). Most of patients treated surgically at the Institute have gliomas; more frequent are the astrocytomas of different grade of malignancy (Konovalov et al. 1993, 2001a). Benign diffusive astrocytomas are found in 50–55% of cases. PA are rarely found. Malignant types of astrocytomas—AnA and GB—are diagnosed in 15–30% of cases. Gangliogliomas, medulloblastomas, EP, EC, HMG, and others neoplasms of the brainstem are rarely observed. The Institute’s classification of brainstem tumours subdivided them into three major types: • Expansively growing (nodular type) • Diffusely growing • Pseudonodular, infiltrating tumour Expansively growing tumours. These tumours are well delineated from adjacent brain tissue, which is revealed on macroand microscopy. The tumour is usually separated from the
brainstem structures by a peculiar glial capsule, appearing as intermingling processes of affected astrocytes, which tend to be grouped more compactly in those areas of the tumour that border brain tissue. Neural elements are compressed and dislocated. Frequently, both cystic and solid components are present. More frequently, there are PA and less often, bi-dermal benign angioastrocytomas. CT reveals a well-delimited area of CE, which may be intrabrainstem or exophytic. Nodular forms of brainstem tumours are characterised by well-defined contours and by a combination of solid and cystic tumour’s components. Exophytic components may grow into the fourth ventricle, cisterna magna, the anterior and lateral parts of pons, and the interpeduncular cistern (Figs. 7.104, 7.105). Nodular brainstem tumours are characterised by well-defined contours and intensive accumulation of contrast medium on CT and MRI (Fig. 7.106). Diffusely growing tumours make up to 80% of all brainstem gliomas. The margins between brain tissue and the tumour are absent on macro- as well as on microscopy. The cellular elements of neural tissue persist among tumour cells, with disintegration and partial destruction of the brain tissue
Fig. 7.104a– d PA of the pons. On Т2-weighted imaging (а) and Т1-weighted imaging (b–d), a tumour
of heterogeneous structure with a large cyst is seen in the right half of pons
Infratentorial Tumours
687
Fig. 7.105a–f PA of the superior part of the brainstem (an 11-year-old child). On CT with CE (а,b), a tumour of heterogeneous structure of
the right thalamus and the right cerebral peduncle. On Т2-weighted imaging (c) and Т1-weighted imaging (d), a tumour with cystic component is seen. CE (e,f) ascertains the distribution of the tumour
Fig. 7.106a,b PA of the left half of the pons (a 9-year-old child). On Т1-weighted imaging (а) before and after (b) CE, a tumour of heterogeneous structure and a solid node that intensively accumulates contrast medium is revealed. Large cysts encircle the tumour in the fourth ventricle and the left pontocerebellar cistern
688
Chapter 7
in the site of tumour. Largely, the brainstem is deformed and enlarged. Histologically, there are astrocytic gliomas of various extents of malignancy (fibrillary protoplasmatic A, anaplastic A, and GB). Distribution of the tumour process with involvement of two levels of brainstem and its whole length with involvement of basal ganglia and cerebellar hemispheres are important tumour characteristics (Fig. 7.107). However, the latter is rarely seen. Fibrillary astrocytomas (FA) grow diffusely in the brainstem, causing its enlargement. The tumour affecting the medulla may involve the superior parties of the spinal cord. On CT, the tumour frequently looks like a hyperdensive mass and does not show CE (Fig. 7.108). If the changes of density are absent and there is no brainstem deformity, then diagnosis by CT is difficult. Hydrocephalus is rarely seen in contrast to other infratentorial tumours. In some cases when a tumour has infiltrative growth, there are areas revealed in which compact growth predominates, with a relatively clear border with
brain tissue, and causes as compression of intact structures. In some cases, there are cysts within a tumour, which appear as hypodensive, round formations on CT images. On MRI, the affected structures are iso- or hypointensive on T1-weighted images and homogenously hyperintensive on T2-weighted images (Barkovich et al. 1990). Tumour borders are well delineated. The entire transverse section of brainstem may be affected, or the process may tend to be more unilateral (Figs. 7.109, 7.110). Exophytic growth into the lateral cistern or the fourth ventricle may be seen. As mentioned above, tumours may contain cysts of various sizes, up to complete cystic transformation (Fig. 7.111). CE varies from absent to prominent, but usually partial accumulation of contrast media is observed (Fig. 7.112). AnA are frequently located in pons, causing its asymmetrical enlargement. A tumour may grow onto the brainstem surface, forming exophytic tumours laterally, anteriorly, or inside the fourth ventricle. Heterogeneous density (on CT) and intensity (on MRI), respectively, are typical for this type of tu-
Fig. 7.107a–d FA of the brainstem. CT (a) shows a hypodensive area of the pons and the medial parts of the cerebellar hemispheres. On Т2-weighted imaging (b,c) and Т1-weighted imaging (d), a diffuse tumour growth is seen in the basal ganglia bilaterally with involvement of midbrain, pons, and the left cerebellar hemisphere
Infratentorial Tumours
689 Fig. 7.108 FA of the brainstem. On CT, a mildly hypointensive area in the central part of pons is seen, without clear borders. The bottom of fossa rhomboidea is evaginated, and the flattened fourth ventricle is displaced backwards
Fig. 7.109a–c FA of the brainstem (a 7-year-old child). On CT (а), the tumour of heterogeneous structure with many calcifications is seen in the left part of pons. Т2-weighted imaging (b) and Т1-
weighted imaging (c) shows a large tumour of pons that expands onto the left cerebellar hemisphere. The basilar artery is included into the tumour stroma
690
Chapter 7
Fig. 7.110a–c FA of the brainstem (a 6-year-old child). On Т2-weighted imaging (а) and Т1-weighted imaging (b,c), abnormal MR signal and thickening of brainstem are seen in the projection of pons and medulla oblongata
Fig. 7.111a–d FA of the brainstem (a 7-year-old child). On CT (а), a solid node that intensively accumulates contrast medium is seen on the background of a large intrabrainstem cyst. Т2-weighted imaging (b) and Т1-weighted imaging (c,d), clearly visualises the intrabrainstem location of the tumour
Infratentorial Tumours
691
Fig. 7.112a–c FA of the brainstem (a 14-year-old patient). Т1-weighted imaging before (а,b) and after (c) CE reveals a tumour of medulla oblongata. CE is observed only in the central parts of pons
mours (Figs. 7.113, 7.114). CE is seen more frequently in these tumours than in benign forms and usually is heterogeneous and focal (Fig. 7.115). Glioblastoma (GB) is characterised by prominent longitudinal and transverse growth. On histology, brain tissue remains as a few strands within a tumour. On CT and MRI, heterogeneous and ring-shaped CE is seen, with necrotic cavities located centrally (Figs. 7.116–7.118). It should be remembered that borders of CE do not reflect true sizes and distribution of brainstem involvement. MR signal changes especially on T2weighted imaging may extend onto the nonenhancing portions of brainstem too. These areas may represent infiltration, oedema, or both. Diffusely growing tumours are frequently inoperable. The average survival rate is 2 years. Pseudonodular, infiltrative tumours are the least frequent among brainstem tumours. Macroscopically, they have a clear border with brain tissue. However, on microscopy, infiltrative growth is revealed, with destruction of brain tissue. These tumours are usually malignant primitive neuroepithelial tumours (PNET). On CT, a hypodensive or isodensive lesion is identified, or signal changes are combined, and calcifications and cysts may be seen. CE is seen in a third of cases of CT and MRI studies, often multifocal; homogenous CE may also be seen (Fig. 7.119). High frequency of implantation metastases along the subarachnoid spaces and the ventricular walls is typical for PNET. According to the modern concept, the management plan in patients with brainstem tumours is based on complex assessment of such parameters as topography, type of growth, histology if available, and presence of cystic and exophytic components. Most neurosurgeons believe that not more than 20% of all brainstem tumours are operable (Kоnovalov et al. 2001; Daglioglu et al. 2003). Precise assessment of a brainstem tu-
mour may be obtained only after a complex of neuroimaging studies (CT and MRI are mandatory). The most informative is MRI with CE. MRI is more sensitive due to facilities such as manipulation with pulse sequences and CE peculiarities. MRI exceeds CT in identification of the tumour itself and the extent of infiltration of brainstem and types of involvement. In small brainstem tumours, MRI is the only way to identify them, and CT is uninformative. This is typical for tumours of the quadrigeminal lamina (Figs. 7.120, 7.121) and some other intrabrainstem tumours. MRI is feasible in all cases of CSF pathway occlusion at the level of the aqueduct of Sylvius or the foramen of Magendie. With CT and MRI, there are several types of tumour topography seen: craniospinal (10%; Fig. 7.122), medulla oblongata (9%), medulla oblongata and pons (15%), pons (20%), (pons and midbrain (20%), midbrain (12%), and quadrigeminal lamina (14%). It is important to ascertain the distribution of the exophytic component of a tumour. We usually observed it within the lumen of the fourth ventricle (32%; Fig. 7.123), less frequently in one of the brainstem cisterns (the lateral [10%] or the ambient cisterns [11%]). If an exophytic component was absent, then an endophytic tumour was diagnosed. Besides those in the brainstem, types of primary tumours or metastases, such as ganglioastrocytomas, astroblastomas, angioreticulomas, melanoma metastases, etc., may be seen rare. Ganglioastrocytomas (GА). On CT a well-delineated solid tumour or a cyst with a primary mural nodulus are identified. It is iso- or hypodensive, and calcifications may be seen. In most cases, CE is observed, but there are exceptions. On T1-weighted imaging, a hypointensive, and on T2-weighted imaging, a hyperintensive signal, are revealed. The extent of CE may vary from absence to prominent, and the type of CE varies too: ring shaped, heterogeneous, or homogenous (Fig. 7.124).
692
Fig. 7.113a–c AnA of the brainstem (a 15-year-old patient). On T2weighted imaging (а), a tumour of heterogeneous structure is seen with an exophytic component. A tumour encircles the basilar artery.
Chapter 7
On Т1-weighted imaging (b,c), hyperintensive foci are revealed in the tumour stroma (haemorrhages within a tumour)
Fig. 7.114a,b AA of the brainstem (a 13-year-old patient). On Т2-weighted imaging (а) and Т1-weighted imaging (b), a tumour of pons is revealed with expansion onto midbrain. The third and the lateral ventricles are dilated
Infratentorial Tumours
693
Fig. 7.115a–f AA of the brainstem (a 6-year-old child). CT images with CE (а–c) reveal a tumour of the pons of heterogeneous structure. Predominantly, the lateral parts of the tumour tissue rightwards are enhanced. Т2-weighted imaging (d,e) shows diffuse involvement of pons with an exophytic component (in the fourth ventricle). CE (f) has heterogeneous appearance
694
Chapter 7
Fig. 7.116a–c GB of the pons (a 15-year-old patient). Т2-weighted imaging (а), Т1-weighted imaging before (b) and after (c) CE shows almost
complete involvment of the transverse section of brainstem; however, only a part of tumour is enhanced
Fig. 7.117a–c GB of the pons (a 12-year-old child). CT with CE (а). On the background of a generally hypodensive zone into the pons, an area of heterogeneous accumulation of contrast medium is seen, and the central part of the lesion is necrotic. Т1-weighted imaging (b)
shows that a tumour has heterogeneous structure and affects nearly the entire transverse section of pons. CE (c) identifies the heterogeneous character of GB enhancement
Infratentorial Tumours
Fig. 7.118a–f GB of the pons (a 7-year-old child). On CT with CE
(а), a ring-shaped tumour is seen in the caudal aspect of pons rightwards. MRI was done 2 weeks after CT: Т2-weighted imaging (b) and Т1-weighted imaging (c) clearly demonstrates the intrabrainstem
695
tumour with central area of necrosis. After CE, a peripheral type of enhancement is seen (d–f). No signal changes are seen after CE in the necrotic area
696
Fig. 7.119a–d Primitive neuroepithelial brainstem tumour (a 7-year-old child). Т2-weighted imaging (а) and Т1-weighted imaging (b) show a tumour of the right half of pons, which has hyperintensive signal on Т2-weighted imaging and hypointensive signal to brain tissue Т1-weighted imaging. After CE (c,d), the intensive but heterogeneous accumulation of contrast medium is seen
Chapter 7
Infratentorial Tumours
697
Fig. 7.120a–c Glioma of the midbrain tectum (an 11-year-old child). CT image (а) shows an isodensive mass lesion of the quadrigeminal lamina. The third and the lateral ventricles are dilated. On MRI before (b) and after (c) CE, the tumour of the midbrain tectum is seen, without accumulation of contrast medium
Fig. 7.121a–c Glioma of the midbrain tectum (a 9-year-old child). Axial (а) and sagittal (b,c) MRI reveal a tumour of the quadrigeminal
lamina with occlusion of the aqueduct of Sylvius. The tumour is hyperintensive on Т2-weighted imaging
698
Chapter 7
Fig. 7.122a–c Craniospinal PA (a 4-year-old child). Т1-weighted imaging before (а,b) and after (c) CE reveal a tumour of the medulla ob-
longata and the upper cervical spinal cord. The tumour is hypointensive to brain tissue on Т1-weighted imaging and intensively accumulates contrast medium. The ventricular system is dilated
Fig. 7.123a–c PA of caudal aspects of the medulla oblongata (a
7-year-old child). Т1-weighted imaging before (а,b) and after CE (c,d): tumour of homogeneous structure is revealed at the level of
the foramen of Magendie, with occlusion of the superior parts of the ventricular system. d–f See next page
Infratentorial Tumours
699
Fig. 7.123d–f (continued) PA of caudal aspects of the medulla oblongata (a 7-year-old child). Postoperative MRI (e,f) shows that the tumour
was completely removed
Fig. 7.124a–c Ganglioastrocytoma of the medulla oblongata (a 10-year-old child). Т2-weighted imaging (а) and Т1-weighted imaging after
CE (b,c) reveal a tumour of the medulla oblongata with a small exophytic component backwards. The tumour intensively accumulates contrast medium
700
Differential diagnosis of brainstem tumours on CT and MRI should be made from brainstem encephalitis, demyelinative disorders (multiple sclerosis, acute disseminated encephalomyelitis), lymphoma, tuberculosis, NF I, and haemorrhages (cryptogenic malformations) of the brainstem (Fig. 7.125).
7.4.2 Brainstem Haemorrhages Brainstem haemorrhage is a separated, often-subependymal haemorrhage, usually located in the pons, which does not destroy but compress brainstem structures. Brainstem haemorrhages should be distinguished from tegmental basilar brainstem haemorrhage, which develops in elderly people with arterial hypertension. Haemorrhagic transformation of the brain tissue is typical for the latter and not only tegmental, but also brainstem base involvement occurs. The course is severe, irreversible, and often fatal. Surgical removal of such tegmental haemorrhages is not performed. The causes of brainstem haemorrhages are occult vascular malformations (OVM). This term was introduced by Russell and Rubinstein (1989) in 1950s to define vascular malformations not revealed on cerebral angiography. The following OIVM are distinguished: telangiectasias, cavernous angiomas, venous angiomas, and AVM with thrombosis. Capillary telangiectasias present as one of the branched (racemous) vascular malformations. Accumulation of dilated capillaries with alternating brain tissue inside is the most important histological feature. On microscopy, telangiectasias are seen as dilated vessels lined with endothelium lying on basal membranes. Elastic and muscle tissues are absent, and an argyrophilic matrix is identified in each vessel. The pons is the usual location of telangiectasias—the predominant site of brainstem haemorrhages. Cavernous malformations or angiomas (CА) were distinguished as a group of pure developmental defects only in 1979 within the International Histological Classification of Tumours. Before, CA were considered tumours. CА represents a system of communicating vascular cavities of different size and of a sinusoid form filled with blood. Vascular cavities are separated by connective tissue septi, which are common for several adjacent cavities. Walls of these cavities are lined with endothelium that forms papillary exophytic growths. Intrinsic argyrophilic matrix is present in each cavity, and muscle and elastics layer are absent. Capillaries and intermingling strands of endothelial cells without lumen are located between vessels. There is no brain tissue within CA structure, but cysts, thromboses, sclerosis, and calcifications are found. The origin of sclerotic changes is unequivocal; they are due to organisation of intra-CA thrombi. Microhaemorrhages within and beyond the malformation are typical for CA, even in silent clinical course. Reactive glial changes stained yellow are typical in the perifocal zone and are due to imbibition of the brain tissue with haemosiderin accumulated in macrophages. Often accumulations of branching vessels resembling capillaries are seen on the periphery of a malformation. In contrast to AVM, there is no an area of “fast flow” inside CA, no large arteries or drainage veins connected with AV shunting. The
Chapter 7
size of CA varies from several millimetres to 8 cm. In the case of intra-CA haemorrhage, a rupture of septi between cavities may occur with formation of larger cavities. That is why in some cases CA consist of only a few cavities, representing a single- or multichamber haemorrhage. Venous vascular malformations (venous angiomas, VA) have the following classical anatomical features: true veins with thinned and hyalinised walls with persistence of brain parenchyma between veins. The main feature of AVM with thrombosis is presence of elastic and muscle fibres in the vessel walls. Different combinations of OVM, which are mixed malformations, are also encountered. There are no reliable statistics on brainstem haemorrhages; however, they are relatively rare conditions. On autopsy, only 6–9% of all intra-axial haemorrhages are brainstem haemorrhages. In addition, in many patients brainstem haemorrhages are missed, being diagnosed as inoperable brainstem tumours, posterior circulation strokes, MS, or brainstem encephalitis, so they are not registered as haemorrhages, which naturally biases the true incidence of this pathology. From 1986 to 2000, 68 patients underwent surgery for brainstem haemorrhage and/or OVM in our clinic (Konovalov et al. 1991, 1997, 2001b). Seven patients were younger than 10 years of age, which does not support the opinion that the condition is rare in children. The youngest patient was 2 years old. Depending on the type of onset (neurological event), three variants are distinguished: stroke-like, pseudotumour, and mixed (encompassing elements of the former two). Angiography does not usually reveal any signs of vascular malformation. In some cases, displacement of cerebral arteries, typical for a mass lesion in the brainstem, is found. In cases of large venous angiomas, pathologically dilated veins seen in the capillary phase and smaller inletting branches (“brush” sign) are an exception (Fig. 7.126). MR venography may serve as an additional technique to verify presence of veins after CE (Fig. 7.127). CT and MRI are mandatory to make a diagnosis of brainstem haemorrhage. However, it is hard to diagnose OVM if haemorrhage has occurred, by CT and MRI, especially if a malformation is small, or is self-destroyed after haemorrhage. Moreover, in CA, a rupture of septi between cavities occurs, and thus a multichamber haemorrhage forms. On CT, a lesion of abnormal density is revealed in the pons, medulla, or midbrain. Brainstem haemorrhage are usually spherical or round in shape. If located at the level of inferior brainstem, artefacts caused by bone may hinder imaging of the haemorrhage. Density changes depend on the time of onset or the age of haemorrhage. Temporal evolution of a haemorrhagic cavity on CT is well studied. In the acute stage, brainstem haemorrhage is hyperdensive (Fig. 7.128), except for those occurring in coagulopathies and anemias, in which cases, they may be isodensive. After liquefaction and resorption of a blood clot, which starts on a haemorrhage periphery, if there were no repeated haemorrhages, then an initial haemorrhage becomes less hyperdensive. One to 6 weeks after onset, CT reveals an isodensive lesion and after, CE con-
Infratentorial Tumours
Fig. 7.125a–f Differential diagnosis of brainstem lesions. Case 1. FA.
On Т1-weighted imaging (а) and Т2-weighted imaging (b,c), an area of abnormal MR signal is seen in the left half of pons, the brainstem is deformed, and the fourth ventricle is compressed. Case 2. Multiple
701
sclerosis. Т1-weighted imaging (d) and Т2-weighted imaging (e,f), show a round, hypointensive lesion in the left half of pons, which is hyperintensive on Т2-weighted imaging and hypointensive to brain tissue on Т1-weighted imaging. The brainstem is not deformed
Fig. 7.126a,b Venous angioma of the middle left cerebellar peduncle. Cerebral angiography (а,b). Abnormally located small veins in the left half of the posterior fossa are seen in the venous phase, which drain into a single hypertrophied vein—the “brush” sign (arrows)
702
Fig. 7.127a–f Combination of CA and venous angioma. CT before (а) and after (b) CE in the middle left cerebellar peduncle: a hyperdensive lesion is seen with minimal CE. The hypertrophied abnormal vein that is located near the pontocerebellar cistern intensively accumulates contrast medium. On Т1-weighted imaging (c) and Т2-
Chapter 7
weighted imaging (d), a heterogeneous lesion of abnormal MR signal is seen, with signs of acute and subacute haemorrhage. MR venography (3D TOF with CE and saturation of signal of arteries) additionally demonstrates a venous angioma (arrows) backwards and lateral from the CA (е,f)
Infratentorial Tumours
703
trast medium accumulates on the lesion periphery due to blood–brain barrier impairment in the newly formed vessels of a newly formed haemorrhage capsule (Fig. 7.129). Then, a haemorrhage becomes hypodensive, which represents the liquefaction and resorption of the blood clot (Fig. 7.130). In rare cases of chronic haemorrhages, sedimentation phenomenon may be seen due to sedimentation of blood elements and remnants of the blood clot that have not yet undergone lysis (Fig. 7.131). Despite the fact that CT reveals an abnormal brainstem lesion and indicates haemorrhage in the acute stage more precisely, CT signs in the chronic stage are nonspecific and do not differentiates a haemorrhage from a tumour, even a giant saccular aneurysm of the basilar artery with pseudotumoural course. MR findings in brainstem haemorrhages are more specific. Due to high contrast, facility of soft tissue structures, multiplanar scanning, and absence of bony artefacts MRI identifies the shape and location of brainstem haemorrhage precisely, and in cases in which an aneurysm is the source of brainstem haemorrhage, it is possible to ascertain its connection with cerebral arteries, their blood supply, and multilayer thrombosis if present (Fig. 7.132). Differential features of brainstem haemorrhage on MRI are more numerous—the quality of imaging of haemorrhages is based on the ratio of haemoglobin-oxidising derivates, which have paramagnetic properties. Other factors determining the appearance of brainstem haemorrhages on MRI are protein content, size, the extent of erythrocyte hydration, the extent of retraction of blood clot, and strength of magnetic field of the MR scanner and the
pulse sequences used. In the acute stage (several minutes to several hours), a formed clot contains oxyhemoglobin, which does not influence the proton relaxation times. This is why the quality of imaging of an acute haemorrhage is determined by the presence of water molecules—they look isointensive on Т1-weighed images and hyperintensive on Т2-weighted images. Later, oxyhemoglobin transforms into deoxyhaemoglobin, which shortens Т2 in the area of a haemorrhage, but the latter still remains isointensive on T1-weighted imaging (Fig. 7.133). Further oxidation leads to formation of methaemoglobin, which markedly increases signal of haemorrhage on Т1- and Т2-weighted imaging. MR signal increase (especially on Т1-weighted images) goes from the periphery to the centre and speaks to the lysis of erythrocytes and of methaemoglobin (release)—the intracellular methaemoglobin is hyperintensive on Т1-weighted imaging and hypointensive on Т2-weighted imaging; free methaemoglobin is characterised by high MR signal in all sequences (Figs. 7.134–7.136). At the end of subacute and the beginning of the chronic stages, the area of narrow hypointensive signal starts to form on the periphery, seen on T2-weighted imaging and represented by haemosiderin deposits in macrophages in the haemorrhage capsule. By that time, the haemorrhage acquires hyperintensive signal of its centre and hypointensive signal at the periphery in all sequences (Fig. 7.137). Several months after the haemorrhage, the volume of hematoma decreases, and local defect remains on its place. Haemosiderin deposition in macrophages remains for a long period, sometimes years,
Fig. 7.128 Acute brainstem haemorrhage (a 15-year-old patient). A
Fig. 7.129 Subacute encapsulated brainstem haemorrhage (a
hyperdensive area is seen on CT at the level of the posterior fossa in the right half of pons—an acute brainstem haemorrhage
10-year-old child). An area of ring-shaped accumulation of contrast medium is seen on CT at the level of the posterior fossa, in the capsule of haemorrhage. The density of brainstem haemorrhage content is lower than that of brain tissue
704
Chapter 7
Fig. 7.130a,b Encapsulated brainstem haemorrhage (a 5-year-old child). On CT with CE (а), an area of ring-shaped accumulation of contrast medium is seen on CT in the left half of pons, in a brainstem haemorrhage capsule. The density of brainstem haemorrhage content is lower than that of brain tissue. On Т1-weighted imaging (b), haemorrhage has high signal intensity due to methaemoglobin. The haemorrhage capsule is also identified
Fig. 7.131a,b Chronic brainstem haemorrhage (a 7-year-old child). On CТ (а,b) a round, hypodensive lesion in the right half of pons is seen—chronic haemorrhage. Sedimentation phenomenon is seen in the inferior part of haemorrhage as a hyperdensive area
Infratentorial Tumours
705
Fig. 7.132a,b A giant aneurysm of the basilar artery with partial thrombosis (a 14-year-old patient). Т2-weighted imaging (а) and Т2-weighted imaging (b) shows the round mass lesion in the pons. It has a heterogeneous abnormal MR signal. The brainstem is markedly compressed
which is why the changes mentioned are MR features of an “old” haemorrhage. In the cases in which duration of the disease does not exceed 1.5 months, CT reveals hyperdensive areas corresponding to blood within the brainstem, which has round or irregular shape. The brainstem density with a mass lesion does not change, or, it may be hypodensive due to oedema. The fourth ventricle is usually deformed. In some cases, the pontine cisterns remain free. Persistence of hyperdensity speaks to the recurrent haemorrhages, the source of which are SVM (in cases of CA), or newly formed vessels of the capsule (Fig. 7.138). Sometimes the sedimentation phenomenon of blood cells and protein components is seen in large haemorrhages (Fig. 7.139). Both CT and MRI differential diagnosis of primary haemorrhage or haemorrhage into a tumour on early stages is very difficult. But absence of oedema, tumour tissue bleeding, and perifocal hypointensive area (especially on T2-weighted imaging), typical signal changes related to temporal evolution of a haemorrhage during the follow-up examinations, allow differentiation of these conditions more precisely (Konovalov et al. 2001c). Determination of type of OVM as a cause of haemorrhage is very important in elaborating tactics of surgical treatment. It should be remembered that imaging of a small malformation within the site of haemorrhage is impossible, as the latter overwhelms all other features. It is possible to determine the type of malformation if haemorrhage is absent, or if its size is small. Undoubtedly, CA diagnosis is established if only a classic MR picture is registered—the central lesion with network (heterogeneous) structure, consisting of areas of hypointensive and hyperintensive signal (in all sequences), surrounded by a peripheral low signal, clearly visualised on T2-weighted imaging (Fig. 7.140). Heterogeneous signal change reflects the morphological substrate of CA, i.e. a complex of pathological changes occurring within the malformation and adjacent
brain tissue. Recurrent “silent” microhaemorrhages beyond the malformation boundaries lead to haemosiderin and ferritin deposition in macrophages, which gives a pathognomonic MR feature: a ring of hypointensive signal surrounding a malformation (Fig. 7.141). Areas of hypointensive signal within malformation on T2-weighted imaging are considered acute haemorrhages or calcifications. Areas of high signal intensity (on Т1- and Т2-weighted images) correspond to subacute haemorrhage, different stages of thrombosis, and organisation of thrombi. Minimal or absent CE is typical of CA (due to enhancement of separate venous cavities) on CT and MRI (Fig. 7.142). On CT, CA (if are not very small) appear as lesions of regular round or irregular shape and high density, without CE. If a hyperdensive lesion persists on CT (over 1.5 months), without any transformation, then CA should be suspected; if it were haemorrhage, then its density would have gradually changed (Fig. 7.143). However, such a classic picture of CA is found in not more than half of cases of suggested CA located supratentorially. In our own series of observations of suggested OVM, including brainstem CA, a hyperintensive signal was identified on MRI (T1-weighted) only in half of all cases, which corresponds to subacute or encapsulated haemorrhage.
7.5
Меtastases
Metastases are frequently found among the posterior fossa tumours in adults. Lung and breast cancers are the most frequent sources of infratentorial metastases. Thus, bronchiogenic carcinoma accounts for cerebral metastases in 30% of cases. Percentage of cerebral metastases of breast cancer is lower: 18–30%. Other tumours that produce cerebral metastases (or have the CNS tropism) are melanoma, kidney carcinoma, and thyroid gland cancer.
706
Chapter 7
Fig. 7.133a–c Acute brainstem haemorrhage (an 11-year-old child). On CT, a hyperdensive lesion is seen in the left middle cerebellar peduncle (а). On Т2-weighted imaging (b), the haemorrhage is hypoin-
tensive, and an area of perifocal oedema is seen also. On Т1-weighted imaging (c), MR signal changes are minimal. A deformation of brain structures is seen within the site of haemorrhage
Fig. 7.134a–c Subacute brainstem haemorrhage (a 15-year-old
middle cerebellar peduncle. The lesion is hyperintensive on periphery (on Т1-weighted imaging), which corresponds to free methaemoglobin
child). On Т2-weighted imaging (а) and Т1-weighted imaging (b,c), a round mass lesion is seen in the left half of the pons and the left
Infratentorial Tumours
Fig. 7.135a–f Intrabrainstem haemorrhage (a 13-year-old child).
On FLAIR (a) Т2-weighted imaging (b) and Т1-weighted imaging (c,d), a round mass lesion is seen in the right half of the pons, with
707
MR signal features typical for subacute haemorrhage—the stage of methaemoglobin transformation. CТ (е,f) with CE reveals that the peripheral part of haemorrhage accumulates contrast medium
Fig. 7.136a,b Intrabrainstem haemorrhage (a 5-year-old child). Axial (a) and sagittal (b) T1-weighted imaging reveals a round mass lesion in the left half of the pons, with high MR signal, which is typical for subacute haemorrhage
708
Chapter 7
Fig. 7.137a–c Brainstem CA. Axial Т2-weighted imaging (а) and Т1weighted imaging (b) shows an area of heterogeneous signal changes in the pons. Peripheral part of the lesion is markedly hypointensive on T2-weighted imaging. On axial (b) and sagittal (c) T1-weighted
imaging, an additional area of signal change is seen besides the hyperintensive area, which represents a haemorrhagic component. The latter spreads into the ventral part of pons
Fig. 7.138a–c Brainstem CA. CT (а). An acute haemorrhage seen
fied by CT looks isointensive on T1-weighted imaging and dark on T2-weighted imaging. In front of it, an additional area is seen that is hyperintensive in all sequences—a subacute haemorrhage
as a hyperdensive area is visualised in the lateral part of pons. Т2weighted imaging (b) and Т1-weighted imaging (c) show more heterogeneous MR signal changes—the subacute haemorrhage identi-
Infratentorial Tumours
Fig. 7.139a–h Chronic brainstem haemorrhage. Case 1. Т1-weighted imaging (а–c) and Т2-weighted imaging (d): a round area of MR signal change is seen in the right half of the pons. In the inferior part of the lesion, an area hypointensive on Т2-weighted imaging and hyperintensive on Т1-weighted imaging is seen—sedimentation phe-
709
nomenon. When the patient lies prone, heavy elements move inside the haemorrhage (b). Case 2. MRI in Т1 (e,f) mode reveals a hyperintensive lesion in the right pons. T2-weighted imaging (g) performed on the back (supine) and on the abdomen (prone) (h) visualises the displacement of blood components into the hematoma’s cavity
710
Chapter 7
Fig. 7.140a–c Brainstem CA (a 15-year-old patient). Т2-weighted imaging (а,b) and Т1-weighted imaging (c) identifies a small cellular (heterogeneous) area consisting of zones of hypointensive and hy-
perintensive signal in all sequences in the right half of the bottom of fossa rhomboidea. This area is encircled by a hypointensive ring better seen on Т2-weighted imaging
Fig. 7.141a–c Brainstem CA (a 7-year-old child). On CT (а) with
Т1- and Т2-weighted imaging). The part of angioma without haemorrhage is hypointensive. It has a patchy picture and is located forward of the haemorrhage
CE, an area with heterogeneous hyperdensity is seen in the pons. Т2-weighted imaging (b) and Т1-weighted imaging (c) shows an angioma with signs of subacute haemorrhage (hyperintensive signal on
Infratentorial Tumours
711
Fig. 7.142a–f Brainstem CA (an 11-year-old child). On Т2-weighted imaging (а) and Т1-weighted imaging before (b) and after (d–f) CE, a mass lesion in the pons is revealed, which has hyperintensive on Т2-weighted imaging and isointensive to brain tissue signal on Т1-
weighted imaging. On a gradient echo image (c), a lesion is hypointensive. Haemosiderin deposits are visualised around the haemorrhage (on T2 and gradient echo imaging). CE is mild and is seen only in the central parts of cavernoma
On CT, metastases are characterised by intensive CE, after which they become hyperdensive. Their borders with brain tissue are unclear. Perifocal oedema may be absent even in larger–sized tumours, which is characteristic for metastases of the posterior fossa (Fig. 7.144). MRI, especially with CE, better visualises infratentorial metastases. On conventional MR images, features of metastases are nonspecific. Т1-weighted images are uninformative in terms of lesion borders, as they reveal only mass effect, dislocation of adjacent cerebellar hemispheres, and brainstem. The fourth ventricle is displaced to the opposite to the side contralateral to metastasis. If a necrotic part is present, it produces hyperintensive MR signal in T2 sequence. Perifocal oedema is better assessed on FLAIR and T2-weighted imaging. Borders of lesions are well seen after CE (Figs. 7.145, 7.146). If a metastasis is situated subdurally, then it may resemble men-
ingioma (Fig. 7.147). In such cases, if other metastases are absent, then it complicates the diagnosis. In contrast to cerebral metastases, meningiomas have clear borders with brain tissue, and a vascular matrix seen in the tumour stroma. Two types of features are seen in melanoma metastases, (1) hyperintensive signal on Т1-weighted imaging and hypointensive signal on Т2-weighted imaging and (2) hypo-, isointensive signal in all sequences. The first type of picture is seen if metastases contain melanin, which has a paramagnetic effect (Fig. 7.148). The latter type is seen in dissemination of so-called amelanotic melanoma (Fig. 7.149). Diagnosis of infratentorial metastases should be made very carefully, as many nontumoural disease may resemble a malignant tumour in their signal characteristics. For instance, atypical AVM or CA may mimic melanoma metastases (Figs. 7.150–7.153).
712
Chapter 7
Fig. 7.143a–d Brainstem CA (a 14-year-old child). On CT (а), a small hyperdensive area is seen in the left middle cerebellar peduncle. MRI done in three mutually perpendicular planes in T2 sequence (b–d) ascertains the location of cavernoma. Low signal is due to haemosiderin deposits on periphery
Fig. 7.144a–c Multiple metastases of breast cancer. CT images with CE. Tumour nodes with central necrosis and enhancing peripheral parts
are seen in both cerebellar hemispheres (а–c)
Infratentorial Tumours
Fig. 7.145a–c Metastasis in the cerebellar hemisphere. Т2-weighted imaging (a) and T1-weighted imaging before (b) and after (c) CE. A mass lesion, which intensively accumulates contrast medium, is seen in the right cerebellar hemisphere. The tumour is isointensive
713
to brain tissue on Т2-weighted imaging (а) and Т1-weighted imaging (b). Perifocal oedema is seen around the tumour, which is hyperintensive on T2-weighted imaging
Fig. 7.146a–c Metastasis in the posterior fossa. Т2-weighted imaging (а) reveals an abnormal hyperintensive lesion in the lateral parts of the posterior fossa rightwards; brainstem is displaced on the left. After CE (b,c), the lesion intensively accumulates contrast medium
714
Chapter 7 Fig. 7.147 Metastasis in the posterior fossa. On Т1-weighted imaging after CE, a lesion is
seen in the cerebellopontine angle, which is pulled along the medial margin of the pyramid of the temporal bone. There is no invasion of the tumour into the meatus acousticus internus; however, abnormal tissue grows along the apex of the pyramid with passage into the medial parts of the middle cranial fossa rightwards
Fig. 7.148a,b Melanoma metastasis in the right cerebellar hemisphere. Т2-weighted imaging (а) and Т1-weighted imaging (b). A tumour hypointensive on Т2-weighted imaging and hyperintensive on Т1-weighted imaging in the central zone is seen. Microcysts perifocal oedema is found on the periphery—obstructive hydrocephalus
Fig. 7.149a–c Melanoma metastasis. CT with CE (а). There is a homogenous and hyperdensive mass lesion in the lateral parts of the posterior fossa leftwards. Т2-weighted imaging (b) and Т1-weighted imaging (c). The tumour has MR signal characteristics close to that of brain tissue
Infratentorial Tumours
715
Fig. 7.150a–f Arteriovenous malformation in the cerebellar vermis and the medial parts of the left cerebellar hemisphere. Т2-weighted imaging (а,b) and Т1-weighted imaging (c–f) show a hypointensive area of irregular shape and heterogeneous structure
Fig. 7.151a–c CA of the right cerebellar hemisphere. CТ images (а–c). In the lateral parts of the right half of the posterior fossa, a mass lesion
is identified that is heterogeneous hyperdensive and encircled by perifocal oedema
716
Chapter 7
Fig. 7.152a–f Venous angioma of the right middle cerebellar peduncle. Т2-weighted imaging (а–c), Т1-weighted imaging (d,e): MR picture
typical for venous angioma. MR venography (f) identifies a vein of atypical shape, size, and location rightwards to the median line
Fig. 7.153a–c CA of the right cerebellar hemisphere (a 2-year-old
child). CТ (а). A large mass lesion of heterogeneous structure with microcalcifications, hyperdensive foci, and cysts is seen in the right cerebellar hemisphere. Т2-weighted imaging (b) and Т1-weighted
imaging (c) shows the lesion with heterogeneously hypointensive signal on Т2-weighted imaging and marked hyperintensive signal on Т1-weighted imaging (due to methaemoglobin in the cavities of cavernoma)
Infratentorial Tumours
717
Refere n c e s al-Mefty O, Borbe L (1997) Skull base chordomas: a management challenge. J Neurosurg 86:182–189 Atlas SW (1991) Infratentorial tumors. MRI of brain and spine. Ed. By Atlas S.W. New York: Raven Press Ball W (1997) Infratentorial neoplasms in children. In: Ball W (ed) Pediatric neuroradiology. Lippincott-Raven, Philadelphia, pp 319–368 Barkovich A (2000) Pediatric neuroimaging, 3rd edn. Lippincott Williams & Wilkins, Philadelphia Barkovich A et al (1990) Brainstem gliomas: a classification system based on magnetic resonance imaging. Pediatr Neurosurg 16:73–83 Beutow M et al (1991) Typical, atypical and misleading features in meningioma. Radiographics 11:1087–1100 Bilaniuk L (1990) Adult infratentorial tumors. Semin Roentgenol 25:155–173 Chiechi M et al (1995) Intracranial subependymomas: CT and MR imaging features in 24 cases. AJR Am J Radiol 165:5:1245–1250 Conway JE et al (2001) Hemangioblastomas of CNS in von HippelLindau syndrome and sporadic disease. Neurosurgery 48:55–63 Daglioglu E et al (2003) Tectal gliomas in children: the implications for natural history and management strategy. Pediatr Neurosurg 38:5:223–231 Elster A et al (1988) Intracranial hemangioblastomas: CT and MR findings. J Comput Assist Tomogr 12:5:736–739 Fernandez C et al (2003) Pilocytic astrocytomas in children: prognostic factors—a retrospective study of 80 cases. Neurosurgery 53:3:544–553 Furie D et al (1995) Supratentorial ependymomas and subependymomas: CT and MR appearance. J Comput Assist Tomogr 19:4:518–526 Gao P et al (1992) Radiologic-pathologic correlation. Epidermoid tumours of the cerebellopontine angle. AJNR Am J Neuroradiol 3:3:863–872 Gentry L et al (1991) MR imaging of primary trochlear nerve neoplasms. AJNR Am J Neuroradiol 12:707–713 Gerosa M, Visca A, Rizzo P et al (2006) Glomus jugulare tumours: the option of gamma knife radiosurgery. Neurosurgery 59:3:561–569 Guillamo J et al (2001) Brainstem gliomas in adults. Prognostic factors and classification. Brain 124:2528–2539 Gusnard D (1990) Cerebellar neoplasms in children. Semin Roentgenol 25:263–278 Harwood-Nash D (1994) Primary neoplasms of the central nervous system in children. Cancer 67:1223–1228
Konovalov A et al (1993) Brainstem tumours: indications to surgery, results of surgery. Abstracts of the 6th Congress of Baltic Neurosurgeons. Riga, Latvia, pp 13–15 Konovalov A et al (2003) Gene expression patterns in ependymomas correlate with tumour location, grade and patient age. Am J Pathol 5:1721–1727 Konovalov A, Huhlaeva E, Ozerova V (1991) Clinics, diagnostics and surgery treatment of the brainstem hematomas. J Vopr Neurosurg 1:3–6 (in Russian) Konovalov A, Kornienko V, Pronin I (1997) Magnetic-resonance tomography in neurosurgery. Vidar, Moscow pp. 471 (in Russian) Konovalov A, Kornienko V, Pronin I (2001a) Diagnostics of the brainstem tumours. J Med Visualis 2:4–12 Konovalov A, Kornienko V, Pronin I (2001b) Hematomas and latent vascular malformation of brainstem. J Med Visualis 2:13–18 (in Russian) Konovalov A, Kornienko V, Qzerova V, Pronin I (2001c) Pediatric neuroradiology. Antidor, Moscow (in Russian) Korshunov A et al (2004) The histologic grade is a main prognostic factor for patients with intracranial ependymomas treated in the micronerosurgical era. Cancer 100:1230–1237 Kuroiwa T et al (1995) Posterior fossa glioblastoma multiforme: MR findings. AJNR Am J Neuroradiol 16:583–589 Lavaroni A, Leonard M (1993) Neuroradiological diagnostics of brain tumor in adults. Neuroradiol. pp. 41-54 Lizak P, Woodruff W (1992) Posterior fossa neoplasms: multiplanar imaging. Semin Ultrasound CT MR 13:182–206 Matsko D, Korshunov G (1998) Atlas of tumors of the central nervous system (the histological structure). Polenov A. Neurosurgical Institute, St.Petersburg, pp. 200 (in Russian) McCormick P et al (1988) Trigeminal schwannoma. J Neurosurg 69:850–860 Meyers S et al (1992) MR imaging features of medulloblastomas. AJR Am J Radiol 158:865–895 Meyers S et al (2000) Postoperative evaluation for disseminated medullablastoma involving the spine. Am J Neuroradiol 21:1757–1765 Meyers S, Khademian Z, Biegel J et al (2006) Primary intracranial atypical teratoid/rhabdoid tumours of infancy and childhood: MRI features and patient outcomes. AJNR Am J Neuroradiol 27:962–971 Orrison W, Hart B (2000) Intraaxial brain tumors. In: Neuroimaging. W.B.Saunders company, Philadelphia pp. 583-611 Osborn A (2004) Brain. Diagnostic Imaging. Amirsys, pp. 960
Hendrick E, Raffel C (1989) Tumours of the fourth ventricle: ependymomas, choroid plexus papillomas, and dermoid cysts. In: McLaurin R, Schut L, Venes J, Epstein F (eds) Pediatric neurosurgery: surgery of the developing nervous system. Saunders, Philadelphia
Rubin G et al (1998) Pediatric brainstem gliomas: an update. Child Nerv Syst 14:1613–1673
Ho Vetal. (1992) Radiologic-pathologic correlation: hemangioblastoma. AJNR 13 (5):1343-1352
Russell D, Rubinstein L (1989) Pathology of tumours of the nervous system, 5th edn. Williams and Wilkins, Baltimore
Koller K et al (2003) Medullablastoma: a comprehensive review with radiologic–pathologic correlation. Radiographics 23:1613–1637
Silverstein J et al (1995) MRI of intracranial subependymoma. Comput Assist Tomogr 19:2:264–267
Rumboldt Z, Camacho D, Lake D et al (2006) Apparent diffusion coefficients for differentiation of cerebellar tumours in children. AJNR Am J Neuroradiol 27:1362–1369
718 Tsuruda J et al (1990) Diffusion weighted MR imaging of the brain: value of differentiating between extra-axial cysts and epidermoid tumours. AJNR Am J Neuroradiol 11:925–931 Wanebo J et al (2003) The natural history of hemangioblastomas of the central nervous system in patients with von Hippel-Lindau disease. J Neurosurg 98:1:82–94
Chapter 7 Wistler O et al (2000) Pathology and genetics of tumours of the nervous system: subependymoma. IARC Press, Lyon, pp 80–81 Zee C et al (1992) MRI of meningiomas. Semin Ultrasound CT MR 13:154–169
Chapter 8
Tumours of the Meninges
8.1 8.2
Meningioma .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 719 Non-Meningothelial Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 785
8.1
Meningioma
Meningioma is one of the most frequent intracranial tumours of nonglial origin (Buetow et al. 1991; Raskin 2003; Osborn 2004). According to data of various authors, the incidence of meningioma is from 13 to 20% of all primary brain tumours (Russell 1989; Orrison 2000), occupying first place in the group of the tumours originated from meninges (Sze 1993). Our data included about 5,000 patients with meningioma of a various locations, which, according to the statistics of the Moscow Neurosurgical Institute makes up about 23.9% of all brain tumours. Usually meningioma is diagnosed in adults, and the incidence peak is between 40 and 60 years old, and women are affected more frequently; the ratio of men to women is from 1:2 to 1:4 (according to various data) (Buetow et al. 1991; Kozlov 2001). Only 1–2% of meningiomas are observed in children less than 16 years of age; more often they are located in atypical places, for example, in the posterior cranial fossa or in the lateral ventricle. Unlike among adults, malignant and giant forms prevail among children (Deen 1982). In children, meningioma is accompanied by neurofibromatosis. Multiple meningioma in patients of elder age is observed in 1–9%, confirmed by CT and autopsy data. Any intracranial meningothelial cell regardless of its concrete location, diploic bone layer, the vertebral canal, or an ectopical location, may potentially be the place for meningioma development. The majority of meningiomas originate from of Pachioni granulations (Hope et al. 1992). In rare cases, the tu-
8
mour may grow from fibroblasts of the dura matter, arachnoid membrane around cranial nerves, and vascular plexus. In many cases, meningioma has no clinical symptoms, and it may be an accidental finding in radiological examination or autopsy (Konovalov 1997). Tumour manifestations and symptoms vary, and they depend on location. Epileptic seizures, movement, and sensitivity disorders are typical for convex or parasagittal tumours. Visual field changes are the feature of meningioma of sphenoid bone wings, whereas cavernous sinus tumours, as a rule, cause involvement of the third to sixth cranial nerves. Tumours of the second cranial nerve sheath in the orbit or in the optic nerve canal leads to visual loss up to blindness on the lesion side. Neoplasm of the anterior cranial fossa (meningiomas of olfactory fossa) may reach very large sizes due to the mainly asymptomatic clinical course, with the exception of anosmia (Figs. 8.1, 8.2). On CT and MR scans, meningiomas can be subdivided into two types according to their shape: (1) spherical, lobular, and (2) flat, which causes an infiltration of adjacent meninges (Figs. 8.3, 8.4). Usually meningiomas are well delimitated from neighbouring brain tissue. The surface of the majority of tumours is even; usually there is an arachnoid fissure between brain tissue and meningioma surface, and it contains dislocated vessels and elements of dura matter (Fig 8.5). Meningioma consistency varies from soft up to cartilaginous density, depending on expressiveness of the fibrous tissue and the presence of calcifications. Tumour stroma may contain small haemorrhagic and necrotic components, cystic, and xanthomatous changes (Burger 1991). As a rule, a reactive thickening of the dura matter is observed around the meningioma. The infiltration of adjoining arachnoid membrane is reported in some cases. Morphological examination were mainly carried for creation of a more simplified classification, with the use of markers for detection of proliferative activity, signs of aggressive growth, and features of malignancy (Kleihues et al. 1993; Naidich 1990; Korshunov et al. 2002; Dezamis 2003). According to WHO classification (2000), meningiomas are divided into three main groups: (1) typical (benign), 88–95%; (2) atypical (half-benign), 5–7%; and (3) malignant, 1–2% of all observations. According to the Moscow Neurosurgical Institute statistical data, the inci-
720
Chapter 8
Fig. 8.1a–c Meningioma of the left optic nerve sheath (case 1). Sagittal T1-weighted imaging (a) and axial T2-weighted imaging (b) reveals a mass lesion that envelops the optic nerve. The borders of tumour are clearly visible on a background of hyperintensive signal
from fat in the orbit. Meningioma of the right optic nerve (case 2). CT with CE detects small tumour in the projection of the right orbit (c)
Fig. 8.2a–f Meningioma of the olfactory fossa. DSA in arterial phase (a): the arched upward and backward dislocation of the fronto-polar artery and initial parts of the ACA. The tumour is mainly supplied from the branches of hypertrophied ophthalmic artery. CT after CE (b): meningioma is a hyperdensive mass lesion in comparison with
brain tissue. MRI on T1-weighted imaging before (c,d) and after (e,f) CE detects a large tumour of the olfactory fossa; the vessels of its matrix remain dark on the background of the hyperintensive signal from the mass of the meningioma (arrow)
Tumours of the Meninges
721
Fig. 8.3a–c The parasagittal meningioma of the left frontoparietal region. T2-weighted imaging (a) and T1-weighted imaging (b,c) with CE
reveals a large, round tumour, with homogeneous accumulation of contrast medium
Fig. 8.4a–c Meningioma of the frontoparietal–convex area. T2-weighted imaging (a) and T1-weighted imaging (b,c) after CE detects a mass
lesion of the flat form, which infiltrates the adjacent bone. The tumour intensively accumulates the contrast medium
722
Chapter 8
Fig. 8.5a–f Meningioma of the left frontotemporal area. T2-weighted imaging (a,b), FLAIR (c), and T1-weighted imaging (d) identify a large tumour with perifocal oedema. There is a clearly expressed subarachnoid fissure around the tumour, which contains the dislocated
vessels, elements of the pia matter, and CSF. MRA 3D TOF (e,f) demonstrates the dislocation of the MCA and medial meningeal artery supplying the tumour, with clearly detectable matrix
dence of these types of meningiomas does not differ from the mentioned data: typical (93%), atypical (5%), and malignant (2%). Histologically, the arrangement of cells with moderate nuclei polymorphism and absence of mitosis and necrosis foci is typical for benign forms. These meningiomas are included in this group: fibroblastic, meningotheliomatous, secretory, transitional, and psammomatous. Atypical meningiomas (more often mixed meningotheliomatous structure) are characterised by marked polymorphism of cells and nuclei, the presence of necrosis foci, and mitotic figures. The histological characteristic of malignant meningiomas includes the following features: dense cell arrangement, multiple mitotic figures, and necrosis foci. According to the Institute data, based on location men-
ingiomas are divided into supra- and subtentorial. Among all, those meningiomas of parasagittal (17%), convex (11%), wings of the sphenoid bone, petroclival (10%), olfactory fossa (4,8%), parasellar (9–12%), and posterior cranial fossa, including posterior border of the pyramid of the temporal bone and clivus (10%) location are described. Rarely are tumours of intraventricular location, pineal area, sheaths of the optic nerves (3%), and craniospinal areas observed. Extracranial meningiomas (paranasal sinuses of nose and cranial vault bones) made up 1%. DSA, despite the invention of new, less invasive techniques like MRI and CT angiography, still continues to play a major role in identification of meningioma blood supply sources. One of the main advantages of DSA is its ability to examine different vessels supplying the tumour, for instance, branches of the ICA and ECA (Figs. 8.6, 8.7, 8.8). Unfortunately, DSA
Tumours of the Meninges
723
Fig. 8.6a–f Meningioma of the right parietal–convex area. T2weighted imaging (a) and T1-weighted imaging with CE (b) detects meningioma of a large size with high degree of contrast medium accumulation. Cerebral angiography performed with separate investigations of the ICA and ECA reveals the dislocation of distal segments
of the pericallous artery and parietal branches of the MCA (c). In the venous phase, the dislocated convex veins outline the tumour’s contours (d). The superior sagittal sinus is visible. Selective angiography of the ECA visualises the branch of the middle meningeal artery supplying meningioma, with the formation of the vascular matrix (e,f)
data does not indicate the level of anaplasia in the tissue of meningioma. Benign forms may have a more developed vascular net, whereas ones more malignant have less developed nets (Figs. 8.9, 8.10). In the literature, the angiographic semiotics of meningioma are described comprehensively and in detail. It is accepted to outline the two basic sources of tumour blood supply. The meningeal arteries such as the middle meningeal artery belong to the first and the most frequent type (Fig. 8.11–8.17). Below is a general table of the most frequently supplying meningeal arteries, depending on the primary location of meningioma (Table 8.1). It is necessary to note that large, long-growing meningiomas with infiltrative growth, or anaplastic meningiomas may be additionally supplied from pial branches of intracranial arteries. It is the second source of neoplasm supply. Peri-
focal oedema around even the small meningiomas is often combined with this factor (Ildan 1999). On angiograms, such tumours are characterised by marked early contrast accumulation that remains even during a venous angiography phase, i.e. the so-called “mother-in-law” sign (“comes early and leaves late”, Osborn 1994). CT with CE remains one of the main methods of primary meningioma visualisation; it enables diagnosing no less than 95% of all intracranial meningiomas (Konovalov 1997). Thus, more often meningioma is revealed as a formation of round, oval, or lobular shape, with well-differentiated contours due to intensive (on 40–45 HU) contrast accumulation (Figs. 8.18, 8.19). Therefore, the use of CE is one of the main components of CT diagnosis of meningioma. In a quarter of cases, meningiomas poorly accumulate contrast substance, or do not accumulate it at all, and in these cases, they are isodensive. In
724
Fig. 8.7a–i Parasagittal meningioma of the right posterior frontal area. CT before (a) and after (b) CE reveals a large tumour in left frontal area with intense and uneven accumulation of contrast medium. Selective angiography of the ICA (c–f) and the ECA (g–i) iden-
Chapter 8
tifies the intensively developed vascular net of tumour with abundant blood supply from the ACA and MCA and also from several hypertrophied branches of the medial meningeal artery
Tumours of the Meninges
Fig. 8.8a–f Bilateral falx meningioma of the parietal area. DSA with
CE of the CCA (a) and branches of the ECA (b,c) visualises the abundant blood supply from the terminal branches of the ACA (the
725
ICA system), occipital, and superficial arteries from the ECA system. CT with CE (d–f) reveals a large tumour of bilateral spreading and with invasion of superior sagittal sinus
726
Chapter 8
Fig. 8.9a–f Parasagittal meningioma of the right side of middle third of the falx cerebelli. The CAA examined in coronal (a,b) and lateral (c)
projections reveals the tumour’s vascular net with the supply from the ACA and the hypertrophied superficial temporal artery. The vascular “spots” in capillary and venous phases of DSA (d–f) are visible
Fig. 8.10a–c Atypical meningioma of the middle and posterior third of the superior sagittal sinus. The DSA of territory CCA contrasting
detects poorly expressed tumour vascular net with the blood supply from the MCA and the hypertrophied parietal and occipital branches of ECA (a–c)
Tumours of the Meninges
727
Table 8.1 The most frequent sources of tumour blood supply Location
Arterial supply
Convex, parasagittal area
Superficial meningeal artery (Figs. 8.11, 8.12) Arteries of the falx cerebelli (from ophthalmic artery)
Olfactory fossa
Ophthalmic artery branches (Fig. 8.12)
Sphenoid bone wing
Maxillary artery (Fig. 8.13) Medial meningeal artery
Tentorium, cerebellopontine angle, intraventricular
Tentorial arteries, meningohypophyseal artery (Bernasconi-Cassinari artery) (Figs. 8.14, 8.15, 8.16)
Foramen magnum, clivus
Anterior meningeal artery of clivus (from the vertebral artery) Dorsal meningeal artery (from the meningohypophyseal artery) Muscular and meningeal branches of the vertebral artery (Fig. 8.17)
Fig. 8.11a–c Meningioma of the anterior and middle third of the superior sagittal sinus and falx cerebelli. DSA of the ICA (a,b) and the ECA (c): the abundant blood supply from the branches of the ACA and ophthalmic artery (anterior artery of the falx) and also from the branch of middle meningeal artery is visualised
728
Fig. 8.12a–f Bilateral meningioma of the middle third of the falx cerebelli. Angiography of CCA (a–c) visualises the abundant blood supply from the terminal branches of the ACA, parietal, and superficial temporal arteries from the ECA system. CT with CE (d–f) reveals a large tumour that infiltrates the adjoining bone
Chapter 8
Tumours of the Meninges
729
Fig. 8.13a–f Meningioma of the wing of the sphenoid bone. CT with CE demonstrates a tumour with intense and homogeneous accumula-
tion of contrast medium (a). DSA of the ICA (b,c) and ECA (d–f): the abundant blood supply from the meningeal branches of the siphon of ICA, maxillary artery, and medial meningeal artery
Fig. 8.14a–c Meningioma of the tentorial incisura. DSA visualises a hypertrophied meningeal branch of the tentorium (arrow). Bernasconi-
Cassinari artery (a,b). CT with CE (c)
730
Chapter 8
Fig. 8.15a–c Meningioma of the left lateral ventricle. DSA of the ICA detects the multiple sources of the tumour blood supply: from the
pericallosal artery, hypertrophied anterior choroid artery, and also from the Bernasconi-Cassinari artery (a–c)
Fig. 8.16a–f Meningioma of the tentorial incisura. CT before (a) and after CE (b,c) reveals the hyperdensive tumour with wide attachment to the free edge of the right tentorium. DSA in the arterial phase
(d,e) detects the hypertrophied meningohypophyseal artery supplying the meningioma (arrow). The vascular net of tumour remains in late capillary phase (f)
Tumours of the Meninges
731
Fig. 8.17a–f Meningioma of the craniovertebral region. DSA in arterial (a–c) and venous phases (d) identifies a hypertrophied muscular branch of the left vertebral artery. The right vertebral artery does not participate in tumour blood supply (e,f)
Fig. 8.18a,b Meningioma of the right
frontal area (a 7-year-old child). CT before (a) and after (b) CE detects a large tumour of relatively homogeneous structure with intense contrasting. There is an area of oedema around the tumour
732
Chapter 8 Fig. 8.19a,b Meningioma of the anterior
clinoid process. CT before (a) and after (b) CE identifies an increase of the tumour density
Fig. 8.20a–c Meningioma of the left frontal area. CT before (a,b) and after (c) CE identifies a tumour of mixed structure with predominant hypodensive components
Fig. 8.21a,b Meningioma of the left
temporal area. CT (a,b) after CE detects a hypodensive tumour without accumulation of contrast medium
Tumours of the Meninges
733
Fig. 8.22a–c Meningioma of the right frontal area. CT in the bone-windows regimen (a) and after CE (b,c) identifies a tumour of mixed
structure, with soft tissue and calcifications
general, in up to 75% of all cases, meningiomas show a certain degree of hyperdensity. Hypodensive neoplasms are observed in CT in 1–5% of cases; more often they are lipoblastic, xanthomatous, and microcystic forms (Figs. 8.20, 8.21). Up to 25% of all meningiomas contain calcifications in their structure, which may be solitary and multiple, point-like, and large, and in exceptional situations, the entire tumour may be calcified. Such tumours are easily identified even on plain X-ray craniograms and even more so on CT (Figs 8.22–8.24). Although the presence of large haemorrhages, necrotic parts, and cyst formation (Konovalov 1997; Osborn 2004) are not typical for meningioma, nevertheless, on the periphery the unevenly dilated subarachnoid spaces with signs of degenerative changes of the surrounding parenchyma may be observed, and adjoining cysts (8%) may sometimes reach large sizes (Fig. 8.25). In a third of all cases, there is a hypodensive perifocal zone due to brain tissue oedema. The latter is often combined with
anaplastic changes in the neoplasm structure and the pial type of tumour blood supply. CT easily reveals the bone changes occurring in cases of meningioma, in particular the bone destruction, invasion of the bone marrow, and above all, hyperostosis (Fig. 8.26). The latter changes are the most frequently diagnosed in cases of basal location of meningioma. It is believed that a meningioma may originate from ectopic arachnoid cells in a diploic layer of the cranial vault and the bones of skull base, and the whole tumour has epidural location; it infiltrates and destroys bone. These are so called hyperostotic meningiomas, which are characterised by the combination of widespread infiltration of skull bones and sharp thickening of these bones with the presence of the flat tumour component, the volume of which may be sometimes minimal (Figs. 8.27–8.29). Invasive growth of meningioma in the bone tissue sometimes is accompanied by bone destruction or spicule-like changes. The intensity of these changes does not depend on the level of tumour anaplasia. CT is the
Fig. 8.23a–c Calcified meningioma of the left anterior clinoid process. CT (a–c) visualises a completely calcified tumour with local hyperostosis of the anterior clinoid process
734
Chapter 8
Fig. 8.24a–c Meningioma (fibroblastic type) of the olfactory fossa. CT series (a–c) with CE visualises a large tumour with large calcifications
Fig. 8.25a–c Cystic meningiomas (different cases). a Meningioma of
left frontal area: CT with CE demonstrates a mass lesion with small solid and large cystic component, the ventricular system is dislocated
to the right. b,c Meningioma of the right frontoparietal area: CT with CE visualises the mass lesion consisting of two large cysts and the parietal tumoural node
Tumours of the Meninges
Fig. 8.26a–f Meningiomas with signs of bone structures destruction. Different cases. a Atypical meningioma of the base of middle cranial fossa. b,c Atypical meningioma of the wing of the sphenoid bone: CT demonstrates the destruction of the external wall of orbit and tem-
735
poral bone with the well-detectable solid component, with relatively intense accumulation of contrast medium. d–f Meningioma of the left frontoparietal–convex area, with wide bone destruction in combination with intense calcifications of tumoural tissue
736
Chapter 8
Fig. 8.27a–f Ossified meningioma of the big wing of the sphenoid bone in the right side. CT series in standard (a,b) and bone (c–f) windows with CE detects a pathological thickening and compaction of the big wing of the sphenoid bone, with spread to the temporal bone
Tumours of the Meninges
737
Fig. 8.28a–f Ossified meningioma of the left pterional region. CT series in standard (a,b) and bone (c–f) windows with CE detects a patho-
logical thickening and compaction of the temporal bone and the big wing of the sphenoid bone on the right side
Fig. 8.29a–c Ossified meningioma of the right frontal area. CT series in standard (a,b) and bone (c) windows with CE detects a pathological
thickening and compaction of the right frontal and parietal bones. Soft tissue components of the tumour are not clearly detected
738
Chapter 8
Fig. 8.30a–f Large bilateral meningioma of the middle third of the falx cerebri and superior sagittal sinus. CT series in standard (a–d) and bone (e,f) windows with CE detects a large tumour with the full occlusion of the superior sagittal sinus. There are spicule-like changes in the bone structures
method of choice for radiological diagnostics of such tumours (Fig. 8.30). Hyperpneumatisation of the sphenoid sinus is also one of the typical attributes of the meningioma in an area of a tuber of the sella turcica and the anterior clinoid process. In this case, the hyperostosis in an area of meningioma matrix as well as hyperpneumatisation of the neighbouring departments of the sinus may be observed (Fig. 8.31). The use of spiral-CT scanning mode with thin scans in the diagnostic of an intracranial meningioma facilitates the more qualitative 3D reconstruction and 3D processing from the set of primary axial CT images (Figs. 8.32–8.34). Multispiral CT scanning improves the quality of CT angiography and simultaneously obtains the images of a tumour and surrounding cerebral arteries. However, it is difficult to evaluate the sources of a meningioma blood supply (Figs. 8.35, 8.36) only by SCT angiography. Atypical ring-shaped contrast accumulation, cystic formation, sites of necrosis, and haemorrhages are observed in no more than 10–15% of all cases. Meningiomas with the signs of malignant transformation may not be distinguishable from the benign forms based on CT data (Sheporaitis et al. 1992) (Fig. 8.37). Currently, most of researchers consider MRI as the gold standard in an intracranial meningiomas diagnostics. The studies demonstrated that MRI data are comparable with the CT data in the accuracy of diagnostics; however, MRI excels CT due to its higher informativity in identification of the vascularisation, invasion into venous sinuses, and especially in
an estimation of the level of surrounding brain structures infiltration. The character of MR signal change varies, depending on the different histological types of meningioma. It was noted that in many cases, the signal changes on T2-weighted imaging may correlate with the histological subtype of meningioma. Therefore, up to 90% of the fibroblastic and transitional types of tumour are hypointensive in comparison with white matter, whereas the two thirds of the meningothelial neoplasms are hyperintensive (Elster 1989; Daemerel 1991; Kaplan 1992) (Figs. 8.38, 8.39). However, many authors consider that correlation between meningioma type and the character of signal change is insufficient for establishing the tumour's histological nature based solely on standard MR protocols (Spagnoli et al. 1986; Sheporatitis et al. 1992; Ray 1993). We support the latter opinion. Regardless of histological type, the majority of meningiomas are iso- or hypointensive on T1-weighted imaging in comparison with the brain cortex. On T2-weighted imaging the signal varies from hypointensive (10%) to iso- (50%) and to moderately hyperintensive (40%) (Figs. 8.40–8.42). The rare forms of meningioma may be characterised by unusual intensity changes on MRI. As observed in the literature, lipoblastic meningioma may result from lipoid transformation of the cells when their cytoplasm contains lipoid inclusions with a high amount of triglycerides. In this case, tumour may be bright on T1-weighted imaging and dark on T2-weighted imaging. The chemical shift artefact is typically observed on the tumour borders.
Tumours of the Meninges
739
Fig. 8.31a–f Meningiomas with local hyperostosis. Different cases: a,b meningioma of the tubercle of sella turcica; c,d meningioma of the
lesser wing of the sphenoid bone; e,f meningioma of the right anterior clinoid process
Fig. 8.32a–c Large meningioma (meningotheliomatous type) of the greater wing of the sphenoid bone. CT with CE
740
Fig. 8.33a–c Meningioma (meningotheliomatous) of the olfactory fossa. CT series (a) detects a mass lesion with intense homogeneous accumulation of contrast medium, on the right side surrounded
Chapter 8
by the perifocal oedema. Coronal (b), and sagittal (c) reformations demonstrate the spreading of the tumour at the base of anterior cranial fossa
Fig. 8.34a–c Meningioma (psammomatous) of the middle cranial fossa. CT series (a) detects a mass lesion with the total calcification occupying virtually all middle cranial fossa. 3D: view from side (b) and view from above (c) demonstrates the spatial interrelations between the tumour and bones of the skull base
Tumours of the Meninges
741
Fig. 8.35a–c Meningioma (meningotheliomatous) of the olfactory fossa. CT (a) with CE reveals a mass lesion in the projection of the anterior cranial fossa, with homogeneous accumulation of contrast medium. CT angiography (b,c) detects a tumour and the dislocated ACA
Fig. 8.36a–f Meningioma of the olfactory fossa. CT series before (a) and after (b) CE identifies tumour in the projection of the anterior cranial fossa with ring-shaped accumulation of contrast medium; the calcifications are visualised in the periphery. CT in coronal and
sagittal reformations (c,d) reveals a tumour and upwardly dislocated ACA. 3D reconstruction (e,f view from above) demonstrates the tumour and the ACA located on its upper contour
742
Fig. 8.37a–f Malignant meningioma of the anterior cranial fossa.
CT before (a,b) and after (c,d) CE visualises a giant neoplasm with homogeneous accumulation of contrast medium. Perifocal oedema
Chapter 8
is absent. Cerebral angiography in the lateral projection (e,f) detects the arched upward dislocation of the ACA; the tumour’s vascular net is minimal
Tumours of the Meninges
743
Fig. 8.38a–c Fibroblastic meningioma of the anterior cranial fossa. T2-weighted imaging (a,b) and T1-weighted imaging (c) detect a large
tumour; the soft tissue component of those has the MR characteristics close to those of non-affected brain. The calcified part of the meningioma has a hypointensive MR signal in all sequences
Fig. 8.39a–c Parasagittal meningioma (meningotheliomatous) of the left frontal-parietal area. T2-weighted imaging (a), T1-weighted imaging before (b) and after (c) CE identifies a round neoplasm. The
tumour is hyperintensive on T2-weighted imaging and slightly hypointensive on T1-weighted imaging. The accumulation of contrast medium is intense and homogeneous
744
Chapter 8
Fig. 8.40a–c Meningioma of the tentorial incisura. T2-weighted imaging (a,b) and T1-weighted imaging (c) detects a tumour of supra- and
subtentorial locations. The tumour is slightly hyperintensive in comparison with the brain tissue on T2-weighted imaging, and it is slightly hypointensive on T1-weighted imaging
Fig. 8.41a–c Meningioma (meningotheliomatous) of the right temporal area. T2-weighted imaging (a) and T1-weighted imaging (b) detect
a large neoplasm with hyperintensive signal in T2 sequence and hypointensive in T1. CE emphasises (c) the internal structure of the meningioma
Fig. 8.42a,b Parasagittal meningioma
(meningotheliomatous) of the left frontal area. MRI on T1-weighted imaging (a,b) detects a hypointensive neoplasm of the round form
Tumours of the Meninges
Fig. 8.43a–c Giant parasagittal meningioma of the middle third of
745
the falx cerebri, in the right hemisphere. T2-weighted imaging (a) and T1-weighted imaging (b) reveals a large tumour of a heteroge-
neous structure (especially on T2-weighted imaging). The border between the tumour and compressed brain is clearly visible in the coronal projection (c)
In general, meningioma are relatively homogeneous lesions despite the sometimes-large sizes on MR images. Heterogeneity of internal structure meningioma depends on several factors: tumour blood supply, the presence of macro- and microcysts, haemorrhages, calcifications, and sites of stroma with different density (Zimmermann et al. 1985) (Fig. 8.43). In cases of convex and basal locations of meningioma, MRT may reveal the radial passage of the small branches of the supplying meningeal arteries in the neoplasm stroma, the so-called matrix of the tumour. On T2- and T1-weighted images, it looks like hypointensive sites of coiled form, streaming like diverging rays from an area of tumour attachment to the dura matter (Figs. 8.44, 8.45). Vascular structures without any links to the site of initial tumour growth may be visualised in the meningioma tissue. They are mainly caused by the type of a tumour blood supply. This phenomenon is more often observed in cases of angiomatous and meningotheliomatous types (Figs. 8.46, 8.47).
Microcysts are visualised as round, point-like hypointensive sites on T1-weighted imaging, and hyperintensive, close to CSF on T2-weighted imaging (Fig. 8.48). Rarely, meningiomas may have unusual multicystic appearance on CT and MRI (Figs. 8.49–8.51). Calcifications are detected as hypointensive areas on T1-weighted imaging and T2-weighted imaging. Completely calcified meningiomas are observed in 10% of all cases. They are hypointensive in all sequence, but more obvious on T2- and T2*-weighted images (Figs. 8.52–8.54). Hyperpneumatisation of the paranasal sinus, and skull bones hyperostosis in an area of meningioma attachment may be better revealed with the use of CT rather than MRI (Fig. 8.55). Haemorrhages in the meningioma tissue, especially in subacute phase have typical MR signs; however, they are an exception rather than a rule (Martinez-Lange et al. 1991). In analyzing the data obtained in the course radiological diagnostics of the intracranial mass lesions, the neuroradiologist must find an answer to a very important question: is the
Fig. 8.44a,b Meningioma of the greater
wing of the sphenoid bone in the right side with extra- and intracranial spreading. MRI in the coronal projection on T2-weighted imaging (a) and T1-weighted imaging (b) detects a hyperintensive (on T2-weighted imaging) meningioma of a large size. The linear hypointensive sites in the form of radial rays that corresponds with the vascular tumour matrix are visible in the tumoural stroma (arrow)
746
Fig. 8.45a–i Meningioma (meningotheliomatous) of the right frontotemporal area. T2-weighted imaging (a,b), T1-weighted imaging before (c,d) and after (e,f) CE demonstrates a large tumour with
Chapter 8
well-detectable (especially after CE) vascular matrix. DSA (g–i): vascularisation of tumour is coming from the ophthalmic, middle meningeal, superficial temporal, and external maxillary arteries
Tumours of the Meninges
747
Fig. 8.46a–c Meningioma (meningotheliomatous) of the right frontal area. T2-weighted imaging (a), T1-weighted imaging before (b) and
after (c) CE demonstrates a large tumour with well-detectable hypertrophied vessels in its structure. There is perifocal oedema around the tumour. The tumoural vascular matrix is not revealed
Fig. 8.47a–f Meningioma of the anterior third of the falx cerebri.
CT with CE (a) reveals a large hyperdensive tumour with a cystic component, located behind the neoplasm. The tumour has a hyperintensive signal on MRI on T2-weighted imaging (b) and isointensive signal on T1-weighted imaging (c). The hypertrophied veins are
detected behind the tumour (arrows). The tumour intensively accumulates contrast medium (d). According to DSA (e,f), the tumour is supplied from the territories of the meningeal branches of the ECA and the ophthalmic artery
748
Chapter 8 Fig. 8.48a,b Meningioma of the left pari-
etal parasagittal area. T2-weighted imaging (a) and proton density–weighted imaging (b) reveal a isointensive (in comparison with the grey matter) mass lesion with the small intratumoural cyst (arrow)
Fig. 8.49a–f Meningioma of the left frontal convex area. CT with CE
(a,b) visualises the tumour of uneven structure, with cystic and solid components. T2-weighted imaging (c), T1-weighted imaging before (d) and after CE (e,f) demonstrate a tumour with mixed structure
and cystic components. The solid part of the meningioma accumulates contrast medium. Contrast accumulation is better revealed on MRI than on CT
Tumours of the Meninges
749
Fig. 8.50a–c Meningioma of the left parietal–convex area. T2weighted imaging (a) and T1 (b)-weighted imaging detect a heterogeneous tumour with solid and cystic components. The hyperintensive area on the periphery of the meningioma on T2-weighted imaging is caused by perifocal oedema. The tumoural tissue, cyst wall, and the adjacent dura matter actively accumulate contrast medium (c arrows)
750
Fig. 8.51a–i Meningioma (clear cell) of the left frontal parasagittal
area. CT series (a) with CE detect a mass lesion of multicystic structure. MR signals on T2-weighted imaging (b) and T1 (c)-weighted imaging are not typical for the meningioma. CE (d,e) improves the delimitation of the tumour from the brain tissue and facilitates the
Chapter 8
assessment of its structure. DSA (f–i) of the CCA territory demonstrates the blood supply from the branches of ICA and ECA, with the formation of a typical vascular matrix and intense “capillary spot” in the capillary phase
Tumours of the Meninges
751
Fig. 8.52a–d Meningioma (psammomatous) of the right posterior frontal–convex area.
T2-weighted imaging (a) and T1-weighted imaging (b) reveals a hypointensive (in all MR sequences) tumour. CE (c) leads to intense accumulation of contrast medium by the tumoural tissue on the periphery of the petrificate. The second, smaller meningioma node in the left frontal parasagittal area becomes clearly visualised. Tumours have a hypointense MR-Signal on DWI (d)
Fig. 8.53a–c Calcified meningioma of the left frontal parasagittal area. T2-weighted imaging (a) and T1-weighted imaging (b) reveals a hy-
pointensive (in all MR sequences) tumour. CE (c) leads to accumulation of contrast medium by the tumoural tissue on the periphery of the calcification
752
Chapter 8
Fig. 8.54a–f Calcified meningioma of the right frontal area. T2-weighted imaging (a,b), and T1-weighted imaging before (c,d) and after (e,f)
CE reveals a small hypointensive (in all MR sequences) tumour (better detected on T2-weighted imaging). The peripheral part of tumour slightly accumulates of CE
Fig. 8.55a–c Meningioma of the tuber of the sella turcica. T2-weighted imaging (a,b) and T1-weighted imaging (c) detects a mass lesion, which is isointensive with the surround brain tissue. The sphenoidal
sinus has increased pneumatisation; hyperostosis in the area of the meningioma matrix is blended with the hypointensive signal from the air in the paranasal sinus
Tumours of the Meninges
Fig. 8.56 The schema of the extra-axial tumour location
revealed neoplasm intra-axial or extra-axial? This is the basis for treatment selection and operational access planning. Our experience of complex use of CT and MRI in diagnostics of more than 5,000 patients with meningiomas demonstrated that MRI with a magnetic field of 1–1.5 T is a more effective method than CT is in identification of an extra-axial location of the lesion. Nevertheless, due to some technical aspects (the short time of CT examination), in an overwhelming majority of cases, we start from CT for the establishment of the preliminary diagnosis and for the visualisation of calcifications and the accompanying bone changes. There are several important criteria that help to demonstrate the extra-axial (in this case, tumour relation to the dura mater is not discussed) tumour location. The wide base adjoining to the dura matter is a frequent, however not obligatory, sign of a meningioma. Bone hyperostosis and/or bone invasion may be observed (Hamilton et al. 2006). However,
Fig. 8.57a–c Meningioma of the petroclival area growing into the
cavernous sinus. CT (a) with CE detects a hyperdensive tumour in the projection of the cavernous sinus and medial parts of the middle cranial fossa on the left, growing along the clivus and medial border
753
this is also an infrequent situation. The presence of anatomical structures located between a tumour and deformed brain tissue is a typical sign of an extra-axial tumour. There may be the vascular structures of the pia matter and the new formed vessels, fissure-like CSF spaces, and fragments of dura matter (Fig. 8.56). On MRT, these structures may be detected virtually in any case; however, sometimes not the whole contour. The dislocated vessels are visualised as point-like or coiled hypointensive areas and usually are well detected on the background of perifocal oedema on T2-weighted imaging. They may be both arterial and venous vessels. Dislocated vessels are most frequently revealed in cases of skull base tumour location, into the Sylvian or inter-hemispheric fissure. The fissure of CSF spaces on the tumour surface in the majority of observations (up to 70–80%) is revealed on the external contour of the tumour, it is hyperintensive on T2weighted imaging and hypointensive on T1-weighted imaging, and its signal characteristics do not differ from the distantly located CSF spaces (Figs. 8.57–8.59). It should be noted that the fissure around a tumour might not be detected in cases of atypical or anaplastic meningioma. As a rule, this is observed partially on the perimeter of the tumour contact. Perifocal oedema is especially intensive in these areas (Fig. 8.60). This may point to, albeit with not 100% reliability, invasive character of tumour growth. The dura matter on the surface of the tumour may be visualised in the form of a thin, hypointensive strip in cases of meningioma of the cavernous sinus. Sometimes it is possible to detect ruptures in the dura matter, with penetration of the filial tumour nodes through these ruptures. The same penetration of the meningioma through the duplication of the dura matter may be observed in cases of meningioma of the tentorium of cerebellum and falciform process (Figs. 8.61–8.63).
of the pyramid of temporal bone on the right. T2-weighted imaging (b) and T1-weighted imaging (c) demonstrates that the tumoural tissue is virtually isointensive to surrounding brain tissue. The CSF fissure sign (arrow) is observed on the lateral contour of the tumour
754
Fig. 8.58a–c Meningioma of the left parietal-parasagittal area. T2weighted imaging (a) and T1-weighted imaging (b) detect a small meningioma adjacent to the falx cerebri and partly to the wall of the
Chapter 8
superior sagittal sinus by the medial contour; the CSF fissure sign and accumulation of contrast medium in the neighbouring parts of the falx cerebri (tail sign) is observed (c)
Fig. 8.59a–f Meningioma of the left frontal area. T2-weighted imaging (a,b) and T1-weighted imaging (c,d) detect a small meningioma of
convex location. The CSF fissure sign is observed around the tumour. The adjacent gyri are partly compressed. CE emphasises the wide basis of the meningioma (e,f)
Tumours of the Meninges
755
Fig. 8.60a–c Malignant meningioma of the left temporal area. T2-weighted imaging (a) and T1-weighted imaging with CE (b,c) detect a mass lesion with intense accumulation of contrast medium and the wide attachment to the dura matter (the tail sign). The typi-
cal CSF fissure sign between tumour surface and adjacent brain tissue is absent. The prominent perifocal oedema around meningioma is observed
Such type of growth is not typical for a primary glial neoplasm. Metastatic tumours may have exophytic growth and cause the infiltration of the dura matter; however, in this case there are no visible CSF spaces and vascular formations between tumour and brain mentioned above. As it was noted before, MRI much better than CT reveals vessels in the stroma and on the surface of a meningioma. It is related to the fact that in CT examination after contrast administration, the tumour’s stroma and vessels equally accumulate contrast medium, whereas on MRI without CE the vascular structures (arteries and veins) have typical signal characteristics. Besides, even if a contrast medium was administrated intravenously, arteries with fast-moving blood remain darker on a background of the tumour that accumulated contrast substance. The signal from a vein on the meningioma’s periphery, as well as in case with CE CT using, is similar to a signal from tumour stroma. Currently, only CT perfusion examination may compete with MRI in accuracy of identification of the vascular formations around the meningioma. This method differentiates veins and arteries based on typical haemodynamical indicators detected during the bolus of CE (Fig. 8.64). In most cases, MRI exceeds CT in revealing a compression or invasive growth into the neighbouring brain tissue. Direct tumour invasion into adjoining venous sinuses is revealed due to narrowing or disappearance of a typical area of signal loss from the blood moving through the sinus, which occours due to compression or sinus invasion by a soft tissue component. The full obturation of the venous sinus is well detected also with use of CT (base on tumour invasion into the sinus’s lumen). Cerebral angiography identifies it due to the presence a nonfunctioning part of sinus (Fig. 8.65).
The occlusion of sagittal and transverse sinuses may be better detected on MRT in coronal projections, whereas a cavernous sinus is better visualised in coronal and axial images. Sometimes, the standard scanning in T1 and T2 sequences is sufficient for revealing meningioma tissue in the sinus lumen (Fig. 8.66); it is usually necessary to use CE (Fig. 8.67). Information more detailed about the state of a blood flow in a sinus may be obtained with the use of MRA and its modification with additional intravenous CE (Figs. 8.68, 8.69). MRA with the simultaneous visualisation of the arteries and veins reveals the tumour tissue on the background of the arterial and venous vessels. However, in our experience, MRA does not always give unequivocal answers about the tumour invasion into the lumen of the sinus or just compression of it by the tumour (Fig. 8.70, 8.71). In some cases, the analysis of raw angioscanning data and images obtaining in gradient echo may help to solve this problem (Fig. 8.72). The use of 3D TOF arteriography in meningioma diagnostics is mainly limited to the detection of the cerebral arteries dislocation, and only in rare cases, is it possible to identify the meningeal artery supplying the tumour (Figs. 8.73–8.75). Carefully performed CT or MRI even without CE may reveal the invasion of the dura matter, tentorium, the falciform process, or cavernous sinus by meningioma. But only MRI can detect the small soft tissue tumour components located in the bone marrow of the cranial vault (Figs. 8.76, 8.77). MRI is not as good as CT is in the identification of calcification into meningioma. Perifocal oedema is observed in patients with meningioma in more than half of all cases (Nakano et al. 2002). This frequently exceeds those observed with the help of CT examinations, whereas MRI, unlike CT, may easily detect even small peritumoural oedema. However, the presence of oedema and
756
Chapter 8
Fig. 8.61a–c Meningioma of the posterior third of the falx, predominantly on the right side. MRI with CE in the coronal (a), axial (b) projections detects a parasagittal meningioma in the right parietooccipital area, which accumulates contrast medium homogeneously.
The tumour is spreading through the falx cerebri into the opposite side. MRA (c) demonstrates the tumour’s image on the background of the completely obliterated superior sagittal sinus
Fig. 8.62a–c Meningioma of the tentorium of cerebellum with sub- and supratentorial growth. Series of axial CT images (a) and CT with the use of the sagittal (b) and coronal (c) reformations detects a large and widespread meningioma in the projection of the falx cerebelli angle
Tumours of the Meninges
Fig. 8.63a–c Meningioma of the tentorium of cerebellum with sub-
and supratentorial growth. T2-weighted imaging (a) and T1-weighted imaging (b,c) with CE detects a large and widespread meningioma
757
with wide infiltration of the free margin of the tentorium. The brainstem is compressed. Sagittal projection clarifies the tumour’s spread on the base of brain
Fig. 8.64a–f Meningioma of the right temporal area. T2-weighted imaging (a) and T1-weighted imaging (b,c) with CE detects a large meningioma with matrix and wide attachment. CT perfusion and maps (CBV) demonstrate the abundance of the arterial vessels scattered along the medial contour of the neoplasm (d–f)
758
Chapter 8 Fig. 8.65a,b Meningioma of posterior third
of the falx cereberi and torcular herophili. On DSA (a,b) visualisation of the posterior third of the superior sagittal sinus is absent because the lumen is completely filled by the tumoural tissue; the abundant blood supply from meningeal branches of ICA is found
Fig. 8.66a–c Parasagittal meningioma of the left parietal area. T2-weighted imaging (a), T1-weighted imaging before (b) and after (c) CE
reveals large and widespread meningioma of the flat type. The lumen of the superior sagittal sinus is completely occluded by the tumour
Fig. 8.67a–c The meningioma’s remains in the middle third of the superior sagittal sinus. T2-weighted imaging (a) and T1-weighted imaging with CE (b,c) detects a small tumour’s remain in the sinus lumen on the background of postoperational changes
Tumours of the Meninges
Fig. 8.68a–f Meningioma of the frontal–convex parasagittal location
in the left side. T2-weighted imaging (a), T1-weighted imaging with CE (b) reveals a cone-shaped meningioma, with hyperostosis in the area of the tumoural matrix. MRA with the use of 3D TOF technique
759
with CE and saturation of a signal from arteries demonstrates the meningioma location regarding the lumen of the superior sagittal sinus (c MIP processing, d–f 3D processing)
760
Chapter 8
Fig. 8.69a–c Meningioma of the middle third of the falx cerebri. MRI in the coronal projection on T1-weighted imaging before (a) and after (b) CE reveals the large meningioma on the level of the middle third of the falx cerebri to the right from the middle line. The lumen of the superior sagittal sinus is completely occluded by the tumour. MRA (c) in the oblique projection with the “suppression” of the artery detects an absence of the blood flow in the superior sagittal sinus on the level of the tumour
Tumours of the Meninges
Fig. 8.70a–f Parasagittal meningioma. T2-weighted imaging (a,b) and T1-weighted imaging (c) reveals a meningioma with homogeneous structure, located to the right from the falx cerebri and adjacent to the superior sagittal sinus. MRA with CE in the sagittal pro-
761
jection (MIP processing) does not enable estimating the degree of the superior sagittal sinus compression (d). MRA 3D reconstruction (e,f) clarifies the influence of the tumour to the sinus lumen—partial compression (arrow)
762
Chapter 8
Fig. 8.71a–f Parasagittal meningioma of the right side. T2-weighted imaging (a–d) visualises the small meningioma adjacent to the wall of the superior sagittal sinus. MR venography demonstrates the partial compression of the sinus lumen in the site of the tumour location (e,f)
Fig. 8.72a,b Parasagittal meningioma of
the right. T1-weighted imaging after CE (a) revea a small meningioma adjacent to the wall of the superior sagittal sinus. MRA (raw data) in the gradient echo sequence (b) demonstrates the absence of the tumoural invasion into the sinus lumen. The sinus wall is intact
Tumours of the Meninges
763
Fig. 8.73a–c Meningioma of the left wings and anterior clinoid process of the sphenoid bone. T2-weighted imaging (a,b) reveals a large tumour with isointensive MR signal. MRA (c) visualises only the dislocation of the MCA
Fig. 8.74a–c Meningioma of the olfactory fossa. T2-weighted imaging (a,b) reveals a large tumour, isointensive in the comparison with
the grey matter. The CSF fissure sign is clearly identified around the meningioma. MRA (c) visualises the arched, upward dislocation of the ACA
764
Chapter 8
Fig. 8.75a–c Meningioma of the greater wing of the sphenoid bone on the right. T1-weighted imaging with CE (a) reveals a very large tu-
mour, with intense and homogenous accumulation of contrast medium. MRA (b,c) visualises the dislocation of the MCA and hypertrophied medial meningeal artery that supplies the meningioma
Fig. 8.76a–c Infiltrative meningioma of the right parietal area. T1-weighted imaging before (a) and after (b,c) CE visualises the “mushrooming” meningioma, with signs of the hyperostosis of the internal bone lamella of the temporal bone and invasion to the bone marrow. The cystic component is medially located to the tumour
Tumours of the Meninges
Fig. 8.77a–f Infiltrative meningioma of the occipital parietal area.
CT with CE (a,b) reveals wide hyperostotic changes of the bone structures of the cranial vault in the parieto-occipital areas, with the invasion of the superior sagittal sinus and the intracranial soft tissue component. T2-weighted imaging (c) and T1-weighted imaging (d,e)
765
after CE visualises the tumoural tissue with wide spreading. MRA with CE demonstrates the absence of the blood flow in the posterior third of the superior sagittal sinus, with presence of the collateral ways of venous outflow formation through the veins of the occipital area (f)
766
Chapter 8 Fig. 8.78a,b Meningioma of the anterior
cranial fossa in the left side. T2-weighted imaging (a) and T1-weighted imaging (b) identifies a round meningioma, clearly outlined on the background of hyperintensive signal from the perifocal oedema
Fig. 8.79a–d Meningioma in the projection of the tuber of sella turcica and entrance
to the optic canal in the left. T2-weighted imaging (a–c) and FLAIR (d) detects a small tumour causing the partial deformation of the intracranial part of left optic nerve. Meningioma has the identical MR characteristics in all sequences and virtually is not distinguished from the brain tissue (arrows)
Tumours of the Meninges
767
Fig. 8.80a–c Parasagittal meningioma in the left side. T2-weighted imaging (a) detects a small meningioma, with attachment to the wall of the superior sagittal sinus. CE (b,c) clearly identifies the tumour on the background of surrounding brain structures
its intensity does not depend on the size of a tumour, and factors determining its appearance are actively discussed in literature. It is widely considered that oedema intensity to a certain extent depends on the histological type of a tumour. Therefore, moderate oedema is more typical for the meningotheliomatous, fibroblastic, and mixed-type meningiomas, whereas it is predominant for syncytial and angiomatous tumours. Malignant meningioma is almost always is accompanied by oedema (Daemerel et al. 1991). Interesting results were obtained by group of researchers headed by Tamiya (2001); they, based on multifactor analysis, demonstrated a high correlation between the presence of cortical–pial type of meningioma blood supply and signs of brain infiltration with intense perifocal oedematous reaction at these sites.
In those cases when meningioma is isointensive in comparison with white matter on T2-weighted imaging, it is usually well identified on a background of oedema (Fig. 8.78). Only in rare situations, especially in cases of the small meningioma of the wings of the sphenoid bone, the base of the anterior cranial fossa, and falx cerebri, are tumour contours poorly identified due to intense perifocal oedema. Isointensive meningiomas of small sizes can be easily omitted on standard MR images. CE is the method of choice in the visualisation of such meningiomas (Figs. 8.79–8.81). Meningioma may sometimes originate from cells of the vascular plexus of the lateral and fourth ventricle (extremely rarely from the third ventricle). The location in an area of the triangle is typical for them in the lateral ventricles. The MR at-
Fig. 8.81a–c Meningioma of the middle cranial fossa. T2-weighted imaging detects an area of hyperintensive signal in the medial part of
right temporal lobe close to the lateral wall of the cavernous sinus at the level of optic canal (b). CE (c) reveals a small meningioma with intense accumulation of contrast medium
768
tributes of these tumours are similar to meningiomas of other locations (Figs. 8.82, 8.83). Differential diagnosis of ventricle meningiomas should be performed with ependymomas and choroid papillomas. The latter are more frequently observed in children and young people, whereas meningiomas are observed in the middleaged and elderly. Usually, meningioma has even and round contours, while papilloma has lobular structure and uneven surface. Unlike meningioma, papilloma causes the dilation of the entire ventricular system, whereas in case of meningioma, only the part of ventricle close to tumour dilates. The reason is the occlusion of the part of the ventricle, due to a large-sized tumour in its lumen (in cases with meningiomas). The intense homogeneous contrast medium accumulation is a typical feature for virtually all meningiomas when MRI and CT are performed (Bydder et al. 1985; Felix 1985; Konovalov et al. 1985; Berry 1986; Fujii 1992; Gaydar et al. 2006). It is caused by the absence of blood–brain barrier in meningioma capillaries, typical for brain capillaries. Maximum contrast medium accumulation is achieved on the first series of postenhanced tomograms and decreases at 25–55 min. With the use of bolus CE dynamic scanning the highest level of contrast accumulation is observed within 1–2 min after intravenous injection, with subsequent gradual decrease of intensity within an hour or retaining enhancement, in the form of a plateau during the first 30–40 min (Figs. 8.84, 8.85). Our substantial experience in meningioma diagnostics with the use of CE leads us to conclude that decrease in dose of MR contrast medium to half of the standard (per kilogram) better estimates the internal tumour structure (Fig. 8.86). Nevertheless, it is necessary to note that this observation does not apply to CT with CE, or to cases of tumours with weak contrast accumulation in CT examination. Intravenous CE is a relatively informative method for revealing craniofacial meningioma and tumour of the optic nerve sheath. In the latter case, standard MRI may omit pathology, whereas after CE, the difference in signal intensity between the tumour and the optic nerve becomes clearer, especially with the use of a MR fat-saturation (“fat-sat”) technique (Fig. 8.87). CE also detects the small meningiomas of the cavernous sinus, which are poorly visualised on conventional scans. The sign of “the dural tail”—the additional CE of the dura matter around the tumour—is revealed in more than in half of all cases. The true nature of this phenomenon is still not clear. Some researchers consider that the tumour infiltration of the neighbouring dura matter is a reason (which requires its fuller surgical removal). Meanwhile, others insist that intense contrast medium accumulation is caused by the reactive changes (Aoki et al. 1990). According to our results, such type of CE in the dura matter is observed in more than 50% in cases of convex meningioma (Figs. 8.88, 8.89). The above-mentioned changes of the dura matter are not specific only for meningiomas; according to our and the literature data, they may be detected in cases of neurinoma, glioblastoma, and other malignant tumours adjoining the brain meninges. CE is an important tool in revealing meningioma remains
Chapter 8
after surgical intervention and tumour relapse on the background of postoperative changes. The dura matter and the tumour node usually show contrast medium accumulation. The meningioma in these situations is visible as an axial mass lesion, with intensive CE. Bolus CE dynamic scanning is a new approach in differential diagnosis of extra-axial neoplasms, which enables estimating the rate of contrast medium penetration into tumour tissue and the rate of its deposition into neoplasm (Fig. 8.90). This is especially important in diagnosis between meningioma and neurinoma in the posterior cranial fossa region. Unlike neurinomas, meningiomas in the overwhelming majority of cases accumulate contrast medium much faster. This difference may be detected only in the first 2 min after the start of scanning end enhancement. Then, the average level of CE tends to flatten in both cases of pathology (Fig. 8.91). However, almost any rule has exceptions, and the same is true of meningioma diagnostics. In our practice, we observe histologically typical meningotheliomatous meningioma that do not accumulate contrast medium at all (Fig. 8.92). The rapid development of new technologies in CT and MRI imaging, such as MRS, MR diffusion, and CT perfusion, visualise the structural elements of the meningioma from a new point of view, and allow quantitative analysis of microelements, and evaluation of the character of diffusion and haemodynamical changes in meningioma tissue and surrounding brain (Yamaguchi et al. 1997; Yang et al. 2003). 1 H MRS in cases of meningioma detects the Ala peak. The increase of the Cho peak, and the Lac–Lip complex peak is observed in combination with the Ala peak (Howe et al. 2003). The decreased NAA peak and high Glx peak form the so-called combined trapeziform complex (Fig. 9.93a). Some researchers find the decrease of the Cr peak in meningioma. This statement remains controversial, because the last metabolite is the most stable, and its changes in the meningioma spectrum are insignificant and not reliable. The presence of the NAA peak in the meningioma spectrum yet awaits its explanation, because this metabolite is a marker for neuronal cells and therefore, theoretically, should not be present in extra-axial tumours. Some researchers interpret it as a Glx complex (Majos et al. 2003). In general comparison with other tumours, the meningioma spectrum differs by the combination of high peaks of Cho, Glx, Lac–Lip, low NAA peak, and presence of an Ala peak (1.5 ppm); the latter is not detected in a spectrum of other lesions of neoplastic origin (Balakbashi et al. 2003). Among nontumoural lesions, the Ala peak is observed, for example, in a bacterial abscess spectrum. It is important to estimate the level of meningioma malignancy. But currently, there are no known specific markers for determination of each level of malignant transformation (Fig. 9.93). Although there are some reports that revealed a certain correlation between the level of malignancy and Cho and Lac peaks. DWI estimates the meningioma characteristics, depending more on the level of anaplasia to a greater extent than on spectroscopy, and it improves MRI effectiveness as a tool of differential diagnosis between meningioma and other tumours,
Tumours of the Meninges
Fig. 8.82a–i Intraventricular meningioma. DSA of the right CCA in
arterial (a,b) and venous (c) phases. The abundant blood supply from the hypertrophied anterior choroid artery and the occipital branch of the ECA is detected, as is the contrast spot of tumour that remains during the venous phase of the AG. CT with CE (d,e) reveals
769
a tumour with intense and homogeneous accumulation of contrast medium located in the projection of the triangle of the right lateral ventricle with extraventricular growth. T2-weighted imaging (f), T1weighted imaging before (g) and after (h,i) CE identify the tumour
770
Fig. 8.83a–i Intraventricular meningioma. DSA of the right CCA (a–c). The abundant blood supply from multiple arterial sources (MCA and anterior choroid artery) is detected. Contrast spot of the tumour appears in the late arterial phase and remains during the venous phase of the angiography (the “mother-in-law” sign). T2weighted imaging (d) and T1-weighted imaging with CE (e–g) reveal
Chapter 8
a tumour with intense and homogeneous accumulation of contrast medium located in the projection of the triangle of the right lateral ventricle. MRA (h,i) demonstrates the mass effect of the tumour to the cerebral arteries and also visualises the hypertrophied and atypically located anterior choroid artery that supplies the tumour
Tumours of the Meninges
Fig. 8.84a–i Meningioma of the torcular herophili. DSA (a,b) identifies the abundant vascular net with the supply from the hypertrophied meningeal branch of the right vertebral artery. Meningioma is slightly hyperintensive on T2-weighted imaging (c) and isointensive on T1-weighted imaging (d). Dynamic MRI examination per-
771
formed with bolus administration of the standard dose of contrast medium after 5 min (e), 20 min (f), 60 min (g), and 3 h (h) visualises the gradual decreased of the meningioma contrast accumulation in comparison with brain tissue. Sagittal MRI on T1-weighted imaging (i) reveals a small supratentorial growth of the tumour
772
Chapter 8
Fig. 8.85 A graph of the relative contrast accumulation curve of the meningioma after intravenous CE
Fig. 8.86a–c Convex meningioma of the right frontotemporal area. T2-weighted imaging (a) and T1-weighted imaging (b,c) detects a large tumour with microcystic changes in the medial part. The use of half dose of MR contrast medium was enough for identification of internal structure of the tumour
Tumours of the Meninges
Fig. 8.87a–f Atypical meningioma of the pterional area. CT (a) with
CE demonstrates the mass lesion, with wide bone destruction of the lateral wall of orbit and temporal bone in the left. T2-weighted imaging (b) and T1-weighted imaging before (c) and after (d,e) CE detect a tumour of the homogeneous structure and contrast accumulation,
773
with the soft tissue tumoural component of the intra-and extracranial spreading. The sequence with fat suppression (f) enables better estimation of the tumour’s spread than standard T1 sequence does. g–l see next page
774
Chapter 8
Fig. 8.87g-l (continued) The selective cerebral angiography of the ECA reveals (on the background of contrast passage into the ICA) the abundant blood supply of the meningioma from the branches of the maxillary artery (g–i). CT-perfusion maps (j–l) show heterogeneous intensely increased blood volume and flow parameters
Tumours of the Meninges
775
Fig. 8.88a–c Meningioma of the middle third of the falx cerebri. T1-weighted imaging before (a) and after (b,c) CE detects a tumour with
intense accumulation of contrast medium. The CE is seen spreading on the falx cerebri from anterior poles of the tumour (arrow)
Fig. 8.89a,b Meningioma of the middle and posterior third of the superior sagittal sinus. MRI before (a) and after (b) CE reveals a large
meningioma, which accumulates contrast medium and spreads on to the dura matter along the superior sagittal sinus
776
Chapter 8
Fig. 8.90a–e Meningioma of the petroclival area. MRI before (a),
after 16 s (b), 32 s (c), and 48 s (d) after bolus CE demonstrates the high rate of contrast medium accumulation in the tumoural tissue
that reflects the dynamic MRI by the appropriate signal increase. On the graph, there is a curve of signal intensity increasing, which is time-dependent (e)
Fig. 8.91 Graph of the comparison of the dynamic CE in
patients with meningioma of the pontocerebellar angle and neurinoma of the eighth cranial nerve. The difference in contrast medium accumulation between tumours become insignificant after 2–3 min after intravenous injection of contrast
Tumours of the Meninges
777
Fig. 8.92a–e Parasagittal meningioma. T2-weighted imaging (a), T1-weighted imaging before (b) and after (c,d) CE detects a mass lesion without contrast medium accumulation on the background of intense enhanced in the convex veins. MR venography (e) does not visualise the blood flow in the superior sagittal sinus in an area of the tumour location, but it does reveal dilated convex veins in the frontal areas
Fig. 8.93a–c MRS patterns of different degrees of malignancy of the supratentorial meningiomas: benign (a), atypical (b), and anaplastic types (c)
778
Chapter 8
Fig. 8.94a–f Benign meningioma of the greater wing of the left sphenoid bone. T2-weighted imaging (a) and T1-weighted imaging (b) detect a tumour that is slightly hyperintensive on T2-weighted imaging
and isointensive on T1-weighted imaging. After CE, the tumour signal became hyperintensive (c,d). The oedema is minimal; it is better identified on DWI (e,f)
especially with neurinoma, lymphoma, and glioma, which has certain practical value in neurosurgery (Filippi et al. 2001). In our series of patients with meningioma, the benign types prevailed (35 patients); the atypical forms (5 patients) and malignant tumours (7 patients) were observed more rarely. On DWI (b = 1000 s/mm2), benign meningioma has homogeneous, slightly hyperintensive or isointensive signal in comparison with non-affected brain tissue (Fig. 8.94). As a rule, the oedema has more intensive signal than tumour does on DWI (b = 500 s/mm2); it surrounds tumour and becomes invisible on DWI at b = 1000 s/mm2. On ADC maps, visually, meningioma does not differ from the white matter; however, in cases of perifocal oedema presence, the tumours are clearly visible on its background. In some cases, ADC maps clearly reveale the CSF fissure
sign as a thin, hyperintensive strip on a map between the meningioma capsule and surrounding structures. The average ADC values are 0.89 ± 0.13 × 10–3 mm2/s in a stroma of benign meningioma. Large meningiomas (larger than 4–5 cm) in 78% of cases have a vascular matrix detected in the centre of a tumour in T2 sequence. On ADC maps, these area have higher ADC values than the main stroma has, and appear in other colour ranges. Visually, the stromata of benign and atypical meningioma do not differ from each other (Fig. 8.95). Malignant meningiomas are characterised by signal heterogeneity on T2-weighted imaging; they are usually hypointensive on DWI (Fig. 8.96). They do not differ from white matter, or they may have fragmental insignificant difference according the colour range on ADC maps. As a rule, they
Tumours of the Meninges
Fig. 8.95a–f Atypical meningioma of the wing of the right sphenoid
bone. T2-weighted imaging (a) and T1-weighted imaging before (b) and after (c,d) CE demonstrate a large meningioma with solid structure and with homogeneous contrast medium accumulation. The tumoural stroma cannot be distinguished from the white matter by the
are surrounded by a wide area of perifocal oedema, which may be absent throughout. The haemorrhages in malignant meningiomas are identified on T1-weighted imaging and DWI as hyperintensive areas (due to T2 effect and diffusion decrease). Statistical analysis demonstrated that ADC in the stroma of malignant meningiomas (ADC = 0.97 ± 0.19 × 10–3 mm2/s) was different and higher than those of benign ones. According to our data, there is no significant difference between the atypical and benign meningiomas; the ADC value for these subgroups were 0.91 ± 0.16 × 10–3 and 0.83 ± 0.11 × 10–3 mm2/s, respectirely (Table 8.2). MRI and CT perfusion examination recently became one of the most important components in preoperative preparation and planning of operational access for meningioma removal,
779
signal characteristics on DWI (e,f). The central part of meningioma has structure more friable (vascular matrix) and higher ADC value. Peritumoural oedema is well identified on DWI b = 500 s/mm2 (e) and “go out” on DWI b = 1000 s/mm2 (f) and has high ADC value
especially for those meningiomas of basal locations (Kimura et al. 2006). The use of quantitative analysis of the perfusion tumour characteristics the preoperative stage enables evaluation of the meningioma blood supply, with high reliability (Figs. 8.97–8.99). Meningiomas with homogeneous contrast medium accumulation in standard CT examination have different blood flow distribution inside the tumour structure on the perfusion maps. Areas with intensively increased perfusion are clearly visible on a background of sites with moderately increased perfusion (Fig. 8.100). Information about such structural changes in a tumour avoids unexpected intraoperative haemorrhages, which may happen if examination was performed with the use of standard techniques. Moreover, the information about the CE curves characteristics on the perfusion maps helps to unmistakably identify arterial
780
Chapter 8
Fig. 8.96a–e Anaplastic meningioma of the right frontotemporal area, with prominent perifocal oedema. T2-weighted imaging (a,b), T1-weighted imaging after CE (c) demonstrates a meningioma of solid structure and with homogeneous contrast medium accumulation. The tumour has wide attachment to the dura matter. The tumour is hypointensive on DWI (d,e) in comparison with the benign types
Tumours of the Meninges
781
Table 8.2 ADC values for meningiomas a
–3
2
Types of meningioma
ADC value (× 10 mm /s)
Benign (n = 35)
0.83 ± 0.11
Atypical (n = 5)
0.91 ± 0.16
Anaplastic (n = 7)
0.97 ± 0.19
N = 47, r <0.05 a
Average value ± standard deviation
Fig. 8.97a–c Meningotheliomatous meningioma of the greater wing of the left sphenoid bone. CT with CE (a) detects a large tumour surrounded by the perifocal oedema. CT perfusion maps based on CBV (b) and on CBF (c) reveal high blood flow in the tumour
782
Fig 8.98a–f Meningioma of the greater wing of the right sphenoid
bone. CT after (a) CE shows the giant tumour of solid structure and with intense homogeneous contrast medium accumulation. CT perfusion maps on CBV (b), CBF (c), and МТТ (d) detect the uneven
Chapter 8
blood flow with the sites of high and average values. On DSA, the tumour is supplied from the middle meningeal artery and short branches of the siphon of the carotid artery (e,f)
Tumours of the Meninges
Fig. 8.99a–i Fibroblastic meningioma of the anterior third of the falx
cerebri. CT (a) and MRI on T1-weighted imaging (b,c) with CE identify a large tumour with the intense contrast medium accumulation. The tumour has small extracranial growths. In the wide attachment of the meningioma on the left, Pachioni granulations are observed.
783
MR venography does not reveal the narrowing of the superior sagittal sinus lumen (d). MR (e,f) and CT perfusion (g–i) demonstrate the moderate increase of blood flow in the tumour tissue. CT perfusion examination enables obtaining an image more qualitative than does MRI
784
Fig. 8.100a–f Meningotheliomatous meningioma of the olfactory
fossa. CT before (a) and after (b,c) CE detects a giant tumour of solid structure and with the intense contrast medium accumulation. CT
Chapter 8
perfusion maps: CBV (d), CBF (e), and МТТ (f) detect the heterogeneous and increased blood flow in the tumour. The sites of middle and high values of perfusion are revealed
Tumours of the Meninges
Fig. 8.101a–c Meningioma of the right temporal area. CT (a) and
MRI (b) with CE detect extra-axial tumour with wide attachment to the dura matter in the temporal area. CT perfusion with the recon-
and venous vessels, both on the periphery of the tumour as well as inside it. Many small arterial vessels were observed in the majority of our observations on the border of tumour–brain tissue in cases of infiltration of the adjoining brain surface by the tumour (Fig. 8.101). The important part of planning operational access to meningioma of the subtentorial area, and in particular, to the skull base, is the visualisation of the tumour matrix with help of CT perfusion (Fig. 8.102). Meningiomas are rarely observed in children; however, in these cases, they reach large sizes and mainly have supratentorial locations. Although CT and MRI characteristics of tumours are identical in children and adults in most cases, it is problematic to come to a conclusion about the meningothelial origin of a neoplasm (Figs: 8.103–8.105). Multiple meningioma (meningotheliomatosis) is a rare phenomenon. It is observed in cases of NF II type in children and adolescents in combination with the signs of the main disease, or as a independent lesion in adults (Sheehy and Crocard 1983). They compose from 1 to 10% of all meningiomas (Figs. 8.106, 8.107). In the majority of cases, radiological and MR diagnostics of meningiomas does not cause serious problems. Nevertheless, on occasions, there can be difficulties in its differentiation from neurinoma, anaplastic astrocytoma, tumours of the skull base with invasive growth, and metastases (most frequently, breast and colon cancers). Sometimes the cavernous angioma and capillary angioma affecting the dura matter and the cavernous sinuses may be similar to meningioma.
8.2
Non-Meningothelial Tumours
Primary mesenchymal tumours apart from meningioma are rarely observed. It is possible to single out bone–cartilage tu-
785
struction of the CBF (c) map identifies the increase of the blood flow in the tumoural tissue with the homogeneous distribution. The blood flow is the most intense in an area of the tumoural matrix
mours like osteoma and enchondroma among benign types of tumour and tumour-like processes. Osteoma is a benign tumour; it consists of cortical bone tissue, and its most frequent location is the frontal sinus (Haddad et al. 1997). Its radiological signs are rather typical: bone-like density on CT and homogeneously hypointensive (identical to the cortical bone) MR signal in all sequences (Fig. 8.108). Enchondroma is usually located in the area of the skull base (Dobert et al. 2002). The majority of these tumours are isointensive with the muscular tissue on T1-weighted imaging and hyperintensive in comparison with the same tissue on T2weighted imaging, with ring-like CE. Lipoma is not a “pure” brain tumour and in half of all observations, it is combined with other brain malformations (Truwitt and Barkovich 1990), which puts it in the group of the congenital CNS pathologies. It is accompanied by the calcifications, fibrous cords, and vessels that penetrate the lipoma. Lipoma is a rare phenomenon; its incidence is about 0.1– 0.5% of all primary brain tumours and reaches about 5% of all tumours located in the corpus callosum. Its preferred location is structures of the middle line, predominantly subtentorial (Rouhart 1992; Donati 1992). Appearance of lipoma has typical features for CT as well as for MRI. For lipoma, the decrease of density from –50 to –100 HU is characteristic on CT scans (Fig. 8.109). The MR image of lipoma is identical to that of subcutaneous fat. Lipoma has hyperintensive MR signal in T1 and T2 sequences. The fat-suppression technique may be used for more specific diagnosis (Figs. 8.110–8.112). Malignant mesenchymal neoplasm, as well as benign type of tumour is also a rare phenomenon. Hemangiopericytoma, chondrosarcoma, malignant fibrous histiocytoma, rhabdomyosarcoma, meningosarcoma, and others are included in such group. Meningosarcoma belongs to a group of polymorphocellular sarcomas. They originate from non-meningothelial cells.
786
Chapter 8
Fig. 8.102a–c Petroclival meningioma. CT before (a) and after (b) CE visualises the tumour of a solid structure with the intense contrast
medium accumulation. CT image in the perfusion sequence (c) demonstrates the vascular matrix of the meningioma (arrow)
Fig. 8.103a–e Meningioma of the middle
third of the falx cerebri and the superior sagittal sinus (a 13-year-old child). X-ray craniogram and CT series with CE (a,b) visualises the meningioma of uneven structure with the calcifications in its stroma. The meningioma is surrounded by perifocal oedema. DSA: meningioma is supplied from the branches of the ACA, ICA, and from the ECA (c). The tumour completely occludes the lumen of the superior sagittal sinus. The contrast spot of the tumour remains during the venous phase of the angiography (d,e)
Tumours of the Meninges
787
Fig. 8.104a–f Giant meningioma of the left frontotemporal area. Carotid angiography in coronal (a,b) and lateral (c) projections detects a significant dislocation of the ACA and MCA, with the presence of the multiple small arterial branches supplying the tumour. MRI series on T2-weighted imaging (d) visualises the meningioma of the uneven structure, and it significantly dislocates the ventricular system. CT series before (e) and after (f) CE shows the uneven structure and the heterogeneous contrast medium accumulation of the meningioma
788
Fig. 8.105a–f Malignant meningioma (a 9-year-old child). CT be-
fore (a) and after (b) CE detects a large neoplasm that causes the destruction of the frontal bone, which has intra- and extracranial spreading. There is large calcification in the tumoural tissue. MRI on
Chapter 8
T2-weighted imaging (c) and T1-weighted imaging (d) additionally reveals dilated blood vessels in the tumoural stroma and haemorrhagic foci. The tumour intensively accumulates contrast medium (e,f). g–h see next page
Tumours of the Meninges
789 Fig. 8.105g–h (continued) MRA (g,h)
demonstrates the dislocation of the cerebral vessels and the participation of the ACA in supplying the meningioma
Fig. 8.106a–f Multiple meningiomas. von Recklinghausen's disease (NF II). MRI series with CE (a–f) detects multiple tumoural nodes of the
infra- and supratentorial locations, with intense and homogeneous contrast medium accumulation
790
Fig. 8.107a–f Multiple meningiomas (meningotheliomatosis). Case 1. CT series with CE (a–c) identifies multiple tumoural nodes of the convex location with partial calcification in some of them. Case 2. CT series with CE (d–f) reveals multiple tumoural nodes of convex and intraventricular locations. The majority of meningiomas have this intense calcification
Chapter 8
Tumours of the Meninges
791
Fig. 8.108a–e Osteoma of the anterior cra-
nial fossa. CT (a,b) reveals a large tumour of bone density in the projection of the anterior cranial fossa and the cysts located behind it. The compact part of the tumour is hypointensive on MRI on T2-weighted imaging (c) and T1-weighted imaging (d,e). The cystic component contains a few isolated cysts with different concentration of the protein content
Fig. 8.109 Lipoma of the fissure of Sylvius. CT detects a hypodensive (up to –70 HU) mass lesion, surrounded on the medial contour by the calcification
792
Chapter 8
Fig. 8.110a–c Lipoma in the projection of the superior vermis of cerebellum. T2-weighted imaging (a) and T1-weighted imaging (b) detect a site of pathologically hyperintensive signal on T2- and T1-weighted imaging, with the characteristics that are typical for the fat tissue. Sagittal projection (c) clarifies the lipoma location
Fig. 8.111a–c Lipoma of the of the ambience cistern on the left. T2-weighted imaging (a) and T1-weighted imaging (b) detect a hyperintensive lesion with MR characteristics typical for fat tissue. Sagittal projection clarifies the lipoma location. Lipoma has hypointensive signal on DWI (c)
Tumours of the Meninges
793
Fig. 8.112a–c Lipoma of the fissure of Sylvius. MRI on T2-weighted imaging (a) and T1-weighted imaging (b) identifies the mass lesion, which has hyperintensive signal. The fat suppression technique detects a change of MR signal typical for the lipoma (c)
Their features are fast growth, wide invasion of the bone structures, and intense arterial (more often meningeal) blood supply. This makes them difficult for removal and they tend to haemorrhage during the operation (Fig. 8.113). Chondrosarcoma is a rarely observed tumour with invasive growth, and its most frequent location is the joint of the bones of the skull base; sometimes it affects the dura matter. It has the mixed signal on T1-weighted imaging and as rule, it has hyperintensive signal on T2-weighted imaging. The calcified structure of the tumour tissue is responsible for the heterogeneity of the signal characteristics and CE (Aoki et al. 1991; Meyers et al. 1992). Rhabdomyosarcoma belongs to a group of mesenchymal tumours, and it is often observed in children. About 35% of tumours affect the skull base and the area of cavernous sinuses. MR signs of rhabdomyosarcoma are not specific. T1-weighted imaging demonstrates isointensivity with muscle soft tissue tumour; rhabdomyosarcoma is heterogeneously hyperintensive on T2-weighted imaging (Figs. 8.114, 8.115). The fibrous histiocytoma is a rare type of a malignant nonmeningeal tumour. It originates from histiocytes, macrophage predecessors. Tumours more frequently are located in the dura matter; however, a parenchymatous location is also possible (Fig. 8.116). Ewing’s sarcoma is one of the most aggressive malignant tumours. Before the initiation of a system therapy, more than 90% of patients suffered from metastases. Their most frequent locations at the time of primary diagnostics are lung, bone, and bone marrow. Fourteen to 50% of patients already have metastases, revealed by the routine examination methods, and much more have the micrometastases. Spread through the lymphatic system is observed rarely, and it is always related to poor prognosis. Retroperitoneal and mediastinal metastases spread are also infrequent; 2.2% of all pa-
tients have metastases into the CNS by the time of the primary diagnosis, and almost all in cases of disease generalisation. Ewing’s sarcoma is the second most frequent malignant tumour in children, and its incidence is 10–15%. This tumour is rarely observed in children younger than 5 years old and in adults older than 30 years. The incidence peaks between 10 and 15 years. Histologically, Ewing’s sarcoma consists of small round cells with poor cytoplasm, a round nucleus that contains gentle chromatin, and poorly visible basophile nucleoles. Unlike osteosarcoma, it does not produce osteoid. There is a certain correlation between the appearance of Ewing’s sarcoma and the presence of the skeleton’s anomalies (enchondroma, aneurismal bone cysts, etc.) and anomalies of the urogenital system (hypospadias, reduplication of the renal system). Unlike osteosarcoma, there is no relation between preceding ionising radiation and Ewing’s sarcoma. X-ray examination is the quickest method of identification of bone metastases. Osteoscintigraphy with Te-99 and most recently, PET, reveals the full spectrum of lesions in bone, as multiple bone metastases are possible. CT is the method of choice for lung metastases detection. In cases of CNS lesions, CT and MRI reveal with the most precision the tumour size and its relation to the surrounding tissue, vessels, cranial nerves, its spreading and the character of the bone destruction, and bone marrow invasion (Fig. 8.117). Tumour trepanobiopsy, and also the aspiration biopsy or trepanobiopsy of the bone marrow from several places, is the final stage of the diagnosis (because Ewing’s sarcoma has tendency to spread into the bone marrow). Unfortunately, the radiological features are not pathognomonic. It is necessary to perform the differential diagnosis from other pathological processes in bones, such as osteomyelitis (first of all) and other malignant tumours of the non-
794
Chapter 8
Fig. 8.113 Meningosarcoma. MRI with CE identifies the giant tumour of the predominantly extracranial location, with the wide bone destruction and intense and uneven contrast medium accumulation
Fig. 8.114a–c Leiomyosarcoma (a 13-year-old child). T2-weighted imaging (a) and T1-weighted imaging (b,c) demonstrates a large tumour
in the projection of the anterior horn of the lateral ventricle, with signs of invasion of its wall
Tumours of the Meninges
Fig. 8.115a–f Leiomyosarcoma (a 7-year-old child). CT (a–c) after
CE. A tumour of uneven structure with a wide area of bone destruction and intra- and extracranial spreading is detected in the left
795
temporal–convex area. T2-weighted imaging (d,e) and T1-weighted imaging (f) adds information about spreading of the neoplasm with the predominantly extradural and extracranial location
Fig. 8.116a–c The malignant fibrous histiocytoma of the right pterional area. CT (a–c) after CE. A tumour of uneven structure with a wide
area of bone destruction and intra- and extracranial spreading (including the skull base) is detected in the left temporal-convex area
796
Chapter 8
Fig. 8.117a–d Ewing’s sarcoma. T2-weighted imaging (a), T1-weighted imaging before (b)
and after (c,d) CE. A mass lesion of the epidural location with the signs of bone marrow invasion is detected in the projection of the occipital bone. The torcular herophili underwent ventral dislocation
meningothelial origin (rhabdomyosarcoma, synovial sarcoma, neuroblastoma, lymphoma, etc). According to the WHO classification (2000), hemangiopericytoma belongs to tumours of the unknown origin; however, some researcher consider it histologically similar to angioblastic meningioma. There is an assumption that these tumours originates from pericytes, the cells surrounding capillaries (Parker 1991; Casentino 1993). Macroscopically, hemangiopericytoma resembles meningioma. The majority of such tumours are dense tumours with uneven surface, often well delimited, may infiltrate brain tissue, have wide attachment to the dura matter, and good vascularisation (Konovalov et al. 2005). Hemangiopericytoma is a rare tumour; its incidence is about 1% of all primary intracranial neoplasms. It is mainly observed in adults, and it prevails slightly in men (Guthrie 1989; Alen et al. 2001). Unlike meningioma, hemangiopericytoma tends to relapse and has metastases into other organs, especially to the lungs and bones. Five-year survival rate is no more than 40% of all operated patients. These tumours are relatively resistant to radiotherapy (Bastin 1992; Borg 1995; Dufour 1998). As a rule, hemangiopericytoma is supplied from the external and internal carotid arteries simultaneously (however, a separate blood supply may also be observed). It has an intense, heterogeneous vascular net that is well visualised to the
late capillary phase in DSA (Figs. 8.118, 8.119). Arteriovenous shunting and early drainage are not typical signs. On CT examination, it shows a heterogeneously hyperdensive pattern, without CE, and it prominently accumulates contrast medium, which emphasises the uneven structure of the neoplasm, mainly due to cysts and necrotic sites (Figs. 8.120–8.123). MR features of the hemangiopericytoma are varied. The heterogeneous tumour structure may be better demonstrated on T2-weighted imaging, whereas the tumour is virtually isointensive on T1-weighted imaging. Contrast medium accumulation is intense and uneven (Fig. 8.124). Large, pathological vessels may be frequently observed in the tumour stroma. CT perfusion examination demonstrates the extremely high blood flow in the stroma, with more heterogeneity in comparison with meningioma (Fig. 8.125). In the majority of cases with meningioma, diagnosis with the use of modern neuroimaging techniques like spiral CT and MRI does not have significant problems. In typical cases, the location of an extra-axial neoplasm may be easily identified, especially with the help of high-field MRI. The combination of CT and MRI answers practically all questions important for neurosurgeons concerning location, spreading, internal structure, and blood supply of the tumours of this histological category. The remaining questions about the preoperational histological differentiation of the meningioma subtypes, the
Tumours of the Meninges
Fig. 8.118a–f Hemangiopericytoma of the tentorium of cerebellum. Carotid angiography in the coronal (a–c) and lateral
(d,e) projections detects an intensely developed vascular net of the tumour with the supply from meningohypophyseal artery. Vertebral angiography demonstrates the arched dislocation of the PCA and the deviation of the superior segment of the basilar artery (f)
797
798
Fig. 8.119a–i Hemangiopericytoma of the anterior third of the falx cerebelli. CT with CE (a) detects a tumour of lobular structure with the intense contrast medium accumulation. Selective carotid angiography of the left ICA (b–d) and CCA in the lateral (e,f) and coronal (g,h) projections reveals an abundant blood supply of the tumour
Chapter 8
from the ophthalmic, fronto-polar arteries, and the ACA. The outflow goes to the anterior segment of the superior sagittal sinus. CE of the ECA does not reveal its participation in the supply of the tumour (i)
Tumours of the Meninges
799
Fig. 8.120a–c Hemangiopericytoma of the frontal area. CT (a–c) with CE identifies the large tumour of the anterior cranial fossa with intensely heterogeneous contrast medium accumulation, and there is a hypodensive area of the perifocal oedema around it
Fig. 8.121a–c Hemangiopericytoma of the left frontal area. CT with CE (a–c) detects a large tumour of the anterior cranial fossa with in-
tensely and uneven contrast medium accumulation
800
Chapter 8
Fig. 8.122a–c Hemangiopericytoma of the right occipito-parietal area. CT with CE (a–c) reveals a large tumour with intense and uneven
contrast medium accumulation and an area of bone destruction
Fig. 8.123a–f Hemangiopericytoma of the parieto-occipital area. CT before (a,b) and after (c,d) CE with the use of 3D reconstruction (e,f) demonstrates the giant tumour with the intensely and uneven contrast medium accumulation and the wide area of bone destruction
Tumours of the Meninges
Fig. 8.124a–f Hemangiopericytoma of the of the right occipital-
parietal area. CT before (a) and after (b,c) CE visualises the large intracranial tumour with relatively even contrast medium accumulation. MRI on T2-weighted imaging (d,e) visualises the dilated vessels
801
in the tumour. Perifocal oedema is minimal. The increased diffusion coefficient in comparison with the brain tissue is detected on the ADC map (f)
802
Chapter 8
Fig. 8.125a–c Hemangiopericytoma of the parietal area. CT with CE (a) detects a wide tumour of intra-extracranial location. CBV (b) and CBF (c) perfusion maps reveal the uneven, highly increased blood flow in the tumour
Fig. 8.126a–c Melanoma metastasis into the left parasagittal area. CT series with CE (a–c) identifies a round tumour adjacent to the falx cereberi from the left. Perifocal oedema is revealed around the tumour
level of the anaplasia of the tumour tissue, and the degree of the meningioma invasion into surrounding tissue, mainly the neighbouring brain structures, are still not resolved. As daily practice demonstrates, there are certain pitfalls in meningioma diagnosis (Louw et al. 1990; Khanna et al. 2006). Many neoplasms, according the CT and MRI data, may have
features similar to meningioma. In most cases, meningioma should be differentiated from metastases, lymphomas of the convex location, and even from intracranial tumours (for example ganglioglioma, oligodendroglioma, etc), sarcomatosis of the meninges, neurinoma of the caudal group of nerves, melanoma, and tumours of the skull base (Figs. 8.126–8.129).
Tumours of the Meninges
803
Fig. 8.127a–c Lymphoma of the right temporoparietal area. CT series with CE (a–c) detects a trapezium-shaped tumour widely adjacent to
the parietal bone. Prominent perifocal oedema is revealed around the tumour
Fig. 8.128a–f Lymphoma of the right temporal basal area. MRI on T2-weighted imaging (a,b) and T1-weighted imaging (c,d) reveals a large tumour that attached to the external wall of the right cavernous
sinus in the projection of the medial parts of the middle cranial fossa. T1-weighted imaging with CE (e,f) demonstrates the intense, homogeneous contrast medium accumulation in the tumoural tissue
804
Chapter 8
Fig. 8.129a–c Hemangioma of the medial parts of the right middle cranial fossa. T2-weighted imaging (a) and T1-weighted imaging before
(b) and after (c) CE reveals a large neoplasm of the homogeneous structure with MR features close to those of the meningioma
Refere n c e s Alen J еt al (2001) Intracranial hemangiopericytoma: study of 12 cases. Acta Neurochir (Vienna) 143:575–586 Aoki J, Sone S, Fujioka F (1991) MR of enchondroma and chondrosarcoma: rings and arcs of Gd-DTPA enhancement. J Comp Assist Tomogr 15:1011–1016 Aoki S, Sasaki Y, Machida T (1990) Contrast enhanced MR images in patients with meningiomas: importance of enhancement of the dura adjacent to the tumour. AJNR Am J Neuroradiol 11:935–938
Daemerel P, Wilms G, Lammeus M (1991) Intracranial meningiomas: correlation between MRI and histology in fifty patients. J Comp Assist Tomogr 15:45–51 Deen H, Sheithauer B, Ebersold M (1982) Clinical and pathological study of meningiomas of the first two decade of life. J Neurosurg 56:317 Dezamis E, Sanson M (2003) The molecular genetics of meningiomas and genotypic/phenotypic correlations. Rev Neurol (Paris), Sep;159(8-9):727-738 (Review)
Balakbashi N et al (2003) Combination of single-voxel proton magnetic resonance spectroscopy and apparent diffusion coefficient in evaluation of common brain tumours. AJNR Am J Neuroradiol 24:225–233
Dobert N et al (2002) Enchondroma: a benign osseous lesion with high F-18 FDG uptake. Clin Nuclear Med 10:695–697
Bastin K et al (1992) Meningeal hemangiopericytoma: defining the role for radiation therapy. J Neurooncol Nov;14(3):277-87 (Review)
Dufour H et al (1998) Meningeal hemangiopericytomas. A retrospective reciew of 20 cases. Neurochirurgie 44(1):5-18 (Review)
Berry I, Brant-Zawadzki M, Osaki L et al (1986) GD-DTPA in clinical MR of the brain. AJNR pp. 789-798 Borg M, Benjiamin CS (1995) Haemangiopericytoma of the central nervous system. Australas Radiol. Feb;39(1):36-41 (Review) Buetow M, Burton P, Smirniotopoulos J (1991) Typical, atypical and misleading features in meningioma. Radiographics 11:1087–1100 Burger P, Scheithauer B, Vogel F (1991) Surgical Pathology of the Nervous System and its Coverings. 3rd ed. New York, Churchill Livingstone, pp. 193-405 Bydder G M et al (1985) MR imaging of meningiomas including studies with and without gadolinium-DTPA. J Comput Assist Tomogr 9:690–697 Casentino C, Poulton T, Esquerra J (1993) Giant cranial hemangiopericytoma: MR and angiographic findings. AJNR, 14:253-256
Donati F, Vassella F, Kaiser G (1992) Intracranial lipomas. Neuropediatr 23:32-38.
Elster A еt al (1989) Meningiomas: MR and histopathological features. Radiology 170:857–862 Felix R еt al (1985) Brain tumours: MR imaging with gadolinium DTPA. Radiology 156:681–688 Filippi С еt al (2001) Appearance of meningiomas on diffusion weighted images: correlating diffusion constants with histopathologic functions. AJNR Am J Neuroradiol 22:65–72 Fujii K, Fijita N, Hirabuki N (1992) Neurinomas and meningiomas: evaluation of early enhancement with dynamic MRI. AJNR 13:1215-1220 Gaydar B, Rameshvily T, Trufanov G Parfenov V (2006) Ray Diagnostics of the brain and spine tumours. Foliant, St. Petersburg (in Russian) Guthrie B, Ebersold M, Scheithauer B (1989) Meningeal hemangiopericytoma: histopathologic features treatment and long-term follow up of 44 cases. Neurosurg 25:514-522
Tumours of the Meninges
805
Haddad F еt al (1997) Cranial osteomas: their classification and management. Report on a giant osteoma and review of literature. Surg Neurol 48:143–147
Naidich T (1990) Imaging evaluation of meningiomas: categorical course on CNS neoplasms. American Society of Neuroradiology, Oak Brook, Ill., pp 160–168
Hamilton B, Salzman K, Patel N (2006) Imaging and clinical characteristics of temporal bone meningioma. AJNR Am J Neuroradiol 27:2204–2209
Nakano T et al (2002) Meningiomas with brain edema: radiological characteristics on MRI and review of literature. Clin Imaging 26:243–249
Hope J, Armstrong D, Babyn P (1992) Primary meningeal tumours in children: correlation of clinical and CT findings with histologic type and prognosis. AJNR Am J Neuroradiol 13:1353–1364
Orrison W, Hart B (2000) Intraaxial brain tumors. In: Neuroimaging, W.B.Saunders company, Philadelphia pp. 583–611
Howe F et al (2003) Metabolic profiles of human brain tumours using quantitative in vivo 1H magnetic resonance spectroscopy. Magn Reson Med 49:223–232 Ildan F еt al (1999) Correlation of relationship of brain-tumor interfaces, magnetic resonance imaging and angiographic findings to predict cleavage of meningiomas. J Neurosurg 91:384-390 Kaplan R, Coon S, Drayer B (1992) MR characteristics of meningioma subtypes at 1.5 Tesla. J Comput Assist Tomogr 16:366-371 Khanna P, Godinho S, Patkar D et al (2006) MR spectroscopy-aided differentiation: “giant” extra-axial tuberculoma masquerading as meningioma. AJNR Am J Neuroradiol 27:1438–1440 Kimura H, Takeuchi H, Koshimoto Y et al (2006) Perfusion imaging of meningioma by using continuous arterial spin-labelling: comparison with dynamic susceptibility-weighted contrast-enhanced MR images and histopathologic features. AJNR Am J Neuroradiol 27:85–93 Kleihues P, Burger P, Scheithauer B (1993) The new WHO classification of brain tumours. Brain Pathol 3:255–268 Konovalov A, Kornienko V (1985) Computed tomography in the clinics of neurosurgery. Medicine, Moscow (in Russian) Konovalov A, Kornienko V, Pronin I (1997) Magnetic resonance imaging in neurosurgery. Moscow, «Vidar», pp. 427 (in Russian) Konovalov A et al (2005) Surgical removal of giant meningeal hemangiopericytoma. In: Kobayashi S (ed) Neurosurgery of complex vascular lesions and tumours. Thieme, Stuttgart, pp 244–248 Kornienko V, Ozerova V (1993) Pediatric neuroradiology. Medicine, Moscow (in Russian) Korshunov A et al (2002) DNA topoisomerase I-alpha and cyclin A immunoexpression in meningiomas and its prognostic significance: an analysis of 263 cases. Arch Pathol Lab Med 126:1079–1086 Kozlov AV (2001) Biology of meningiomas: current status. Zh Vopr Neirokhir Im N N Burdenko, Jan-Mar;(1):32-37; discussion 38 (Review, in Russian) Louw D, Sutherland G, Halliday W (1990) Meningiomas mimicking cerebral schwannoma. J Neurosurg 73:715–719 Majos C еt аl (2003) Utility of proton MR spectroscopy in diagnosis of radiologically atypical intracranial meningiomas. Neuroradiology 45:129–136 Martinez-Lage J, Poza M, Martinez M (1991) Meningiomas with haemorrhagic onset. Acta Neurochir (Vienna) 110:129–132 Meyers S, Hirsch W, Cutrin H (1992) Chondrosarcomas of the skull base: MRI features. Radiology 184:103–108
Osborn A (1994) Diagnostic Neuroradiology. Mosby-Year Book pp. 765 Osborn A (2004) Brain. Diagnostic Imaging. Amirsys pp. 936 Parker D, Rabinov J (1991) Recurrent meningeal hemangiopericytoma. AJR 156:1307-1313 Raksin P (2003) Imaging of meningiomas. Semin Neurosurg 14:3:193–201 Ray C, Nijensohn E, Advana V (1993) MRI and angiographic findings of a highly aggressive malignant meningioma. Clin Imaging 17:59-63 Rouhart F, Goas J, Neriot P (1992) Le lipome du corps calleux. Sem Hop. Paris 68:331-335 Russell DS, Rubinstein LS (1989) Pathology of Tumors of the Nervous System. 5-th. ed. Baltimore. Williams and Wilkins pp. 470 Sheehy J, Crocard H (1983) Multiple meningiomas: long term review. J Neurosurg 59:1–13 Spagnoli M, Goldberg H, Grossman R (1986) Intracranial meningiomas: high-field MR imaging. Radiology 161:369–375 Sheporaitis L, Osborn A, Smirniotopoulos J (1992) Radiologic pathologic correlation intracranial meningioma. AJNR Am J Neuroradiol 13:29–37 Sze G (1993) Diseases of the intracranial meninges: MR imaging features. AJR Am J Radiol 160:727–733 Tamiya T еt al (2001) Peritumoural brain oedema in intracranial meningiomas: effects of radiological and histological factors. Neurosurgery 49:1046–1051 Truwitt C, Barkovich A (1990) Pathogenesis of intracranial lipoma: an MR study in 42 patients. AJNR Am J Neuroradiol 11:669–674 Yamaguchi N еt al (1997) Prediction of consistency of meningiomas with preoperative magnetic resonance imaging. Surg Neurol 48:579–583 Yang S еt al (2003) Dynamic contrast-enhanced perfusion MR imaging measurements of endothelial permeability: differentiation between atypical and typical meningiomas. AJNR Am J Neuroradiol 24:1554–1559 Zachenhofer I, Wolfsberger S, Aichholzer M et al (2006) Gammaknife radiosurgery for cranial base meningiomas: experience of tumour control, clinical course and morbidity in a follow-up of more than 8 years. Clin Stud 58:1:28–36 Zimmerman R D et al (1985) Magnetic resonance imaging of meningiomas. AJNR Am J Neuroradiol 6:149–157
Chapter 9
Head Trauma
9
in collaboration with A. Potapov, A. Kravchuk, and N. Zaharova
9.1 9.2 9.3
Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 807 Primary Brain Injuries .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 808 Secondary Injuries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 869
9.1
Introduction
Head trauma is one of the most significant causes of disability and mortality in young and middle-aged people, and it is a major social and economic problem. According to epidemiological data, the incidence of head injury in moscow is 4.32 per 1000 population. In the U.S., 1.6 million traumatic brain injuries occur each year, 51000 U.S. citizens die each year from TBI (data of centers for Disease Control and Prevention, Report of Congress of the U.S.A., 2006). Car accidents, falls from height, assaults, etc. are the major causes of head injury. A mechanism of injury should be determined in every case of head injury, as well as the degree and severity of damage to brain and skull. If these factors are determined operatively, then many complications may be avoided, and many measures for salvage of brain tissue can be undertaken to prevent irreversible changes. Diagnostic equipment should work 24 h a day, 7 days a week in hospitals where the head injury is examined. X-ray craniography and CT are major diagnostic tools required for head injury diagnosis; if necessary, MRI and angiography should be available. The choice of tool depends on many factors including accessibility, speed, diagnostic yield, and, of course, patient condition. For instance, MRI examination of a patient with acute intracranial haemorrhage will take more time (including anaesthesiological manipulations) than will
modern spiral CT and fast multidetector spiral CT (FMCT). Delay in these procedures may cause many complications or even death. On the other hand, rapid craniography cannot reveal brain damage and may lead to delay in diagnosis. It is dangerous to assess severity of head injury (HI) according to presence or absence of fractures on routine craniograms, as the latter is ineffective for brain injury screening. Special attention is required when an adequate history is absent; however, it is not feasible to perform CT in every patient admitted with HI. Confusion, neurological deficit, penetrating brain injury, and a palpable impressed fracture, etc. are indications for CT. CT is a diagnostic tool of choice in acute HI. It is available, fast, and compatible with equipment for monitoring of vital functions and artificial ventilation. If image is spoiled by motion artefacts, then it is possible to repeat selectively several slices acquired on FMCT. The study acquires images in bone, soft tissue, and intermediate regimens (adequate to diagnose subdural haemorrhages) without CE to reveal parenchymal and meningeal injuries and bone fractures. We believe X-ray craniography may be circumvented if CT is accessible. MRI is an alternative examination technique that is more sensitive to brain lesions, especially of brainstem. MRI is an important component of the diagnostic complex in head trauma, as it shows a wider spectrum of traumatic changes (haemorrhagic and nonhaemorrhagic) than does CT. At present, MRI is performed in the subacute period, especially for patients in coma, and often in diffuse axonal injuries (DAI) and craniospinal trauma when clinical findings do not correspond to CT findings. To study abnormalities of signal on MRI, standard pulse sequences such as T1- and T2-weighted imaging in three planes are used as well as other pulse sequences. Despite the fact that T2-weighted imaging, spin echo sequence is the most applicable in HI, it has several drawbacks, among which are hyperintense signal of the CSF and high contrast between the grey and the white matter, which hampers identification of small injuries located close to the CSF pathways, as well as cortical and subcortical lesions. FLAIR images may help to overcome these drawbacks. FLAIR sequence has this property
808
due to attenuation of the CSF signal and to smoothening of contrast between the white and grey matter. FLAIR is more sensitive than Т2-weighted imaging for DAI, cortical contusions, subdural haemorrhages, and brainstem lesions, and it is the leading sequence in studying vasogenic oedema and gliosis in HI. Another sequence widely used in HI is Т2*-weighted gradient recall echo, which is sensitive to petechial haemorrhagic lesions and small haemosiderin deposits present for months and even years after injury. Sensitivity of this sequence is due to the diamagnetic properties of blood decay products. DWI is becoming more widely used in HI. Segmental axonal injury that changes diffusion anisotropy is typical for HI, especially for DAI. It was shown that DWI reveals hyperintense lesions in some cases and ADC reduction due to cytotoxic oedema, and in other cases, it reveals hyperintense lesions and increased ADC due to higher mobility of molecules in neuronal and glial alterations. Whereas CT and MRI are required to study macroscopic changes in HI, 1H MRS is a noninvasive technique used to study imbalance of chemical substances, such as NAA, Lac, Cho, and Cr. Clinical studies showed that Lac elevation may be found even in normal-looking tissue. Reduction of NAA level, reflecting neuronal alteration or decreased metabolism, may be seen in patients with high Lac 24 h after HI. In the subacute stage of DAI, reduction of the NAA peak or the NAA–Cr ratio in the white mater is observed. The combination of MRI and 1 H MRS shows condition and metabolism of tissues, which may be used to prognosticate clinical outcomes and changes in treatment and rehabilitation strategy. Functional neuroimaging can ascertain regional cerebral blood flow (by SPECT) or metabolism (PET). It obtains data about abnormal changes in those brain regions that look intact on MRI in head-injured patients. Perfusion CT and MRI are used for these purposes, which also give information about CBF, based on the analysis of how the contrast medium passes along the vascular net. Ultrasound is a portative and cheap technique that does not expose patients to radiation. However, if compared with CT and MRI, ultrasound is a less specific and sensitive technique in diagnosis of intracranial haemorrhages and ischaemic events. PET and SPECT are also less helpful for patients with acute HI, but may be successfully used in chronic stages. Their potential facilities are being studied at present in several clinics. Brain injuries are subdivided into primary and secondary. Primary injuries are brain contusions of different types, locations and severity, DAI or their combinations, intracerebral and meningeal haemorrhages, rupture of ependyma of cerebral ventricles, of subependymal veins, of the choroid plexus, of the pituitary infundibulum, and injuries of cranial nerves. Secondary injuries are brain oedema and swelling, impactions, ischaemic events and infarctions, formation of aneurysms, and arteriovenous fistules. According to the classification adopted by the Burdenko Neurosurgery Institute, HI is subdivided into “open” and “closed” in relation to intracerebral content and the risk of its infection. Closed head injury is that in which head skin
Chapter 9
integrity is preserved or wound of the soft tissues is present without damage to the aponeurosis. Cranial fractures without wounds of head soft tissues are related to closed HI. Open HI is that in which head soft tissue injuries are present with damage to aponeurosis, cranial fractures with wounds of adjacent tissues, or skull base fractures with nasal or ear bleeding or CSF leakage. If dura mater integrity is intact, then open HI is called “nonpenetrating”, if dura mater integrity is damaged open HI, then it is called “penetrating” (Lichterman 1998). Other authors subdivide HI into “open” and “closed” according to presence of dura mater damage (Cooper 1982; Grossman 1994; Castillo 2002).
9.2
Primary Brain Injuries
9.2.1 Cerebral Contusions Cerebral contusions are traditionally subdivided into “coup” and “contrecoup” (Figs. 9.1, 9.2), and according to location, into “cortical–subcortical” (Figs. 9.3, 9.4), “subcortical” (Fig. 9.5), “brainstem” (Fig. 9.6), and “mixed” (Fig. 9.7). In frontal lobe contusion, the brain moves above the rough margin of the anterior fossa internal bone lamina and impacts against the sphenoid bone wings and against ribs of the temporal bone pyramid. That is why contusions of frontobasilar, anteriotemporal, and laterotemporal areas (i.е. cortex around the Sylvian fissures) occur more frequently (Figs. 9.8, 9.9). Less often, parasagittal haemorrhagic lesions are seen in the dorsal parts of corpus callosum and brainstem (leading to perimesencephalic subarachnoid haemorrhage), posterior fossa, and other locations. It is noteworthy that within the first hours after HI, CT may be normal (in 20% of cases), and only several hours later traumatic lesions appear. The same is true for delayed haemorrhagic contusion lesions that occur 20–48 h after injury (Fig. 9.10).
Fig. 9.1 Haemorrhagic contusion in the left frontal lobe, compression of the homolateral ventricle, (axial CT) 7 days after HI
Head Trauma
809
Fig. 9.2a–c Contrecoup contusions in the right temporal and left inferior parietal areas. T2-weighted imaging (a) and T1-weighted imaging
(b,c), MRI 10 days after HI Fig. 9.3 Cerebral contusion in the right
frontal lobe of the cortical-subcortical location (CT) 7 days after HI
Fig. 9.4a–c Haemorrhagic cerebral contusions in the frontal-basal region: T1-weighted imaging (a) and T2-weighted imaging (b). CT (c) poorly visualises contusions (due to bone artefacts) 7 days after HI
810
Chapter 9
Fig. 9.5a–c Focal lesion in the right thalamus and basal ganglia, with blood extension into the lateral ventricles. CT 5 days after HI (a). Dy-
namic CT after 1 (b) and 2 (c) months demonstrates a hypodense area after lysis of haematoma Fig. 9.6a,b MRI on the second day after HI
visualises an area of changed signal from the acute microhaematoma in the projection of midbrain on the left
Fig. 9.7 Multiple contusions in the frontal–temporal region with
intracerebral and subdural haematomas. T1-weighted imaging and T2-weighted imaging 8 days after HI
Head Trauma
811
Fig. 9.8a,b Multiple haemorrhagic contu-
sions in the frontal and temporal regions. T2-weighted imaging (a) and T1-weighted imaging (b). Examination performed on the 4th day after HI
Fig. 9.9a–c Multiple haemorrhagic contusions in the frontal–temporal areas (subacute phase). T2-weighted imaging (a,b) and T1-weighted imaging (c) 9 days after HI
812
Chapter 9
Fig. 9.10a–i Dynamic CT series in severe HI. a–c First hours after injury, d–f 26 h later, g–i 3 days after injury. Haemorrhagic imbibition of
contusions in the left frontotemporal–basal region is observed on 3 days after injury
Head Trauma
813 Fig. 9.11a,b Type I contusion focus in the
left frontal region is visualised as lowdensity area with a minimal compression of the anterior horn of the left lateral ventricle (CT). a 1 day after HI, b after 2.5 months— no pathological changes in this area are marked
Fig. 9.12a–c Multiple haemorrhagic contusions in the right frontal–temporal region (type II contusion). Severe HI. a Axial CT, b,c 3D re-
construction
Acute contusions (less than 12 h) may be classified according to CT and MRI features into the following groups: • Hypodense on CТ and hyperintense on MRI (Т2-weighted imaging): type I (Fig. 9.11) • Mixed density on CT and heterogeneous signal on MRI, haemorrhagic areas: type II (Figs. 9.12, 9.13) • Intracerebral haemorrhage with mixed density on CT and hyperintense signal on MRI in adjacent brain tissue: type III (Figs. 9.14–9.16) It should be remembered that a type I contusion may transform into types II and III, and type II into type III. That is why in acute HI, the dynamic clinical examination and CT are required (Kornienko et al. 1987; Lebedev et al. 1998). In the acute stage, hyperdensity on CT (50–70 HU) is due to high protein content in intact erythrocytes (Fig. 9.17). MRI is less sensitive than CT is in the superacute stage, as amagnetic intracellular oxyhaemoglobin does not have unpaired electrons, and the
signal of the blood clot is practically identical to that brain tissue, i.e. it is mildly hypointense on T1-weighted imaging and mildly hyperintense on T2-weighted imaging. Dynamic study gives additional information about the size of haemorrhage and its volume if delayed haemorrhage or vasogenic oedema is present. Contusions of soft tissues, subdural haemorrhages (often communicating with parenchymal haemorrhage), subarachnoid and intraventricular haemorrhages, fractures of skull bones (Fig. 9.18) and, finally, multiple haemorrhages (Figs. 9.19, 9.20), can also be present. Acute haemorrhagic contusion lesions (less than 3 days since injury) mainly contain paramagnetic intracellular deoxyhaemoglobin formed after dissociation of haemoglobin and oxygen. As deoxyhaemoglobin does not shorten Т1, haemorrhagic contusions have normal and mildly hypointense signal in this sequence. High content of erythrocytes and fibrin in a clot shortens Т2 and leads to hypointense signal on T2 and Т2*-weighted imaging.
814
Chapter 9
Fig. 9.13a–c Acute bilateral haemorrhagic contusion in both frontal lobes (type II). Moderate HI. T1-weighted imaging (a), T2-weighted imaging (b) and FLAIR (c)
Fig. 9.14a–c Multiple haemorrhagic contusions. Severe HI (7 days after injury). Axial CT (a), T2-weighted imaging (b) and T1-weighted MR-imaging (c)
Head Trauma
815
Fig. 9.15a–c Cerebral contusions, type III (10 days after HI) are visualised on axial CT (a) and T1-weighted imaging (b) and T2-weighted MR-imaging (c)
Fig. 9.16a–c Cerebral contusion, type III. CT (a), T1-weighted imaging (b), and T2-weighted MR-imaging (c) visualise the haemorrhagic area
of the brain lesion in the left frontal region. There are smaller contusions in the right frontal area
816
Fig. 9.17a–f Dynamic CT of cerebral contusions (type III). a Five days after injury, b the 9th day, c the 16th
day, d the 23rd day, e the 30 day, f after 1.5 months. CT demonstrates the gradual lysis of the haemorrhagic component with the straightening of the ventricles
Chapter 9
Head Trauma
817
Fig. 9.18a–i Dynamic CT series of the contusion (type III) in the right parietal lobe with blood extension into the lateral ventricle (CT before (a–c) and after (d–i) surgery)
818
Chapter 9
Head Trauma
9 Fig. 9.19a–o Dynamic FLAIR, T1-weighted imaging, and T2-weighted imaging (MRI), respectively (left to right in figure parts), of frontal lobes contusions 2 (a–c), 4 (d–f), 7 (g–i), 14 (j–l) and 17 (m–o) days after injury
819
820
Chapter 9
Fig. 9.20a–f Multiple cerebral contusions in both hemispheres with damage of the corpus callosum (DAI): T2-weighted imaging (a–c) and
FLAIR (d–f) MRI
Fig. 9.21a–c Severe HI (5 days after trauma). a CT and b FLAIR MRI show haemorrhagic lesions in the midbrain and left frontal–temporal
region. CT perfusion (c CBF map) reveals decrease of the blood flow in the left frontal lobe
Head Trauma
Several days later, subacute contusion lesion starts to attenuate, and vasogenic oedema develops and is enlarged within the first week and may lead to impactions. It looks hypointense on T1-weighted imaging and hyperintense on T2-weighted imaging. When deoxyhaemoglobin transforms into intracellular paramagnetic methaemoglobin, the interaction between protons and paramagnetic centres of methaemoglobin leads to hyperintense signal on T1-weighted imaging, which initially appears on the contusion lesion periphery. Intracellular methaemoglobin is characterised by hypointense signal on T2-weighted imaging. After rupture of membranes of erythrocytes and migration of methaemoglobin into the intracellular space (subacute haemorrhage), MRI reveals change of haematoma—hyperintense signal of extracellular methaemoglobin appears on Т1- and Т2-weighted imaging. Novel vessels at the lesion periphery do not have tight endothelial connections, as in intact blood–brain barrier, which is why accumulation of contrast medium may be seen at the lesion periphery on CT and MRI, and vessels of fragile granulation tissue are predisposed to repeated haemorrhages. At the same time, CT shows decreased density of contusion lesion and mass effect due to reduction of oedema. Peripheral rims of haemosiderin and ferritin are mildly hypointense on T1-weighted imaging and markedly hypointense on T2-weighted imaging, which is a hallmark to lesion transition into the chronic stage. Blood clot resorption starts from the centre to the periphery and depends on the size of haemorrhage. Duration of this process may vary from one to several weeks. New achievements in studying cerebral blood flow appeared when the CT perfusion technique was introduced. It is a noninvasive method of mapping regional cerebral blood flow. In the acute stage, CT perfusion findings are used to identify areas of oligemia, ischaemia, infarctions, and hyperaemia (Fig. 9.21) (Wintermark et al. 2004).
9.2.2 Diffuse Axonal Injuries DAI is one of the most frequent primary brain injuries in severe HI. The damage is produced by the rotational forces of shear, acceleration, and breaking, resulting in displacement of grey and the white matter (they have different density). This is why the term shear injury is used. This shearing leads to rupture of axons and their swelling and impairment of axoplasmic flow. Axonal rupture may be incompletely (partial) marked on the microscopic level and complete in combination with acute haemorrhage from ruptured capillaries. Severe DAI leads to coma and unfavourable outcome in half of cases with this injury. Factors of poor prognosis are low scores on the Glasgow coma scale, concomitant acute nonhaemorrhagic and haemorrhagic lesions of brainstem, corpus callosum, and combined haemorrhagic and nonhaemorrhagic lesions such as subdural haemorrhages and contusions. Distribution of damage points along the white matter tracts is typical for DAI. About two thirds of lesions are found in the white matter at the junction of grey and white matter in the frontoparasagittal region,
821
temporoperiventricular region, less frequently in parietal and occipital regions (Figs 9.22). The corpus callosum is always affected, especially its splenium and posterior portions of its corpus (Figs 9.23, 9.24). If intraventricular haemorrhage is present, then involvement of corpus callosum should be suspected, with concomitant damage to subependymal capillaries along the ventricular surface of corpus callosum, fornix and septum pellucidum (Fig. 9.25). Traumatic lesions of thalamus and basal ganglia are relatively uncommon. In DAI, rupture of small perforans vessels is frequently seen. Sometimes lesions are found in the internal and external capsules (Fig. 9.26). Brainstem DAI lesions are classically located in the dorsolateral portions of midbrain and superior pons. Some tracts are most frequently affected: superior cerebellar peduncles and medial lemniscus; cerebral peduncles are also often involved (Figs. 9.27–9.30). If brainstem is affected, then lesions are usually found in the white matter (of cerebral lobes) and corpus callosum (Fig. 9.31). If no abnormal changes are revealed, then diagnosis of DAI should be made cautiously, as transtentorial herniation may lead to secondary brainstem damage or mass effect in the posterior fossa. Low Glasgow coma scale scores persist in patients with HI and DAI, which may mean involvement of the brainstem structures. On CT, no abnormal changes are usually seen or haemorrhagic areas are present in DAI patients (Fig. 9.32). Basal cisterns are usually poorly visualised after brainstem injury, due to diffuse brain oedema (Fig. 9.33). MRI provides better examinations of the brainstem, as it is more sensitive for nonhaemorrhagic lesions and less biased by artefacts of the posterior fossa. Frequently, combinations of DAI and subarachnoid haemorrhages, contusions, meningeal, and intraventricular haemorrhages are diagnosed (Figs. 9.34, 9.35). If complete ruptures of axons occur, then petechial haemorrhages 0.5–1.5 mm in size are seen on CT in 20–50% of cases. Petechiae are encircled by hypodense oedema. Large haemorrhages are better seen on CT scans performed in later periods. In acute nonhaemorrhagic DAI, small areas of oedema that have hypointense signal on T1-weighted imaging and hyperintense on T2-weighted imaging may be seen on MRI. Several days later haemorrhagic lesions may appear in a nonhaemorrhagic lesion. It appears as a hyperintense lesion on T1-weighted imaging and hypointense lesion on T2-weighted imaging, which reflects intracellular methaemoglobin transformation into extracellular methaemoglobin with typical characteristics (bright signal on Т1- and T2-weighted imaging). The lesion of acute haemorrhagic DAI (deoxyhaemoglobin) is isointense to adjacent brain tissue on T1-weighted imaging and hypointense on T2-weighted imaging (Fig. 9.36). MRI identifies DAI better than CT does (Jinson et al. 2001), especially when DAI reaches the stage of oedema and haemorrhage, or haemorrhage in the methaemoglobin phase is present (the subacute period). T2-weighted imaging and FLAIR images are especially sensitive when detecting axonal injuries (lesions are hyperintense), whereas they are iso- or hypointense on T1-weighted imaging (Fig. 9.37). Acute and subacute nonhaemorrhagic le-
822
Chapter 9
Fig. 9.22a–f Diffuse axonal injury in patient with severe HI. CT (a–c) and T1-weighted imaging (d,e) and T2-weighted MR-imaging (f) reveal
multiple subcortical haemorrhagic lesions, corpus callosum and brainstem damages
Fig. 9.23a–c Diffuse axonal injury. T1-weighted imaging (a), T2-weighted imaging (b) and DWI (c) MRI reveal lesion in the splenium of corpus callosum, which is better detected on DWI
Head Trauma
823
Fig. 9.24a–c Diffuse axonal injury with the haematoma in the corpus callosum. T2-weighted imaging (a) T2-weighted MR-imaging (b,c)
Fig. 9.25a–d Severe HI, DAI. Acute haema-
toma in the projection of the corpus callosum, blood extension into lateral ventricles. Isointense signal on T1-weighted imaging (a), hypointense on T2-weighted imaging (b–d) and DWI (e) show acute haematoma (presence of deoxyhaemoglobin)
824
Chapter 9
Fig. 9.26a–c DAI in patient with severe HI. T1-weighted MR-imaging (a,b) and T2-weighted MR-imaging (c) show involvement of the cor-
pus callosum, external capsule, and thalamus Fig. 9.27 DAI. MRI demonstrates brain-
stem lesion at the cerebral peduncle level
Fig. 9.28 DAI. T2-weighted MR-imaging
shows multiple lesions in cortical–subcortical structures and in the left cerebral peduncle
Head Trauma
825
Fig. 9.29a–c DAI. Haemorrhagic lesion in the projection of the left superior cerebellum peduncle and upper aspect of pons. The haemor-
rhagic component is hyperintense on T1-weighted imaging (a); FLAIR MRI (c) better than T2-weighted imaging (b) visualises the lesions in temporal lobes
Fig. 9.30a–d DAI (2 days after injury). T2-weighted imaging (a), T2-weighted imaging (b), FLAIR (c), and DWI (d) MRI reveal the bilateral areas of the signal change in the projection of the midbrain
826
Chapter 9 Fig. 9.31a,b DAI. T1-weighted imaging (a)
and FLAIR (b) MRI show haemorrhagic lesions in the brain stem, grey–white junctions and corpus callosum
Fig. 9.32a–d DAI. Dynamic CT on the fourth day after HI (a,b) and 1 month after injury
(c,d). Signs of diffuse brain atrophy are observed
Head Trauma
827
Fig. 9.33a,b Diffuse brain oedema with compression of basal cisterns, third ventricle, and subarachnoid spaces in patient with severe HI.
Dynamic CT. a Acute stage, b 2 weeks later—regression of the oedema and compression of the CSF spaces
Fig. 9.34a–c DAI. Combination of temporal lobe contusion, lesion of the corpus callosum and subdural haematoma. T1-weighted imaging
(a), FLAIR (b), and DWI (c) MRI
828
Chapter 9
Fig. 9.35a–c DAI. T1-weighted imaging (a), T2-weighted imaging (b), and FLAIR (c) MRI show multiple lesions in the corpus callosum, head of the caudate nucleus, and subdural and subgaleal haematomas
Fig. 9.36a–c DAI. T2-weighted imaging (a), FLAIR (b), and DWI (c) MRI reveal lesions in the corpus callosum and acute subependymal microhaemorrhages
Head Trauma
829
Fig. 9.37a–c DAI in a patient with severe HI. T1-weighted imaging (a), T2-weighted imaging (b), and FLAIR (c) MRI detect lesions in the corpus callosum and right thalamus. Acute haemorrhages are hypointense in all sequences
sions are hyperintense on DWI (Fig. 9.38), and have low ADC values, represented by cytotoxic oedema. Diffusion of water molecules in the brain is restricted by myelinated axons in the white matter. Diffusion along the fibres is significantly higher, and local axonal injury, for instance, in corpus callosum may cause change in diffusion anisotropy (Kuzma and Goodman 2000). Secondary Wallerian degeneration is also seen in axonal rupture and may cause diffuse degeneration and atrophy of axons months and years later. Histological study of DAI lesions showed that reactive disorganisation of intercellular connections occurred, causing
Fig. 9.38 DAI in the acute phase. DWI (b = 500) demonstrates the
hyperintense area in the corpus callosum
impairment of osmolar equilibrium and cell death (Gentleman et al. 1995). To assess the degree severity of brain damage we used 1 H MRS, which identifies in vivo neurochemical changes of such metabolites as Cr, Cho, mI, NAA, and Lac in the selected tissue volume. After 1H MRS examination of DAI lesions, special attention is paid to changes of NAA, Lac, and Cho peaks in relation to the Cr peak. One of the NAA functions is to support the osmolar status. In addition, NAA is a donor of acetyl groups, which are responsible for protein synthesis during myelination. Irrespective of the functional peculiarities of NAA, this metabolite is exclusively synthesised in neuronal mitochondria, which allows calling it a “neuronal marker”. Brain damage accompanied by neuron mass loss is manifested by decrease of NAA content in the examined brain tissue. MRI is capable of revealing change in the NAA level not only in the lesion, but also in the brainstem, subcortical white matter, and basal ganglia. This phenomenon may be explained by widespread DAI. Decrease of the NAA peak is seen in the spectrum of the DAI lesion compared with intact brain tissue. In several cases, the Lac peak may be seen, thus reflecting activation of anaerobic glycolysis due to hypoxia and ischaemia. If an increase in Cho peak is seen, then it means cell loss in the damage area and destruction of cell membranes with release of Cho-containing components in a lesion (Kuzma et al. 2000; Sinson et al. 2001). We studied changes of ratios between metabolite peaks and compared them with patient condition, assessed by the Glasgow coma scale. MRI was performed 4 and 20 days after injury. In cases of favourable outcome, NAA peak decrease was observed at first examination alongside a mild Cho peak and Lac peak increase; on day 20, the NAA peak almost reached normal state; the Lac peak decreased (Fig. 9.39). It may be explained by absence of irreversible changes, impairment of intercellular connections, and massive cell loss.
830
Chapter 9
Fig. 9.39a–c DAI, lesion in splenium of the corpus callosum (a), favourable clinical outcome. In comparison with findings of the initial examination performed at time of acute HI stage (b), dynamic MRS reveals restoration of the NAA peak and disappearance of the Lac peak (c)
Fig. 9.40a–c DAI, unfavourable clinical outcome. Dynamic MRS reveals decrease of the NAA peak and appearance of the Lac peak com-
pared with the initial examination
Head Trauma
In unfavourable outcomes, only a moderate decrease of NAA peak was initially seen. On day 20 the NAA peak was decreased, the Lac peak appeared, and the Cho peak increased (Fig. 9.40). Such a spectrum means that hypoxia, ischaemic changes, cell loss with membrane destruction (i.e. irreversible changes) are present. The NAA–Cr ratio is a significant prognostic marker in patients with head trauma in the first 24 h after injury. Analysis of 24 patients treated in the Institute showed that in favourable outcomes, this ratio was 1.58 ± 0.32, and in severe neurological deficit it was 1.27 ± 0.24. Thus, study of 1H MRS in head-injured patients is an important and useful technique for diagnosis and prognosis. In 2001, Firsсhing et al. proposed classification of traumatic brain lesions based on MRI findings. Using their own material they showed that there existed a correlation between survival, disability, and level of brainstem damage: • Grade I Supratentorial lesions only • Grade II Unilateral brainstem lesions at any level ± I • Grade III Bilateral brainstem lesions on the mesencephalic level ± I • Grade IV Bilateral lesions of the pons ± any of the foregoing lesions of lesser grades Dynamic MRI of HI patients treated in the Institute demonstrated a clear correlation between degree of confusion (according to the Glasgow coma scale), level of brain damage, and outcome, which was confirmed by several other studies (Mannion 2007). Unfortunately, routine MRI does not allow completel assessment of DAI, as real size of involvement in DAI is much larger. Size of DAI on autopsy always exceeds that of routine neuroimaging, including MRI; DAI is found in 80–100% of all fatal outcomes in HI patients. New possibilities in the study of primary ultrastructural changes, especially in DAI, can be provided by diffusion tensor imaging and tractography; they visualise in vivo white matter anatomy based on diffusion anisotropy changes and acquire 2D and 3D images (Arfanakis et al. 2002; Wilde et al. 2006; Yasokawa 2007). It is possible to compare clinical picture and morphology completely, i.e. DTI gives an opportunity to reveal those affected brain structures that look intact on routine MRI (Т1- and Т2-weighted and FLAIR images) (Fig. 9.41).
9.2.3 Intracranial Haemorrhages 9.2.3.1
Subdural Haematomas
Subdural haematomas with or without contusion lesions are the most frequently seen extracerebral traumatic injury, often leading to fatal outcomes. According to statistics, they account for 10–20% of cases in specialised clinics and up to 30% in autopsies. Blood is accumulated between dura mater and arachnoid membrane. Subdural haematoma may cross sutures, falx, or tentorium. Subdural haematoma is frequently caused by traumatic rupture of cortical veins at the brain base in temporal lobes, sphenoparietal, or petrous sinuses. However, rupture of superficial veins and the superior longitudinal sinus is also
831
a frequent cause. Among other causes, vascular abnormalities (dural fistules) and marked cortical atrophy should be mentioned. Subdural haematomas are rarely combined with skull fractures in adults, but accompanied by subarachnoid haemorrhages in approximately 70% of patients. By the time of onset of clinical symptoms, subdural haematomas are classified into acute, subacute, and chronic, and each of them is characterised by a certain CT pictures. On CT acute subdural haematomas (less than 2–3 days) may be hyperdensive (60%), may have mixed density (active bleeding or rupture of the arachnoid membrane, 40%), or may be isodensive (rarely, if a patient has coagulopathy or anaemia, Hb < 8–10). A typical picture for acute subdural haematoma on CT is hyperdensive accumulation between the cerebral hemisphere and the internal cranial bone lamina, extending from the frontal region backwards around the hemisphere (Fig. 9.42). If haemorrhage is massive, then mass effect is frequently seen, which causes midline shift, homolateral compression of the lateral ventricle, and contralateral ventricle enlargement. Acute subdural haematomas may be rarely iso- or hypodensive due to anaemia and low haemoglobin and when CSF leakage is caused by rupture of the arachnoid membrane. In this case, the CT picture may be typical for subacute subdural haematoma. It should be remembered that right and left subdural spaces are separated by the inferior sagittal sinus and falx. Rupture of veins feeding the superior sagittal sinus leads to accumulation of blood in the subdural space along one falx side. The medial haematoma edge is linear, the lateral is convex, and it causes midline shift. Inter-hemispheric haematoma is more frequently seen in children. Haematomas may accumulate in subdural spaces along tentorium. Supratentorial extracerebral blood accumulations are more often subdural, less frequently epidural, and infratentorial accumulations of blood are mainly epidural than subdural. Subdural haematomas above the tentorium appear as uneven areas of hyperdensity. They are poorly visualised on CT without frontal slices. Acute subdural haematoma is typically hypointense on T2-weighted imaging MRI due to deoxyhaemoglobin. On T1weighted imaging, subdural haematoma is usually isointense (Figs. 9.43, 9.44). Subacute subdural haematoma (from 2–3 days to 2 weeks) has a density identical to that of adjacent cerebral cortex on CT. Midline shift and accumulation of CSF in the compressed fissure under the haematoma are marked. In intravenous CE accumulation of contrast medium is seen in the displaced convex veins or in the hypervascularised internal wall of the forming haematoma capsule. Size and density of subdural haematomas gradually decrease with time (to 1.5–2 HU per day), due to resorption of haemoglobin, erythrocytes, and platelets. The density of subacute subdural haematoma 7–20 days after trauma is close to that of normal brain tissue. Isodense subdural haematoma is hardly identified on CT without CE, but may be detected with the help of indirect features such as displacement of the grey and the white matter from the internal cranial bone lamina and by smoothening of subarachnoid fissures homolaterally. CT with CE reveals that contrast medium accumulates in a haemorrhage capsule or in cortical veins, helping to identify the borders of brain surface. Subacute subdural haematoma is
832
Chapter 9
Fig. 9.41a–f DAI (3 days after injury), lesions in the posterior limb of the left internal capsule, splenium of the corpus callosum, right thalamus (a T1-weighted imaging, b FLAIR, c DWI MRI). No pathological changes are identified on T1-weighted imaging. Fractional
anisotropy map (d) shows decrease of values of anisotropy in the internal capsule posterior limb and corpus callosum splenium. 3D images (e,f) demonstrate clear asymmetry of the projection tracts and decrease of their density on the left
Fig. 9.42 Acute subdural haematoma in the
frontoparietal region (CT)
Head Trauma
833
Fig. 9.43a–d Acute subdural haematoma in the left temporoparietal region (second day
after injury). Haematoma is hyperdense on CT (a), whereas it is hypointense on MRI (b–d)
Fig. 9.44a,b Acute subdural haematoma
in the left temporal–parietal region is isointense on T1-weighted imaging (a) and hypointense on T2-weighted imaging MR (b). Subcortical contusions in the right temporal area are seen
834
Chapter 9
easily identified on MRI images, as it is hyperintense on T1weighted imaging (Figs. 9.45–9.48). Chronic subdural haematoma (discussed here for readers comfort, though it belongs to HI consequence) develops 2 weeks after HI. Bleeding is accompanied by bilateral haematoma capsule formation. The part of capsule adjacent to dura mater is usually characterised by abundant vascularisation and may be the source for microhaemorrhage, even in mild recurrent HI. Two hundred eighty-one patients with chronic subdural haematomas have been treated at the Burdenko Neurosurgery Institute. The density of haematomas on CT depended on time of its clinical manifestation since the last haemorrhage and time of examination. More frequently, the content of chronic subdural haematomas were hypodense compared with brain (61.6%). High protein content is responsible for subdural haematoma high density compared with CSF (25.8%). Recurrent haemorrhage results in increased density of chronic subdural haematomas, and the sedimentation phenomenon is
frequently marked. Liquid haematoma resembles the external contours of cerebral hemispheres. In chronic subdural haematoma connective tissue, trabeculae may be seen; they separate cavities of haematoma. These cavities may differ in content (Figs. 9.49–9.51). Chronic subdural haematomas may be isodense (12.6%). Usually, isodense haematomas are difficult to diagnose. CT diagnosis may be made if a narrow lumen of sulci or CE is present to visualise capsule contrasting or cortical vessels displacement. Bilateral subdural haematoma is seen in 25% of cases; when it is large, it may lead to marked compression of lateral ventricles without midline shift (Figs. 9.52–9.54). On CT perfusion of patients with bilateral subdural haematomas, decrease of regional cerebral blood flow may be identified in the haematoma-adjacent structures as well as a blood flow asymmetry between two hemispheres (Fig. 9.55). At present MRI is considered the gold standard for diagnosis of chronic subdural haematomas. Due to presence of methaemoglobin, they are characterised by hyperintense MRI signal of various extents. Usually, thick capsule, intra-
Fig. 9.45a–f Subacute subdural haematoma in the right frontopa-
MR-imaging (d) show hyperintensity of haematoma due to free methaemoglobin. Additional contusion focus in the right temporal area is visualised (e,f)
rietal–temporal region with midline shift to the left. Haematoma is hypodense on CT (a,b). T2-weighted imaging (c) and T1-weighted
Head Trauma
835
MRI
Fig. 9.46a–d Subacute subdural haematoma. T2-weighted imaging (a) and T1-weighted MR-imaging (b–d)
Fig. 9.47a–c Subacute interhemispheric haematoma. Axial CT (a) and T2-weighted imaging (b) and T1-weighted MR-imaging (c) visualise dislocation of brain structures from haematoma
836
Chapter 9
Fig. 9.48a–c Bilateral subacute subdural haematomas in frontotemporal areas. T1-weighted imaging (a), T2-weighted imaging (b), and FLAIR (c) MRI
Fig. 9.49a–c Chronic subdural haematoma in the left frontotemporal–parietal area. CT (a) shows the hypodensity of the haematoma, and T1-weighted imaging and T2-weighted MR-imaging (b,c) demonstrate hyperintensity
Head Trauma
837
Fig. 9.50a–f Chronic subdural haematoma. CT (a–c) and MRI (d–f) reveal right hemispheric abnormal extraaxial collection with the trabeculae, recurrent haemorrhages, midline shift
Fig. 9.51a–c Chronic subdural haematoma in the left temporoparietal region is hyperintense on T1-weighted imaging (a) and T2-weighted MR-imaging (b) and hypodense on CT (c)
838
Chapter 9
Fig. 9.52 Bilateral chronic subdural haematomas. Axial CT reveals the com-
pression of the frontotemporal area of the brain. Capsule calcification of the right haematoma is observed
Fig. 9.53a,b Bilateral chronic subdural haematomas. Series MRI (a) and CT
(b) demonstrate large haematomas with brain compression and regions of hyperintense signal on MRI in T1 sequence and hyperdensity on CT as signs of recurrent haemorrhages
Head Trauma
839
Fig. 9.54a–c Bilateral chronic haematomas. T1-weighted imaging
(a) and T2-weighted MR-imaging (b,c) detect large subdural fluid accumulation over cerebral hemispheres, compression of the brain and ventricular system
840
Fig. 9.55a–f Bilateral chronic subdural haematomas (a CT, b T1weighted MR-imaging). CT perfusion (c) reveals decrease of blood flow in haematoma–adjacent areas and slight asymmetry of blood flow between the hemispheres. Four weeks after haematoma drain-
Chapter 9
age CT (d) demonstrates straightening of ventricles and moderate dilatation of subarachnoid spaces. CT perfusion reveals normalization of CBF and CBV values (e,f)
Fig. 9.56a,b Chronic subdural haematoma
on the left. MRI reveals uneven signal on T2-weighted imaging (a) and hyperintense signal on T1-weighted imaging (b) (recurrent haemorrhage)
Head Trauma
841
haematoma trabeculae, and delayed bleeding form a typical picture of chronic subdural haematoma on T1-weighted imaging and T2-weighted MR-imaging (Figs. 9.56–9.59; Evans and Gean 1999). The improvement in the isodense chronic subdural haematomas visualisation may be achived by CECT (Fig. 9.60). Subdural hygromas are subdural accumulations of semiliquid exudate, resembling CSF without blood components; less frequently they are caused by CSF resorption disturbance. They are identified shortly after HI in 7–12% of cases or in the delayed period due to rupture of the arachnoid membrane. In several cases, subdural hygromas are hardly distinguished from chronic subdural haematomas, and more often, they are marked in the elderly and children; approximately in 20% of cases they are accompanied by other brain damage (Babchin et al. 1995). On CT, subdural hygromas are isodensive to the CSF; however, their walls do not accumulate contrast medium (Fig. 9.61). On MRI, subdural hygroma-like CSF is isointense in all sequences including FLAIR; however, mild hyperintensity may be seen in cases of high protein content (Figs. 9.62, 9.63).
9.2.3.2
Epidural Haematomas
Fig. 9.57a,b Chronic subdural haematoma of the right frontotemporal-parietal area. MRI series on T1-weighted imaging (a) and T2weighted imaging (b) reveal a large extra-axial haematoma of the
lenticular form with a heterogeneous signal (recurrent haemorrhages). Connective tissue trabeculae are marked in the haematoma structure
Epidural haematomas are the second frequent type of extracerebral traumatic damages and are usually combined with skull fractures (in 85–90% of cases). Damage of the internal skull bone lamina may lead to rupture of medial meningeal arteries or their branches; less frequently, it leads to bleeding from meningeal veins or venous sinuses (transverse or sigmoid). Blood penetrates the space between of internal skull bone lamina and dura mater, closely connected with sutures, and that is why epidural haematomas never cross sutures and have typical lens-like appearance compared with subdural haematomas. However, they may expand beyond dural processes like falx. Epidural haematomas are more frequently seen in young people, they are usually unilateral (95%), and in most cases, they are located in the supratentorial space in the temporoparietal region. They are rarely seen in the posterior fossa (less than 5%). Such pathology usually results in severe disability or death. Two thirds of acute epidural haematomas appear hyperdense, and in a third of cases, they have mixed density on CT. They look like biconvex mass lesions, usually located above skull bone fracture. Hypodense areas inside haematoma are admixture of free blood and serum separated from a blood clot. They may be indicative of acute arterial haemorrhage. In
842
Chapter 9
Fig. 9.58a–d Bilateral chronic subdural haematomas. MRI on T2-weighted imaging (a),
T1-weighted imaging (b,c) and also CT (d) detect bilateral haematomas with trabeculae and capsule. Hyperintensity on T1-weighted imaging points to recurrent haemorrhages
Fig. 9.59a–c Bilateral chronic subdural haematomas. T2-weighted imaging (a) and T1-weighted MR-imaging (b,c) shows bilateral subdural
accumulations of different signal intensity, especially in T1 sequence (hyperintense signal from haematoma on the right is caused by recurrent haemorrhage)
Head Trauma
843 Fig. 9.60a,b Chronic subdural haematoma
of the right frontoparietal area. CT before (a) and after (b) CE. Extra-axial lesion with compression of brain tissue is detected (better after CE)
Fig. 9.61a,b Chronic subdural hygroma
in the left frontotemporal–parietal area. CT reveals hypodense area with the density close to that of the CSF
Fig. 9.62a–c Combination of hygroma of the left frontal area and arachnoid cyst at the base of the middle cranial fossa. T1-weighted imaging (a), T2-weighted MR-imaging (b) and CT (c) detect subdural hygroma with the signal characteristics close to those of the CSF
844
Chapter 9 Fig. 9.63a,b Contusions in the right
frontotemporal region, damage of the corpus callosum splenium, hygroma in the left frontotemporal area. MRI: signal from hygroma is close to that of CSF in lateral ventricles
approximately 30% of cases, other lesions on the ipsilateral side are found as well as contrecoup subdural haematomas and contusions (Figs. 9.64–9.68). Acute epidural haematoma is isointense to cerebral cortex on most MRI sequences; however, a thin dark line between haematoma and brain is always revealed. This line is the displaced dura mater. Subacute and early chronic epidural haematomas are hyperintense on T1- and T2-weighted imaging (Figs. 9.69–9.71). Large epidural haemorrhages with prominent mass effect may displace and compress the brain, leading to transtentorial herniation. Angiography (CTA, MRA) reveals avascular, crescent-shaped areas and displacement of cortical vessels from the cranial vault. Chronic epidural haematomas are isointense on T1- and T2-weighted imaging compared to the CSF. The combination of epi- and subdural haematomas may be observed (Fig. 9.72), and a release of haemorrhage after repeated head trauma may be also identified (Fig. 9.73).
Fig. 9.64 Acute epidural haematoma of the right frontal area (CT)
Small epidural asymptomatic haematomas are situated along the convex surface, and they are smaller than 1.5 сm in width; they cause minimal or no mass effect and do not require (surgical) intervention, except CT and MRI in order to exclude haematoma enlargement, which more frequently occurs within the first 48 h after injury (Fig. 9.74).
9.2.3.3
Intracerebral Haematomas
Intracerebral haematomas are frequently caused by penetrating brain injuries—gunshot or blunt injuries—or occur after closed HI. Similar to contusions, they are mainly localised in frontal and parietal regions; haemorrhage is accompanied by blood clot formation that penetrates into the deep white matter or traumatic rupture of perforans vessels occur. Haemorrhage spreads along axons, haematoma is formed, and blood clot is formed and retracted. In the active phase, bleeding may
Fig. 9.65 Acute epidural haematoma of the left frontal area. Haem-
orrhagic focus in the right basal ganglia is also revealed
Head Trauma
845 Fig. 9.66 Acute epidural haematoma in the
right frontotemporal area, defect of the left temporal bone after resection, subgaleal haematoma (CT)
Fig. 9.67a,b Acute epidural
haematoma in the lateral part of the posterior cranial fossa on the right with occipital bone fracture. CT in bone (a) and standard (b) windows
Fig. 9.68 Acute epidural haematoma in the
posterior cranial fossa on the left (CT)
846
Chapter 9
Fig. 9.69a–f Subacute epidural haematoma in the right frontal area. T1-weighted imaging (a,b), T1-weighted MR-imaging (c,d). Sagittal and
coronal projections (e,f) add information about haematoma size and spread
Head Trauma
847
Fig. 9.70a,b Subacute epidural haematoma of the left frontal area. T2-weighted imaging (a) and T1-weighted MRI-imaging (b) reveal hyperintense blood accumulation of the lenticular form
Fig. 9.71a–c Early subacute phase of the epidural haematoma of the left temporal area on T1-weighted imaging (a), T2-weighted imaging (b), and FLAIR (c) MRI. Contrecoup contusion is in the right temporal lobe
848
Chapter 9
Fig. 9.72 Chronic epi- and subdural haematomas of the left frontotemporal-parietal area. T2-weighted MRI-imaging shows hypertrophy of the dura matter at the haematoma border
Fig. 9.73 Epidural haematoma in the left frontal area. CT after contract enhancement detects a hyperdense area surrounded by the zone of peripheral contrast accumulation (capsule formation)
Fig. 9.74 Typical CT appearance of acute epidural haematoma in the left parietal area
rupture into the ventricular system through ependyma (up to 30% of cases) (Zimmerman 1999). Acute posttraumatic primary haematoma should be distinguished from haemorrhage into contusion area. However, if examination is performed in the acute phase, then CT or MRI may fail to differentiate these two types of lesions. Incidence of traumatic intracerebral haematomas is lower than that of haemorrhagic contusions, and they most frequently occur in adults. CT shows a haematoma directly after HI. It look like a hyperdensive, well-delineated area, and perifocal oedema may be identified within the first 12 h after injury (Fig. 9.75); the peak of its prevalence is 2 or 3 day after head trauma. Though most intracerebral haematomas are revealed within the first 24 h after injury, a small percent develops 1–7 days after injury (Besenski et al. 1996; Orrison 2000). These intracerebral haematomas mostly develop on the side ipsilateral to contusion lesion and are usually located in the frontotemporal region, and, probably, they should not belong to pure intracerebral haematomas, the main cause of which is rupture
of vessels wall after HI. Subacute haematomas (3–7 days after HI) may have mixed density in their centre on CT if blood clot retraction occurs. In late subacute haematoma (7–14 days after injury), the density starts to decrease from the periphery to the centre, approximately by 1–2 HU per day. More than two-week subdural haematomas mainly consist of intracellular ferritin and lysosomal haemosiderin. CT shows progressive decrease of their density. By the third week, haematomas become isodensive compared with brain parenchyma and are hardly identified. Continuing proteolysis, phagocytosis, and atrophy lead encephalomalacy in the haematoma place. Different paramagnetic forms of intra- and extracellular haemoglobin are the main factors that influence dynamic MRI picture during blood clot retraction (Figs. 9.76–9.78). Superacute haemorrhage (within the first hours) contains oxyhaemoglobin, acute haemorrhage (first three days) contains deoxyhaemoglobin, subacute (less than 3 weeks) contains methaemoglobin, and chronic haemorrhage (over 2 months) has a haemosiderin ring. Subacute haemorrhage may be sub-
Head Trauma
Fig. 9.75 Acute intracerebral haematoma (first day after HI). Hy-
podensive area on the haematoma periphery represents perifocal oedema formation
divided into early and the late stages. Early subacute haemorrhage (intracellular methaemoglobin) develops on the 3d day and lasts for a week. Late (extracellular methaemoglobin) haemorrhage occurs at first week after injury. Transformation into the chronic stage is characterised by a haemosiderin ring around haematoma on MRI (Table 9.1; Figs. 9.79, 9.80). These changes may be seen on MRI for a 3–5 year period. The results and experience in treating patients with contusion lesions and intracerebral haematomas without lifethreatening signs of brain compression or dislocation gained in Burdenko Institute of Neurosurgery show that if thorough clinical and CT/MRI dynamical and intensive care are performed, then surgical intervention may be avoided, and a favourable outcome may be reached in 80% of cases, with good recovery and moderate disability in most patients. Only in 4.5% of patients in this group the immediate causes of fatal outcome were progressive brain oedema with dislocation and brainstem compression and brainstem haemorrhage. In the rest of the patients, causes of fatal outcome were different extracranial complications like septic pneumonia, myocardial infarction, pulmonary embolism etc.
9.2.4 Traumatic Subarachnoid Haemorrhages HI is a frequent cause of subarachnoid haemorrhages (SAH) due to rupture of small vessels, pial, and arachnoid veins. SAH is seen in 33% of patients with moderate HI and it is found in almost 100% of cases at autopsy, in usual combination with brain contusion and subdural haematomas. The risk of SAH in
849
very young or elderly patients is higher, as their subarachnoid spaces are wider. Blood from intracerebral haematoma usually penetrates into ventricular system, and then together with the intraventricular CSF gets into the subarachnoid space. According to several authors, vasospasm occurs in 20–41% of patients with SAH. On CT, hyperdensive blood may be seen in basal cisterns and subarachnoid spaces, for instance, in Sylvian fissures, superior cerebellar cisterns, etc. (Figs. 9.81, 9.82). Interpeduncular cistern may be poorly visualised due to small quantities of isodensive blood. Small quantity of subarachnoid blood may, however, not be visualised on CT. Due to low haematocrit and deoxyhaemoglobin, which are almost isointense compared which brain tissue on T1 and T2weighted imaging in the acute stage of SAH, MRI may miss or underestimate acute SAH. Subacute SAH usually looks bright on Т1-weighted imaging (Fig. 9.83). FLAIR can identify small areas of acute SAH (which are not seen on other MRI sequences or CT) appearing as hyperintense signal in Sylvian fissures and convex spaces. More frequently, CT is used to diagnose SAH; however, recent studies have shown that FLAIR has 100% sensitivity in detecting acute SAH. SAH and intraventricular haemorrhages (IVH) are easily differentiated from parenchymal haemorrhages, as in SAH and IVH blood is admixed with CSF, and has high oxygen and protein content, thus shortening T1, and that is why bloody CSF looks hyperintense on FLAIR (on which the CSF is normally dark). This sequence was elaborated in order to attenuate signal of protons in pure CSF; however, presence of protein and haemorrhagic component in CSF is considered the reason for hyperintense signal on FLAIR. Sometimes artefacts of CSF pulsation may imitate SAH on FLAIR in the prepontine cisterns, making difficult performing noninvasive diagnosis. Even CT may miss acute SAH in some cases, but clinical signs and negative CT dictate the necessity to perform lumbar puncture to verify or rule out SAH or meningitis. Lumbar puncture indicates when there is dissociation between clinical signs and CT findings. Late subacute SAH looks bright on DWI due to restricted motion of water molecules. Hydrocephalus is the most frequent complication of SAH. Acute obstructive hydrocephalus may develop within the first week due to ependymitis or intraventricular blood occluding the Sylvian aqueduct or the fourth ventricle. Communicating hydrocephalus may develop within the first hours at first week if arachnoid granulations are filled with blood, thus leading to fibroplastic proliferation in subarachnoid spaces and their blockage. SAH may induce vasospasm. The highest risk of severe ischaemia occurs within 5–15 days after injury. Vasospasm is most frequent when SAH is combined with subdural haematoma, IVH, contusion or intracerebral haematoma.
9.2.5 Intraventricular Haemorrhages IVH are relatively rare. More frequently, IVH are combined with contusions and SAH. Intracerebral haematomas may cause white matter tracts damage, with blood rupture into the ventricular system. Haemorrhagic damage of corpus callosum
850
Fig. 9.76a–i Dynamic CT and MRI of intracerebral haematoma (a–c 9, d–f 17, and g–i 30 days post-injury)
Chapter 9
Head Trauma
851
Fig. 9.77a,b Acute intracerebral haema-
toma of the left temporoparietal area (third day after injury). T1-weighted imaging (a) and T2-weighted imaging (b) MRI
Fig. 9.78a,b Acute intracerebral haema-
tomas of the right frontal area (first day after injury). T2-weighted imaging (a) and T1-weighted MRI-imaging (b) visualise zones of heterogeneous, hypointense signal in the right frontal lobe caused by deoxyhaemoglobin
Table 9.1 MRI picture of an intracerebral haematoma depending on transformation rate Period
Content
Т 1-weighted imaging
Т 2-weighted imaging
Superacute (<24 h)
Oxyhaemoglobin
Isointense
Hyperintense
Acute (1–3 days)
Deoxyhaemoglobin
Hypointense
Hypointense
Early subacute (3–7 days)
Intracellular methaemoglobin
Hyperintense
Hypointense
Late subacute (1–2 weeks)
Extracellular methaemoglobin
Hyperintense
Hyperintense
Chronic (>2 weeks)
Haemosiderin rim
Hypointense on periphery (haemosiderin)—hyperintense in the centre (than hypointense)
Hypointense on periphery (haemosiderin)—hyperintense in the centre
852
Chapter 9
Fig. 9.79a–c Chronic intracerebral haematoma with recurrent haemorrhage. T2-weighted imaging (a), T1-weighted imaging (b), and DWI (c
series on the bottom of figure part) MRI demonstrate hyperintense signal from methaemoglobin in T1 and T2 sequences
Fig. 9.80a–c Subacute intracerebral haematoma of the right frontal area on T2-weighted imaging (a) and T1-weighted imaging (b,c) in combination with subacute subdural haematoma on the right. Hypointense signal at haematoma periphery means accumulation of haemosiderin (the beginning of chronic phase)
Fig. 9.81a,b Subarachnoid haemorrhage in
acute HI. CT detects blood in the suprasellar cisterns (a) and in posterior part of the interhemispheric fissure (b)
Head Trauma
853
Fig. 9.82a–c Severe HI, depressed fracture of the right temporal bone, subarachnoid haemorrhage (first day after accident). CT (a–c) reveals hyperdense areas in the projection of basal subarachnoid spaces and Sylvian fissure on the right
Fig. 9.83a,b Subarachnoid haemorrhage (sixth day after accident). T1-weighted imaging MRI demonstrates hyperintense areas in the Sylvian fissure on the left
854
Fig. 9.84 Intraventricular
haemorrhage. Acute phase, second day after accident. CT detects acute blood in the lateral ventricle
Chapter 9
Fig. 9.85a,b Intraventricular haemorrhage (fourth day after accident). CT shows acute blood in ventricular system. Microhaemorrhages are visualised bilaterally in basal ganglia. Subependymal haemorrhage is detected in the right hemisphere
and brainstem haemorrhages are also frequently combined with IVH. On CT, a hyperdense blood layer in the ventricles with CSF above it may be seen. Primary IVH may be caused by rupture of subependymal veins and/or choroid plexus. If these two injuries are isolated and hydrocephalus is absent, then they are clinically insignificant. But most frequently IVH is accompanied by clinically significant brain injuries (Figs. 9.84, 9.85).
9.2.6 Pneumocephalus Pneumocephalus is caused by abnormal communication between air-containing structures (nasal sinuses and air-containing cells of the temporal bone) and subarachnoid spaces via rupture of meninges and skull base fractures, impacted fractures of nasal sinuses, and air-containing cells of the mastoid process (Fig. 9.86). Impacted fractures allow air to penetrate intracranially. On CT, air can be seen in brain tissues, epidural, subdural and subarachnoid spaces, or ventricles. Intracranial air may be diffuse or focal in form of pneumocele (Fig. 9.87). As a rule, pneumocephalus is not life threatening because air is gradually absorbed. Sometimes air volume may increase due to valve mechanism producing tense pneumocephalus, which often occurs after skull base fractures, and after craniotomy. If air volume increases abruptly, then brain compression may occur. If pneumocephalus persists, then CSF leakage should be suggested. Pneumocephalus is usually marked soon after trauma; however, it may develop days or months later. Dynamic CT is required to exclude a delayed pneumocephalus in patients with skull base fractures. Air is easily found on cranial CT—it looks highly hypodense, more hypodense than fat inclusions in orbits, and isodense like in nasal sinuses (Fig. 9.88–9.90). On MRI, air
looks like areas of signal void. Epidural air is frequently located in the same place and does not move when the head changes position. Subdural air often forms at the air–liquid level. Subarachnoid air is frequently found in the convex fissures and is multifocal. Intraventricular air is usually identified in the anterior horns of lateral ventricles and intraventricular blood, conversely, is often found in the posterior horns. Tense pneumocephalus and pneumocele sometimes require immediate surgical treatment if patient condition deteriorates. In a noncomplicated hydrocephalus, air volume is significantly reduced by the 10–15th day, and 3 weeks later it disappears.
9.2.7 Fractures of Skull Vault and Skull Base Isolated extracerebral injuries such as skull fractures (especially skull vault) are not clinically significant by themselves, which is why routine X-ray craniography (if CT is present) becomes less significant in clinical practice. Fractures of skull vault are signs of bone damage after HI. However, that does not mean that the brain is injured. On the other hand, one third of patients with severe head injuries do not have fractures. That is why X-ray craniography is ineffective as screening technique. Nevertheless, due to wide accessibility (any hospital has an X-ray device) and legal reasons, this diagnostic tool is widely used. Bone damages are significant not only as signs of trauma itself, but also as way of infectious dissemination, when fracture is accompanied by loss of integrity of adjacent tissues. If palsy of any cranial nerve, CSF leakage, nasal, or ear bleeding is revealed, then it is necessary to reveal skull base fracture affecting an anatomic fissure or a channel. Many fractures can be visualised on craniography, which helps to identify the zone of interest during CT. Convexity of
Head Trauma
855
Fig. 9.86a,b Craniofacial injury. CT reveals damage of the facial bones and internal wall of frontal sinus; air is revealed in the subarachnoid spaces
Fig. 9.87 Pneumocele in the left
frontal area (CTCG)
856
Chapter 9
Fig. 9.88a–c Posttraumatic cystic changes in the right frontal area, CSF leakage, and air in cyst and anterior horn of the left lateral ven-
tricle. CT
Fig. 9.89 Pneumocephalus over frontal lobes, and air in the subarachnoid spaces and anterior horn of the lateral ventricle. 2 days after HI. CT
Fig. 9.90 Pneumocephalus with air in lateral ventricles and suba-
rachnoid spaces of the right frontoparietal area is detected on CT
Head Trauma
857
Fig. 9.91a,b Acute subgaleal haematomas.
CT (a) detects blood accumulation over parietal area, T2-weighted imaging (b) reveals thickening of the soft tissues and subgaleal haematoma in the right frontoparietal area (different cases)
soft tissues of the skull (subgaleal injuries) may point out the region of fracture on CT or MRI (Figs. 9.91, 9.92). While healing, the line of fracture can be hardly distinguished from such structures like vascular picture or bone sutures. Depending on location, skull fractures are subdivided onto skull vault fractures and skull base fractures. Gunshot (injuries) fractures form a separate group, for they significantly differ from civil injuries.
9.2.7.1
Skull Vault Fractures
The following skull vault fractures are outlined: linear, impacted (compression), and diverging (traumatic divergence of cranial sutures). Several authors also distinguish whole fractures (fractures with bone defect formation). Linear fractures occur with blunt injury, they are more vivid than the vascular picture, and cranial sutures have different configuration and length, rectification and angularity, sharpness and clarity of visualisation, and frequently, separated visualisation of fissures in the internal and external cranial bone lamina fractures is had. Usually their width is less than 3 mm. Linear fractures are frequently located in the parietotemporal, frontal, and occipital regions and tend to expand from the cranial vault to the skull base (Fig. 9.93). Special attention is required if a linear fracture crosses the sulci of meningeal arteries, venous sinuses and channels of the diploetic veins. Frequently vessels in these areas are affected, and haemorrhage occurs. In unclear cases, target (contact) craniography is required to ascertain the size and precise location of fracture. Linear fractures in children heal in less than 3–6 months, whereas in adults it may take 2–3 years. If fracture line does not heal, then leptomeningeal cysts or meningoencephalocele may develop. Both complications occur due to complex fracture with rupture of dura mater and invagination of soft tissues between fragments of fractured bones. Brain pulsation is
transmitted into margins of bone defect, hampers healing and leads to its dilatation. Impacted (compression) fractures more frequently occur after HI done by a blunt object with limited square, and usually accompanied by damage of soft tissue in this site. In contrast to linear fractures, impacted ones are not so clearly visualised, which is why in all cases when they are suspected, it is necessary to perform target (tangential and contact) craniography. Impacted fractures are subdivided into “impressed” and “depressed” fractures. In the former there is no complete divergence of bone fragments, and the integrity of the internal cranial bone lamina is preserved at the periphery of traumatic lesion. If the square of impaction does not exceed thickness of adjacent skull vault bones, then damage of dura mater rarely occurs. Depressed fractures usually cause damage to dura mater and brain, as they are accompanied by complete separation of bone fragments and their intracranial dislocation. This group of fractures is better visualised on CT in bone window regimen (Figs. 9.94–9.97) and to identify cortical contusion lesions in this cases, MRI is feasible (Fig. 9.98). Impacted compression fractures may lead to infectious complications such as osteomyelitis, meningitis, brain abscesses, and relapsing sinusitis. Divergence of cranial sutures usually occurs when the impact force is high and when ruptures and scattering of skull occurs, which means the utmost severity of head trauma. Coronal and lambdoid sutures are less than 2 mm in width. Traumatic divergence of cranial sutures (diastasis) is diagnosed when width of sutures exceeds 3 mm. Thus, coronal suture is consolidated by the age of 30, but the lambdoid suture does not consolidate even after age 60. True divergence of cranial bone sutures without fractures are seen only in children and are very rare. In adults, rupture of sutures is accompanied by damage of their margins—the “teeth” sign. The most reliable sign is a ladder-like deformation of suture due to transposition of bone fragments into different levels, which is better seen on tangential target craniograms or CT scans crossing the fracture site.
858
Chapter 9
Fig. 9.92a–e Linear fracture of skull vault in the frontotemporal area extending to the anterior cranial fossa base on X-ray in the direct (a) and lateral (b) planes. T2-weighted imaging (c) and FLAIR (d,e) MRI additionally reveal contusions in the left temporobasal area with the blood in sphenoid sinus and subdural haematoma in the left frontal area
Fig. 9.93a,b Linear skull fractures on craniography of different patients
Head Trauma
859
Fig. 9.94a–c Depressed skull fracture of the right parietal bone. CT, coronal planes
Fig. 9.95a–f Depressed skull fracture of the right parietal bone close to the superior sagittal sinus. Skull X-rays (a,b) and CT (c) demonstrate skull bone damage. MRI (d–f) additionally visualises brain damage adjacent to the fracture area. d T2-weighted imaging, e DWI, and f FLAIR sequence
860
Chapter 9
Fig. 9.96a–c Depressed fracture of the right frontal bone with contusion of the right frontal lobe. CT
Fig. 9.97a,b Fragmental skull fracture of the left temporal and parietal bones with temporal lobe contusion, haemorrhagic contusion, and
ischaemic zone in the left temporoparietal–occipital area. Some blood in the posterior horn of the right lateral ventricle is visible. CT
Head Trauma
861
Fig. 9.98a–g Contusion in the left frontotemporal–parietal
area; depressed fracture of the temporal and parietal bones. CT (a,b), MRI (c–g). Acute HI, day 2
862
9.2.7.2
Chapter 9
Skull Base Fractures
Over 900 patients with craniofacial and craniobasal injuries were examined in the Burdenko Neurosurgery Institute. Among them, 46.1% had skull base fractures, and 18.6% had basal CSF leakage. Presence of blood behind the tympanic membrane without direct ear trauma, presence of otorrhea, and subcutaneous haematoma around the mastoid process, orbits, or eyelids without their direct injury, may indirectly suggest skull base fracture, which is accompanied by intracranial traumatic lesions in 50% of cases. Craniography is less informative in these cases due to severity of a patient condition and difficulties in performing target craniograms, with special positioning for examination of different skull bones. The best and the most informative technique in these cases is CT (axial and frontal projections, 3D reconstruction in spiral CT) and CTCG. It should be noted that this type of injury is considered severe, and its prognosis often unfavourable. Brainstem, cranial nerves, and dura mater are frequently damaged in skull base fractures. The passage of linear fractures depends on the type of impact. In lateral contusions and compressions, transverse fractures occur, and in anterior and posterior contusions, longitudinal fractures are common (sometimes across all cranial fossae). Linear fractures often become an extrapolation of splits of skull vault bones. Fractures of the frontal bone squamous part and sphenoidal bone are often extrapolated into external parts of the anterior cranial fossa, and the middle part of the latter is damaged in craniofacial injury with involvement of facial skeleton (Figs. 9.99–9.102). Typical features of these fractures are damage of walls of the frontal sinuses, ethmoidal sinuses, nasal sinuses passages, their mucosal membranes, and, as a rule, dura mater. All this may lead to disturbed communication between the cranial cavity and nasal sinuses and consequent infectious complications. Other manifestations are liquorrhea nasalis, nasal bleeding, cranial neuropathies I–VI (vision loss, sensory loss on the face, anos-
mia etc.), frontal haemosinus, haemosinus of the ethmoidal cells, and pneumocephalus. Fractures of the middle cranial fossa bones may be secondary to linear fracture of the parietal or temporal squama bones. Fractures of the sphenoidal bone are usually cross-spinous, oval, or round foramina that have parasellar location; that is why cranial neuropathies III–V and fractures of the sphenoidal sinus walls and of the posterior walls of the ethmoidal labyrinth are typical and manifested by nasal or ear bleeding or liquorrhea, intraorbital and occipital haematomas, carotid-cavernous fistulas and pneumocephaly. Fractures of the temporal bone pyramids are distinguished in separate group, due to possible complications: disturbance hearing and equilibrium organs. Oblique (transverse) and longitudinal fractures are distinguished in relation to the pyramid axis. The oblique (transverse) fractures may pass in any region from the apex to the lateral margin of the pyramid (Fig. 9.103). The acoustic tube is affected in the pyramid apex, and often, the internal carotid artery channel is affected too, and severe arterial bleedings may occur. The middle and external parts of the pyramid walls of the internal acoustic passage with the vestibulocochlear nerve and the labyrinth may be affected. In such patients hearing loss and equilibrium impairment occur soon after HI. Damage of the aqueduct of Fallopius channel walls results in facial nerve defect. Longitudinal fractures frequently descend from the temporal bone squama, pass through the anterior surface of the pyramid, and affect the anterior wall of the tympanic cavity and the tympanic membrane. However, structures of the internal ear are less frequently affected. Such fractures often manifest by ear bleedings and loss of sound conductivity. Paresis of soft palate, dysphagia, and flaccid dysphonia may occur after injury of cranial nerves IX–XI, fracture of the temporal bone pyramid near the jugular foramen. Fractures of the posterior fossa cranial bones (Fig. 9.104) may be extrapolations of the total skull base fracture or descend from the skull vault; they often are combined with
Fig. 9.99a–c Fractures of the frontal bone, walls of the left maxillary sinus and squama of temporal bone. CT in bone window regimen
Head Trauma
863 Fig. 9.100a,b CT. Fracture of the anterior wall of the left maxillary sinus with fluid in the sinus cavity. Fracture of nasal bones
Fig. 9.101a,b Axial CT. Multifragmental fracture of facial scull bones. Axial CT. Multiple fractures of the orbit, anterior and middle cranial fossa, and frontal bone
Fig. 9.102 Fracture of the skull base. CT series. Multiple fractures of facial skull bones with haemotamponade of the paranasal sinuses
864
Chapter 9 Fig. 9.103 Fracture of left temporal bone pyramid. Axial CT
Fig. 9.104a,b Fragmental fracture of squama of the occipital bone. CT (a,b) in bone window
fractures of the temporal bone pyramid, margins of foramen magnum, and jugular foramen. Ring-shaped fractures around foramen magnum are exceptionally rare. MRI gives only indirect information about skull base fractures as haemosinus of the nasal sinuses or ethmoidal air-containing cells in the frontotemporal and basal regions (Figs. 9.105, 9.106). In conclusion, it should be mentioned that subdivision of skull vault fractures often conditional. Different combinations may be observed in clinical practice: from simple splint (short linear fractures) to very complex, multisplinter open and combined fractures (Fig. 9.107).
9.2.8 Gunshot Wound Head Injury Gunshot wound HI is the second frequent cause of death in the United States in patients aged 15–24 years (Lee and Go 2002). Gunshot wound HI is subdivided into “open” and “closed” depending on the risk of development of intracra-
nial infection. However, it should be mentioned that due to transition of kinetic force of a bullet through an intact skull, different types of brain damages may occur, from a concussion to severe contusion. Gunshot wound HI are subdivided according to degree of penetration of shooting projectile into the cranial cavity: • Superficial: injuries of soft tissues and skull vault bones • Tangential (ricochet): when a projectile does not penetrate into the skull vault, but traumatic injury of various severity may occur, from contusion to damage of brain parenchyma with bone splinters (Babchin 1949; Gaidar 1998; Gean 1994) When a projectile penetrates the skull vault, gunshot wound HI are additionally subdivided into “penetrating” and “perforating”. Over 80% of gunshot wound HI are penetrating. In contrast to closed HI, it is more difficult to assess patients’ condition in gunshot HI due to involvement of many anatomical structures—soft tissues, cranial bones, and meninges.
Head Trauma
865
Fig. 9.105a–c T2-weighted imaging (a) and T1-weighted MR-imaging (b,c) reveal small haematoma in the middle cranial fossa floor, and haemorrhages in cells of mastoid and tympanic cavity on the right. Subacute HI
X-ray craniograms assess condition of cranial bones, boning splinters, and ascertain position of a foreign body. X-ray craniograms may give additional information after CT is performed, as they lack linear artefacts at sites where foreign bodies are present. The same information may be obtained on scout view CT. Usually, it is sufficient to obtain craniograms in direct, lateral, and rectangular projections regarding to the wound passage. CT is the main diagnostic tool for gunshot HI patients. It should be done immediately after admission. Modern techniques such as spiral CT markedly reduce scanning time. CT acquires a 3D set of data with the subsequent reconstruction of slices of any thickness in soft tissue and in bone regimens. The following artefacts may be seen: linear, radial artefacts from foreign bodies (Fig. 9.108), partial mass artefacts, and motion artefacts. To identify changes in artefacts zones, scanning may be repeated with another gentry’s inclination angle. To identify extracerebral haemorrhages, a wide scanning window should be chosen for soft tissue regimen. It should be noted that CT allows reconsideration of the concept of distribution of bone splinters along the wound channel and ascertains feasibility of their extraction in every particular case (Fig. 9.109). Application of MRI in diagnosis of gunshot HI is limited by ferromagnetic properties of materials of which most bullets or shell casings are made. Minimal artefacts are seen only in gunshot HI caused by nonferromagnetic bullets, and in these cases, adjacent brain structures are better seen on MRI than on CT. FLAIR reveals acute haemorrhages, including subarachnoid, more precisely than CT does. DWI is also applicable in early diagnosis. Nevertheless, CT is the leading method of choice in the diagnosis of gunshot HI, and MRI may only give additional information and cannot radically change management strategy.
In rare cases, angiography is performed to exclude injuries to cerebral vessels. Modern achievements of noninvasive visualisation of vessels (MRI, CT) perform noninvasive AG. Certain indications exist for standard AG, MRA, and CTA in clinical practice. Metal fragments influence the quality of MRA and CTA. Delayed haemorrhages and clinical manifestations of arteriovenous fistules are signs of significant vascular events, and they should be assessed by standard angiography. If metal fragments are absent, then MRA and CTA may be used in the subacute stage of large intracerebral haemorrhages. They are more preferable than standard angiography in the diagnosis of such vascular events such as dissection of arterial intima. Standard angiography may visualise lumen narrowing, but gives no information about changes of the vessel wall. CTA is more informative than MRA, due to absence of flow void artefacts and higher resolution. Nevertheless, these techniques should be further compared and indications more precise for their use in gunshot HI patients should be elaborated. Different haematomas may be seen in soft tissues in gunshot wound HI: subcutaneous, subperiostal, and subgaleal. Subcutaneous and subperiostal haematomas are more frequently seen in children, whereas subgaleal haematomas are more frequently seen in adults irrespectively to the type of injury, whether it is penetrating or close. On CT, these haematomas are seen as hyperdense areas. They tend to be largely expanded, whereas subperiostal haematomas are limited and lens shaped in some cases. On X-ray craniography, satellite divergent fractures are usually seen at the site of the projectile entry, whereas linear fractures are seen in the delayed period. Bone splinters in gunshot HI may cause such complications as haemorrhages, infections, and epilepsy. They appear as focal dark areas on X-ray craniograms. Depending on ve-
866
Fig. 9.106 Skull base fracture. T1-weighted imaging (a) and T2-weighted imaging (b) MRI reveal blood in
cells of the left mastoid bone
Fig. 9.107a–f Severe HI with multiple fractures of facial skull. CT in three projections and 3D reconstructions
Chapter 9
Head Trauma
867 Fig. 9.108 Penetrating gunshot brain injury. CT reveals a foreign body with typical artefacts alongside with posttraumatic changes
Fig. 9.109a,b Perforating gunshot brain injury. CT demonstrates wound canal with haematoma and bone fragments along it
868
locity of the projectile, the skull may have hole of a simple or complex shape. Damage and/or distortion of the internal bone lamina are seen at the entry. Size of entry wound is usually less than that of the site of outlet wound. In most cases, many bone splinters of the internal bone lamina are seen at the entry wound. If a bullet is in the brain parenchyma, then it is more likely that it ricocheted off other bones (Fig. 9.110). Type of bone splinters seen in tangential injuries depends on the depth and angle of bullet inclination, as well as bullet energy. Impacted splinter fractures are more frequently seen in tangential injuries and are better seen on CT. Splintering of the skull at the site of wound may not be seen on routine craniograms, but easily identified on CT. After tangential injuries of the cranial vault bones a furrow-shaped bone injury occurs. Skull base fractures are better identified on spiral CT with frontal reconstruction. After gunshot HI several complications may develop such as pneumocephaly, epidural and subdural haematomas, and subarachnoid haemorrhages. All these events are easily visualised on CT (Fig. 9.111). Changes in the brain parenchyma are cone shaped, with the base at the entry and an apex directed along the wound channel. Wound changes alongside the channel vary and depend on velocity of a bullet flight and rotation. Ricochets are prognostically unfavourable. Haemorrhages and contusions may develop far from the wound channel and they may be delayed, for instance, in face and neck injuries. DAI may develop in gunshot HI. Intraventricular haemorrhages are prognostically unfavourable and caused by damage of closely located vessel or after rupture of subependymal haematomas. Ischaemic events are frequently seen in penetrating HI. Intracranial pressure rises soon after gunshot HI due to several factors such as posttraumatic hyperaemia, early oedema, haemorrhage, and obstructive hydrocephalus. Oedema is usually vasogenic and occurs along the wound channel; it is more frequently manifested between 42 and 72 h after injury, and frequently resolves within a week. On CT and MRI, intracranial pressure rise appears as narrowing of the CSF spaces, especially basal cisterns, and impactions may also occur.
Chapter 9
Fig. 9.110 Penetrating gunshot brain injury. Axial CT shows wound
canal with a foreign body in the left parietal and typical metal artefacts from it
Long-term complications include infections, CSF fistulas and hydrocephalus. All forms of intra- and extracranial infections may be seen in gunshot HI: soft tissue infection around wound, osteomyelitis of cranial bones, epidural and subdural empyemas, meningitis, ventriculitis, cerebritis, and brain abscess. Though modern surgery and antibiotics reduce the number of infectious complications, they make up 5–7% of cases. Infectious complications may occur even several years later. Risk factors are exogenous wound infection, CSF fistula, and injury of nasal sinuses. A bullet remaining intracranially does not increase the risk of infectious complications itself. Osteomyelitis of the cranial bones may occur in the long term. Lytic changes that are typical for osteomyelitis are easily identified on CT. Nevertheless, MRI may reveal bone infections at the earliest stages.
Fig. 9.111a,b Penetrating gunshot brain injury. Axial CT reveals a foreign body in the left parietal area with signs of acute subarachnoid haemorrhage
Head Trauma
Epidural and subdural empyemas resemble meningeal haemorrhages by their shape, and are hypodense on CT, are mildly hyperintense on T1-weighted imaging, and isointense to the CSF on T2-weighted imaging. The extent of diffusion in empyemas is reduced by what is seen on DWI. Peripheral CE is more typical for empyemas than it is for haemorrhage. However, in most cases differential diagnosis of empyemas and meningeal haemorrhages is difficult. Brain abscesses occur after gunshot HI in 2–3% of cases. They are formed 2–4 weeks after injury or later. CSF fistulas occur in approximately 9% of gunshot HI. They are predominantly located in orbits and communicate with nasal sinuses. Traumatic aneurysms of cerebral vessels are frequently located in a distance from the circle of Willis. In penetrating injuries, they may be false. They occur in 3–4% of cases, but rupture is over marked in 50% of cases (Aarabi 1988). Timely angiography is required to reveal them. It is necessary to mention habitual penetrating HI in this section. Different protocols of CT and MRI in different projections are helpful in these cases, for foreign bodies may be made of various materials (metal, wood, plastic, etc.) (Fig. 9.112–9.115). If situated close to cerebral arteries, then direct cerebral angiography should be performed (Figs. 9.116, 9.117).
9.3
Secondary Injuries
These injuries develop secondarily to primary posttraumatic intra- and extracerebral injuries. Diffuse oedema occurs due to diffuse injury or global anoxia (Fig. 9.118). Hyperhydration used in resuscitation may sometimes cause brain oedema but more frequently, it causes oedema of the soft tissues of head.
869
In addition, oedema may develop primarily in absence of any abnormality (Lee 2002). Focal cerebral oedema and cerebral infarctions occur due to dissection and occlusions of vessels, more frequently arteries than veins. Penetrating and nonpenetrating injuries as well as impactions may cause focal ischaemia. Global ischaemia more frequently develops after cardiac arrest. Posttraumatic aneurysms and pseudo-aneurysms, according to Osborn (2002), more frequently occur in the middle cerebral arteries (50%), distal branches of the anterior cerebral arteries (25%), and the petrous or cavernous parts of the internal carotid or basilar arteries (25%). Among other posttraumatic vascular events, arteriovenous fistulas (including carotid cavernous fistula) and thromboses should be mentioned. Fistulas between meningeal arteries and veins are usually identified in combination with fractures of cranial bones; however, they are rarely manifested clinically. Up to 17–36% of patients with penetrating HI had vascular injuries, whereas they were present only in 0.67% of nonpenetrating cases (Osborn 2002).
9.3.1 Brain Oedema MRI is superior to CT in identification of brain oedema, which may compress cerebral ventricles, cisterns, subarachnoid spaces, other brain structures and brainstem (due to impaction), which is why MRI should be performed in headinured patients whose clinical condition deteriorates. Redistribution of liquid in neural and glial cells (swelling) and extracellular space (oedema) occurs in posttraumatic water-electrolyte imbalance. In focal contusions, focal, perifocal, or hemispheric oedema develops more frequently, and less frequently, oedema is diffuse. Diffuse brain swelling is more typical for DAI, which
Fig. 9.112a,b Foreign body (metal fragment) under the skull base on the left, CT: sagittal and coronal projections (a) and 3D reconstruction (b)
870
Chapter 9
Fig. 9.113a–c Foreign bogy in the left orbit. CT (a), T1-weighted imaging (b), and T2-weighted MR-imaging (c) demonstrate a foreign body (wood chip) in the left orbit and its penetration through the optic canal into the cranium. Inflammatory zone around the foreign body is visualised
Head Trauma
871
Fig. 9.114a,b Foreign body in the right temporal area (wood fragment) with adjacent posttraumatic changes in the brain tissue. CT series
Fig. 9.115a–c Penetrating brain injury of the right orbit, foreign body (wood). T1-weighted imaging (a,b) and T2-weighted MR-imaging
(c) with CE demonstrates foreign body penetrating from the orbit into cranium. Contrast—accumulating inflammatory granulations are detected around this body
872
Chapter 9 Fig. 9.116a,b Metal foreign body in the right temporoparietal area. Angiography: a lateral, b direct projections
Fig. 9.117a–e Metal foreign body in the
skull base on the right. Craniography (a,b). CT series (c) and cerebral angiography (d,e) demonstrate anatomical relation between foreign body and bone structures as well as cerebral brain arteries
Head Trauma
873 Fig. 9.118a,b Diffuse brain oedema with compression of the ventricular system and subarachnoid spaces in HI (ninth day). CT
leads to intracranial hypertension and axial brain displacement. It should be noted that in children with HI, brain oedema may develop very early, rapidly progress, and manifest more severely due to higher water content in the brain; however, it may as well rapidly disappear after appropriate treatment. In contrast, in the elderly brain oedema is less prominent, frequently focal, slowly progresses, and reduces. Brain oedema and swelling in HI are in complex interaction with intracranial pressure; however, the latter does not determine severity of every patient condition. Brain oedema is an increase of cerebral volume due to elevation of water content. Diffuse oedema is one of the most life-threatening conditions occurring after HI. Diffuse oedema develops in 20% of severe HI cases and more frequently in children than in adults. Severe forms of brain oedema develop within 24–48 h, and mortality reaches 50%. Five types of brain oedema are distinguished: vasogenic, cytotoxic, hydrostatic, hypo-osmotic, and interstitial (Orrison 2000). Vasogenic oedema is the most frequent type of brain oedema in HI patients and usually reaches its maximum within the first 24 h. Vasogenic oedema is caused by local increase of cerebrovascular permeability, which leads to increase of extracellular liquid content with predominant accumulation in the white matter (Figs. 9.119–9.121). Cytotoxic oedema usually develops due to hypoxic–ischaemic brain damage in HI patients. Cytotoxic oedema reaches its nadir on the fifth day, compared with 24 h in vasogenic oedema. Cytotoxic oedema is caused by accumulation of intracellular fluid, with damage to all types of cells. Dysfunction of the sodium–potassium pump and insufficient excretion of water out of cells are two causes of cytotoxic oedema (Figs. 9.122–9.126). Hydrostatic oedema develops due to abrupt an rise in intravascular pressure, which exceeds normal cerebrovascular resistance. Hydrostatic oedema differs from vasogenic oedema, as the blood–brain barrier remains intact in the former. This type of oedema is seen in patients with significantly raised intracranial pressure and abrupt change of the intravascular pressure, for instance, after decompression craniotomy.
Hypo-osmotic oedema develops due to reduction of plasma osmolarity, which leads to excretion of fluid into the extravasal space. Reduction of plasma osmolarity is seen in some HI patients as a result of hypothalamopituitary system injury. Disordered secretion of antidiuretic hormone is a cause of reduction of plasma osmolarity in these cases. Another cause of hypo-osmatic oedema after HI is excessive intravenous infusion. Interstitial (periventricular) oedema is the result of secondary rise of the CSF pressure in the ventricular system due to developement of posttraumatic hydrocephalus. Direct excretion of fluid out of ventricles into the adjacent white matter is marked (Fig. 9.127). Posttraumatic oedema usually resolves within 2 weeks, frequently with consequent brain atrophy. On CT, oedema is seen as a hypodensive area predominantly in the white matter (subcortical white matter is less resistant to accumulation of fluid than grey matter) and smoothening of white–grey matter border occurs. No accumulation of contrast medium is seen after intravenous CE, unless the blood–brain is damaged. On MRI, oedema is hypointense on T1-weighted imaging and hyperintense on T2-weighted imaging. If the blood–brain barrier is damaged, then accumulation of contrast medium is seen in several areas after intravenous CE. Vasogenic oedema causes increased fluid in the brain (ADC increase), while cytotoxic oedema resulting increased cellular swelling (decrease of ADC). 1H MRS reveals reduction of NAA and elevation of Cho peaks, i.e. destruction of cellular membranes is seen (Fig. 9.128). МRA may reveal decrease of cerebral blood flow and, hence, may poorly visualise intracranial arteries.
9.3.2 Dislocation and Deformation of the Brain (Impactions) Secondary posttraumatic brain injuries may lead to deterioration of patient condition and may be more life threatening than the primary injury. Impactions are related to such injuries. They are deformations or dislocations of brain due
874
Chapter 9
Fig. 9.119a–d Vasogenic oedema around contusion in the right frontal area. CT (a), T2-weighted imaging (b), FLAIR (c), and DWI (d) MRI
Fig. 9.120a–c Contrecoup contusion of the temporal lobes with perifocal vasogenic oedema (8 days after injury). CT (a), T2-weighted imag-
ing (b), and FLAIR (c) MRI
Head Trauma
875
Fig. 9.121a–c Vasogenic oedema around contusion of the left frontal area is hyperintense on T2-weighted imaging (a), FLAIR (b), and DWI (c) (12th day after accident)
Fig. 9.122a–c Severe HI with bilateral contusion of the temporoparietal areas and subdural haematoma on the right. The cytotoxic oedema is better visualised on DWI (c) in comparison with T1-weighted imaging (a) and T2-weighted imaging (b)
876
Chapter 9
Fig. 9.123a–c Cytotoxic oedema in the right temporoparietal area. HI (13th day after accident) oedema is hyperintense in all sequences: T2 (a), FLAIR (b) and diffusion (c)
Fig. 9.124a–c Subdural haematoma in the left frontoparietal area. HI (13th day after accident). Hyperintense area on T2-weighted imaging (a), FLAIR (b), and DWI (c) of the left frontal lobe means cytotoxic oedema
Head Trauma
877
Fig. 9.125a–c Small bilateral subdural haematomas in the right and left temporal areas. T2-weighted imaging (a), T1-weighted imaging (b)
and DWI (c) MRI visualise an ischaemic zone, better revealed on DWI
Fig. 9.126a–d DAI. Damage of corpus callosum. T2-weighted and FLAIR (a,b) and DWI
(c) MRI reveals hyperintense signal in the splenium of corpus callosum, on ADC map— diffusion decrease points out to the cytotoxic oedema (d)
878
Chapter 9 Fig. 9.127a,b Case 1. Axial CT (a) reveals hydrocephalic dilatation of the lateral ventricles and periventricular (interstitial) oedema. Case 2. MRI (b) detects hydrocephalus with interstitial oedema, which is hyperintense on T2-weighted imaging
Fig. 9.128a,b Posttraumatic hydrocephalus with periventricular oedema and gliosis of the white matter of frontal lobes (a). b MRS reveals the Lip–Lac complex peak, NAA peak decrease, and Cho peak increase
Head Trauma
to raised intracranial pressure, changes in the cerebral CSF and blood flow, and imbalance between extra- and intracellular fluid (oedema, swelling). Compression of parenchyma, nerves, and vessels against cranial bones and dural processes (falx, tentorium) are signs of primary injury. Compensatory facilities of the reserve spaces (CSF, vascular, and perivascular spaces) are rather small, and progressive development of impactions results in dislocations of different brain structures. The degree of impaction depends on the site of injury, progression rate, individual anatomic peculiarities, initial atrophy, etc. (Osborn 1991; Reich et al. 1993; Lain et al. 1995; Evans 1999). Impactions frequently lead to severe neurological deficits and even death. The following types of impactions are distinguished: lateral (beneath the falx), transtentorial (ascending and descending) uni- and bilateral, transalar, impaction of cerebellar tonsils,
879
and impaction of brain into the cranial defect (Fig. 9.129). Lateral and descending transtentorial impaction are most frequent in HI. Dynamic CТ and MRI in different projections clearly visualise these conditions. Lateral dislocation is a displacement of the cingulated gyrus beneath the free edge of falx across the median line. As the extent of displacement increases, the extent of the lateral ventricle on the ipsilateral side increases due to occlusion of Monro’s foramen (Fig. 9.130). Compression and dislocation of the anterior or posterior cerebral arteries or their branches, occlusion occurs and as a consequence ischaemia and infarctions occurs. Transtentorial impactions: the descending type is more frequent. In this type of impaction uncus and parahippocampal gyri are medially displaced and seen above the free edge of tentorium (Fig. 9.131, 9.132). In the early stage, the hallmark
Fig. 9.129a–c Types of cerebral herniation in HI in coronal (a), axial (b), sagittal (c) projections. 1 external, 2 lateral (under falx, cingulate), 3 descending transtentorial (central), 4 descending transtentorial (lateral, uncal), 5 ascending transtentorial, 6 basal–temporal–transalar, 7 tonsillar herniation
Fig. 9.130a,b Lateral brain shift in HI. CT demonstrates posttraumatic ischaemic changes in the right occipital area, brain oedema with dislocation of the ventricular system
880
Chapter 9 Fig. 9.131 Descending transtentorial herniation in severe HI. CT shows left temporal lobe contusion with uncal herniation into the tentorial foramen with bilateral compression of the basal cisterns
Fig. 9.132a–d Descending transtentorial herniation in severe HI. CT (a,b) and T2-weighted MR-imaging (c,d). Herniation of the brain tissue into tentorial foramen with compression of the brain stem and ventricular system dislocation to the opposite side are revealed
Head Trauma
of initiated impaction is smoothening of perimesencephalic and suprasellar cisterns ipsilaterally, and the ipsilateral cerebellopontine angle dilates as brainstem is displaced contralaterally to the dislocated temporal lobe. With progression of supratentorial mass effect, impaction of both medial aspects of temporal lobes occurs, which leads to complete obliteration of basal cisterns. The tentorial incisure is filled with temporal lobes and inferior portions of midbrain. The latter is compressed and shortens in its transverse section; paresis or more frequently palsy of oculomotor nerves occurs. Medial displacement of temporal lobes and/or dislocation of brainstem are better seen on coronal MRI. The anterior choroid artery, posterior communicating artery, and posterior cerebral artery are also displaced in the inferior medial direction in severe descending impactions. Infarctions of occipital lobes are caused by compression of the posterior cerebral artery between the brainstem and tentorium cerebelli. Coiling and occlusion of small perforans vessels are frequently seen. These are causes of midbrain and basal ganglia infarctions. Secondary haemorrhages of the midbrain may also occur in transtentorial impactions and are caused by compression of perforans arteries in the interpeduncular cistern. Foci of oedema, ischaemia, and haemorrhagic necrosis in the cerebral peduncle contralateral to the temporal lobe impaction are due to compression against tentorium, when brainstem is displaced from the affected side. Ascending transtentorial impaction is the upward impaction of cerebellar vermis and hemispheres via the tentorial incisure and is frequently combined with infratentorial traumatic injury. On CT and MRI, the superior cerebellar cistern and the fourth ventricle are compressed, and the quadrigeminal lamina and midbrain may also be displaced forward and/ or compressed from beneath. Obstructive hydrocephalus may occur after occlusion of the Sylvian aqueduct. Transalar impactions are rarely seen. They may be ascending due to injury of the middle cranial fossa structures with enlargement of the latter, and descending—the identical event in the frontal region. Displacement of the middle cerebral artery, and temporal and frontal lobe via the large wing of the sphenoidal bone occurs. Impaction of cerebellar tonsils is due to displacement of the latter through the foramen magnum, which is obliterated, and occlusion of the outlet from the fourth ventricle causes hydrocephalus better seen on sagittal MRI. Impactions into the cranial defects occur soon after trauma, open skull fractures, in postsurgical defects, or oedema. Lateral displacement frequently occurs, for instance, of the Sylvian fissure, middle cerebral artery, and the temporal lobe. The brain region, which is out-pouched, acquires shape of fungus and haemorrhages may occur inside it.
9.3.3 Vascular Complications A radiologist should correctly choose the diagnostic tool (CT, MRT, angiography) and software (CTA, MRA, DW MRI, PW MRI, etc.) if a secondary vascular event or its consequences are
881
suspected after HI, according to the radiologist’s knowledge of aetiology and pathogenesis. Several important aspects should be mentioned: • Vascular complications differ in pathogenesis and clinical consequences in penetrating and nonpenetrating HI. • Hemodynamic changes in the brain after HI occur: focal, regional (vasospasm, infarctions), or diffuse. • Possible causes of clinical deterioration may be rupture, injury, or dissection of a vessel, formation of pseudo-aneurysm or fistula. • CT and MRI findings without CE vary depending on the type of lesion –– Focal cervical haematoma should be differentiated from a pseudo-aneurysm and dissection of the carotid artery –– Hypodensity of the white matter and cortical layers of the cerebral hemispheres may occur due to ischaemia or vasospasm –– Secondary infarctions after impaction: descending tentorial, occlusion of the posterior cerebral artery; beneath falx, occlusion of the anterior cerebral artery, and central, occlusion of perforans vessels (Figs. 9.133– 9.135). Angiography is mandatory in blunt and penetrating cervical wounds, as it may reveal occlusion of the carotid arteries, rupture and dissection of intima, arteriovenous fistulas, and vasospasm—diffuse or local narrowing of vessels. Carotid and vertebral artery territories are examined (special attention should be paid to their petrous parts), as well as anterior and middle cerebral arteries (Figs. 9.136–9.138). CTA showed that it is more specific and sensitive in diagnosis of cervical vessels injuries (especially in penetrating ones), as it ascertains unevenness of walls, and changes in calibre and defects of intra-vessel accumulation of contrast medium with high precision. MRA identifies vascular occlusions, regional hypoperfusion, and acquires hyperintense signal on DWI due to limited diffusion in the brain. CTA and MRA may clearly differentiate contusion lesions and haemorrhages due to rupture of a traumatic aneurysm, but if brain injury is massive, then CTA is preferable (Fig. 9.139). Examination of patients with suspected arteriovenous fistulae should be made only with cerebral angiography. All phases of blood supply and collateral blood supply should be examined (Figs. 9.140–9.144). Thus, in conclusion it should be noted that CT is the main neuroimaging technique in the acute period of HI, as it obtains data about type of brain injury, cranial fractures, extra-, and intracerebral haemorrhages quite swiftly. MRI is indicated if clinical findings do not correlate with CT findings, especially in patients in coma, to reveal small focal lesions, brainstem involvement, DAI, and brain oedema.
9.3.4 Brain Death Brain death is an anatomic and physiological complex of complete and irreversible loss of all cerebral function. However,
882
Chapter 9
Fig. 9.133a,b Posttraumatic changes in frontal lobes, severe ischaemia in the region of the right PCA. Second week after accident. CT
Fig. 9.134a–c Secondary ischaemia caused by HI. CT at 3 (a) and 7 (b) days, and 2 weeks (c with CE) after accident demonstrates ischaemic
lesion in the region of left PCA alongside with multiple contusions
Head Trauma
883
Fig. 9.135a–e Secondary ischaemia of the
right basal ganglia resulting from severe HI. CT (a) and T1-weighted imaging (b), T2-weighted imaging (c), FLAIR (d), and DWI (e) MRI visualise ischaemic areas with typical hyperintense signal on DWI in projection of the right deep subcortical structures
Fig. 9.136 Posttraumatic pseudo-aneurysm of the extracranial segment of the ICA resulting from an injury at the cervical level (angiography)
884
Chapter 9 Fig. 9.137a,b Posttraumatic pseudo-aneurysm of the siphon of left ICA. Cerebral angiography in the lateral (a) and direct (b) projections
Fig. 9.138a–d Partially thrombosed posttraumatic saccular aneurysm of the ACA (2 years after the head trauma). a CT, b MRI, c,d DSA
Head Trauma
885
Fig. 9.139a–f Secondary damage in HI. Damage of squama of right temporal bone, traumatic damage of the right frontotemporal area, oe-
dema, and descending transtentorial herniation. Vessels of the MCA and PCA on the side of damage are poorly visualised on CTA
Fig. 9.140a,b Posttraumatic arteriovenous fistula. Pathological dumping flow from the right vertebral artery to the venous system of the
right posterior cervical region. Angiography: a direct and b lateral projections
886
Chapter 9
Fig. 9.141a–c Posttraumatic carotid–cavernous fistula in combination with posttraumatic pseudo-aneurysm of the extracranial segment of
the ICA. Angiography Fig. 9.142 Posttraumatic carotid–cavernous fistula. Lateral angiography demonstrates pathological flow of blood from the ICA into the cavernous sinus, the superior orbital vein, and facial veins
Fig. 9.143a,b Posttraumatic arteriovenous fistula. Selective angiography of the vertebral artery reveals pathological flow from the left vertebral artery into the venous plexus at C1 level (a direct and b lateral projections)
Head Trauma
887
Fig. 9.144a–d Posttraumatic fistula of branches of ECA and VA. Selective angiography. a first observation, b second observation, c,d third observation
clinical diagnosis, first of all, and modern neuroimaging may only confirm but not replace clinical criteria. Brain death occurs due to severe traumatic or ischaemic brain injury; however, precise pathophysiology of intracranial blood flow in brain death is yet to be further elucidated. As is believed, the main cause of brain death is rise of intracranial pressure due to diffuse brain oedema (Kornienko 1981; Walner 1998; Ishii et al. 1996; Nakahara et al. 2001). CT reveals diffuse brain oedema in which white–grey matter differentiation smoothens, gyri are oedematous, CSF spaces are compressed, and density of cerebellum changes (it becomes higher than that of cerebral hemispheres); with a background of hypodensive brain tissue basal cisterns may look hyperdensive. After CE, there is no accumulation of contrast medium in cerebral vessels (MCA, BA, PCA) (Fig. 9.145).
MRI reveals swelling of cerebral gyri, poor white–grey matter differentiation, and absence of fluid surrounding the brain. Prolongation of T1 and T2 relaxation times is seen in the affected gyri and grey matter nuclei. There is no signal of intracranial blood flow, the central brain impaction is seen— basal regions of cerebral hemispheres, midbrain, and cerebellar tonsils are displaced downward, and both temporal lobes are compressed by the tentorial incisure. Accumulation of contrast medium is seen only in facial structures. DWI reveals diffuse hyperintensity of the cerebral hemispheres with reduction of ADC. Angiographic examinations (angiography, МRА, CТА) fail to reveal intracranial blood flow—it is absent above the supraclinoid part of the internal carotid arteries and in the distal parts of the vertebral arteries (Fig. 9.146).
Fig. 9.145a,b Brain death. Severe HI. CT reveals diffuse brain oedema, absence of the border between the grey–white junctions
888
Chapter 9
Head Trauma
9 Fig. 9.146a–o Severe HI. Brain death. T2-weighted imaging (a), FLAIR (b), T1-weighted imaging (c) and T1-weighted imaging with CE (d) MRI demonstrate diffuse brain oedema, haemorrhagic lesion in the left thalamus. 1H MRS in the right (e, f) and left (g, h) deep subcortical structures reveals decrease of the NAA peak (reflects decrease of undamaged neurons concentration), increase of the Cho peak (relates with the destruction of the cellular membranes and release of choline from them), and decrease of the Cr peak (linked the inhibition of energy exchange). The Lac peak reflects the activation of anaerobic glycolysis. The colour maps (i–k) reflect the distribu-
889
tion of the different metabolites: the heterogenic Cho concentration as a consequence the cellular membrane destruction; concentration of Cr close to normal level remains local in projection of the left subcortical ganglia, and it is decreased in all other parts of brain; and the increased concentration of Lac together with decreased concentrations of undamaged neurons is observed in the examined volume. There are two shunting systems in the body of lateral ventricle. MRA (l) and CTA (m–o) demonstrate no filling of the intracranial segments of cerebral arteries
890
9.3.5 Consequences and Complications of Head Injury The following forms of HI consequences are distinguished regarding morphological substrate: tissue, CSF circulation, and vascular consequences. According to clinical and neuroimaging findings, the first group consists of posttraumatic focal and diffuse atrophy, cortical and subcortical gliosis, encephalomalacy, posttraumatic skull defects, acquired encephalocele, and meningoencephalocele. Meningoencephalitis, empyema, abscess, and meningitis compose a separate subgroup. Consequences of HI related to CSF circulation are posttraumatic hydrocephalus, porencephaly, chronic hygromas, and CSF fistulas. Vascular consequences are aneurysms (true and pseudoaneurysms), arteriosinus fistulas, sinus-thromboses, and delayed and chronic haematomas. Thorough history and neurological deficit, volume, type and location of brain tissue defect, and CSF circulation are those aspects a radiologist should take into account when interpreting CT and MRI findings. However, a radiologist should remember that there exist such brain injuries that cannot be identified with modern neuroimaging techniques. Traditionally, radiologists were more interested in changes of brain anatomy after HI. It was thought that CT was an adequate modality in head-injured patients. However, MRI studies of HI showed that this technique is more reliable in HI examination, especially in subacute and chronic stages (Young 1996). Neuroimaging studies that concentrated on descriptive anatomy demonstrated that head- injured patients may develop different consequences and complications within several hours, several weeks, months, or even years after injury. That is why it is always necessary to have them in mind and adopt diagnostic techniques. In the early period after HI, such lesions may be seen as delayed intracerebral, subdural and epidural haemorrhages, pneumocephaly, and CSF leakage. In
Chapter 9
the later period cerebral atrophy, hydrocephalus, acquired encephalocele, and meningoencephalocele are more frequently diagnosed. CSF fistulas and CSF leakage also frequently occur in the delayed period after HI. Until now, CT has been considered a method of choice to study the early period after HI. MRI is considered a method of choice to study subacute conditions and delayed consequences of HI.
9.3.5.1
Consequences with Involvement of Brain Tissue
9.3.5.1.1 Posttraumatic Focal and Diffuse Atrophy, Encephalomalacy, and Gliosis Brain atrophy in HI patients may be focal or diffuse. In focal lesions, necrotic detritus dissolve within 6–12 months after injury and are replaced by CSF cavities, with brain atrophy of various extents. In focal atrophy, cerebral gyri are reduced in size, the CSF spaces are compensatorily dilated at the site of injury, and the adjacent parts of cerebral ventricles are enlarged (Figs. 9.147, 9.148). Cysts are surrounded by gliosis and haemosiderin cicatrices. In these cases, CT and MRI demonstrate focal encephalomalacy and porencephalic cysts, widening of cortical sulci, and ventriculomegaly (Figs. 9.149–9.151). Sometimes it is difficult to differentiate encephalomalacy and porencephaly on CT, as in both cases a hypodense cyst is identified. Porencephalic cyst contains only CSF and is more hypodense (isodense to the CSF) than an area of encephalomalacy is. MRI is more informative, especially if FLAIR sequence is used. Porencephalic cyst on FLAIR is characterised by hypointense signal and clear connection with the lateral ventricle, whereas an area of encephalomalacy is heterogeneously hyperintense. Even several months (or, rarely, years) later, FLAIR images in contrast to CT may visualise hyperintense signal of brain tissue on the periphery of posttraumatic cysts or focal brain
Fig. 9.147a,b Dynamic CT in the acute (a) and residual (b) stages of HI. CT (b) reveals atrophy of frontal lobes and dilatation of both ventricles
Head Trauma
Fig. 9.148 Cystic, gliosis changes in the right frontotemporal area
as a result of HI. Hydrocephalus, asymmetrical dilatation of lateral ventricles. CT
891
Fig. 9.149 Consequences of HI. Cystic transformation in the right frontoparietal area
Fig. 9.150a,b Consequences of HI. Cystic encephalomalacy of the left frontal area. T2-weighted imaging (a) and T1-weighted MR-imaging (b)
892
Chapter 9
Fig. 9.151a–c Consequences of HI. MRI. Cystic–gliosis changes in the left temporal area, dilatation of the left lateral ventricle. Herniation of brain tissue into skull defect
Fig. 9.152a–c Posttraumatic changes of the frontal–basal location. T2-weighted imaging (a) and T1-weighted MR-imaging (b,c) demonstrate cystic transformation of the brain, hyperintense areas on the cyst periphery on T1-weighted imaging indicates gliosis
atrophy—posttraumatic gliosis (Figs. 9.152, 9.153). These changes may be mildly hyperintense on T2-weighted imaging and may not be seen at all on T1-weighted imaging. Diffuse brain atrophy frequently develops after DAI, and is characterised by prominent dilatation of cortical sulci and the ventricular system, without signs of its occlusion (Figs. 9.154, 9.155). Periventricular changes of MRI signal usually seen in hydrocephalus are absent. Less frequently, atrophy of infratentorial structures develops. Cerebellar atrophy is manifested by dilatation of the subarachnoid spaces and cistern of the posterior fossa. The extent of brain atrophy after
HI depends on the remoteness of the latter (Fig. 9.156). MRI is a unique method that identifies corpus callosum atrophy in vivo, which is seen only after severe DAI. As well, MRI picture of corpus callosum atrophy correlates with clinical signs of disconnection of the cerebral hemispheres. Reduction in size and volume fornix and hippocampus may also be found in the delayed period after head trauma. Modern neuroimaging allows studying not only structural, but also hemodynamic and metabolic brain changes in the delayed period after HI (Fig. 9.157).
Head Trauma
893
Fig. 9.153a–c Consequences of HI. T2-weighted imaging (a), T1-weighted imaging (b), and FLAIR (c) MRI reveal atrophy of the frontal lobes
with formation of the gliosis transformation in the cortical–subcortical departments alongside with marked hydrocephalus and periventricular oedema
Fig. 9.154 Dynamic CT (3, 8 days, and 2 months after accident) reveals atrophic brain changes after HI
Fig. 9.155 Diffuse brain atrophy resulting from severe HI (dynamic CT: 4 days and 1 month after injury)
894
Fig. 9.156a–f Consequences of severe HI persistent vegetataive state.
Two years after injury (diagnosis was DAI, the epidural haematoma in the right temporoparietal–occipital area, secondary ischaemia in the region of the right PCA). At time of present examination: axial T2-weighted imaging (a), FLAIR (b), and sagittal T1-weighted MRimaging (c) reveal the marked cystic–atrophic brain changes includ-
Chapter 9
ing brainstem atrophy and a cyst in the splenium of atrophic corpus callosum. The increased diffusion and decreased fractional anisotropy is revealed in the midbrain area according to the diffusion map (d) and the anisotropy map (e). Reconstruction of 3D images (f) detects marked asymmetry of projection corticospinal tracts and their density decrease
Head Trauma
Fig. 9.157a–d Consequences of head trauma (8 month after injury). The examination of the patient with the
persistent minimal consciousness state, tetraparesis and hyperkinesis in the left hand. Beside moderate atrophic changes (a FLAIR), MRI reveals the asymmetric density decrease in the left projection tracts (b DTI). Blood flow examination (CT perfusion, c CBF) reveals blood flow increase in the right deep subcortical area; PET examination (d) shows increased glucose metabolism
895
896
9.3.5.1.2 Posttraumatic Skull Defects The problem of restoration of cranial integrity after large posttraumatic cranial defects (PCD) is still exists. Large experience of over than 1,000 cases obtained at the Burdenko Neurosurgery Institute allowed us to elaborate the classification of posttraumatic skull defects including such criteria as aetiology, location, condition of adjacent soft tissue, concomitant posttraumatic changes, and many others. To avoid reciting of all items of this classification we would like to emphasise that in relation to aetiology, intrinsic traumatic and iatrogenic (postsurgical) bone defects are distinguished. The latter are caused by resection or decompression trepanation after surgery for HI. Craniography and CT are basic diagnostic tools for posttraumatic skull defects. Craniography in two standard projections is done initially. Target craniography is necessary if peculiarities of defect location are present or the control of an implant positioning af-
Chapter 9
ter surgery is required. Craniography identifies location, size, and contours of the defect and visualises any inflammatory complications (osteomyelitis) present (Fig. 9.158). Soft tissue and bone regimen CT should be performed, because presence of bone defect means that the patient must have focal and/or diffuse changes of brain parenchyma (cystic, cicatrices or adhesive changes, porencephaly, meningoencephalocele, etc.). Another advantage of CT compared with craniography is a capacity for precise assessment of craniobasal and cranio-orbital posttraumatic skull defects. Spiral CT has been more widely used recently as it detects size, shape, and location of posttraumatic skull defects with more precision. For this purpose, 3D reconstruction is used, which is construed of a set of primary axial scans. The most reliable reconstruction is done with 3-mm slice thickness (Figs. 9.159–9.161). In addition, 3D reconstruction not only obtains volume images of a skull from any point of view, but also further models implants ideally fitted to bone defects (Fig. 9.162). This technique is called computer stereolythography. It is especially important in modelling of cranio-orbital bone defects before an operation.
9.3.5.1.3 Acquired (Traumatic) and Postsurgical Encephalocele and Meningoencephalocele
Fig. 9.158 Osteomyelitis of the bone flap and edges of skull defect
after HI and osteoplastic trepanation (lateral X-ray)
In large posttraumatic skull defects, especially after surgery, adjacent brain tissues may be displaced into a bone defect, together with meninges and CSF spaces. If brain tissue pouches out of the defect, then it is called an encephalocele. If brain tissue and meninges pouch out of the defect, then it is called meningoencephalocele (Fig. 9.163). Cases are described in which posttraumatic meningoencephalocele developed in combination with CSF leakage and hydrocephalus. CT and MRI clearly visualise the content that pouches out of the cranial bone defect—CSF and/or brain tissue. On CT, the CSF structures are isodense to the normal ventricular CSF; affected brain tissue looks hypodense to intact brain tissue due
Fig. 9.159a–c Bone defect after surgical wound treatment and resection of squama of the frontal bone, the accompanying focal contusion of
the frontal lobe on CT (a,b). 3D CT (c) demonstrates shape of the bone defect
Head Trauma
897 Fig. 9.160a,b Posttraumatic defect of the frontal–craniofacial area with penetration into anterior cranial fossa base. 3D CT: a view from the front, b from above
Fig. 9.161a,b Posttraumatic defect of the frontal–craniofacial area with penetration into the anterior cranial fossa
base (a,b different 3D CT projections)
Fig. 9.162a,b Posttraumatic skull defect. 3D CT before operation (a), after bone defect closure using computer stereolythography (b)
898
Chapter 9 Fig. 9.163a,b Consequences of HI. Meningoencephalocele in the right parietal bone defect, hydrocephalic dilatation of the ventricles. T1-weighted imaging (a) and T2weighted MR-imaging (b)
to necrosis and oedema caused by strangulation in the bone defect (Fig. 9.164). On MRI, brain tissue inside the encephalocele also looks abnormal; it is heterogeneously hypointense on T1-weighted imaging and hyperintense on T2-weighted imaging. Microhaemorrhages seen as hyperintense foci may often be found on T1-weighted imaging. FLAIR is more sensitive to these abnormalities (Figs. 9.165, 9.166). In large posttraumatic skull defects, brain dislocation to the affected side may be seen leading to midline shift and pulling of the ipsilateral ventricle. Intrusion of brain tissue into the skull bone defect may lead to strangulation, oedema, and hyperaemia, as was mentioned above. In severe injury, we observed cases when meningoencephalocele was combined with carotid cavernous fistula (Fig. 9.167). Changes of blood flow in the strangulated brain tissue may be effectively assessed by CT or MRI perfusion (Figs. 9.168, 9.169). The concept of “growing cranial fracture” exists in clinical practice of neurotraumatology. It is a rare complication seen in children of 1–3 years of age and is characterised by a progressive widening of the fracture line. Most linear fractures in children and adolescents are usually treated without consequences. Growing cranial fractures develop due to constant
Fig. 9.164 Consequences of HI–meningoencephalocele of the both temporal area, CT
contact of the CSF and bone defect margins. Rapid growth of brain tissue within the first years of life is another causative factor. Constant pulsation of the CSF in the area of cranial fracture causes resorption of an adjacent bone. Craniography or CT reveals diastasis of the fracture line. Further examinations are required to confirm widening (Fig. 9.170). Prevalence of growing fractures in children varies from 0.5 to 10% of all cranial fractures (Husson et al. 1996).
9.3.5.1.4 Infectious Complications of Head Injury In large posttraumatic skull defects (especially of skull base) and brain contusions as well as in cases with inadequate treatment, different severe infectious complications may develop in the posttraumatic period such as encephalitis, abscess, subdural and epidural empyema, meningitis, and ependymitis (ventriculitis). Infectious pathogens may penetrate into the brain after HI via two routes, (1) haematogenous dissemination from remote foci and (2) direct invasion through the bone defect (in skull base fractures), from infectious lesions (in purulent otitis, mastoiditis, sinusitis), or perineurally alongside cranial nerves in craniofacial injury. Encephalitis and abscess. Encephalitis and abscess are the result of extracerebral infection and are frequently seen in otitis, mastoiditis, sinusitis, skin infections, or penetrating cranial injuries, or may be caused by osteomyelitis. The targets of infection are contusion lesions, petechial haemorrhages, and foci of oedema. Attenuation of brain tissue in encephalitis may lead to formation of an abscess. On CT without CE, encephalitis is characterised by a large, hypodense area with unclear borders. Initially this area may be restricted to the white matter or even to a certain anatomic region or cerebral lobe (Fig. 9.171). Smoothening of subarachnoid fissures may be seen, and CE may be absent. Further progression may lead to expansion into the grey matter or the contralateral hemisphere (generalisation) (Fig. 9.172). Hyperdense foci start to appear in hypodense areas—haemorrhages. The active phase of inflammation is accompanied by blood– brain barrier impairment and a typical gyral type of CE (repeating contours of gyri).
Head Trauma
899
Fig. 9.165a–c Consequences of HI. Encephalocele of the left frontal area (1 month after injury). T1-weighted imaging (a), FLAIR (b), and T2-weighted MR-imaging (c) visualise large changes of the brain tissue with its prolapse into the bone defect
Fig. 9.166a–c Meningoencephalocele in the ethmoid bone (18 days after injury). T2-weighted MR-imaging (a,b); 45 days after injury,
T2-weighted imaging (c) detects pneumocephalus of the right frontal area
900
Chapter 9
Fig. 9.167a–d Combination of posttraumatic meningoencephalocele of the left fronto-orbital area and left carotid–cav-
ernous fistula (8 months after injury). a CT, b MRI, c,d cerebral angiography
Fig. 9.168a–c Posttraumatic meningoencephalocele. CT perfusion examination demonstrates hyperaemia zone of the prolapsed area of the
brain tissue
Head Trauma
Fig. 9.169a–f Consequences of HI, 4 months after severe HI. CT (a) detects open internal hydrocephalus, cystic brain changes in the area of its prolapse into the postoperative bone defect (the meningoencephalocele). CT perfusion identifies decreased blood flow values and blood volume in the area of prolapsed brain tissue and in frontal
901
lobes (b,c). After ventriculoperitoneal shunting, bone defect plasty in the frontoparietal area (d CT), a relative normalization of blood flow and blood volume in the left temporoparietal area is observed; however, the blood flow continues to decrease (e CBF, f CBV) in the frontal lobes
Fig. 9.170a,b Growing fracture. Dynamic CT in bone window demonstrates enlargement of the fracture line in 1 month
902
Chapter 9
Fig. 9.171 Encephalitis of the left temporoparietal area after HI. CT reveals hypodensive area predominantly in the white matter
Fig. 9.172 Encephalitis after HI. CT series
MRI is more sensitive than is CT in diagnosis of early infectious complications. Т1-weighted imaging may reveal hypointense signal in the area of primary inflammation along with smoothening of sulci and mass effect. Т2-weighted imaging and FLAIR images are more informative and better show the abnormal area of hyperintense signal represented by oedema (Fig. 9.173). Accumulation of contrast medium is absent in the early stage. In the high point of encephalitis, markedly hyperintense signal appears in the white matter with subsequent
expansion of abnormality into the grey matter. The picture of gyri is lost, and lateral ventricles may be narrowed or moderately dilated. CE gives prominent accumulation of contrast medium alongside the gyri in the affected region (Fig. 9.174). Progression of inflammation with necrosis of its central part may lead to formation of an abscess. Prevalence of posttraumatic abscesses is highly variable and comprises 2–26.7% . On CT with CE, an abscess is round or oval with peripheral zone of accumulation of the contrast medium, which is a hall-
Fig. 9.173a,b Encephalitis resulting from HI. T2-weighted imaging (a) and T1-weighted imaging (b) MRI reveal signal changes from the white and grey matter
Head Trauma
Fig. 9.174a–d Focal meningoencephalitis of the left temporoparietal area (HI complication). Series T2-weighted imaging (a), FLAIR (b), DWI (c), and T1-weighted imaging with CE (d) demonstrate a spread
903
area of signal change from the brain tissue and thickened dura matter. Brain tissue and dura matter accumulate contrast media
904
Chapter 9
Fig. 9.175 Posttraumatic abscess of the left frontoparietal area. CT with CE
Fig. 9.176 Posttraumatic abscess of the right frontal area. CT with CE
mark of its capsule (Figs. 9.175, 9.176). Thickness of walls may be small (1–3 mm); less frequently it reaches 5–6 mm, and usually it is identical throughout the whole length. In deepseated abscesses, the wall may be uneven with thinner medial contour. It is explained by poor vascularisation of deep brain parenchyma, and this factor determines rupture of an abscess into the ventricular system, with formation of filial abscesses. Since the abscess centre becomes necrotic, Т1 and Т2 relaxation times prolong, and the central part becomes hypointense on Т1-weighted imaging and hyperintense on Т2-weighted imaging. Necrotic purulent masses are hyperintense in all sequences to CSF (Fig. 9.177). FLAIR images show hypointense lesion with perifocal hyperintense signal of vasogenic oedema. On DWI, the abscess content is markedly hyperintense compared with the surrounding oedema and brain tissue due to high viscosity and cellular content of pus (Fig. 9.178). It is possible to differentiate abscesses from necrotising tumours in this regimen in nearly 100% of cases. MRS reveals in the centre of an abscess such resonance peaks as Lac, Ala, acetate, and succinate (Kim et al. 1997). However, single MRS findings are nonspecific and insufficient to diagnose an abscess as seen in different malignant tumours with central necrosis (for instance, in glioblastomas). Clinical improvement in patients with brain abscesses correlates with reduction of CE in the capsule, reduction of the central part volume, and the extent of perifocal oedema expansion. Subdural and epidural empyema. Infection may also expand into the subdural and epidural spaces, with development of subdural and epidural empyemas. The most frequent cause of subdural and epidural empyemas after HI is purulent sinusitis, less frequently, otitis, penetrating skull injuries, craniotomy, and osteomyelitis of the bone graft and the edges of bone defects. The most frequent locations of subdural empyemas are the convex brain surface
above the cerebral hemispheres (80%), interhemispheric fissure (12%), and frontal region, for epidural empyemas (Sze and Lee 1999). On CT, acute empyema appears as a lens-like, hypodensive area (containing pus) adjacent to the internal cranial surface or falx. In some cases, only mass effect predominates on CT and empyema itself is isodensive. Oedema may be seen in the adjacent white matter. On CT with CE, an area of accumulation of contrast medium is seen which separates epi- and subdural suppurations and the adjacent brain tissue due to formation of granulations on the leptomeningeal border of empyema, as well as focal inflammation of the adjacent brain tissue. Recently MRI has become a method of choice for diagnosis of subdural and epidural empyemas even of small volumes. Multiplanar examination (especially when coronal section is used) improved diagnostics for cases with paratentorial or subtemporal suppuration (Figs. 9.179, 9.180). Besides, MRI helps to differentiate between subdural and epidural empyema. Dura mater appears as hypointense rim separating brain tissue and the epidural space. Suppuration is hyperintense on T1-weighted imaging and T2-weighted imaging. CE provides higher reliability in diagnosis of empyemas as it produces a clear contour around a suppuration. Meningitis. The pathogens of posttraumatic meningitis may be of a bacterial, fungal, viral, or parasitic nature. They are disseminated via haematogenic or contact routes; meninges are not so resistant to infection, and CSF motion alleviates their distribution above the brain surface, along the vertebral channel and cerebral ventricles, i.e. meningitis is always a cerebrospinal disorder. It is seen in 1.3–4.8% of all cases of HI. In the initial stages of meningitis, CT and MRI pictures may be normal and may remain normal if timely and adequate treatment is performed. When infection continues to develop, mild hyperdensity may be seen in basal cisterns, interhemispheric fissure, and choroid plexus, which is the result of the combination of hypervascularity of infected meninges
Head Trauma
905
Fig. 9.177a–c Posttraumatic abscess of the right frontal area: CT with CE (a), and MRI in T2-weighted imaging (b) and T1-weighted imaging with CE (c)
Fig. 9.178a–d HI and development of multiple abscesses accompanied by the ventriculitis and encephalitis. CT (a), MRI on T2-weighted imaging (b), T1-weighted imaging (c), DWI (d)
906
Chapter 9
Fig. 9.179a–h HI and development of multiple empyemas of the left hemisphere accompanied by the encephalocele (2 months after injury).
CT (a), MRI in T2-weighted imaging (b,c), T1-weighted imaging (d,e), and FLAIR (f) sequences. CE improves visualisation of the purulent cavities in the affected brain hemisphere (g,h)
Head Trauma
907
Fig. 9.180a–d Posttraumatic bone defect of the left parietotemporal area (severe HI). T2-weighted imaging (a), T1-weighted imaging (b), and T1-weighted imaging with CE (c,d) visualise the empyemas of small size adjacent to the bone defect area
and choroid plexus, and presence of fibrin of haemorrhagic exudate in the subarachnoid spaces. Lateral and third ventricles may be narrowed due to diffuse brain oedema. CE around the brain is frequently absent on CT, due to hyperdensity of the internal cranial bone lamina. MR findings in meningitis resemble those of CT. However, MRI findings are more prominent and specific. Dura mater looks thickened and hyperintense on T1-weighted imaging, while MRI signal is identical to that of grey matter. Narrowing of subarachnoid spaces, and thickening and hyperintensity of dura mater are better seen on FLAIR. If clinical manifestations are prominent, then CE is typical in meninges (Fig. 9.181), which may be peripheral, diffuse (around the whole brain), or focal localised, for instance, only in basal cisterns or above the single lobe. Thrombosis of sinuses (revealed on angiography), hydrocephalus with the subsequent calcinosis of meninges may complicate meningitis. Ependymitis (ventriculitis). Ependymitis may develop secondarily to leptomeningitis in retrograde expansion of infection, after spontaneous or iatrogenic rupture of an abscess into the ventricles, or if shunts placed for hydrocephalus are infected.
On CT with CE, bacterial meningitis is seen as a thin accumulation of contrast medium in the ependyma of the lateral ventricles—focal or diffuse (Fig. 9.182). In severe cases Т1-weighted imaging may reveal prominent hyperintense signal in the periventricular area, and Т2-weighted imaging may reveal hyperintense signal around cerebral ventricles, which is more focal and irregular than in hydrocephalus (Fig. 9.183). Corpus callosum is frequently affected in ependymitis. Accumulation of contrast medium is more often seen along the walls of the lateral ventricles.
9.3.6 Fluid Dynamic Consequences of Head Injury 9.3.6.1
Hydrocephalus
Dilatation of the ventricular system is seen in 0.7–3.9% of patients with HI. Pathogenesis of posttraumatic hydrocephalus is variable. Dilatation of ventricles may develop after occlusion of narrow passages of the CSF system, with blood clots (so-called obstructive hydrocephalus) in the late period after HI, secondary to brain atrophy and resorption impairment (aresorptive hydrocephalus). Common classification of hy-
908
Chapter 9
Fig. 9.181a–e HI complication–meningitis.
T2-weighted imaging (a), T1-weighted imaging (b), and T1-weighted imaging with CE (c–e) visualise pathological thickening and contrast accumulation in the dura matter around brain hemispheres and falx
Fig. 9.182 HI complication. CT series visualises contrast accumulation in the ependyma of the lateral ventricles and marked decrease of the white matter density (encephalitis and ventriculitis)
Head Trauma
909
Fig. 9.183a,b Encephalitis and ventriculitis, HI complications. T2-weighted imaging (a) and T1-weighted imaging (b) MRI demonstrate the hyperintense areas in the white matter
drocephalus adopted by the Burdenko Institute of Neurosurgery is applied for posttraumatic hydrocephalus (Konovalov et al. 2002). CT and MRI are main techniques for examination of patients with hydrocephalus; invasive and noninvasive techniques are used. Examination of CSF spaces on CT is based on relationship between brain tissue and CSF. CSF is hypodensive regarding brain parenchyma. Iso- or hyperdensivity to brain tissue CSF means fresh blood or its decay products in the CSF. The major disadvantage of CT is that it does not study CSF circulation, and it is difficult to identify brain lesions located close to CSF when their density is equal to that of the CSF. CTCG better demonstrates CSF spaces of the brain. Contrast medium is introduced intrathecally to study its distribution along CSF pathways of the brain and spinal cord. CSF is hypointense on T1-weighted imaging and hyperintense on T2-weighted imaging except in narrow ventricular segments like Sylvian aqueduct, interventricular foramina, and outlet of the fourth ventricle, where MRI signal is usually hypointense. Hypointense signal of the CSF in these regions is normal. Mechanism of flow-void signal in the aqueduct is similar to what we see in blood flow. It is better seen on T2weighted imaging and proton density images on axial and sagittal scans through the aqueduct. The most rapid pulse or volume CSF is hypointense, whereas peripheral relatively slow (laminar) CSF flow is hyperintense. Flow-void phenomenon in the Sylvian aqueduct is an indicator of pathological condition wherever it develops (occlusion superior or inferior to the aqueduct). Constant flow-void phenomenon in the aqueduct is frequently seen in communicating hydrocephalus
due to dilatation of the aqueduct and increased turbulence of the CSF flow. Prominent flow-void phenomenon may also be physiological in children due to tachycardia and larger volume of choroid plexus compared to adults. Pulse sequences like FLAIR, PSIF, and many others (the term depends on the software manufacturer) are used to examine the CSF system by MRI. Though they give some information about CSF circulation, it is better to study the latter by cine phase contrast images (Fig. 9.184) (Bradley et al. 1996; Arutiunov et al. 2000).
9.6.3.1.1 Obstructive Hydrocephalus Obstructive hydrocephalus is usually combined with extraor intracerebral traumatic lesions that cause occlusion of CSF pathways. Parts of the CSF system that are proximal to such lesions dilate due to increased volume and pulse pressure of CSF. The most frequent cause of obstructive hydrocephalus is the blockade of the CSF pathways with blood, especially in narrow sites. Such a hydrocephalus is less frequently seen than are other forms. CТ is the most effective method of visualisation of blood clots in cerebral ventricles in the acute HI stage. However, it requires high-resolution acquisition of thin slices, especially at the level of foramen magnum and midbrain. MRI is more helpful in the subacute period—blood is bright on T1-weighted imaging and is clearly seen together with hypointense signal of the CSF. It is preferable to visualise acute blood on MRI Т2 and Т2* sequences, when blood looks dark, whereas CSF
910
Chapter 9
Fig. 9.184a–d Posttraumatic hydrocephalus. Sagittal projection T1-weighted imaging (a),
PSIF (b), and phase-contrast MRI (c,d) demonstrate CSF flow on the aqueduct of cerebrum, fourth ventricle and basal cisterns in different phases of the cardiac cycle
remains bright. MRI exceeds CT in precise assessment of the Sylvian aqueduct and fourth ventricle outlets. If there is an abrupt and prominent raise of the intraventricular pressure in the periventricular spaces reflecting an interstitial oedema typical for rapidly developed occlusion, then hypodense areas may be seen on CT (which are hyperintense on T2WI and FLAIR). In communicating of the aresorptive hydrocephalus, symmetrical dilatation of all parts of the ventricular system is present. Obstruction usually involves convex subarachnoid spaces but may also involve basal cisterns. Superior level obstruction more frequently involves arachnoid pili along the superior sagittal sinus and choroid plexus of lateral ventricles with the subsequent impairment of CSF resorption and development of hydrocephalus—the main cause for that is presence of blood in subarachnoid spaces and ventricular system after HI. Impairment of the CSF resorption occurs even in the spinal subarachnoid spaces. Blood resorption and aseptic inflammation lead to sclerosis (or desolation) of arachnoid pili and impairment of the CSF circulation. CT and MRI show diffusive dilated cerebral ventricles and the dilated convex sulci imitating atrophic changes (Figs. 9.185, 9.186). Increased CSF pressure in lumbar puncture may help in diagnosis of these patients. Sylvian aqueduct may also be dilated. On T2-weighted imaging, flow-void phenomenon is absent not only in the aqueduct, but also proxi-
mally, in the third ventricle and distally, in the dilated fourth ventricle. Adams and Hakim (1965) described group of patients with reduction and slow CSF resorption in normal CSF pressure and called that condition normotense hydrocephalus. At present normotense hydrocephalus is defined as a combination of chronic communicating hydrocephalus and atrophic parenchymal brain changes. This type of hydrocephalus frequently develops after HI. After surgical interventions (shunting, etc.), CT and MRI are the main methods of assessment of the CSF system. According to our data, moderate narrowing of ventricles and reduction of periventricular oedema is seen in 1–2 weeks after shunting; 3–4 weeks after shunting ventricles continue to decrease in size, and 3 months after shunting their sizes normalise and periventricular oedema disappears.
9.6.3.1.2 Traumatic CSF Leakage Most cases of CSF leakage are caused by HI and skull base fractures. To identify the source of CSF leakage, it is necessary to differentiate CSF leakage and nasal exudate. It is made by biochemical tests showing the level of glucose over 30 mg/l. It was shown on a large material that in two thirds of patients, CSF leakage was found within the first 48 h after in-
Head Trauma
Fig. 9.185a–f Dynamic posttraumatic hydrocephalus. a–c Acute phase, d–f 5 months after injury
911
912
Chapter 9
Fig. 9.186a–f Dynamic posttraumatic hydrocephalus, a Acute phase, b 25 days, c 1 month, d 40 days, e 3 months, and f 4 months after in-
jury
jury. In other cases, it developed later, and in several cases in the delayed period—months or years later. The longest period between HI and onset of CSF leakage was 25 years, according to the literature. Most fistulas are closed spontaneously after medical treatment (Gavrilov 2003). Spontaneous closure of fistula is observed in adhesive processes, displacement of brain tissue towards bone defect, and less frequently in cases with formatted granulation tissue after concomitant meningitis. Quality of spontaneous closure is often inadequate and as a result, meningitis or CSF leakage was developed (Ommaya 1996). Meningitis may be prompt and life threatening. The prevalence of meningitis caused by CSF leakage according to our data is 7.8%, it ranges from 16 to 21% according to other reports (Freedman 2001). Vigilance is required when CSF leakage develops after HI,
especially in skull base fractures, in fractures of frontal sinus, ethmoidal labyrinth cells, and temporal bone. Delayed CSF leakage may abruptly manifest by abundant CSF leakage or meningitis without obvious CSF leakage. Prevalence of skull base fractures is 46.1% and basal CSF leakage is 18.6% of 249 patients treated at the Burdenko Neurosurgery Institute. With progression of HI severity, the number of CSF leakage cases significantly increased. In 81.2% of cases, medical therapy led to spontaneous closure of fistulas irrespectively to severity of HI. Location of CSF fistulas in most cases coincides with sites of fractures diagnosed on CT and with location of bone splinters. According to the data of the Burdenko Neurosurgery Institute, CSF fistulas were marked in the frontal sinus in 43.6%, 6.4% in frontal sinus and anterior portions of the ethmoidal
Head Trauma
bone, 15.4% in the ethmoidal sinus, 7.1% in the posterior part of the ethmoidal and sphenoidal sinus, 10.9% in the sphenoidal sinus, and 16.7% in the temporal bone pyramid. Target craniography may help to diagnose the CSF leakage source, as it can show the level of fluid in the nasal sinuses, especially in the sphenoidal one. Pneumocephalus is one of the features that prove communication of the subarachnoid spaces and the external space. To determine type of lesion and its location, SCT with 3D reconstruction of the entire anterior cranial fossa is indicated, and in cases of ear liquorrhea after injury of the temporal bone pyramid, it is necessary to scan the whole skull base in this regimen (Figs. 9.187, 9.188). To visualise CSF fistula CT cisternography (CTCG) is used. After local anaesthesia, a lumbar puncture is done at the level of L3–L4 or L4–L5, CSF pressure is measured, and then a non-ionic contrast medium is introduced intrathecally (Omnipaque, Ultravist). The patient is positioned prone, with head end of the table lowered, and 20–30 min later, frontal CT is performed with thin slices and short gap. CTCG may demonstrate the precise location of the CSF leakage source and a fracture, and sometimes multiple fractures (Fig. 9.189). However, it should be noted that in 13.3% of nasal liquorrhea cases, CTCG fails to reveal the cause or location of bone defect when CSF leaks into the nasal cavity. MR cisternography (MRCG) with such pulse sequences as PSIF, SSFP, and CISS (in relation to the software manufacturers’ terms) is a noninvasive technique used in CSF leakage diagnosis after HI. The signal of CSF is hyperintense, whereas the signal of bones of the anterior cranial fossa base is hypodense, thus providing a highly diagnostic method. Frontal and sagittal projections are most informative. It should be noted that patients with CSF leakage should be examined in the prone position; this position provides reliable fistula visualisation. Despite modern noninvasive facilities of MRI in the
913
diagnosis of CSF fistulas, the per cent of cases in which they are visualised is even lower than in CTCG. When MRCG or CTCG fails to determine location of CSF fistula, then MRCG with injection of mixed contrast media— a non-ionic X-ray contrast medium and a paramagnetic such as Omnipaque and Omniscan or Ultravist and Magnevist or Gadovist was used at the Burdenko Neurosurgery Institute. Sensitivity and specificity of MRI in case of nasal liquorrhea diagnosis increased to 98% (Figs. 9.190, 9.191). Meningoencephalitis, ventriculitis, empyema, and brain abscess may also complicate traumatic basal liquorrhea along with meningitis. The most significant factor of their development is duration of liquorrhea over than 14 days.
9.3.7 Vascular Lesions of Head Injury 9.3.7.1
Delayed Intracerebral Haematomas
Delayed intracerebral haemorrhages are found in 7% of patients with severe HI, and usually they are revealed within the first week after injury, more frequently within the first 24–48 h. They may occur within the first 10 days in those patients who underwent urgent evacuation of acute intracerebral haematomas. One of possible causes is impairment of coagulation alongside with primary brain injury, which leads to consequent intracerebral bleeding and haemorrhagic infarctions. CT is a method of choice to diagnose delayed and recurrent intracerebral haematomas. Delayed intracerebral haematomas are most always lobar, and frequently multifocal, and may be found in those areas where contusion lesions have been seen earlier. Delayed recurrent intracerebral haematomas may also be revealed at the site that appeared to be normal on primary CT, which is why CT should be performed each 2–5 days in patients who show no improvement after HI.
Fig. 9.187a,b Posttraumatic nasal CSF leak, 2 days after injury, fracture of the posterior wall of the frontal sinus with penetration into the right ethmoid labyrinth. a Scanogram, b coronal CT
914
Chapter 9 Fig. 9.188a–f Posttraumatic nasal CSF leak, depressed fracture of the frontal–zygomatic–orbit complex, bilateral fracture of the frontal, ethmoidal, and nasal bones, and fracture of the facial skull bone. (a–g axial and coronal CT, h, i 3D reconstruction)
Head Trauma
915
Fig. 9.188g–i (continued) Posttraumatic nasal CSF leak, depressed fracture of the frontal–zygomatic–orbit complex, bilateral fracture of the frontal, ethmoidal, and nasal bones, and fracture of the facial skull bone. (a–g axial and coronal CT, h, i 3D reconstruction)
Fig. 9.189a–f Nasal CSF leak in skull base fracture. CTCG (different patients)
916
Chapter 9
Fig. 9.190a–f Nasal CSF leak after HI. Two fistulas in the ethmoid bone and sphenoid bone. CTCG (a–c) and FLAIR (d–f) MRI with use of
combined contrast substance
Fig. 9.191 CSF leak. MR CG using combined contrast substance in posttraumatic basal CSF leak
Head Trauma
917
Fig. 9.192a–c Severe HI. CT on the third day after injury (a) detects haemorrhagic contusion in the left frontotemporal area and subarach-
noid haemorrhage. CT in 2 weeks after injury (b) reveals enlarged perifocal oedema in the contusion area; MRI (c) shows delayed subacute subdural haematoma
9.3.7.2
Delayed Epidural and Subdural Haematomas
Delayed epi- and subdural haematomas are also found in approximately 7% of patients after severe HI, within the first 10 days, more frequently within the first 24–48 h (see Fig. 9.10). If a patient’s condition has not improved within the first 48 h and primary CT failed to reveal and mass lesions, then it should be repeated each 2–5 days as in patients with delayed intracerebral haematomas, even if a patient was admitted for small extracerebral haematomas. CT should be repeated 3–5 days later irrespective of the extent of clinical recovery. There are observations of patients who underwent urgent craniotomy with extracerebral haematoma evacuation, and later delayed contralateral haemorrhage developed within the following two weeks (Zee et al. 2002). CT and MRI features of delayed haemorrhages do not differ from that of acute ones. MRI is more sensitive in detection of subdural and paratentorial haematomas (Fig. 9.192).
Application of modern neuroimaging techniques in diagnosis of HI changed treatment tactics fundamentally. Past interpretation of craniograms was based on descriptive anatomy and was not compared with clinical course and outcomes of HI. Recent advances in neuroimaging based on correlations between physiological, functional, and anatomic images, open new horizons in understanding of HI biology and prognosis of clinical outcomes. New neuroimaging methods examine complex and ultrastructural neuropathophysiological events and then to map them anatomically. MRI may also reveal dot-like lesions in HI, to differentiate vasogenic and cytotoxic oedema, and demonstrate ischaemic foci with high precision and speed unlike any neuroimaging technique of the past. Modern MRI facilities lead to increased interest of mild HI, as it leads to changes that have never been paid attention before. Implementation of MRS, DWI, and PW MRI widened our understanding of HI pathogenesis.
Refere n c e s Aarabi B (1988) Traumatic aneurysms of the brain due to high-velocity missile head wounds. Neurosurgery 22:1056–1063 Adams RD, Fisher CM, Hakim S et al (1965) Symptomatic occult hydrocephalus with “normal” cerebrospinal fluid pressure. N Engl J Med 273:117–126 Arfanakis K et al (2002) Diffusion tensor MRI imaging in diffuse axonal injury. AJNR Am J Neuroradiol 23:794–802 Arutiunov N et al (2000) MRI Ventriculo-cisterno-myelography and phase contrast MRI with cardiac gating in investigating pathologies of CSF dynamics. 86th scientific assembly and annual meeting of the Radiological Society of North America, Chicago, pp 150–151
Babchin A, Kondakov E, Zotov I (1995) [Traumatic subdural hygromas.] Rossiiskii nauchno-issledovatel’skii neirokhirurgicheskii institut im. A.L. Polenova, St. Petersburg (In Russian) Besenski N, Broz R, Jadro-Santel D et al (1996) The course of the traumatizing force in acceleration head injury: CT evidence. Neuroradiology 38:36–41 Bradley W et al (1996) Normal pressure hydrocephalus: evaluation with CSF measurements at MRI imaging. Radiology 198:523–529 Castillo M (2002) Neuroradiology. Lippincott Williams & Wilkinson, New York, pp 257–271
918 Cooper P (1982) Head injury. Lippincott, Williams & Wilkinson, New York Evans S, Gean A (1999) Craniocerebral trauma. In: Stark D, Bradly W (eds) Magnetic resonance imaging, 3rd edn. Mosby, St. Louis, pp 1347–1360 Firsching R et al (2001) Classification of severe head injury based on magnetic resonance imaging. Acta Neurochir (Vienna) 143:263–271 Friedman J, Ebersold M, Quast L (2001) Post-traumatic cerebrospinal fluid leakage. World J Surg 25:1062–1066 Gaidar B (ed) (1998) Military neurosurgery. VIAVMA St. Petersburg, Russia Gavrilov A, Potapov A, Kravchuk A et al (2003) [Skull base fractures: clinical and prognostic aspects. In: Evidence-based neurotraumatology.] Antidor, Moscow, pp 62–97 (In Russian) Gean A (1994) Imaging of head trauma. Raven, New York Gentleman S et al (1995) Axonal injury: a universal consequence of fatal closed head injsury. Acta Neuropathol 89:537–543 Grossman R, Yousem D (1994) Neuroradiology. Mosby, St. Louis, pp 149–169 Husson B, Pariente D, Tammam S et al (1996) The value of MRI in the early diagnosis of growing skull fracture. Pediatr Radiol. 26:744–747 Ishii K et al (1996) MRI of brain death. Neurol Med Chir (Tokyo) 36:166–171 Jinson G et al (2001) MTI and proton MRS in the evaluation of axonal injury. AJNR Am J Neuroradiol 22:143–151 Kanamalla U, Ibarra R, Jinkins J (2000) Imaging of cranial meningitis and ventriculitis. Neuroimaging Clin N Am 10:309–331 Kim S, Chang K, Song I et al (1997) Brain abscess and brain tumor. Discrimination with in vivo 1H MR spectroscopy. Radiology 204:239–245 Konovalov A, Lihterman L, Potapov A (eds) (2002) Clinical manual on traumatic brain injury. Antidor, Moscow (in Russian) Kornienko V, Vasin V, Kuzmenko V (1987) Computed tomography in diagnostics of traumatic brain injury. Medicina, Moscow (in Russian) Kornienko V (1981) Angiographic study of the brain hemodynamic in neurosurgery patients with irreversible changes. In: Functional cerebral angiography. Medicine, Leningrad, pp 184–203 (in Russian) Kornienko V, Arutiunov N, Petryaikin A, Fadeeva L (2002) Flair and SE+MTC after intrathecal administration combined X-ray/MR contrast media of skull base CSF fistula—what sequence is better? 17th Neuroradiological symposium, Paris Kuzma B, Goodman J (2000) Improved identifications of axonal shear injuries with gradient echo MRI technique. Surg Neurol 53:400–402 Laine F, Shedden A, Dunn M et al (1995) Acquired intracranial herniations: MR imaging findings. AJR Am J Roentgenol 16:967–973
Chapter 9 Lebedev V, Krylov V (1998) [Remarks on the pathogenesis of brain contusions occurring by a counterimpact mechanism in the acute period of their development.] Zh Vopr Neirokhir Im N N Burdenko.1:22–26 (In Russian) Lee Ch, Go J (2002) Imaging of head trauma. Neuroimaging Clin N Am12:2 Lichterman L, Potapov A (1998) [Classification of head trauma.] In: Konovalov A, Lichterman L, Potapov AМ (eds) [Clinical handbook of head trauma.] Antidor, Moscow, pp 47–129 (In Russian) Mannion R et al (2007) Mechanism-based MRI classification of traumatic brainstem injury and its relationship to outcome. J Neurotrauma 24:128–135 Nakahara M, Ericson K, Bellander B (2001) Diffusion-weighed MRI and apparent diffusion coefficient in the evaluation of severe brain injury. Acta Radiol 42:365–9 Ommaya A (1996) Cerebrospinal fluid fistula and pneumocephalus. In Wilkins RH, Rengachary SS (eds) Neurosurgery. McGraw-Hill, New York, pp 2773–2782 Orrison W (2000) Neuroimaging and head trauma. Saunders, Philadelphia, pp 884–915 Osborn A (1991) Secondary effects of intracranial trauma. Neurosurg Clin N Am 1:461–474 Osborn A (2002) Vascular effects of trauma. In: Osborn A, Blasrer S, Salzman K (eds) Pocket radiologist. Saunders, Philadelphia, pp 25–27 Potapov A, Lihterman L, Zelman V et al (2003) Evident neurotraumatology. Medicine, Moscow (in Russian) Reich J et al (1993) MRI measurements and clinical changes accompanying transtentorial and foramen magnum brain herniation. Ann Neurol 33:159–170 Sinson G, Bagley L, Cecil K (2001) Magnetization transfer imaging and proton MRI spectroscopy in the evaluation of axonal injury: correlation with clinical outcome after traumatic brain injury. AJNR Am J Neuroradiol 22:143–51 Sze G, Lee S (1999) Infectious diseases. In: Cranial MRI and CT, 4th edn. McGraw-Hill, New York, pp 453–516 Uolker A (1998) Brain death. Medicine, Moscow (in Russian) Wilde E, Chu Z, Bigler E et al (2006) Diffusion tensor imaging in the corpus callosum in children after moderate to severe traumatic brain injury. J Neurotrauma 23:1412–1426 Wintermark M, Melle G, Schnyder P et al (2004) Admission perfusion CT: prognostic value in patients with severe head trauma. Radiology 232:211–220 Yasokawa Y et al (2007) Correlation between diffusion-tensor magnetic resonance imaging and motor-evoked potential in chronic severe diffuse axonal injury. J Neurotrauma 24:163–173 Young B (1996) Sequelae of head injury. In: Wilkins RH, Rengachary SS (eds) Neurosurgery. McGraw-Hill, New York, pp 2841 -2846 Zee C, Hovanessian A, Go J Kim PE (2002) Imaging of sequelae of head trauma. Neuroimaging Clin N Am 12325–338 Zimmerman R (1999) Craniocerebral trauma. In: Lee H, Rao K (eds) Cranial MRI and CT. McGraw-Hill, New York, pp 413–452
Chapter 10
10
Hydrocephalus
in collaboration with V. Ozerova and N. Aroutiunov
10.1 10.2 10.3 10.4 10.5
Physiology of the Cerebrospinal Fluid System . . . . . . . . . . . . . . Techniques for Neuroimaging of CSF Spaces and Quantitative Measurement of CSF Circulation . . . . . . . . . . . . . . Quantitative Techniques for Measurement of CSF Flow Velocity by PC MRI .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clinical Studies .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Complications .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
919 921 921 924 933
10.1 Physiology of the Cerebrospinal Fluid System The physiology of the CSF system includes CSF production, CSF circulation, and CSF resorption (Arendt 1948; Purin et al. 1978; Barkovich 2000). These three processes are dynamic parameters of the CSF system functioning, which may change with time. It is thought that the CSF motion in contrast to blood motion is not a circulation itself. CSF is produced by the choroid plexus of the cerebral ventricles and undergoes partial resorption intracranially; the rest of the CSF undergoes resorption in the spinal cord. The CSF produced intraventricularly flows from the lateral ventricles into the third ventricle via foramina of Monro, then via the aqueduct of Sylvius to the fourth ventricle, from there is goes into Magendie and Luschka foramina into the basal cerebral cisterns and subarachnoid spaces of the brain and the spinal cord. It was shown that CSF is also produced in the central channel of the spinal cord. The long dural sack is a reservoir for CSF, as there is no significant production of CSF in the spinal cord; however, a significant portion of CSF undergoes resorption there. CSF moves caudally from the cranial cavity. That is why in the spinal cord in rest, CSF moves caudally. During body movement, mild deviation of CSF motion occurs in the dural sack or it undergoes remixing. The milder is tension of the dural sack, the greater is CSF remixing.
CSF circulation is much more sophisticated intracranially. Until now, CSF circulation was considered a slow motion in a single direction from the ventricular system via CSF pathways into the subarachnoid spaces of the brain and the spinal cord and into the Pachioni granulations (the bulk-flow model) (Baron et al. 1976). CSF level equilibrium is mainly determined by CSF production and resorption. In the past, only the hydrostatic CSF pressure was estimated, which was measured via lumbar puncture and sensitive manometer in pathological conditions and during infusion tests. However, CT, MRI, and radiological cisternography data, as well as observations of neurosurgeons during surgical interventions, distinguished not only the slow, but also the rapid CSF circulation. Radiological studies by Di Chiro (1964, 1966) revealed the rapid tracing of the isotope from the lumbar space into the cranial cavity. Later, the existence of rapid flow of CSF were confirmed by the studies of isotope tracing after injection into the dural sack (Greitz 1993). During the endoscopic perforation of the third ventricle’s floor, surgeons many times registered rapid flows of blood clots with CSF. These facts allowed reconsidering the existing concept of CSF circulation in accordance with fluctuations of CSF pressure, depending on phases of the cardiac cycle (Greitz 1996). The first evidence acquired by phase-contrast MRI revolutionised the existing concepts of CSF circulation. It was shown that a pulsatile motion is typical for the extraventricular CSF flow (Enzmann and Peln 1991; Kupriyanova 2004). It causes rapid remixing of CSF in the subarachnoid space (SAS). In the extraventricular SAS, there was no resulting CSF flow detected, but the resulting CSF outflow was revealed in the aqueduct of Sylvius, which confirmed the generally adopted opinion that CSF is mainly produced in the choroid plexus of the cerebral ventricles. Greitz (1993) linked this pulsatile CSF motion with dilatation of intracranial arteries. The pulsation of blood causes CSF pulsation in the craniovertebral junction, and CSF motion in the aqueduct of Sylvius reflects the resilient dilatation of the cerebral tissue. The later studies of Greitz confirmed that the concept of continuous CSF flow to Pachioni granula-
920
tions should be reconsidered, and adsorption of CSF in the CNS occurs not only in Pachioni granulations, but also in capillaries (Greitz 1997). Bhadelia et al. (1997, 1998) revealed a correlation between the arterial and CSF pulsations, and it was shown that the character of CSF circulation is directly associated with the cardiac pulsation. If CSF outflow occurred only via Pachioni granulations into the venous system, then it should be expected that the venous as well as arterial flow influences somehow on CSF pulsations. However, such conformity has not been found. Authors explained this fact by predominance of the arterial influence on CSF flow and the variability of the venous flow. The venous pulsations influenced the amplitude of CSF pulsations under conditions of venous compression—the condition when the intracranial pressure rises. Under these conditions, the maximal systolic velocity of CSF flow was decreased extraventricularly, and a peak of CSF curve was delayed in time. It was shown that the character of CSF flow in the subarachnoid space is quite a constant parameter, and high reproducibility of CSF curve shapes was registered (Greitz and Hannerz 1994). CSF circulation in the cranial cavity is quite sophisticated. In the brain rich in blood vessels, changes in brain volume occur under the influence of blood pulsations. The venous system of the brain, with its large veins on the convex cerebral base surface and with sophisticated venous sinuses system, may change its volume significantly when the cerebral blood volume changes. When the blood flows to the head, a compensatory evacuation of CSF via the appropriate foramina occurs. Fluctuations of blood pressure, especially the venous ones, cause fluctuations of CSF pressure in the way of a wave. The wave of systolic pressure increase initiating in the cranial cavity goes to the lumbar portion of the spinal cord during the diastole, but these pulse waves do not lead to increase of CSF flow, only to remixing of CSF. Thus, the intracranial and intravertebral CSF flow has a sophisticated pulsatile character and is associated with cardiac pulsations. Depending on the phase of the cardiac cycle, CSF flow acquires different directions, i.e. CSF motion is biphasic. However, biphasic flow in the basal cistern, the aqueduct of Sylvius, and the spinal channel is not coherent due to delay caused by the motion of brain tissue. Thus, caudal motion of the cerebellar tonsils and brainstem that occurs right after the systole leads to systolic caudal flow of CSF, and in the cervical part, it occurs earlier than in the aqueduct of Sylvius. In the latter, systolic flow of CSF is more dependent on motions of the cerebral hemispheres. Complete admixture of flows and bidirectional flow of CSF may occur on different levels including cisterna magna, the prepontine, and the suprasellar cisterns. The most complete admixture occurs in the subarachnoid space of the spinal cord, especially in the cervical and the thoracic regions. In the convexally located subarachnoid space, CSF admixture is not significant due to mild CSF pulsations. The character of CSF flow is determined not only be the strong association between the brain motion and the blood flow, but also by the complex geometry of CSF space. Besides, much more complex interac-
Chapter 10
tions exist between the blood supply and pressure in the territories of venous circulation: the venous sinuses, the cerebral base veins, deep and convex veins, on the one hand, and facial, jugular veins, craniovertebral ring and the deep vertebral veins, on the other hand. Very complex is the relation between outflow and pressure inside the veins (hence, the intracranial pressure) and a patient’s position (horizontal, vertical, prone or supine), and presence of somatic pathology. Our numerous studies and experiments with account to other authors’ experience allowed elaborating the most complete model of CSF production, circulation, and resorption in the brain (Fig. 10.1). Thus, the intracranial and intravertebral CSF motion is associated with the cardiac cycle as well as with different conditions and positions of a patient’s body. The discussed anatomic and physiological characteristics of CSF system physiology makes it obvious that diagnostic features of pathological changes in CSF spaces may be static as well as dynamic. They may appear as impairments of intraand extracerebral regions symmetry, changes of relative size of the cerebral ventricles, cisterns, SAS, by absence of communication between them, as well as by impairments of secretion or resorption of CSF, changes of resilient (mechanical) properties of the brain parenchyma and, as result, as changes of CSF flow velocity in CSF channels.
Fig. 10.1a,b The modern concept of CSF circulation
Hydrocephalus
10.2 Techniques for Neuroimaging of CSF Spaces and Quantitative Measurement of CSF Circulation 10.2.1 CT and MR Myelography, Cisternography CT and MRI neuroimaging techniques of CSF spaces may be subdivided into static and dynamic, according to the assessed basic physiological parameters of CSF system, but first, among the diagnostic tools, invasive and noninvasive techniques are distinguished. Invasive techniques suggest the injection of contrast medium into CSF spaces of the brain and the spinal cord. One of the first invasive techniques of CSF system assessment was pneumography. When contrast media safe for intrathecal injection was created, specialists started to apply X-ray myelography and cisternography to reveal anatomic and physiological impairments of CSF system, and later when CT appeared, specialists started to apply CT myelography and cisternography. CTCG in the diagnosis of intracranial lesions including occlusions, fistulas, liquorrheas, injuries, cysts of different origin, and other disorders and lesions, localises and characterises the morphology of the pathological areas as well as to assess secondary effects caused by a tumour, for instance (Hachatrian et al. 1998). Contrast media is not used during noninvasive techniques, and imaging of CSF spaces occurs on CT, due to tissue contrast between the brain parenchyma and CSF. Implication of geometrical techniques to estimate CSF spaces volume was applied in CT. Initially, CSF spaces volume was calculated by encircling contours of the studied structure manually on each of the sequential CT scans and then 3D reconstruction techniques appeared. CT scans reconstruct geometry of CSF spaces and aid in calculating the ratio of the ventricle– brain volumes (VBR). Different indixes were applied (Evans index, etc.), and attempts were made to compare changes of the ventricular system volume with clinical signs of different disorders—brain atrophy, schizophrenia, Alzheimer’s disease, hydrocephalus of various origin—and, despite bias inherent in CT techniques, potential significant of the acquired findings was obvious.
921
High tissue contrast inherent in MRI made it a basic noninvasive technique for neuroimaging of CSF spaces (Parkkola et al. 2001) (Fig. 10.2). Myelography and cisternography techniques permit study of slow flows of CSF during relatively long time scans (dozens of minutes and hours), and they are related to static techniques. However, visual assessment of the dynamic parameters of CSF flow (velocity, acceleration) by CT, MR myelography and cisternography, as well as acquisition of quantitative parameters of CSF flow are impossible. An advantage of noninvasive CT and MR CG is the facility to perform 3D studies, which are used for quantitative assessment of CSF flow parameters, such as volumes of the ventricular system and the subarachnoid space, volume of the cranial vault and the brain parenchyma. The 3D fast asymmetric spin echo (FASE) technique assesses the intracranial and the intraventricular CSF volumes and aids in calculating the ratio of these volumes. Dilatation of the ventricles and high ratio of the intracranial and the intraventricular CSF volumes allows diagnosing normal pressure hydrocephalus (NTH) with high probability (Yoshihara et al. 1998). CT, MR myelography and cisternography techniques assess anatomic characteristics of CSF system, and visualise geometry of CSF spaces with slow CSF motion. Rapid CSF motion produces artefacts on images. Imaging of the rapid CSF flows depending on the flow direction and velocity became possible on phase-contrast MRI (PC MRI).
10.3 Quantitative Techniques for Measurement of CSF Flow Velocity by PC MRI PC MRI is a technique for imaging and quantitative assessment of CSF flow and blood flow velocity. To encode a flow velocity in the pulse sequence (PS), additional gradient pulses are used, due to which, an additional spin velocity–depending shift in phase occurs within the MR signal, reflecting the moving protons moving with the flow. Additional shift in phase is absent in stationary spins. The images acquired contain only
Fig. 10.2a,b MR cistern ventriculography
in the normal state (а), and in open hydrocephalus (b)
922
a data about the moving flow of spins; the signal of protons from the motionless tissues is absent. Protons moving in a single direction look bright on an image, whereas protons moving in the opposite direction look dark (Figs. 10.3, 10.4). Viewing images acquired in different phases of the cardiac cycle in “cine” regimen, CSF flow may be visualised, and the average flow per a cardiac cycle may be calculated as well as a momentarily values of the flow in separate phases of the cardiac cycle (Nitz et al. 1992). Other imaging techniques, such as TOF, for instance, give mainly morphological information and may characterise the proton motion velocity only indirectly. Diapason of the TOF techniques is limited by a Т1 value of blood and the value of the blood velocity in a vessel. Brightness of signal on phasecontrast images immediately corresponds to the spin motion velocity, i.е. PC techniques allow not only to assess CSF or blood flow visually, but also to obtain quantitative parameters of the flow velocity (Figs. 10.5, 10.6). During the registration, it is necessary to calibrate intensity of each pixel of an image according to the flow velocity. After that, changes of velocity may be observed in all phases of the cardiac cycle, and it is possible to acquire associations of quantitative characteristics of this flow: linear and volume velocities of spins with a flow. Theoretic considerations. PC MRI utilises a pulse sequence that is sensitive to changes in the phase of a measured
Chapter 10
signal. In such PS, an additional pair of gradients of the opposite polarity is used (bipolar gradients), each of them creates an additional shift in phase φ in the MR signal, depending on the proton motion velocity: φ = γАgТV, where γ is the gyromagnetic proton ratio, Аg is the square under the circumferential curve of each of bipolar gradient, Т is the time delay between the centres of two bipolar gradients, and V is a component of motion velocity in the direction of gradient field strength. A moving spins velocity weighted image is a result of subtraction of two sequentially registered images, whose parameters differ only in polarity of the additional gradients. When the second image is registered, polarities of the additional gradient pulses invert, and the resulting shifts in phase of a single proton on two sequential images will be identical in their value but opposite in a mathematical context. In the signals of stationary protons, shifts in phase for the time of action of the bipolar gradients will be identical, and amplitudes and phases of signals of such protons will be identical on both images. They will be mutually reduced on the subtraction image. The signals of protons moving with flow will differ in amplitude and phase, and will not be reduced. Initially, when PC MRI was applied at first, an image was constructed that was acquired without additional gradients in PS, and then the second image was constructed that was acquired when bipolar gradients were added, further, subtracFig. 10.3a,b Phase-contrast MRI with
cardiac synchronisation (axial plane) on the craniocervical level in normal state. а Craniocaudal CSF flow in the systole, CSF appears bright (the arrow points to the spinal subarachnoid space). b Caudocranial CSF flow in the diastole, CSF appears dark
Fig. 10.4a,b Phase-contrast MRI with
cardiac synchronisation (axial plane) at the level of the aqueduct of Sylvius in normal state. а Craniocaudal CSF flow via the aqueduct of Sylvius CSF appears bright (arrow). b Caudocranial CSF flow via the aqueduct of Sylvius, CSF appears dark
Hydrocephalus
tion of these images was performed in a pixel-to-pixel manner. Moreover, it was taken a priori that the signal intensity on a subtracted image depends only on the velocity of spins movement. Later, in order to accelerate the process, MRI techniques began to use inversion of additional gradients in PS of the first and the second image, and after that, subtraction was performed before the Fourier transformation procedure during the reconstruction. In this case, to assess the velocity of spin movement quantitatively, it is necessary to take into account the spatial and temporal characteristics of movement. Moreover, to acquire quantitative measurements, the fundamental nonlinear associations between the signal intensity of a subtracted image and the shift in phase produced by motion should be taken into account. Velocity is a vector parameter, and vector of spins velocity may be directed in any dimension S/I, A/P, or R/L of the scanner system of coordinates. To acquire an image that will characterise the direction of flow motion as a whole, separate components of a flow should be identified along each of three dimensions of the scanner system of coordinates, and then, taking them into account, a velocity weighted image is calculated within the given slice plane. In PC MRI, the value of encoding velocity (VENC) is a maximal value of velocity, which will be visualised without distortion—that is why it is also called a limit of artefact due to the aliasing velocity phenomenon. This parameter gives a
923
diapason of spin movement velocities visualised without distortion, to which acquired PC images are sensitive. Pulsations of a flow may influence the acquired estimate of the motion velocity. Firstly, the motion velocity will be different in each measurement, which leads to artefacts within the direction of speed encoding. Secondly, velocity changes with acceleration what may also cause additional shifts in phase and, hence, additional artefacts. To avoid type I artefacts, cardiac synchronising and rapid PS are used. To avoid type II artefacts, a phase added by an accelerated motion is taken into account. Usually 16–20 sequential images are acquired during a single cardiac cycle, and the corresponding magnitudes of velocity are represented as a curve of velocity during the time span taken by a cardiac cycle. To view images in the cine regimen, measurement may be synchronised with the peripheral pulse changes. In cardiac synchronising, the moment of velocity estimation is usually set to the certain phase of a cardiac cycle (i.е. systole and the subsequent moments are determined more reliably). Due to delay of pulse during the peripheral synchronisation, the systolic part of a signal of changing flow velocity may be shifted in time. Imaging of the intracranial vessels of small calibre require to use thin slices when scanning (3–5 mm), to avoid volume partial artefacts on border of a vessel and the brain parenchyma. The slice plane should be oriented possibly in a rectangle to the direction of a flow. InFig. 10.5a,b Phase-contrast MRI, Flow
Analysis software, a healthy volunteer. а F1 Site of interest (the aqueduct of Sylvius), where CSF flow velocity was measured. b Curve showing a correlation between the linear velocity and the phase of the cardiac cycle
Fig. 10.6a,b Phase-contrast MRI of a
healthy volunteer. a F1 the intradural space, B1 the spinal cord. The site where CSF flow velocity was measured is located between F1 and В1. b Flow Analysis software: curve showing a correlation between the maximal linear velocity and the phase of the cardiac cycle
924
Fig. 10.7 Т1-weighted image of the aqueduct of Sylvius (axial plane)
in normal state with high resolution
Fig. 10.8 The correlation of stroke volume and the square of transverse section of the aqueduct of Sylvius in the normal state
correct choice of the slice plane (if the angle between the slice plane and the axis of flow direction is not 90°) may lead to mistake in measurement of flow velocity due to overestimation of the square of the transverse section of a chosen object. To estimate the diameter of an object with more precision an image of its transverse section is constructed with high resolution (Fig. 10.7). Such an image improves visualisation of contours but elongates the time of examination. In standard studies, minimally achieved time echo is used (when compensation of motion effects is used also), and the repetition time of PS is about
Chapter 10
40–50 ms. The direction of speed encoding is chosen such as the sensitivity of registration to a flow throughout a slice is provided. A typical 3D phase-contrast study at the level of the aqueduct of Sylvius requires the following protocol parameters: matrix 256 × 160, FOV = 20, VENC = 10–20 m/s, flip angle = 20°, TR = 26, TE = 11, slice thickness = 3 mm, and duration of examination should be a bit over than 7 min. Several minutes are also required for the image reconstruction, and slices for flows in the А/Р, S/I, and R/L directions may be obtained, respectively—60 amplitude images, and 20 new phase projection images, for 80 images for a whole study. Rapid CSF flows in CSF pathways were revealed and visual and quantitative estimates of CSF flow velocity were determined with the help of PC MRI. Perfection of PC MRI technique, implementation of the cine regimen, and cardiac synchronising opened new doors in the study of dynamic parameters of CSF circulation. To estimate function of CSF system in normal state and in different pathological conditions the following CSF circulation parameters are measured. • Amplitude parameters –– Linear velocity: v cm/s –– MSV: maximal systolic velocity –– MDV: maximal diastolic velocity –– Volume velocity: V = v × S ml/s (S is square of CSF pathway transverse section) • Temporal parameters –– R-MSV: a time span up to the point with MSV value –– R-MDV: a time span up to the point with MDV value –– R-S: a time span up to the origin of the craniocaudal flow –– R-D: a time span up to the origin of the caudocranial flow • Energetic parameters –– Stroke volume: the volume flow of CSF, passing through the section of CSF pathway during a cardiac cycle or per minute (millilitres per second and millilitres per minute) Our studies of CSF circulation in normal state showed that there is a strong correlation (r > 0.88) of stroke volume in the aqueduct of Sylvius and the square of its transverse section. The acquired correlation may help enormously in the approximate estimation of stroke volume without PC MRI, using only statistical methods of visualisation of CSF system, such as PSIF and FIESTA (Fig. 10.8).
10.4 Clinical Studies Hydrocephalus is an excessive accumulation of CSF in the cerebral CSF spaces due to imbalance of its production and resorption. In the normal state, the balance between production and resorption of CSF is a constant value. Hyperproduction of CSF is seen only in secondary hydrocephalus in patients with papillomas of the choroid plexus. In the rest of cases, hydrocephalus is usually a result of impaired resorption of CSF, or may ensue due to blockage of CSF pathways. On the one
Hydrocephalus
hand, decrease of resorption may be a result of blockage of arachnoid pili or lymphatic canal of cranial and spinal nerves and adventitia of cerebral vessels. Increase of the intracranial pressure leads to development of compensatory resorption pathways of CSF: through arachnoid membranes, stroma of the choroid plexus, and the extracellular spaces of the cerebral tissue (the transependymal pathway). The causes of hydrocephalus may influence a developing brain in the intrauterine period (congenital hydrocephalus) as well as after birth (acquired hydrocephalus). Factors mediating hydrocephalus are cerebral malformations (up to 30%), stenosis and gliosis of the aqueduct of Sylvius, congenital vascular malformations, pathology of arachnoid pili and granulations, brain tumours and nontumoral mass lesions, craniocerebral injury, haemorrhages, ischaemia, acute and chronic inflammatory disorders, and chronic intoxication (Maytal et al. 1987; Flodmark 1992). Open or communicating (internal, external, mixed) hydrocephalus is distinguished. Such term as hydromyelia is used when the central spinal canal is dilated. Clinical picture depends on the patient’s age and the type of hydrocephalus. Main symptoms of hydrocephalus in children younger than 2 years are progressive increase of head circumference, stain and out-pouching of the major fonticulus, thinning of cranial vault bones, diversion of suture margins, and dilatation of subcutaneous head veins. Frequently, cranial neuropathies are seen: upward gaze palsy, abducens nerve palsy, impairment of pupil photoreaction, and lower spastic paraparesis due to involvement of the corticospinal tract. In older children and adults, the signs of hydrocephalus reflect rise of intracranial pressure (headaches with nausea and vomiting, papilloedema) and pyramidal signs. Diagnosis of hydrocephalus is mainly based on X-ray and CT examinations, taking into account the clinical picture.
10.4.1 Open (Communicating) Hydrocephalus In open hydrocephalus, communication between the ventricular system and the subarachnoid space is preserved. If the
925
cerebral subarachnoid space is completely or partially absent (as after inflammatory process in meninges), then resorption of CSF is impaired, and it accumulates in the ventricular system, i.e. open internal hydrocephalus develops. In other cases, the cerebral subarachnoid space is preserved, dilated, and CSF accumulates predominantly there, i.e. open external hydrocephalus develops. On X-ray craniograms in young children, increase of skull size is seen, and its shape acquire hydrocephalic features: frontal tubers protrude, and the vault bows transit to each other creating a spherical surface. In rapid progression, the major fonticulus becomes strained, and sutures are pulled aside and yawn. The sella turcica is usually preserved, only in longstanding hydrocephalus does it depresses together with other cranial bones and turns towards the anteroposterior direction. In older children and adults, changes in cranial bones are far less prominent. Smoothening of the vault bows and prominent “fingerprints” point out the internal hydrocephalus. CT and MRI signs of an open hydrocephalus is a dilatation of all sections of the ventricular system—the fourth ventricle, the aqueduct of Sylvius, the third ventricle, and the lateral ventricles (Fig. 10.9). The connection between the fourth ventricle and cisterna magna is clearly seen. The latter may have normal or markedly increased size. The bottom of the third ventricle (especially its anterior portions) is depressed and is seen from the level of sella diaphragm or even in its cavity. The lateral ventricles are dilated to such extent that their walls are adjacent to the internal bone lamina of the vault, which is more frequently seen in younger children (Fig. 10.10). In rapid progression, a hypodensive area near the anterior horns of the lateral ventricles is seen; on MRI, it is a hyperintense area (better seen on T2-weighted imaging, proton density, and FLAIR images). The cerebral cisterns and the interpeduncular cistern are clearly seen on the appropriate slices. In younger children, they are usually increased in size, and the brainstem is as if “floating” in the large amount of CSF. The ambient cistern in rapidly progressive hydrocephalus is narrowed, and in slowly progressive hydrocephalus, it remains intact. Subarachnoid spaces of the convex brain surface are not seen in rapidly pro-
Fig. 10.9a,b Open internal progressive
hydrocephalus. CТ (a,b): cisterns of the posterior fossa are free, and cisterns magna communicates with the wide fourth ventricle. The ambient cistern is narrowed. The aqueduct of Sylvius, and the third and the lateral ventricles are dilated, their borders are uneven, and the subarachnoid fissures are not visible
926
Chapter 10 Fig 10.10a,b Open internal progressive hy-
drocephalus. CT (а,b). Cisterns of the posterior fossa are wide and communicate with the fourth ventricle. Brainstem volume is reduced, it as if “floats” in the large amount of CSF. The lateral ventricles are dilated, their anterior portions are asymmetrical, D > S, the posterior are also asymmetrical, S > D (cross-dilatation). External walls of the lateral ventricles reach the cranial bones. The skull shape is irregual
gressing hydrocephalus or appear extremely narrowed. Frequently, dilatation of the lateral ventricles or any their part may be asymmetrical. The typical features of external hydrocephalus on CT and MRI are a dilatation of the cerebral subarachnoid space and a relatively mild dilatation of the ventricular system (Fig. 10.11). CTVG reveals a passage of contrast medium from the punctuated lateral ventricle into the contralateral ventricle, the third and the fourth ventricles, cisterna magna, and the spinal subarachnoid space. Under conditions of retarded resorption of CSF, the contrast medium retains (sometimes up to 48 h and over) for a long time in the ventricular system and the subarachnoid space of brain and spinal cord (Fig. 10.12).
On CTCG, the contrast medium injected intrathecally freely passes into the ventricular system and the cerebral subarachnoid space and remains there for a long time if CSF resorption is impaired—aresorptive hydrocephalus (Fig. 10.13). MRI cisternography sensitive to CSF flow (pulsatile artefacts) reveals the free passage of CSF from the third into the fourth ventricle and then via foramen Magendie into cisterna magna and the subarachnoid space of the spinal cord—low signal from CSF flow (Fig. 10.14). PC MRI with cardiac synchronisation allows obtaining an image of CSF motion in different phases of the cardiac cycle (usually 9–16 phases, depending on heart rate). In open hydrocephalus, CSF flow is clearly seen via the aqueduct of Sylvius: during systole, the signal of CSF in the aqueduct of Sylvius is high, and during di-
Fig 10.11a–c Open external hydrocephalus. CТ (а–b). The basal brain cisterns are wide, as well as the interhemispheric and the subarachnoid fissure of the convex brain surface. The ventricular system is mildly dilated
Hydrocephalus
Fig 10.12a–f Open internal progressive hydrocephalus. CTVG (а–c) 30 min after Omnipaque infusion in the right cerebral ventricle: the contrast fills the ventricular system, the dilated cisterns of the posterior fossa, the subarachnoid fissure of the convex brain surface, the interhemispheric and the lateral cerebral fissures are free of contrast
927
medium. CT (d–f) 6 h later: the evenly enhanced are the ventricular system, the basal cisterns, the interhemispheric and the lateral cerebral fissures, and the (partial) subarachnoid fissure of the convex brain surface. g–i see next page
928
Chapter 10
Fig 10.12g–i (continued) Open internal progressive hydrocephalus. CT (g–i) 24 h later: the contrast capacity of the ventricular system, the
basal cisterns, and the subarachnoid fissure of the convex brain surface decreased
Fig 10.13a–d Open internal subcompensated hydrocephalus. CTCG (а,b) 30 min after
injection of Omnipaque: the basal cisterns, and the third and the lateral ventricles are filled with contrast medium. CT (c,d) 24 h later: the ventricular system and the subarachnoid spaces remain weakly contrasted
Hydrocephalus
929
Fig 10.14a–c Open internal hydrocephalus. T2-weighted imaging (а), T1-weighted imaging (b), and MRCG (c): the lateral ventricles are
dilated, symmetrical, the signal of the third ventricle, the aqueduct of Sylvius, and the region of Magendie foramen are low due to CSF flow
Fig 10.15a–c Posttraumatic hydrocephalus. Axial PC MRI images
via the aqueduct of Sylvius in the systole (а) and diastole (b). During systole, the signal of CSF flow in the aqueduct of Sylvius is high,
astole, it is low (Fig. 10.15). In open hydrocephalus, the linear and volume CSF flow exceed normal values many times. PC MRI may detect a decrease of CSF flow through the aqueduct of Sylvius after the shunting operation for open hydrocephalus (Aroutiunov et al. 2000).
10.4.2 Obstructive Hydrocephalus Obstructive hydrocephalus occurs after the intraventricular obstruction of CSF pathways at the level of interventricular foramina, the third ventricle, the aqueduct of Sylvius, and the fourth ventricle (Cinalli et al. 1998). On X-ray craniograms, changes in cranial bones are much more prominent than in cases of open hydrocephalus. It is manifested by rapid enlargement of cranial size, thinning of
and it is low in diastole; the curve (c) shows a decrease of CSF flow velocity in the aqueduct of Sylvius on the third day after shunting operation
cranial vault bones, enhancement of the internal bone lamina relief, by pulling suture margins aside, and by depression of cranial base fossae. In infants, the major fonticulus evaginates and sutures yawn and are pulled aside. In older children and adults, X-ray craniograms reveal that suture margins are pulled aside. In slow progression of occlusion dents of sutures elongate, acquire large amplitude and after that, only sutures are pulled aside. In rapid progression, dents of sutures remain short, sutures are pulled aside, and the distance between them exceeds the length of dents that is why sutures appear torn. Size, shape, and structure of sella turcica fragments change due to immediate compression by the third ventricle as well as with the raise of intracranial pressure. A time of existence of hydrocephalus and the site of obstruction may be hypothesised according to the changes of cranial vault and base bones.
930
Chapter 10
Fig 10.16a–c Obstructive hydrocephalus (the level of the aqueduct of Sylvius). CТ: the third and the lateral ventricles are markedly dilated and the size of the fourth ventricle is unchanged. Marked periventricular oedema, the pontine cisterns are narrowed as well
as the ambient cistern, the subarachnoid fissure of the convex brain surface, and the interhemispheric and the lateral cerebral fissures are not visible
On CT and MRI, dilatation of the ventricular system is revealed superior to the site of occlusion. The most frequent site of occlusion is the aqueduct of Sylvius (Fig. 10.16). The third and the lateral ventricles are enlarged, the fourth ventricle remains unchanged, and the aqueduct of Sylvius is markedly narrowed or its lumen is invisible, which is better demonstrated on sagittal MRI (Fig. 10.17). Virtual endoscopy visualises changes of the aqueduct of Sylvius as if on an intraoperative picture (Figs. 10.18, 10.19). Occlusion of the outlet apertures of the fourth ventricle is characterised by a prominent dilatation of all sections of the ventricular system. The fourth ventricle appears round on axial slices, and on sagittal MRI, it loses its usual triangular shape. In addition, MRI reveals marked turbulent CSF motion
in the closed cavities of the third and the fourth ventricles (Figs. 10.20, 10.21). Occlusion of the interventricular foramina of inflammatory origin is very rare. The most frequent causes are tumours of the chiasmal sellar region, growing into the third ventricle or the third ventricle cysts, tumours of septum pellucidum, basal ganglia, and thalami. These mass lesions may lead to occlusion of one or both interventricular foramina and, hence, to symmetrical or asymmetrical hydrocephalus (Fig. 10.22). Changes more prominent in obstructive hydrocephalus are seen in the basal cerebral cisterns and the subarachnoid spaces of convex cerebral surface. The cisterna magna is small on MRI or may be even invisible on CT, and the pontine cis-
Fig 10.17a–c Obstructive hydrocephalus (at the level of the aqueduct of Sylvius). T1-weighted imaging (a) and MRCG (b,c): the fourth ventricles are of usual size, the third and the lateral ventricles
are dilated, and the septum in the aqueduct of Sylvius is seen. MRCG shows heterogeneity of signal from the third and the lateral ventricles cavities due to turbulent CSF flow
Hydrocephalus
931
Fig 10.18a–c Obstructive hydrocephalus after the aqueduct of Sylvius stenosis. MRCG: а (usual, magnified) images, b virtual endoscopy—
view from the third ventricle into the aqueduct of Sylvius
Fig 10.19a–c Obstructive hydrocephalus. The cyst of the pineal region. Adhesion at the level of the superior cerebral velum. MRCG: а (usual)
and b (magnified) images, c virtual endoscopy—the view from inside of the aqueduct onto the region of occlusion
Fig 10.20a–c Obstructive hydrocephalus (at the level of Magendie foramen). CT. The ventricular system is markedly enlarged, and the pontine cisterns are narrowed. The interhemispheric and the lateral cerebral fissures, and the subarachnoid fissure of the convex brain surface are not differentiated
932
Chapter 10
Fig 10.21a–c Occlusion of Magendie foramen. T1-weighted imaging (а) and T2-weighted imaging (b): the fourth ventricle is enlarged, and
has an incorrect triangular shape, and the third and the lateral ventricles are enlarged. c MRCG: marked turbulent CSF flow in the third and the fourth ventricles, and the aqueduct of Sylvius
Fig. 10.22a–c The colloid cyst of the third ventricle. а CT (a series of slices): a hyperdense mass lesion within the foramen of Monro. The lateral ventricles are asymmetrically enlarged. b T2-weighted imaging: the mass lesion in the foramen of Monroe is isointense to the
cerebral gray matter, periventricular oedema near the anterior horns of the lateral ventricles is mild. c Sagittal MRI on T1-weighted imaging: the mass lesion is hyperintense
Hydrocephalus
terns are narrowed, which is caused by enlargement of the supratentorial and shrinkage of the infratentorial spaces. The ambient cistern in all cases of obstructive hydrocephalus is markedly narrowed. The interhemispheric, the lateral fissures, and the subarachnoid space of the convex cerebral surface are markedly decreased in size due to enlargement of the ventricular system volume and brain oedema. Periventricular oedema is present in all cases of obstructive hydrocephalus; however, its extent may vary. If the origin of hydrocephalus is hard to diagnose, then CTVG may help. Contrast medium injected into the cavity of the lateral ventricle does not pass beyond the limits of occlusion and remains for a long time superior to the site of occlusion (Fig. 10.23). MR myelography and cisternography (MRMG and MRCG, respectively) acquire images of CSF spaces in comparison with the brain parenchyma in a relatively short time of examination. In obstructive hydrocephalus, MRCG may ascertain the site of occlusion of CSF pathways.
10.4.3 Changes of the Brain and CSF System after Shunting Operations Regression of obstructive as well as of open progressive hydrocephalus is accompanied with disappearance or decrease of CSF hypertension. Clinical picture improves in a way of disappearance of headaches, nausea and vomiting, and papilloedema inverts. In infants, strain and out-pouching of the major fonticulus dwindles, and its pulsation appears, and psychomotor development improves. Thickening of cranial vault bones tubular layer, disappearance or regression of fingerprints are seen and the relief of cranial vault bones becomes monotonous, sutures return to their normal state, and the shape and structure of sella turcica fragments are restored. In case of rapid CSF outflow, the region of major fonticulus and the skull acquires a peculiar form, with saddle-shaped and ladder-like deformity of this region. The correctly positioned tips of drainage system are seen in the projection of lateral ventricles. CT and MRI reveal the precise location of the ventricular tip of a catheter relatively to the ventricular system. Its free position in the lateral ventricle cavity is considered ideal, as that mediates an unhampered CSF outflow. Regression of hydrocephalus is manifested on CT and MRI by several signs, which may separately or in whole point out the extent of functional capacity of a drainage system (Assaf et al. 2006; Cinalli et al. 2006; Palm et al. 2006; Drake et al. 2007). The follow-up observation in the postoperative period should be considered positive if the ventricular system volume dwindles, the extent of periventricular oedema decreases or oedema disappears at all, if the thickness of cerebral tissue increases and the sizes of basal cisterns, and the subarachnoid space of the convex brain surface normalises in obstructive (Fig. 10.24) as well as in open hydrocephalus (Fig. 10.25). The most demonstrative are the changes in the ambient cisterns.
933
After surgery, its size increases in nearly 100% of cases, as CSF blockage disappears on the tentorial level. Restoration of the cerebral tissue after shunting operations is a criterion for successful treatment of hydrocephalus. The cerebral tissue becomes thicker within several weeks, due to mechanical contraction, thickening of earlier elongated axons, remyelination, and glial proliferation. The combination of these signs along with reduction of the white matter oedema leads to improvement of the remaining neurons function. If a shunting system is correctly chosen, reduction of size of the ventricular system is proportional in all segments irrespective to the type of hydrocephalus and the type of operation except ventriculocisternostomy. In cases when some premorbid ventricular disproportion was present (asymmetrical hydrocephalus, fronto-occipital disproportion), it usually preserves, but to the less extent (see Fig. 10.25). In obstructive hydrocephalus, MRCG is sensitive to CSF flow before and after surgery and may allow judgment about the success of ventriculostomy of the bottom of the third ventricle via the created aperture (Fig. 10.26). MRCG is the most reliable technique in the assessment of the third ventricle ventriculostoma functioning. CSF circulation in the surgically created fistula is detected by the “loss” of signal within the bottom of the third ventricle and basal cerebral cisterns (the chiasmal and the interpeduncular). PC MRI gives an important information about the pulsatile CSF flow via the decompressed aqueduct of Sylvius (after a tumour excision which compresses its lumen) or via the newly formed pathway in the bottom of the third in obstructive hydrocephalus (Konovalov et al. 2007) (Fig. 10.27). Impairment of a shunting system functioning in obstructive or open hydrocephalus is manifested by the same features as before operation or by their increase. They are changes of ventricles, subarachnoid spaces on different levels and periventricular oedema. All these signs serve as criteria for unsuccessfulness of the performed surgery and require revision of a shunting system (Fig. 10.28).
10.5 Complications We discuss only those complications that occur due to implantation of shunting systems and are detected by neuroimaging. They may be subdivided onto two groups, extra- and intracranial. According to timing of occurrence, they are subdivided onto the early, occurring within the first 10 days after surgery, and the late, occurring later. Among the intracranial complications, the most dangerous are haemorrhages: intraventricular, intracerebral, and subdural, which makeup 17% (Figs. 10.29, 10.30). Subdural haemorrhages often cause no progression of neurological deficits and are found in the late postoperation period, sometimes on a stage of calcification (Fig. 10.31). Calcified subdural haemorrhages may be found on X-ray craniograms: they appear as islands or chains of calcifications of various intensities near the cranial vault bones. If calcifications are absent, then indirect signs of subdural haemorrhages
934
Fig. 10.23a–i Obstructive hydrocephalus (the level of the aqueduct
of Sylvius). CTVG (а–c) 30 min after injection of Omnipaque into the right lateral ventricle: the third and the lateral ventricles are evenly filled, and the ambient cistern and cisterns of the posterior fossa are not enhanced. The lateral ventricles contours are weakly differentiated. CT (d–f) 6 h later: the fourth ventricle, the pontine cisterns, and
Chapter 10
the ambient cistern are lacking a contrast medium, which remains in the third and the lateral ventricles. CT (g–i) 24 h later: the density of the third and the lateral ventricles decreased, their contours are clear-cut. A ribbon-like strand in the anterior portion of the right lateral ventricle is seen
Hydrocephalus
Fig 10.24a–h Obstructive hydrocephalus (the level of the aqueduct
of Sylvius). CT (а–d) before surgery: the fourth ventricle has usual size, and the third and the lateral ventricles are enlarged. The pontine cistern and the ambient cistern are markedly narrowed. The interhemispheric and the lateral cerebral fissures, and the subarachnoid fissure of the convex brain surface are not visible. Marked periventricular oedema, more prominent near the anterior and the poste-
935
rior horns of the lateral ventricles is seen. CT (e–h) 7 days after a shunting operation. The third and the lateral ventricles are mildly decreased in size. The transverse cistern is wide. Periventricular oedema disappeared. The interhemispheric and the lateral cerebral fissures became visible, as well as the subarachnoid fissure of the convex brain surface. A drainage tube within the left lateral ventricle cavity is seen
936
Chapter 10 Fig 10.25a–f Open progressive
hydrocephalus. CТ (а–c) before the operation: cisterns of the posterior fossa are free, cisterna ambient is narrowed, the third and the lateral ventricles are enlarged, periventricular oedema is evident, the interhemispheric and the lateral cerebral fissures, and the subarachnoid fissure of the convex brain surface are narrowed. CТ (d–f) 2 years after ventriculoatriostomy: the ventricular system reduced markedly, cisterns of the posterior fossa have the same size as before operation, the ambient cistern, the interhemispheric and the lateral cerebral fissures, and the subarachnoid fissure of the convex brain surface increased in size
Hydrocephalus
937
Fig. 10.26a,b Occlusion of the aqueduct of Sylvius. MRCG before (а) and after (b) the third ventriculostomy: comparative assessment of
MRI a large area of signal loss is seen in the anterior portion of the third ventricle, and its bottom and farther in basal cisterns due to rapid CSF flow via the created fistula
Fig 10.27 Obstructive hydrocephalus (the level of the aque-
duct of Sylvius). PC MRI. Postoperative period: in the sagittal plane in the systole a hyperintense signal of CSF flow via the newly formed fistula in the bottom of the third ventricle into the basal cisterns. CSF flow via the aqueduct of Sylvius is not visible
938
Chapter 10 Fig 10.28a–f Obstructive
hydrocephalus (the level of the aqueduct of Sylvius). CT (а–d) before the operation: the fourth ventricle is unchanged, cisterns of the posterior fossa and the ambient cistern are narrowed, the third and the lateral ventricles are enlarged, and periventricular oedema is mild. The interhemispheric and the lateral cerebral fissures and the subarachnoid fissure of the convex brain surface are almost invisible. CТ (e–h) 10 days after ventriculostomy: the fourth ventricles have the same size and they are correctly positioned, and the third and the lateral ventricles decreased in size; the basal cisterns are clearly seen, the subarachnoid fissure of the convex brain surface, the interhemispheric and the lateral cerebral fissures, a drainage tube in the cavity of the right lateral ventricle are seen. g–l see next page
Hydrocephalus
939 Fig 10.28g–l (continued) CT
(i–l) 8 months after surgery (the condition worsened, headaches appeared, vomiting began): the posterior fossa structures are not conspicuous compared with the previous data, the ventricular system again increased in size, periventricular oedema appeared, and the subarachnoid spaces are not visible; and a drainage tube in the cavity of the lateral ventricle, its tip reached the interhemispheric fissure— impaired functioning of a shunt
940
Chapter 10 Fig 10.29a,b Obstructive hydrocephalus.
CT a day after ventriculoatriostomy (а,b). There is much blood in the posterior portions of the lateral ventricles. A drainage tube enters the left lateral ventricle from the side of the right one
Fig 10.30 Occlusion of the aqueduct of
Sylvius. CТ after ventriculoperitoneostomy: accumulation of CSF above the cerebral hemispheres bilaterally—bilateral pseudohygromas. There is small amount of blood in the posterior horns of the lateral ventricles, D > S
Fig 10.31a–c B-layer subdural haemorrhage rightwards after ven-
triculoatriostomy for obstructive hydrocephalus due to occlusion of the aqueduct of Sylvius (head trauma 6 days before admission). CТ
(a) after the operation: the ventricular tip of a catheter is near median line. One year later on CT (b): bilateral subdural haemorrhages (S > D). 3 years ago on CТ (c): calcification subdural hematomas
Hydrocephalus
941 Fig. 10.32a,b Two years after ventriculoatriostomy for obstructive hydrocephalus. X-ray craniograms in the lateral (a) and the frontal (b) projections. Calcified subdural haemorrhages bilaterally, a drainage tube is flexed downwards
may be detected on X-ray craniograms: a bow-shaped dislocation of a drainage tube (Fig. 10.32). Pseudohygromas occurring after shunting operations are the consequence of CSF hyperdrainage. They are frequently asymptomatic and are detected on control CT/MRI. Porencephalic fistulas (Fig. 10.33) within the sites of drainage tubes may be regarded as a consequence of an old haemorrhage occurred during a shunt passage into the ventricular cavity. They usually do not change the patient’s state, but if they increase in size up to a size of cystic cavity in the occipital lobes that may cause impairment of the fields of vision. Inadequate placement of the ventricular tip of a catheter is usually revealed in the late postoperative period on follow-up examinations. It may be located deeply in the inferior horn of the lateral ventricle, in the contralateral ventricle to that where it has been initially placed, or in the brain parenchyma. Inadequate placement of the ventricular tip of a catheter may cause its occlusion by ependyma or cerebral matter particles, blood clots, or by the choroid plexus and may lead to impairment of CSF outflow. Formation of membranes and strands in the ventricular cavities are usually the consequence of inflammatory process occurred before as well as after operations and they are clearly seen on CT and MRI. Separating the ventricles into separate cavities, these membranes may not only hamper CSF outflow
but also may cause occlusion of the ventricular tip of a catheter (see Fig. 10.23, Fig. 10.34). Lacing of the fourth ventricle (Fig. 10.35) is rarely seen in the late postoperative period and is a result of occlusion of outlets, stenosis of the aqueduct of Sylvius (formation of membranes within its cavity), as a result of inflammatory process or haemorrhage. Probably, it is more correct to regard lacing of the fourth ventricle to the previous group of complications as in the former and in the latter cases, the cause of ventricular separation into distinct chambers is an inflammatory process leading to formation of membranes and strands. Inverted cortex is rarely found in the postoperative period, predominantly in young children with prominent hydrocephalus, which is a result of rapid dwindling of the ventricular volume, and abrupt decrease of the intraventricular pressure combined with weakness of the cerebral tissue. Among extracranial complications, the most frequent ones are incorrect placement of the cardiac tip of a catheter, formation of additional loops and twisting, eruption of a part of a catheter and its displacement with blood flow, and calcification of the cardiac tip of a catheter. The most frequent cause of impairment of a shunt functioning in children in infancy is the exit of a shunt from the heart chamber due to insufficient length relative to the child’s height.
Fig. 10.33a,b Four years after ventriculoatriostomy for obstructive hydrocephalus. CТ: the lateral ventricles are moderately enlarged, S > D, and a drainage tube in the right lateral ventricle, and a porencephalic cavity along the drainage tube near the posterior portion of the right lateral ventricle (а,b) are seen
942
Chapter 10
Fig. 10.34a–c Open progressive hydrocephalus. Т2-weighted imaging (а) and Т1-weighted imaging (b,c): marked dilatation of all sections of the ventricular system, the fourth ventricle widely communicates with cisterna magna, the aqueduct of Sylvius is free, and membranes in the left lateral ventricle are seen Fig. 10.35a,b The isolated fourth ventricle in a 2-year-old child. Т1-weighted imaging (а) and MRCG (b): the fourth ventricle is markedly enlarged, the aqueduct of Sylvius is occluded, and the outlet from the fourth ventricle is not visible
Hydrocephalus
943
Refere n c e s Arend AА (1948) Hydrocephalus and it surgical treatment. Medicine, Moscow, p 200 (in Russian) Aroutiunov NV, Petriakin AV, Kornienko VN (2000) Assessment of CSF flow by magnetic resonance imaging. Vopr Neurosurg 3:29– 33 ( in Russian) Assaf Y et al (2006) Diffusion tensor imaging in hydrocephalus: initial experience. AJNR Am J Neuroradiol 27:1717–1724 Barkovich A (2000) Pediatric neuroimaging, 3rd edn. Lippincott Williams & Wilkins, Philadelphia, pp 581–620 Baron MA Maiorova TF, Dobrovolskiy GF (1976) CSF canals of pia matter of the brain. Arch Anat Histol Embryol 7:10–25 (in Russian) Bhadelia R, Bogdan A, Kaplan R, Wolpert S (1997). Cerebrospinal fluid pulsation amplitude and its quantitative relationship to cerebral blood flow pulsations: a phase-contrast MR flow imaging study. Neuroradiology 39:258–264 Bhadelia R, Bogdan A, Wolpert S (1998) Cerebrospinal fluid flow waveforms: effect of altered cranial venous outflow: a phase-contrast MR flow imaging study. Neuroradiology 40:283–292 Cinalli G, Sainte-Rose C, Kollar E et al (1998) Hydrocephalus and craniosynostosis. J Neurosurg 88:209–124 Cinalli G et al (2006) Intracranial pressure monitoring and lumbar puncture after endoscopic third ventriculostomy in children. Neurosurgery 58:126–136 Di Chiro G (1966) Observations on the circulation of the cerebrospinal fluid. Acta Radiol 5:988–1002 Drake J et al (2007) Endoscopic third ventriculostomy in pediatric patients: the Canadian experience. Neurosurgery 60:881–886 Enzmann D, Pelc N (1993) Cerebrospinal fluid flow measured by phase-contrast cine MR. AJNR Am J Neuroradiol 14:1301–1310 Flodmark O (1992) Hydrocephalus. In: Harwood-Nash DC, Petterson H (eds) Paediatric radiology. Mosby Intl., London, pp 63–77 Greitz D (1993) Cerebrospinal fluid circulation and associated intracranial dynamics: A radiologic investigation using MR imaging and radionuclide cisternography. Acta Radiol 386(Suppl):1–23 Greitz D, Greitz T, Hindmarsh T (1997) A new view on CSF circulation with the potential for pharmacological treatment of childhood hydrocephalus. Acta Pediatr 86:125–132
Greitz D, Hannerz J (1996) A proposed model of cerebrospinal fluid circulation: observation with radionuclide cisternography. AJNR Am J Neuroradiol 17:431–438 Greitz D, Hannerz J, Rähn T et al (1994) MR imaging of cerebrospinal fluid dynamics in health and disease. On the vascular pathogenesis of communicating hydrocephalus and benign intracranial hypertension. Acta Radiol 35:204–11 Hachatrian VA, Bersnev VP et al (1998) Hydrocephalus: pathogenesis, diagnosis, and surgical treatment. Medicine, Saint Petersburg, p 230 (in Russian) Konovalov A N, Kornienko VN, Ozerova VI, Pronin IN (2001) Pediatric neuroradiology. Antidor, Moscow, p 435 (in Russian) Kupriyanova O, Aroutiunov N et al (2004) Cerebral spinal flow (CSF) in patients with Chiari I malformation: phase-contrast MRI data. 21st annual meeting of the European Society of Magnetic Resonance in Medicine and Biology, 9–12 2004, Copenhagen, Denmark Maytal J, Alvarez L, Elkin C, Shinnar S (1987) External hydrocephalus: radiologic spectrum and differentiation from cerebral atrophy. Am J Roentgenol 148:1223–1230 Nitz W, Bradley W, Watanabe A et al (1992) Flow dynamics of cerebrospinal fluid: assessment with phase-contrast velocity MR imaging performed with retrospective cardiac gating. Radiology 183:395–405 Palm W et al (2006) Intracranial compartment volumes in normal pressure hydrocephalus: volumetric assessment versus outcome. AJNR Am J Neuroradiol 27:76–79 Parkkola R et al (2001) Cerebrospinal fluid flow in children with normal and dilated ventricles studied by MR imaging. Acta Radiol 42:33–8 Purin VR, Jukova TP (1976) Congenital hydrocephalus. Medicine, Moscow, p 215 ( in Russian) Yoshihara M, Tsunoda A, Sato K, Kanayama S, Calderon A (1998) Differential diagnosis of NPH and brain atrophy assessed by measurement of intracranial and ventricular CSF volume with 3D FASE MRI. Acta Neurochir (Wien), 71:S371S–374
Chapter 11
11
Intracranial Infections
11.1 11.2 11.3 11.4 11.5 11.6
Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . Bacterial Infection .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Granulomatous Infections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fungal Infection (Mycosis) of the CNS .. . . . . . . . . . . . . . . . . . . . . . Viral Infections .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parasitogenic Disorders .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
945 946 964 969 975 988
11.1 Introduction According to most authors, the incidence of infectious and parasitogenic diseases rises worldwide, despite the fact that new methods of treatment and creation of new antibiotic and anti-inflammatory drugs have appeared (Yakhno and Shtulman 2003; Whitemann et al. 2002). This increase is partially supposed to be due to increasing incidence of acquired immune deficiency syndrome (AIDS), and due to use of immunosuppressive drugs in cancer therapy and organ transplantation. The incidence of life-threatening CNS infections may be connected with several adverse factors, such as presence within the focus of infection, open brain injury, liquorrhea, sinusitis, otitis, etc., especially in immunodeficient patients. Early diagnosis is crucial in these cases. In addition to thorough neurological and laboratory (CSF tests) examinations performed, neuroimaging techniques, such as CT and MRI are very helpful. Cranial vault, meninges, and blood–brain barrier (BBB) protect brain and spinal cord from internal and external infections. Nevertheless, different pathogens (bacteria, viruses, fungi, and parasites) may invade the CNS via blood or after immediate contact of CNS tissue with focus of infection. Such structural peculiarities of the brain as absence of lymphocytes, small number of capillaries in subarachnoid spaces, and presence of perivascular CSF spaces lead to development of inflammatory reaction caused by pathogens that enter intrac-
ranial or intravertebral spaces. CSF is a suitable environment for dissemination of an infectious process. If intracranial infection is diagnosed, then it is crucial to detect its exact location. It can narrow the circle of differential diagnosis and sometimes even suggests the type of pathogen, which leads the way to administer appropriate treatment in the early stage of the CNS infection, and to predict the course and outcome of the disease. Infectious pathogens may enter brain tissue and cause focal inflammatory lesions (abscesses, cysts) or diffuse lesions (encephalitis), and inflammation of meninges (meningitis, ependymitis, arachnoiditis) or CSF spaces (subdural or epidural empyema). Phlebitis and thrombophlebitis of cerebral veins are also distinguished. Aetiology of these disorders is miscellaneous: it may be bacterial, viral, fungal, toxic, postinfectious, parasitogenic, or traumatic. A significant part of infectious lesions in the CNS, which may have variable manifestations considerably sophisticating the diagnosis, is represented by HIV infection—infectious diseases in humans with AIDS. CT and MRI give additional information for diagnosis of many pathological processes, including infectious ones. High tissue contrast, facilities for multiplanar neuroimaging, and absence of bone artefacts steer specialists to consider MRI as a method in diagnosis. MRI is of crucial importance if pathology is located in the posterior fossa, paratentorially, or on the convex CNS structures, and if small lesions without obvious mass effect are present. MRI is superior over CT in diagnosis of old as well as early haemorrhages, and in diagnosis of ischaemic lesions and infarctions that may accompany infectious process, as it is well known. MRI with CE is more sensitive in detection of meningeal lesions than is CT with CE. In addition to traditional techniques, new MR technologies that give additional and sometimes unique data are applied nowadays in diagnosis of intracranial infections. Diffusionand perfusion-weighted MR studies improve identification of acute stroke and assess viability of affected tissues and risk of infarction. MRS may give in vivo biochemical information. Nowadays MRS is an important tool in diagnosis of CNS infections. In this chapter, we describe CT and MR features of several intracranial infections and the contribution of new
946
Chapter 11
MR technologies in assessment and differential diagnosis of specific neuroinfections and parasitogenic disorders.
11.2 Bacterial Infection Bacterial infection mainly disseminates intracranially via a haematogenic route from a remote infectious focus, with subsequent involvement of meninges, subcortical white matter, and choroid plexus. In addition, pathogens directly disseminate via bone lesions from the local infectious focus in patients with otitis, mastoiditis, and sinusitis, or disseminate along cranial nerves after injury or surgical intervention.
11.2.1 Subdural Empyema Subdural empyema (SE) is encountered in about 13–20% of all cases of bacterial intracranial infection and in about 5% of subdural mass processes (Weinman 1972). Empyema is frequently associated with abscesses, especially in late stages of infectious brain disorders. SE was a poorly curable disorder in the past, and was characterised by high mortality (up to 40% of cases). When CT/MRI facilities for early diagnosis of SE were applied, the rate of mortality significantly reduced. The most frequent aetiology of SE is purulent disorders of cranial sinuses, for instance, frontitis, which according to several reports, is diagnosed in about 40% of those affected. Less frequent aetiological factors are complications of purulent otitis, penetrating cranial injury, craniotomy, and osteomyelitis of bone grafts. SE may be a complication of purulent meningitis in infants or a result of subdural haemorrhage suppuration. Two problems are distinguished in the pathogenesis of SE, and progressive retrograde thrombophlebitis is the main one. Less probable is infection via altered dura mater. The predominant location of SE is convex brain surface— in up to 80% of all cases. Location in the interhemispheric fissure is seen in 20% of cases. There are over 50% of cases of SE with supratentorial location, and less than 10% of infratentorial location. On CT, subdural empyema usually appears as a crescentshaped, hypodensive area over an affected hemisphere. Its density is higher than that of CSF, 10–12 Н.U. (Fig. 11.1). In cases of large empyemas, mass effect with compression of adjacent brain structures is prominent. Sometimes hypodensity of the surrounding brain tissue is seen due to oedema, inflammatory reaction, or ischaemia. After CE, a clearly enhanced demarcation zone appears, which separates empyema from brain tissue due to formation of granulation tissue on the border with brain tissue. MRI is a preferable method for diagnosis of SE in comparison with CT. This is especially true in cases of neuroimaging of small planar mass lesions on the cerebral convex, or accumulations of pus located over or under tentorium cerebelli. In these cases, MRI in the coronal plane is indicated. Traditional series of MR images without CE in most cases may identify dura mater by a characteristic low-intensity signal in all
Fig. 11.1 Subdural empyema on the left side. CT of a 16-month-old child—suppuration of subdural haemorrhage, occurred after shunting operation
scanning sequences on the border between brain tissue and empyema. On Т1- and Т2-weighted images, the MR signal of empyema is usually higher than that of CSF in cerebral ventricles. In addition, MRI visualises concomitant inflammatory changes of adjacent brain tissue (infarctions, venous thromboses) that appear as areas of MR signal change on T2 and FLAIR sequences. MRI with CE gives information more reliable about spatial distribution of empyema and expansion of dura mater inflammatory involvement. Internal and external rims of empyema are usually enhanced. Differential diagnosis should be made between subacute and chronic subdural haemorrhages and hygromas. Medical history, clinical signs, and results of CSF tests if available should be mandatory, considered along with neuroimaging data.
11.2.2 Epidural Empyema Epidural empyema (EE) is observed less frequently than the subdural type. The most frequent aetiological factors are purulent disorders of sinuses (especially frontal) and cells of the mastoid process. That may explain why empyema is frequently located in the frontal convex region. Among other aetiological factors, postoperative complications rank second, such as osteomyelitis of rims of a trepanated bone or a bone graft. Bone injuries with penetration of pathogen into the epidural space may also be an aetiological factor. CT without CE may fail to detect a small EE, or it may be revealed as a hypodensive area without clear-cut borders, adjacent to the internal bony lamina and has a convex shape. Contrast enhancement improves demarcation of purulent
Intracranial Infections
content of empyema from brain tissue due to enhancement of infected dura mater (Figs. 11.2, 11.3). If empyema is located along the median axis, then falx may be separated from the internal bony lamina. If empyema is located on the convex surface of a cerebral hemisphere, then the differential diagnosis between epidural and subdural empyema may be difficult. In these cases such additional features as presence or absence of soft head tissue involvement (oedema or subaponeurotic suppuration) above the site of empyema, presence of air and, for instance, posttraumatic bone defects may help; presence of inflammatory changes of cranial sinuses may contribute to the clinical picture also. That is why it is essential that CT examination should entail sinuses in patients with suspected intracranial suppuration. As in diagnosis of SE, it is preferable to use MRI in EE diagnosis, especially with CE. On Т1- and Т2-weighted images, purulent content has more hyperintense signal than has CSF (Fig. 11.4). MRI is better than CT is in imaging of bordering dura mater—it is the most reliable criterion in differentiation of sub- and epidural locations of the process. However, MRI lags behind CT in demonstration of concomitant destructive bone changes in osteomyelitis, and it is less sensitive in detection of small amounts of air. Nevertheless, there are published cases where a combination of subdural and epidural suppuration was diagnosed. Application of diffusion programs in MRI also improved precision of diagnosis of empyema in the parameningeal space—suppuration has a prominently hyperintense signal on DWI irrespective of the applied b value of the pulse sequence (Osborn 2004).
947
11.2.3 Brain Abscesses Brain abscesses (BA) are a relatively rare intracranial pathology accounting for about 1–8% of cases, worldwide regardless of the economic level of a country in which the study was performed (Bhatia 1973; Osenbach and Loftus 1992). The increase in the number of AIDS patients led to the increased incidence of BA. The male to female ratio is 2:1, and average age of affected patients is 35–45 years. In 25% of cases, BA develops in children and adolescents younger than 15 years. BA is rarely diagnosed in children younger than 2 years, usually only after meningitis caused by Citrobacter diversus or other gram-negative bacilli. In adults, BA developing after haematogenic dissemination is frequently caused by anaerobic bacteria or by a combination of aerobic and anaerobic microbes. In children, the most frequent pathogens are staphylococci, strepto- and pneumococci. In patients with brain injury or who underwent surgery, abscesses are usually caused by Staphylococcus aureus. Pathogenesis of BA is well studied. Several ways of dissemination of infection into the cranial cavity are distinguished. It is thought that in 45–70% of all cases of BA, contact dissemination from a parameningeal focus takes place, for instance, via otitis or sinusitis. Mainly it occurs through the zone of osteomyelitis or in a retrograde way via venae emissariae. Haematogenic dissemination is typical for 25% of patients, especially as a complication of lung infection (Zhuchenko 1963). Location within the middle cerebral artery territory is typical for it, on the border between grey and white matter,
Fig.11.2a,b Multiple subdural empyemas. MRI (a,b) with CE demonstrates the zones of pathologic accumulation of the contrast medium in the right frontal and temporal regions adjacent to posttraumatic bone defect
948
Chapter 11
Fig. 11.3a–d Epidural empyema in the left frontal region and inter hemisphere cleft from
the left. CT was performed after blunt-force skull–brain trauma before (a,b) and after (c,d) CE on the background of extensive posttraumatic bone defects detect low-density zones of convex form. After intravenous contrast medium administration, the increase of the capsule density was detected
Fig. 11.4 Multiple epidural empyemas in the left forehead region and interhemispheric
fissure (from the left). CT after severe skull–brain trauma. A small abscess in the contusion region is also present (arrow)
Intracranial Infections
and with poor formation of capsule, multiple lesions, and high level of mortality. Factors predisposing one to BA are chronic lung infections, osteomyelitis, cholecystitis, gastrointestinal infections, purulent skin disorders (furunculosis, etc.) Less frequently, BA is diagnosed in bacterial endocarditis, RenduWeber-Osler disease, and congenital cardiac defects. • In contact dissemination: –– Otitis and mastoiditis (abscesses of the temporal lobe and cerebellum) –– Sinusitis (abscess of the frontal lobe in frontitis) –– Meningitis (rare) –– Orbit phlegmone (furunculosis) • In haematogenic dissemination: –– In adults: infectious lung diseases (abscesses, bronchoectasis, empyema) –– In children: congenital cardiac defects with right-to-left shunting –– Pulmonary arteriovenous fistulas, congenital haemorrhagic telangiectasia (up to 5% of patients ) –– Bacterial endocarditis (rare) –– Bacteriaemia associated with intracranial infectious foci, in particular in dental surgery • Penetrating brain injury • Neurosurgical operations (10% of all purulent and inflammatory complications) It was shown in experiments that formation of BA has four stages of histopathological transformation (Britt et al. 1981): 1. Early cerebritis (nonencapsulated infectious focus in the brain)—weakly separated focus with diffuse inflammation, perifocal oedema, and brain tissue destruction. It is formed in days 1–3. 2. Late cerebritis—the central part of the infectious focus suppurates and necrotises with formation of cavity filled with semi-liquid purulent content (days 4–9). 3. Beginning of capsule formation—increase of the layer of fibroblasts with a rim of neovascularisation and reactive astrogliosis (days 10–13) 4. Capsule formation—thickening of capsule with reactive collagen (later then 2 weeks) It is noteworthy that timing of BA development and transition from one stage to another may vary greatly depending on many factors, e.g. preexisting conditions at the inception of infection (for instance, chronic brain hypoxia caused by concomitant diseases, etc.), as well as on the type of pathogen and ways of its dissemination. It was shown that in contact dissemination, abscesses have capsules thicker than those in haematogenic dissemination. The clinical picture of the disease is nonspecific, and course may be fulminant or slow, depending on the immune status of the patient, virulence of the pathogen, location of the abscess, and presence of concomitant purulent complications (meningitis, ventriculitis, rupture of the abscess wall, etc.). In cases with hemispheric location, headache, fever, and motor deficits predominate. In cases with location in the posterior cerebral fossa, nystagmus, ataxia, and intracranial hypertension are present. Epileptic seizures are seen in 25–45% of cases, and
949
meningeal signs are observed in 25% of patients. Early diagnosis of the inflammatory process is crucial for correct choice of tactics and successful treatment of BA. CT and MRI before and after intravenous CE are the most effective techniques of abscesses imaging. Traditional CT and MRI applied for differential diagnosis of mass lesions in the brain have high sensitivity (95%), but low specificity (50– 60%). That is why they do not always allow determining the type of pathological process before surgeon. Pathologically cerebritis is considered localised but poorly delineated areas of brain tissue attenuation with foci of necrosis, oedema, petechial haemorrhages, and perivascular inflammatory infiltration. On Т2-weighted MR images, early cerebritis appears as areas of high signal intensity, which are weakly or not distinguished from the perifocal oedema (Fig. 11.5). Proton density–weighted, Т2-weighted and FLAIR MR images, visualising early changes in brain tissue, detect cerebrates earlier than does CT. On Т1-weighted MR images, cerebrates appear iso- or hypointense to normal brain tissue, with possible mass effect manifested by compression of gyri and/or adjacent cerebral ventricle. On Т1-weighted MR images, foci of subacute haemorrhages may be revealed in the affected regions as well as areas of hyperintensity relatively to normal or oedematous brain tissue. CE in the early stage is usually mildly pronounced and heterogeneous. On CT, the affected area may not be detected at all or appear as hypodensive area without clear border with brain tissue. A focus of cerebritis transforms to an abscess when liquid necrosis occurs in its central part, which is clearly visualised on CT and especially on MRI, and separated by a collagen capsule. Duration of abscess maturation varies from 2 weeks to several months. The majority of patients see a doctor in the stages of late cerebritis or mature abscess. In over 50% of cases of haematogenic dissemination, a solitary abscess is found, which is usually located on the border of grey and white matter within the anterior or middle cerebral artery territories (more often in the frontal or temporal lobes). The most typical CT and MRI feature of the mature abscess is a presence of a round structure with thin-walled capsule intensively accumulating contrast medium (the ring phenomenon), with clear-cut and smooth borders (Figs. 11.6, 11.7). However, even in typical cases, it may be difficult to differentiate an abscess from another intracranial mass with ringshaped CE seen on CT and/or MRI (glioblastoma, metastasis, multiple sclerosis, tuberculoma, cysticercosis, etc.). In typical abscesses, the central part is hypodense on CT and has heterogeneous signal changes on MRI, increased on Т2- and decreased on Т1-weighted images relative to brain tissue (Figs. 11.8, 11.9). On Т1-weighted images, the signal from the central part is always higher than of CSF in the lateral ventricles. On Т2-weighted images, MR signal intensity varies, depending on TE in a spin echo pulse sequence, on protein content, and viscosity of the central absdess content. On MRI without CE, a mature abscess often has a rimmed periphery. The signal on the margin of abscess is isointense or mildly more hyperintense than those of the white matter on T1weighted imaging, and is hypointense on Т2-weighted MRI.
950
Chapter 11
Fig. 11.5a–c Abscess of the left frontobasilar region (in the stage of
celebritis). T2-weighted MRI (a): changes of MR signal are minimal (arrow). After CE (b), focal accumulation is noted (arrow). On CT,
performed 2 weeks later (c), an area of pathological enhancement increased and hypodense perifocal oedema appeared
Fig. 11.6 Abscess of the left frontal lobe.
CT with CE—spherical mass lesion with thin capsule and perifocal oedema
Fig. 11.7a–c Abscess of the right paracentral region. MRI in T2 (a), and T1 (b) sequences and after intravenous CE (c) visualises spherical
mass lesion with a thin capsule intensively accumulating contrast medium
Intracranial Infections
951 Fig. 11.8 Abscess of the left frontal lobe. СT
without CE demonstrates hypodense mass lesion with relatively clear spherical border
Fig. 11.9a–d Abscess of the left frontal region. MRI in T1 (a) and
T2 (b) sequences reveals spherical mass lesion with sufficiently thick capsule and perifocal oedema. The capsule of the abscess is hyperintense on T1-weighted imaging (arrows) and hypointense on T2-weighted imaging. DWI (c): typically hyperintense MR signal. 1H MRS (d) demonstrates the acetate peak (Ac), lactate peak (Lac), and amino acids peak (АА); the NAA peak is decreased
952
The signal properties of the abscess periphery are due to collagen, products of haemorrhages, and presence of free paramagnetic radicals in macrophages participating in phagocytosis and heterogeneously distributed on the abscess periphery. Successful surgical or therapeutic treatment of abscess leads to decrease of activity of macrophages and disappearance of the hypointense rim. Thus, presence of the rim may be the best indicator of treatment efficacy, even better than residual CE, which may be seen on MRI with CE several months after treatment cessation. However, a typical picture of an abscess with thin-walled capsule and smooth internal border is not always found. Thus, in a complex study of 10 patients with BA, we visualised typical features on CT and MRI in only five cases. In three cases, thickness of capsule was 5–8 mm, with small amount of pus in the centre (Fig. 11.10). Such thickening of an abscess wall is due to the chronic course of the disease (Pronin et al. 2002). In 20–30% of cases, the features of abscess on standard CT or MRI may be nonspecific, with knobby, but not thin internal borders of capsule. The shape of an abscess may also be irregular (Fig. 11.11). Multiple abscesses are rarely encountered (Figs. 11.12, 11.13). Supratentorial location is typical for BA. However, in practice, posterior fossa abscesses are also seen (Fig. 11.14). Filial abscesses, as experience shows, appear as smaller areas with ring-shaped enhancement on the periphery, located nearby, and often along the medial wall of the paternal abscess (Fig. 11.15). The volume of oedema surrounding an abscess may exceed volume of the abscess itself and may be the cause of accompanying mass effect. If abscess ruptures into the ventricular system, then ependymitis develops and enhancement of the border of the ventricles is seen in addition to ringshaped enhancement. Purulent masses do mildly differ from
Chapter 11
CSF by their signal, causing mild hyperintensity on Т1- as well as on Т2-weighted MR images. Definite experience and thorough analysis of signal characteristics are required for correct interpretation of the abscess wall rupture (Fig. 11.16). Nevertheless, despite the early diagnosis, purulent tamponade of the ventricles is usually indicates a poor prognosis. At present echo planar pulse sequences and new MR techniques are available such as DWI, perfusion MRI, and MRS, which markedly increased MRI specificity, reaching 100% of the precision of diagnosis. On DWI, prominent hyperintensity in the central part of the abscess is seen (it is a purulent, necrotic zone), which is evidence for decrease of water diffusion in that site. ADC values in the central part of the abscess and in capsule are significantly lower (Р < 0.005), than in the cerebral white matter (Table 11.1), if the (diffusion factor) b value is 500 or 1000 s/mm2. The reason for impaired diffusion of water molecules in the central part of an abscess is mainly linked to the high viscosity of pus, which contains many cellular elements and their remnants. Ebisu et al. (1996), studying in vitro pus aspirated from abscess, found hyperintense signal and low ADC values on DWI and ADC maps. It is also noteworthy that on ADC maps, low ADC values do not characterise the content of every abscess. According to our studies, in approximately 25% of cases ADC parameters of pus may exceed that of white matter. High T2 value of pus may influence ADC values when ADC maps are construed—a possible explanation. In our series of DWI, we could reliably diagnose rupture of abscess capsule and the subsequent tamponade of the lateral ventricles (Fig. 11.16). In our opinion, DWI specificity is markedly higher than that of CT or MRI with CE in early
Fig. 11.10a–c Abscess of the left occipital region. On MRI in T2 sequence (a), T1 before (b) and after CE (c), a cyst and a small annular formation with thick, well-enhanced walls is detected. High MR signal on T2-weighted imaging in the centre of the mass lesion detects remnants of pus (arrow)
Intracranial Infections
953
Fig. 11.11a–h Case 1. Abscess of the left
parietal lobe. T1-weighted imaging with CE in axial (a), sagittal (b), and coronal (c) projections demonstrates a mass lesion with irregular borders. Case 2. Abscess of the left frontal region. Т2-weighted imaging (d) and DWI (e): abscess has a dumbbell shape and a thick capsule. Pus inside the abscess cavity is hyperintense on DWI. Case 3. Abscess of the right parietal region. T1-weighted imaging with CE (f), Т2-weighted imaging (g), and DWI (h)
954
Chapter 11
Fig. 11.12a–c Multiple abscesses in the right hemisphere in a 5-year-old child. CT (a–c) with CE: annular contrast accumulation in the ab-
scess walls with prominent oedema in the temporoparietal–occipital region. The right lateral ventricle is severely compressed; the ventricular system is grossly displaced to the left
Fig. 11.13a–c Multiple abscesses in the frontal lobes of the brain. T2-weighted imaging (a) and T1-weighted imaging (b) MRI show restricted
spherical areas of changed MR signal. Capsule is better visualised on T2-weighted imaging. After enhancement (c), two abscesses with flat internal walls are clearly visualised
Fig. 11.14 Two-chamber abscess in posterior cranial fossa in an 8-year-old child. CT with CE: capsule of the abscess is hyperdense
Intracranial Infections
955
Fig. 11.15a–c Abscess of left frontal region. CT (а) and MRI (b,c): a filial abscess is visualised at the frontal border (arrows).The pus has high MR signal on DWI (с)
Fig. 11.16a–c Right parieto-occipital region abscess rupture into the
subarachnoid space and the ventricular system. T2-weighted imaging (a) and T1-weighted imaging (b) after CE demonstrate an atypical MR picture of an abscess of irregular shape (resembling manifestation of glioblastoma or metastasis). CE of its capsule is heteroge-
neous. On DWI (c), high MR signal is detected not only from the abscess itself, but also from pus in the lateral ventricles and the subarachnoid spaces (arrows). Increased MR signal on T2-weighted imaging from ependyma and periventricular white matter are the features of ventriculitis
Table 11.1 Acquired diffusion coefficient (ADC) of water diffusion in the pathological brain tissues –3
2
2
2
2
ADC (× 10 (mm /s)
Abscess (b = 500 s/mm )
Abscess (b = 1,000 s/mm )
Glioblastoma (b = 1000 s/mm )
Abscess capsule/tumour
1.01 ± 0.16
0.997 ± 0.09
1.18 ± 0.09
Oedema
1.83 ± 0.31
1.65 ± 0.25
1.59 ± 0.16
Pus/necrosis
0.58 ± 0.14
0.65 ± 0.15
2.15 ± 0.34
White matter
0.84 ± 0.07
0.8 ± 0.04
0.82 ± 0.04
956
Chapter 11
Fig. 11.17a–g Case 1. Micro-abscess of the right frontal region. CT (а,b) reveals micro-
annular lesion in the right frontal lobe with density increase after CE (b). On T2-weighted imaging (c) and DWI (d), a small mass lesion with perifocal oedema is visualised. On the follow-up examination after treatment (2 months), the hyperintense MR signal from the central part of the abscess disappeared on DWI (arrow) (e). Case 2. Multiple brain abscesses. On T2-weighted imaging, there are multiple cystic lesions in the left temporal region and the splenium of corpus callosum (f). On DWI (g), two abscesses in capsules with high signal in the centre are detected (big arrows). A site of high MR signal in the projection of the left thalamus without capsule—in the stage of late cerebritis (small arrow) and a hypointense cyst of the left temporal region after sanation of pus (doubled arrow) are seen
Intracranial Infections
957
stage of capsule formation as well as when a capsule is already formed, especially in multiple and/or small brain abscesses (Fig 11.17). Appearance of abscess on standard CT and MRI, namely the phenomenon of ring-shaped CE and perifocal oedema of different extent, require making differential diagnosis from several other pathologies, such as those with tumoral or nontumoral origin that have resembling neuroimaging picture. Among tumours, malignancies should be first considered, such as a solitary metastasis or glioblastoma. Among nontumoral pathologies subacute haemorrhages and relapsing demyelinating diseases should be considered. ADC values inside the zone of ring-shaped enhancement for abscesses and glioblastomas are adduced in Table 11.1. In patients with glioblastomas, higher ADC values than those in abscesses are revealed within the central area of necrosis. DWI is becoming a highly informative neuroimaging technique in patients with abscesses, namely for monitoring treat-
ment efficacy. If treatment effect is positive, then pus disappears from the abscess cavity, and that leads to reduction of initially high signal on DWI (in acute stage) and to reduction of the lesion volume. If the disease progresses, then the volume of abscess cavity increases and high signal intensity of its content is preserved (Fig. 11.18). Purulent inflammatory complications after neurosurgery is a rare, however severe phenomenon. In these cases, DWI becomes the only reliable technique to assess the content of postoperative cavity (Figs. 11.19–11.21). MRS is also a technique that may improve specificity of MRI in diagnosis of BA (Dev 1998; Burtscher 1999; Gary 2004). MR spectra acquired from the central part of an abscess are quite characteristic. In spectra of untreated abscess, there are acetate peaks (1.92 ppm), Lac (1.3 ppm), Ala (1.5 ppm), and succinate (2.4 ppm), and pyruvate complexes peaks (0.9 ppm), and such amino acids as Val, Leu, and Ile are included (Fig. 11.22). Acetate, Lac, succinate, and pyruvate are
Fig. 11.18a–f Abscess of the left parietal region before and after antibiotic therapy. T2-weighted imaging (a) and T1-weighted imaging before (b) and after (c) CE demonstrate a small annular formation
with marked perifocal oedema. DWI confirms the diagnosis (d). Two weeks after treatment reduction of the abscess, absence of capsule enhancement (e) and partly elimination of pus (f) are seen
958
Chapter 11
Fig. 11.19a–c Purulent complication after surgical elimination of glioblastoma. FLAIR (а) and T1-weighted imaging after CE (b) detect areas of pathological MR signal change and enhancement. DWI
(c) demonstrates typically high MRI signal from pus, confirming the reason of worsening of the patient’s condition in the early postoperative period
Fig. 11.20a,b Purulent complication after the surgical intravascular occlusion of the internal carotid artery at the level of clinoid part in a patient with the saccular aneurysm of bifurcation. MRI 6 months after sugery visualises the abscess in the mediobasal temporal region: T1-weighted imaging after CE (a), DWI (b = 500)—high MR signal from pus with an artefact from the iron marker of the balloon (b)
Fig. 11.21 Purulent complication of the surgical intravascular occlusion of the internal carotid artery. The series of CT scans with CE 3 months after sugery visualises abscess in the posterior cranial fossa. Artefact from the iron marker of the balloon is seen in the projection of temporal bone pyramid
Intracranial Infections
959
Fig. 11.22a–e Abscess of the left parietal-
occipital region. T2-weighted imaging (a) and T1-weighted imaging before (b) and after (c) CE (respectively), and MRS (d) from the central part of the abscess (peaks detected in the spectrum are outlined on the picture), and DWI (b = 1000) (e)
end products of metabolism of microbes. Acetate and succinate are never seen in necrotic tumours and hence, they serve as reliable markers of pyogenic abscesses. However, these two resonance peaks are not always seen in the MR spectrum of an abscess cavity. Revealed in vivo MRS, an amino acid peak (Val, Leu, and Ile) at 0.9 ppm is also never seen in necrotic or cystic tumours, but it is typical for abscess. These amino acids appear as a result of proteolytic activity of polymorphic leukocytes. To identify peaks of these amino acids the study is performed with ТЕ = 136 ms to acquire and inverted peak that is well differentiated from adjacent non-inverted peaks. In vitro MRS showed that the content of these amino acids in the abscess cavity is 20–78 times higher than that of cystic or necrotic tumours (Lai et al. 2005). The content of these amino acids in a tumour is below the threshold of imaging, which is why if a tumour is examined with ТЕ = 136 ms, peaks that correspond to them are not seen. The central part of a cystic or necrotic tumour is frequently characterised by a single Lac peak. Thus, presence of the inverted peak in a spectrum at 0.9ppm frequency is a reliable indicator of diagnosis of a brain abscess. The typical spectrum of a bacterial abscess always differs from the typical spectrum of a cystic or necrotic tumour. However, in our experience, in single-voxel MRS when a capsule wall enters the area of interest, one may acquire a picture resembling a tumour, such as a single Lac–Lip complex in the absence of peaks from other metabolites. In such cases, MRS
should be repeated with more precise placement of the area of interest. MRS is also useful to assess treatment efficacy. Ebisu (1996) examined 22 patients with verified abscesses after combined (antibiotics plus surgery) treatment. Lactate and amino acids were present in spectra before and after treatment, but acetate and pyruvate disappeared a week after cessation of combined treatment. Other authors reported disappearance of succinate, acetate, Ala, and other amino acids on the 20th day after treatment with antibiotics, but the Lac peak was preserved (Osenbach and Loftus 1992; Ebisu 1996).
11.2.4 Ventriculitis Infectious damage to ependyma with subsequent inflammatory process (ventriculitis or ependymitis) is, as usual, a complication of meningitis, abscess rupture into the ventricular system, and after surgery, in particular after ventricular catheter placement (Lyke 2001). Mortality reaches 80%. On CT without CE, there is a dilatation of ventricles, with the presence of a fluid. A hypodense area may be seen paraventricularly. Its volume depends on the severity of infectious brain load (Fig. 11. 23). On Т1-weighted MR images, there is a ventriculomegaly and hypointense signal of ependyma and adjacent brain tis-
960
Chapter 11
Fig. 11.23a–f Ventriculitis with progression to diffuse encephalitis in a patient after partial resection of internal base of the skull meningioma and placement of the ventricular catheter in order to treat acute hydrocephalus. The series of CT scans without CE (a–f) verifies
ventriculomegaly, and prominent hypodensity of the white matter in the cerebral hemispheres with brainstem involvement. Hyperdensive areas in the periventricular area are haemorrhages (arrows)
sue. On Т2-weighted and FLAIR images, this area is hyperintense with involvement of corpus callosum. It differs in its inflammatory changes from those of transependymal CSF impregnation, for instance, in decompensated obstructive hydrocephalus. In separate cases, it is possible to visualise dense protein elements within the cavities of the lateral ventricles with formation of fluid. On MRI and CT with CE, there is an enhancement of walls of the lateral ventricles (Osborn 2004).
Before entering the CNS, bacteria usually colonise the mucous membrane of the nasopharynx, and then enter subarachnoid space via a haematogenic pathway or via local tissue invasion. Bacteria may enter meninges directly via anatomic cranial defects or from parameningeal spaces, for instance, nasal or middle ear sinuses. Inflammatory reaction leads to proinflammatory cytokines, interleukine-1 and -6, and tumour necrosis factor-α release, which increases BBB permeability, leads to vasogenic oedema and changes in cerebral blood flow, and may cause direct neurotoxic effects. These changes are prominent on the convex brain surface in infections caused by Streptococcus and Haemophilus, and on the brain base in infection caused by Neisseria meningitidis. Complications of bacterial meningitis are brain oedema, hydrocephalus, and brain infarction, but the infection of brain tissue itself is rare. Complications may appear after several days or weeks and are diagnosed in almost 50% of adults with bacterial meningitis. Frequently, they are cerebrovascular events. Cortical
11.2.5 Meningitis The aetiological and predisposing factors for bacterial meningitis may be a somatic infection (pneumonia, parameningeal infection), head injury, defect of meninges, preceding surgery, cancer, alcoholism, or immune deficiency etc. The type of pathogen depends on age and predisposing factors (Table 11.2).
Intracranial Infections
961
Table 11.2 Bacterial meningitis pathogens Pathogen
Age and predisposing factors
Streptococcus agalactiae Escherichia coli Listeria monocytogenes Citrobacter
<3 months
Neisseria meningitidis Streptococcus pneumoniae Haemophilus influenzae
3 months–8 years
N. meningitides S.pneumoniae
18–50 years
S. pneumoniae L. monocytogenes Gram-negative bacteria
>50 years
L. monocytogenes Gram-negative bacteria
Impairment of cellular immunity
S. pneumoniae Gram-negative bacteria staphylococci
Brain injury, neurosurgery, CSF shunt
infarctions lead to rupture of arachnoid membrane, which is a barrier to dissemination of infection. As a result, abscesses develop in adjacent cortical regions and white matter. Lesions of brain parenchyma with oedema and mass effect may be diffuse or focal. Subdural accumulations forming after infectious damage of arachnoid membrane and its necrosis become separated and transform into empyemas. Inflammatory occlusion of CSF pathways causes hydrocephalus. Ventriculitis is a relatively rare complication of leptomeningitis. MRI without CE in patients with uncomplicated bacterial meningitis usually shows no changes. MRI with CE usually visualises enhancement of thickened meninges around cerebral hemispheres (Fig. 11.24). Despite that, signs of meningeal enhancement may be revealed by CT with CE; nevertheless, MR diagnosis is superior over that of CT, especially if programs with magnetisation transfer and FLAIR sequence are used. Multiplanar MRI better visualises a loss of subarachnoid space elasticity with dilatation of the interhemispheric fissure, which, according to several authors, is an early sign of acute meningitis. Thus, standard MRI and MRI with CE reveals more features of meningitis itself and of its further complications in comparison with CT, including infarction, cerebritis/abscess, subdural empyema, and ventriculitis. Cortical and subcortical infarctions appear as areas of hyperintensity on T2-weighted MR images and are revealed earlier than on CT. Occlusions of small perforating arteries lead to infarctions in basal ganglia, and spasm of the anterior and middle cerebral arteries cause large infarctions in the corresponding vascular territories. DWI confirms acute infarction more clearly. In patients with subacute infarction, MRI usually demonstrates sulcus-like CE. MRA confirms spasm or arterial occlusions. Haemorrhagic infarctions have typical features on Т1 and Т2 MR images, depending on timing of their develop-
ment. Occlusion of cortical veins with dural venous thrombosis may be revealed. Hydrocephalus is a common consequence of meningitis. It may be open or obstructive, and it is more frequently seen in children than in adults. Hydrocephalus itself is detected on both CT and MRI; however, MRI assesses the site of occlusion or the absence of such a site with more precision. CSF flow may be seen and quantitatively assessed by phase-contrast angiography in a cine regimen. Periventricular accumulation of CSF (transependymal impregnation), secondary to ventricular obstruction, is better visualised on proton-weighted, T2-weighted, and FLAIR images, where they appear as hyperintense areas around the ventricular system.
11.2.6 Neuroborreliosis (Lyme Disease) Neuroborreliosis (Lyme disease, Lyme borreliosis [LB])—is an infectious, transmissive, multisystem disorder occurring in the natural focus that is caused by the spirochete Borrelia burgdorferi, is transmitted by ticks, and is apt to chronic remitting-relapsing course. As it is transmitted by ticks, the majority of LB cases occur in summer. Statistical analysis shows that LB incidence is two to four times higher than that of tick encephalitis, and account for 0.7–3.2 cases per 100,000 per year in Russia (Lobzin et al. 1996). The incubation period is 2–30 days, 2 weeks on average. The disease manifests in several stages and has skin, joint, cardiac, and neurological signs; however, it is not mandatory that every stage be seen in each patient for diagnosis. Ring-shaped erythema (erythema migrans) is seen in the site of tick bite in up to 70% of patients—the first stage of LB. Fatigue, headache, neck extensor rigidity, arthralgia/my-
962
Fig. 11.24a–c Bacterial meningitis. T2-weighted imaging (a) and T1weighted imaging with CE, in axial (b) and coronal (c) projections reveal open hydrocephalus, pathologic thickening, and enhancement
Chapter 11
of meninges around the cerebral hemisphere. On T2-weighted imaging, high signal from subarachnoid spaces indicates the of absence of CSF pulsation
Fig. 11.25a–f Chronic stage of neuroborreliosis. MRI in T2 sequence (a–f) reveals mildly hyperintense lesions in the white matter of the
cerebral hemispheres
Intracranial Infections
algia, anorexia, sore throat, and nausea may be present. In the second stage (acute neuroborreliosis) symptoms and signs are caused by dissemination of Borrelia from the primary skin lesion in different organs with predominant involvement of the nervous system (serous meningoradiculitis or Bannwarth syndrome, meningitis, cranial neuropathies), heart (myocarditis), joints (large joint polyarthritis), muscles (myositis), eyes (conjunctivitis, iritis, choiroiditis, papillary oedema), liver, etc. Neurological signs of LB may appear a month to a year after a bite, i.e., on the second stage (dissemination) or on the third stage (late manifestation) of the infection. In the last stage, progressive or remitting-relapsing course may be seen with remissions of variable duration. Usually any of various syndromes can predominate (neurological, skin, joint, or cardiac) (Yakhno and Shtulman 2003). If acute onset of the disease was absent, then diagnosis on the third stage is difficult, as the connection of the disease with history of tick bite is lost. In the past, white matter involvement in LD was explained by a complex of immune mechanisms developing after spirochete invasion of the brain. Modern techniques allow finding in a cerebral biopsy of LB patients, small amounts of spirochetes, with a negligible inflammatory reaction. Standard MRI in LB patients does not reveal any signal changes in the brain in the acute phase of the disease, but sometimes multiple bilateral periventricular hyperintense lesions without mass effect are found on T2-weighted images. As it is reported, these lesions resemble MS plaques; however, other cerebrovascular diseases and demyelinating diseases should also be kept in mind. Lesions may appear in basal ganglia and in the brainstem. MRI is more sensitive for these processes than CT is. CE in patients with cranial neuropathies reveals pathological enhancement of the cisternal portions of the third and the fifth cranial nerves, or, less, frequently, spinal roots on T1-weighted images. In chronic stage, periventricular cerebral lesions without severe mass effect and focal enhancement may be seen (Fig. 11.25).
11.2.7 Syphilis Syphilis, as well as LB, is a primary infection caused by spirochetes, and is a chronic disease with well-known stages. The pathogen causing syphilis is Treponema pallidum. Since 1986– 1989, the incidence of syphilis markedly increased, mainly due to HIV infection. In approximately a fourth of cases, T. pallidum invades the CNS, where it causes asymptomatic meningitis (asymptomatic neurosyphilis). Two main types of symptomatic syphilis are meningovascular and parenchymal. Mixed form with progressive paralysis and tabes dorsalis is frequently seen. Timing of symptoms onset in meningovascular syphilis is 5–10 years, and that of tabes dorsalis is 25 years. It is suggested that syphilis progresses more rapidly in HIV-infected individuals. Acute and subacute syphilitic meningitis usually develops within the first 2 years after contamination, mainly in middleaged males. Meningeal neurosyphilis in the form of syphi-
963
litic meningitis usually leads to hydrocephalus, cranial neuropathies, and formation of gummae. Extensive thickening of meninges and meningeal perivascular infiltration are seen on pathological studies in these patients. Optic, facial, vestibulocochlear, oculomotor, trigeminal, and abducens cranial nerves are more frequently involved. On histology, syphilitic gummae present as round masses of granulomatous tissue encircled by mononuclear cells and fibroblasts with inclusions of giant cells and perivasculitis. Gummae are the result of intense leptomeningeal inflammatory reaction in the early stage of neurosyphilis. They are rarely found. In the brain, gummae originate from meningeal connective tissue and vessels; they expand to the neighbouring parenchyma and are located above the brain convex surfaces near dura mater and brain tissue. They vary from 1 to 4 cm in size, and may be solitary or multiple. Necrosis may be found inside gummae, but spirochetes are rarely present. In chronic meningoencephalitis progressive paralysis develops, which is accompanied by cortical atrophy and ependymitis. The biopsy of grey matter sometimes detects spirochetes. The clinical picture of meningovascular neurosyphilis is characterised by headache and focal neurological deficit with pleocytosis, increased protein, and positive serologic CSF tests. Two types of vascular lesions are distinguished in neurosyphilis: Heubner’s and Nissl-Alzheimer’s endarteritides. Huebner’s endarteritis is more frequently encountered; it affects large and middle-calibre arteries with subsequent occlusion of the latter. Nissl-Alzheimer’s type of arteritis is less frequently seen; it affects small-calibre vessels, the occlusion of which is caused by intense proliferation of endothelial and adventitial cells. Both types of arteritis lead to occlusion of vessels. Tabes dorsalis is related to the group of myelopathies and is due to atrophy, degeneration, and demyelination of the posterior spinal roots and the spinal cord. A triad of symptoms is typical for this disorder—piercing pain, dysuria, and ataxia, and a triad of meningeal signs (Argyle-Robertson pupil, areflexia, and delirium). Argyle-Robertson pupil is also seen in progressive paralysis, and is a small pupil with irregular shape and without reaction to light. Diagnosis is confirmed by serology and CSF tests. On CT, a third of all studies usually fail to find any changes, and in another third of studies, only cerebral atrophy is seen. On MRI as well as on CT, secondary signs of vasculitis may be seen such as small infarctions or ischaemic lesions (Atlas 1996). Multiple hyperintense lesions are seen on T2-weighted images in grey as well as in white matter and in subcortical structures. Multiple infarctions may be seen in large arterial territories involving supra- and infratentorial structures as well as basal ganglia. Postcontrast MRI may reveal enhancing lesions of subacute infarction. MRI is superior to CT in imaging of pathological meningeal CE. To confirm acute infarctions, diffusion MRI is applied and to confirm stenosis or occlusion, MRA is used. Gummae appear as masses of affected tissue near the brain surface with
964
Fig. 11.26a–f Neurosyphilis. Gummae of the right frontal region.
T2-weighted imaging (а–c) reveals the area of heterogeneous MR signal increase in the convex right frontal lobe. In the projection of subcortical structures leftwards, a small, old infarction is seen (ar-
nodular or ring-shaped enhancement, and meningeal enhancement may be present nearby (Fig. 11.26). Congenital syphilis is a result of transplacental contamination of foetus in the second or the third trimester of intrauterine development. Pathological study of the brain reveals infiltrates in meninges with mononuclear cells. Infiltrates are located in the basal regions of dura mater and in meninges encircling cranial nerves. Frequently infiltrates disseminate via Virchow-Robin spaces. Lesions in cerebral parenchyma are rare. In most cases of congenital syphilis, neurological signs are absent within the first weeks. During this period, metaphyses of tubular bones are changing (20%). Neurological signs develop during the first 2 years of age: epileptic seizures, cranial neuropathies, and intracranial hypertension. CSF tests reveal pleocytosis and high protein content. Later optic nerve atrophy, blindness, neurosensory hearing loss, and tabes dorsalis develop. On CT and MRI with intravenous contrast, enhancement accumulation of contrast is seen in dura mater. Inflammatory infiltrates may enter brain tissue through
Chapter 11
row). On T1-weighted imaging (d) without CE, a mildly hypointense pathological area is seen. The cortical picture is lost. After CE (e,f), an area of contrast accumulation that involves cortical surface is revealed (arrow)
Virchow-Robin spaces and may be enhanced. If cerebral infarction is present, then it has a corresponding appearance on CT and MRI.
11.3 Granulomatous Infections 11.3.1 Tuberculosis Since 1986, there has been an increased incidence of tuberculosis (TB) is observed with higher proportion of extrapulmonary symptoms, which may be explained by the AIDS epidemic and multidrug resistance to Mycobacterium tuberculosis (Jinkins et al. 1995; Engin 2000). According to studies done in the United States, 28–31% of patients with TB are HIV-seropositive. And, conversely, 5–9% of AIDS patients have TB. CNS involvement is found in all age groups, in average in 2–5% of TB patients. At the same time, most cases (up to 60–70%) include those of patients younger than 20. Neuro-
Intracranial Infections
tuberculosis is one of the troublesome forms of systemic TB, as it is characterised by high mortality and high risk of neurological deficits and complications (Atlas 1996; Carcia-Monco 1999; Uysal 2001). TB is a postprimary infection in adults, and primary in children. Signs of neurotuberculosis are miscellaneous, ranging from a diffuse form—TB leptomeningitis—to focal forms, such as cerebritis/abscess and tuberculoma. Regrettably, it is quite difficult to diagnose TB. It is noteworthy that a neuroimaging picture of TB may mimic many other neurological disorders. As well, according to several reports, in 50% of neurotuberculosis patients, no other extracranial signs of the disease were revealed (Menon 2004). Tuberculosis of meninges (ТМ), is usually a result of reactivation of latently persisting mycobacterial infection. Primary contamination usually occurs via droplet contact. Mycobacteria enter meninges and superficial brain tissue via a haematogenic route from lungs. Here microbes remain inactive in the tubercles or microgranulomas (Rich’s foci), which later may rupture into the subarachnoid space and cause tuberculosis of meninges (Skrikanth et al. 2007). ТМ is the most frequent syndrome of neurotuberculosis and is mainly diagnosed in children and adolescents. The clinical picture of leptomeningitis is usually that accompanied by fever, headache, confusion, and meningeal signs. Several mechanisms in the pathogenesis of TM are distinguished. The first is a rupture of tubercles or granulomas into the CSF spaces. The second is increased permeability of meningeal vessel walls in a haematogenic route of dissemination. Less frequent types of dissemination are the rupture of a microtubercle in miliar form of TB, or, least frequently, the contact dissemination from the focus of bone TB. In any case, basal meninges are affected first, and then basal cisterns are filled with gel-like exudate. Arteries passing through the exudate are involved in the inflammatory infiltration directly as well as indirectly, due to reactive obliteration (arteritis), which leads to angiospasms, thromboses, and infarctions. Arteritis is present in 28–41% of basal meningitis cases. Infarctions are more frequently seen in children than in adults. The middle cerebral artery and its branches are most frequently involved, especially, small branches supplying basal ganglia. These infarctions are usually bilateral. Both CT and MRI make quite a reliable diagnosis of such lesions, but MRI reveals them earlier. A typical consequence of TM is hydrocephalus, which is well visualised on both CT and MRI. CE in basal cisterns and meninges is better visualised on MRI (Skrikanth et al. 2007). Usually in TM, a patient’s hydrocephalus is open; it develops secondarily due to obliteration of CSF resorption pathways, but sometimes hydrocephalus may be obstructive due to focal brain lesions with mass effect or occlusion of narrow CSF pathways due to granulomatous ependymitis. Thus, neuroimaging signs of TM are following: • Basal meningeal CE • Hydrocephalus • Supratentorial and brainstem cerebral infarctions
965
Final diagnosis is usually made by inoculation of M. tuberculosis from CSF, which requires several weeks and a considerable amount of CSF. Polymerase chain reaction (PCR) may be used for diagnostic purposes. Mortality in adults in ТМ exceeds 25%, and it is even higher in children. The most frequent form of TВ affecting brain tissue, tuberculosis granuloma (tuberculoma). Granulomas consist of a central, solid necrotic core encircled by a collagen capsule, epithelial cells, giant polynuclear cells, and mononuclear inflammatory cells. TB bacilli may be found in the necrotic core and in the capsule. Oedema and proliferation astrocytes are present outside of the capsule. Tuberculomas may be located in cerebral cortex, in cerebellum, in the subarachnoid, subdural and epidural spaces, as well as in the spinal cord, and they may be solitary or multiple (Bernaerts et al. 2003). Cortical and subcortical brain tissue and periventricular white matter are usually involved. In most cases, tuberculomas are revealed supratentorially, but in children, they are more frequently located infratentorially (Kumar et al. 2000). Rare sites of tuberculoma location are the sella turcica, the cerebellopontine angle, the pineal region, and in the cerebral ventricles. Combination with meningitis is not seen in all cases. More frequently, tuberculomas are found in patients with the miliar form of pulmonary TB. On CT, tuberculomas are seen in only a few TB patients. Among them, in 10–34% lesions are multiple. CT with CE visualises small foci with ring-shaped enhancement. In a third of patients, a specific sign is seen—a centrally located petrificate or a dot-like enhancement surrounded by a hypodense area with a rim of hyperdensity. However, this sign is not pathognomonic. On MRI without CE, granulomas are isointense with grey matter on Т1-weighted images, and they may have a hyperintense rim (due to possible accumulation of paramagnetic substances that shorten T1, for instance, free radicals, etc.). On Т2-weighted images, MR signal of tuberculoma varies. Frequently, it is more iso- or hypointense, than the brain tissue is, due to T2 shortening as a consequence of free radicals in macrophages, which heterogeneously disseminated within the granuloma. Thicker than brain tissue, mature tuberculoma has hypointense signal on T2-weighted MR images. Granuloma may be hyperintense on T2-weighted MR images if fluid content is present (necrosis). Surrounding oedema is mild and, as CT shows, always less than oedema surrounding a bacterial abscess of the same size. In the initial stages of granuloma formation, oedema is more prominent. Postcontrast MRI of tuberculomas demonstrates nodular or ring-shaped types of enhancement (Figs. 11.27–11.29). Calcifications are better seen on CT. On MRI, they are better visualised with gradient echo pulse sequence. In Table 11.3, neuroimaging features that are revealed in tuberculomas of different structures are summarised. Atrophy is a late consequence of TB infection of the CNS. Months or years of therapy are required for resection of a cerebral tuberculoma. Tuberculosis abscess is a rare complication, which is seen in 10% of all patients with neurotuberculosis. In contrast to caseous tuberculomas (with separate bacilli), abscesses are
966
Chapter 11 Fig. 11.27a–f Tuberculosis menin goencephalitis in a 5-year-old child. On T2-weighted imaging (a,b) and T1-weighted imaging with CE (c–f), multiple tuberculomas combined with diffuse involvement of meninges and the choroid plexus of the late ral ventricles are seen, with prominent enhancement of the latter
Intracranial Infections
967 Fig. 11.28a–f Cerebral tuberculomas. T2-weighted imaging (a–c) reveals multiple hyperintense areas in the cerebral hemispheres. T1-weighted imaging with CE (d–f): sites of signal increase in the chiasmal and the circumferential cisterns, in the anterior section of interhemispheric and lateral fissures, in the right lenticular nucleus, and left frontal lobe
968
Chapter 11
Fig. 11.29a–f Cerebral tuberculoma. T2-weighted (a) and FLAIR (b) MR images: hyperintense lesion in the convex surface of left temporal
lobe. T1-weighted imaging before (c) and after (d,e) CE—prominent and homogeneous enhancement is noted. On DWI, (f) MR signal intensity is not increased
Table 11.3 CT and MRI features of tuberculomas Structure
CT
CT with CE
MRI
MRI with CE
Noncaseous
Hypo-, isodense
Homogenous enhancement
Т1: Hypointense Т2: Hyperintense
Homogenous enhancement
Caseous with solid centre
Hypo-, isodense
Heterogeneous central enhancement, ringshaped enhancement
Т1: Hypo-, isointense Т2: Hypo-, isointense
Ring-shaped enhancement
Caseous with fluid centre
Hypodense
Ring-shaped enhancement
Т1: Hypointense Т2: Hyperintense
Ring-shaped enhancement
Intracranial Infections
filled with semi-fluid pus with many tuberculosis bacilli. The walls of tuberculosis abscess have no giant-cell epithelial granulomatous reaction (Provenzale and Jinkins 1997). It is thought that abscesses may develop due to spontaneous opening of a typical caseous tuberculoma, with leakage of its liquid content. ТВ abscesses are larger than tuberculomas are and have more rapid clinical course. Their features resemble those of bacterial abscesses; however, they are frequently multichambered (Atlas 1996; Palmer 2002). On CT, tuberculosis abscesses are hypodense, and surrounded by oedema and mass effect. Postcontrast studies demonstrate ring-shaped enhancement, with a thin and homogenous rim, which, however, may be thick and irregular. The abscess is detected by the central core of fluid purulent necrosis and surrounding oedema. The central core is hyperintense on Т2-weighted MR images. The lesion appears the same as on CT. Comparison of studies in HIV-positive and HIV-negative individuals with TM reveals hydrocephalus, with identical frequency in these groups. Non-enhanced lesions (predominantly infarctions) are seen in 27% of cases in HIV-positive and only in 6% of cases in HIV-negative groups. Meningeal signs are also more prominent in the HIV-positive, with enhancement of meninges in 23% of cases and only 6% in HIVnegative cases. Infarctions, enhancement of meninges, and parenchymal lesions are more frequent in the group of HIVpositive patients with TB (Atlas 1996; Osborn 2004). Tuberculosis encephalopathy is a diffuse involvement of brain tissue usually seen in children with pulmonary TB. Diffuse oedema of brain tissue is seen on CT and MRI. Usually the disease leads to a fatal outcome within 2 months after onset of neurological symptoms despite the tuberculostatic therapy (Dastur et al. 1995). Spinal tuberculosis. With improvement of MRI techniques, it became possible to make live diagnoses of spinal forms of TB. In contrast to other spinal infections, involvement of all components of the vertebral channel in the infectious process is a characteristic feature of TB (Gupta 1994). Several forms of the disorder are distinguished—tuberculosis radiculomyelitis, intramedullary tuberculoma, epidural phlegmone, and abscess. The clinical picture as a whole is nonspecific and may resemble features of a tumour, polyradiculopathy, or a spinal demyelinating process. TB bacilli are rarely found in CSF (Dastur 1995), which is why other diagnostic tests play a first-line role in correct interpretation of changes within the vertebral channel. MRI should be preferred, as this technique allows describing lesions of the spinal cord, meninges, and epidural space more precisely (Sharma 1997).
11.3.2 Neurosarcoidosis It is thought that the CNS involvement in systemic sarcoidosis is a rare phenomenon (Kellinghaus 2004; Osborn 2004). Onset of the disease with neurological signs is observed in less than in 7% of patients, and CNS involvement is diagnosed less than in 15% of patients. Sarcoidosis is usually diagnosed in patients within the age range of 30–40 years; females are affected more frequently.
969
Two main types of the CNS involvement are distinguished, (1) involvement of meninges and ependyma and (2) involvement of brain tissue. Granulomatous involvement of leptomeninges is diagnosed if optic nerve chiasm, the pituitary, the bottom of the third ventricle, and the hypothalamus are affected. As a result, open hydrocephalus is common. Intracerebral lesions in sarcoidosis appear as poorly separated areas of brain tissue changes, resembling brain tumours. Brain CT fails to reveal any changes in 60% of patients with CNS involvement in sarcoidosis. In meningeal lesions, CT pictures cannot be distinguished from that of bacterial meningitis, with thickening and enhancement of basal meninges. Open hydrocephalus as a single sign may be seen in several cases. If brain tissue if affected, then separate hyperdense areas are revealed (on CT without CE) in the temporal and, less frequently, the frontal lobes parenchyma. These areas are intensely and homogenously enhanced; however, their borders are not clear-cut. A combination of pathologically thickened and enhanced meninges and involvement of adjacent brain tissue may be seen on frontal CT scans (Mirfakharee 1986). Despite the fact that MRI is superior to CT in detection of CNS involvement in sarcoidosis, CE is always required. On MRI without contrast enhancement, one may only suspect thickening of basal meninges and detect areas of signal change in surrounding brain tissue as hyperintense areas on T2-weighted and FLAIR images. After intravenous administration of contrast medium, prominent and homogenous enhancement of basal meninges is seen, which may involve sellar and suprasellar regions, and optic chiasms (Fig. 11.30). CE may expand deeply into the adjacent brain tissue, having an appearance of tongues of fire, which is explained by dissemination of granulomatous lesions via perivascular spaces. As usual, granulomas in sarcoidosis are not visible on Т1weighted images (or are hypointense), and are hyperintense on T2-weighted images. If a systemic process (i.e. pulmonary involvement etc.) is not proven, then differential diagnosis should be made between intracerebral tumours, metastases and, less frequently, from multiple sclerosis. Follow-up MRI with CE may reveal the reduction of lesion load as well as reduction of its distribution into the spinal cord (Lexa 1994; Smith 2004).
11.4 Fungal Infection (Mycosis) of the CNS Fungal infection if affects the CNS is considered an opportunistic granulomatous disorder, which may be acute and fulminant, or chronic and slowly progressive. Fungi may invade the CNS and cause meningitis and brain tissue lesions (Table 11.4) in patients affected with systemic mycoses. MRI and CT features of fungal infections resemble those of tuberculosis (Lyons and Andriole 1986; Sze and Zimmerman 1988). CT and MRI may reveal a mass lesion, abscesses, infectious foci in orbits or nasal sinuses, and hydrocephalus (Figs. 11.31, 11.32). CT frequently underestimates the distribution of pathology in patients with fungal diseases. MRI is more sensitive in fungal diseases, but it also often cannot dif-
970
Chapter 11
Fig. 11.30a–f Neurosarcoidosis. T2-weighted imaging (a) and T1weighted imaging (b): the area of heterogeneous signal change in the right temporal basal region. After enhancement (c–f), the area of contrast accumulation in the right temporal region is visualised
along with additional enhanced areas along the brainstem meninges (double arrow) and cranial nerves—long arrow indicates lesion of the left oculomotor nerve
Table 11.4 Pathogens of fungal meningitis
a
Pathogen
Conditional pathogenicity
Other structures affected
CSF changes
Cryptococcus neoformans
Sometimes in AIDS
Lungs, bones, joints
Viscous consistency, stain by Indian ink, cryptococcal antigen positive reaction
Coccidioides immitis
Absent
Lungs, skin, bones
Complement binding reaction is positive
Candida
Present
Mucosae, skin, oesophagus, urogenital system, heart
Gram-positive staining
Aspergillus
Present
Lungs, skin
Neutrophilic pleocytosis
Mucor
Present (in diabetes mellitus)
Orbits, nasal sinuses
Histoplasma Capsulatum
Sometimes
Lungs, skin, mucosae, heart, visceral peritoneum
Blastomyces Dermatitidis
Absent
Lungs, skin, bones and joints, visceral peritoneum
Actinomycesa
Absent
Jaws, lungs, abdominal cavity, orbits, sinuses, skin
Nocardiaa
Present
Lungs, skin
Microbes having an intermittent taxonomy between bacteria and fungi
Intracranial Infections
971
Fig. 11.31a–e Abscess of the right occipital re-
gion (caused by Nocardia). T2-weighted imaging (a), T1-weighted imaging (b) without CE, and a series of T1-weighted imaging with CE (c–f): a cluster-of-grapes-shaped, multicystic structure with clearly contrasted capsule is visualised
972
Chapter 11
Fig. 11.32a–f Mycotic granuloma of the left superior orbital fissure and the cavernous sinus. T2-weighted imaging (a), T2-weighted imaging (b,c), and FLAIR (d,e) detect a lesion in the projection of the
left cavernous sinus, the left superior orbital fissure, and the orbital infundibulum. CT with CE (f): a homogenous enhancement of granuloma is detected
ferentiate various fungal lesions. Several features are inherent in different types of fungi. Thus, among frequently encountered fungi, there are distinguished, conditionally pathogenic microbes, which affect only immune deficient patients (Candida, Aspergillus, Mucor) and microbes that infect immunocompetent individuals. Cryptococcosis and histoplasmosis may occur in previously healthy, as well as in immunocompromised people. Candida, Aspergillus, Mucor, and Cryptococcus neoformans are ubiquitous; other fungi are endemic and live in definite geographic areas. Moreover, a pathophysiology of fungal disorder of the CNS depends on the type of fungus. Fungi that reproduce as yeast (by division), invade the CNS via the haematogenic route (Cryptococcus and Histoplasma), enter microvascular system of meninges, and penetrate through the vessel wall, causing acute or chronic leptomeningitis. Less frequently, intracerebral lesions are found, such as granulomas or abscesses (Gaviani 2005). Fungi, which reproduce by spores in the infected tissue (Aspergillus, Mucor) or by pseudospores (Candida) invade brain parenchyma, not meninges, as the blood supply of meninges is not sufficient for their reproduction. Spore forms of fungal colonies may invade and occlude large, middle, and small arteries, which may lead to brain infarction and cerebritis.
Infection of the CNS by Candida species frequently leads to disseminated intracerebral micro-abscesses, secondary to occlusion of small arterioles (Zimmermann 1987). C. neoformans is a fungus that most frequently affects the CNS in HIV-infected individuals. Clinical manifestation of fungal infection is seen in 6–7% patients. In 45% of HIV-infected patients with cryptococcosis, clinical manifestations are mainly presented by fungal infection (Davenport et al. 1992). The typical route of infection is inhalation. Cryptococcosis of the CNS leads to basal meningitis. A common and frequently single sign of subacute fungal meningitis is a headache. Neck muscle rigidity, seizures, and intracranial hypertension may also occur. Diagnosis is based on staining, detection of cryptococcal antigens or inoculation of fungal culture from the CSF. MR picture of fungal meningitis is nonspecific. CT is often negative. Features revealed by CT such as atrophy and open hydrocephalus are nonspecific. CE of meninges may occur in immunodeficient patients. MRI is more sensitive to fungal infections than CT is, but it often fails to reveal any change. MRI with CE may visualise enhancement of meninges, which is usually not seen on MRI without CE (Whiteman et al. 2002). Dissemination of infection through the brain parenchyma occurs via haematogenic dissemination or via immediate
Intracranial Infections
dissemination through cerebral cortex. Parenchyma lesions in cryptococcosis may exhibit various forms, and there are controversial reports about this. Four types of fungal parenchyma lesions are distinguished: intracerebral mass lesions known as cryptococcomas, dilatation of Virchow-Robin spaces, parenchymal/leptomeningeal nodes, and a mixed form (Whiteman et al. 2002). Cryptococcomas are accumulations of microbes, inflammatory cells, and gel-like mucus materials. The relative quantity of separate elements may vary. It produces an image of a so-called gelatine cyst. Consistency of these cysts may differ in concentration, and they may have isodensive (on CT) or isointense (on MRI) signal. In AIDS patients with cryptococcosis, signs and pathological studies are frequently negative, probably due to absence of adequate immune response. That may explain why neuroimaging features are so “scanty” (Sze et al. 1987). Criptococcomas in AIDS patients infrequently accumulate contrast medium; however, this may occur in the immunocompetent patients also. Virchow-Robin spaces are the sites where fungi sediment and start to reproduce. Along the estuary of these perforating vessels passing from basal cisterns into brain tissue, fungi produce much mucus, which fills and enlarges perivascular spaces. It is more obvious in basal ganglia and midbrain, but may also be found in other brain regions (Mathews 1992). In these cases, the infectious agent lies outside the brain tissue and does not cause visible inflammation. Parenchymal/leptomeningeal nodes in cortex are represented by small granulomas (Sze et al. 1987). Features acquired during diagnosis of cryptococcosis depends on the individual. In the immunodeficient patients with CNS lesions, hydrocephalus is seen in 9% of cases, whereas in immunocompetent patients with cryptococcosis hydrocephalus is seen in 25% of cases. Enhancement of meninges is also less frequently seen in AIDS patients in comparison with patients without AIDS. In cryptococcosis of the CNS, hypodensive foci (<3 mm) that are not enhanced may be
973
found on CT in basal ganglia. They are represented by dilated Virchow-Robin spaces filled with cryptococci and mucus. Appearance of the intracerebral features varies. In basal ganglia of AIDS patients, larger cystic structures with septi are found. These gelatine pseudocysts are usually not enhanced. Mass effect is minimal, and there is no oedema. Intracerebral lesions and the oedema around them are smaller in cryptococcosis than in toxoplasmic encephalitis. Hypo- and isodense structures with ring-shaped or diffuse enhancement are seen on CT, especially in basal ganglia and cerebral hemispheres. Surrounding oedema and mass effects are seen. There are reports about intraventricular and chiasmal-sellar cryptococcomas (Fig. 11.33) (Popovich 1990; Kоnovalov et al. 2001). Finally, small, peripheral enhancing nodules may be combined with cortical granulomas. CT without CE reveals calcifications in such nodules. MRI shows conglomerates of small round lesions isointense to CSF in any pulse sequence, which indicates dilatation of Virchow-Robin spaces. Such lesions initially located in basal ganglia may be bilateral and frequently symmetrical. Analogous findings may be seen in the midbrain. Lesions are not enhanced with gadolinium and do not cause mass effect or oedema. Mass lesions (cryptococcomas) may appear variably depending on their structure. Gel-like pseudocysts isointense to CSF on Т1- and Т2-weighted MR images are not accompanied by oedema and do not enhance; however, mass effect may be seen around large lesions. Such lesions initially located in basal ganglia may be bilateral and frequently symmetrical up to 3 mm or several centimetres in diameter. Thus, areas of pathological signal <3 mm in diameter on MRI may be small cryptococci or dilatations of Virchow-Robin spaces (Mathews 1992). Criptococcomas may also appear as mass lesions in basal ganglia with perifocal oedema, causing mass effect and accumulating contrast medium. More frequently, it is seen in immunocompetent patients. In contrast to gellike pseudocysts, MR signal intensity of such lesions does not correspond to CSF intensity. Another form of CNS crypto-
Fig. 11.33a,b Cryptococcoma of the chiasmal sellar region CT with CE (a,b): an annular heterogeneous hyperdensive lesion, expanding to the cavernous sinuses. The borders of substance are clear-cut
974
Fig. 11.34a–i Aspergillosis of the CNS. On a series of CT scans (a–c)
without CE, a moderately hyperdense area in the projection of anterior horn of left lateral ventricle is seen. On T1-weighted imaging (d) and T2-weighted imaging (e,f), a subependymal area of MR signal change around the anterior horn of the left lateral ventricle is detected, which is deformed. Additionally in the left periventricular
Chapter 11
region, a hyperintense area is visualised—a lacunar stroke (arrow). MRI with CE (h,i) demonstrates an area of heterogeneous contrast accumulation in the projection of the anterior horn of the left lateral ventricle, and small lesions in the right choroid plexus and subependymal region of the right lateral ventricle triangle (arrows)
Intracranial Infections
coccosis produces a picture of multiple enhancing intracerebral or leptomeningeal nodules, suggestive for granulomas (Tien 1991). MR features of candidoses are nonspecific. On Т2-weighted MR images, Candida abscesses appear as clear-cut areas of hypointense signal encircled by a larger area of hypointensity, representing oedema (Sze et al. 1988). Some authors call this the “bull’s-eye” phenomenon. Rarely, candidoses may cause meningitis, meningoencephalitis, or form a granuloma. Aspergillus and Mucormycoses invade CNS immediately, penetrating through nasal sinuses or via haematogenic route. The later is seen more frequently. In immediate penetration, vascular invasion is frequently seen involving the cavernous sinus and circle of Willis vessels, which leads to angiitis, thrombosis, and infarctions. Dissemination into the subarachnoid space may cause meningitis and meningoencephalitis (Post 1984). Rarely, it may form atypical tumour-like lesions (Phuttharak 2005; Cho 2007). In haematogenic dissemination, usually from pulmonary lesions, Aspergillus settles in brain vessels, causing their occlusion and infarctions. The latter transform into septic infarctions with cerebritis and formation of abscesses, which are usually located near the anterior and the middle cerebral arteries. On MRI, lesions are well enhanced on the periphery in a ring shape, typical for abscesses, or the lesion may be encircled by a small area of tissue with prolonged Т1 and Т2, with CE and with mass effect or without (Fig. 11.34). Presence of haemorrhage is often a sign of Aspergillus infection. Mucormycoses of the CNS are phycomycoses caused by Mucor genes. Such infection is seen in patients with decompensated diabetes mellitus or in immunodeficient patients; however, it is rarely seen in AIDS patients. Mucomycoses of the CNS often has rhinocerebral (craniofacial) origin with perivascular or perineural dissemination via the ethmoid labyrinth into the frontal lobes, or along the orbit cover into the cavernous sinus. Intracranial mucormycosis leads to an infarction or a fungal abscess and usually involves brain base and cerebellum after invasion via contact way through the subtemporal fossa or the orbit. The area of infarction or abscess may be located at a site remote from the focus of primary contamination. Direct invasion in mucormycosis may cause basal meningitis. In assessment of skull base structures and occlusions of cerebral arteries in this area, MRI is superior to CT and is a method of choice to diagnose fungal infections. MRI visualises haemorrhagic and nonhaemorrhagic infarctions. Sinusitis usually appears hyperintense on Т2-weighted MR images, whereas aspergillosis (and other fungal infections) markedly reduce signal on Т1-, as well on Т2-weighted MR images, and shows peripheral CE. Hypointense signal may be a differential sign in diagnosis of mass lesions in cranial sinuses. In contact intracranial dissemination, areas of hyperintense signal are well demonstrated on multiplanar Т2-weighted MR images or on Т1-weighted MR images with CE, as areas of pathologically enhanced meninges or brain tissue. Infection of the CNS with Coccidioides immitis occurs via haematogenic route by dissemination of endosporae from a pulmonary focus. Endosporae 2–5 mm in diameter infect meninges, probably as do separate yeast cells of Cryptococcus
975
or Histoplasma (Kobayashi 1980). Inflammation of meninges with formation of purulent or caseous granulomas, especially on brain base, is usually seen in these cases. The most frequent signs on CT and MRI are pathological enhancement of meninges along the surface of hemispheres and in basal cisterns, open hydrocephalus, dissection of the fourth, or part of third or the lateral ventricles, with obstructive hydrocephalus. Less frequently focal thickening of the white or the deep grey matter is seen in the form of granulomas. Occlusion of vessels is quite rare; however, vasculitis may occur in Coccidioides infection.
11.5 Viral Infections Timely identification and precise diagnosis of a viral pathogen of the infectious CNS disorder are very important, as most of these diseases are curable. Viruses may affect CNS in three ways: (1) via the haematogenic route (viruses transmitted by arthropods), (2) via neural processes by axonal transport (herpes simplex virus), or (3) by causing autoimmune reaction that leads to demyelination of nerves (varicella zoster and influenza viruses).
11.5.1 Viral Encephalitis and Viral Meningitis Intracranial viral infections manifest by focal or diffuse inflammatory lesions in brain tissue (encephalitis) and in cerebral meninges (meningitis). Especially high is the incidence of viral meningitis and encephalitis in children and adolescents. Acute or chronic CNS infection may be aetiological factors. Viral encephalitis is frequently caused by pathogens of exanthematous paediatric infections, arthropod-transmitted viruses, and herpes simplex virus type 1 (Table 11.5). Main pathogens of viral encephalitis, endemic areas, carriers, etc. are recited in Table 11.5. Main pathophysiological features of viral encephalitis are neuronal degeneration and inflammation. Encephalitis is characterised by perivascular, muff-like lymphocyte infiltration and microglial proliferation, which are mainly present in grey matter. The spectrum of main histological features consists of mild to diffuse oedema and congestion with haemorrhage and necrosis (as in encephalitis caused by herpes simplex virus type 1 [HSV-1], type 2 [HSV-2], and arbovirus). Brain oedema of various extents is seen frequently as well as occlusion of meningeal vessels. The most frequent pathology in the general population is aseptic meningitides caused by enteroviruses (Coxsackie viruses and ECHO viruses) and less frequently by HSV (Jubelt 1984). In AIDS patients, pathogens that cause meningitis are HIV itself, sometimes HSV-1 and -2 and, especially, cytomegaloviruses (CMV). Condition in which signs of meningeal and brain tissue involvement are revealed simultaneously is defined as meningoencephalitis. On MRI, viral encephalitis appear as separate, nonconfluent areas of hyperintensity on Т2-weighted MR images, and iso- or hypointense on Т1-weighted MR images with different
976
Chapter 11
Table 11.5 Pathogens of viral encephalitis Pathogens
Carriers
Comments
Paediatric exanthema viruses Measles, varicella, mumps, rubella
Human
Rare
Alphavirus East equine encephalitis virus (US) Venezuela equine encephalitis virus (US, South America)
Mosquitoes
In children In infants and patients older than 50 years Mainly in adults
Flaviviruses Japanese encephalitis virus type B St. Louis encephalitis virus Murray valley virus West Nile virus Rochio virus (Brazil)
Mosquitoes
Caysanur-Forrest virus (India) Powassan virus (US) Spring tick encephalitis virus (Russia) Louping-ill virus (UK)
Ticks
Mainly in adults
Bunyaviruses California encephalitis virus Rift valley virus (Africa)
Mosquitoes
Mainly in children
Orbiviruses Colorado tick fever virus (US)
Ticks
Arboviruses
In adults In adults and the elderly
Other viruses Herpes simplex virus type 1 (HSV-1) Herpes simplex virus type 2 (HSV-2)
Human
Rabies virus
Wild and domestic mammals
features of mass effect (Fig. 11.35). Foci of subacute haemorrhage (extracellular haemoglobin) are hyperintense on Т1 weighted MR images (Fig. 11.36). Local or generalised cerebral atrophy is better visualised on FLAIR MR images. These basic features are seen in most cases of viral encephalitis: however, several infections have specific features that are characteristic to the individual infections and help in differential diagnosis. These features will be described below.
11.5.2 Herpes Viruses Herpes viruses are represented by a large group of viruses including HSV-1, HSV-2, CMV, Epstein-Barr virus (EBV), varicella zoster virus (VZV), B-virus, HSV-6, and HSV-7 (Tien 1993). All of them possess a molecular structure with a nucleus—double-stranded, helical DNA—and an envelope consisting of different glycoproteins that define intrafamilial differences between viruses. CNS infection by herpes virus family members may occur via a haematogenic route or by way of neuronal transmission from an extracerebral lesion into the brain. After a virus enters a human host, primary viraemia is observed with subsequent dissemination along the CNS. Virus invades the neural tissue via BBB or via contamination of
Focal neurological signs in neonates, children and adults; meningitis in older children
endothelial cells in the walls of intracranial arteries. These are the mechanisms of contamination in HSV-1, HSV-2, CMV, and EBV infections. In HSV-1 infection in adults but not in infants, VZV, or B-viral (Coxsackie B virus) infection occurs in the peripheral neurons and disseminates centrally via axons into the brain (Tien 1993), where it persists in a latent form and may reactivate thereafter. Clinical manifestations are proportional to the extent of viral replication (reproduction) in the neural tissue. Signs may vary from aseptic meningitides to severe encephalitis with fever, headache, mental disorders, and focal or diffuse neurological deficit.
11.5.2.1 Herpes simplex virus type 1 HSV-1 is a pathogen of 95% of all herpes encephalitis cases and is the most frequent cause of fatal sporadic encephalitis cases. In the United States, mortality in HSV encephalitis reaches 50–70%. In adults, this infection occurs in individuals with preexisting antibodies and, thus represents a reactivation of virus. In children, HSV-1 infection usually occurs soon after birth; infants are more frequently infected with HSV-2, which is the cause of 80–90% viral infections in neonates and
Intracranial Infections
Fig. 11.35a–d Viral encephalitis of the left tempo-occipital region. CT with CE (a), T2-weighted imaging (b) and T1-weighted imaging without (c) and with CE (d) detect a large area of pathologic density/signal change with prominent enhancement along the cerebral gyri
977
978
Chapter 11
Fig. 11.36a–d Viral encephalitis of the left parietal region. CT (a)—an area of heterogeneous density changes in the left parietal region. T2-weighted imaging (b) and T1-weighted imaging before (c) and after (d) CE demonstrate an area of MR signal change, with a focus of subacute haemorrhage and prominent enhancement, simulating an intracranial tumour
almost all congenital viral infections (Shaw 1993; Kоnovalov et al. 2001). The clinical picture in adults includes nonspecific mental changes, confusion, focal neurological deficits, and fever. CSF tests are nonspecific; it is difficult to inoculate HSV from CSF. Final diagnosis is made after brain biopsy. Viral DNA may be detected by PCR. In the immunocompetent patient (without AIDS), HSV1 may cause necrotising encephalitis of the temporal lobes and of the frontal lobes orbital surface. In addition, surfaces of insula, cerebral hemispheres and posterior regions of the occipital lobes may be affected. Lesions are usually bilateral with involvement of basal ganglia (Schroth 1987). Later as the lesion expands, it may involve cingulated gyri. It is thought that in adults HSV-1 encephalitis cases are caused by reactivation of latent HSV-1 infection in the trigeminal ganglion after intracellular dissemination of the virus via branches of the fifth cranial nerve, which innervates meninges of the anterior and middle cranial fossae. Infectious
lesions in brainstem may be found too, which are caused by the retrograde dissemination of the virus along the cisternal part of the fifth cranial nerve up to the brainstem. CT shows hypodense areas in the temporal lobes, sometimes with involvement of the frontal and occipital lobes (Fig. 11.37). CE and haemorrhages are rarely visualised. Correlations between CT, MRI, electroencephalogram (EEG) data, and CSF tests attests to the superior sensitivity of MRI over that of CT. In herpes encephalitis cases, MRI shows early signs such as oedema with hyperintense signal in the temporal and anterior parts of the frontal lobes on Т2-weighted and FLAIR images (Fig. 11.38). Hyperintense signal involves cortex as well as the white matter, and it may be seen as early as 48 h after first clinical signs manifestation (Bale 1987). On CT changes of density and contrast accumulation are reliably seen on days 3–5, and on days 4–11 with SPECT performed with iodine or technetium (Tien 1993). Mass effect occurs along with enlargement and confluence of separate lesions in a single large lesion. After that, infection is dissemi-
Intracranial Infections
Fig. 11.37 Herpes encephalitis. On CT scan, a hypodense area with irregular borders in the left tempo-occipital area is seen with prominent mass effect. The ventricular system is displaced to the right
nated from the temporal lobes along the Sylvian fissures to insulae, frequently sparing putamina. Usually, MRI shows involvement of both temporal lobes (the process may also be asymmetrical), whereas on CT only unilateral involvement is revealed. In the earliest stages, CE is frequently absent, but as the disease progresses, the extent of CE increases also, duplicating the borders of gyri (Figs. 11.38, 11.39). On autopsy, foci of haemorrhages are frequently found, which are poorly, if at all, seen on CT. Acute haemorrhage on MRI appears as an area of moderate or prominent hypointensity on gradient echo or T2-weighted MR images, which is almost isointense on Т1-weighted MR images. MRI is more sensitive than CT is in imaging of subacute haemorrhage. It is more feasible to use MRI when repeatedly administering antiviral therapy (Fig. 11.40). Brain atrophy is a late consequence of the infection (Fig. 11.41). In children, the inflammatory process is more diffuse; destructive changes may expand to parietal and occipital lobes. Mortality in HSV-1 encephalitis is 50–70%. There are reports that HSV-1 and -2 infections are present in AIDS patients but on rare occasion and are seen only in 2% cases on autopsy. In such patients, HSV leads to diffuse and not focal frontotemporal lesions. Along with the typical pathological features of necrotising encephalitis cases may be absent in AIDS patients, even if HSV-1 and -2 are inoculated in cultures of brain tissue. In immunodeficient patients, there is a reverse correlation between the extent of immune deficiency, severity of the inflammation caused by HSV, and disease progression rate.
11.5.2.2 Herpes Simplex Virus Type 2 HSV-2 is a main cause of encephalitis in neonates (Barnes et al. 1994; Girard and Zimmermann 2000; Barkovich 2000).
979
Primary contamination occurs during labour; however, sometimes it occurs via the haematogenic route and via the placenta during the intrauterine life (Tien 1993). The CNS is involved in 30% of affected children. As soon as the virus enters the brain, it rapidly disseminates along the white matter, due to low resistance of the immature immune system of neonates. Destruction of brain tissue takes several weeks. After that, ventricles and sulci became wide, large areas of cystic encephalomalacy appear between the ventricles and the brain surface, and periventricular calcinates may form (Fig. 11.42). If a child survives, then microcephaly develops. The incidence is 1 case per 2,000–5,000 neonates. The infection may cause seizures, microcephaly, microophthalmia, ventriculomegaly, multicystic encephalomalacy, and frequently is a cause of death. Pathological studies reveal acute or chronic inflammation of brain parenchyma and leptomeninges. In contrast to the frontotemporal location seen in adults, neonatal HSV infection is always diffuse and leads to massive brain destruction. In the early stage, CT may reveal a mild hypodensity of the periventricular white matter with relative preservation of deep grey matter and structures of posterior fossa (Whiteman et al. 2002). These signs may progress with involvement of the surrounding white matter and cerebral cortex. Later in the course of the disease, CT may reveal foci of haemorrhagic necrosis, calcifications in parenchyma, and areas of cystic encephalomalacia. MRI changes reflect the process of brain destruction. In the initial stage with moderate brain oedema, diagnosis is difficult due to the inhability to differentiate the process from normally myelinated white matter in neonates. As destructive changes increase, areas of MR signal change appear in cortex and adjacent structures of the white matter (up to cyst formation), more frequently in the temporal, the frontal, and less frequently in the parietal lobes; lesions tend to increase in size and to become confluent. In unilateral destruction, compression of the ipsilateral ventricle occurs and then dislocation of ventricles from the median axis develops. Sometimes MR signal changes appear as separate asymmetrically located islands. MRI is more sensitive at the stage of cyst formation, when areas of characteristic signal changes appear on Т1- and Т2-weighted MR images.
11.5.3 Varicella-Zoster Virus VZV causes two diseases, varicella and herpes zoster. A smiliar histology is characteristic for both diseases, such as skin changes and CNS infection manifesting itself as haemorrhagic necrosis with intranuclear eosinophilic inclusions. Varicella is a highly infective disease, manifesting itself by generalised skin rash; it is seen predominantly in children without serious complications. However, in patients with immune deficiency it may be complicated by encephalitis. Varicella as a CNS infection may cause transverse myelitis, meningoencephalitis, cerebellar ataxia, and septic meningitides. Neurological complications of varicella manifest in less than 1% of infected patients. Cerebellar ataxia is combined with skin rash. In patients
980
Chapter 11
Fig. 11.38a–h Herpes encephalitis. There is
region of increasing of MR signal intensity on T2-weighted imaging in the left temporal lobe (a,b) and FLAIR (c,d). On T1-weighted imaging before (e,f) and after (g,h) CE, there are no sites of contrast accumulation within the site of the lesion in the temporal lobe
Intracranial Infections
Fig. 11.39a–i Herpes encephalitis. Acute stage. T2-weighted imaging (a,b), and T1-weighted imaging (c,d) detect an extended area of pathologically changed MR signal in the right temporal lobe. On T1weighted imaging, the hyperintense lesions are visualised (sites of haemorrhagic transformation). On FLAIR images (e,f), additional
981
lesions in the right frontal and left temporal regions are better visualised. After intravenous contrast injection, the cortical enhancement is demonstrated (g,h). 1H MRS: depression of the NAA peak, mI, and Lip–Lac complex peaks are increased (i)
982
Chapter 11
Fig. 11.40a–f Herpes encephalitis 2 weeks after onset, treated with antiviral therapy. T2-weighted imaging (a,b) and T1-weighted imaging before (c,d) and after (e,f) CE reveal the reduction of the area of increased MR signal. Dislocation syndrome ceased. There are signs of haemorrhagic transformation of cortical portion of the right temporal and frontal lobes. Cortical CE became more prominent. Improvement of clinical status was observed
Intracranial Infections
Fig. 11.41a–f Outcome of herpes encephalitis. T2-weighted imaging
(a), FLAIR (b), and T1-weighted imaging (c) performed 3 months since the onset of the disease demonstrate evidence of marked atrophy of the frontotemporal regions, ventriculomegaly, and dilatation of the subarachnoid space. Residual foci of haemorrhagic transfor-
983
mation of cortex of the temporal lobes persist (increased signal on T1-weighted imaging). After CE (d), small areas of pathologic enhancement along the cerebral gyri are detected. There is no signal change in the brain tissue on DWI (e). 1H MRS registers a low peak of NAA along with a sufficiently high and broadened Lip–Lac peak (f)
984
Chapter 11
Fig. 11.42a–c Outcome of herpes encephalitis. A 2.5-year-old child. CT 2 years after recovery (a–c). Prominent hypodensity of the white
matter and multiple calcinates, more leftwards, are seen. There is asymmetrical dilatation of the lateral ventricles. Bilayer subdural haemorrhage over the left brain hemisphere is seen
with cerebellar ataxia, which usually regresses spontaneously, neuroimaging is negative (Whiteman et al. 2002). Meningoencephalitides are rare complications of varicella; however, they are poorly tolerated due to fever, headache, nausea, seizures, and confusion they cause. They usually develop 11 days or several weeks after the onset of the disease. CSF testing reveals mild to moderate lymphocytic pleocytosis with elevated protein. EEG reveals diffuse changes. MRI detects multiple hyperintense foci in cerebral cortex on Т2-weighted and FLAIR images. Mortality is usually low in the immunocompetent patients. Infection of the CNS caused by herpes zoster may manifest as encephalitis, neuritis, myelitis, and/or ophthalmic herpes. These complications are rarely seen during the clinical course in healthy adults, but the risk of CNS involvement in the immunodeficient patients is higher. Immunocompetent individuals frequently develop cranial neuropathies, whereas AIDS patients and other immunodeficient patients frequently develop diffuse encephalitis (Reichman 1978). Latent virus persisting in the ganglia, especially of the fifth and the seventh cranial nerves, may reactivate, and then start to disseminate into the brainstem, causing encephalitis. If a fever, meningeal signs, and confusion develop in a patient with herpes zoster, then such a diagnosis may be suspected. A CSF test is not specific; it reveals mild pleocytosis, mild elevation of protein, and normal glucose content. MRI may show hyperintense signal in brainstem and supratentorial grey matter on Т2-weighted MR images, and may reveal enlargement of brainstem despite that CT is negative (Tien 1993). Cranial and peripheral neuropathies are seen in the dermatomes where characteristic skin lesions are found. Involvement of the fifth cranial nerve is manifested by trigeminal neuralgia along the nerve branches, by headache, and sometimes by reduction of corneal reflex. The ophthalmic portion of the fifth cranial nerve is the most frequently affected branch (herpes zoster ophthalmicus); the disorder manifests itself by
way of pain syndrome and formation of skin vesicles within the area of the ophthalmic portion of the fifth cranial nerve innervation. Direct angiography detects local stenosis or occlusions, which are often unilateral and are located in the proximal segment of the middle and anterior cerebral arteries or the carotid siphon. CT and MRI may reveal brain infarctions in these cases. Diffuse VZV encephalitis is a rare disorder. It may occur in the immunodeficient patients (Leestma 1985), and the white matter may be more severely involved than the grey matter. Affected areas are hyperintense on Т2-weighted MR images and may reflect the infection itself or an immune reaction induced by the infection. Vasculitis may also occur.
11.5.4 Epstein-Barr Virus EBV is a pathogen of infectious mononucleosis, which also causes several peripheral and CNS disorders, such as Guillain-Barré syndrome, meningoencephalitis, transverse myelitis, and chronic fatigue syndrome. All of these may manifest during infectious mononucleosis or when it is absent. CNS complications are seen in about 5% of all patients with infectious mononucleosis. Diffuse encephalitis develops in less than 1% of all affected with brief, but severe clinical course, albeit favourable prognosis for recovery. On Т2-weighted MR images, there are multiple areas of hyperintense signal in the grey matter or in the subcortical white matter (Tolly 1989; Weeks et al. 2006).
11.5.5 Cytomegalovirus Cytomegalovirus infection frequently accompanies AIDS in adults, affecting not only the CNS, but also other systems and
Intracranial Infections
organs. More frequently, CMV disseminates outside of the CNS and affects the respiratory and gastrointestinal tracts, liver, urogenital system, and haemopoietic organs. In the latent form, the virus is present in the majority of individuals in population. Almost 90% of adults have antibodies to CMV (Leestma 1985). Reactivation of the virus leads to mild subclinical infection, manifesting itself as does mononucleosis. In the immunodeficient individuals, reactivation causes dissemination of infection, with severe necrotising meningoencephalitis and ependymitis. CMV may involve peripheral and central nervous system (Wiley 1988). Neurological manifestations of CMV infections are as follows: acute or chronic meningoencephalitis, cranial or peripheral (including brachial plexus) neuropathies, vasculitis, retinitis, and myelitis. In HIV-infected patients, CMV may coexist with other infections, such as toxoplasmosis or cryptococcosis, without clinical manifestations. In almost 15–30% of adults with HIV infection, CMV is found on neuropathological studies. According to literature, the incidence of CMV infection amongst foetuses is 1%. Ten percent of these children have different haemopoietic and neurological disorders, and signs of failure to thrive. A pathognomonic histological feature of CMV infection is “the owl eye”—an enlarged cell with a nucleus, containing eosinophilic viral inclusions encircled by a halo, which contributes to the specific appearance (Post 1986). Presence of the owl eye may be seen in ependymal and endothelial cells, subependymal astrocytes, oligodendroglia, and neurons. Involvement of ependyma is frequent. Less frequently, CMV infection may lead to large destruction of grey and white matter. Another typical histological feature of CMV is delineated nodules of microglia, as well as nuclear inclusions found in the spinal cord, spinal roots and retina. CMV encephalitis is most frequently seen in AIDS patients, in seropositive patients after transplantation of organs, but it can occur in the immunocompetent adults also. Subacute symptoms with fever, confusion, memory loss, and progressive dementia may sometimes develop for several days or a month (Post 1986). Involvement of the brain may be diffuse or limited to subependymal region. CSF tests and complementary blood titres are nonspecific, which makes diagnosis difficult. CT is often ineffective in visualising CMV encephalitis in adults (Post 1986). The most common CT feature is cerebral atrophy; less frequently, it is a hypodensity of the white matter. Taken in a whole, CT underestimates the extent of CNS involvement. Periventricular and subependymal CE may be additionally seen with atrophy and white matter hypodensity, especially if a double enhancement is used with a temporal gap between intravenous injection and the beginning of scanning procedure. MRI is much more sensitive in detection of CMV than CT is. In addition to atrophy, MRI demonstrates hyperintense signal on Т2-weighted MR images in the periventricular white matter, which may be focal or rarely diffuse (Ramsey 1988). Visible subependymal enhancement is an important diagnostic sign. In patients with CMV retinitis, MRI with CE visualises thickening and prominent enhancement within membranes of the eye on FLAIR images. Haemorrhagic retinitis is diagnosed in 20–40% of AIDS patients.
985
In children, CMV is a frequent cause of severe fatal encephalitis, especially in neonates. CMV contamination in utero is a result of transplacental transmission of the virus from mother to child. In 30–40% of primary maternal infection cases, intrauterine contamination does occur. These children are often born prematurely. Only 10% of children with congenital CMV infection are symptomatic right after birth and have decreased platelet count, chorioretinitis, and hepatosplenomegaly. In 50–75% of children with CMV infection, signs of microcephaly develop. Intrauterine contamination with CMV may lead to intracranial necrosis of brain tissue and hydrocephalus. According to the literature, the incidence of CMV infection of foetus is 1%. Clinical manifestations of CMV infection are directly connected with timing and the extent of changes in the brain and usually start to manifest during the first year of life. The symptoms are microcephaly, epilepsy, and mental retardation. Diagnosis of CMV is based on X-ray craniography, CT and MRI. On X-ray craniograms, many calcifications of various size and shape are found in brain structures. CT and MRI give a more complete picture of the extent of cerebral involvement: calcified lesions better seen on CT are found in the walls of the lateral ventricles, and the number of calcifications as well as the extent of ventricular dilatation is much higher if the contamination occurred within the first 3 months of intrauterine life. In these cases, MRI finds lissencephaly, cerebellar hypoplasia, and marked ventriculomegaly. If the contamination occurred later, then CT and MRI reveal less severe changes in the brain parenchyma and the ventricular system (Fig. 11.43). However, petrificates in the periventricular area (mineralisation angiopathy) and cystic encephalomalacia may be seen in other infectious disorders (for instance, in herpes simplex, varicella or toxoplasmosis).
11.5.6 Human Retroviruses Human retroviruses that cause neurological disorders include HIV and human T-lymphocyte virus type I (НTLV-I). In HIV (a lentivirus) there are two subtypes: HIV-I (initially known as НTLV-I) and HIV-2. HIV-1 is found in all continents, and HIV-2 is found predominantly in Africa. НTLV-I infection is endemic in southern Japan, Caribbean countries, and several regions of Africa and Southern America, but it may be encountered in North America (Rosenblatt 1988; Atlas 2002). HIV infection is a severe disorder with progressive course and involvement of all vital organs and systems. The immune system is the first-line target of this infection, and its involvement causes the immune deficiency syndrome. When the virus enters a human host, the T-helper population of lymphocytes is primarily affected. Monocytes, scavenger cells, and neuroglial cells are also affected. On pathological studies of the CNS, HIV-1 or the viral RNA are found in 90% of adults and children with AIDS. However, immune deficiency leads to activation of endogenous conditionally pathogenic flora of human organism (herpes virus, Candida), as well as to increased sensitivity
986
Chapter 11 Fig. 11.43a,b Congenital cytomegalovirus infection. CT of a 5-year-old child. Subependymal foci of calcification in the walls of the lateral ventricles and hypodensive signal in the adjacent brain tissue are seen
to exogenous pathogens (cryptococci, CMV, toxoplasmosis, etc.). More than in a third of all affected individuals do brain (lymphomas) and skin tumours (lymphomas and Kaposi’s sarcoma) develop. CNS involvement in patients with HIV infection is divided into two basic groups: (1) primary involvement directly connected with AIDS, which often manifest as encephalopathy, myelopathy, peripheral neuropathy and myopathy, and (2) secondary involvement caused by additional factors such as activation of opportunistic infection, brain tumours, and metabolic and vascular disorders (Yakhno and Shtulman 2003). Table 11.6 summarises the most frequently seen types of CNS involvement connected with HIV infection. The most common neurological complication in AIDS patients is subacute encephalitis. It is found on autopsy in 28%
of adult patients. Its clinical manifestations are progressive dementia with motor and behavioural dysfunctions. First signs of memory and concentration impairment are followed by apathy and social alienation, which can be wrongly considered as symptoms of depression. Headache is a frequent sign and almost in 10% of cases, epileptic seizures are observed. It was shown that the pathological correlate of HIV encephalitis is involvement of myelin by HIV-infected giant multinuclear cells, proliferation of microglia, gliosis, and degeneration. In patients with AIDS–dementia complex subacute encephalitis with giant multinuclear cells, but not the formation of microglial nodes, is a pathological correlate. Electronic microscopy detects retroviral particles inside the giant multinuclear cells and their presence correlates with AIDS–dementia complex manifestations. Diffuse atrophy is usually seen (as reported by
Table 11.6 CNS disorders that accompany HIV infection Involvement
Disorders
Primary involvement
Meningitis (acute, chronic, remitting-relapsing) Encephalopathy (AIDS-dementia complex) Vascular myelopathy
Secondary involvement (opportunistic infection)
Cytomegalovirus Toxoplasmosis Cryptococcosis Progressive multifocal encephalopathy Herpes encephalitis Candidosis Histoplasmosis Tuberculosis (and atypical mycobacterial infection) Aspergillosis
Tumours
Primary CNS lymphoma Kaposi’s sarcoma
Vascular lesions
Secondary haemorrhagic thrombocytopenia Vasculitis and brain infarction
Metabolic and nutritional disorders
Wernicke’s encephalopathy Vitamin В12 deficiency
Post-therapeutic complications
Secondary peripheral neuropathy Secondary metabolic myopathy
Intracranial Infections
most authors). Initially the disorder develops in the white matter and distributes to basal ganglia and cortex as the disease progresses. White or grey matter involvement may predominate in individual patients. Lesions may be located in brainstem, cerebellum, and the spinal cord (Navia and Gonzales 1986; Sze et al. 1987; Whiteman et al. 2002; Osborn 2004). The main aetiological factor of spinal cord involvement in AIDS is a vacuolar myelopathy, which is seen in up to 25% of cases according to autopsy data. Demyelinating lesions are a secondary feature of retroviral infection, and they are a relatively late finding. Small, hardly visible lesions are patched in the total picture of myelin involvement. In addition, HIV infection may lead to acute encephalitides as well as to acute or chronic meningitides. Viral meningitides are represented by lymphocyte infiltration of meninges and are accompanied by fever, headache, and meningeal signs. Neuroimaging is usually negative. In patients with subacute encephalitis, CT usually reveals brain atrophy. White matter involvement is rarely seen on CT in patients with HIV encephalopathy. In some cases, CT is negative, if even MRI shows diffuse white matter changes. The clinical diagnosis of HIV encephalopathy usually precedes neuroimaging findings. MRI is superior to CT in detection of CNS involvement. Frequent findings are atrophy and hydrocephalus. Usually, these are the first signs. Follow-up MRI shows progression of cortical and subcortical atrophy. Hyperintense lesions without mass effect may be seen on Т2-weighted MR images. They are located in the periventricular white matter and centrum semiovale, corresponding to foci of demyelination and vacuolation. These foci are not enhanced after IV contrast administration. Solitary and diffuse unilateral lesions as well as large bilateral lesions with MR signal change may be seen. White matter involvement is better revealed on FLAIR MR images. Despite the fact that MRI shows signal changes in the white matter, it does not detect giant multinuclear cells or microglial nodules, which are found on histology. It is not yet elucidated whether diffuse changes of signal in the periventricular white matter confirm HIV encephalitis in contrast to multifocal changes in multifocal leukoencephalopathy. Variability of size, distribution, and topography in HIV demyelination as well as in leukoencephalopathy, especially on early stages of the diseases, permits diagnosis with MRI only. HIV demyelinating lesions are more symmetrical and centrally located in comparison with progressive multifocal leukoencephalopathy (PML). Despite the fact that lesions shown on T2-weighted MR images are in any case hyperintense, areas of HIV demyelination are not discernible on Т1-weighted MR images, whereas demyelination lesions in PML are hypointense and clear-cut. The clinical picture plays a crucial role in diagnosis, as HIV encephalitis is frequently manifested by global encephalopathy, and PML—by a focal neurological deficit. Therapy of AIDS patients has markedly improved during the last years. On MRI in patients who undergo therapy initially, signs of progression of white matter involvement are
987
seen soon after therapy; however, later regression is obvious (Thurnher 2000). MRS became a valuable tool for diagnosis of HIV infection. It was shown in several studies that the NAA–Cr ratio is significantly lower in AIDS patients, and the extent of its reduction correlates with progression of the clinical picture (Jarvik 1993). The average Cho–Cr ratio is also markedly decreased in this patient group. MR spectra of healthy controls and patients were compared in a blindfold manner, and all spectra of healthy people were considered normal, and 80% of the AIDS patients spectra were considered abnormal. However, MRI failed to show any differences between the patients and the control group. That allows presuming that MRS may reveal impairment of cerebral metabolism before the underlying pathology is visualised by standard techniques, i.e. MRS is a technique for early biochemical diagnosis of white matter involvement in HIV-infected individuals. Thus, MRS reveals (1) reduction of NAA content in those brain regions that appear absolutely normal on standard MRI, and NAA content correlates with progression of clinical picture (after therapy the level of NAA increases); (2) increase of the Cho peak, which occurs earlier than reduction of the NAA peak on early as well as on late stages of HIV-associated dementia; and (3) increase of mI peak on early stages of the disease (Laubenberger 1996; Navia 1997).
11.5.7 Human Т-Lymphocyte Virus Type 1 HTLV-1 differs from HIV in its origin and pathogenicity. This virus is thought associated with Т-cell leukaemia/lymphoma, and it is thought to cause tropical spastic paraparesis (ТSP) and the associated tropical myelopathy (ТМ) (Whiteman et al. 2002). The clinical picture of this infection mildly resembles multiple sclerosis, but TSP and TM are separate nosological entities, the aetiology of which is identified by epidemiological studies and serology. TM and TSP are manifested by the progressive paraparesis, mild sensory abnormalities, and urinary urgency. Autopsy shows spinal cord involvement, especially at the truncal level, where inflammatory changes, axonal degeneration, and demyelination are found. Widespread chronic meningoencephalomyelitis with inflammatory changes is revealed. Inflammatory changes involve cerebral meninges, brainstem, and supra- and infratentorial white matter. In addition, there are signs of vasculitis such as thickening of external and middle layers of walls of the arteries that pass through the subarachnoid space (Akizuki 1987). Т2-weighted MR imaging shows dot-like or small nodular hyperintense lesions, without mass effect in the periventricular and subcortical white matter in about 50% of patients. These findings are not specific and should be differentiated with such white matter disorders as multiple sclerosis, Lyme disease, HIV demyelination, ischaemia, and vasculitis. The lesions do not show CE. Follow-up scans reveal enumeration of the affected white matter areas in patients (Hara 1988).
988
11.6 Parasitogenic Disorders Parasitism as a concept is a universal ecologic phenomenon that represents one of the forms of relationships between species. The term parasite originates from Latin words para “beside” and sitos “food”. From the Greek term parasitos “person who eats at the table of another,” according to definition, parasitism is an antagonistic symbiosis, in which organism of one species settles in or on the organism of another species and utilises it as a source of habitation and nutrition, causing harm to the latter (Zayats 2002). True (for instance, intestinal helminthes etc.) pseudoparasites and hyperparasites (for instance, bacteria in protozoa) are distinguished. There exist different routes of invasion of a parasite into a host organism: • Alimentary route—eggs of helminthes, cysts of protozoa, larvae of helminthes (Trichinella), autonomous form of protozoa (Toxoplasma) • Air-droplet route—viruses (influenza) and bacteria (diptheria, plague) and several protozoa (Toxoplasma) • Contact route—eggs of contact helminthes, many arthropodia (Lice, etc.) • Transmissive route—if an arthropod carrier participates (plasmodium of malaria, tripanosoma, plague) • Transplacentary route—Toxoplasma, plasmodium of malaria • Percutaneous (Schistosoma), venereal (HIV, Trichomonada) • Transfusional route—(HIV, plasmodium of malaria, tripanosoma) and when non-sterile medical materials and instruments are used (HIV, Trichomonada) (Zayats et al. 2002) Invasion of a parasitic pathogen into a human organism leads to a disorder called parasitosis. Parasitoses are subdivided into several groups (Table 11.7). Each of the recited diseases pass through certain stages, but the main peculiarity of many of them reflected in this section of the book is CNS involvement to more or less extent depending on the type of pathogen.
11.6.1 Malaria Malaria is the most wide-spread parasitogenic disease caused by four species of protozoa from the order of Plasmodium. They are transmitted to humans by female Anopheles mosqui-
Chapter 11
toes. CNS involvement (the so-called cerebral form of the disease) is the most frequent and severe complications of tropical malaria (caused by Plasmodium falciparum). Plasmodia enters the CNS with infected erythrocytes and causes occlusion of cerebral capillaries with possible brain oedema, infarctions, and microhaemorrhages. Focal hyperintensities may be seen on T2-weighted MR images in the subcortical structures and cerebellum (Osborn 2004).
11.6.2 Toxoplasmosis Contamination with toxoplasmosis in most cases happens after consumption of raw meat containing cysts of Toxoplasma gondii. Contamination may also occur via excrement, raw milk, blood transfusion, transplantation of organs, usage of non-sterile needles, via cat excrement, or in utero. The pathogen is ubiquitously distributed. Antibodies to Toxoplasma are present in 6–90% of people in different geographic regions, and 30% of people worldwide are invaded. Gastrointestinal organs mainly serve as a gate for invasion. Later, trophozoits (and autonomous stage) enter the cells of many viscera causing inflammation. Invasion is subclinical in the immunocompetent patients or may by accompanied by lymphadenopathy, skin rash, myalgia, arthralgia, and pneumonia with or without fever. In the immunodeficient, cysts (encapsulated accumulations of trophozoits) rupture with release of free trophozoits, which start to affect adjacent cells. In severe acquired toxoplasmosis, signs of anaemia, mucosal haemorrhages, dilatation of heart chambers, pneumonia and lung oedema, necrotic lesions in liver and spleen, and lymphadenopathy are seen. In the intrauterine route of invasion, foetus death within the first months of pregnancy and spontaneous abortions occur. In cases of contamination in later periods, impairment of brain development occurs. Congenital toxoplasmosis accounts for about 1 case per 3,000 neonates. Toxoplasmosis manifests as mild diffuse encephalitis and/or meningitis. Inflammatory nodules (which later become calcified) are located in ependyma of the lateral ventricles and meninges, which leads to hydrocephalus. Clinical picture resembles that of CMV. The earlier invasion occurs, the more severe are neurological deficits such as microcephaly, hydrocephalus, epilepsy, tetra- or diplegia, and blindness. Clinical manifestations оf acute toxoplasmosis with encephalitis are relatively infrequent. More frequently, toxoplasms af-
Table 11.7 Systemic groups of parasites and human disorders they cause (Belyakov et al. 1989) Realms and groups of parasites
Groups of disorders
Viruses
Infections
Procaryotes (Mycoplasmae, Chlamidiae, Ricketsiae, bacteria, Spirochetae)
Infections
Eucaryotes (fungi)
Mycoses
Eucaryotes (protozoa and helminthes)
Invasions
Eucaryotes (arthropods)
Infestations
Intracranial Infections
fect viscera and other organs (brain, lungs) in AIDS patients. Before the AIDS era, necrotising encephalitides caused by toxoplasms were seen only in patients with marked immune deficiency (in cancer patients, after transplantation of organs of irradiation therapy). If treatment is not timely in AIDS patients, then toxoplasmic encephalitis leads to progressive and fatal brain destruction. Toxoplasmic encephalitis is the most widespread opportunistic brain invasion in ALDS patients. On autopsy, it is seen in 10–34% of adults with AIDS. Early neuroimaging diagnosis mediates early treatment start. On CT without CE, toxoplasmic encephalitides have a characteristic features such as multiple iso- or hypodense areas located predominantly in basal ganglia (76–88%) and in the cortical and subcortical layers. Posterior fossa may be involved. Haemorrhages are very rare. Sizes of mass lesions vary from less than 1 cm to over than 3 cm. Oedema and mass effect of variable extent are present (Osborn 2004). Postcontrast CT shows ring-shaped and nodular enhancement. Ring-shaped enhancement with central hypodensity is a common feature. The rim of enhancement is usually thin and smooth, but in large lesions, thick and uneven rims may be seen (Post 1983). To detect such lesions, double CE is effective. Double-dose CE and delay of scanning may lead to maximal enhancement of a lesion as initial ring-shaped rim enhancement the central part also becomes enhanced. Neuroimaging findings correlate with pathological ones: the central hypodense part corresponds to nonvascular coagulation necrosis. Enhancing rim corresponds to the zone of intense inflammatory reaction, and the area of oedema is located peripherally. Pathological and neuroimaging correlations attests to the fact that distribution of pathological tissue changes in this infection exceeds the area of CE on CT (Post 1983).
989
MRI with CE is more sensitive in detection of novel as well as old lesions of toxoplasmic encephalitis than CT before and after CE. On T2-weighted MRI, active lesions have variable signal. They may be more hyperintense than the brain tissue is and indistinguishable from the hyperintense area of oedema. An iso- or hypointense lesion may be seen in the centre, encircled by a hyperintense area of oedema. In the latter case, this is the bull’s-eye phenomenon; however, it is not specific for toxoplasmosis. On Т1-weighted MR images, the lesion signal is iso- or hypointense (Fig. 11.44). After gadolinium contrast administration ring-shaped or nodular enhancement in the active zone is seen, which clearly differs from the hypointense oedema (Figs. 11.45, 11.46). The pictures of CE on MR and CT are identical. Haemorrhages are very rare in toxoplasmosis. MRI is more sensitive than CT is, especially in detection of small subcortical white mater lesions. Toxoplasmosis frequently affects basal ganglia and lesions are usually multiple (Fig. 11.47); only in 14% of patients with toxoplasmic encephalitis are solitary lesions seen. Due to higher sensitivity, MRI reveals more lesions than CT does (Porter 1993). After specific treatment of toxoplasmic encephalitis, follow-up CT and MRI show that number and size of lesions reduces, as well as oedema and mass effect. These changes occur 2–4 weeks after treatment, and 6 months after treatment complete recovery may ensue. Treated lesions have different density on CT. Calcifications, if present, may be dot-like or large and quite thick (Fig. 11.48). Encephalomalacy areas may form. On MRI, petrified lesions appear as areas of hypointense signal on Т1and Т2-weighted MR images and are more visible on gradient echo pulse sequence images. In the past, a biopsy of an enhanced lesion was made for diagnostic purposes. Nowadays, when toxoplasmosis is widely distributed among AIDS patients, if typical clinical and neuroimaging findings are pres-
Fig. 11.44a–c Toxoplasmic encephalitis in a HIV-infected patient. T2-weighted imaging (a) and T1-weighted imaging in axial (b) and coronal (c) projections demonstrate an extensive area of MR signal change in the right basal ganglia. Mass effect and perifocal oedema are prominent. The brainstem is also involved
990
Fig. 11.45a–d Toxoplasmic encephalitis in an HIV-infected patient. MRI in T2 (a), FLAIR (b), and T1 sequences (c): an area of heterogeneous MR signal changes is seen in the left thalamus. After intravenous contrast medium injection (d), the site of annular enhancement in the centre of the area is observed
Chapter 11
Intracranial Infections
Fig. 11.46a–i Toxoplasmosis in an HIV-infected patient. T2-weighted imaging (a,b) and T1-weighted imaging with CE (c–f) show multiple sites of MR signal change and prominent contrast accumulation—the bull’s-eye phenomenon. In the upper series of MRI scans, an annular lesion is visualised in the right cerebellar hemisphere, resembling an
991
abscess. DWI (g) doesn’t confirm presence of the purulent content in the centre of the lesion. MRS (h,i) taken from the area of central necrosis: a high Lip–Lac complex on the background of reduction of other metabolite peaks is obtained
992
Chapter 11 Fig. 11.47a,b Toxoplasmosis in a 1.5-month-old child. There is obstructive hydrocephalus (at the level of Magendie foramina) and prominent dilatation of the entire ventricular system. The fourth ventricle is round. In the wall of right lateral ventricle, a calcified node (arrow) is seen on MRI (a,b)
Fig. 11.48a–d Toxoplasmosis in a 7-year-old child. CT (a,b)—calcifications in the walls of the lateral ventricles and the brain tissue, hydrocephalus were observed. T2-weighted imaging (c) and T1-weighted imaging (d) also demonstrate the sites of MR signal increase from periventricular brain tissue. Calcifications are almost invisible
Intracranial Infections
ent, the patient is at once administered specific treatment, and 10 days to 2 weeks later a control CT or MRI is performed. Gradual improvement confirms the diagnosis of toxoplasmic encephalitis.
11.6.3 Cysticercosis Cysticercosis is a frequent and ubiquitously observed CNS invasion. In endemic regions, it is seen in immunodeficient as well as in immunocompetent patients. Mexico, Central and South Americas, India, China, Eastern Europe, Africa, Asia, and Portugal are endemic regions for cysticercosis. The pathogen is the larvae form of Taenia solium. Contamination occurs via alimentary route after swallowing larvae. If contaminated, then a human organism becomes a host for a full life cycle of the parasite. In the intestine, larvae develop in tapeworms 1–8 m long. Tapeworms themselves do not cause any symptoms but release many eggs, which are found in faeces and the intestine. The external membrane of an egg dissolves in the intestine, releasing an oncosphere. These oncospheres or primary larvae migrates through the intestine walls into blood and in 60–95% of cases, affect brain tissue via haematogenic dissemination. Intracranially oncospheres are located in the brain tissue, meninges, ependyma, and choroid plexus. Spinal cord lesions are rarely seen: meninges and subarachnoid space are predominantly involved (Hawk et al. 2005). Cysticercosis may affect retina, skeletal muscles, heart, and subcutaneous tissues (Davis and Kornfeld 1991). Four types of CNS involvement in cysticercosis are distinguished: parenchymal, subarachnoid, intraventricular, and mixed forms. The parenchymal form is the most frequent. In the stage of primary invasion by larvae, the disease is usually asymptomatic, and only small lesions with oedema may be visualised on neuroimaging. In the next stage, larvae and cysticercus develop into cysts. Formed cysts may be revealed in the brain tissue only 2–3 months after eggs were ingested (Davis and Kornfeld 1991). This stage is also usually asymptomatic. The size of cyst varies from 3 to 18 mm in diameter, and it contains scolex (a head of a tapeworm). If the parasite is alive, then minimal inflammation is seen around the cyst, which may be preserved 2–6 years after contamination. As the parasite dies, antigens and products of metabolism are released through the walls of cyst into the surrounding brain tissue, causing visible inflammatory reaction, oedema, and mass oedema. Clinical manifestation of CNS involvement appears at this stage (seizures and focal neurological deficits). Earlier transparent liquid in cysts becomes turbid and gel-like. Then cysts collapse, degenerate, and petrify. If entering meninges or choroid plexus, the infection may affect the ventricular system and the subarachnoid space. Subarachnoid cysts may be multiple, resembling grapes 5 mm–9 cm in size. Scolexes are absent inside these forms. Chronic meningitis or ventriculitis usually develop. Grapelike cysts may cause obstructive hydrocephalus. In endemic regions, contamination may occur many times, and intracra-
993
nial cysts may be on different stages of maturation. Too, several lesions may resolve slower than others, which also leads to detection of different stages of the disease in an individual patient. The characteristic neuroimaging picture of cysticercosis allows making a diagnosis. It should be mentioned that a parasite progresses through several stages of development, each of which have their histological and diagnostic equivalents (Escobar 1983). In the initial vesicular stage, multiple small lesions are found, hypodense on CT, and hyperintense on Т2- and hypointense on Т1-weighted MR images. These lesions do not usually accumulate contrast medium and have no cystic component and may not be visualised at all (Hawk 2005). Later, during the following several weeks, a cyst forms 1–2 cm in diameter, which is well detected on CT and MRI. Cysts may lay on borders of grey and white matter, as well as in basal ganglia, brainstem, and cerebellum. Surrounding oedema is mild or absent. The walls of cyst are thin and smooth. Protoscolexes appear as lesions better seen on MRI than CT (Fig. 11.49). Vivid signal on Т2-weighted MR images of CSF may mask scolexes, which is why they are better visualised on proton density–weighted or FLAIR images. In this stage, the walls of the cyst may show CE. On MRI, cysts are isointense to CSF in all sequences and have CSF density on CT. MRI reveals more viable cysts than CT does. Five to 7 years later, a larva of cysticercus start to degenerate and dies (the colloid–vesicular stage), and inflammatory reaction develops around the parasite with formation of fibrous capsule. Protein content in the cystic fluid increases. As a result, cysts on MRI become mildly hyperintense on Т1- and vivid on Т2-weighted MR images. Scolex inside the cyst is well visualised on the background of hyperintense signal on Т2weighted MR images of the cyst content. During the granularnodular stage, resorption of fluid from the cyst cavity occurs (a dying parasite), a capsule thickens, and a granulomatous node forms, which shows ring-shaped or homogenous CE. In the final stages, mineralisation (calcification) of the node occurs (Fig. 11.50). Granulomatous nodes are replaced by gliosis with subsequent petrification, which is visualised on CT, but is also visible on Т2-weighted MR images as a small hypointense signal, and is better visible on gradient echo pulse sequence. On CT intraventricular and subarachnoid cysts are difficult to identify in many cases, as they are isodense to CSF. If the subarachnoid cysts do not enhance, then intraventricular cysts may enhance and are better seen on MRI, especially if it is taken into account that in cysticercosis they are predominantly located in the fourth ventricle and frequently cause hydrocephalus (Fig. 11.51). The most frequent sites of location of cysts are the subarachnoid space of the cerebellopontine angle and the suprasellar cisterns. Borders of these subarachnoid cysts are sometimes difficult to assess even on MRI. Focal dilatation of CSF spaces and inflammatory reaction in the adjacent brain tissue may be diagnostic signs. Due to chronic meningitis caused by parasitic invasion, open hydrocephalus may form, and MRI shows CE along meninges in basal cisterns. Standard X-ray study of extremities should be made, in
994
Chapter 11
Fig. 11.49a–f Cerebral cysticercosis. T2-weighted imaging (a–c) and T1-weighted imaging (d–f) show small multiple cysts, settled on the convex surface of the brain hemisphere. The mural scolex of the parasite is indicated by arrows
Fig. 11.50 Cerebral cysticercosis. CT without CE detects multiple calcifications in the cerebral meninges, brain tissue, and the lateral ventricle walls
Intracranial Infections
995
Fig. 11.51a–d Cysticercosis in an 8-year-old child. Standard CT after the first surgery (a): a multistage cystic formation with clear borders in the right cerebellar hemisphere. The fourth ventricle is compressed and removed forwards. b CT with CE: the density of the lesion borders increased minimally. c,d T1- and T2-weighted imaging: polycystic mass lesion has a signal identical to that of CSF, and clear-cut borders
which calcifications in skeletal muscles are usually revealed (Fig. 11.52). Diagnosis of cysticercosis is based on the results of clinical, imaging, and serological tests. Intraventricular cysts may require surgical intervention (shunting) if the ventricles are occluded.
11.6.4 Amoebiasis Several types of amoeba may invade CNS. They are Entamoebа histolytica, Naegleria fowleri, and Acanthamoeba, which are most frequently seen. Contamination occurs during the contact with infected water. Entamoebа histolytica. Southern regions of the United States, South America, South-Eastern Asia, and Africa are endemic for this parasitogenic disease (Osborn 2004). CNS infection occurs after the contaminated water enters the intestine, and then infection is spread via the haematogenic route. Liver abscesses frequently develop in the affected individuals. Clinical signs are nonspecific: headache, nausea, somnolence, seizures, meningeal signs, and sopor. CSF tests are not spe-
cific. Prognosis is unfavourable if treatment is not started a timely fashion. CT and MRI data are scanty in patients with amoebiasis. CT reveals solitary or multiple lesions with ring-shaped CE (Dietz 1991). MRI may also detect multiple enhancing lesions (Singh et al. 2006). Such an infection may be suspected in patients with multiple brain and liver abscesses, who may have been exposed during visits to endemic regions (tourists). Naegleria fowleri is a pathogen that causes primary amoeba encephalitis in healthy individuals. The N. fowleri protozoa lives in lakes, ponds, and soil. It is a rare, fatal infection that affects males twice more often than it does females. Immunocompetent individuals and often children are affected. Amoebae enter the CNS via ethmoidal lamina during bathing, spread into the anterior cranial fossa and into the brain, and then may disseminate via perivascular channels. Clinical signs are as those in bacterial meningitis: headache and seizures, with progression to spoor and coma. Diffuse, purulent exudates especially on the bottom of the anterior cranial fossa (the site of primary invasion), is found in patients with primary amoeba encephalitis. Necrosis of brain tissue may occur in the frontal and the temporal lobes. Meningeal
996
Chapter 11 Fig. 11.52a–f Neurocysticercosis. Series of CT scans without CE (a–e): many hyperdense areas are found, which are spread throughout the brain tissue, subependymal regions, and convex cerebral surfaces. Separate areas are calcified. X-ray examination of the upper limb skeletal muscles revealed (f) solitary calcifications (arrows)
Intracranial Infections
997 Fig. 11.53a,b Echinococcosis of the right parietal region. CT scan (a) demonstrates a homogenously hypodense solitary cystic lesion with clear cut round walls. T1-weighted imaging (b) in the sagittal projection—the content of the cyst is isointense to CSF in the lateral ventricles
haemorrhages are seen. CE of basal cisterns and meninges was seen in solitary cases.
11.6.5 Echinococcosis Echinococcosis of the brain is caused by the slowly growing Echinococcus granulosus. Filial vesicles may form within a primary vesicle, which may grow not inside, but also outside of the maternal vesicle increasing its volume. Echinococcus is endemic in the Middle East, Southern America, Australia, and Mediterranean countries. Even in endemic regions, echinococcosis (hydatid disease) is rarely seen in only in 2% of all intracranial mass lesions. Echinococcus is a tapeworm that lives in the intestine of vertebrates. Lambs or humans may be intermediate hosts. The life cycle of the parasite usually begins with excretion of eggs with host faeces, which may enter the intestine of the intermediate host. There the parasite penetrates the intestine walls and disseminates throughout the organism via venous channels and lymphatic vessels (Zayats et al. 2002). The pathogen frequently accumulates in liver or lungs, and the brain may be the terminal organ. Intracranially the parasites form gradually increasing
cysts. Echinococcus multilocularis may also infect the brain, forming small flocculi of cysts, which are called alveoles. On CT, Echinococcus is detected as a clear–cut, round hypodensive area (equal to CSF density). CE does not change the picture. The extent of ventricular system deformity depends on the size of Echinococcus (Fig. 11.53). Multiple cysts are usually small, united in a common lesion, and frequently disseminating along the subarachnoid spaces and the ventricular system (Figs. 11.54–11.56). With time, such lesions located near the internal surface of skull base may cause bone erosion (Demir 1991). Calcification of hooks or walls of dead parasites is seen predominantly in adults and is due to caustic salts accumulation (rarely seen in children). On MRI, echinococcal cysts are mildly more hyperintense than is the grey matter on proton density–weighted images, and are isointense to CSF on Т2-weighted MR images. Cysts are usually more hyperintense than CSF on Т1-weighted MR images. Oedema is usually absent. Accumulation of contrast medium is rarely seen on the cyst periphery, probably due to local inflammatory granulomatous process around a capsule. Mild mass effect is seen. Haemorrhages into the echinococcal cyst cavity are quite a rare phenomenon, but it is possible (Fig. 11.57).
998
Fig. 11.54a–i Echinococcosis in a 10-year-old child. Series of CT scans (a–c): clearly delineated multiple cystic lesions located in the subarachnoid space and along the ventricular system accompanied with hydrocephalus. T2-weighted imaging (d–h) demonstrates a
Chapter 11
small number of cysts with multiple filial vesicles, filling in the right lateral, and the third and the fourth ventricles. T1-weighted imaging (i) gives additional information about lesion distribution
Intracranial Infections
999
Fig. 11.55a–c Echinococcosis of the posterior frontoparietal area. T2-weighted imaging (a,b) and T1-weighted imaging in the sagittal projec-
tion (c) visualise a cystic lesion, consisting of two cavities with different signal on T1-weighted imaging
Fig. 11.56a–f Echinococcosis of the left temporal region (of a multi-
lobar structure). On T2-weighted imaging (a) and T1-weighted imaging before (b) and after (c,d) CE, a cystic lesion is visualised, consisting of multiple cysts (in a shape of a cluster of grapes—flocculus). Walls of several cysts accumulate contrast. On DWI (e), cysts are
hypointense. 1H MRS spectrum (f), taken from the central part of a cyst encompassing the cystic and capsular portions of Echinococcus—a high succinate (Suc), alanine (Ala), and Lip–Lac complex peaks (Lac). The NAA peak is markedly reduced
1000
Chapter 11
Fig. 11.57a–d Echinococcosis of the right posterior frontoparietal region. On T2-weighted imaging (a,b), FLAIR (c) and T1-weighted imaging (d), a ring-shaped structure with hypointense capsule and high MR signal in all regimes due to the intracystic haemorrhage is seen
Refere n c e s Akzuki S, Nakazato O, Higuichi Y et al (1987) Necropsy findings in HTML-1 associated myelopathy. Lancet 1:156–157
Bhatia R, Tandon P, Banerji A (1973) Brain abscess: an analysis of 55 cases. Int Surg 58:565–568
Atlas S (2002) MRI of the brain and spine, 3rd edn. Lippincott Williams & Wilkins, Philadelphia, pp 1099–1173
Burtscher I, Holtas S (1999) In vivo proton MR spectroscopy of untreated and treated brain abscesses. AJNR Am J Neuroradiol 20:1049–1053
Aviv R, Benseler S, Silverman E et al (2006) MR imaging and angiography of primary CNS vasculitis of childhood. AJNR Am J Neuroradiol 27:192–199 Bale J, Morph J (1992) Congenital infections and the vervous system. Pediatr Clin North Am 39:669–690 Barkovich A (2000) Pediatric neuroimaging, 3rd edn. Lippincott Williams & Wilkins, Philadelphia, p 850 Barnes P, Poussaint T, Burrows P (1994) Imaging of pediatric central nervous system infections. Neuroimaging Clin N Am 4:2:367–391 Belyakov V, Iafaev R (1989) [Epidemiology.] Medicine, Moscow (in Russian) Bernaerts A, Vanhoenacker F, Parizel P et al (2003) Tuberculosis of the CNS: overview of neuroradiological findings. Eur Radiol 13:1876–1890
Carcia-Monco J (1999) Central nervous system tuberculosis. Neurol Clin 17:737–759 Cho S Lee D, Hong S, Oh W (2007) Intracranial aspergillosis involving the internal auditory canal and inner ear in an immunocompetent patient. AJNR Am J Neuroradiol 28:38–140 Dastur D, Manghani D, Udani P (1995) Pathology and pathogenetic mechanisms in neurotuberculosis. Radiol Clin North Am 33:733–752 Davenport C, Dillon W, Sze G (1992) Neuroradiology of the immunosupressed state. Radiol Clin North Am 30:611–637 Davis L, Kornfeld M (1991) Neurocysticercosis: neurologic, pathogenic, diagnostic and therapeutic aspects. Eur Neurol 31:229–240 Demir K, Karsli A, Kaya T et al (1991) Cerbaral hydatid cyst: CT findings. Neurology 33:22–24
Intracranial Infections
1001
Dev R, Gupta R, Poptani H et al (1998) Role of in vivo proton magnetic resonance spectroscopy in the diagnosis and management of brain abscesses. Neurosurgery 42:37–42
Lyke K, Obasanjo O, Williams M et al (2001) Ventriculitis complicating use of intraventricular catheters in adult neurosurgical patients. Clin Infect Dis 33:2028–2033
Dietz R, Schanen G, Kramann B et al (1991) Intracranial amebic abscesses: CT and MR findings. J Compu Asisst Tomogr 15:168–170
Lyons R, Andriole V (1986) Fungal infections of the CNS. Neurol Clin 4:159–170
Ebisu T, Tanaka C, Umeda M et al (1996) Discrimination of brain abscess from necrotic or cystic tumors by diffusion-weighted echo planar imaging. Magn Reson Imaging 14:1113–1116 Engin G, Acuna B, Acuna G et al (2000) Imaging of extrapulmonary tuberculosis. Radiographics 20:471–488 Escobar A (1983) The pathology of neurocysticercosis. In: Palacios E, Rodrigues-Carbajal J, Taveras J (eds) Cysticercosis of the CNS. Charles C. Thomas, Springfield, pp 27–54 Gaviani P, Schwartz R, Herley-Whyte E et al (20005) Diffusionweighted imaging of fungal cerebral infection. AJNR Am J Neuroradiol 26:1115–1121 Girard N, Zimmerman RA (2000) Infectious and inflammatory diseases of brain and spinal cord. In: Zimmerman R, Gibby W, Carmody R (eds) Neuroimaging: clinical and physical principles. Springer, Berlin Heidelberg New York, pp 909–950 Hara Y, Takahashi M, Ueno S et al (1988) MRI of the brain in myelopathy associated with human T-cell lymphotropic virus type I. J Comput Assist Tomogr 12:750–754 Hawk M, Shahlaie K, Kim K et al (2005) Neurocysticercosis: a review. Surg Neurol. 63:123–132 Jarvik J, Lenkinski R, Grossman R et al (1993) Proton spectroscopy of HIV-infected patients: characterization of abnormalities with imaging and clinical correlation. Radiology 186:739–744 Jinkins, J Gupta R, Chang K et al (1995) MRI of CNS tuberculosis. Radiol Clin North Am 33:771–786 Jubelt B (1984) Enterovirus and mumps virus infections of the nervous system. Neurol Clin 2:187–207 Kellinghaus C, Schilling M, Ludemann P (2004) Neurosarcoidosis: clinical experience and diagnostic pitfalls. Eur Neurol 51:84–88 Kobayashi G, Fungi D (1980) In: Davis B, Dulbecco R, Eisen H et al (eds) Microbiology. Harper and Row, New York pp 817–850 Konovalov AN, Kornienko VN, Ozerova VI, Pronin IN (2001) [Pediatric neuroradiology.] Antodor, Moscow Kumar R, Jain R, Kaur A et al (2000) Brain stem tuberculosis in children. Br J Neurosurg 14:356–361 Lai P, Kun T, Shu S et al (2005) Pyogenic brain abscess: findings from in vivo 1.5-T and 11.7-T in vitro proton MRS. AJNR Am J Neuroradiol 26:279–288 Laubenberger J, Haussinger D, Bayer S et al (1996) HIV-related metabolic abnormalities in the brain: detection with proton MR spectroscopy with short echo times. Radiology 199:805–810 Leestma J (1985) Viral infections of the nervous system. In: Davis R, Robenson D (eds) Textbook of neuropathology. Williams & Wilkins, Baltimore, pp 704–787 Lexa F, Grossman R (1994) MR of sarcoidosis in the head and spine spectrum of manifestations and radiographic response to steroid therapy. AJNR Am J Neuroradiol 15:973–982 Lobzin Yu, Antonov V, Kozlov S (1996) Lyme disease—tick borreliosis. Medicine, St. Petersburg, p 57 (in Russian)
Mathews V, Alo P, Glass J et al (1992) AIDS-related CNS cryptococcosis: radiologic-pathologic correlation. AJNR Am J Neuroradiol 13:1477–1486 Menon V, Gogoi M, Saxena R (2004) Isolated “one-and-a-half syndrome” with brainstem tuberculoma. Ind J Pediatr 71:469–471 Mirfakharee M, Crofford M, Guinto F et al (1986) VirchowRobin space: a path of spread in neurosarcoidosis. Radiology 158:715–720 Navia B, Gonzalez R (1997) Functional imaging of the AIDS dementia complex and the metabolic pathology of the HIV-1 infected brain. Neuroimag Clin North Am 7:431–445 Osborn A et al (2004) Diagnostic imaging. Brain. Amirsys, Manitoba, SK, p 910 Osenbach R, Loftus C (1992) Diagnosis and management of brain abscesses. Neurosurg Clin North Am 3:403–420 Palmer P (ed) (2002) Tuberculosis of CNS. In: The imaging of tuberculosis. Springer, Berlin Heidelberg New York, pp 125–133 Phuttharak W, Hesslink S, Wixon C (2005) MR features of cerebral aspergillosis in an immunocompetent patient: correlation with histology and elemental analysis. AJNR Am J Neuroradiol 26:835–838 Popovich M, Arthur R, Helmer E (1990) CT of intracranial cryptococcosis. AJNR Am J Neuroradiol 11:139–142 Porter S, Sande V (1993) Toxoplasmosis of the CNS in acquired immunodeficiency syndrome. N Engl J Med 2:1643–1648 Post M, Hoffman T (1984) Cerebral inflammatory disease. Neuroradiology 4:525–594 Pronin I, Kornienko V, Podoprigopa A et al (2002) Complex MR imaging of brain abscesses. J Vopr Neurosurg 1:7–11 (in Russian) Provenzale J, Jinkins J (1997) Brain and spine imaging findings in AIDS patients. Radiol Clin North Am 35:1127–1166 Ramsey R, Geremia G (1988) CNS complications of AIDS: CT and MR findings. AJNR Am J Neuroradiol 151:449–454 Reichman R (1978) Neurological complications of varicella-zoster infections. Herpes zoster varicella infections. Am Intern Med 89:375–388 Rosenblatt J, Chen I, Wachsman W (1988) Infection with HTLV-I and HTLV-II: evolving concepts. Semin Hematol 25:230–246 Schroth G, Gawehn J, Thron A et al (1987) Early diagnosis of herpes simplex encephalitis by MRI. Neurology 37:179–183 Sharma A, Goyal M, Mishra N et al (1997) MRI of tubercular spinal arachnoiditis. Am J Roentgenol 168:807–812 Shaw D, Cohen W (1993) Viral infections of the CNS in children: imaging features. AJR Am J Radiol 160:125–133 Singh P, Kochhar R, Vashishta R et al (2006) Amoebic meningoencephalitis: spectrum of imaging findings. AJNR Am J Neuroradiol 27:1217–1221 Smith J, Matheus M, Castillo M (2004) Imaging manifestations of neurosarcoidosis. AJR Am J Roentgenol 182:289–295 Srikanth S, Taly A, Nagarajan K et al (2007) Clinicoradiological features of tuberculosis meningitis in patients over 50 years of age. J Neurol Neurosurg Psychiatr 78:536–538
1002
Chapter 11
Sze G, Zimmermann R (1988) The MRI of infections and inflammatory diseases. Radiol Clin North Am 26:839–859
Weinman D, Samarasingue H (1972) Subdural empyema. Aust N Z J Surg 41:324–330
Sze G, Brant-Zawadzki M, Norman D et al (1987) The neuroradiology of the AIDS. Semin Roentgenol 22:42–53
Whiteman M, Bowen B, Post M, Bell M (2002) Intracranial infections. In: Atlas W (ed) Intracranial infection in MRI of the brain and spine, 3rd edn. Lippincott Williams & Wilkins, Philadelphia, pp 1099–1175
Thurnher M, Schindler E, Thurnher S et al (2000) Highly active antiretroviral therapy for patients with AIDS dementia complex: effect on MRI findings and clinical course. AJNR Am J Neuroradiol 21:670–678 Tien R, Chu P, Hesselink J et al (1991) Intracranial cryptococcosis in immunocompromised patients: CT and MR findings in 29 cases. AJNR Am J Neuroradiol 12:283–289 Tien R, Feldberg G, Osumi A (1993) Herpes virus infections of the CNS: MR findings. AJNR Am J Neuroradiol 161:167–176 Tolly T, Wells R, Sty J (1989) MR features of fleeting CNS lesions associated with Epstein-Barr infection. J Comput Assist Tomogr 13:665–668 Uysal G, Kose G, Guven A, Diren B, (2001) MRI in diagnosis of childhood central nervous system tuberculosis. Infection 29:148–153 Weeks J, Helton K, Conley M et al (2006) Diffuse CNS vasculopathy with chronic Epstein-Barr virus infection in X-linked lymphoproliferative disease. AJNR Am J Neuroradiol 27:884–886
Wiley C, Nelson J (1988) Role of human immunodeficiency virus and cytomegalovirus in AIDS encephalitis. Ann J Pathol 133:7381 Yakhno N, Schtulmann D (2003) Nervous system disorders. Manual for physicians in 2 vols. vol 1, 3rd edn. Medicine, Moscow, p 744 (in Russian) Zayats R, Rachkovskaya I, Karpov I (2002) Basis of general and medical parasitology. Rostov-na-Donu. Phenix, p 224 (in Russian) Zhuchenko D (1963) Metastatic brain abscesses. Medicine, Moscow, p 251 (in Russian) Zimmenmann R, Bilaniuk L, Sze G (1987) Intracranial infection. In: Brant-Zawadzki M, Norton D (eds) MRI of the central nervous system. Raven, New York, pp 235–257
Chapter 12
12
Toxic and Metabolic Disorders
in collaboration with S. Serkov
12.1 12.2
Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1003 Primary Toxic and Metabolic Encephalopathies .. . . . . . . . . . 1003
12.1 Introduction Characteristics of a heterogeneous group of CNS disorders are given in this chapter, which remain the most complex in terms of clinical neurology as well as of modern neuroimaging. Attention is paid here to disorders that have typical MR features, and to rare disorders, the cases of which are our own, and were observed and verified clinically by laboratory tests and stereotactic biopsy. All toxic and metabolic encephalopathies (TME) at present are subdivided onto primary (hereditary) and secondary (acquired). The first and most abundant group comprises hereditary metabolic disorders with the CNS involvement such as aminoacidopathies, lipidoses, mucolipidoses, mucopolysaccharidosis, mitochondrial disorders, leukodystrophies, and several other hereditary metabolic and storage diseases. The second group comprises acquired endo- and exogenous intoxications that cause secondary involvement of the CNS: drug addiction and CNS involvement due to exo- or endogenous exposure to physical and chemical factors. X-ray craniography is useful in cases when it is necessary to rule out or to reveal developmental abnormalities of cranial bones, as many hereditary metabolic encephalopathies are accompanied by osteodysplasias. CT is used in the diagnosis of TME to reveal calcifications, which frequently serve as an important differential diagnostic sign. The main technique for neuroimaging of this group of disorders is MRI. Т2-weighted imaging and Т2-FLAIR MRI are the most sensitive in detec-
tion of the white matter involvement (oedema, demyelination, gliosis) than is T1-weighted imaging. If metal deposits possessing paramagnetic properties are found in the brain (for instance, manganese-containing substances in ephedrine addiction or copper in Wilson-Konovalov disease), appropriate changes are seen on Т2- as well as on Т1-weighted imaging due to influence of a paramagnetic properties. Congenital TME show no CE except rare pathologies with inflammatory demyelination and impairment of blood–brain barrier (as in adrenoleukodystrophy). Intravenous contrast medium in cases of TME is essential for the differential diagnosis from other disorders, for instance, demyelinating disorders or encephalitis. In secondary acquired TME, administration of contrast medium is justified in order to ascertain damage to BBB and for the differential diagnosis. DWI and MRS play an important role in diagnosis of hereditary and acquired TME. DWI may reveal the ultrastructural changes of the brain parenchyma, including those cases in which Т2-weighted imaging shows only a mild signal changes. Increased diffusion is seen in demyelination when extracellular spaces are enlarged, in primary and secondary destructive lesions, and in degenerative changes in neurons and glia (Engelbrecht et al. 2002). Impairment of diffusion may be due to deposition of pathological or normal substrates in the extracellular and in the intracellular space in storage diseases or chronic intoxications, as well as in cytotoxic oedema (for instance, in mitochondrial disorders) with dwindling of the extracellular spaces size. MRS allows performing a qualitative assessment of ratios of basic metabolites peaks and quantitatively calculating their content in the brain parenchyma (Wang et al. 1998). It is very important in diagnosis of inherited TME, and may be effective in early stages of the disease in which MR findings are absent or scanty. In addition, DWI and to greater degree MRS may serve as a tool for follow-up assessment of the disease course and treatment efficacy.
12.2 Primary Toxic and Metabolic Encephalopathies Aetiology of all forms (hereditary) toxic and metabolic encephalopathies (PTME) is usually linked with a deficit in an
1004
enzyme participating actively or indirectly in the CNS metabolism. In some cases, an enzymatic deficit may cause insufficient myelination of the white matter (myelinopathy), in other, more frequently seen cases, an enzymatic deficiency or the decrease of its activity causes an accumulation of an excessive amount of substrate in the body or CNS, in the metabolism of which this enzyme participates. Abnormal metabolites deposition in the CNS or accumulation of substances normally utilised by in high concentrations leads to toxic and mechanical exposure of these deposits in brain structures, with consequent demyelination, degeneration and atrophy, gliosis, and secondary hydrocephalus. In some cases, the disease pathogenesis is more complex and has multifactorial character, and frequently morphological signs of many processes coincide within a single pathology. As usual, PTME signs manifest in early age, with fluctuations from infancy to adulthood in different pathologies and their forms. Taken as a whole, all pathologies lead to progressive involvement of the CNS with such manifestations as behavioural changes, mental retardation, pyramidal and extrapyramidal deficits, visual and hearing loss, and in some cases, peripheral neuropathy due to peripheral demyelination (Veltishchev and Temin 1998; Теmin and Kazantseva 2001). It is very difficult to classify metabolic encephalopathies. Many classifications have been proposed, and many of them are not perfect and are based on clinical or laboratory signs. Development of modern neurosciences, especially immunohistochemistry and neurogenetics, imposes changes in the position of various nosologies. Moreover, clinical and laboratory techniques are not always specific, diagnosis of certain forms may cause essential difficulties, the biochemical diagnosis is absent for several hereditary disorders with unknown biochemical defects, and, thus, they cannot be classified reliably at the present stage of scientific development. Along with that, the costs for screening biochemical and DNA tests are high, and performance of such examinations require maximal narrowing of the differential diagnosis circle. Facing these aspects and taking into account the relative uselessness of clinical classifications for neuroimaging purposes as well as development of neuroimaging in the past years (implication of DWI, MRS) we represent the actual material in this chapter with an accent on neuroimaging approaches. It is based on modern MR techniques’ ability to ascertain the particular CNS structures affected, which regions of grey or white matter are primarily affected (especially on early stages of the disease), if there a primary or secondary destructive process (demyelination, toxic necrosis), which impairments of white and grey matter exist (cortical abnormalities, myelinopathy), and whether there are depositions of pathological substrates in the brain (paramagnetic metal deposits, toxic substances in metabolic defects). Such an approach that takes into account all the evidence acquired with known typical pathological changes in different disorders and lesions frequently allows a radiologist to perform a correct diagnosis, and if it is impossible, to reduce the circle of the subsequent differential diagnosis essentially. It should be noted that the after MR imaging, diagnosis is the most specific in early stages
Chapter 12
of disease and as disease progresses, the damage becomes diffuse and loses specificity; secondary reparative changes ensue as well as gliosis, atrophy, and hydrocephalus. As a whole, the group of toxic and metabolic encephalopathies is characterised by more expanded and diffuse, frequently bilateral, damage to the CNS structures (van der Knaap et al. 1998) in contrast to focal, unilateral, and asymmetrical lesions inherent in other pathologies, which are described in other chapters of this book. Despite common features, almost each hereditary metabolic disorder is characterised by signs that distinguish it from other disorders within the group. We believe that at present time, the classification of primary metabolic encephalopathies by Barkovich (2000) (with modifications) based on neuroimaging features better corresponds our specialty: 1. Disorders that primary affect grey matter a. Cortical grey matter i. Ceroid lipofuscinoses ii. Mucolipidoses type I b. Deep grey matter i. Prolonged Т2 in striatum 1. Leigh disease 2. MELAS (mitochondrial encephalopathy with lactic acidosis and stroke-like syndrome) 3. Hypoglycaemic encephalopathy (old infants, adolescents and adults) ii. Short T2 in pallidum 1. Hallervorden-Spatz disease iii. Prolonged Т2 in pallidum 1. Methylmalonic academia 2. Bilirubin encephalopathy (kernicterus) 2. Disorders that primary affect white matter a. Early period of the subcortical white matter involvement i. With increased head size 1. Leukoencephalopathy with macrocephaly and mild clinical course (van der Knaap’s disease) 2. Alexander’s disease (involvement of the frontal lobes, decrease of the NAA peak on MRS) 3. Children’s ataxia with diffuse hypomyelination of the CNS (CACH syndrome) ii. With normal head size 1. Galactosaemia, aciduria 2. 4-Hydroxybutyric, also with cerebellar atrophy b. Early period of deep white matter involvement i. Pathological MR signal in thalamus 1. Krabbe’s disease ii. Normal MR signal in thalamus 1. Peroxisomal disorders (specific lesion of pontomedullary pathways) 2. Nonspecific involvement of brainstem pathways a. Metachromatic leukodystrophy b. Phenylketonuria c. Maple syrup disease (involvement of cerebellum and cerebral peduncles) d. Lowe’s disease
Toxic and Metabolic Disorders
e. Hyperhomocysteinemia (5,10-methylentetrahydrofolate reductase deficiency or impairment of cobalamine metabolism) c. Hypomyelination i. Pelizaeus-Merzbacher disease ii. Trichothiodystrophy iii. 18q syndrome (the brief shoulder of the 18th chromosome) d. Nonspecific white mater involvement (diffuse, uni- or bilateral, asymmetrical) i. Hyperglycaemia without ketonemia ii. 3-Hydroxy-3-methylglutaryl coenzyme-А reductase deficiency iii. Carbamid metabolism impairment iv. Late-stage white matter involvement of any cause 3. Disorders with primary involvement of grey and white matter a. Cortical grey matter i. Normal bones 1. Cortical dysplasia a. Fukuyama congenital muscular dystrophy b. Walker-Warburg syndrome c. Muscle-eye-brain disease d. Other congenital muscular dystrophies 2. No cortical dysplasia a. Alper’s disease b. Menkes disease ii. Abnormal bones 1. Mucopolysaccharidoses 2. Lipid storage disorders 3. Peroxisomal disorders b. Deep grey matter i. Primary thalamic involvement 1. Krabbe’s disease 2. GM-2 gangliosidosis 3. GM-1 gangliosidosis ii. Primary involvement of globus pallidus 1. Large NAA peak on MRS, bilateral thalami involvement—Canavan’s disease 2. Kearns-Sayre syndrome 3. Methylmalonic acidaemia 4. Maple syrup disease 5. l-2-Hydroxyglutaric aciduria iii. Primary involvement of striatum 1. Leigh’s disease 2. MELAS 3. Ethylmalonic acidaemia 4. Propionic acidaemia 5. Glutaric aciduria type I (glutaryl coenzyme A dehydrogenase deficiency) 6. Molybdenum cofactor deficiency 7. Mitochondrial ATP synthetase deficiency 8. 3-Methylglutaconic aciduria 9. β-Ketothiolase deficiency 10. Malonic acidaemia 11. α-Ketoglutaric aciduria 12. 3-Ketothiolase deficiency
1005
13. Biotinidase deficiency 14. Cochayne’s syndrome 15. Wilson-Konovalov disease (primary hepatocerebral dystrophy) This classification may essentially help a radiologist informing a physician as to what group of disorders the encountered syndrome should be related. However, it is not complete and lacks many rare, inherited disorders that affect the CNS. Considering a diagnostic case after patient examination, measurement of the patient’s height, head circumference, and inspection facial bones, a radiologist must form a picture of the following: whether the disorder is characterised by primary involvement of the grey, the white matter, or both. The common feature of disorders primarily affecting cortical grey matter is dilatation of cerebral and cerebellar sulci. In disorders primarily affecting deep grey matter (basal ganglia, brainstem, and cerebellar nuclei), CT shows hypodensity within the affected area, and MRI shows prolongation of Т1 and Т2 relaxation times in the acute stage and T1 shortening in the chronic stage. It should be noted that basal ganglia may be affected due to involvement of white as well as of grey matter (as half of basal ganglia is constituted of the white matter). White matter is frequently characterised by abnormal MR signal changes in disorders with primary grey matter involvement, due to Wallerian degeneration of axons, which leads to decrease of white matter volume. It is represented by hypodensity of CT and by mild T2 prolongation on MRI in the white matter. Such a feature is not typical for primary white matter involvement. In disorders with primary white matter involvement marked hypodensity of affected regions on CT occurs, as well as marked prolongation of Т1 and Т2 on MRI in the stage when the decrease of volume (atrophy) of the white matter are still insignificant (van der Knaap 1995; Barkovich 2001). In addition, in disorders with primary white matter involvement, such phenomena as heterotopias, and abnormal sulci and gyri development are not seen, as these features are signs of neuronal migration impairment. These simple differential diagnosis criteria, usually combined with nonspecific clinical signs (seizures and dementia predominance due to involvement of cortical grey matter or signs of deep grey matter involvement—chorea, athetosis, dystonia in contrary to ataxia, hyperreflexia, and spasticity typical for the white matter involvement), distinguish primary white matter disorders from other toxic and metabolic encephalopathies due to primary grey or combined grey and white matter involvement. Then, once the primary white matter involvement is diagnosed, it is necessary to judge what kind of white matter is affected—deep periventricular or white matter within basal ganglia—and whether short, U-shaped associative fibres and brainstem pathways are involved (Barkovich 2000). It is necessary to define whether a patient has isolated signs of cerebral involvement, or if spinal signs are present. Several disorders of that group are presented with combined involvement of the brain and the spinal cord (for instance, Х-linked adrenoleukodystrophy/adrenomyeloneuropathy) or vertebral column involvement is present (as in mucopolysaccaridoses).
1006
In all these cases, additional MR study of the vertebral column and the spinal cord may essentially ascertain the diagnosis. Below we discuss only those metabolic encephalopathies that were observed by the authors in practice and confirmed by laboratory tests and instrumental studies.
12.2.1 Leukodystrophies Leukodystrophies are a large group of genetically determined disorders, with primary white matter involvement of the brain and frequently the spinal cord. Until 1910, only one disease with diffuse white matter involvement was known: periaxial encephalitis, or, Schilder’s disease, later related to the group of demyelinating disorders. During subsequent years, the circle of disorders with primary white matter involvement was essentially widened. At present, several leukodystrophies that are distinct pathological entities are known. They were named after the authors who described them, or according to histology and morphology. According to modern concepts of inherited disorders, taking into account that pathologically distinct leukodystrophies are related to different groups of metabolic disorders (for instance, adrenoleukodystrophy is a peroxisomal disorders, metachromatic leukodystrophy and Krabbe’s disease are lysosomal disorders), we adduce the register of basic, known at present disorders without classification, including those few cases of which have just been described: • Globoid cell leukodystrophy (galactosylceramide lipidosis, Krabbe’s disease) • Metachromatic leukodystrophy (including Austin-type) • Pelizaeus-Merzbacher disease (Х-linked spastic paraplegia type II) • Spongiform leukodystrophy (Canavan–van Bogart–Bertrand disease) • Fibrinoid leukodystrophy with Rosenthal fibres (Alexander’s disease) • Х-linked adrenoleukodystrophy and adrenomyeloneuropathy) • Leukodystrophy with trichothiodystrophy • Nondifferentiated ortochromatic sudanophilic leuko dystrophies • Aicardi-Goutières syndrome • Ovarioleukodystrophy • Autosomal dominant leukodystrophy imitating multiple sclerosis • Leukodystrophy with megaloencephaly and subcortical cysts (van der Knaap’s disease) • CACH syndrome • Nasu-Hakola disease (polycystic lipomembranous osteodysplasia with progressive dementia) • Leukoencephalopathy with calcifications and cysts • Leukoencephalopathy with brainstem and spinal cord involvement and high lactate (LBSL)
Chapter 12
12.2.1.1 Х-Linked Adrenoleukodystrophy The disease was firstly described by Haberfeld and Spieler in 1910. Its prevalence varies from 1:20,000 to 1:100,000. It is often inherited as an X-linked recessive trait. The mutant gene was mapped to Xq28 and is found in all patients. The product of the mutant gene is the ALD protein, located in the peroxisomal membrane and partaking in fatty acids transport. The defect of the transporter protein leads to impairment of unsaturated long-chain fatty acids metabolism, increase of their content in blood, and accumulation in tissues and the CNS in toxic concentrations. Toxic action of the long-chain fatty acids, in particular hexacosanoic acid, leads to trigger of inflammatory demyelination in the CNS, as well as to damage to cellular membranes of suprarenal cortical cells and development of clinical picture of the disease (Yakhno and Shtulman 2001; Gusev et al. 2001). At present, six different phenotypes of adrenoleukodystrophy are known: infantile cerebral form, juvenile cerebral form, adrenomyeloneuropathy, adult cerebral form, isolated Addison’s disease, and asymptomatic form. In clinical practice, 80% of patients have cerebral forms of adrenoleukodystrophy and adrenomyeloneuropathy (predominant changes in the spinal cord with minimal cerebral involvement). Clinical manifestations depend on the form of the disease and start at the ages of 5–40 years, more frequently the disease starts in boys 5–10 years of age. The disease manifests by progressive pyramidal deficiency with gait disturbances and cognitive impairment. Addison’s syndrome and suprarenal deficiency signs frequently precede neurological signs and may ensue later, and are absent at all in several cases. Progression of the disease is usually rapid, quadriparesis and ataxia develops, and in the late stages dementia, hearing and visual loss, and seizures appear. Adrenomyeloneuropathy usually starts after the age of 12; it is slowly progressive, signs of the spinal cord involvement and peripheral demyelination are marked, and cerebral signs may be absent. Females are asymptomatic carriers of the mutant gene; however, rare cases of females with neurological signs and X-ALD have been described (under inactivation of X chromosome, partial deletion of X chromosome, or presence of the mutant gene on another chromosome). Pathological studies reveal demyelination, cytoplasmic inclusions of unsaturated very long-chain fatty acids in cerebral macrophage cells, cysts, and perivascular lymphocytic infiltrates in the periventricular white matter, predominantly in parieto-occipital regions (Orrison, Jr. 2000). Resembling changes are detected in spinal pathways and peripheral nerves in adrenomyeloneuropathy. Neuroimaging picture is typical in adrenoleukodystrophy (Fig. 12.1). CT reveals hypodensity, and MRI reveals symmetrical hyperintensity in Т2 and hypointensity in Т1 in the deep white matter of the parieto-occipital regions, with the distribution in the splenium of corpus callosum (Barkovich 2000). Involvement of the splenium of corpus callosum and adjacent cerebral structures is explained by several authors by the increased expression of ALD protein in the glial peroxi-
Toxic and Metabolic Disorders
1007
Fig. 12.1a–f Х-linked adrenoleukodystrophy. CT (a), CT with CE
(b), MRI FLAIR (c), and Т1-weighted imaging (d). Splenium of corpus callosum and symmetrical adjacent parieto-occipital white matter are affected. As the disease progresses, lesions expands onto the internal capsule, temporal and deep white matter bilaterally, and peripheral white matter. Contrast medium accumulation is clear, in a rim shape on borders of affected areas and areas with ongoing demyelination (b). DWI b = 500 (e), b = 1000 (f). Clearly separated areas of markedly parieto-occipital white matter involvement (low signal on DWI) and area of active demyelination and perifocal oedema have increased signal. МRS (g) shows elevation of Lac–Lip complex, decrease of NAA and increase of Cho
1008
somes of these areas. Contrast administration reveals pathological enhancement on the periphery of the affected area on CT as well as on MRI, which indicates inflammatory changes during active demyelination. In early stages of the disease, peripheral white matter is intact, but with progression, it also gets involved. Т2 prolongation in the corticospinal (pyramidal) and corticopontine tracts within the brainstem and their CE are typical. In adrenomyeloneuropathy, cerebellar white matter and the brainstem portion of corticospinal tracts are often affected, as well as corticospinal tracts in the lateral columns of the spinal cord. Less typical imaging features of adrenoleukodystrophy have also been described. Sometimes calcifications are found in the parieto-occipital regions. Also, patients with predominant white matter involvement in the frontal, but not the parieto-occipital regions have been described (10–15% of cases), with the combination of symmetrical frontal and parieto-occipital regions involvement, as well as patients with asymmetrical involvement of only one hemisphere (1–2%). We observed only two of such cases (Figs. 12.2, 12.3). However, in more than two thirds of patients, bilateral and symmetrical involvement of the parieto-occipital regions and of the splenium of corpus callosum is seen. 1H MRS reveals the decrease of NAA, increase of Cho, Glx, decrease of mI, and increase of aliphatic hydrocarbons. In some cases, abnormal MRS changes precede those on MRI in time. On DWI, increased diffusion in the parieto-occipital regions is revealed. Laboratory diagnosis of adrenoleukodystrophy may be established if high concentrations of very long chain fatty acids (hexacosanoic and begenic) are found in blood serum and erythrocytes of skin fibroblasts culture.
12.2.1.2 Metachromatic Leukodystrophy The term metachromatic leukodystrophy was coined by L. Einarson and A. Nell in 1938, when these authors also established the disease as a distinct pathological entity among variants of Schilder’s leukoencephalitis, based on presence in the brain tissue of patients on autopsy such substances that are stained with aniline tinctures. The disease frequency is 1:40,000. It is autosomal recessive. The cause of metachromatic leukodystrophy in most cases is a deficiency of arylsulfatase-A. Its gene is mapped to 22q13.31-qter. It was shown that in some patients, the cause of the disease is a deficiency of a protein activator SAP I, under conditions of normal arylsulfatase A activity. The gene of SAP I is mapped to chromosome 10. In Austintype metachromatic leukodystrophy (multiple sulphatase deficiency, the more severe form of the disease), there is not only deficiency of arylsulfatase A, but also of six other sulphatases mapped to different chromosomes. In all forms of metachromatic leukodystrophy, accumulation of sulphatides in lysosomes is seen (in Austin type mucopolysaccharides and cholesteryl sulphate are also found), and rupture of myelin sheaths and neuronal demyelination. The precise mechanism of toxic action of sulphatides on myelin is not known. According to time of onset and clinical picture congenital, infantile, late infantile, juvenile, and adult variants of the disease are distinguished. In the congenital form, death occurs within the
Chapter 12
several hours after delivery, and in all cases, described diagnosis was made on autopsy. In other forms hypotonia, muscle weakness, ataxia, speech disturbances, and polyneuropathy are seen. Then, mental retardation ensues (or cognitive impairment in adult form), and extrapyramidal signs frequently predominate and seizures appear. Pathological studies reveal white matter demyelination in cerebral hemispheres, sulphatide inclusions in macrophages, astrocytes, cortical neurons of cerebral and cerebellar hemispheres, the spinal cord, and peripheral axons. Cortical atrophy of cerebral hemispheres and cerebellum is seen on autopsy. The neuroimaging picture is not specific, which may be explained by polymorphism of causes and course of the disease. On CT, progressive atrophy and diffuse hypodensity in the deep periventricular white matter are seen. On MRI (Fig. 12.4), symmetrical areas of Т1 and Т2 relaxation times prolongation are seen in the affected tissue. CE has not been reported. Peripheral white matter gets affected only in the latest stage of the disease (Faerber et al. 1999). On DWI, a nonspecific increase of diffusion in the affected demyelinated areas of deep periventricular white matter is seen, which may reflect increase of free water content there. No specific peaks on MRS were described in metachromatic leukodystrophy. Precise laboratory diagnosis of metachromatic leukodystrophy is, at present, impossible due to the large variety of its forms. Increased content of sulphatides is detected in urine. Decreased arylsulfatase-A activity is found in skin fibroblasts culture, and in Austin type, of other sulphatases as well. Metachromatic inclusions in blood cells may be found, which are not specific and can be seen in other inherited disorders, for instance, in Hurler mucopolysaccharidosis (Yakhno et al. 2001). Laboratory diagnosis has not yet been elaborated for cases of metachromatic leukodystrophy caused by protein activator SAP I deficiency.
12.2.1.3 Spongiform Leukodystrophy (Canavan’s disease) Leukodystrophy of Canavan-Van Bogaert-Bertrand (spongiform degeneration of the CNS) was described for the first time by American neuropathologist Canavan in 1931. Later Van Bogaert established that the disease is a distinct pathological entity. Frequency is not known, but the disease is thought to be very rare. The most cases have been described among Ashkenazi Jews; few cases were seen in Saudi Arabia and other regions. At present, 100 cases have been described. Inheritance is autosomal recessive. The mutant gene of N-aspartoacylase, the deficiency of which is a cause of spongiform leukoencephalopathy, is mapped to 17p13-pter, and different mutations are found in patients of different nationalities and geographic inhabitance. As a result of N-aspartoacylase deficiency in the brain, NAA accumulates in the brain excessively, which is highly toxic to oligodendroglia and leads to demyelination of the white matter. Clinicians distinguish neonatal (congenital), early infantile, late infantile, juvenile, and adult forms of the forms. Macrocephaly is the important sign of the disease. More frequently, the disease starts in the first year of
Toxic and Metabolic Disorders
Fig. 12.2a–f Rare atypical variant of Х-linked adrenoleukodystrophy (ventrodorsal): on Т2-weighted imaging (а), and Т1-weighted imaging (b) splenium and genu of corpus callosum are affected with parieto-occipital and frontal white matter involvement. Fragmentary
1009
CE of areas of demyelination is seen (c–e). MRS shows active demyelination and white matter destruction such as NAA decrease, Cho increase, and pathological Lac–Lip complex peak (f)
Fig. 12.3a–c Rare atypical variant of Х-linked adrenoleukodystrophy (unilateral): splenium of corpus callosum and the left parieto-occipital white matter involvement is seen. Marked pathological CE is seen in the left corticospinal tract (a–c)
1010
Chapter 12
Fig. 12.4a–d Metachromatic leukodystrophy: CT (a) and MRI: Т2-weighted imaging (b)
and Т1-weighted imaging (c) show that the deep white matter is affected and the peripheral white matter is almost spared, DWI with b = 1000 (d)—low signal (high diffusion velocity) in the affected white matter
life. Marked hypotonia, slack child syndrome, and seizures occur. With the disease progression, spasticity, cognitive decline, motor retardation, and optic atrophy develop. Death usually occurs in the second year of life. Pathological studies reveal increased brain weight, cerebellar atrophy, and a gelatinous or spongy consistency of brain tissue in Canavan’s disease. Microscopy reveals complete demyelination, including Ushaped fibres, and marked degeneration of the white matter and cortex. Myelin sheaths are affected in a way of ruptures with formation of vacuoles, and these changes contribute to the spongiform appearance of the brain. CT and MRI reveal diffuse and symmetrical involvement of cerebral white matter, without any focal predominance (Fig. 12.5). Peripheral white matter is involved in the early stages of the disease (in contrast to metachromatic leukodystrophy) and may look oedematous. White matter of the internal and external capsules is also affected. CE has not been reported. Specific and isolated globus pallidus involvement was described in absence of changes in other basal ganglia. Diffuse white matter atrophy and then cortical atrophy develop with progression of the disease. 1H MRS reveals the increase of N-acetylaspartate, which is typical for this disease (Barkovich 2000). In contrast to Canavan’s disease, cortical
CSF cysts and absence of the NAA peak are the distinguishing features of van der Knaap’s disease, which resembles Canavan’s disease clinically and radiologically (van der Knaap 1995). DWI of a single analysed case of this disease observed in our clinic revealed total involvement of corpus callosum, lateral parts of globus pallidus, both internal capsules, and the white matter of both cerebral hemispheres; however, areas of increased (predominantly) as well as decreased diffusion were seen within the recited regions. Decreased diffusion areas resembling those of a cytotoxic oedema were seen in different regions of the deep periventricular white matter without lacunar changes on routine MRI.
12.2.1.4 Alexander’s Disease Fibrinoid leukodystrophy with Rosenthal fibres was for the first time described by Alexander in 1949. Frequency is not known, but the disease is thought to be very rare. Several dozens of cases of the disease have been described at present, predominantly in boys. Most cases are apparently sporadic, but autosomal recessive inheritance is suggested in a few others. Precise biochemical defect of Alexander’s disease is unknown.
Toxic and Metabolic Disorders
Fig. 12.5a–f Spongiform leukodystrophy (Canavan’s disease). A series of axial Т2-weighted imaging (a–c), and sagittal Т1-weighted imaging (d) show total involvement of the cerebral white matter and lateral segments of globus pallidus, and putamen and caudate nuclei
1011
are intact (e black arrow). DWI with b = 1000 (f) reveals high signal in the affected white matter due to Т2 effect. MRS (g): typically high NAA
1012
It is suggested that the pathogenesis is due to accumulation of fibrillary α-B-crystalline protein in the pathologically changed astrocytes. It is thought that crystalline becomes insoluble in Alexander’s disease and produces conglomerates accumulating in astrocytes. In addition, pathological accumulation of sialo-lactosylceramide (GM3-ganglioside) in those cells is seen. The cause of these changes and their significance for brain damage is yet unexplained. Infantile and adult forms of the disease are distinguished. Macrocephaly since birth or developing within the first year of life is typical for the infantile form. Signs of increased intracranial pressure, with pouching of the occipital fonticulus may be present. Psychomotor retardation, spasticity, and seizures are clinical features. When the disease starts in years 2–12, psychomotor retardation, bulbar and pseudobulbar, and pyramidal signs are seen. The adult form starts after the age of 30. In most cases, multiple sclerosis or oedema is incorrectly diagnosed. Spasticity and ataxia are typical with cognitive decline on late stages. The disease is progressive, with fatal outcome several months or years after onset. Pathological studies reveal increased size of brain, and Rosenthal fibres, α-B-crystalline masses, dispersed through microfibrils of the cytosol of astrocytes in the white matter of cerebral hemispheres. Interestingly, Rosenthal fibres may also be seen in multiple sclerosis, tuberose sclerosis, Alzheimer’s disease, and several other disorders. CT reveals hypodensity of the frontal lobes white matter that expands gradually in a dorsocaudal direction into the parietal regions and internal capsules (Fig. 12.6). In the initial stage of the disease, CE may be seen within the affected deep periventricular white matter near anterior horns of the lateral ventricles. MRI affected areas typically have high signal on Т2- and low on Т1-weighted imaging. Peripheral white matter is involved beginning in the early stages of the disease. In the late stages, affected brain areas are transformed into CSF cysts, imitating holoprosencephaly (Bobele et al. 1990).
Chapter 12
12.2.1.5 Globoid Cell Leukodystrophy (Krabbe’s Disease) Krabbe’s disease (KD) also known as globoid cell leukodystrophy (galactosylceramide lipidosis), was described for the first time by paediatric neurologist K. Krabbe in 1916. The frequency is not known, but the disease is the most common in Sweden (1:25,000). Inheritance is autosomal recessive; the mutant gene is mapped to 14q21–q31. The disease often presents acutely between the third and the sixth months of life, with motor excitation, irritability, intermittent fever, difficulties when feeding, hyperreflexia, and failure to thrive. Optic atrophy and hypacusia are the most frequent signs. In the terminal stage, children have quadriparesis with bulbar signs. Death comes within the first years of life. Galactosylceramideβ-galactosidase deficiency is the cause of the disease. Absence of this enzyme leads to destruction of oligodendrocytes due to unknown cause. Psychosine accumulation is also seen in the affected cells. Despite that the main diagnostic test is detection of low β-galactosidase activity in the peripheral leukocytes and skin fibroblasts, CT signs also exist, which may be helpful at a certain stage of the disease. Hyperdensity of thalami, caudate nuclei, corona radiate, and dentate cerebellar nuclei may be seen in the initial stage of the disease. With the progression, diffuse white matter atrophy develops. On this stage, CT picture is identical to that of terminal stage of any myelinopathy. MR picture of KD is not specific. Т1 and Т2 prolongation in the deep periventricular white matter of cerebral and cerebellar hemispheres is seen (Fig. 12.7b,c). Brain is affected to the most extent in parietal lobes, with frequent involvement of the splenium of corpus callosum or the posterior part of the internal capsule (Farina et al. 2000). Isolated involvement of the corticospinal tract on MRI was reported in a few cases (van der Knaap and Valk 2005). Peripheral white matter is spared in the initial stage. MR signal of thalami may be normal, or Т1
Fig. 12.6a,b Alexander’s disease. Different
cases: CТ (a) and Т2-weighted imaging (b). Frontal white matter involvement bilaterally, in the case of (a), marked demyelination and destruction of the frontal lobes with porencephalic cysts formation are observed
Toxic and Metabolic Disorders
1013
Fig. 12.7a–c Globoid cell leukodystrophy (Krabbe’s disease). Т2-weighted imaging (a), Т1-weighted imaging (b) and Т1-weighted imaging (c) after CE. A nonspecific pattern of white matter of posterior frontal and parietal regions without CE is seen
and Т2 are prolonged. MR signs of thalami involvement ensue in a distant stage of the disease.
12.2.1.6 Novel Leukodystrophies Sometimes reports in literature appear about novel syndromes and diseases of the group of leukodystrophies that have not been described. Many of these cases are primarily diagnosed by MRI. In 1995, megalencephaly with leukodystrophy and subcortical cysts was discovered, which was later named by the author—van der Knaap’s disease. For many leukodystrophies, primary diagnoses by MRI corresponding to biochemical defects were detected in the subsequent years, as well as causative mutations. For such a disease as children’s ataxia with diffuse hypomyelination (vanishing white matter disease or CACH syndrome [van der Knaap et al. 1997]), which has been discovered recently, the mutant gene was detected, which allows considering the disease a distinct pathological entity and confirms the validity of primary neuroimaging approach. In these cases, neuroimaging techniques distinguish a novel syndrome, detecting peculiarities of white matter involvement, in terms of anatomical pattern (certain pathways affected, features of demyelinating or degenerative process), as well as in terms of unique pattern of MR signal changes or changes in ratios of metabolite peaks on MRS, etc (for example, New syndrome with hypomyelination with atrophy of the basal ganglia and cerebellum; van der Knaap et al. 2003). In 2002, independent groups of Dutch, Russian, and American scientists, described one more novel white matter involvement syndrome with the help of MRI in particular, called leukoencephalopathy with brainstem and spinal cord involvement and elevated white matter lactate (LBSL) (van der Knaap et al. 2003 ; Serkov et al. 2003). At present, this syndrome has been diagnosed in 40 patients. The disease is clinically characterised by progressive ataxia and pyramidal signs,
frequently combined with posterior columns involvement and mild cognitive impairment. MR picture is typical and includes heterogeneous symmetrical bilateral changes of the cerebral and cerebellar white matter and surprisingly selective involvement of pathways (Fig. 12.8). Corticospinal tracts are involved throughout their length, from the internal capsule to lateral columns of the spinal cord. Afferent pathways including posterior columns of the spinal cord, medial lemniscus up to thalamus, and corona radiate superior to thalamus, are also affected throughout their length. Cerebellar pathways are selectively involved too. The distinctive feature seen in most patients is involvement of intrabrainstem portion of the trigeminal nerve and mesencephalic pathway bilaterally, which have not been described in any other white matter disorder (Serkov et al. 2005). On MRS in the affected white matter, mild elevation of Cho and pathological Lac peaks are seen, which speaks to mild demyelination. Decrease of NAA and elevation of mI peaks more prominently speak to marked axonal loss and gliosis, respectively. DWI reflects the ultrastructural changes and shows increased diffusion of water molecules in all directions due to brain tissue destruction. As a whole, MRI and MRS findings suggest axonal loss and damage of the white matter. Involvement of pathways throughout their length speaks for primary axonal degeneration. The present element of demyelination must be secondary. It is difficult to explain marked dissociation between prominent MR changes of the white matter and relatively mild clinical manifestations. A wide spectrum of laboratory tests in LBSL patients failed to reveal pathological findings, except Lac elevation in blood. In recent years, LBSL cases in consanguine brothers and sisters, confirmed by MRI, were described. In 2007 the gene of this disease, which encodes mitochondrial aspartyl-tRNA synthetase, was found (Scheper et al. 2007). Thus, MRI is at present a single test to diagnose LBSL as clear clinical and laboratory criteria lack.
1014
Chapter 12
Toxic and Metabolic Disorders
1015
9 Fig. 12.8a–k Leukoencephalopathy with brainstem and spinal cord involvement and elevated white matter lactate (LBSL). White matter involvement anatomy in LBSL. Axial slices at the level of internal capsule: Т2-weighted imaging (a) shows symmetrical hyperintense signal in the deep and periventricular white matter of cerebral hemispheres. Splenium and genu of corpus callosum are clearly affected (black arrow), and the posterior part of the internal capsule (white arrow). Т1-weighted imaging (b) shows hypointense signal of the affected structures. c Т1-weighted imaging with CE (there is no contrast medium accumulation). Coronal slice (d) at the level of basilar artery on Т2-weighted imaging shows symmetrical involvement of centrum semiovale and corticospinal tracts up to cerebral peduncles (arrow). e Median sagittal slice (T2-weighted imaging)— total involvement of corpus callosum (black arrows), spinal cord involvement is clear observed (white arrow). f Axial slice on T2weighted imaging at the level of pons: medial lemniscus involvement
(black arrow), the mesencephalic trigeminal nerve pathway (thin white arrow) and the intrabrainstem portion of the trigeminal nerve root (thick white arrow). g FLAIR: at the level of endbrain—medulla with 5-mm slice thickness, involvement of posterior spinocerebellar tracts (black arrow), corticospinal tracts at the decussation level, pons, and cerebral peduncles (white arrows) are seen, involvement of medial lemniscus and its decussation (thick white arrows), and the mesencephalic trigeminal nerve pathway (thick white arrows). h DWI b = 1000: high signal of the affected white matter. i MRS with the area of interest in the affected white matter of the right frontal lobe: a decrease NAA–Cr ratio, increase of Cho–Cr, mI–Cr, and Lac– Cr ratios. MRI of the cervical and superior thoracic spine (Т2-Т1weighted imaging): median sagittal projection (j), increased signal in the dorsolateral portions of the spinal cord, axial projections (k) ascertain the lesion location—lateral corticospinal tracts and posterior columns (arrows)
12.2.2 Mitochondrial Disorders
netic classification. Moreover, many impairments of organic acids metabolism cause impairment of mitochondrial function. Should they be classified as mitochondrial disorders? Or are to be classified according to cytosolic enzymes whose function is impaired, or should be termed more specifically as “organic aminoacidaemia”? Of course, classification would be more precise, when biochemical defect are better studied. At present, it is important to understand that mitochondrial disorders and organic aminoacidaemias are not separate pathological entities and intermingle to a great degree. Neuroimaging diagnosis of mitochondrial disorders is usually difficult. In many patients, it is possible to suspect that their cases belong to this group, which is also unhampered according to clinical findings, but it is difficult to define a distinct pathology; however, several MD are successfully distinguishing such cases by MRI (Wray et al. 1995; Barragan-Campos et al. 2005). In several patients, only insufficient myelination and white matter Т2 prolongation are seen (Barkovich et al. 1993). However, in most patients, grey matter is also involved. It should be remembered that in children with deep periventricular white matter involvement, especially when combined with white matter involvement, MD should be considered for
Mitochondrial disorders (MD), which were recently considered a distinct group of pathological entities owing to successes in neuropathology, molecular genetics, and cellular organelles histochemistry, encompass diseases due to reduction of ATP production in cells with impaired mitochondria. One or several organs are involved, and frequently there are skeletal muscles and the brain. The most frequent clinical signs are seizures, low stature, cognitive impairment, muscle weakness, physical exertion intolerance, and neurosensory hearing loss. If a child has a classical complex of symptoms of a specific mitochondrial disorder, then diagnosis is made rapidly. In cases lacking a classical complex of symptoms, diagnosis of a specific mitochondrial disorder is difficult (Wolters 1982). Such a heterogeneity of symptoms cause difficulties in the classification of mitochondrial disorders. Several authors believe that a register of certain symptoms may be distinguished, which may be helpful in a more precise diagnosis. Others think that combinations of symptoms within separate syndrome are too variegated to satisfy any clinical classification, and they prefer molecular ge-
1016
differential diagnosis. Certain disorders, as MERRF (myoclonus epilepsy with ragged red fibres) and hereditary optic atrophy of Leber are manifested in adults also. Classification of mitochondrial disorders that manifest on MRI (Barkovich 2000) is as follows: 1. Isolated myopathy or predominant myopathic syndrome a. Fatal infantile myopathy b. Benign infantile myopathy 2. Predominant cerebral involvement a. Subacute necrotic encephalomyelopathy (Leigh’s disease) b. Alper’s syndrome c. МERRF d. Trichothiodystrophy (Menke’s disease) e. MELAS f. Glutaric aciduria type I and II g. Familial mitochondrial encephalopathy with macrocephaly, cardiomyopathy and complex I deficiency 3. Others a. Progressive external ophtalmoplegy i. Isolated ii. Combined with pigmental retinitis and systemic involvement (Kearns-Sayre syndrome) b. Encephalomyopathy in adults c. Myoneurogastrointestinal encephalomyopathy MR findings in mitochondrial disorders are extremely variable (Figs. 12.9–12.11), as well as causative genetic defects. The main diagnostic criteria are: • Persisting stroke-like lesions and areas (more specific for MELAS) (Castillo et al. 1995) • Frequent involvement of basal ganglia and brainstem (more specific for Leigh’s disease) • Multifocality of involvement, resemblance with MS (more specific for Leber disease) • Formation of cysts and foci of necrosis • Areas of high signal on DWI, Lac peak within MR spectra (for all disorders in periods of energetic crisis) • Atrophy in the affected regions It should be remembered that many forms caused by unknown biochemical and genetic defects as well as unknown MR findings are present within the group of mitochondrial disorders, which may inevitably lead to bias in diagnosis.
12.2.3 Aminoacidopathies and Organic Acidopathies Impairments of amino acids and organic acids metabolism are rare disorders due to deficiency of enzymatic function or transport system mediating metabolism of various amino acids. Oxidation of amino acids leads to increase of ammonia content up to toxic level. As the carbamid cycle takes part in the metabolism of ammonia, inherited defects of this cycle lead to hyperammoniaemia or to increase of plasma content of glutamine (which forms of ammonia). The defects of carbamid cycle are carbamyl phosphosynthetase deficiency, citrullinaemia (ornithine transcarbamylase deficiency) and argini-
Chapter 12
nosuccinic aciduria. Severity of clinical signs depends on the extent of metabolic compromise, and the duration of disease depends on dynamics of pathologic substrates accumulation, as well as on presence of other metabolic compromise (such as hypoglycaemia).
12.2.3.1 Phenylketonuria Phenylketonuria (PK) is the most well-known autosomal recessive disorder among acidopathies, which is mapped to genetic defect on 12q24–24.1. Mutation leads to phenylalanine hydroxylase deficiency; however, other genetic defects may also be causative. This enzymatic deficiency leads to elevation of phenylpyruvate and phenylacetate, as well as of phenylacetylglutamine—substances that are toxic to the developing brain. Untreated patients show stature and development retardation, exematous dermatitis, hypopigmentation, as well as a peculiar musty odour of the urine, skin, and hair. Diet and sometimes dietary supplements are required for treatment. Neuroimaging features includes abnormal white matter signal, indicating myelination impairment. In elderly patients, marked dilatation of ventricles due to white matter degeneration is noted. MRI shows prolongation of Т2 in the deep periventricular white matter of cerebral hemispheres (Pearsen et al. 1991; van der Knaap and Valk 1995). Peripheral white matter on early developmental stages is intact. The volume of affected white matter directly depends on treatment adequacy. CE is not reported (Fig. 12.12). In a few PK cases, due to dihydropterin reductase deficiency or tetrahydrobiopterine synthesis defects, the frontal, the occipital cortex, subcortical white matter, and putamen are affected. CT shows calcifications of the white matter of frontal, occipital lobes, and putamen. 1 H MRS reveals elevation of phenylalanine peak at 7.73 ppm (Barkovich 2000; Scott et al. 2002), detection of which is in many cases impossible due to limitations of scale of most scanners to 4 ppm. Follow-up of this peak size is helpful during treatment. Other peaks are normal. In cases of so-called maternal PK, which is not a disease, but an embryofetopathy—cerebral involvement in neonates whose mothers have PK—identical changes in the brain are seen in these children as those in patients. The only difference is that the progression of MR findings are absent and partial or complete reversibility of cerebral involvement is typical, or vice versa.
12.2.4 Primary Hepatocerebral Dystrophy (Wilson-Konovalov Disease) Primary hepatocerebral dystrophy (HCD) is a severe, inherited progressive disorder characterised by the combined involvement of internal organs (predominantly liver) and the brain (predominantly basal ganglia). C. Westphal (1883), A. Strumpell (1898), B. Kayser (1902), D. Fleischer (1903), and S. Wilson (1912) contributed to discovery of the disease. In 1912, S. Wilson published a paper with detailed description
Toxic and Metabolic Disorders
Fig. 12.9a–f Mitochondrial encephalopathy with unknown biochemical defect. Follow-up MRI with 6-month interval. Т2-weighted imaging (a) and Т1-weighted imaging (b) in the first examination. Acute involvement of the left putamen. The second study 6 months later (c,d). Negative dynamics is seen—head of the left caudate nucleus and the
1017
right putamen are involved; regress of oedema and cyst formation in the initially affected left putamen is seen. The third visit another 6 months later (e,f). Regress of acute changes is seen with cystic and atrophic transformation of putamina and caudate nuclei bilaterally, and secondary dilatation of the anterior horns of lateral ventricles Fig. 12.10a,b Kearns-Say-
re syndrome. Т2-weighted imaging (а,b) reveals typical features of the disease: diffuse bilateral involvement of deep and subcortical white matter of cerebral hemispheres, and the white matter of thalami, periventricular white matter is intact. Midbrain, tegmentum and medullary involvement is important feature
1018
Fig. 12.11a–f Subacute necrotising encephalomyelopathy (Leigh’s disease). Т2-weighted imaging (а) Т1-weighted imag-
ing (b), and FLAIR (c) images reveal expanded bilateral involvement of deep and partial of the subcortical white mater of cerebral hemispheres, with asymmetrically located necrotic cysts within. DWI (d,e) reveals low signal in the affected white matter and low diffusion, which points out prominent destruction. On MRS (f) high pathological Lac peak and marked reduction of NAA peaks are seen
Chapter 12
Toxic and Metabolic Disorders
1019
Fig. 12.12a–e Phenylketonuria. a,b Axial FLAIR. Mild
symmetrical hyperintensity in the deep white matter of cerebral hemispheres. c,d DWI b = 500 and b = 1000. МRS (e) does not reveal any pathological changes in the spectra, as the area of phenylalanine spectrum lies beyond the scale (7.35 ppm)
1020
Chapter 12
of clinical picture and pathological findings. HCD is a monogenic disorder with autosomal recessive inheritance. The gene was mapped to13q14.3 in 1985; it is responsible for the synthesis of P-type ATPase, transporting copper. The disease manifests according to its clinical forms between 7 and 25 years of age; however, later onset at 40 and even at 50 years of age has been described. Two basic mechanisms are responsible for pathogenesis of the disease—impairment of biliary excretion of hepatic copper fraction and secondary decrease of inclusion of copper into ceruloplasmin, which precedes its transport in blood. Impairment of biliary excretion of hepatic copper fraction leads to copper is stored in hepatocytes for a long time, causing Wilson’s hepatitis, leading to cirrhosis. In this stage, the disease is almost asymptomatic. When hepatocyte cytosol becomes overburdened with copper, it permeates the blood, causing haemolytic anaemia and visceral pathology. Copper ions excessively accumulating in human tissues and brain are highly toxic and may oxidise proteins and lipids of cellular membranes, increasing free oxygen species synthesis. First of all, copper accumulates in the brain and cornea, and Kayser-Fleischer forms corneal rings form, which is a specific, but not always a clearly detected sign of the disease. Copper deposition in basal ganglia is explained by peculiarities of the blood supply. In clinical practice, several forms of the disease are distinguished such as abdominal, akinetic–rigid, rigid and tremor, tremor (Westphal form), extrapyramidal and cortical, and fulminant (in children), in relation to predominance of these or those signs in clinical picture. Extent of the CNS involvement depends on the biochemical reserve of liver and time when toxic damage develops, and on timely diagnosis of the disease and treatment start. Pathological findings include atrophy of lenticular bodies, predominantly putamen, and also caudate nucleus, lateral segments of globus pallidus, dentate nuclei, and cerebral cortex, with formation of microcysts in basal ganglia. Microscopy reveals changes of glia in the affected structures, so-called Alzheimer’s glia types I and II, as well as atonia of small vessels leading to stasis and microhaemorrhages with spongiform changes. The neuroimaging picture is typical. On CT, which is less specific, symmetrical hypodensity of basal ganglia is usually seen (Fig. 12.13а). MR features of the disease are considered pathognomonic (Prayer et al. 1988) and encompass hyperintensity on Т2 and hypointensity on Т1-weighted imaging in
deep subcortical structures (putamen, caudate nuclei, lateral segments of globus pallidus, external capsules) (Mironov 1993), midbrain, pons, cerebellar dentate nuclei, and vermis (Fig 12.13b–f). Initially putamen, and caudate nucleus are affected. Median and dorsal portions of pons are affected, corticospinal tracts are spared, and signal changes of affected pontine structures are identical to the above cited. Sequential evolution of MR signal on dorsal part of pons resembles a panda’s face, which is formed by abnormal signal from central tegmental pathways. Involvement of midbrain is diffuse; however, white matter involvement predominates over that of nuclear grey matter, including that of red nuclei. In typical cases and high-resolution capacity, it is possible to detect bilateral symmetrical involvement (increased signal on Т2-weighted imaging) in the superior cerebellar peduncles, central tegmental pathways, striatonigral pathways, and rubrospinal tracts or lateral lemniscus. Selective and progressive involvement of midbrain and dorsal pons, respectively, “faces of the giant panda and her cub”, are typically hallmarks of primary HCD pattern (Van Wassanaer et al. 1996). Along with atrophy of the above cited, deep subcortical structures, more clearly seen on later stages of the disease, and areas of hypointensity on T2-weighted imaging in the putamina are seen due to copper deposition, which is better revealed if Т2* gradient echo pulse sequence is used. DWI clearly shows stages of changes seen in Wilson-Konovalov disease. At the onset, decreased diffusion and signal on DWI are seen in putamen and caudate nuclei, resembling that of cytotoxic oedema (Kishibayashi et al. 1999). Probably, these changes are due to toxic action of copper and swelling of cells, with reduction of diffusion. The same changes are seen later in the brainstem (midbrain and dorsal pons). In the late stage, spongiform degeneration and atrophy develops, which cause decreased signal on DWI and increased diffusion in the affected deep subcortical and brainstem structures (Fig. 12.13f). There are reports in the literature with separate descriptions of MR studies in Wilson-Konovalov disease by MRS (Taylor Robinson et al. 1996). On spectra taken from deep subcortical structures, NAA peak decrease, Cho peak increase, and possible presence of Lac are noted, which are nonspecific signs of brain tissue damage due to copper deposition and demyelination. Results of MRS also depend on the stage of the disease when the study was performed.
7 Fig. 12.13a–f Primary hepatocerebral dystrophy (PHCD) (Wilson-Konovalov disease). a CТ: symmetrical hypodensity in basal ganglia. MRI: Т2-weighted imaging (b,d), Т1-weighted imaging (c,e). Increased signal on Т2 and decreased on Т1-weighted imaging is seen in the deep subcortical structures (putamen, caudate nucleus, claustrum, the lateral segments of globus pallidus, exter-
nal capsule), midbrain, pons, dentate nuclei, and the cerebellar vermis. Selective and progressive involvement of midbrain and dorsal pons in a specific pattern for PHCD, called “faces of the giant panda and her cub”. f DWI: high signal is seen in the affected dorsal pons, and peripheral segments of putamen, which reveals active process in this areas
Toxic and Metabolic Disorders
1021
1022
Chapter 12
12.2.5 Hallervorden-Spatz Disease
12.2.6 Secondary Toxic and Metabolic Encephalopathies
Another name for Hallervorden-Spatz disease (HSD) is inherited pallidal degeneration, which is adopted in neurological manuals, but which reflects the essence of the disease pathogenesis not correctly, as the pathogenesis clearly supports the concept that HSD belongs to primary metabolic encephalopathies. HSD is a rare disease that was described by J. Hallervorden and H. Spatz in 1922 in a large pedigree, in which five consanguine sisters among 12 children were affected. At present, 40 families with HSD have been described, and observations of sporadic cases have been published that include clinical, laboratory, and MRI data supporting diagnosis. The disease is inherited as an autosomal recessive trait, the gene has not been mapped, and the primary biochemical defect is still unknown. The disease pathogenesis under conditions of unknown biochemical defect is supposed to be connected with impairment of metabolism of iron-containing substances. Neurological signs are caused by iron deposition in deep subcortical structures, predominantly in the lateral segments of globus pallidus. Typical cases manifest between 5 and 15 years of age; however, occasional descriptions exists with onset in 1–3 years of age and also late onset cases of HSD. The disease is manifested by gait disturbance due to increased muscle tone in children who have developed normally before. Typical are extrapyramidal signs—dystonia, muscle rigidity, oromandibular dystonia; as well, chorea, athetosis, tremor, and myoclonus may be seen. Pyramidal signs are frequently seen also such as extensor plantar responses, hyperreflexia, spasticity, and lower spastic paraparesis. Subcortical dementia with cognitive decline and personality deterioration is an important clinical feature. The disease inevitably progresses, survival includes those 8–20 years or older, and fatal outcome is usually due to secondary complications. The most important pathological feature is yellowish-brown discoloration of globus pallidus, pars reticularis substantia nigra, and red nuclei due to deposition of iron-containing pigment. Granules of pigment are seen in neurons, neighbouring glia, and perivascular spaces. In addition, local enlargement of axons in the affected structures is typical, abnormal mitochondria are seen, and there is proliferation of membranes and tubular structures, as well as in axons of cerebellum and peripheral nerves. Neuronal loss, gliosis, and diffuse demyelination of the white matter are also seen. MRI has an utmost importance as other diagnostic tools lack in HSD (Savoiardo et al. 1993; Hayflick et al. 2001). Marked hypointensity on T2-weighted imaging in the lateral segments of globus pallidus bilaterally due to paramagnetic effect of iron deposits with a small area of increased signal in this regimen is seen. Such a neuroimaging pattern is the “tiger eye”. In some cases, additional hyperintense areas on T1-weighted imaging are found in the centre of the affected zones—the so-called tiger eye pupils, which are hyperdensive on CT (petrificates). Other MRI and CT features are not specific (dilatation of external subarachnoid spaces of cerebral and cerebellar hemispheres, of the ventricular system), as they are signs of atrophy.
Acquired toxic and metabolic encephalopathies usually develop in adults; however, may also be seen in children, especially of school age. It is known that chemical substances affecting the CNS are specific to certain brain regions. This specificity is explained by the concept of functional systems (functional connection of neurons and their projections) and common biochemistry of certain brain regions (for instance, oxygen requirements, chemical composition, neurotransmitters). Thus, carbon dioxide is tropic to grey matter (globus pallidus); however, white matter may also be affected. Hexachlorophene contained in several antiseptic solutions for skin preparation selectively affect the white matter and cause vacuolating myelinopathy. Toluol is also trophic to the white matter (Valk and van der Knapp 1993). In children and adolescents with acute neurological signs and symmetrical white matter involvement, intoxications should always be ruled out. Cyanide poisoning, 3,4-methylenedioxymethamphetamine (Ecstasy) intoxication and inhalation of organic solvents (Harper and Butterworth 1997) may affect deep subcortical grey matter and sometimes cerebral (especially cyanides) and cerebellar cortex (Rosenow et al. 1995). Exposure of the CNS to a toxic factor may be exogenous or endogenous. It occurs when metabolic intrinsic pathways are deranged, for instance, in renal or liver deficiency. High content of toxic metabolites may circulate in blood, causing CNS intoxication or accumulating there, which leads to neurological impairments. Toxic agents may be trophic to grey or white matter, causing damage to these or those structures of grey or white matter. The classification of secondary toxic and metabolic encephalopathies with neuroimaging features is adduced below (Barkovich 2000; Scott et al. 2002, with modifications). Classification of Secondary Toxic and Metabolic Encephalopathies 1. With predominant grey matter involvement a. Wernicke’s encephalopathy b. Carbon dioxide poisoning 2. With predominant white matter involvement a. Central pontine (and extra pontine) myelinolysis b. Marchiafava-Bignami disease (central corpus callosum demyelination) c. Subacute combined degeneration of the spinal cord in vitamin B12 (cyanocobalamin) and folic acid deficiency—funicular myelosis d. Vitamin E (tocopherol) deficiency e. Radiation and chemotherapy associated leukoencephalopathy and myelopathy 3. With combined involvement a. Manganese intoxication b. Hepatic encephalopathy in chronic alcoholism (acquired hepatocerebral dystrophy) c. Organic solvents intoxication (toluol, hexachlorophene) d. CNS intoxications associated with opioids, cocaine, and other narcotic abuse
Toxic and Metabolic Disorders
12.2.6.1 Secondary Toxic and Metabolic Encephalopathies with Predominant Grey Matter Involvement Acquired TME of this group are characterised by predominantly nuclear damage of deep subcortical region and brainstem with or without concomitant cortical involvement. White matter involvement (demyelination) is also present but less prominent.
12.2.6.1.1 Wernicke’s Encephalopathy (Gayet-Wernicke Acute Alcoholic Encephalopathy) Wernicke’s encephalopathy is acute condition described for the first time by French physician C. Gayet in 1875 and again by German neurologist and psychiatrist R. Wernicke in 1881, due to deficit of vitamin B1 (thiamine). It may develop in alcoholics after prolonged starvation, and chronic vomiting with absorption impairment (intestinal obstruction, other malabsorption syndromes); it may be iatrogenic in digitalis intoxication or after infusion of large quantities of glucose without vitamin B1-emaciated patients. It is supposed that several individuals may be predisposed to Wernicke’s encephalopathy (WE) due to transketolase enzyme functional impairment; however, that has not been proven. The mechanism of CNS involvement in vitamin B1 deficiency is unknown. Pathological features are neuronal degeneration, demyelination, petechial haemorrhages, proliferation of capillaries, and astrocytes in the periaqueductal grey matter, mamillary bodies, thalami, and cerebellum. The classic clinical triad includes acute ophtalmoplegy, ataxia, and confusion. Korsakoff ’s psychosis may follow. Central hypothermia and hypotension are caused by hypothalamus involvement. In many patients, CNS involvement is combined with peripheral neuropathy. Urgent diagnostic tests are measurement of pyruvate content in blood and decrease of transketolase activity in erythrocytes. Treatment proceeds via immediate thiamine infusion with subsequent daily injections until improvement. Prognosis depends on the timely begun therapy; mortality is 10–20%, and residual neurological deficit is seen in over than 80% of cases on recovery. CT diagnosis of WE is not usually informative; however, in severe cases in the acute stage, bilateral hypodensity of dorsal and medial thalamic nuclei may be seen. MRI reveals hyperintensity on Т2-weighted imaging of the same structures, mamillary bodies, and periaqueductal grey matter with mild hypointensity on T1-weighted imaging. These changes are better seen on FLAIR images (Gallucci et al. 1990). Identical changes may be seen in brainstem due to involvement of its nuclei and periventricular white matter near the third ventricle. Due to moderate cytotoxic and vasogenic oedema of these structures, DWI in acute stage reveals high signal in the affected areas. CSF circulation impairment may be seen with moderate internal hydrocephalus due to oedema of periaqueductal grey matter at the level of midbrain, with temporary stenosis of the aqueduct. In mild deficit and with timely treatment, reversible changes of signal features in MRI are seen. In WE, patients with alcoholism degeneration and atrophy of cerebellum may
1023
ensue, as well as enlargement of subarachnoid spaces of the posterior fossa.
12.6.1.1.2 Carbon Dioxide Poisoning Carbon dioxide poisoning frequently occurs in cases of attempted suicide (from car exhaust in an enclosed garage, for instance); however, professional intoxications may occur. Chronic CO poisoning usually manifest by a nonspecific general cerebral signs and is pathogenically stimulated by hypoxia. In these cases, neuroimaging fails to reveal any changes, or nonspecific features of encephalopathy are revealed resembling that of chronic iaschemic brain disease (brain atrophy with dilatation of external and internal CSF spaces, enlargement of Robin-Virchow spaces, local areas of hyperintensity on T2-weighted imaging—areas of demyelination). Acute СО poisoning causes rapid brain oedema and coma, with high probability of fatal outcome. Brain oedema with focal or diffuse necrosis of cerebral cortex, cerebellum, and bilateral necrosis of globus pallidus are seen on autopsy what is typical for this intoxication. In 10% of survivors, secondary exacerbation ensues in a way of delirium with extrapyramidal, frequently tonic neurological signs. Akinetic mutism usually develops in most survivors, and they die of secondary complications (pneumonia, bedsores). In addition, periventricular white matter demyelination may also occur, which reflects acute exposure of myelin to CO and hypoxia. Neuroimaging of acute CO poisoning is typical (Fig. 12.14). CT reveals symmetrical hypodensity of globus pallidus. MRI reveals hyperintensity on Т2-, and hypointensity on Т1weighted imaging of these structures (O’Donnell et al. 2000) with CE. In some cases of CO poisoning, additional signs of hypoxic leukoencephalopathy may be seen, with increased signal intensity on Т2-weighted imaging and Т2-FLAIR-weighted imaging in deep white cerebral matter.
12.2.6.2 Secondary Toxic and Metabolic Encephalopathies with Predominant White Matter Involvement This conditionally distinguished group includes involvement of cerebral and spinal pathways, due to osmotic changes, several cofactors deficiency (vitamins group В), and physical and chemical factors causing destruction of myelin sheaths of pathways and usually selective destruction of white matter. Grey matter (cerebral cortex, basal ganglia, brainstem, and spinal nuclei) may be affected secondarily due to degenerative process.
12.2.6.2.1 Central Pontine (and Extrapontine) Myelinolysis (CPM) Myelinolysis central pontine (and extrapontine) myelinolysis (CPM) usually occurs in adult alcoholics with nutritional deficiency. Nutritional deficiency and rapid correction of hyponatraemia by intravenous infusion of NaCl, causing osmotic myelinolysis in the central parts of the pons. The risk group contains other patients with nutritional and electrolyte com-
1024
Chapter 12
Fig. 12.14a–g Carbon dioxide poisoning, acute period. Axial Т2-weighted imaging (a), FLAIR (b), Т1-weighted imaging without (c) and with (d) CE—bilateral involvement of lateral segments of globus pallidus. DWI b = 500 (e) and b = 1000 (f) do not reveal any pathological changes. MRS (g) with the area of interest in the affected left globus pallidus—decreased NAA peak and appearance of Lac peak
promise. However, precise pathogenic events leading to CPM are sill not known. In children, CPM occurs in fulminant hepatitis, a chronic disease with nutritional deficiency with severe electrolyte compromise. Neuroimaging in children is identical to that in adults with CPM. CT reveals hypodensity and MRI reveals T2 and T1 prolongation in the central pons; frequently a regular, oval-shaped lesion is revealed—rarely is a lesion is asymmetrical. Corticospinal tracts are intact (Gocht and Colmant 1987; Miller et al. 1988). Recovery as well as improve-
ment of MRI picture is possible if slow correction of electrolyte and nutritional deficiency is managed (Fig. 12.15). Extrapontine myelinolysis is an osmotic myelinolysis not in the pons, but in other CNS regions. According to different authors, signs in these patients manifest just after rapid correction of electrolyte compromise, so the causes are same as in pontine myelinolysis. Т2 prolongation is seen on MRI within external capsule and putamen. Extrapontine myelinolysis may occur in an isolated manner or together with the pontine.
Toxic and Metabolic Disorders
1025
Fig. 12.15a–f Central pontine myelinolysis. Axial Т2-weighted imaging (a), Т1-weighted imaging without (b) and with (c) CE, DWI (d) respectively at the level of pons. An oval area hyperintense in Т2-weighted imaging, and hypointense in Т1 in the central pons is
shown without CE, with high signal on DWI (intramyelin oedema). The follow-up study 1 month later after successful treatment (e,f) revealed that signal changes in pons disappeared
12.2.6.2.2 Marchiafava-Bignami Disease (Central Corpus Callosum Demyelination)
may be seen in optic chiasm, anterior commissure, centrum semiovale, and the middle cerebellar peduncles. On microscopy, demyelination with intact axons is revealed. Central fibres of corpus callosum are usually affected, and superior and inferior parts remain intact. There is a loss of oligodendroglia and many macrophages with lipid inclusions appear. Mild reactive changes of astrocytes are seen. Vessels within and outside of necrotic foci do proliferate; hyalinosis is seen in their walls. The pathogenesis of MBD is unclear. Resembling lesions are seen in CO and cyanide poisoning. Neuroimaging in the acute stage includes diffuse oedema of corpus callosum with hyperintensity on Т2-weighted imaging. On the follow-up MRI in the chronic form, focal necrosis of genu, body, and splenium of the corpus callosum is revealed, with hypointensity on T1-weighted imaging. Confluent hyperintense foci are seen on T2-weighted imaging in subcortical and periventricular white matter. According to several authors, extracallosal lesions may disappear with time and thus they are likely to correspond to oedema and not demyelination. Concomitant signs of WE and CPM may occur in these patients too.
Marchiafava-Bignami disease (MBD) is a rare disorder in which primary necrosis of corpus callosum with rare involvement of extracallosal regions is seen. It develops in male alcoholics with over 20 years of abuse. Initially, it was found in Italian patients who abused red wine. Later, cases of MBD were described in starving nonalcoholics. Clinical picture develops acutely with confusion, seizures, dysarthria, ataxia, diffuse increase of muscle tone, pyramidal signs, and frontal disinhibition. Most patients die within the first days. Subacute and chronic forms may course for months and years, with progressive dementia and sometimes confusion, signs of interhemispheric associative fibbers damage, pyramidal and cerebellar signs, and fatal outcome. For some time, diagnosis was made only on autopsy; however, many cases were diagnosed before death by MRI and CT. In recent years, survivors were described who had undergone timely nutritional support and thiamine administration. Largely, MBD is characterised by foci of cystic necrosis predominating in genu and body of corpus callosum (Celik et al. 2002). Extracallosal foci
1026
12.2.6.2.3 Subacute Combined Degeneration of the Spinal Cord (Funicular Myelosis) In vitamin В12 (cobalamine) and/or folic acid deficiency, the peripheral nervous system and, more prominently, the spinal cord are affected. Subacute combined degeneration of the spinal cord develops with demyelination and vacuolisation of posterior and lateral columns. The most frequent causes of cobalamine deficiency are pernicious anaemia and autoimmune gastritis in which the internal Castle factor is absent. In addition, vitamin В12 deficiency develops after gastric surgery and in malabsorption syndrome. The symptoms of funicular myelosis are general fatigue and paraesthesia in the arms and feet. As the disease progresses, gait disturbances appear, and palsies in lower extremities with further development of spastic and ataxic paraplegia with contractures occur. Deep sensation and sense vibration loss occur. Treatment comprises monthly life-long injections of vitamin B12. The most important factor determining the treatment efficacy is a time of onset of the disease. Funicular myelosis is a secondary demyelination. Longterm course causes secondary axonal degeneration. On autopsy, the brain looks normal, and the spinal cord is atrophic. Posterior and lateral columns have greyish pallor, and are thinned and semi-transparent. Early pathological signs are swelling of myelin sheaths, with relative preservation of axons. Foamy macrophages and perivascular lymphocytic infiltration are found in the foci of necrosis. Initially, foci are small; later they become confluent. In the severe cases of disease, the spinal cord is vacuolated, demyelinating lesions affect posterior and lateral columns throughout its length, and sometimes anterior columns are affected. Small areas of perivascular demyelination may be found in the brain. On MRI, hyperintensity of the spinal cord is seen on Т2weighted imaging of the cervical and thoracic regions, with predominant involvement of posterior columns. Mild en-
Chapter 12
largement of the spinal cord is seen with mild CE (Scott et al. 2002). Posterior column signal changes are distributed throughout the length of spinal cord, which differentiates it from demyelination of other origin, whose foci are disseminated (for instance, in multiple sclerosis). Vacuolar myelopathy in AIDS has a similar MR picture. History plays very a important role in differentiation of these conditions. Neurological signs in SCDS may regress after treatment with B12 vitamin with positive follow-up MR changes (Fig. 12.16). Brain MRI may reveal hyperintense lesions on Т2-weighted imaging in the white matter, which also may regress after treatment with vitamin B12.
12.2.6.2.4 Radiation- and Chemotherapy-Associated Leukoencephalopathy and Myelopathy These conditions are usually discussed together, as they develop in patients after radiation and chemotherapy for neurooncological disorders. However, there are cases when patients undergo only radiation (tumours, vascular malformations) or only chemotherapy; sometimes postchemotherapy encephalopathy develops in patients underwent chemotherapy for an extraneural tumour. Consequences of isolated brain exposure to radiation, such as radiation necrosis, postradiation leukoencephalopathy, and myelopathy are discussed in the chapters on neuro-oncology. Here we discuss only postchemotherapy leukoencephalopathy and combined involvement of brain after radiation and chemotherapy. White matter involvement may ensue after chemotherapy. The drugs that cause leukoencephalopathy are methotrexate, cisplatin, arabinosylcytosine, carmustin, and thiotepa. White matter changes seen on MRI in these cases may be reversible and asymptomatic. In acute damage, neurological signs are usually present. In these cases, neuroimaging features are minimal. DWI may register decreased diffusion, which may
Fig. 12.16a–c Subacute combined degeneration of the spinal cord (funicular myelosis). On Т2-weighted imaging (a) there is hyperintense signal in dorsal parts of the spinal cord throughout all the study. A typical triangle-shaped, symmetrical involvement of the posterior funiculi of the spinal cord is seen (b,c arrows)
Toxic and Metabolic Disorders
1027
Fig. 12.17a–f Postchemotherapy leukoencephalopathy. Т2-weighted imaging (а), FLAIR (b): diffuse involvement of the periventricular white matter of cerebral hemispheres; Т1-weighted imaging before (c) and after (d) contrast medium injection: there is no pathological CE. e,f DWI b = 500 and b = 1000, respectively
help in the differential diagnosis. In contrast to focal white matter involvement seen after postradiation leukoencephalopathy, areas with Т1 and Т2 prolongation, occurred in a delayed period after chemotherapy, are usually symmetrical, diffuse, and occupy large territories (Fig. 12.17). T2 prolongation occurs first in the central and periventricular white matter; subcortical U-shaped fibres are relatively spared (Stemmer et al. 1994). Corpus callosum and anterior commissure are often spared. If CE occurs after contrast medium administration, then it is multifocal and locates deeply in centum semiovale. Signal changes in the white matter usually reverse after cancellation of treatment, but may persist for life with adjoining of secondary nonspecific changes (gliosis and moderate ventricular dilatation). Results of 1H MRS in early stages of the white matter involvement due to chemotherapy suggest that T2 prolongation is due to myelin damage, and show elevation of Cho peak and appearance of Lac in spectra (Brown et al. 1995).
It is important to understand that combined exposure to radiation and chemotherapy causes damage more severe to brain tissue than that of these treatments separately (Scott et al. 2002). In cases of combined exposure prominent brain oedema, CE and mass effect within the projection of radiation fields are seen. These features occur within 5–13 months (10 months in average) after treatment. It may be difficult to differentiate a focus of radiation necrosis from relapse of a tumour. Leukoencephalopathy after combined treatment develops usually later than a tumour relapse, is usually multifocal, and often lesions are located very distant from each other, even contralaterally (Fig. 12.18). Identical changes may be seen in the spinal cord (postchemotherapy or combined myelopathy), with appropriate neurological signs. In these cases a myelopathy or metastasis, not only a primary intramedullary tumour, should also be suspected in patients who underwent chemotherapy even long
1028
Chapter 12
Fig. 12.18a–e Necrotic postradiation
leukoencephalopathy after combined radio- and chemotherapy of the sphenoid sinus cancer. Т2-weighted imaging (а–c) and Т1-weighted imaging with CE (d,e). Expanded almost symmetrical white matter involvement of the cerebral hemispheres with intact deep subcortical structures (vasogenic oedema, radiation-associated demyelination), and radiation necrosis of basal parts of the frontotemporal regions with demarcation CE
ago, if there are hyperintense areas on Т2, and hypointense areas on Т1-weighted imaging with CE in the spinal cord.
12.2.6.3 Secondary Toxic and Metabolic Encephalopathies with Combined Grey and White Matter Involvement 12.2.6.3.1 Manganese Intoxication Manganese poisoning is encountered among people working in the mining industry. In addition, it develops in ephedrine abusers (a mixture of ephedrine and potassium permanganate). Rare occasions of manganese intoxications were described in patients fed with manganese-containing enteral nutrition (Isocal). The clinical picture in drug abusers or individuals with other origin of intoxication includes manganese dementia syndrome—increased motor activity and hallucinations. Chronic intoxication leads to neuronal loss in basal ganglia, substantia nigra with manganese depositions in these
structures, and development of extrapyramidal, mainly parkinsonian, signs. CT diagnosis of manganese intoxications usually fails to reveal any changes. MRI reveals bilateral hyperintensity in putamen and caudate nucleus on T1, and in cerebral peduncles and quadrigeminal lamina, and corticospinal tracts in the superior cervical spinal segments due to paramagnetic effect of manganese deposits (Fig. 12.19). Т2-weighted imaging shows no changes. MRS shows displacement of spectra above the zero line due to paramagnetic effect of the metal (Wolters et al. 1982; Scott et al. 2002).
12.2.6.3.2 Hepatic Encephalopathy in Chronic Alcoholism (Acquired Hepatocerebral Leukodystrophy) In chronic alcoholism with toxic hepatitis and cirrhosis of liver, as in cases of primary hepatocerebral leukodystrophy (Wilson-Konovalov disease), hepatic encephalopathy with
Toxic and Metabolic Disorders
Fig. 12.19a–e Manganese intoxication. Т2-weighted imaging (a) and
Т1-weighted imaging in axial (b) and sagittal (c) projections. Hyperintensity on Т1-, and hypointensity on Т2-weighted imaging are seen in caudate nuclei and putamina bilaterally, and in corticospinal tracts in the cerebral peduncles due to paramagnetic effect of manganese
resembling neurological signs (extrapyramidal and cerebellar) may develop. Pathological studies show microcavities on borders of grey and white matter subcortically and within cerebral and cerebellar cortex, neuronal loss, and destruction of myelin sheaths of basal ganglia and cerebellum. In addition, due to impairment of protein-synthesising liver function and decreased transferring and ceruloplasmin synthesis (transport proteins for copper and zinc), accumulation of these metals in the lateral segments of the globus pallidus usually occur. The neuroimaging picture is specific in cases when patients have an appropriate history: the presence of hyperintense signal on Т2-weighted imaging and hypointense signal on Т1-weighted imaging in globus pallidus bilaterally (Fig. 12.20). High signal due to paramagnetic effect of metals may also be registered
1029
deposition. DWI (d) with echo-planar PS more clearly reveals the decreased signal in these structures than does Т2-weighted imaging. MRS (e): displacement of zero line upwards due to paramagnetic effect of metal on MR signal
along cerebral peduncles (Brunberg et al. 1991). Acquired hepatocerebral leukodystrophy should be differentiated from manganese intoxication on MRI.
12.2.6.3.3 Organic Solvents Intoxication This problem exists among young people who are addicts and inhale glue. Toluol and other organic solvents are rapidly delivered from inhaled air into blood, pass the BBB, and enter the CNS. Acute encephalopathy with neurological impairment and cognitive decline develops. Pathological studies reveal axonal loss with secondary demyelination, diffuse demyelination in cerebral and cerebellar white matter, degeneration and gli-
1030
Chapter 12
Fig. 12.20a–c Secondary hepatocerebral dystrophy in a patient with cirrhosis of liver and a long history of alcoholism. a Т2-weighted imaging: there are no obvious pathological findings. Т1-weighted imaging in axial (b) and coronal (c) projections—increased signal in putamina and caudate nuclei bilaterally is observed
osis of ascending and descending pathways, peripheral nerves and axons of corpus callosum and, in late stages, generalised cerebral and cerebellar atrophy. MRI shows smoothening of borders between white and grey matter, diffuse T2 prolongation in the cerebral and cerebellar white matter, often mild Т2 shortening in putamen and enlargement of cerebral and cerebellar sulci (Xiong et al. 1993; Yamanouchi et al. 1995). In severe cases, Т2 shortening is seen in thalami, substantia nigra and cerebral cortex.
12.2.6.3.4 CNS Intoxications Associated with Narcotic Abuse These conditions were partially discussed in previous sections. Except for specific MR changes in manganese intoxication and organic solvent poisoning, cyanides, in drug addicts (opioids, cocaine, marijuana, phencyclidine, etc,), cerebral angiospasm with subsequent strokes are frequently seen with residual neurological deficits with typical neuroimaging picture (Valk et al. 1992; Chen et al. 2000; Keogh et al. 2003).
Refere n c e s Barkovich A (2000) Pediatric neuroimaging third edn. LippincottRaven, Philadelphia, p 890 Barkovich A, Good W, Koch T, Berg B (1993) Mitochondrial disorders: analysis of their clinical and imaging characteristics. Am J Neuroradiol 14:1119–1137 Barragan-Campos H, Vallee J, Lo D et al (2005) Brain magnetic resonance imaging findings in patients with mitochondrial cytopathies. Arch Neurol 62:737–742 Bobele G, Garnica A, Schaefer G et al (1990) Neuroimaging findings in Alexander’s disease. J Child Neurol 5:253–258 Brown M, Simon J, Stemmer S et al (1995) MR and proton spectroscopy of white matter disease induced by high-dose chemotherapy with bone marrow transplant in advanced breast carcinoma. AJNR Am J Neuroradiol 16:2013–2020 Brunberg J, Kanal E, Hirsch W, Van Thiel D (1991) Chronic acquired hepatic failure: MR imaging of the brain at 1.5 T. AJNR Am J Neuroradiol 12:909–914 Castillo M, Kwock L, Green C (1995) MELAS syndrome: imaging and proton MR spectroscopic findings. AJNR Am J Neuroradiol 16:233–239
Celik Y, Kaya M, Sengun S, Utku U (2002) Marchiafava-Bignami disease: cranial MRI and SPECT findings. J Clin Neurol Neurosurg 104:339–341 Chen C, Lee K, Lee C et al (2000) Heroin-induced spongiform leukoencephalopathy: value of diffusion MR imaging. J Comput Assist Tomogr 24:735–737 Clark J, Marks M, Adalsteinsson E et al (1996) MELAS: clinical and pathologic correlations with MRI, xenon/CT and MRS. J Neurol 46:223–227 Engelbrecht V, Scherer A, Rassek M et al (2002) Diffusion-weighted MR imaging in the brain in children: findings in the normal brain and in the brain with white matter diseases. J Radiol 222:410–418 Faerber E, Melvin J, Smergel E (1999) MRI appearances of metachromatic leukodystrophy. J Pediatr Radiol 29:669–672 Farina L, Bizzi A, Finocchiaro G et al (2000) MR imaging and proton MRS in adult Krabbe’s disease. AJNR Am J Neuroradiol 21:1478–1482 Gallucci M, Bozzao A, Splendiani A et al (1990) Wernicke’s encephalopathy. MR findings in five patients. AJNR Am J Neuroradiol 11:887–892
Toxic and Metabolic Disorders
Gocht A, Colmant H (1987) Central pontine and extrapontine myelinolysis: a report of 58 cases. J Clin Neuropathol 6:262–270 Harper C, Butterworth R (1997) Nutritional and metabolic disorders. In: Graham D, Lantos P (eds) Greenfield’s neuropathology, vol 2, 6th edn. Arnold, London, pp 601–652 Hayflick S, Penzien J, Michl W et al (2001) Cranial MRI changes may precede symptoms in Hallervorden-Spatz syndrome. J Pediatr Neurol 25:166–169 Keogh C, Andrews G, Spacey S et al (2003) Neuroimaging features of heroin inhalation toxicity: “chasing the dragon.” AJR Am J Radiol 180:847–850 Kishibayashi J, Segawa F, Kamada K, Sunohara N (1993) [Study of diffusion weighted magnetic resonance imaging in Wilson-Konovalov disease.] Rinsho Shinkeigaku 33:1086–1089 (in Japanese) Miller G, Baker Jr H, Okazaki H, Whisnant J (1988) Central pontine myelinolysis and its imitators: MR findings. J Radiol 168:795–802 Mironov A (1993) Decreased signals intensity of the putamen and the caudate nucleus in Wilson disease of the brain. J Neuroradiol 35:166 O’Donnell P, Buxton P, Pitkin A, Jarvis L (2000) The magnetic resonance imaging appearances of the brain in acute carbon monoxide poisoning. J Clin Radiol 55:73–280 Orrison WW Jr (ed) (2000) Neuroimaging. Saunders, Philadelphia, p 1782 Pearsen K, Gean-Marton A, Levy H, Davis K (1990) Phenylketonuria: MR imaging of the brain with clinical correlation. J Radiol 177:437–440 Prayer L, Wimberger D, Kramer J et al (1990) Cranial MRI in Wilson-Konovalov disease. J Neuroradiol 32:211–214 Rosenow F, Herholz K, Lanfermann H et al (1995) Neurological sequelae of cyanide intoxication: the patterns of clinical, magnetic resonance imaging and positron emission tomography findings. J Ann Neurol 38:825–828 Savoiardo M, Halliday W, Nardocci N et al (1993) HallervordenSpatz disease: MR and pathologic findings. AJNR Am J Neuroradiol 14:155–162
1031
Stemmer S, Stears J, Burton B et al (1994) White matter changes in patients with breast cancer treated with high dose chemotherapy and autologous bone marrow support. AJNR Am J Neuroradiol 15:1267–1273 Taylor Robinson S, Sargentoni J, Oatridge A et al (1996) MR imaging and spectroscopy of the basal ganglia in chronic liver disease: correlation of T1-weighted contrast measurement with abnormalities in proton and phosphorus-31 MR spectra. J Metab Brain Dis 11:249–268 Temin P, Kazantseva L (2001) Congenital disturbance of neuro-psychic development in children: manual for physicians. Medicine, Moscow, p 432 (in Russian) Valk J, van der Knaap M (1992) Toxic encephalopathy. AJNR Am J Neuroradiol 13:747–760 van der Knaap M, Barth P, Stroink H et al (1995) Leukoencephalopathy with swelling and a discrepantly mild clinical course in eight children. J Ann Neurol 37:324–334 van der Knaap M, Barth P, Gabreëls F et al (1997) A new leukoencephalopathy with vanishing white matter. J Neurol 48:845–855 van der Knaap M, Smit L, Barth P et al (1997) MRI in classification of congenital muscular dystrophies with brain abnormalities. J Ann Neurol 42:50–59 van der Knaap M, Breiter S, Naidu S et al (1999) Defining and categorising leukoencephalopathies of unknown origin: MR imaging approach. J Radiol 213:121–133 van der Knaap M, Naidu S, Pouwels P et al (2003) New syndrome characterised by hypomyelination with atrophy of the basal ganglia and cerebellum. AJNR Am J Neuroradiol 23:1466–1474 van der Knaap M, van der Voorn P, Barkhof F et al (2003) Leukoencephalopathy with brainstem and spinal cord involvement and high lactate. J Ann Neurol 53:252–258 van der Knaap MS, Valk J (eds) (2005) Magnetic resonance of myelin, myelination, and myelin disorders, 3rd edn. Springer, Berlin Heidelber New York, p 1084 van Wassanaer-Van Hall H, Van den Heuvel A, Algra A et al (1996) Wilson disease: findings at MRI imaging and CT of the brain with clinical correlation. Radiology 198:531–536
Scott W et al (2002) Magnetic resonance imaging of the brain and spine, 3rd edn. Lippincott Williams & Wilkins, Philadelphia, p 1240
Veltisthev J, Temin P (1998) Congenital diseases of central nervous system: manual for physicians. Medicine, Moscow, p 496 (in Russian)
Serkov S, Pronin I, Bykova O et al (2003) [Three cases of non-differentiated leukodystrophy with injury of the deep white matter of the hemispheres, cerebellum and specific injury of the neural tracts.] J Neurol Psychiatr 7:61–68 (in Russian)
Wang Z, Zimmermann R (1998) Proton MRS of pediatric brain metabolic disorders. J Neuroimaging Clin North Am 8:781–807 Wolters E, van Wijngaarden G, Stam F et al (1982) Leukoencephalopathy after inhaling heroin pyrolysate. Lancet 2:1233–1237
Serkov S, Pronin I, Fadeeva L, Kornienko V (2003) Neuroradiology in diagnostics of leukodystrophy. J Med Visualis 2:77–90 (in Russian)
Wray S, Provenzale J, Johns D, Thulborn K (1995) MR of the brain in mitochondrial myopathy. AJNR Am J Neuroradiol 16:1167–1173
Serkov S, Pronin I, Bykova O et al (2004) Five patients with a recently described novel leukoencephalopathy with brainstem and spinal cord involvement and elevated lactate. J Neuropediatr 35:1–5 Scheper GC, van der Klok T, van Andel R, van Berkel C, Sissler M, Smet J, Serkov S et al (2007) Mitochondrial aspartyl-tRNA synthetase deficiency causes leukoencephalopathy with brain stem and spinal cord involvement and lactate elevation. Nat Genet 39:534–539
Xiong L, Matthes J, Li J, Jinkins J (1993) MR imaging of “spray heads”: toluene abuse via aerosol paint inhalation. AJNR Am J Neuroradiol 14:1195–1199 Yamanouchi N, Okada S, Kodama K et al (1995) White matter changes caused by chronic solvent abuse. AJNR Am J Neuroradiol 16:1643–1649 Yakhno N, Shtulman D (2001) [The diseases of the nervous system.] Medicine, Moscow, p 480 (in Russian)
Chapter 13
Demyelinating Diseases of the Central Nervous System
13
in collaboration with S. Serkov
13.1 13.2 13.3
Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1033 Primary Demyelinating Diseases .. . . . . . . . . . . . . . . . . . . . . . . . . 1034 Disorders with Secondary Demyelination and/or Destruction of White Matter .. . . . . . . . . . . . . . . . . . . . . . 1063
13.1 Introduction The term demyelinating diseases of CNS denotes primary conditions of unknown aetiology (idiopathic) that cause destruction of normally developed myelin sheaths. These disorders are multiple sclerosis, its classic form, and atypical types (Marburg, Devic’s opticomyelitis, Balò’s concentric sclerosis, and Schilder’s disease) and inflammatory, tumour-like demyelination. In addition, there are disorders with secondary demyelination and/or destruction of white matter, such as acute disseminated encephalomyelitis (ADEM), progressive multifocal leukoencephalopathy (PML), HIV-associated leukoencephalopathy, and several slowly progressive demyelinating disorders of viral aetiology. Several authors relate to demyelinating disorders other secondary demyelinating conditions of other aetiologies, such as nutritional and vitamin deficiency, osmotic impairments (central pontine myelinolysis, Marchiafava-Bignami disease and others), genetic abnormalities (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, AVED syndromes, ataxiatelangiectasia, α-β-lipoproteinaemia, etc.), and several other diseases and conditions. Only classic demyelinating will be discussed in this chapter. Inherited myelinopathies and secondary demyelinating disorders of toxic and metabolic origin are discussed in Chap. 12. It is important to note that disorders such as vascular encephalopathy (chronic ischaemic brain disease, hypertonic
encephalopathy, Binswanger’s disease), vasculitis, several granulomatous and autoimmune disorders (Behçet’s disease, Wegener’s granulomatosis, lupus erythematosus etc.), infectious and allergic disorders (neuroborreliosis, neurobrucellosis, neurosyphilis, viral encephalitis etc.), neurotrauma, degenerative disorders, prion diseases, storage diseases, and many others morphologically lead to myelin loss (demyelination) of CNS pathways, causing MR signal changes. However, they are not related to demyelinating disorders at present as they have another pathogenesis. Classification of Classic Demyelinating Disorders (Scott et al. 2002, with modifications) 1. Primary demyelinating disorders a. Multiple sclerosis (MS) i. Classic Charcot type ii. Acute malignant Marburg type of MS iii. Diffuse cerebral sclerosis (Schilder type) iv. Balò’s concentric periaxial sclerosis v. Devic’s opticomyelitis vi. Inflammatory pseudotumour demyelination 2. Disorders with secondary demyelination and/or destruction of white matter a. ADEM b. Classic (acute disseminated encephalomyelitis) c. Hyperacute (acute haemorrhagic leukoencephalitis (Hurst disease) i. Subacute sclerotising panencephalitis (Van Bogaert’s disease) ii. Progressive rubella panencephalitis iii. PML iv. HIV-dementia complex and HIV-associated myelopathy CT is uninformative in diagnosis of demyelinating diseases (DD). Large (over 1–2 сm in diameter) lesions of demyelination can be seen on CT as hypodense areas, more clearly in late stages of disease. In the acute phase of disease on CT, there could be CE of lesions with perifocal vasogenic oedema. Demyelinating lesions less than 1 сm in diameter usually are not revealed on CT. Calcifications are not typical for DD. In rare cases, in the hyperacute form of ADEM, haemorrhagic
1034
transformation of lesions may be seen, and CT reveals them as areas of heterogeneously increased density. The main technique that allows diagnosing DD is MRI (Ge 2003). Standard Т1- and Т2- axial-weighted imaging is used. FLAIR sequences, which suppress CSF signal, are helpful if signal changes on T2-weighted imaging are not clear and for better detection of demyelinating lesions bordering with CSF spaces. For better imaging of corpus callosum, brainstem, and cerebellar peduncles, which are frequently affected in MS, sagittal and frontal Т2-weighted imaging or FLAIR images should be made. MR picture of corpus callosum involvement seen on T2-weighted imaging or FLAIR images in classic MS is called the “Venus necklace”. With CE, it is possible to detect active demyelinating lesions and to diagnose the phase of disease, which is important in making treatment decision. DWI and MRS are modern MR techniques, revealing subtle ultrastructural changes of white matter and basic metabolites in areas of demyelination. They allow judging the stage of demyelination, and can be used as diagnostic tools for the follow-up of treatment efficacy. Neuroimaging picture of DD is nonspecific, in cases with scanty pathological changes, it is feasible to perform complex MR investigation with CE, modern PS such as FLAIR, magnetisation transfer (MT), DWI, and MRS, especially in a follow-up manner to establish a diagnosis. In general, it should be remembered that DD are characterised by multiple, focal, and asymmetrical lesions in white matter in contrast to inherited disorders causing demyelination and secondary toxic and metabolic disorders, for which bilateral diffuse and symmetrical lesions are typical. In DD MR, signal changes on Т1- and Т2-weighted imaging, and FLAIR are polyphasic, and MR signal undergoes various stages. For the whole group of DD in contrast to other disorders with CE, one of the most important and often single feature is a “partial enhancement” phenomenon, in which enhancement has a shape of ring or semi-ring. We believe that this type of CE is pathogenetic for DD, especially in MS, and occurs due to irregular breakdown of BBB on the periphery of demyelinating lesions , in contrast to regular and ring-shaped enhancement seen in the group of malignant gliomas, to ring-shaped enhancement of an abscess capsule, to fungal and parasitogenic disorders.
13.2 Primary Demyelinating Diseases 13.2.1 Multiple Sclerosis MS is a chronic progressive CNS disease with disseminated neurological symptoms and in typical cases, with relapsingremitting course on the initial stage (Adams and Victor 1993). The history of research in this disorder started in 1835, when the great French pathologist J. Kruvelie described “patchy” or “insular” sclerosis. The first classic description was made by J. Charcot in 1866, who characterised the disease as a combination of spastic paraplegia, intention tremor, speech impairment, visual loss, and nystagmus. Since the first decryption, an epoch has passed in the research of the disease. Today, MS is the most studied demyeli-
Chapter 13
nating disorder; however, its aetiology is still not clear. Exogenous factors are probably responsible for the development of the disease, and these factors act because of genetic predisposition. Aetiological hypotheses consider infection, autoimmune reactions to normal myelin, a combination of infectious and autoimmune processes, and toxic and metabolic causes. A lot of evidence suggests viral aetiology in genetically predisposed individuals (Gusev et al. 1997; Zavalishin and Golovkin 2000). However, no pathogen was inoculated either from biopsy or autopsy material. A multifactorial causative theory is the most acknowledged today, according to which, MS develops under a certain combination of exogenous factors in genetically predisposed individuals, and leads to chronic inflammation, autoimmune reactions, and demyelinating lesions in the white matter of CNS. Genetic predisposition remains unproven; however, a strong association of MS with HLA-DR2 class II, and the role of other genes are discussed in combination of different genetic factors in particular. In most cases, MS starts at the age of 20–40 years, in 15% of patients, onset occurs before 20, and in 10%, after 50 years of age. MS incidence is threefold higher in females than in males and is low in children (about 0.3–0.4% of all cases) when it starts in the first decade of life. In 60% of cases, the first symptoms are diplopia and optic neuritis. Among other signs are muscle weakness, paraesthesia, and gait disturbances. With the progression of MS, amelioration of pyramidal signs and pelvic sphincters impairment is observed, as well as cognitive decline and memory loss. Sensory loss is often seen at onset, and pain is not typical and may occur as a rare occasion. There are different clinical forms and courses of MS. The most cases are related to classis Charcot type. Rare clinical forms are hyperkinetic, isolated spinal, and atypical forms of MS (Yakhno and Shtulman et al. 2001), distinguished according to pathological and clinical peculiarities, the distinct nosological entity of which is still a subject of discussion (Devic’s opticomyelitis, Balò’s concentric sclerosis, Schilder disease). The course of the disease is variable, and the following types of MS course are distinguished at present: relapsing–remitting, primary progressive, secondary progressive, and progressive with relapses. In addition, benign MS (when a patient remains functionally active within the first 15 years since the onset, 15–20% of cases) and malignant MS (rapid progression with development of prominent disability within a short time span, 5–10% of cases) are distinguished. In most patients, the relapsing–remitting course is seen (70%), with exacerbations and remissions of multifocal neurological signs. In the early stages; complete recovery may occur after exacerbation; however, the subsequent course of the disease may become progressive. In 10% of cases, the disease is progressive without remissions, and it is called primary progressive MS. In patients with chronic progressive course, more prominent involvement of the spinal cord than that of the brain is seen. In the late stages of the classic variant, severe neurological deficit is present with cognitive decline irrespective to the disease duration (Тоtolyan et al. 2002b). In this group of MS patients, as well as in children with MS older than 5 years, atypical clinical features and MRI data may be observed. Epileptic seizures in children with MS are seen more frequently than in adults.
Demyelinating Diseases of the Central Nervous System
In addition, in children a monosymptomatic disease may be seen as a single episode of a neurological deficit, such as optic neuritis, transverse myelitis, or brainstem syndrome. On autopsy in MS multiple, clear-cut disseminated plaques are present in the white and, rarely, in the grey matter. Despite the common type of distribution of MS plaques in the brain, peculiarities may be seen in individual patients. In the chronic stages, plaques may occupy larger territories of the white matter of cerebral hemispheres. Certain regions of the white matter are more affected for the unknown cause. They are periventricular white matter, optic nerves, brainstem, and spinal cord. Periventricular white matter involvement is typical for MS, but it is not always homogenous. The majority of plaques are located in typical sites, connected probably with subependymal veins (Newcombe et al. 1991; Leng Ten et al. 2002). About 50% of lesions are periventricular and mainly surround the horns of lateral ventricles. The periaqueductal grey matter of brainstem and the bottom of the fourth ventricle are also often affected. Despite this, MS plaques are usually located in the white matter, though some of them are found also in the grey matter (Grossman and McGowan 1998; Scott et al. 2002). Plaques typically undergo acute, subacute stages, and a transformation to gliosis. Largely, plaques are usually oval and have regular contours. Their sizes vary from several millimetres to several centimetres. In the acute stage, plaques are moist and pink; in the subacute stage, they become less vivid and acquire chalky colour, and the number of macrophages within them increases. In the stage of gliosis, they become grey and semitransparent. Cortical plaques are hardly seen largely, except cases when they occupy subcortical white matter. Lesions may correspond to different stages. In the spinal cord, lesions are usually oval with longitudinal orientation along their lengths. Other typical MS features are atrophy of the optic chiasm and optic nerves, of white matter of cerebral hemispheres, of brainstem, and spinal cord. Hydrocephalus occurs in 5–10% of long-term course MS cases. Plaques are usually oval and are located around veins. A vein passes through a plaque along its longitudinal axis. In acute-stage oedema, fragmentation of myelin and formation of myelin “globules” are seen, well detected in stained preparations. Axons are relatively spared, but look swollen. Perivascular lymphocytic infiltrates mainly containing T cells is a typical but not a constant feature. Activated microglial cells are present. With the progression of lesions, lymphocytes are replaced by macrophages with lipid inclusions. Sudanophilic material is seen inside macrophages as well as in the extracellular space. Plaques located within the grey matter do not usually affect neurons. In the chronic stage, a plaque transforms into a focus of gliosis or an “inactive” plaque, in which demyelination is clearly demarcated by a lesion’s margin. Lymphocytes and macrophages are not seen in these plaques. Despite the fact that axons are relatively intact, their number decreases, and they become situated less compactly than in adjacent intact areas (Adams and Victor 1993). Microcysts frequently occur. In some plaques, incomplete destruction of myelin is seen and owing to their irregular margins, they are so-called shadowlike plaques (Poser et al. 1983). Shadow-like plaques are a sign of ongoing remyelination within the lesions. It was shown that
1035
remyelination also occurs in acute lesions; however, myelin recovers incompletely. In chronic shadow-like plaques, demyelination and remyelination proceed simultaneously. In addition to focal brain changes, diffuse changes are also found on autopsy in MS—they are mild histological changes in a largely normal cerebral parenchyma: diffuse gliosis, perivascular inflammation, lipofuscin deposition, sclerotising of veins, and microscopic demyelinating lesions. Identical changes are seen in spinal MS, which confirms diffuse involvement of the CNS in this disorder (Scott et al. 2002). In rare cases, meningeal infiltration with inflammatory cells is seen in subarachnoid spaces. MRI prominently changed approaches to clinical diagnosis of MS. MRI sensitivity in detection of MS lesions markedly exceeds facilities of clinical examination as well as of other neuroimaging techniques (for instance, CT). It should be then noted that MRI specificity in MS diagnosis is not more than 80%, as white matter lesions resembling MS plaques may be found in healthy people, as well as in patients with other disorders—vascular encephalopathy, migraine, lupus erythematosus, chronic fatigue syndrome, diffuse axonal damage after head trauma, vasculitis, Behçet’s disease, Wegener’s granulomatosis, neuroborreliosis, etc. In addition, MRI may be normal in 25% MS patients with confirmed diagnosis (Totolyan et al. 2002a). For these reasons, MR findings cannot be the only criteria for MS diagnosis, and should be considered in complex with clinical signs and results of laboratory investigation. Earlier, attempts to systematise peculiarities of topical location of MS plaques were performed many times to elaborate the so-called MR criteria for MS diagnosis (Fazekas et al. 1988; Barkhof 1997). In 2001, an international panel on diagnosis of MS led by W.I. McDonald incorporated the modified Barkhof criteria into the diagnostic scheme to demonstrate dissemination in space on MRI and to facilitate the diagnosis of MS in patients with clinically isolated syndrome (CIS). (McDonald et al. 2001). The modified Barkhof criteria require at least three of the following four features: 1. One gadolinium-enhancing lesion or nine T2 hyperintense lesions if gadolinium-enhancing lesions are not present 2. At least one infratentorial lesion 3. At least one juxtacortical lesion 4. At least three periventricular lesions When three out of four Barkhof parameters are not fulfilled, then the presence of two or more subclinical lesions consistent with MS on brain MRI plus CSF detection of oligoclonal bands are required to demonstrate dissemination in space. In 2005, a panel of experts revised the McDonald criteria to simplify the criteria for dissemination in time. There are two ways to show dissemination in time using imaging: 1. Detection of gadolinium enhancement at least 3 months after the onset of initial clinical event, if not at the site corresponding to the initial event 2. Detection of a new T2 lesion on a brain MRI if it appears at any time compared with a reference scan done at least 30 days after the onset of initial clinical event
1036
Chapter 13
However, even with criteria that has been revised many times in different years, specificity of MRI in MS diagnosis still comprises not more than 80% of cases (Totolyan et al. 2002a), which requires further studies with novel MRI techniques. At present series MR scans with CE in a follow-up manner remain an important technique in MS diagnosis as well as in differential diagnosis with other disorders. MS plaques greatly resemble lesions typical for many other disorders of the white matter. They are disseminated and have different sizes with hyperintense signal on images with prolonged TR. Routine MRI is sensitive to MS lesions, but it does not differentiate time spans of plaques formation and histopathology ongoing within them (demyelination, transient inflammation, remyelination). MS lesions are often located in the periventricular white matter, internal capsules, corpus callosum, pons, cerebral, and cerebellar peduncles. However, they may be located within the myelinated white matter and within grey matter (Figs. 13.1, 13.2). MS plaques located in the periventricular white matter are usually oval and oriented rectangularly to the lateral ventricles—the so-called Dawson fingers. MS plaques located in the periventricular white matter are difficult to assess, with images having prolonged ТR/ТЕ, in which CSF is hyperintense. On proton density-weighted imaging (long TR/short ТЕ) and FLAIR images, these plaques are better seen. Noteworthy is that the MRI picture of MS
plaques is variable. The anatomic distribution of plaques is not a crucial aspect of diagnosis, as “rare” locations are ubiquitously seen. Corpus callosum is the structure most apt to develop demyelinating lesions, as it is intimately connected with walls of the lateral ventricles and small vessels that perforate it. Several authors reveal hyperintense lesions on T2weighted imaging in the inferior portions of corpus callosum (the callososeptal region) in 93% of MS patients (Grossman et al. 1999; Evangelou et al. 2002). Sagittal T1-weighted imaging visualises these lesions quite well as areas of hypointense signal or merely as thinning of the inferior portions of corpus callosum. Despite that it was suggested earlier that the appearance of these callososeptal lesions (the Venus necklace) is MS specific, further evidence showed that ischaemic lesions may appear just the same. Temporal evolution of MS plaques is characteristic for MS, which is reflected on MRI. Not only size, but also signal characteristics of MS plaques may change, and thus it is not possible to judge the time of occurrence of these lesions in any separately taken image. Primary MS plaques may dwindle in size due to reduction of perifocal oedema as well as due to remyelination, and may leave smaller plaques after (Fig. 13.3). In exacerbations, reactivation of an old lesion may happen, it may increase in size, and that usually correlates with increase in the neurological deficit.
Fig. 13.1a–d Neuroimaging semiotics of focal lesions in MS. Т2-weighted imaging: a le-
sion in the middle left cerebellar peduncle (a), a lesion in the periventricular white matter adjacent to lateral wall of the right lateral ventricle (b), subcortical focus of demyelination in the right frontal lobe and a smaller plaque in the deep white matter of the left parietal lobe (c), and plaques in corpus callosum (d). All lesions are indicated by arrows
Demyelinating Diseases of the Central Nervous System
1037
Fig. 13.2a–c Multiple MS plaques in brainstem and cerebellum. Т2-weighted imaging (a, b) and a series of axial FLAIR (c) images
Fig. 13.3a–c Regression of a focus of demyelination in the middle right cerebellar peduncle: acute plaque on Т2-weighted imaging (a) and
Т1-weighted imaging (b). c The same lesion 6 months later (T2-weighted imaging), marked reduction of size and signal intensity of focus of demyelination
Many authors emphasise that MR picture correlates with type of MS course (primary progressive, secondary progressive, relapsing—remitting, etc.) (Тоtolyan et al. 2002b; Pronin et al. 2003). The number and the total plaque load are different in different types of MS course, and rate of plaque load increase, development of secondary gliosis, and diffuse neurodegeneration and atrophy also follow this correlation. In patients with favourable relapsing–remitting course, when exacerbations occur not more than one per year, T2weighted imaging reveals hyperintense lesions of a few to 10–15 mm in size. In most cases, MR signal of these lesions is homogenous, and lesions have relatively clear contours with the intact white matter (Fig. 13.4). The shape of plaques may vary from irregular to round. Round-shaped lesions are more frequently encountered and are seen predominantly in
the periventricular white matter and centrum semiovale, and less frequently in corpus callosum and subcortical structures. Solitary plaques may be located in brainstem and a cerebellar hemisphere. On T1-weighted imaging in relapsing–remitting MS, in most cases, plaques are not seen; only several foci can be found, which have mildly hypointense MR signal. In these patients, infratentorial lesions are not visualised on T1-weighted imaging. Assessment of follow-up MR scans in patients with relapsing–remitting MS within the period of 24 months since the first scanning does not reveal such additional changes in brain tissue as an increase in old plaques size or increase in brain atrophy. Solitary additional lesions may only appear. In the secondary progressive MS course, with clinically significant exacerbations, gradual and inevitable progression of the neurological deficit and short periods of stabilisation,
1038
Chapter 13
Fig. 13.4a,b Remitting relapsing MS. MR
T2-weighted imaging (a) and 2 years later (b); a single new plaque is revealed (arrow)
T2-weighted imaging usually reveals hyperintense lesions of different shape up to 25 mm in size. Brainstem, cerebellar hemispheres, and supratentorial structures are affected. In several cases, the square of the affected area in pons on axial T2-weighted imaging may occupy up to 30% of its transverse section. Marked diffuse dilatation of convex subarachnoid spaces of supra- and infratentorial location is seen. On T1weighted imaging in patients with this type of MS course, markedly hypointense plaques are typical. These changes predominate in the majority of supratentorially located plaques (in corpus callosum, in the periventricular white matter of cerebral hemispheres). Less often, hypointense plaques are revealed in the cerebellar hemispheres and in brainstem. Assessment of follow-up MR scans in patients with secondary progressive MS demonstrated that gradual increase of changes of brain tissue around certain closely located lesions occurs
with formation of large areas of pathological MR signal—a phenomenon of “confluent plaques”. These changes are clearly seen on T2-weighted imaging, but are also seen on T1-weighted imaging (Fig. 13.5). Simultaneous occurrence of novel hyperintense plaques of different location could be found on T2weighted imaging. In patients with secondary progressive MS, large areas hyperintense on T2-weighted imaging and markedly hypointense on T1-weighted imaging are typical. In addition, these changes are expanded and occupy supra- as well as infratentorial brain tissue. Follow-up scans reveal gradual increase of total plaque burden. The number of infratentorial plaques increases, the size of certain plaques grows, confluent areas of pathological MR signal form, cerebral atrophy progresses, the relative contrasting of plaques on T2-weighted imaging increases, and these changes correlate with pathological findings.
Fig. 13.5a–c Secondary progressive MS. MRI with a 1-year interval: Т2-weighted imaging at the level of the lateral ventricles bodies—gradual confluence of separate plaques backwards to the lateral ventricles bodies with formation of a united area of pathological MR signal hyperintensity. Increased brain atrophy was found
Demyelinating Diseases of the Central Nervous System
Fig. 13.6 Relapsing–remitting multiple sclerosis: MRI simultaneously reveals enhancing (“active”) and nonenhancing (“inactive”) foci of demyelination, which is typical for MS and rules out other conditions. Axial T1-weighted imaging with CE (a nonenhancing lesion is pointed by arrow)
Gadolinium enhancement of MS lesions may reflect the transient BBB impairment. CE is applied in MS to reveal more or less specific changes within the picture of multiple hyperintense lesions on T2-weighted imaging—it is known that simultaneous identification of enhancing and nonenhancing lesions is typical for MS (Fig. 13.6) and allows ruling out other conditions. In addition, a transformation of these enhancing and nonenhancing lesions in time is also typical for MS more than for other pathologies. Several types of CE of MS plaques were described (diffuse, ring-shaped, and partial) (Pronin et al. 2003). In the diffuse type, the total plaque volume seen previously on T2-weighted imaging enhances. This type is typical for multiple small plaques several millimetres in diameter. Ring-shaped enhancement is seen when contrast medium accumulates in the peripheral parts of larger demyelinating lesions in a shape of ring. The size of these lesions approaches 1 cm and larger. Such a type of CE is seen in plaques with perifocal oedema, revealed on T2-weighted imaging or DWI. Partial type of CE is, to our opinion, the most typical for demyelinating lesions in MS as a whole, and manifests as partial accumulation of contrast agent within the area of pathologically changed MR signal revealed on T2-weighted imaging. It is feasible to note the semi-ring or half-moon type of CE in MS plaques, when signal increase on postcontrast T1-weighted imaging is seen only in the peripheral area of plaque without locking, as opposed to ring-shaped CE (Fig. 13.7). This type of CE is explained by heterogeneous impairment of BBB on border of a demyelinating lesion, which is due to inconstant course of the autoimmune process. This semi-ring or partial type of CE is one of the differential diagnostic criteria and one of the most typical features of MS that allow to differentiate it from mass lesions with “crown-effect” (complete ring-shaped
1039
enhancement), such as in metastasis, abscess, parasite, tumour cyst, and tuberculoma. Several authors connect the existence of several type of CE with freshness of certain lesions. Thus, R. Grossman et al. (2002) compared MRI with CE and immunohistochemical findings, and concluded that only nodular (diffuse) type of CE stands for newly MS lesions, whereas semi-ring CE is a feature of secondary process, as it reflects inflammation around an old lesion, especially if such a CE is seen on a plaque periphery, looking hypointense on T1-weighted imaging before CE (Fig. 13.8). We regard this opinion true, as in patients with exacerbation of MS, it is often possible to reveal CE in plaques that have been hypointense on T1-weighted imaging and showed no CE on previous MR scans (reactivation of old plaques). A perspective technique is bolus injection of contrast medium with subsequent assessment of CE. Several authors revealed marked differences in the dynamics of CE in MS and glial tumours (Pronin et al. 2003), which confirms existence of different mechanisms of BBB alteration in these disorders. In MS, BBB is not so severely affected as in malignant gliomas, so CE occurs not right after it was injected, but after a delay. Optimal time when CE occurs in MS is 20–30 min after injection of contrast medium. Mass demyelinating lesions (over 2–3 сm) are typical for tumour-like MS, which is characterised by severe neurological deficit that corresponds to the anatomical location of the lesion. In this conditionally distinguished form of MS, a single large pseudotumoral lesion is revealed surrounded by other smaller lesions. It is more difficult to make diagnosis having such a lesion resembling a glial tumour, if no additional MR changes are present. To avoid stereotactic biopsy, thorough clinical analysis should be made as well as CSF tests (Shalmon et al. 2000). The most of these cases present inflammatory demyelinating pseudotumoral syndrome (see below) or focal leukoencephalitis. Tumour-like MS is typical for children and young people (Scott et al. 2002; Тоtolyan et al. 2002b; Kornienko et al. 2003). With time, partial reduction of a large lesion may occur with formation of cyst and gliosis on its site (Fig. 13.9). Extremely rare, mild, diffuse hyperintensity of the white matter (often in centrum semiovale, optic radiation and cerebellar peduncles) is seen on Т2-weighted imaging and Т2FLAIR images without focal signal changes (Fig. 13.10) in the brain and spinal cord in patient with otherwise-typical MS according to clinical picture. It is the so-called diffuse type of MS (Scott et al. 2002). During 10 years of neuroimaging studies, we observed only two cases with such MR picture, in clinically and laboratory-confirmed MS. In such cases, if a clinician more reflects to MR findings, then for many years the patient will be followed with wrong diagnosis. Increase of hypointensity of MS lesion on T1-weighted imaging correlates with progression of demyelination and axonal loss (Prineals et al. 1985; Grossman and McGowan 1998). Signal intensity of these lesions approaches that of the CSF and they are described as “black holes”. Their appearance correlates with progression of disability (Gusev et al. 1997). MS lesions on T1-weighted imaging without CE may show ring-
1040
Chapter 13
Fig. 13.7a,b Patterns of CE in active lesions
of MS: diffuse and ring-shaped types of enhancement (a); partial type, semi-ring enhancement (b)
Demyelinating Diseases of the Central Nervous System
1041
Fig. 13.8a–e Reactivation of an old MS plaque. Т2-weighted imaging (a), Т1weighted imaging (b), FLAIR (c), and Т1-weighted imaging (d) with CE. A semiring enhancement is noted on borders of an “old” plaque (arrow). Smaller inactive plaques and new active foci of demyelination with diffuse enhancement are revealed. e DWI: the signal of foci is high due to Т2 effect caused by oedema in active plaques
Fig. 13.9a–f Tumour-like MS. Axial (a) and sagittal (b) Т2-weighted imaging. MRI 2 years later: Т2-weighted imaging (c) and Т1-weighted imaging (d). A large (4 cm in diameter) focus of demyelination in the anterior portions of the left frontal lobe is revealed, not seen before.
Slices on the same level on MRI 1 year later (e,f): marked regression of a large plaque with gliosis and cystic transformation were observed
1042
Chapter 13
Fig. 13.10a–c Diffuse MS. FLAIR images reveal hardly visible symmetrical hyperintensity (arrows) in the middle cerebellar peduncles (a), centrum semiovale, and the deep white matter of the cerebral hemispheres (b,c). No focal signal changes are seen
shaped CE inside or on the periphery, which is suggestive for presence of paramagnetic material and free oxygen species in the macrophagal layer, which constitutes a margin of an acute plaque. Diffuse atrophy is often revealed during the disease progression. Iron deposits in thalami, basal ganglia, cerebral cortex, and the subcortical white matter may be revealed. CE of dura mater and haemorrhagic foci are rarely reported in MS too. To standardise MRI diagnosis of MS and improvement of the results compatibility we propose the following brain neuroimaging protocol for MS: T2-weighted imaging (rapid spin Axial, TR = 2,000–4,500, echo or spin echo T2- and proton TE = 20/80–100 ms, slice density-weighted imaging) thickness 5 mm, with minimal interslice gaps Т1-weighted imaging
Parameters depend on type of MRI
FLAIR
Parameters depend on type of MRI
Т1-weighted imaging with CE Т1-weighted imaging with magnetisation transfer with CE
If present in an MRI scanner software
All studies should be done in the same planar regimen, preferably in axial, on the same levels, with visualisation of all the brain from brain base to convex. Sagittal projection may be additionally used and it is optimal when T2-weighted imaging and FLAIR images are made. MS in children resembles adult MS in many features. However, several peculiarities of neuroimaging picture exist in children (Тоtolyan et al. 2002b). Several authors believe that focal lesions are characterised by less signal changes on T1weighted imaging than in adults. In addition, beginning in the
early stages, diffuse demyelination of the deep white matter is seen with rapid involvement of subcortical fibres (Fig. 13.11). Tumour-like forms, with large demyelinating lesions predominate in children. Acute demyelinating lesions in children in contrast to adults including those that are hypointense on T1weighted imaging may be completely reversible. Brain atrophy does not develop in children for a long time due to large reparative potential of the CNS. If MS is suspected in a child, then other focal lesions should be considered for differential diagnosis (vasculitis, neuroinfection, several mitochondrial encephalopathies etc.). Optic neuritis is often found in MS patients on autopsy; however, routine spin echo sequences even with high resolution often do not reveal optic nerve involvement even if it is clinically present. Other PS including FLAIR and rapid spin echo with fat signal attenuation (T1-Fat-suppression-weighted imaging) are more sensitive in diagnosis of optic neuritis. They reveal abnormal hyperintensity in the affected optic nerves (Fig. 13.12a–c). Т2-weighted imaging with rapid spin echo with high resolution and fat signal attenuation, аs well as Т1-weighted imaging after CE with high resolution, also often reveal heterogeneity of signal intensity within optic nerves. Identification of lesions in optic nerves if optic neuritis signs are clinically evident is, of course, of relative importance. Optic neuritis is the first MS sign in 20% of cases and develops with the progression of MS in 50% of cases. In 45–80% of patients with optic neuritis, overt MS further develops within the 5 years since the onset. Most clinicians believe that in patients with isolated optic neuritis, MRI is necessary to exclude other rare causes of optic neuritis and to identify clinically silent lesions in the brain to confirm the diagnosis of MS. Treatment of optic neuritis decreases risk of overt MS development from 36 to 16%, but only in patients with other lesions in the brain during the first exacerbation (Scott et al. 2002). Thus, despite the relative significance of imaging confirmation of optic nerves involvement, MRI is important in MS course
Demyelinating Diseases of the Central Nervous System
Fig. 13.11a–i Childhood MS. Axial Т2-weighted imaging (a–c), T1weighted imaging (d,e). On sagittal Т2-weighted imaging (f), diffuse and focal involvement of corpus callosum and a foci of demyelina-
1043
tion in the pons. A series of axial MRI on FLAIR images (g). T1weighted imaging after CE (h,i): there are many small foci of demyelination in white matter with enhancement
1044
Chapter 13
Fig. 13.12a–e Clinical isolated syndrome.
Case 1. Focus of demyelination in optic nerve (optic neuritis). T2-weighted imaging with fat saturation (a), Т1-weighted imaging with CE in axial (b) and parallel to optic nerve projections (c). Case 2. A focus of demyelination in the right trigeminal nerve root on FLAIR images with hyperintensity and local thickening of the nerve (d,e). Plaques are pointed by arrows
prognosis for making correct treatment decisions. Everything mentioned above about optic nerves is true for other cranial nerves, such as trigeminal, oculomotor in which demyelinating lesions may also be found in MS (Fig. 13.12c,d). Frequently, MRI reveals concomitant brain disorders in MS patients. We met combinations of MS with arachnoid cysts, hydrocephalus, or variants of the ventricular system development (Fig. 13.13), brain tumours (gliomas, meningiomas, neurinomas (Fig. 13.14), lymphomas, pituitary adenoma (Fig. 13.15), vascular pathology, cavernous (Fig. 13.16), and frequently, venous angiomas (Fig. 13.17). Probably, the prevalence of such coincident cases increases when CE is used, which is more frequently done in MS than in other disorders. It may be supposed that earlier described haemorrhagic lesions in MS patients (except those in Hurst’s disease) were cavernous angiomas with old haemorrhages. In addition to the study of macroscopic picture of MS, a quantitative analysis of relaxation times, analysis of magnetisation transfer ration, diffusion and proton MRS studies of normal-appearing white matter (NAWM) are also applied. These data may reflect mild histological changes which pathologists describe (a microscopic picture of MS) and may
confirm that MS is a diffuse process. These quantitative techniques help us to perceive microstructural changes in MS plaques, to show MS on the microscopic level not seen by routine MRI and may document irreversibility of the disease (Grossman and McGowan 1998). 1 H MRS was performed by many researchers in MS and on animal models of demyelinating disorders. This technique allows assessing biochemical changes within MS lesions, to distinguish oedema from zones of demyelination and/or incomplete remyelination (Miller et al. 1998). On MRS in chronic plaques as well as in NAWM decrease of the NAA peak is seen. Decrease of NAA peak in MS was regarded a marker of secondary neuronal loss after primary demyelination. Hence, it is a marker of irreversibility of the brain tissue damage. Other authors suggest that presence of free lipids and cholesterol, which are products of myelin degradation was associated with proton spectra abnormalities (Scott et al. 2002). MRS of active contrast-enhancing lesions reveals amino acids, lipids and other products of myelin degradation. 1 H МRS findings in demyelinating process depend on time of examination (Loevner and Grossman 1995). In the early stages of demyelinating process relative elevation of Cho
Demyelinating Diseases of the Central Nervous System
1045
Fig. 13.13a–d MS with concomitant abnormalities of CSF development. An arachnoid cyst of the right Sylvian fissure (a,b). Septum pellucidum cyst (the fifth ventricle) on Т2weighted imaging (c,d)
Fig. 13.14a–c MS and the right trigeminal nerve neurinoma. Т2-weighted imaging (a), FLAIR (b), and coronal Т2-weighted imaging (c). Along with multiple foci of demyelination in the periventricular white matter and pons, a tumour of sensory portion of the right trigeminal nerve is detected (neurinoma)
1046
Chapter 13
Fig. 13.15a–f MS in an adult with clinical signs of mild acromegaly. There are pituitary tumour (a Т1-weighted imaging with CE) and plaques
of demyelination in white matter on FLAIR images (b–f)
Fig. 13.16a–c Cavernous angioma of the left frontoparietal region in MS patient. Т2-weighted imaging (a), Т1-weighted imaging (b), and
FLAIR images (c). Cavernoma has hypointense signal in contrast to foci of demyelination in Т2 and FLAIR images along the contour of a mass lesion due to haemosiderin deposits (arrow)
Demyelinating Diseases of the Central Nervous System
1047
Fig. 13.17a,b Venous angioma of the deep left subcortical region in MS patient. Т2weighted imaging (a), Т1-weighted imaging with CE (b). Multiple pathologically enlarges and enhanced veins draining into the venous plexus of the left lateral ventricle are revealed
peak, occurrence of Lac peak, and decrease of NAA peak with changes in peak ratio with the reference Cr peak are typical. Elevation of Cho peak occurs due to destruction of cellular membrane and axons in areas of active demyelination. Increase of Lac peak is also a marker of tissue destruction, cytotoxic oedema, and anaerobic glycolysis with accumulation of lactate. Decrease of NAA peak is due to decrease of neuronal mass in affected area. Increase of mI peak is not typical for acute demyelinating lesions and is seen only in chronic demyelinating diseases due to gliosis (Fig. 13.18) However, separately taken MRS data are not sufficient to make differentiation between demyelinating lesions and glial tumours (for instance, anaplastic astrocytomas), which have resembling spectra. In conclusion, these data suggest that MRS may reflect stages of histopathological changes in MS, to follow the history of the disease and to monitor treatment efficacy. MT is applied in MRI of MS patients to assess MS plaques and to rule out another silent pathology of normally appearing brain parenchyma (Loevner 1995). Implication of this PS easily performed on a conventional scanner assesses the dif-
ference between relaxation times of immobile water protons temporarily bound with macromolecules, and solvent molecules. That is based on concept that demyelination leads to increase of free water (i.е. reduction of “boundary” fraction of water) to compare with the myelinated white matter or intact but oedematous tissue. Application of out-of-resonance saturation pulse leads to selective attenuation of bound water and to decrease of signal of the brain tissue. This property of MT found its implication in imaging of small and hardly enhancing MS plaques in routine T1 sequences (Fig. 13.19). Application of MT provides the identical detection capacity of active MS lesions as provided by standard dosage and triple dose of contrast agent, but without out-of-resonance pulse sequence. The ratio of MT is calculated (MTR), and relative extent of saturation of different brain regions is compared. Many authors showed that this ratio is higher in the normal mature myelinated white matter than in grey matter (i.e. decrease of signal is more prominent during saturation for the normal white matter). Assessing lesions of experimental allergic encephalitis with early oedema mild changes of MTR were
Fig. 13.18a–c MRS of plaque in patient with MS. Spectra of an acute plaque intensively accumulating contrast medium (a), spectra of the same focus (b) 2 weeks later (subacute plaque). c Chronic focus of demyelination without contrast medium accumulation
1048
Chapter 13
Fig. 13.19a–c Magnetisation transfer technique (МТ). Т1-weighted imaging before CE (a). Т2-weighted imaging with CE (b) reveals a single focus of accumulation of contrast medium. МТ (c) better visualises an active plaque (arrow)
revealed in comparison to normal white matter; however, marked decrease of MTR was found in demyelinating lesions in human MS (Prineals 1985). One study showed that MTR was more decreased in enhancing than in nonenhancing lesions. This МТR decrease correlated with MRS findings that identified active demyelination. The role of MTR in demyelinating disorders still needs further research; however, MTR is planned to be implemented in treatment efficacy assessment. Diffusion-weighted and diffusion tensor MRI gives quantitative data about brain tissue structure basing on parameters of water molecules motion. In this technique sensitive to water diffusion, a pair of gradient pulses before and after 180° frequency pulse of EPI-spin echo sequence is used (Ciccarelli et al. 2001). It is thought that specifically organised structure of a mature (myelinated) tissue leads to diffusion anisotropy (i.e. to limitation of water motion in a certain direction) to compare with the grey matter. Despite that it is still unknown whether myelin is a source of anisotropy, it is reported that demyelinating lesions are characterised by abnormal diffusion. One of the studies of experimental allergic encephalitis in primates demonstrated that white matter lesions were identified by DWI earlier than on MRI by spin echo technique. It was shown that DWI may differentiate acute and chronic plaques. In the hyperacute period of demyelination when changes on T2-weighted imaging are minimal or absent, DWI registers high signal due to cytotoxic oedema and ACD value decreases. In the acute period, decrease of diffusion velocity in the active demyelinating lesions is explained by cellular infiltration of demyelinating lesions (by lymphocytes and macrophages) and by tissue destruction or temporary decrease of blood flow in this area due to inflammatory process. Ten to 20 days later, normalisation of the ADC value in demyeli-
nating lesions occurs, and then ADC starts to increase due to myelin and axonal destruction and expansion of the extracellular space. Further, as MS plaque forms, the signal on DWI decreases, and ADC increases as myelin and axonal destruction progress. In chronic inactive MS lesions, high ADC and low DWI signal are registered (Fig. 13.20). Assessment of a complete DWI picture in MS also differentiates visible lesions from silent, and reveals differences in clinical subgroups of patients. Other researches also revealed correlations between DWI parameters in normal brain parenchyma, clinical signs, and level of disability (Nusbaum et al. 2000). Possibly, in the not-to-distant future, MT and DWI will take a leading place in brain tissue assessment in MS patients. In white matter, molecular movement is not the same in the directions due to the structural barriers within the fibre tracts (so-called anisotropy). It is leads to an orientation-dependent diffusion property of the water molecules. Diffusion tensor imaging (DTI) is a new technique that allows estimating with anisotropy. DTI is acquired with diffusion weighting gradients in at least six directions, which allows for the construction of a tensor. The tensor can be used to produce images of both mean diffusivity and fractional anisotropy. Therefore, DTI may provide information about tissue microstructure and architecture of the brain and in turn, constitutes a proved and effective quantitative method for evaluating tissue integrity at a molecular level (Filippi et al. 2001; Lin et al. 2007). Moreover this information provided by fractional anisotropy can serve as source for fiber tracts of white matter reconstruction—so-called tractography (Fig. 13.21). CT, MR perfusion studies may also be helpful in MS research as they may detect parameters of tissue perfusion in the “normally appearing” and in the affected white and grey
Demyelinating Diseases of the Central Nervous System
matter. This study reveals differences in perfusion within acute (active) and chronic (inactive) MS plaques (Fig. 13.22). The register of disorders that should be differentiated with MS in their neurological manifestations and MR findings of focal white matter involvement is rather wide. In children, MS should be differentiated from leukodystrophies and other toxic and metabolic encephalopathies, for the whole group of which diffuse symmetrical changes of MR signal are typical without CE. Also in this age group, MS should be differentiated from ischaemic changes, such as delay in myelination of terminal zones, hypoxic encephalopathy, and periventricular leukomalacia. In adults, especially in MS onset after the age of 40 years, frequent difficulties occur when it is required to perform differential diagnosis with hypoxic encephalopathies (chronic ischaemic brain disease, Binswanger’s disease etc). The latter as well as MS are characterised by focal and diffuse changes in the white matter of cerebral hemispheres, due to atrophic demyelination caused by atherosclerosis of arterioles and by chronic hypoxia. These changes are asymmetrical and localise in the deep as well in the subcortical white matter; they usually are accompanied by dilatation of the subarachnoid spaces and the ventricular system due to cerebral atrophy. The following features are helpful to distinguish them from demyelinating disorders: frequent (in contrast to demyelinating disorders) detection of identical focal changes in basal ganglia, lacunar
1049
strokes, multiple dilatated perivascular Robin-Virchow spaces, areas of encephalomalacia (Figs. 13.23, 13.24). Frequently in these disorders a diffuse signal hyperintensity is seen on Т2weighted imaging and FLAIR, encircling the lateral ventricle, which is called leukoareosis. These changes are explained by destruction of ependyma, exudation of CSF from the ventricles into the periventricular white matter and development of gliosis herein. In MS, such changes of ependyma and the periventricular white matter may be seen only in the late stages of disease (Fig. 13.25). CE in absence of ischaemic changes (stroke) is not typical for hypoxic encephalopathies. If MS is clinically suspected after the age of 40 in a patient with MR features of vascular encephalopathy, then it is difficult to confirm MS. Follow-up MRI with CE is required. Small numbers of tiny hyperintense lesions on T2-weighted imaging predominantly in the deep and subcortical white matter of cerebral hemispheres may be seen in migraine. They are caused by crisis vasculopathy of the small arterioles. Lesions in migraine are small (not larger than 0.5 сm), they are not found in the infratentorial structures, and they are not enhancing (Fig. 13.26). Several leukoencephalitis require differential diagnosis with MS, especially those caused by cytomegalovirus and several other herpes viruses (Fig. 13.27). The latter are characterised by a nonspecific focal white matter involvement, more often supratentorially and less often in cerebellum. In cases of mul-
Fig. 13.20a,b DWI in MS. Acute focus of demyelination in the cerebellar peduncle is hyperintense on DWI due to cytotoxic oedema (a). The
same lesion 2 weeks later after corticosteroid treatment—decrease of signal of DWI is noted (b)
1050
Fig. 13.21a–i Clincially isolated syndrome in a 30-year-old woman. Two foci of demyelination in right frontal lobe were found on FLAIR images (a–c) with absence of CE. Fractional anisotropy map
Chapter 13
(d) shows the area of decrease anisotropy in plaque of MS (arrow). MR tractography (e–i) demonstrates partially disorganisation and dislocation white matter pathways in placement of plaque
Demyelinating Diseases of the Central Nervous System
Fig. 13.22a–f Tumour-like MS in adult. T2-weighted imaging (a–c) demonstrate four lesions in sub- and supratentorial locations. The biggest one is in the left parietal lobe. T1-weighted imaging with CE
1051
(d): there is semi-ring pattern of contrast medium accumulation. CBV (e) and CBF (f) maps based on CT perfusion show minimally increased parameters of blood volume and flow into enhanced area
Fig. 13.23a–c Chronic ischaemic brain disease. Т2-weighted imaging (a), Т1-weighted imaging (b), and FLAIR (c) images. Multiple small foci
of vascular demyelination in the deep and subcortical white matter of cerebrum
1052
Chapter 13
Fig. 13.24a–c Multiple dilated perivascular spaces of Robin-Virchow in a patient with arterial hypertension without neurological signs.
Axial Т2-weighted imaging (a) and Т1-weighted imaging (b), and coronal Т1-weighted imaging (c). Perivascular spaces are pulled along venules of pathways
Fig. 13.25a–c Ventriculomegaly due to secondary atrophy in a patient with long history of MS with gliosis in the periventricular white matter (leukoareosis). Т1-weighted imaging (a) and FLAIR (b,c) at the level of lateral ventricles
Demyelinating Diseases of the Central Nervous System
1053
Fig. 13.26 Focal changes in the white matter of a patient with clinical signs of migraine. FLAIR images reveals nonspecific small, hyperintense foci in the white matter of cerebral hemispheres
Fig. 13.27a,b Focal leukoencephalitis caused by varicella zoster virus (VZ encephalitis). The affected area consists of small confluent foci in
the left posterior frontal region and has a heterogeneously hyperintense signal on Т2-weighted imaging (a) and FLAIR (b)
1054
tiple lesions, the differential diagnosis with MS by MRI is often impossible and requires laboratory tests to identify virus or specific antibodies in blood. MS should be distinguished from various autoimmune disorders—several connective tissue disorders (lupus erythematosus [LE] or nodular periarteritis) and other vasculitis, Lyme disease (Lobzin et al. 1992), neurosarcoidosis, Behçet’s disease, Wegener’s granulomatosis, chronic fatigue syndrome, and several even more rare disorders. MR findings in these disorders are caused by vasculitis or multifocal vasculopathy and in most cases, correspond to the following variants: small multifocal lesions in the white matter with typical periventricular, subcortical, or combined location (however, large lesions may be occasionally revealed); multifocal and diffuse leukoencephalopathy; and combined multifocal involvement of the white and the grey matter. In vasculitis, lesions have various sizes depending on affected arteries. Thus, if large magistral head or cervical arteries are affected, then granulomatous process develops in their walls with after thrombosis and stenosis (for instance, in nonspecific aorto-arteritis), ischaemic strokes are typically revealed within the affected artery territory. In this case, lesions are large, but their number is low, a single lesion may also be revealed, and hemispheric location is typical. More difficult is to differentiate MS with vasculitis and vasculopathies of small and especially middle calibre (LE, Behçet’s disease, Wegener’s granulomatosis etc.). Such lesions may mimic MS. One should remember that all vasculitides are monophasic disorders, which is why in the acute stage, CE is seen in all the lesions that have been revealed on T2-weighted imaging before CE. After recovery, all lesions stop to show CE. In MS, lesions are disseminated in time what was above mentioned. It is hard to distinguish a picture specific to any of vasculitides according to reports and our own experience, except for a few cases of sarcoidosis, in which apart from parenchymal changes granulomatous involvement of meninges is seen with typical thickening after CE (see Chap. 11). More relevant is the heterogeneity of MR features of these disorders and to use appropriate additional tests to confirm the diagnosis (skin tests, serology, CSF tests, etc.). In neurotrauma, some pathological changes in the brain may resemble that seen in MS. Usually that takes place in brain concussion, but may be seen in severe head trauma as well if lesions are small focal, or diffuse and focal as in diffuse axonal injury (DAI). Lesions of DAP often locate in the corpus callosum, its splenium, in midbrain, and the pons and may vary in size, often not more then 1–3 сm. They differ from MS plaques and other lesions by a haemorrhagic component better seen in Т2* gradient echo. However that occurs only soon after trauma when the appropriate history speaks about the cause. In the distant period of head trauma, correct diagnosis is facilitated by such signs as absence of CE of DAI lesions, absence of surrounding perifocal oedema, and often seen transformation into microcysts. Radiation exposure. After local brain radiation for tumour, a lesion occurs in the cerebral white matter, which topically corresponds to the site of radiation, and usually it occurs in a delayed period (several months after therapy or up to a
Chapter 13
year). The central area of a lesion is an radiation necrosis— necrotic changes are identified on MRI in the site of brain tissue decomposition and perifocal postradiation changes (oedema and demyelination) having hyperintense signal on Т2-weighted imaging, which may grow with time and cause mass effect. When thick areas of caseous necrosis form, DWI registers hyperintense signal pathognomonic for radiation necrosis. CE is often seen on the periphery of necrosis, which repeats the pattern of cerebral gyri subcortically under the cortex which appears normal. On MRS reduction of all normal metabolites is observed within the area of necrosis with high “dead” Lac peak. Differential diagnosis of MS should be made with brain metastases (МТS), primary or secondary multiple CNS lymphoma, and several parasitogenic disorders, such as multiple cysticercosis. In multiple metastatic or parasitogenic involvement, small size of lesions location of the pathological changes should be first of all taken into account, and this distinguishes them from MS. Metastases affect meninges and ependymal layer of the ventricular system, which is not seen in MS. In addition, MTS are characterised by a homogenous ring-shaped CE with simultaneous enhancement of all lesions, and there is no semi-ring type of CE (Figs. 13.28–13.30). In solitary and large demyelinating lesions, especially in atypical MS forms, differential diagnosis should be made from glioma or with ischaemic stroke (see below). The study of the spinal cord in MS is performed under the following circumstances: appropriate neurological signs are present, brain MRI does not ascertain the diagnosis; the follow-up assessment assumes lesions in the spinal cord. Usually MS plaques in the spinal cord are found along with those in the brain. However, in 5–24% of cases, they may be isolated (Scott et al. 2002). If a spinal lesion suggestive for MS is found, then brain MRI should be performed to verify the generalised character of the disorder. Normal brain MRI in this case does not exclude MS. The majority of spinal MS lesions are located at the cervical level, which is confirmed by autopsy studies. In the progressive character of the disease and marked disability, generalised spinal cord atrophy is often seen. On axial T2weighted imaging typically peripheral location of MS plaques is identified (predominantly in the dorsolateral portions of the spinal cord), where pial veins are close to the white matter (Fig. 13.31). Combined involvement of the spinal white and the grey matter with plaques may be seen. Acute spinal MS lesions produce CE (Fig. 13.32). It depends on BBB condition and the period of disease in which the study was done. Enhancing MS lesions are hardly distinguishable from tumours and inflammatory lesions in the spinal cord, especially when the latter is enlarged due to oedema. Repeated MRI is required to confirm the diagnosis, especially if brain MRI is normal. Fast spin echo (FSE) is a routine technique for assessment of spinal MS lesions; however, it leaves unrecognised mild pathological changes (Miller et al. 1998). Comparison of FLAIR and FSE in detection of MS lesions on the cervical level showed that FLAIR is more informative. Gradient echo should not be applied for spinal MS plaques diagnosis, as it is less sensitive to intraparenchymal spinal lesions than spin echo is. Despite its high sensitivity in cerebral lesions, FAST-
Demyelinating Diseases of the Central Nervous System
1055
Fig. 13.28a–d Active stage of MS with involvement of brainstem and cerebellum. Series Т2-weighted imaging (a) and Т1-weighted imaging (b), FLAIR (c), and Т1 with CE (d). Demyelinating lesions are revealed with (active plaque) and without (inactive plaque) enhancement
1056
Chapter 13
Fig. 13.29a–c Multiple brain metastases. Т1-weighted imaging with CE: axial (a), sagittal (b), and coronal (c) projections. All pathological
lesions enhance in the shape of a ring. Metastases adjacent to meninges and located subependymally are revealed
Fig. 13.30a–c Multiple primary lymphoma of the brain with a large
tumour node in the right parietotemporal region adjacent to the lateral ventricle triangle. Т2-weighted imaging (a): tumour stroma is revealed clearly on the background of vasogenic oedema with mildly
hyperintense signal relatively to the white matter with necrotic detritus in the central part. Т1-weighted imaging without (b) and with (c) CE show multiple foci of contrast medium accumulation of different size
Demyelinating Diseases of the Central Nervous System
Fig. 13.31a–d MS plaques in the spinal cord. MRI of cervical and
thoracic spine: sagittal Т2-weighted imaging (a) and Т1-weighted imaging (b). Axial (c) Т2-weighted imaging (slice via a plaque), involve-
1057
ment of the dorsolateral white matter of the spinal cord rightwards (arrow). Sagittal (d) Т2-weighted imaging encompassing spine. MS plaques on the lower thoracic level (arrow)
Fig. 13.32a,b Acute focus of demyelination in the cervical spinal cord in a patient with MS. Т2-weighted imaging (a) and Т1-weighted imaging with CE (b). Diffuse enhancement is seen in the focus of demyelination, the area of oedema is not enhanced having hyperintense signal on Т2-weighted imaging and hypointense on Т1-weighted imaging rostrally and caudally to the enhanced area
1058
Chapter 13 Fig. 13.33a,b Multiple confluent MS plaques and spinal cord atrophy in the secondary progressive MS. Т2-weighted imaging of cervical and superior thoracic spine (a), inferior thoracic and lumbar (b) spine in sagittal projection (arrows point to MS plaques)
FLAIR is also not so sensitive in the identification of spinal MS lesions, especially in the chronic stage. That is because chronic spinal MS plaques acquire such values of relaxation times that are compatible with those of spinal parenchyma and so they loose their contours in the spinal cord depth. Number of spinal MS lesions, especially in secondary progressive MS, increases in time. They become confluent and appear not only in the cervical but also in thoracic and lumbar regions. Neurodegenerative changes develop in parallel to demyelinating lesions as well as spinal cord atrophy (Fig. 13.33). We suggest the following protocol for MRI of the spinal cord in MS: Т2- and PD weighted imaging (spin echo)
Sagittal projection and axial projection at the level of lesions found in the sagittal one
Т1-weighted imaging
Sagittal projection
FLAIR Images
Sagittal projection, if T2 changes are unclear
Differential diagnosis of spinal MS lesions should be performed between intramedullary tumours, ischaemic spinal stroke, lymphoma, HIV myelopathy, syphilis, funicular myelosis and leukodystrophies, posttraumatic and radiation, and myelopathy. MS diagnosis is always difficult in spinal solitary lesions and absence of typical MS plaques in the brain. Enlargement of the spinal cord with cystic component is more typical for intramedullary tumours. Diffuse involvement of the whole length of the spinal cord is typical for funicular myelosis (in which lateral and posterior columns are usually affected), for HIV-myelopathy, and leukodystrophies. In leukodystrophies and funicular myelosis, CE is absent.
13.2.2 Atypical MS Types Less typical types of MS differ from classic MS in clinical signs, course, histopathological features, and neuroimaging findings.
13.2.2.1 Acute Malignant MS (Marburg Type) This disease was described for the first time by Austrian neurologist O. Marburg in 1902. This type is rarely seen; usually young adults are affected. Fever often precedes the disease, its course is fulminant and causes death within several months. Pathological findings are widespread myelin destruction, axonal loss, and oedema. MRI reveals multiple demyelinating lesions of various size (including large) with intermingling areas of perifocal vasogenic oedema (Fig. 13.34). Ring- and semi-ring CE is typical. DWI especially done in a follow-up manner reveals rapid development of demyelinating lesions with necrosis in the centre. MRS reveals nonspecific features of destruction of cellular membranes—high Lip–Lac complex, high Cho peak, with subsequent decrease of NAA (Niebler et al. 1992). This form should be differentiated from tumour-like MS (which is distinguished according to pure neuroimaging findings: large demyelinating lesions more than 3 cm in size) and from acute disseminated encephalomyelitis. For tumour-like MS, which clinically corresponds to Charcot type, classic course with relapses and remissions is typical; rapid progression as well as severe patient’s general condition is not typical. On MRI in tumour-like MS as in Marburg type large demyelinating lesions may be found and presence of “old” chronic plaques is typical; however, many of them may not show CE. Differential diagnosis of Marburg type with ADEM may be made only by following-up the patients. Successful treatment of Marburg
Demyelinating Diseases of the Central Nervous System
1059
Fig. 13.34a–c Malignant Marburg variant of MS. A series of axial FLAIR images (a–c). Large confluent supratentorial foci of demyelination along with lesions in brainstem and cerebellum are observed
1060
type is possible if treatment is started timely and high doses of immunosuppressants and steroids are administered.
13.2.2.2 Devic’s Opticomyelitis French physician E. Devic described this disease for the first time in 1890. It is an acute demyelinating syndrome affecting optic nerves and the spinal cord, which predominate in the clinical picture, and almost occur simultaneously. The signs often do not appear isolated but are the parts of a generalised disorder. Approximately 50% of patients die within the first several months. Such clinical picture is seen in several other disorders; however, the term is used only for cases of sporadic opticomyelitis. Relation of Devic’s syndrome to MS is debatable. On MRI demyelinating lesions, are found and encountered in optic nerves and spinal cord. The brain remains intact (Sadiq and 1995). Sometimes there are no changes on MRI.
13.2.2.3 Schilder’s Disease (Periaxial Diffuse Cerebral Sclerosis) This is a white matter disorder of unknown aetiology described by American neurologist and psychiatrist P. Schilder in 1912. This disorder later was classified as one of the atypical MS types and is characterised by widespread confluent and asymmetrical demyelinating lesions in both hemispheres, brainstem, and cerebellum. A large area of demyelination in parieto-occipital region expanding into splenium of corpus callosum is revealed with CE on margins. The disorder was described only in children. Clinical signs are seizures, pyramidal symptoms, ataxia, and psychiatric signs. The disease progresses within a year or two; however, demyelinating process may be fulminant and lead to fatal outcome. In the late stages, Wallerian degeneration and formation of cysts are seen
Chapter 13
in survivors. It is still debatable as to which disorder was described by Schilder. At present, most scientists believe, and we support this idea, that Schilder’s disease is an asymmetrical variant of X-linked adrenoleukodystrophy. Others think that in his article Schilder described an atypical type of MS. In several modern neurological guidelines, Schilder’s leukoencephalitis retains its nosological distinction within the group of demyelinating infectious allergic encephalitis. We observed two cases in our practice in which clinical and neuroimaging findings corresponded to those described by Schilder. In both cases, demyelinating process was confirmed by stereotactic biopsy. Interestingly that in one case, a large venous angioma was revealed inside the large demyelinating lesion (Fig. 13.35).
13.2.2.4 Balò’s Concentric Sclerosis This was for the first time was described in 1928 by Hungarian pathologist J. Balò. It is an extremely rare demyelinating disorder in which several large demyelinating lesions alternate with normally myelinated areas; MR picture resembles annual rings in tree trunks (Kim et al. 1997). Myelinated areas do most probably reflect remyelination rather that intact myelin. This progressive disorder often affects young people and is frequent in Japan and in the Philippines. Balò concentric sclerosis has a typical pathological and MR picture. Clinically, the disorder does not differ from classic MS; however, marked neurological deficit in one of descending or ascending pathways with minimal signs of dissemination in space is seen in Balò’s sclerosis (Chen et al. 1996). Therefore, it is not typical for this condition to find many demyelinating lesions in different functional systems. Taking into account a modern concept of multifactorial MS aetiology, it is possible that atypical forms of MS that have different neuroimaging picture are caused by genetic pecu-
Demyelinating Diseases of the Central Nervous System
9 Fig. 13.35a–f Schilder periaxial sclerosis. Large area of demyelination in the left parieto-occipital region with involvement of splenium of corpus callosum and with peripheral CE. Demyelination expands into the right parietal region. Series Т2-weighted imaging
1061
(a,b), Т1-weighted imaging with CE (c,d), DWI (e). Venous angioma in the centre of primary demyelination area (f) on CT angiogram (arrow) is clearly seen
1062
liarities, which influence on myelin structure and course of autoimmune process in the CNS.
13.2.3 Inflammatory Pseudotumour Demyelination Demyelinating disorders sometimes may be represented with solitary focal or not well-defined diffuse areas in the brain, which clinically and radiologically may imitate intracerebral tumours or atypical strokes. Several authors distinguish these disorders out of the primary demyelinating disorders and received a name of inflammatory pseudotumour demyelination (IPD), or inflammatory myeloclastic diffuse sclerosis, which is pathological slang rather than a term of nosology. It is a rare form of demyelinating disorders included in the group of primary demyelinating disorders, as neuroimaging reveals a solitary large demyelinating lesion in contrast to multifocal CNS involvement in ADEM (Dagher and Smirniotopoulus 1996; Kornienko et al. 2003). Histological study of autopsy or biopsy material in IPD reveals only signs of acute demyelinating process without glial or reparative transformation or remyelination, which is typical for MS. J. Kepes (1993) analysed 130 patients with IPD in a follow-up manner. No additional changes were present in most patients except for a solitary, large demyelinating lesion in the brain or in the spinal cord for the entire study period. After steroid treatment, complete recovery was seen, with formation of the CSF-filled cavity and gliosis at the site of lesion. However, in the subsequent years each 10th patient of this group was shown to develop additional changes in brain parenchyma, typical for multifocal involvement seen in MS. Several authors (Тоtolyan et al. 2002b) believe that it is more correct to distinguish “acute inflammatory demyelination syndrome”, to which onset of MS, ADEM, and IPD should be related. Inflammatory IPD is revealed in all age groups (8–77 years). Over a half of cases develop in the third to the fifth decade of life. Clinical symptoms resembles that of postvaccinal/ postinfectious encephalitides with acute onset and prominent improvement after steroids. In addition, the disorders differ from the Marburg MS variant in its clinical signs and imaging findings as well as of Schilder’s disease. Subacute onset with general cerebral, often-mild meningeal signs and focal neurological deficit with clear correlation with anatomic location of lesion is typical. As IPD has atypical clinical presentation, diagnosis is frequently made only on autopsy. Stereotactic biopsy may be performed to ascertain diagnosis, as these lesions resemble glial tumours on neuroimaging. Biopsy shows histology typical for acute demyelinating process. Demyelination and relative preservation of axons is mandatory to make a diagnosis of a demyelinating disorder. Focal lymphocytic infiltration is usually found as well as macrophages. The ratio between lymphocytes and macrophages varies and depends on time of biopsy. Focal demyelination with relative preservation of axons, reactive astrocytosis, and “torn” axons are seen. However, even histological diagnosis may be difficult due to resemblance to histological picture of a
Chapter 13
malignant glial tumour with necrotic decay in the centre and acute demyelination (without reparation and gliosis). Histological study cannot also differentiate IPD from postvaccinal/ postinfectious encephalitis if a pathogen was not inoculated from the biopsy (Poser et al. 1992). Neuroimaging findings include a solitary large (several centimetres) lesion or hardly demarcated hypodense area on CT. MRI reveals this area as hyperintense on T2-weighted imaging and hypointense on T1-weighted imaging (Fig. 13.36). Marked perifocal oedema may be seen with mass effect on adjacent structures. The area usually is located in the white matter of cerebral hemispheres or sometimes in cerebellar hemispheres (Falini et al. 2001). Grey matter remains intact. In contrast to classic MS, there is no involvement of the periventricular white matter, optic nerves, and brainstem. In IPD, heterogeneous accumulation of contrast agent is seen after CE mainly on the periphery of lesions (ring- or semi-ring or semi-rim type CE). Similar semi-ring type of CE may be seen in malignant gliomas, often in glioblastoma, and in brain abscess. However, semi-ring type of CE is considered typical for demyelinating process, due to presence of intact (nonenhancing) and altered (enhancing) regions of BBB. The central part of a demyelinating lesion is usually not enhanced, as it is area of total alteration of brain tissue. DWI studies demonstrated that DWI picture depends on time of the study and the stage of IPD, which may play an important differential sign between IPD and a tumour (Kornienko et al. 2002). DWI and MRI with CE, as well as MR angiography allow differentiating most cases of IPD from ischaemic stroke. In our studies in 1999–2003, we analysed seven cases of IPD confirmed by complex follow-up neuroimaging and stereotactic biopsy with immunohistochemistry. Patients were admitted to the Burdenko Institute of Neurosurgery with diagnoses of intracranial tumour or ischaemic stroke. In six cases, a solitary demyelinating lesion was revealed (3–7 сm in diameter), with typical density changes on CT and intensity changes on MRI, typical semi-ring CE surrounded by perifocal oedema, and with mass effect on adjacent brain structures. Only supratentorial lesions were seen in the white matter of the frontal, temporal, and parietal lobes, with deep and subcortical white matter involvement. Four large lesions were revealed in one patient in the frontal and temporal regions of cerebral hemispheres. In all cases partial recovery and improvement of demyelinating lesions was seen after steroids. In one case after complete recovery of one large lesion with residual glial scar developed, a new large demyelinating lesion developed 2 years later in the opposite hemisphere, which also recovered after steroid therapy. Having no laboratory tests confirming IPD, positive effect of steroids and unfeasibility of surgical treatment, the task of primary neuroimaging of this demyelinating disorder is a very important problem, the salvation of which would avoid mistakes in treatment. Of course, the question of nosological distinction of IPD remains unresolved and requires further research. Possibly, this disorder will also occur to be an atypical MS variant.
Demyelinating Diseases of the Central Nervous System
1063
Fig. 13.36a–f Pseudotumour inflammatory demyelination. Т2weighted imaging (a) and Т1-weighted imaging (b) show a large solitary focus of demyelination with perifocal oedema and moderate mass effect into the left lateral ventricle of the left posterior frontoparietal-occipital region. Т1-weighted imaging with CE (c) reveals
heterogeneous enhancement on the periphery of the affected area in a shape of crown-effect. The hypointense zone in the central part does not enhance. DWI, b = 500 (d) and b = 1000 (e). МRS (f) of the affected area: decrease of NAA and Cr, elevation of Cho, and appearance of high, two-humped Lip–Lac complex peaks are seen
13.3 Disorders with Secondary Demyelination and/or Destruction of White Matter
cal findings. Demyelination in viral infections may be caused by several mechanisms: (1) direct oligodendroglial infection (JC papavovirus), (2) autoimmune destruction of oligodendrocytes and myelin via cross-autoimmune reactions into viral particles, (3) secondary damage by immune complexes, and (4) autoimmune reaction on myelin (Gusev et al. 2004). Neurons and glia may be infected as it occurs in encephalitis and encephalomyelitis. Autoimmune demyelination may concurrently occur as in acute disseminated encephalomyelitis in which virus has not been inoculated from the brain tissue. In the so-called slowly progressing encephalitis (for instance, subacute sclerotising panencephalitis) and in progressive multifocal leukoencephalopathy, direct infection of the brain occurs which proceeds for several months or years and then clinically manifests after primary contamination.
In many white matter disorders, secondary demyelination or myelin destruction occur due to known causes. Pathological findings vary from “pure” demyelination (as in central pontine myelinolysis), up to necrosis withy demyelination (as in PML). Secondary demyelinating disorders due to toxic and metabolic defects are discussed in the appropriate chapters. Here we discuss on secondary demyelination of viral and postvaccinal aetiology. One classification of viral infections is based on an anatomic principle, i.e. on location of structures that are affected—meninges, the peripheral nervous system, and the CNS. These factors stipulate clinical manifestations and pathologi-
1064
13.3.1 Acute Disseminated Encephalomyelitis ADEM (perivenous encephalomyelitis, postinfectious encephalomyelitis, acuteperivascular myelinoclastia) is an inflammatory demyelinating disorder that is often seen in children, but may occur in all age groups. It clinically manifests as a monophasic process, limited by CNS boundaries and developing several weeks after recovery from a nonspecific infection (measles, rubella, mumps, varicella, mononucleosis, Epstein-Barr infection, pertussis, Mycoplasma or Cocksakie B infection) or after vaccination (of rabies, diphtheria, smallpox, tetanus, or typhus). It may occur spontaneously in complete health. Clinical symptoms develop within several days after primary infection and include fever, headache, and meningeal signs, which may be complicated by seizures and focal neurological signs such as ataxia, cranial neuropathies, choreatetosis, sopor, and coma. Beneficial effect of steroids is usually seen; however, in the most severe cases, even a combination of steroids and plasma exchange with intravenous λ-immunoglobulins are ineffective. Neurological deficit usually improves spontaneously within a month. Residual neurological deficit remains in 10–20% of patients, and the most frequent complication is epileptic seizures. Sometimes progression of neurological deficit occurs with severe quadriparesis, other neurological signs, and even fatal outcome. A CSF test may reveal no pathology or neutrophilic pleocytosis may occur up to 1,000 cells/mm3, mild protein elevation, and rarely, elevation of oligoclonal immunoglobuli -G (IgG) bands titre. Histology of ADEM is identical to that of experimental allergic encephalomyelitis (especially its chronic form), which confirms the autoimmune origin of ADEM after viral infection of the CNS. The most vivid pathological findings are lymphocytic infiltration of meninges and perivascular spaces of the brain; perivascular infiltrates consist of microglia and “foamy” macrophages, multiple demyelinating lesions, vasculitis, and perivascular necrosis are identified in the brain and the spinal cord. Demyelination is demarcated by areas of lymphocytic infiltration. Largely, brain oedema is seen and initial signs of cerebral herniation. In contrast to MS, macroscopic examination reveals several typical lesions or fails to reveal them at all. Virus has not been inoculated from autopsy material. MRI features of ADEM are identical to that of initial MS stages. In some patients with ADEM, further exacerbations occur, and the diagnosis changes to MS. On T2-weighted imaging multiple hyperintense homogenous (due to simultaneous occurrence) lesions in the supratentorial white matter, brainstem, and cerebellum with frequent involvement of deep grey matter (Fig. 13.37). Lesions may be large, but mass effect is usually minimal. A follow-up MRI usually identifies marked reduction of lesions in size (Fig. 13.38), and in some cases, complete recovery after steroids. In ADEM (as in MS) ring-shaped CE is seen in most cases, semi-ring type of CE is less typical, as the process of demyelination is monophasic and acute; however, absence of CE does not rule out the diagnosis. Optic neuritis often occurs as well as the spinal cord involvement (Sing et al. 1999; Khong et. al. 2002). ADEM with monofocal lesions sometimes cannot be distinguished from
Chapter 13
inflammatory demyelinating pseudotumour, especially in cases when lesion is large. All monofocal demyelinating disorders, such as MS, ADEM, and IPD require differential diagnosis with gliomas and metastases, and patients with such disorders often require Stereotactic biopsy. Based on our own experience, we think that in cases with suspicions on ADEM and IPD, it is feasible to reject urgent STB or open biopsy due to invasiveness of the procedure, and to make a diagnosis it is better to perform a follow-up MRI, after steroids administered ex juvantibus. In many cases “a tumour” rapidly reduces after steroids (”improvement” of a demyelinating lesion), in other cases when the effects of steroids is absent a follow-up MRI may reveal additional demyelinating lesions (Figs. 13.39, 13.40).
13.3.2 Acute Haemorrhagic Encephalitis Acute haemorrhagic encephalitis (AHE, Hurst’s disease) is a fulminant form of ADEM (described by В. Hurst in 1947). This disorder is more frequently seen in young patients and starts with abrupt fever, occipital muscles rigidity, and progressive neurological deficit, which leads to a fatal outcome 1–5 days later. AHE develops after viral infections, sepsis, as a complication of allergic disorders (including ulceration colitis and bronchial asthma), as well as after several medications intake. Elevation of IgG titre and presence of basic myelin protein are found in the CSF. Occasional cases of recovery were described in literature after aggressive steroid therapy, and in one case, the course was slow—up to 1.5 months (Scott et al. 2002). Brain autopsy reveals multiple lesions of acute perivascular demyelination and multiple haemorrhages into the white matter (especially frequent in centrum semiovale, internal capsule and the cingulated gyrus white matter). U-shaped subcortical fibres are spared. On microscopy, necrotising angiitis with perivascular ring-shaped and round haemorrhages is found. Confluent haemorrhages can be seen. Chronic perivenous inflammatory infiltrates consist of macrophages with lipid inclusions and T lymphocytes with microglial and astrocytis activation. On MRI, multiple asymmetrical demyelinating lesions are found in the white matter of cerebral hemispheres and cerebellum with small haemorrhages. Differential diagnosis should be made with haemorrhagic vasculitis.
13.3.3 Subacute Sclerotising Panencephalitis Subacute sclerotising panencephalitis (SSPE, Van Bogaert’ disease) was described in 1933 by. J.R. Dawson, in 1939 by Pette and Derrin, and in 1945 by Belgian neurologist L. van Bogaert. The disease develops due a latent infection reactivated after an acute episode of measles and has slow course. Owing to national programmes of vaccination, SSPE became rare. For unknown reasons in SSPE patients, the measles virus acquires a mutation in its genome, which gives it a property to persist for a long time in neurons and oligodendrocytes of the brain. The immune reaction to the virus remains incomplete, and
Demyelinating Diseases of the Central Nervous System
1065 Fig. 13.37a–f Acute disseminated encephalomyelitis. Multiple large demyelinating lesions in the white matter of cerebral hemispheres bilaterally, hyperintense on Т2-weighted imaging (a) and hypointense on Т1-weighted imaging (b) are observed. CE is seen in a shape of ring and semi-ring on the periphery of lesions (c). DWI, b = 500 (d) and b = 1000 (e) reveal decreased signal in the central parts of demyelinating lesions (areas of myelin destruction) and high signal on the periphery of lesions (oedema). МRS (f) of the demyelinating lesion: decrease of NAA, elevation of Cho, and appearance of high, two-humped Lip–Lac complex peaks
1066
Chapter 13 Fig. 13.38a–f Acute disseminated encephalomyelitis. Axial Т2-weighted imaging (a), sagittal FLAIR image (b), and Т1-weighted imaging with CE (c,d). There are multiple supra tentorial demyelinating lesions of different size including large ones, which enhance and surround by perifocal oedema, in the white matter of cerebral hemispheres and corpus callosum. Axial Т2-weighted (e) and Т1-weighted imaging (f) performed, respectively, 1 month after the first study. Reduction of number and size of demyelinating lesions is seen; reduction of perifocal oedema with compensatory dilatation of the lateral ventricles were found
Demyelinating Diseases of the Central Nervous System
1067 Fig. 13.39a–f Stereotactic biopsy in a patient with ADEM. Pathological focal process in the deep and subcortical white matter of the right frontal lobe (a–c). Follow-up MRI 2 weeks later: new demyelinating lesions appeared (d–f), including medulla oblongata (arrow)
1068
Fig. 13.40a–i Open biopsy of a focus of ADEM in a suggested diagnosis of a tumour. MRI (a–f) 1 month after surgery reveals postsurgical changes in the right posterior temporo-occipital region and multiple demyelinating lesions of other locations, including
Chapter 13
brainstem and corpus callosum with CE (arrows). Follow-up MRI 2 months after treatment with steroids (g–i): marked reduction of demyelinating lesions and absence of contrast medium accumulation are observed
Demyelinating Diseases of the Central Nervous System
1069
the constant presence of the virus may lead to conformational changes, which may induce inflammatory myelin destruction also. This is confirmed by higher proinflammatory cytokines levels in the brain. There may be a secondary demyelination due to neuronal loss. The disease begins between the ages of 3–20 years and has a several-years-long latent period. Mental retardation, progressive myoclonus, epilepsy, and ataxia are the clinical signs. Progressive cerebral involvement leads to immobilisation, brainstem syndrome, and coma. Fatal outcome occurs within 6 months to 6 years. Many theories have been proposed to explain long latent period and slow course of the disease, but none of them was fully adopted. Grey and white matter involvement is seen on pathology. Neuronal loss, eosinophilic intranuclear and intracytoplasmic inclusions of viral particles with remnants of cytoskeleton (Alzheimer-like tangles) in neurons and oligodendroglia, parenchymal lymphocytic infiltration, demyelination, and gliosis are the pathological findings.
MRI and CT reveal diffuse changes in density and signal in the periventricular white matter with grey matter involvement in basal ganglia and cortex with marked oedema and mass effect, compression of ventricles, and cerebral atrophy with neuroimaging picture of that of a shrunken walnut in the terminal stage (Fig. 13.41). In the late stages, SSPE is not distinguishable according to neuroimaging features from the consequences of acute panencephalitis with predominant white matter involvement (Senol et al. 2000).
Fig. 13.41a–f Subacute sclerotising panencephalitis, late stage. A
subcortical white matter, cerebral atrophy with dilatation of external subarachnoid spaces and the ventricular system, a neuroimaging picture similar to that of a shrunken walnut
series of axial MR images: Т2-weighted imaging (a,b), Т1-weighted imaging (c,d), and FLAIR (e,f). Total involvement of the deep and
13.3.4 Progressive Rubella Panencephalitis Progressive rubella panencephalitis (PRPE) is an extremely rare disease described for the first time in the 1970s. It develops as a complication of intranatal rubella. Pathogenesis in unclear, and disease may start 8–19 years after the primary infection. Clinical picture resembles that on Van Bogaert’s en-
1070
cephalitis; however, myoclonus is less evident, and cerebellar ataxia is more severe. Fatal outcome occurs 2–3 years after onset. Widespread demyelination of the white matter of cerebral hemispheres, and involvement of basal ganglia and brainstem are the pathological findings. Vasculitis, perivascular lymphocytic infiltration, and neuronal loss are seen. In contrast to SSPE, no intranuclear and intracytoplasmic inclusions are found in PRPE (Yakhno and Shtulman 2001). Neuroimaging findings are nonspecific and resemble that of SSPE. Differential diagnosis should be made with SSPE and other viral panencephalitis (Scott et al. 2002). There is no effective treatment on SSPE and PRPE.
13.3.5 Progressive Multifocal Leukoencephalopathy PML is caused by reactivation of the latent JC papavovirus (named after initials of the patient of whom it was inoculated). Before the AIDS epidemics, PML was rarely diagnosed and occurred mainly in patients with leukaemia or lymphoma, or developed after organ transplantation with subsequent immunosuppressive therapy. Most cases of PML present are AIDS complication. PML develops in 5% of AIDS patients. In patients who do not have AIDS, other disorders may lead to PML such as those affecting immunocompetent cells (leukaemia or lymphoma, sarcoidosis, tuberculosis, malignancies) and immunosuppressive therapy (Lee et al. 2001). Rarely are no systemic disorder or acquired immunodeficiency are found in PML patients. PML starts with dementia and various other neurological signs such as visual loss, palsies, ataxia, and aphasia. Palsies are most prominent. Seizures also occur as a sign of cortical involvement. Diagnosis is made according to combination of MRI data and PCR in the CSF on JC papavovirus DNA. Biopsy is performed in those cases when MRI and clinical findings support PML, but repeated PCR of the CSF done with interval not less than 4 weeks, are negative. Numerous PCR sensitivities are 99%, and a single PCR sensitivity is 80%. The disease leads to severe neurological deficit; survival is 6 month in average. Longer survival correlated with higher CD4+ lymphocyte count. Recently elaborated antiviral therapy, which activates the immune system in AIDS, may also prolong life in PML. Confluent demyelinating lesions in the white matter of cerebral hemispheres or generalised demyelination are found in PML. Grey matter is also involved, but lesions are not so conspicuous in it. Multiple demyelinating lesions are found on microscopy. Necrosis is not typical. Atypical oligodendrocytes are characteristic by large swollen nuclei, and basophilic and eosinophilic inclusions. Reactive astrogliosis is also seen with large and atypical astrocytes. Chronic inflammatory cellular infiltration is noted. Demyelinating lesions resemble those in MS, but are larger and confluent, resembling ischaemic necrosis with cystic degeneration. As the virus is found in oligodendrocytes, it is believed that the cause of PML is incapacity of the affected lymphocytes to support myelin function. MRI features of PML are multifocal hyperintense lesions with unclear margins on T2-weighted imaging and in the
Chapter 13
subcortical white matter. White matter of the parietal lobes is more frequently affected; however, lesions may be situated in the frontal regions. Only seldom are lesions present at the disease onset, but with progression, they increase in number. Mild mass effect is seen near lesions, so it can be difficult to differentiate it from glioma at times. CE is absent, probably due to mild inflammation. However, in 5–15% of patients, CE on the lesion periphery is found (Scott et al. 2002). Abnormal angiography findings such as parenchymal hyperaemia and arteriovenous shunting, which have been encountered in several PML patients, may reflect proliferation of small vessels and perivascular inflammatory changes due to JC papavovirus persistence in the oligodendrocytes. Despite the fact that the majority of lesions are situated in the white matter, approximately in 50% of patients grey matter involvement is seen too. A few authors described haemorrhages; others consider them a feature atypical for PML. MRI reveals posterior fossa structures involvement in 48% of cases (Falini et al. 2001). Other disorders affecting the white matter and mimicking PML may be present in AIDS patients. They are such disorders with multifocal white matter involvement as cytomegaloviral encephalitis, Toxoplasma encephalitis, and HIV-1-associated encephalopathy. Mass effect is more typical for lymphoma and toxoplasmosis, but may be seen in PML also. Optic neuritis does not occur in PML, and spinal cord is involved in rare occasions.
13.3.6 HIV-Associated Disorders of the CNS (AIDS-Dementia Complex and Vacuolar HIV-Myelopathy) Recent literature reports that the AIDS virus (HIV-1 and HIV-2) was transmitted from monkeys contaminated with zoonoses immunodeficiency virus to humans. Fifty million HIV-infected patients exist worldwide. Recently it has been shown that combined antiretroviral therapy may prolong life of HIV-infected individuals. In 7–20% of patients, neurological deficits are the first clinical signs. They may be caused by an HIV virus itself or by other infections. Frequently opportunistic infections occur, such as the JC papavovirus that causes PML, cytomegalovirus, toxoplasmosis, fungal infection etc. HIV-associated neurological complications are aseptic meningitis, HIV encephalopathy, vacuolar myelopathy, peripheral neuropathy, and myopathy. Cerebral involvement in HIV is also known as the AIDS–dementia complex. The virus affects the CNS in the early stage and enters the CSF. With disease progression, the viral content increases in the CSF. The higher it is, the higher the risk of dementia. Usually, HIV encephalopathy develops in patients with marked immunosuppression and concomitant systemic disorders. In some cases, it may be the first sign of the disease. Radiologist should differentiate HIV encephalopathy from dementia of another origin. In most patients cognitive decline, slowing of mental processes and memory loss occurs. In rare cases AIDS-dementia complex progresses rapidly (Yakhno and Shtulman 2001). In most cases of HIV encephalopathy not complicated with toxoplasmosis or lymphoma, mild atrophy is seen. Microscopic changes are variable and widespread. Deep grey mat-
Demyelinating Diseases of the Central Nervous System
1071
ter and the white matter of cerebral hemispheres are mainly affected, whereas cortex is well preserved. On histology, myelin is diffusely pallid in both hemispheres and cerebellum. Vacuolation, myelin, and axonal loss with signs of necrosis are the pathological findings in the white matter. Mild chronic inflammation may be present. Macrophagal infiltration and increased number of microglial cells and reactive astrocytes are seen. Microglial infiltrates are nodular in shape. Giant polynuclear cells are the most conspicuous feature of HIV encephalopathy. They are found in brain parenchyma and in perivascular spaces. More frequently, they are found in white matter of cerebral hemispheres, basal ganglia, and thalamus. MRI usually reveals brain atrophy. In the early stages, Т2weighted imaging shows hyperintense signal in the periventricular white matter of the brain without oedema and mass effect. Many lesions of cortical and subcortical location are identified on FLAIR images (Scott et al. 2002). With the progression of the disease, confluent hyperintense areas appear in the deep white matter (Fig. 13.42). Bilaterally symmetri-
cal hyperintense signal on prolonged TR images are seen in basal ganglia (caudate nucleus and putamen) and thalamus; hyperintense signal may be seen in brainstem also. Followup MRI after antiviral therapy in AIDS-dementia reveals improvement and stabilisation of MR signal changes. Proton MRS reveals decrease of NAA–Cr ratio, increased Cho peak in NAWM, and presence of Lac in the white matter with abnormal MR signal. Several authors reported decreased level of lactate in HIV encephalopathy patients on the follow-up MRS after antiviral treatment. In addition, myelopathy may develop in HIV-infected individuals. It is characterised by a diffuse white matter involvement in the spinal cord frequently throughout its length. It appears as hyperintense signal on T2-weighted imaging, not visualising or mildly hypointense on T1-weighted imaging. CE is frequently absent. It should be remembered that the abovementioned CNS in HIV-infected individuals may be caused not by HIV infection itself, but also be other opportunistic infection such as cytomegalovirus, toxoplasmosis, etc.
Fig. 13.42a–f HIV encephalopathy and myelopathy. CT (a), MRI: Т2-weighted imaging (b), and Т1-weighted imaging without (c) and with (d) CE. Leukoencephalopathy with involvement of temporooccipital regions and splenium of corpus callosum. There is no CE.
e,f HIV myelopathy: sagittal Т2-weighted imaging. Diffuse thickening of the spinal cord is seen, increased signal on T2-weighted imaging (oedema, demyelination)
1072
Chapter 13
Refere n c e s Adams R, Victor M (1993) Multiple sclerosis and allied demyelinative diseases. In: Adams RD, Victor M (eds) Principles of neurology, 5th edn. McGraw-Hill, New York, pp 776–798
Khong P, Ho H, Cheng P et al (2002) Childhood acute disseminated encephalomyelitis: the role of brain and spinal cord MRI. Pediatr Radiol 32:59–66
Aviv R, Benseler S, Silverman E et al (2006) MR imaging and angiography of primary CNS vasculitis of childhood. AJNR Am J Neuroradiol 27:192–199
Kim M, Lee S, Choi C et al (1997) Balò’s concentric sclerosis: a clinical case study of brain MRI, biopsy, and proton magnetic resonance spectroscopic findings. J Neurol Neurosurg Psych 62:655–658
Balò J (1928) Encephalitis periaxialis concentrica. Arch Neurol Psychiatr 19:242–264
Kornienko V, Pronin I, Serkov S et al (2003) The case of acute inflammatory demyelinative process with a pseudotumourous course. J Med Visualis 1:6–12 (in Russian)
Barkhof F (1997) The role of magnetic resonance imaging in diagnosis of multiple sclerosis. In: Thompson A, Polman C, Hohlfeld R, Dunitz M (eds) Multiple sclerosis: clinical challenges and controversies. Martin-Dunitz, London, pp 43–64 Barkhof F, Filippi M, Miller D et al (1997) Comparison of MRI criteria at first presentation to predict conversion to clinically definite multiple sclerosis. J Brain 120:2059–2069 Bartitynski W, Boardman J, Zeigler Z et al. Posterior reversible encephalopathy syndrome in infection, sepsis and shock. AJNR Am J Neuroradiol 27:2179–2190 Chen C, Ro L, Chang C et al (1996) Serial MRI studies in pathologically verified Balò’s concentric sclerosis. J Comput Assist Tomogr 20:732–735 Cho S, Lee D, Hong S, Oh W (2007) Intracranial aspergillosis involving the internal auditory canal and inner ear in an immunocompetent patient. AJNR Am J Neuroradiol 28:138–140 Ciccarelli O, Werring D, Wheeler-Kingshott C et al (2001) Investigation of MS normal-appearing brain using diffusion tensor MRI with clinical correlations. J Neurology 56:926–933
Lee S, Yoon P, Park S et al (2001) MRI findings in neuro-Behçet disease. J Clin Radiol 56:485– 494 Leng Tan I, van Schijndel R, Pouwels P et al (2000) MR venography of multiple sclerosis. AJNR Am J Neuroradiol 21:1039–1042 Lin F, Yu C, Jiang T et al (2007) Diffusion tensor tractography-based group mapping of the pyramidal tract in relapsing–remitting multiple sclerosis patients. AJNR Am J Neuroradiol 28:278–284 Lobzin IU, Uskov A, Kozlov S (2000) Lyme disease (Ixodes scapularis). Foliant, St. Petersburg, p 174 (in Russian) Loevner L, Grossman R, Cohen J et al (1995) Microscopic disease in normal-appearing white matter on conventional MR images in patients with multiple sclerosis: assessment with magnetizationtransfer measurements. J. Radiology 196:511–515 McDonald W, Compston A, Edan G et al (2001) Recommended diagnostic criteria for multiple sclerosis: guidelines from the international panel on the diagnosis of multiple sclerosis. J Ann Neurol 50:121–127
Dagher A, Smirniotopoulos J (1996) Tumefactive demyelinating lesions. J Neuroradiology 38:560–565
Miller D, Grossman R, Rheingold S et al (1998) The role of magnetic resonance techniques in understanding and managing multiple sclerosis. J Brain 121:3–24
Evangelou N, Konz D, Esiri M et al (2000) Regional axonal loss in the corpus callosum correlates with cerebral white matter lesion volume and distribution in multiple sclerosis. J Brain 123:1845–1849
Newcombe J, Hawkins C, Henderson C et al (1991) Histopathology of multiple sclerosis lesions detected by magnetic resonance imaging in unfixed postmortem central nervous system tissue. J Brain 114:1013–1023
Falini A, Kesavadas C, Pontesilli S et al (2001) Differential diagnosis of posterior fossa multiple sclerosis lesions: neuroradiological aspects. J Neurol Sci 22:S79–S83
Niebler G, Harris T, Davis T et al (1992) Fulminant multiple sclerosis. AJNR Am J Neuroradiol 13:1547–1551
Fazekas F, Offenbacher H, Fuchs S et al (1988) Criteria for an increased specificity of MRI interpretation in elderly subjects with suspected multiple sclerosis. J Neurol 38:1822–1825 Filippi M, Cercignani M, Inglese M et al (2001) Diffusion tensor magnetic resonance imaging in multiple sclerosis. Neurology 56:304–311 Filippi M, Bakshi R, Rovaris M et al (2007) MRI and multiple sclerosis: what happend in the last 10 years? J Neuroimaging 17:1–2 Ge Y (2006) Multiple sclerosis: the role of MR imaging. AJNR Am J Neuroradiol 27:1165–1176 Grossman R, McGowan J (1998) Perspectives on multiple sclerosis. [Review article.] AJNR Am J Neuroradiol 19:1251–1265 Gusev E, Zavalishin I, Boiko A (2004) Multiple sclerosis and the other demyelinative diseases. Miklosh, Moscow, p 540 (in Russian) Gusev E, Demina T, Boiko A (1997) Multiple sclerosis. Miklosh, Moscow, p 544 (in Russian) Kepes J (1993) Large focal tumour-like demyelination lesion of the brain: intermediate entity between multiple sclerosis and acute disseminated encephalomyelitis? A study of 31 patients J Ann Neurol 33:18–27
Nusbaum A, Tang C, Wei T et al (2000) Whole-brain diffusion MR histograms differ between MS subtypes. J Neurology 54:1421–1427 Poser C, Paty D, Scheinberg L et al (1983) New diagnostic criteria for multiple sclerosis: guidelines for research protocols. J Ann Neurol 13:227–231 Poser S, Lüer W, Bruhn H et al (1992) Acute demyelinating disease. Classification and non-invasive diagnosis. J Acta Neurol Scand 86:579–585 Prineals J et al (1985) The neuropathology of multiple sclerosis. In: Koetsier J (ed) Demyelinating diseases. Elsevier, Amsterdam, pp 213–257 Pronin I, Beliaeva I, Boiko A et al (2003) Diagnostic and prognostic abilities of MRI in multiple sclerosis. J Neurol Psychiatr 2:18–25 (in Russian) Rocca M, Filippi M (2007) Functional MRI in multiple sclerosis. J Neuroimaging, 17:36–41 Sadiq S, Miller J (1995) Multiple sclerosis, Devic syndrome and Balò’s disease. In: Rowland L (ed) Merrit textbook of neurology, 9th edn. Williams & Wilkins, Baltimore, pp 804–826 Scott W et al (2002) Magnetic resonance imaging of the brain and spine, 3rd ed. Lippincott Williams & Wilkins, Philadelphia, pp 1240
Demyelinating Diseases of the Central Nervous System
1073
Senol U, Haspolat S, Cevikol C et al (2000) Subacute sclerosing panencephalitis: brain stem involvement in a peculiar pattern. J Neuroradiol 42:913–916
Totolyan N, Trophimova T, Skorometz A (2002) Abilities of magnetic resonance imaging in diagnostics of multiple sclerosis. J Neurol Psychiatr 1:32–41 (in Russian)
Shalmon B, Nass D, Ram Z et al (2000) Giant lesions in multiple sclerosis a diagnostic challenge. J Harefuah 138:936–939
Totolyan N, Skorometz A, Trophimova T (2002) Multiple sclerosis with debut in childhood. J Neurol Psyhiatr 7:3–8 (in Russian)
Singh S, Alexander M, Korah I (1999) Acute disseminated encephalomyelitis: MR imaging features. AJR Am J Radiol 173:1101–1107
Zavalishin I, Golovkin V (2000) Multiple sclerosis. Selected chapters of the theory and practices. Detskaya Kniga, Moscow, p 453 (in Russian)
Singh S, Kochhar R, Vashishta R et al (2006) Amoebic meningoencephalitis: Spectrum of imaging findings. AJNR Am J Neuroradiol 27:1217–1221
Yakhno N, Shtulman D (2001) Diseases of the nervous system. Medicine, Moscow, p 480 (in Russian)
Chapter 14
Neurodegenerative Disorders of the Central Nervous System
14
in collaboration with S. Serkov
14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8
Introduction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synucleinopathies .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Taupathies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cerebral Amyloidoses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spinocerebellar Degenerations .. . . . . . . . . . . . . . . . . . . . . . . . . . Huntington’s Disease .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hereditary Spastic Paraplegias . . . . . . . . . . . . . . . . . . . . . . . . . . . Amyotrophic Lateral Sclerosis . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1075 1076 1078 1080 1084 1084 1085 1086
14.1 Introduction Neurodegenerative disorders of the CNS is a conditionally distinguished heterogeneous group of relatively slowly progressing disorders with predominant grey matter involvement and in most cases, with formation of abnormal intracellular deposits with the following apoptotic death of neurons. At present, the term conformation diseases is used to determine this group of disorders in literature, as much evidence has been accumulated about the primary role of protein conformation (folding) changes in the majority of neurodegenerative disorders of the CNS. Several disorders earlier related to neurodegenerative are now related to primary metabolic encephalopathies (such as Wilson disease, Hallervorden-Spatz disease, etc.), as their pathogenesis was ascertained and considered to be unrelated to conformation diseases pathogenesis; specific inclusions are also absent in these disorders. There exists a hypothesis that true neurodegenerations reflect (or serve a model) an accelerated physiological aging triggered by some endogenous or exogenous factor. Endogenous factors are often products of mutated genes that are abnormal neuronal proteins that play important role in the maintaining the cellular metabolism and cytoskeleton function. The majority of endogenous factors that are triggers of neurodegeneration (ND) remain unexplored. The role of electromagnetic exposure, impairment of ecology, chronic stress,
etc. is discussed. Transmissive spongiform encephalopathies are the specific class of ND. There are prion disorders in which a molecule of exogenous abnormal prion protein plays a crucial etiological role. It is noteworthy that there is no neuroimaging classification of ND of the CNS, as this group encompasses the smallest quantity of nosologies characterised by specific imaging features. Many disorders of that group cannot be diagnosed by imaging at all, especially in the early stages (Hauser and Olanow 1994; Valk et al. 2003). We suggest modern classification of ND of the CNS based on molecular, biological, and pathological findings, and, when possible, clinical signs. Classification of Neurodegenerative Disorders of the CNS (Illarioshkin 2003, with additions): 1. Synucleinopathies a. Lewy body diseases (Parkinson disease and Lewy bodies disease) b. Multiple systemic atrophy 2. Taupathies a. Progressive supranuclear palsy (Steel-RichardsonOlszewski syndrome) b. Frontotemporal dementia c. Corticobasal degeneration 3. Cerebral amyloidoses a. Alzheimer’s disease b. Cerebral amyloid angiopathy c. Transthyretine-associated cerebral amyloidoses d. Human prion diseases 4. Spinocerebellar degenerations 5. Huntington’s disease 6. Hereditary spastic paraplegias 7. Amyotrophic lateral sclerosis As a whole, ND from the imaging point of view are characterised by slowly progressive atrophy of these or those nuclei and less of pathways, and by concomitant dilatation of CSF spaces, which are better seen on late stages of these disorders. Relatively mild demyelination and gliosis may be present. Prion disorders have specific neuroimaging features. On early stages of all ND imaging features are usually absent. However, the
1076
possibility to perform live neuroimaging diagnosis of conformation diseases of the CNS attracts great interest, as at present final diagnosis of the majority of these disorders may be made only on autopsy.
14.2 Synucleinopathies Synucleinopathies encompass disorders that develop due to impairment of alpha-synuclein metabolism, a neuronal protein that makes about 1% of brain weight. The normal function of the protein is yet unexplored. Research data implies its important role in memory, synaptic transport, and stability of other neuronal protein functions, in particular, in dopaminergic transmission. The common feature of this group disorders is detection on electron microscopy of strictly specific intracellular inclusions: Lewy bodies. The main components of Lewy bodies are abnormal alpha-synuclein and other proteins, fatty acids, sphingomyelin, and polysaccharides.
14.2.1 Parkinson’s Disease Parkinson’s disease (idiopathic parkinsonism) is one of the most prevalent ND of the CNS and is found in up to 80% cases of the parkinsonism syndrome. Other 20% of cases are symptomatic or are included in syndromes of other ND. The disease was first termed trembling paralysis in 1817 by the British physician James Parkinson. He described the disease in himself and five other patients, among whom there were some of his relatives. The term Parkinson’s disease was later coined by the famous French neurologist J. Charcot. The disease starts in the elderly and is encountered in 2–4% of all individuals older than 65 years according to data from the most studied populations worldwide (60–140 cases per 100,000). Positive familial history is revealed in 10–15% of patients; the majority of cases are sporadic. Four genetic loci responsible for the autosomaldominant Parkinson’s disease have been identified (PARK1on chromosome 4q21–23: the gene of alpha-synuclein itself and PARK2 on chromosome 6q25.2–27; the gene of parkin (ubiquitin ligase L3), responsible for juvenile parkinsonism; PARK3 on chromosome 2p13, (the gene and the substrate are unknown), and PARK4 on chromosome 4p14–16.3 (the gene and the substrate are unknown); and PARK5 on chromosome 4p14 the gene of ubiquitin carboxy-terminal hydrolase L1, the enzyme that participates in the ubiquitin proteasome degradation pathway of abnormal neuronal proteins). The disorder is inevitably progressive and is characterised by a classic triad of symptoms: tremor in rest, muscle rigidity, and hypokinesia (akinetic rigidity syndrome). Cognitive and emotional dysfunction, asymmetrical distribution of symptoms and positive effect of levodopa treatment are typical. Pyramidal and cerebellar signs are absent. Aetiology and pathogenesis of the disease remain unclear. Aging, genetic predisposition (see above), and exogenous factors are regarded as etiological risk factors that. One of the most important exogenous risk factors that may cause a syndrome clinically identical to Parkinson’s disease (PD) is
Chapter 14
1-methyl-4-phenyl-1,2,3,6-tetrahydropiridin, which leads via several steps of metabolism to a blockage of NADP-hydroxylase in the mitochondria of neurons in substantia nigra, with further neuronal death. Iron and aluminium also play an important role in the pathogenesis of the disease. These ions are found in large quantities in the neurons of substantia nigra in PD. These ions cause toxic effects, and mediate formation of free-oxygen species, which trigger oxidative stress that causes neuronal death. The main pathogenetic mechanism of all clinical forms of PD is a severe depletion of dopaminergic pool of neurons in substantia nigra and striatum, and hence, impairment of relations between striatum and other basal ganglia and cerebral cortex. Dopaminergic denervation leads to excessive inhibition of basal ganglia and their excessive inhibitory inputs on the motor cortex with development of akinesia. The pathogenesis of juvenile parkinsonism, a specific form of PD with onset between 20 and 40 years and PARK2 gene mutations, is different. The product of this gene, the enzyme ubiquitin ligase-L3, immediately participates in ubiquitination, of alpha-synuclein in normal individuals without PD, but in PD its function is impaired and the formation of Lewy bodies is impossible, which indicates out a protective role of these bodies in other forms of PD. Degeneration and death of pigmented (melanin containing) dopaminergic neurons of substantia nigra and locus coeruleus are revealed, gliosis of these nuclei, atrophy of the adjacent portions of the midbrain tectum, secondary degeneration of dopaminergic, and noradrenergic pathways connecting these nuclei with putamen and cerebral cortex are also seen. Iron-ion depositions in high concentrations are seen in substantia nigra. Lewy bodies are detected in the degenerating neurons, except for juvenile parkinsonism cases (Wakabayashi et al. 1993). Moderate atrophy of cerebral cortex is observed on gross examination. CT reveals no changes. Routine Т1- and Т2-weighted MRI reveal mild dilatation of the subarachnoid spaces of the cerebral hemispheres. In “pure” PD, there is no signal change in the cerebral hemispheres and cerebellum (Antoni et al. 1993). If any MR signal changes are present in subcortical structures (putamen) and midbrain, then secondary syndrome of parkinsonism is likely. In patients older than 40 years of age, signs of vascular encephalopathy as a distinct nosology may be revealed. It is important to differentiate MR signs typical for PD and secondary changes of the brain parenchyma of vascular (or another) origin. In PD on Т2-weighted imaging and especially in the T2 gradient echo sequence, more sensitive to magnetic field heterogeneity, the following MR signal changes are seen. In some patients, normally decreased signal intensity of the reticular part of substantia nigra and red nuclei disappears due to loss of melanin-containing neurons. In other patients, confluence of areas normally hypointense in these sequences is seen due to deposition of iron in the compact and the reticular parts of substantia nigra, as well as in red nuclei, which is accompanied by a mild hyperintensity on Т1-weighted imaging. In thorough study of midbrain on Т1- and Т2-weighted imaging with decreased field of view (FOV) and especially in the T2 gradient echo sequence, these changes are better seen. Dot-like areas of hyperintense sig-
Neurodegenerative Disorders of the Central Nervous System
1077
nal may be seen on T2-weighted imaging in the compact part of substantia nigra. In Wilson’s disease, chronic hepatitis and manganese intoxication a paramagnetic effect influences on MR signal involving large regions—basal ganglia (putamen, caudate nucleus). Demyelination of striatonigral descending pathways accompanies these changes, which differentiates these disorders from PD (Duguid et al. 1986; Braffman et al. 1988; Huber et al. 1990; Gorell et al. 1995). It should be noted that in patients with pharmacologically resistant forms of parkinsonism surgical treatment may be applied—chronic stimulation of subthalamic nuclei after stereotactic implantation of micro-electrodes (Fig. 14.1).
may develop on the final stages (Yakhno and Shtulman 2001). Mild or moderate decrease of brain weight, dilatation of sulci in frontal and parietotemporal regions and dilatation of the lateral ventricles are seen. On microscopy depigmentation, neuronal loss, and gliosis of substantia nigra and locus coeruleus are found. The main pathological sign of the disease is a large quantity of Lewy bodies in the midbrain and hypothalamus, basal ganglia, inferior olives, brainstem reticular formation, dentate nuclei of the cerebellum, and even in several structures of the spinal cord. Lewy bodies are insoluble aggregates of the alpha-synuclein protein. Additional changes are represented by senile plaques and neurofibrillary tangles, which are primitive in their morphology and the extent of maturity; in contrast to Alzheimer’s disease, they lack a clear amyloid core and minimally presented in the hippocampus. Features are nonspecific. Except for mild brain atrophy and concomitant challenging vascular changes no other changes are revealed (Scott et al. 2002). The absence of changes in hippocampi on MRI differentiates Alzheimer’s disease from Lewy body–like disease, as their clinical pictures resemble each other.
14.2.2 Lewy Bodies Disease Dementia with Lewy bodies is a sporadic disease, which was for the first time described only in 1960s and 1970s. Reliably confirmed familial cases were not described. Until now, the nosological relationship of the disease is a subject of discussion. Some authors regard diffuse Lewy bodies disease a distinct nosological entity, and others think that PD and Lewy bodies disease are the identical nosology. The aetiology and pathogenesis of the disease are unclear. The main link in the pathogenesis is the impairment of alphasynuclein conformations that form the basic component of abnormal intracellular inclusions found in this disease: Lewy bodies. Clinical features of the disease are directly correlated with quantity and distribution of Lewy bodies in the CNS structures (see below) and are manifested by a combination of parkinsonism syndrome and dementia. The disease usually starts in the sixth to eighth decade of life; however, cases with earlier onset have been described. A typical presenting symptom is memory impairment, and less frequently, the disease presents with parkinsonism. Total frontal-type dementia resembling that in Alzheimer’s disease develops through the course of the disease. Anterior horn involvement is seen in some patients also. Quadriplegia and/or apallic syndrome
14.2.3 Multiple Systemic Atrophy Before J. Graham and D. Oppenheimer in 1969 coined the term of multiple systemic atrophy (MSA); different clinical variants of the disease were previously described as olivopontocerebellar degeneration, striatonigral degeneration, and Shy-Drager syndrome. It is a sporadic disease; no familial cases have been described. The prevalence of the disease is 4 cases per 100,000 population. The role of several exogenous toxins such as pesticides, formaldehyde, hexane, etc. in individuals with possible genetic predisposition is discussed. Genetic defects have not been mapped. The disease pathogenesis is linked to abnormality of alpha-synuclein conformation and deposition of its insoluble aggregates in the CNS. In contrast to other synucleinopathies,
Fig. 14.1a–c Surgical treatment of Parkinson’s disease. Implantation of micro-electrodes into the subthalamic nuclei. Т2-weighted imaging (a) at the level of basal ganglia and midbrain, and sagittal Т1- and coronal Т2-weighted imaging (b,c)
1078
deposits of alpha-synuclein are revealed in MSA not only in the degenerating neurons, but also in large quantities in oligodendroglia. The latter occurred to be an unexpected finding, as in normal state alpha-synuclein is located predominantly in neurons. Accumulation of alpha-synuclein in oligodendroglia may possibly be connected with increased level of its expression in glial cells, or with loss of such a function in oligodendroglia as alpha-synuclein degradation. The disease starts on the fifth or the sixth decades of life and inevitably progresses; survival since onset is less than 10 years. Neurological signs are often presented with three of initially described variants: olivopontocerebellar syndrome (ataxia, bulbar syndrome, and to a lesser extent by parkinsonism syndrome and autonomic dysfunction), striatonigral syndrome (the leading is a parkinsonism syndrome with mild cerebellar and pyramidal signs), or by Shy-Drager syndrome (the dominating sign is arterial orthostatic hypotension and other autonomic signs caused by degeneration of brainstem reticular formation nuclei, with other groups of nuclei being involved to a less extent). Widespread neuronal loss and gliosis of basal ganglia, brainstem, and cerebellar nuclei are observed (Rebeiz et al. 1968). In addition to the deposits of alpha-synuclein in neurons, another specific feature of the disease is the picture of multiple argyrophilic cytoplasmic inclusions in oligodendroglia, which are not only alpha-synuclein- and ubiquitin-, but also tau-positive (tau-positive inclusions are typical for taupathies, see below). These inclusions differentiate the MSA with polyglutamine disorders with resembling clinical manifestations (for instance, several spinocerebellar degenerations). MRI changes seen in MSA especially in its olivopontocerebellar variant, and may resemble those in several spinocerebellar degenerations (SCD, see below). In the olivopontocerebellar variant of MSA marked atrophy of cerebellum and all of its peduncles, pontine atrophy, and dilatation of pontocerebellar cisterns are seen. On axial MRI, in all sequences on slices at the level of pons MR images reveal changes in the configuration of pons in a way of flattening of its anterolateral surfaces bilaterally and, along with atrophy of the middle cerebellar peduncles, which produce a figure of a triangle or an isosceles trapezium, with the apex facing the prepontine cistern. On T2-weighted and FLAIR images, done at this level, demyelination of the transversal fibres of pons is seen. This, along with CSF pulsatile motion artefact in the dilatated interpeduncular cistern, produce a sign of a cross, which crosses the pons, with hyperintense signal (Fig. 14.2). Such signal changes are not found in ataxias due to cerebellar or vermal hypoplasia. In MSA cerebellar atrophy with dilatation of the subarachnoid spaces between its folia and dilatation of the fourth ventricle are seen. On sagittal median MR slices, the anterior surface of pons looks flattened. Besides, on Т2-weighted images and especially on the T2 gradient echo sequence, iron and neuromelanin deposits are seen in basal ganglia (striatum), especially in the striatonigral variant of MSA. In MSA presented as Shy-Drager syndrome, the same changes of brainstem as in the olivopontocerebellar variant of MSA are seen with marked atrophy of cerebellum and its peduncles (Savoiardo 1989). MR differentiation of MSA variants is impossible at present.
Chapter 14
In addition, the differential diagnosis between MSA and the group of spinocerebellar degenerations should be made, but what is also often impossible by MRI. DNA diagnosis is crucial to reveal SCD.
14.3 Taupathies The term taupathies determines the distinct group of ND with parkinsonism syndrome. The leading pathogenetic factor is an accumulation of neurofibrillary tangles (NFT) in the neuronal and glial cells cytosol. NFT are the aggregates of the tau protein. The tau protein is linked with a microtubular apparatus of neurons, and in the normal state proceeds polymerisation of a monomeric tubulin during the folding of microtubules of neuronal cytoskeleton, maintaining its stability. Impairment of the tau protein conformation in taupathies leads to down-regulation of its connections with microtubules, its release and aggregation, impairment of the cytoskeleton, and neuronal loss.
14.3.1 Progressive Supranuclear Palsy Progressive supranuclear palsy (Steel-Richardson-Olszewski syndrome) is a second frequently encountered parkinsonian syndrome of degenerative aetiology (after Parkinson’s disease). It was first described in 1963–1964 by Canadian physician J. Steel and American physicians J. Richardson and J. Olszewski (1964). The prevalence of the disease is 5 cases per 100,000. In most cases it is sporadic; a few familial cases are revealed with autosomal dominant inheritance and incomplete penetrance of the mutant tau protein gene mapped on chromosome 17. The aetiology of hereditary form of the disease is linked to the mutation of tau protein, which leads to impairment of its correct conformation. It is supposed that the following factors may influence the progression of progressive supranuclear palsy with the “unfavourable tau haplotype”: nerve growth factor and the excitotoxin glutamate, which increase the tau protein gene expression in cell cultures of neurons; thyroid hormones regulating mRNA splicing and the ratio of tau proteins isoforms in the developing brain; the excess of Са2+ and Mg2+ ions stimulating the aggregation of tau filaments; increased lipid peroxidation and defects of oxidative phosphorylation; and carrier state of the ε4 allele of apolipoprotein-Е. The knowledge about the disease pathogenesis is limited to the selective neuronal loss in basal ganglia and brainstem due to their cytoskeleton instability caused by abnormal conformation of the tau protein mediated by genetic or environmental factors. The disease starts in middle age or older and is manifested by a triple of symptoms—gaze palsy, pseudobulbar syndrome, and parkinsonism syndrome with peculiarities. Ocular movements are at first impaired in the vertical plane, and then gradually the internal ophtalmoplegy develops, with retraction of the upper eyelips and the central fixation of gaze, which looks like a constant expression of surprise. The pseudobulbar syn-
Neurodegenerative Disorders of the Central Nervous System
1079
Fig. 14.2a–f Multiple systemic atrophy (the olivopontocerebral vari-
better on proton density images, demyelination of the transverse pontine fibres is seen. There is a flattening of the anterior pontine surface on sagittal Т1-weighted imaging (f)
ant). Т2-weighted imaging (a–d) and proton density–weighted imaging (e): atrophy of pons, inferior olives, and cerebellar peduncles is seen with dilatation of basal cisterns. On Т2-weighted imaging, and
drome and parkinsonism syndrome also develop with accompanying dystonia of axial muscles and absence of tremor in rest, which differentiates this disease from PD. The course of Steel-Richardson-Olszewski syndrome in inexorably progressive with prominent disability; the main sign leading to disability is hypokinesia. Survival never exceeds 5–7 years. Neuronal loss is found in basal ganglia (mainly in globus pallidus and the subthalamic nuclei), red nuclei, para-aqueductal grey matter, superior colliculus, pontine and brainstem nuclei, and frontal and temporal lobes of the cerebral hemispheres. On microscopy, aggregates of tau protein are found in neurons and glia (spike-like astrocytes) of the mentioned structures. There are no specific changes on CT. Cavitation of tectum and tegmentum of midbrain, striatum, and caudate nuclei may be seen on MRI. This cavitation cannot be differentiated from that seen in lacunar vascular encephalopathy. Lacunar changes are often not found; only atrophy of the upper por-
tions of midbrain, especially of lamina tecti, is seen. MR signal changes are seen in substantia nigra and red nuclei resembling those seen in PD (see above), mild hyperintense signal in the peri-aqueductal grey matter. Hypointense signal may be seen on T2-weighted imaging in the lateral segments of globus pallidus due to iron deposits. Differential diagnosis should be made with MSA, PD and Lewy body disease (Savoiardo 1989; Valk et al. 2003).
14.3.2 Frontotemporal Dementia Frontotemporal dementia comprises 15–20% of all cases of primary degenerative dementias; its prevalence in individuals older than 60 years may reach 30 cases per 100,000. There are such variants of the disease as pallido-nigral degeneration, Pick’s disease, and several other forms, in particular, it may coincide with amyotrophic lateral sclerosis (ALS) and may be a
1080
component of ALS–parkinsonism–dementia complex (Guamanian syndrome). According to modern concepts, all these dementias are variants of the same disorder. Familial (30– 50%), and sporadic cases have been described. It is supposed that the part of sporadic cases may be linked with the incomplete penetrance of the mutant gene or with the lack of precise information about familial history. Half of familial forms are linked with mutations of the tau protein gene on chromosome 17. For other cases, genes have not been mapped. Aetiology and pathogenesis are common for all taupathies. The first signs of the disease usually manifest after the age of 50. The clinical picture is characterised by a progressive frontal dementia with motor deficits. Apathy, disinhibition, and the lack of spontaneous behaviour are typical features. Further signs include intellectual impairment, capacity to construe a motor program, motor aphasia, and acalculia manifest with social de-adaptation of a patient. The relative preservation of memory and spatial orientation are the peculiar features of the disease. Five to 10 years after the disease onset, motor deficits join in a way of parkinsonism syndrome and ataxia. In some patients pyramidal signs, oculomotor palsies, amyotrophies, seizures, and incontinence are also seen. On autopsy, marked atrophy of the frontal and the temporal cortices are seen. On microscopy, there is a large cortical neurons loss, cortical spongiosis and gliosis, degeneration of basal ganglia, substantia nigra, dentate nuclei and cerebellar cortex, hippocampi, and anterior horn cell of the spinal cord (the latter is seen in ALS–parkinsonism–dementia complex). NFT (tau precipitates) are found in astroglia and degenerating neurons). In 20% of cases, balloon-shaped cells are found in the brain tissue, which are Pick bodies with tau-positive inclusions. CT and mainly MRI reveal dilatation of the subarachnoidal spaces in the frontoparietal–temporal regions due to atrophy of cerebral gyri, with marked thinning of the latter, dilatation of the lateral ventricles, especially their anterior horns, which is better seen on the late stages of the disease. These findings are specific. Perfusion imaging, SPECT, and PET reveal the decrease of cerebral blood flow and metabolism in the anterior regions of the cerebral hemispheres and in basal ganglia (Kamo et al. 1987).
14.3.3 Corticobasal Degeneration Corticobasal degeneration (CBD) is a sporadic neurodegenerative disorder that develops mainly in the elderly with the asymmetrical syndrome of parkinsonism, with accompanying dystonia, myoclonus, tremor and cortical involvement. Familial cases have not been described. It was first described by J. Rebeitz in 1968. At present, about 100 known cases of this disorder exist. The main pathogenetic mechanism of CBD, as well as in progressive supranuclear palsy, is an impairment of ratio between the main isoforms of tau proteins with excess of the 4R conformer, which leads to increased affinity of the 4R-tau protein to tubulin, and, hence, to slowing of the axonal trans-
Chapter 14
port via microtubules. After that, there occurs a cytosolic accumulation of several neurofilaments, which are concurrently linking with tubulin, and precipitation of abnormal protein inclusions in neurons, with further apoptotic death of the latter by apoptotic mechanism. The aetiology of splicing impairment of the tau protein gene in CBD is still unexplained. Due to resemblance of clinical, morphological, and molecular mechanisms of CBD to other taupathies first of all, and then progressive supranuclear palsy and frontotemporal dementia, there exist doubts about the nosological distinction of CBD. The disease starts at the ages of 50–70 years. Initial signs of CBD are loss of dexterity of one of extremities with impairment of complex sensations (discrimination sense, astereognosis, etc). The symptoms slowly expand on the second ipsilateral and then on the contralateral extremities. After that, akinetic rigid syndrome, dystonia, tremor, cortical myoclonus, and pyramidal symptoms ensue. Parkinsonism syndrome is asymmetrical. Frontal gait apraxia, pseudobulbar dysarthria, and rarely, dysphagia are seen. In 90% of CBD cases, all types of apraxia develop. It is typical for CBD patients to develop “alien hand” syndrome, frequently observed in the primarily affected extremity due to lesion of the contralateral thalamus. Diagnostic criteria for CBD require three of the following signs: levodopa-resistant parkinsonism, alien hand syndrome, apraxia or complex sensory loss, focal limb dystonia, severe postural or kinetic tremor, and myoclonus. Patients usually die 5–10 years after onset, being confined to bed due to secondary complications (Riley et al. 1990; Yakhno and Shtulman 2001). Atrophy of the frontotemporal cortex, often asymmetrical, and signs of hydrocephalus due to cerebral atrophy are seen. Microscopic finding do not differ from those in progressive supranuclear palsy. Tau-protein aggregates are identified in the affected neurons and glia (Gibb et al. 1990). Neuroimaging usually reveals diffuse cerebral atrophy, often asymmetrical, with predominant involvement of the frontal and the temporal lobes on the side contralateral to clinical signs (Fig. 14.3). CT, MR perfusion studies, and cerebral angiography reveal the decrease of cerebral blood flow, and SPECT and PET investigations detect hypometabolism in cortical and subcortical regions, predominantly on the most affected side (Neary et al. 1987).
14.4 Cerebral Amyloidoses Amyloidoses is a group of disorders in which conformation impairment of various proteins leads to their insolubility and deposition of proteopolysaccaride complex (amyloid) in the extracellular space of various tissues and organs, including the CNS. The pathogenesis of cerebral amyloidoses is linked with conformational impairment of neuronal and glial proteins of the CNS, and amyloid depositions are detected predominantly in these structures, causing the psychiatric and neurological symptoms. Several amyloidoses are genetically determined and caused by impairment of the amino acid structure of proteins encoded by the mutant genes. Other,
Neurodegenerative Disorders of the Central Nervous System
1081
Fig. 14.3a–c Corticobasal degeneration. The rightward “alien hand”
elination in basal ganglia and the deep white matter. On the coronal image (c) there is a hyperintense signal in the left thalamus contralateral to the alien hand syndrome (arrow)
syndrome. Axial MRI (a,b): asymmetrical atrophy of the cerebral hemispheres is seen, more to the left, with areas of atrophic demy-
sporadic, amyloidoses are due to conformational impairment of proteins on the posttranslation stage.
14.4.1 Alzheimer’s Disease The disease is a leading cause of dementia in the modern world and, hence, is a keen social problem. Alzheimer’s disease (AD) at present affects over 20 million people worldwide. The prevalence is about 3% of all population older than 65. It is several times more frequently observed in women, manifests with progressive cognitive decline, and the first and predominating sign is a memory loss. Acute psychotic episodes may occur with delusions, hallucinations, and delirium. Hyperkinetic syndrome, parkinsonian syndrome, and seizures are less frequently seen. The mean survival is 10 years, but sometimes the disease slowly progresses over 15–20 years and terminates with total decline of personality, aphasia, and general emaciation. Over 50% of cases are sporadic and have multifactorial origin. Among various hereditary forms with different penetrance, there are 3–10% of true monogenic forms with a complete penetrance of a mutant gene, and another gain a
complete penetrance by the age of 60–65. At present, three genes have been mapped: chromosome 21p21, beta-amyloid precursor protein (APP) gene, and preseniline genes mapped on chromosomes 14q24.3, and 1q31–42, with a chaperon-like function not yet fully understood. Unfavourable genetic factors leading to AD in 50% of cases are the carrier state for alleles of apoplipoprotein-T gene, neuronal receptor alpha-2macroglobuline gene, and APP-processing modulating protein—nicastrin (Illarioshkin 2003). On autopsy, microscopy usually reveals diffuse cerebral atrophy with predominant involvement of the parietal and the occipital lobes. The typical microscopic features are extracellular amyloid plaques with green fluorescence on confocal microscopy dyed with Congo red (beta-amyloid and a peptide fragment of alpha-synuclein) and neurofibrillary tangles in the degenerating neurons. Neuronal loss and destruction of synapses with glial proliferation around the amyloid plaques are seen along with solitary or numerous Lewy bodies. These changes are more prominent in cerebral cortex, predominantly in hippocampi. AD is characterised by maximal involvement of hippocampi in contrast to other ND. Targeted study of temporal lobes in coronal planes reveal asymmetrical atrophy of hippocampi
Fig. 14.4a,b Alzheimer’s disease. Т2-
weighted imaging at the level of uncal hippocampus (a,b) detects marked atrophy with thinning of cortex and the white matter. The dilatation of the temporal horns of the lateral ventricles and the parahippocampal fissures are observed
1082
with cortical thickening, dilatation of Bisha fissure bilaterally and the temporal horns of the lateral ventricles (Scott et al. 2001). These changes are the earliest (Fig. 14.4). Atrophy of the parietal and the occipital lobes is also revealed with dilatation of their external subarachnoidal spaces. For early imaging, diagnosis of AD at present MRS is widely used. Decreased NAA-Cr ratio without changes of ratio of other metabolites is revealed in hippocampi on both sides on spectrograms from patients with clinically suspected AD, which is evident for primary degeneration of neurons. As a rule, these changes on MRS occur earlier than any changes detected on MRI. Nevertheless, the same both-sided MRS changes are also characteristic for another disease, for instance mesial temporal sclerosis. SPECT and PET in AD patients reveal decreased metabolism in hippocampi and parieto-occipital regions.
14.4.2 Cerebral Amyloid Angiopathy Cerebral amyloid angiopathy (CАА, amyloid angiopathy with intracerebral haemorrhages) is observed in 5–10% of all cases of nontraumatic haemorrhages in the elderly. Most cases are sporadic. On rare occasions, the disease is familial: hereditary (familial) cerebral haemorrhage. Inheritance is autosomal dominant; mutation was found in exon 17 of the transmembranous amyloid precursor protein gene on the 21q21 chromosome locus (Dutch-type CAA). As mentioned above, other mutations in exons 16 and 17 of this gene lead to AD. The gene of British-type CAA is mapped on chromosome 13q14 and encodes a membrane protein with unknown function. “Probable” diagnosis of all types of CAA requires the following features: age over 60, multiple spontaneous hemispheric haemorrhages in cortical and subcortical regions without obvious causes, and multiple hypointense areas revealed on Т2-
Fig. 14.5a–c Cerebral amyloid angiopathy in a 60-year-old patient.
Along with cerebral atrophy with dilatation of the external subarachnoid spaces and the lateral ventricles (a,b) multiple foci of small haemorrhages in the chronic stage are seen as areas of hypointense
Chapter 14
gradient echo images, which are petechiae with haemoglobin degradation product depositions. Final diagnosis of CAA is made after histology. The disease is characterised by amyloid deposits in the walls of small, usually cortical and leptomeningeal arteries with thinning and further rupture of their walls. In contrast to haemorrhages in arterial hypertension, multiple small haemorrhages in the subcortical brain areas with relative preservation of basal ganglia are typical for amyloid angiopathy. That is why detection on CT and MRI multiple small haemorrhages of different “age” in an elderly patient without arterial hypertension is supposed to be a typical feature of the disease (Fig. 14.5). Small petechial haemorrhages are better visualised on T2 gradient echo images as hypointense areas due to influence of haemosiderin deposits. However, solitary and large haemorrhages may be found, in particular, deep-seated ones. The differential diagnosis in elderly should be made between CAA and chronic ischaemic brain disease of hypertonic origin and with acute hypertonic encephalopathy.
14.4.3 Transthyretin-Associated Amyloidoses This is a group of amyloidoses of various organs and tissues, due to hereditary or sporadic impairments of transthyretin conformation, which is a transport protein responsible for thyroxin- and retinol-binding peptides transport. Cerebral transthyretin-associated amyloidoses are caused by rare mutations of the transthyretin gene (on chromosome 18q11.2– 12.1), which may initiate predominant CNS involvement with amyloid deposition in the brain. Clinical picture is characterised by variable age of onset (17–80 years), by different neurological symptoms (progressive dementia, spastic pareses,
signal on Т2-weighted imaging (c). On Т2* gradient echo sequence, small petechial subcortical haemorrhages are clearly seen in comparison with routine MRI
Neurodegenerative Disorders of the Central Nervous System
1083
seizures), and by relapsing parenchymal and subarachnoidal haemorrhages. The disease often remains unrecognised during throughout life, and patients are usually being followedup with other diagnosis. Diagnosis during lifetime is possible if DNA screening of the transthyretin gene is performed; otherwise, diagnosis is made only on autopsy. Neuroimaging diagnosis is nonspecific and has no differences from features of cerebral amyloid angiopathy. Signs of typical subarachnoidal and parenchymal haemorrhages are revealed. Relapsing course in young patients may raise suspicion of the correct diagnosis. In addition, superficial and parenchymal haemosiderosis as a result of old haemorrhages of different “age”. Cerebral atrophy, vascular demyelination, and gliosis are seen.
may develop in any age (cases are described in people over 15 years of age), with an incubation period from 4 to 30 years. EEG findings typical for CJD are pathological complexes acute wave–slow wave (Kretzschmar 1996; Zuiev et al. 1999). The clinical picture of Gerstmann-Sträussler-Scheinker syndrome resembles that of CJD; however, the leading symptom is ataxia, the disease has milder course, and death comes 2–10 years after onset. Fatal familial insomnia is characterised by impairment of sleep–wake cycle and several autonomic signs, which indicates damage of reticular formation of the brainstem. Amyotrophic leukospongiosis was described in Belarus inhabitants, and its nosological distinction is a subject of discussion (it may be a variant of CJD), but it differs from the latter by multiple peripheral palsies and predominant loss of spinal motor neurons on pathology along with spongiform changes of the CNS. The prion protein was inoculated in cases of this disease, which may also be familial or sporadic. Kuru, the first prion disease described in humans, was discovered in Papua New Guinea native inhabitants, who consumed human brains. Due to eradication of cannibalism, it is not found at present. Largely, in all prion diseases atrophy of cerebral hemispheres, decrease of brain volume and weight are seen. Microscopy reveals the following typical signs: spongiform vacuolation of the grey matter, secondary demyelination and astrogliosis, neuronal loss in all regions of the CNS, and amyloid depositions containing the prion protein PrPSc. There are several pathomorphological peculiarities specific for different forms of prion diseases due to predominant involvement of these or those CNS structures. It is important that in most transmissive cases, the prion protein is found in peripheral lymphatic tissues, which makes possible the alive diagnosis of a prion disease basing on histology of a puncture material of lymphatic nodes (Illarioshkin 2003). Neuroimaging is used more in cases of CJD. However, according to most authors, MR features of CJD are heterogeneous. In the iatrogenic variant, the earliest CJD signs are hyperintense signal on Т2-weighted and FLAIR images in dorsomedial thalamic nuclei, which is often symmetrical (DiRocco et al 1993; Barboriak et al. 1994; Bahn et al. 1997; Valk et al. 2003). Later these changes expand onto putamina and heads of caudate nuclei (Gertz et al. 1988; Will et al. 2000). In 83% of cases, hyperintense signal is noted in the peri-aqueductal grey matter of midbrain, most frequently in familial fatal insomnia. In CJD, hyperintense signal in these sequences is seen in centrum semiovale of both cerebral hemispheres, which may be very extensive, especially on the late stages of the disease (Kruger et al. 1990). Total demyelination of the white matter of cerebral hemispheres is sometimes seen. In some cases, there are no MR signal changes, and the disease manifests on MRI by progressive cerebral atrophy (Vrancken 2000). Many studies have been done in prion diseases with MR diffusion and MR spectroscopy (Demaerel et al. 1997; Сraham et al. 1993). However, no specific changes have been revealed by these techniques, but they are slightly more sensitive to pathological changes in the brain, which reflect the course of neurodegeneration. Differential diagnosis should be made be-
14.4.4 Human Prion Diseases (Spongiform Encephalopathies) The group of primary cerebral amyloidoses characterised by deposits of amyloid in brain parenchyma, with abnormal prion protein PrPSc being one of the main components of deposits. Several prion diseases in animals are known: scrapie in sheep, bovine spongiform encephalopathy, deer-emaciating diseases, etc. The prevalence of relatively recently described human prion diseases (beginning in the 19070s) is about 1 case per 1 million; however, it increases yearly. At present several forms of human prion diseases are described: • Creutzfeldt-Jakob disease –– Hereditary form –– Iatrogenic transmissive form • Gerstmann-Sträussler-Scheinker syndrome • Fatal familial insomnia • Amyotrophic leukospongiosis • Kuru The unique character of prion diseases is based on the fact that they may be hereditary (genetically determined by a mutation in the prion protein gene PRNP, locus 20p12-pter), as well as sporadic due to transmission of the prion protein from a patient via food or transplantation of organs, via the lymphatic system. In hereditary forms, impairment of normal human prion protein conformation (the protein function id still unexplored) PrPС is seen, with synthesis of its pathological conformer PrPSc. In addition, the already-synthesised pathological prion protein PrPSc, which may be produced in small quantities (for instance, in cases of incomplete penetrance of the mutant gene), is capable of changing the conformation of normal prion protein PrPС, transforming it into PrPSc. Hypothetically, a single molecule of PrPSc is sufficient for the development of prion disease (Prusiner 1987). The most thoroughly studied disease of this group is Creutzfeldt-Jakob disease (CJD). The hereditary form onset is between 45 and 70 years. The disease is characterised by subacute cortical dementia with rapid cognitive decline, generalised seizures, and myoclonus, and parkinsonism syndrome. The average survival is 6 months; less frequently the disease may progress for several years, and death ensues after complete decortication and coma. The iatrogenic variant of CJD
1084
tween encephalitides, organic acidurias in children, and toxic injuries (CO poisoning, addictions to organic solvents).
14.5 Spinocerebellar Degenerations Spinocerebellar degenerations (SCD) is the most abundant group of ND, comprising about 50 distinct nosological entities. They are Friedreich’s ataxia (the mitochondrial disorders with mutations of the nuclear gene), AVED syndrome, polyglutaminic autosomal dominant SCD (about 17 distinct entities in this subgroup was revealed), episodic autosomal dominant ataxias, autosomal recessive SCD, and several SCD with unclear pathogenesis (Yakhno and Shtulman 2001; Illarioshkin 2003). Diseases that are members of this group have different molecular genetic aetiology and pathogenesis, different age of onset, but they have common clinical and pathological findings. For all of these diseases, the leading syndrome is cerebellar ataxia with other cerebellar signs present to this or that extent (nystagmus, dysarthria, megalographia) as well as pyramidal signs and motosensory polyneuropathy. Pathologically, all these diseases are characterised by degeneration of posterior and lateral columns of the spinal cord, dentate nuclei and vermis, cerebellar peduncles and olives, in several forms—atrophy of the cerebellar cortex, brainstem nuclei, spinal motor neurons, and demyelination of the cerebellar white matter and ascending and descending pathways of posterior and lateral columns of the spinal cord. Neuroimaging of different forms of SCD according to CT and MRI, even with high resolution, is nonspecific. Thus, we believe that it is not feasible to describe neuroimaging of separate forms of SCD in this chapter. However, the entire group possesses common features, which assumes diagnosis of SCD according to MRI data. The most prominent changes are seen in Friedreich’s ataxia. There are no signal changes in the white matter of cerebral hemispheres. Their volume is not changed in contrast to MSA; sometimes MRI reveals dilatation of its external subarachnoidal spaces. Atrophy of pontine, inferior
Chapter 14
olives, cerebellum, and its peduncles analogous to those describes in the olivopontocerebellar variant of MSA are seen (see above) (Fig. 14.6). In several forms of SCD, only cerebellar atrophy, especially of vermis, is found. In all SCD, thinning of the spinal cord without signal changes is typical. It is difficult to say to what extent these or those changes are present in particular forms of SCD, as specific research is necessary with study of correlations between molecular genetic and neuroimaging data. Brainstem atrophy without hemispheric lesions (in contrast to MSA) allows a radiologist to diagnose SCD with more probability. These changes with signs of the spinal cord atrophy are also more typical to SCD than to hereditary spastic paraplegia variants (see below), in which usually MR changes in cerebellum and brainstem are absent (Scott et al. 2001).
14.6 Huntington’s Disease Huntington’s disease is an autosomal dominant hereditary ND first described by American psychiatrist G. Huntington in 1872. The disease prevalence is 2–10 cases per 100,000. Sporadic cases are not known. The onset of the disease is usually about 30–50 years of age. The malignant juvenile Westphal variant is characterised by onset at 20 years. Sometimes onset in the elderly is observed. The mutant gene characterised by complete penetrance is mapped on chromosome 4p16.3 and encodes the huntington protein, which presumably participates in the endocytosis and the cytosolic transport in neurons. Increase of trinucleotide tandem repeats of cytosine–adenine–guanine (CAG) in the huntington gene from for 38–121 repeats (in healthy people there are less than 33 repeats). The more CAG repeats that are present, the earlier is the disease onset (the anticipation phenomenon). Other mutations have not been described, which is why DNA diagnosis is very effective, and positive familial history in a primarily diagnosed patient clearly point out the nosology. The mechanism of action of mutant huntington is
Fig. 14.6a–c Friedreich’s ataxia (a) and cerebellar atrophy in chronic alcoholism (b,c). Two cases
Neurodegenerative Disorders of the Central Nervous System
1085
not known. GABA-ergic neurons in putamen and caudate nucleus are primarily lost—these neurons give the origin of the “indirect” striopallidar pathway. The inhibitory input of striatum on the external segment of globus pallidus occurs with activation of ascending thalamocortical pathways and development of choreic hyperkinesis. In the late stages, neurons of the “direct” striopallidar pathway are lost with disinhibition of the internal segment of globus pallidus and chorea is replaced by akinetic rigidity syndrome. As well, increase of МАО-В enzyme and increase of homovanillic acid occurs in Huntington’s disease, which causes cognitive decline (Illarioshkin 2003). The classic triad of signs in the clinical picture includes choreic hyperkinesis, subcortical type dementia, and behavioural changes (Illarioshkin 2003). Clinical manifestations depend on the stage of the disease and the neurodegenerative process (see above) in corpus striatum (chorea on the initial stage is replaced by akinetic rigidity syndrome in the late stage). The juvenile Westphal form starts with akinetic rigidity syndrome. The disease inexorably progress and survival spans 15–20 years. Pathologically, atrophy of basal ganglia and to a less extent of cerebral cortex is seen, and external and internal hydrocephalus and decrease of brain weight are also noted. Specific histological signs are loss of spike-like neurons of corpus striatum (putamen and caudate nucleus), as well as of medial pert of caudal nucleus since the earliest stage of the disease, which contains amyloid aggregates of the polyglutamine protein huntington. On CT, the dilatation of the anterior horns of the lateral ventricles is seen, often on the late stage of the disease. MRI clarifies that the cause of this is an atrophy of the heads of caudate nuclei and putamina. Morphometric studies detect the decrease of caudate nuclei volume up to 27%. It is known that all basal ganglia in 50% of cases consists of internal white matter. In Huntington’s disease, heterogeneous changes of MR signal on Т2-weighted imaging are seen in putamina due to myelin loss in the putaminal white matter and due to gliosis (hyperintense signal). On the other hand, foci of hypointense signal within them point out on iron deposits (Scott et al. 2001).
Classification of hereditary spastic paraplegia (HSP) according to A. Harding (1993) is cited below: 1. Isolated HSP a. Autosomal dominant, type 1, onset before 35 years of age b. Autosomal dominant, type 2, onset after 35 years of age c. Autosomal recessive d. X-linked (SPG1) mutation in the gene of neuronal adhesion factor Xq28 e. X-linked (SPG2) mutation in genes of proteolipid protein Xq22 (Pelizaeus-Merzbacher disease) 2. Complicated paraplegias: paraplegia and a. Peroneal amyotrophy b. Upper limb amyotrophy—autosomal recessive type (Troyer syndrome) c. Upper limb amyotrophy—autosomal dominant type (Silver syndrome) d. Ichtiosis and retinopathy, mental retardation (SjøgrenLarsson syndrome) e. Cerebellar ataxia (Charlevoix-Saguenay syndrome) f. Pigmental degeneration of retina with mental retardation and optic nerve atrophy g. Myoclonus epilepsy h. Sensory neuropathy i. Choreoathetosis and dystonia j. Athetosis and dementia (Mast syndrome) k. Skin hypopigmentation l. Hearing loss and nephropathy m. Dementia n. Adrenomyeloneuropathy
14.7 Hereditary Spastic Paraplegias This is a heterogeneous group of neurological disorders conditionally and traditionally discussed in the section of ND, the common clinical feature of which is progressive spastic lower paraparesis. Isolated hereditary spastic paraplegia is distinguished, in which 70% of cases correspond to the classical description of German neurologist A. Strümpell (1880). The disease was later names Westphal-Strümpell disease. Complicated forms of the disease involve various forms of hereditary spastic paraplegia. The latter are the most heterogeneous and many of them are now related to other groups of disorders— enzymopathies, mitochondrial disorders, etc.
Spastic, complicated paraplegias are very rare, and their nosological distinction is not yet proven; the genes of most forms are not mapped. It is shown that the form of paraplegia with adrenomyeloneuropathy is an adult variant of adrenoleukodystrophy, Sjøgren-Larsson syndrome, which is an enzymopathy with insufficiency of aldehydedehydrogenase of fatty acids, and they have nothing in common with ND. The lower spastic paraparesis plus dementia is possibly a variant of Alzheimer’s disease, as it is caused by mutation in the preseniline gene on chromosome 14q24.3. In Х-linked lower spastic paraplegias with optic atrophy described in 1964, the mutation OMIM 311000 was revealed, related to hereditary Leber's optic atrophy, which is a mitochondrial disorder. Variants of isolated hereditary spastic paraplegia are caused by mutations in several genes mapped to different chromosomal loci, in particular, autosomal dominant forms (Westphal-Strümpell disease)—to loci 2p, 8q, 12q, 14q, 15q, and 19q. Primary molecular defects have not been explored except the genes of spastin (2p) and paraplegin (16q), encoding synthesis of a protein belonging to mitochondrial ATPases. That may point out a crucial role of impairment of oxidative phosphorylation in the pathogenesis of this disease, and probably the entire group of diseases. As well, on light microscopy of an autopsy material, in all forms of spastic paraplegias, any intraor extracellular inclusions typical for ND are not found. General atrophy of the total length of the spinal cord is
1086
found in the isolated forms of HSP, more in caudal regions, especially in the corticospinal tracts of the lateral columns, along with less prominent changes in the posterior columns and spinocerebellar tracts. In the late stages, corticospinal tracts at the level of brainstem may be involved, with partial, probably, secondary, neuronal loss of Betz cells of cerebral hemispheres. All these findings point out on the primary axonopathy with secondary involvement of neuronal bodies; thus HSP are related to disorders with primary white matter involvement. The most characteristic MR feature of isolated HSP is a general atrophy of the spinal cord along its length without changes of the vertebral channel size (Fig. 14.7). Brain examination usually reveals no pathological signal changes or signs of atrophy. However, MRI can rule out other causes of lower spastic paraparesis clearly—intrauterine hypoxic damage of foetus white matter that leads to children’s spastic paralysis (Little’s disease), adrenoleukodystrophy and especially adrenomyeloneuropathy, bilateral parasagittal meningioma ,and spinal cord lesions of other origin.
14.8 Amyotrophic Lateral Sclerosis Amyotrophic lateral sclerosis (ALS) is one of the most severe ND of the CNS, described for the first time by French neu-
Fig. 14.7a–c Low spastic paraplegia in a 30-year-old patient. On
sagittal Т2-weighted imaging (a), Т1-weighted imaging (b), and Т1weighted imaging with CE (c) of the cervical and the upper thoracic
Chapter 14
rologist Charcot in 1874. The prevalence is 0.4–7.2 cases per 100,000 (Skvortsova and Levitsky 2007). Males are more frequently affected. In typical cases, late onset is after 50–60 years of age. However, there are cases with onset before 50 and even before 40 (5%). The juvenile form is extremely rare. The vast majority of cases are sporadic. Familial ALS cases with autosomal dominant as well as autosomal recessive inheritance account for 10%, their genetic bases is extremely variegated, and by the present time over 100 different causative mutations have been revealed on chromosomes 2, 9, 15, 18, and 21. The most thoroughly studied are mutations in the Cu–Zn superoxide dismutase enzyme (SOD1) gene on chromosome 21q21. The aetiology of sporadic cases is still unexplored, but they are probably linked with different molecular genetic defects that are not elucidated yet. Infrequently the disease starts with an extremity that underwent mechanical or electrical injury long ago. The pathogenesis has not been sufficiently studied. Neuronal loss is linked with a neurotoxic effects of a conformed SOD1 molecule (young-onset forms of ALS), or with changes in the pro-oxidant neighbourhood of motor neurons, which increase with physiological ageing on the background of premorbid mitochondrial defects, impairment metabolism of glutathione, excitotoxic glutamate, and glutamate transport. The final stage of all these processes is an apoptotic death of motor neurons.
spine: marked atrophy of the spinal cord with decrease of its diameter up to 3–4 mm is seen, without any signal changes or pathological enhancement
Neurodegenerative Disorders of the Central Nervous System
1087
The disease is characterised by selective loss of lower spinal and brainstem motor neurons and upper motor neurons. Depending on the predominant localisation of the process, four clinical forms are distinguished: cervicothoracic, lumbosacral, bulbar, and high. The course of the disease could be diffuse or there could be predominance of signs of upper or pyramidal motor neurons involvement. Paresis of skeletal and bulbar muscles, amyotrophies, fasciculations, and spasticity develop. Dysarthria and dysphagia may also develop. Pelvis sphincters are usually preserved. ALS patients have an abnormal skin collagen structure, which may explain a paradoxical absence of bedsores even in patients who are confined to bed. No effective therapy for ALS is available. The disease usually progresses rapidly. Survival rarely exceeds 5 years, and death comes due to weakness of respiratory muscles (diaphragm) due to loss of spinal motor neurons and loss of neurons in brainstem that control respiration. The diagnostic criteria include involvement of three limbs and EMG data. Macroscopic changes of spinal cord are minimal and almost absent in the brain. Thinning of the spinal cord especially its anterior roots is seen. Microscopy reveals significant degeneration of anterior horn motor neurons, typically more prominent at the level of cervical enlargement with predominant loss of alpha-motor neurons. Identical features are seen in brainstem motor nuclei with relative preservation of oculomotor, trochlear and abducens nerves. In addition, degen-
eration of motor neurons in the anterior central gyrus and adjacent areas of the frontal lobes are seen. The loss of white matter that corresponds to axons of these motor neurons is also found (corticospinal tracts on all their way to spinal and bulbar motor neurons). Possibly a part of fibres degenerate secondarily by a dying-back mechanism due to degeneration of spinal motor neurons, and not due to loss of upper motor neurons in the motor cortex. Electronic microscopy reveals axonal spheroids that contain neurofilament-like structures in the degenerating motor neurons. It is thought that there is no specific neuroimaging features of ALS. CT and MRI with low magnetic field strength are not informative. A spinal cord study is also nonspecific even with high quality of imaging equipment. Decreased diameter of the spinal cord with absence of typical lumbar and cervical enlargements may be present. In several cases, especially with a large experience high-magnetic-field strength, brain MRI may contribute to ALS diagnosis (Fig. 14.8). There are no changes on Т1-weighted imaging. On Т2-weighted imaging, and especially on FLAIR images, mild bilateral hyperintense signal within the projection of corticospinal tracts may be seen at the level of cerebral peduncles and the anterior central gyri. These changes reflecting degeneration of the corticospinal tracts on MRI are usually symmetrical or close to symmetrical. The changes are more prominent in centrum semiovale more ventrally to “terminal areas”, which have
Fig. 14.8a–e Amyotrophic lateral sclerosis. A series of Т2-weighted imaging (a,b) and FLAIR (c–e) images reveals a bilateral symmetrical hyperintense MR signal areas in the corticospinal tracts location at the level of midbrain–centrum semiovale. These changes are better seen on FLAIR images as well in axial as in coronal plans
1088
normally high signal on FLAIR images. In the late stages of the disease, changes of the corticospinal tracts may be seen at the level of pons and medulla. Atrophy of the anterior central gyri with enlargement of the central sulcus may also be found. CE is not effective and not indicated, except for cases ruling out any concomitant pathology. DWI does not reveal any significant changes in ALS. Additional information may be obtained from MRS data as a tool for the follow-up observation of ALS patients. MRS reveals a decrease of NAA–Cr ratio in centrum semiovale, and according to several authors, these changes may precede MR signal changes that appear on Т2-weighted imaging and FLAIR images. In our own studies, we noticed cases in which MRS changes were nonsignificant in patients with clinically and laboratory supported ALS. The most complicated is the analysis of MRS data in ALS patients with onset later than 50–60 years of age, when normal NAA– Cr ratio decreases. Interestingly that in our own observations, we encountered with the combination of ALS and vascular encephalopathy in the same patient. If atrophic demyelination due to cerebral atherosclerosis and arterial hypertension is present, then it is very difficult to register MR signal changes in the corticospinal tracts typical for ALS. MRI is also effective when the differential diagnosis is made between ALS and cervical myelopathy with ALS-like syndrome. In these
Chapter 14
cases, detection of the spinal cord compression at the level of cervical enlargement (listhesis, disc herniation, spondylosis, etc.) may cause hesitation in the diagnosis of ALS even if the above-mentioned MR signal changes in the brain are present. However, on rare occasions, the combinations of ALS and cervical myelopathy have been described, when ALS was proven clinically and by electromyography, DNA testing, and autopsy. We have observed one such occasion (Fig. 14.9). In the late stages of ALS when clinical diagnosis is doubtless, MRI clearly reveals degeneration of corticospinal tracts with isolated atrophy of anterior central gyri (Fig. 14.10). The differential diagnosis in ALS should be made between Wallerian degeneration of upper motor neurons and their axons in the corticospinal tracts described in cranio-cerebral injury, after intracerebral haemorrhage, and demyelinating disease, etc. (Fig. 14.11). In these cases, MR signal changes are usually observed in the corticospinal tracts contralateral to hemiparesis and may be descending or ascending in their origin (Kuhn et al. 1989; Pennock et al. 1993; Sawlani et al. 1997; Mazumdar et al. 2003). Concluding the chapter, we present the following Table 14.1, with main neuroimaging features of neurodegenerative disorders of the CNS. We hope that this data may help in the differential diagnosis of different ND.
Fig. 14.9a–d The combination of ALS and cervical myelopathy. In a patient with proven ALS by clinical and EMG findings, there is a herniation of the С5–С6 intervertebral disc with compression of the spinal cord. A focus of myelopathy is seen on sagittal and axial Т2-weighted imaging (a,b). c,d see next page
Neurodegenerative Disorders of the Central Nervous System
1089
Fig. 14.9a–d (continued) The combination of ALS and cervical myelopathy. In a patient with proven ALS by clini-
cal and EMG findings, there is a herniation of the С5–С6 intervertebral disc with compression of the spinal cord. Brain MRI reveals no clear signal changes in the corticospinal tracts even on FLAIR images (c,d), which does not contradict at the diagnosis
Fig. 14.10a–f ALS, the late stage. A series of FLAIR MR images (a–d) reveal prominent hyperintense signal in the corticospinal tracts bilaterally at the level of both centrum semiovale and atrophy of the precentral gyri. Functional MRI (e) shows that the spot of activation
of the left arm motion (motor cortex for the arm) coincides with the area of hyperintense signal. MRS of the affected area reveals the decrease of the NAA–Cr ratio without changes in any other metabolites, what is a feature of neurodegenerative process (f)
1090
Chapter 14 Fig. 14.11a–f Wallerian degeneration of the left corticonuclear tract in a patient 12 months after the intracerebral haemorrhage. Linear posthaemorrhagic cyst in the posterior portions of the left frontal lobe is observed (a–c). Axial FLAIR (d,e) and coronal Т2weighted imaging (f) reveal hyperintense signal in the left corticospinal tract of secondary origin
Neurodegenerative Disorders of the Central Nervous System
1091
Table 14.1 Neuroimaging features of neurodegenerative disorders Neurodegenerative disorders 1. Synucleinopathies Lewy body disease a. Parkinson’s disease b. Dementia with Lewy bodies Multiple systemic atrophy 2. Taupathies Progressive supranuclear palsy Frontotemporal dementia
Corticobasal degeneration 3. Cerebral amyloidoses Alzheimer’s disease Cerebral amyloid angiopathy Transthyretin-associated amyloidoses Prion diseases 4. Polyglutamine diseases Spinocerebellar degenerations Huntington disease
Neuroimaging features
Iron deposits in substantia nigra Typical changes in the lower brainstem and cerebellum
Cavitation of tectum and tegmentum of midbrain Marked atrophy of the frontotemporal regions with thinning of gyri and dilatation of the anterior and temporal horns of the lateral ventricles. Decreased cerebral blood flow and metabolism in these regions Diffuse asymmetrical cerebral atrophy. Decreased cerebral blood flow and metabolism in these regions Predominant lesions of hippocampi Multiple small and large parenchymal and subarachnoidal haemorrhages Predominant involvement of basal ganglia. Variable neuroimaging picture
Specific changes in brainstem, medulla, atrophy of the cerebella peduncles Involvement of caudate nucleus and putamen. Dilatation of the anterior horns of the lateral ventricles
5. Hereditary spastic paraplegias
Mild changes or normal picture of the white matter in centrum semiovale. Thinning of the total length of the spinal cord without signal changes
6. Amyotrophic lateral sclerosis
Hyperintense MR signal on Т2-weighted and FLAIR images in corticospinal tracts on brain MRI
7. Wallerian degeneration
Asymmetrical hyperintense MR signal in the descending or ascending pathway involved
Refere n c e s Antonini A, Leenders K, Meier D et al (1993) T2 relaxation time in patients with Parkinson’s disease. Neurology 43:697–700 Bahn M, Kido D, Lin W, Pearlman A (1997) Brain magnetic resonance diffusion abnormalities in Creutzfeldt-Jakob disease. Arch Neurol 54:1411–1415 Barboriak D, Provenzale J, Boyko O (1994) MR diagnosis of Creutzfeldt-Jakob disease: significance of high signal intensity of the basal ganglia. AJR Am J Radiol 162:137–140 Braffman B, Grossman R, Goldberg H et al (1988) MR imaging of Parkinson’s disease with spin-echo and gradient-echo sequences. AJNR Am J Neuroradiol 9:1093–1099 Craham G, Petroff O, Blamire A et al (1993) Proton magnetic resonance spectroscopy in Creutzfeldt-Jakob disease. Neurology 43:2065–2068 Demaerel P, Baert A, Vanopdenbosch L et al (1997) Diffusionweighted magnetic resonance imaging in Creutzfeldt-Jakob disease. Lancet 349:847–848
de Priester J, Jansen G, de Kruijk J, Wilmink J (1999) New MRI findings in Creutzfeldt-Jakob disease: high signal in the globus pallidus on T1-weighted images. Neuroradiology 41:265–268 DiRocco A, Molinari S, Stollman A et al (1993) MRI abnormalities in Creutzfeldt-Jakob disease. Neuroradiology 35:584–585 Duguid J, De La Paz R, De Groot J (1986) Magnetic resonance imaging of the midbrain in Parkinson’s disease. Ann Neurol 20:744–747 Gertz H, Henkes H, Cervos-Navarro J (1988) Creutzfeldt-Jakob disease: correlation of MRI and neuropathologic findings. Neurology 38:1481–1482 Gibb W, Luthert P, Marsden C (1990) Clinical and pathological features of corticobasal degeneration. Adv Neurol 53:51–54 Gorell J, Ordidge R, Brown G et al (1995) Increased iron-related MRI contrast in the substantia nigra in Parkinson’s disease. Neurology 45:1138–1143
1092
Chapter 14
Hauser R, Olanow C (1994) Magnetic resonance imaging of neurodegenerative diseases. J Neuroimaging 4:146–158
Riley D, Lang A, Lewis M et al (1990) Cortical-basal ganglionic degeneration. Neurology 40:1203–1212
Huber S, Chakeres D, Paulson G, Khanna R (1990) Magnetic resonance imaging in Parkinson’s disease. Arch Neurol 47:735–737
Savoiardo M, Strada L, Girotti F et al (1989) MR imaging in progressive supranuclear palsy and Shy-Drager syndrome. J Comput Assist Tomogr 13:555–560
Illarioshkin S (2003) [Conformation diseases of a brain]. Yanus-K, Moscow, p 248 (in Russian) Jahno N, Shtulman D (2001) [Diseases of nervous system: the management for doctors in two volumes.] Medicine, Moscow, p 480 (in Russian) Kamo H, McGeer P, Harrop R et al (1987) Positron emission tomography and histopathology in Pick’s disease. Neurology 37:439–445 Kretzschmar H, Ironside J, DeArmond S, Tateishi J (1996) Diagnostic criteria for sporadic Creutzfeldt-Jakob disease. Arch Neurol 53:913–920 Kruger H, Meesmann C, Rohrbach E et al (1990) Panencephalopathic type of Creutzfeldt-Jakob disease with primary extensive involvement of white matter. Eur Neurol 30:115–119 Kuhn M, Mikulis D, Ayoub D et al (1989) Wallerian degeneration after cerebral infarction: evaluation with sequential MR imaging. Radiology 172:179–182 Mazumdar A, Mukherjee P, Miller J et al (2003) Diffusion-weighted imaging of acute corticospinal tract injury preceding Wallerian degeneration in the maturing human brain. AJR Am J Neuroradiol 24:1057–1066 Neary D, Snowden J, Shields R et al (1987) Single photon emission tomography using 99mTc-HM-PAO in the investigation of dementia. J Neurol Neurosurg Psychiatr 50:1101–1109 Pennock J, Rutherford M, Cowan F, Bydder GM (1993) MRI: early onset of changes in Wallerian degeneration. Clin Radiol 47:311–314 Prusiner S (1987) Prions and neurodegenerative diseases. N Engl J Med 317:1571–1581 Rebeiz J, Kolodny E, Richardson E (1968) Corticodentatonigral degeneration with neuronal achromasia. Arch Neurol 18:20–33
Sawlani V, Gupta R, Singh M, Kohli A (1997) MRI demonstration of Wallerian degeneration in various intracranial lesions and its clinical implications. J Neurol Sci 146:103–108 Scott W et al (2002) Magnetic resonance imaging of the brain and spine, 3rd edn. Lippincott Williams & Wilkins, Philadelphia, p 1240 Skvortsova V, Levitsky G. (2007) [Amyotrophic lateral sclerosis.] In: Gusev E, Konovalov A, Geht A (eds) [Clinical recommendations: neurology and neurosurgery (Russian Society of Neurology).] Geotar Media, Moscow, p 39 (in Russian) Steele J, Richardson J, Olszewski J (1964) Progressive supranuclear palsy. Arch Neurol 10:333–359 Stuss D (1993) Assessment of neuropsychological dysfunction in frontal lobe degeneration. Dementia 4:220–225 Valk J, Barkhof F, Scheltens P (2003) Magnetic resonance in dementia. Springer, Berlin Heidelberg New York, pp 353 Vrancken A, Frijns C, Ramos L (2000) FLAIR MRI in sporadic Creutzfeldt-Jakob disease. Neurology 55:147–148 Wakabayashi K, Takahashi H, Oyanagi K, Ikuta F (1993) Incidental occurrence of Lewy bodies in the brains of elderly patients: the relevance to aging and Parkinson’s disease. No To Shinkei 45:1033–1038 Will R, Zeidler M, Stewart G et al (2000) Diagnosis of new variant Creutzfeldt-Jakob disease. Ann Neurol 47:575–582 Yakhno N, Shtulman D (2001) [Diseases of the nervous system.] Medicine, Moscow, p 480 (in Russian) Zuiev V, Zavalishin I, Roykhel V (1999) [Prion disorders of the human and animals.] Medicine, Moscow, p 192 (in Russian)
Chapter 15
Spine and Spinal Cord Disorders
15.1 15.2 15.3 15.4 15.5 15.6 15.7 15.8 15.9
Imaging Modality and Normal MRI Anatomy . . . . . . . . . . . . . Specific Features of the Spine and Spinal Cord in Children Congenital Spinal Pathology .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spinal Cord Tumours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Intramedullary Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Extramedullary–Intradural Tumours . . . . . . . . . . . . . . . . . . . . . Extradural Tumours .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Traumatic Spine and Spinal Cord Injuries .. . . . . . . . . . . . . . . . Degenerative Spinal Diseases .. . . . . . . . . . . . . . . . . . . . . . . . . . . .
.
1093 1096 1097 1122 1124 1150 1184 1261 1267
15.1 Imaging Modality and Normal MRI Anatomy Incidence of spinal cord tumours compared with organic lesions of the CNS varies from 1.98 to 3%, and compared with brain tumour cases is less than 15% of CNS lesions (Nikolsky 1947; Razdolsky 1958; Manelfe 1992). For many years, myelography (first applied in 1923) has been considered one of the principal imaging modalities for diagnosis of spinal pathology. In the early 1980s, its place was overtaken by CT and its modification, CT myelography with soluble contrast medium. This permitted, on the one hand, reducing the rate of complications and, on the other hand, significantly improving the quality of primary diagnosis of spinal cord lesions. It is mainly used for extramedullary tumours (Aubin 1979; Post 1980; Haughton 1982). The introduction of a new imaging modality—MRI—in neurosurgical practice was a new step towards improved diagnosis and treatment of patients with spinal cord lesions. MRI scanners enable whole-spine and spinal cord imaging without CE or ionising radiation; it is also useful in diagnosing tumour size and localisation (especially intramedullary), and differentiating solid and cystic tumour components. All these factors contribute to its widespread use. And as a reflection of this process, an appearance of a number of monographs devoted to use of this modality in neurosurgery and neurology surfaced (Brant-Zawadzki 1987; Valk 1987; Haughton 1988; Stark and Bradley 1988; Manelfe 1989).
15
At present, MRI (especially high-field MRI) is considered the guiding method in diagnosing the majority of spine and spinal cord lesions; it has practically replaced myelography (usually used for preoperative examinations) as well as markedly restricted usage of such a method as spiral CT (SCT myelography). Our imaging was performed with 1- to 1.5-T units with superconductive magnets. Spine and spinal cord MRI was conducted using two surface radiofrequency coils of various configurations. One of them is usually used for studying the cervical or craniovertebral spine while the other (its flat form), for any segment of the spinal column. Its application in thoracic or lumbar spine imaging resulted in outcomes more favourable. Taking into account the fact that a simple surface coil has a limited FOV, it should, as a minimum, be moved twice along the spinal axis to demonstrate the entire spinal column length. Nowadays, the above-mentioned types of radiofrequency coils are not produced. The so-called phased array coil has replaced them. Its unique feature is that it is constructed of small-size radiofrequency coils (six and more). It has FOV of 48–50 cm. In most cases, it is enough for studying the entire spine and spinal cord; no additional patient repositioning is required during an examination. The scanning zone merely shifts. The programme for examining spine and spinal cord depends on the tasks set and patient’s ability to maintain stable position for a rather long period. Most often, it comprises strict sagittal T1- and T2-weighted sequences. Pulse sequence SE with TR ranging 500 from 650 ms and TE of about 15 ms ensures T1-weighted sequence attainment (for the indicated MR units). The peculiar feature about these images is tissues with the shortest T1 relaxation time (spinal cord, lipid tissues, etc.) are known to produce the brightest MR signal (i.e. hyperintense signal), while tissues with the longest T1 relaxation time, the darkest MR signal (CSF, spinal ligament, cortical part of the vertebral body; i.e. hypointense MR signal). This regimen is helpful for providing adequate information about anatomic structures of the spine and spinal cord (Fig. 15.1) To obtain T2 images, Fast SE is used with TR = 4,000– 4,500 ms and TE = 80–100 ms (1.5-T MR units). CSF, nucleus pulposus of intervertebral disks, and lipid tissues have the
1094
Chapter 15
Fig. 15.1a–i Normal anatomy of cervical
spine and spinal cord. T2- and T1-weighted images in sagittal plane (a,b), T1-weighted images in axial plane (c). 1 Spinal cord, 2 subarachnoid space, 3 intervertebral disk, 4 C2 vertebra, 5 white matter, 6 grey matter. ADC map in sagittal plane (d) demonstrates relationship between spinal cord (blue) and CSF (red). Fractional anisotropy map in axial plane (e) and structural map (f 2D tractography). Sagittal reformation of CT data in standard (g) and bone (h) window as well as 3D reconstruction show cervical spine and intervertebral foraminae
Spine and Spinal Cord Disorders
brightest (most intense) MR signal. Spinal cord, vertebral body bone marrow, and spinal ligaments produce a hypointense signal on T2-weighted sequences, thus making these images look like myelograms in the presence of a hyperintense signal from CSF. For obtaining axial cervical spine views, T2* images are usually used to ensure high contrast between CSF spaces, spinal cord, and spinal structures, provided no pulsation artefacts from the moving CSF, so characteristic for T2 MRI, are present. For thoracic or lumbosacral spine, we prefer using fast SE to obtain axial views. Change of TR, TE parameters, and flip angle in gradient echo pulse sequence (except T2 regimen) is helpful in obtaining T1-weighted images. Vertebral body has a dark MR signal on T1-weighted images, while the spinal cord has a bright MR signal. This regimen is indicated for assessing localisation and invasion of the metastatic spinal lesions (most metastatic lesions have an increased MR signal intensity in this regimen). Nowadays T1-weighted imaging remains the basic imaging modality for postcontrast examination of patients with intravenous CE. Additional information about contrast media diffusion and character, for instance in case of a large-size tumour outgrowing the spinal canal, is possible to obtain on T1 images, using the fat-sat technique. It helps to obtain images when a hyperintense signal from lipid tissues cannot be identified (fatty tissues of vertebral body bone marrow, interfascial and subcutaneous fat) and regions with a minimal contrast accumulation demonstrate a brighter signal compared with T1 MRI.
1095
Nowadays, FLAIR sequence with T2 or T1-weighting are more widely used in spinal cord imaging. The normal spinal cord, which has a hyperintense signal on T1-weighted images, is strictly contoured in the presence of a hypointense signal from the surrounding CSF and spinal ligaments. The spinal cord itself as well as its contours can be clearly visualised; it is easy to assess its location in the spinal canal, usually resembling physiological curvature of the spine. T1-weighted images have proved to be informative for assessing spinal cord extension in normal conditions and pathology. Here, sagittal and axial views are most useful. High-resolution MRI measurement of spinal cord dimensions obtained by De LaPaz et al. (1985) practically coincide with the results obtained from using CT myelography (Thijssen 1979). Surface coils with a high signal-to-noise ratio and increased resolution image degree provide high-quality axial views of the spinal cord and easy differentiation of the white and grey matter. Vertebral body bone marrow (lipid tissues), nucleus pulposus of the intervertebral disks, and upper vertebral fibrous rings have a moderately-intense signal on T1-weighted images ,very close by its intensity to that of the spinal cord. Taking into account the fact that CSF circulation in SAS is well visualised on T2-weighted images with strictly outlined contours of the latter, the role of T2-weighted images (or T2*) becomes absolutely indisputable in demonstrating pathological processes causing SAS narrowing in the spinal cord. The intervertebral disk’s central part has a high content of hydrogen protons and is characterised by a hyperintense signal on
Fig. 15.2a,b Normal anatomy of lumbar
spine of child (2 years old). MRI in T2 (a) and T1 (b) sequences. 1 Vertebral body, 2 pulpous nucleus, 3 fibrous rim, 4 spinal canal, 5 cauda equina
1096
T2-weighted images compared with spinal cord tissue. It is more characteristic for children and adolescents (Fig. 15.2). With age and in cases of degenerative changes in the disk tissues, signal intensity is gradually decreased, thus reflecting the dehydration degree of intervertebral disk tissue (Modic 1984; Modic and Masaryk 1988). Sometimes quality of spinal T2-weighted images deteriorates due to artefacts caused by CSF pulsation in SAS of the spinal cord, in respiration, or in systoles. In that case, in order to improve the quality of tomograms, it is recommended to use saturation impulses for the cardiac region as well as special programmes for cardiorespiratory synchronisation. However, it should be noted that scanning time for synchronisation is usually increased. Gradient echo technique obtains T2*-weighted images (Fig. 15.3) and is considered less sensitive towards the above-mentioned artefacts. Spine and spinal cord MRI provides no bone markers that can help a radiologist to evaluate target points. The most reliable marker for spinal MRI is location of the C2 vertebra with the odontoid process; a less remarkable marker is the L5 vertebrae level (Fig. 15.4). In our opinion, to determine vertebra location in the thoracic spine it is reasonable to either adequately place the surface coil at investigation (for visualisation of the above-indicated markers) or preliminarily perform scanning of the whole spine with a maximum VOF of 48–50 cm. One can also be guided by a special marker filled with paramagnetic content.
15.2 Specific Features of the Spine and Spinal Cord in Children Anatomic and physiological features of the spine and spinal cord have been thoroughly described in literature. In this chapter, we briefly touch upon the main aspects of spine and spinal cord embryology.
Chapter 15
Formation of spine cartilage starts at the second intrauterine month, i.e. simultaneously with vertebral body bone nucleus formation. Their fusion occurs by the age of 1 year. Secondary ossification nuclei of vertebral bodies and articular processes appear by the age of 14–16 years. A 1-year-old child’s vertebrae are wider, lower, and deeper compared with that of an adult. The length of child’s spine accounts 50% of body length, while in adults it is 45%. Physiological curvature of a newborn’s spine, caused by its vertical position, is formed and markedly expressed by ages 6–7 years. With a child’s growth, physiological curvature extends and its vertex shifts downward. Growth of spine takes more time than growth of intervertebral disks. The spine remains flexible and elastic for a long time and is completely formed by the age of 20–25 years. Spinal cord develops from the caudal portion of the medullar tube; in a 2-month embryo, it occupies the whole spinal canal. An embryo’s spine grows faster than the spinal cord does; by age of 2 years, the conus medullaris is localised at the L3 vertebra’s low edge, gradually ascending and occupying the position similar to adult’s conus, i.e. the L1 level. Spinal nerve roots are lengthened and form cauda equina. If conus medullaris position in a 2 year-old child is lower the L2–L3 level, then it is regarded as pathological and one of the “tethering” syndrome elements. Cervical and lumbar spinal cord thickening is usually observed by the second month of intrauterine development and is well defined in a newborn. During first years of life, this process continues due to growth of grey matter cells, processes, and neuroglia. Microscopic spinal cord structure of a newborn is similar to that of an adult; however, the number of motor cells is half that in adults. Anterior horn size in the early age is larger than the posterior horn size. The key moment in assessing the child’s spine is knowledge of localisation of vertebral body ossification centres; it helps to prevent diagnostic errors, as in cases of normal anatomic changes that are sometimes confused with spinal injury; for
Fig. 15.3a,b Normal anatomy of cervical
spine and spinal cord. Sagittal (a) and axial (b) projections in T2* sequence (gradient echo). 1 Spinal cord, 2 subarachnoid space, 3 intervertebral disk, 4 white matter, 5 grey matter
Spine and Spinal Cord Disorders
1097
1 year of age. The C2 vertebra has five ossification centres: one is located in the vertebral body, two others in vertebral arches (one per each arch), and the remaining two in the odontoid process. Synchondrosis, located between the dens and C2 vertebral body, may cause some sort of confusion, as it usually simulates spine fracture (Fig. 15.5). Fusion of the dens and C2 vertebral body is completed by age 7 years, but the region of synchondrosis may be visible for several more years. By the age of 6 years, the so-called terminal ossification centre appears (os terminale), which is fused with the main dens portion by the age of 10–12 years. The C3–L5 vertebral bodies have three primary ossification centres, one is localised in the vertebral body, and the other two in posterior vertebral arches (each per arch). Fusion of the vertebral arch and body is completed by age 3–6 years. Five additional ossification centres are formed in the adolescence period: by 1 year, in the apexes of transverse and spinous processes and anterior and inferior parts of vertebral bodies. Fusion of additional centres occurs by age 25 years. The important anatomic factor of the child’s developing spine is a comparatively horizontal orientation of intervertebral facets. It is clearly seen in the atlanto-occipital facet and cervical facets. Facet angle of the upper fourth cervical vertebra in newborns is <30° ; by the age of 10 its size increases to 60–70°. In the inferior cervical level, this angle ranges from 55° (in newborns) to 70°. Because of the horizontal facet angle direction, a child’s spine is prone to flexion fractures. A child’s spine acquires mechanical features, so typical for adults, approximately by the age of 11 years. As well, spinal ligaments and muscles in children are weak, unlike in teenagers or adults. It is evident for cases of pseudosubluxation at the C2–C3 level (sometimes C3–C4) observed in 10-year-old children. Children often reveal a large interval between the anterior C1 arch and C2 dens, which is normal, i.e. 3–4 mm (up to 5 mm), while in adults this interval does not exceed 2.5 mm.
15.3 Congenital Spinal Pathology
Fig. 15.4 MRI of whole spine in T2 sequence with the use of large FOV. There are well-defined C2 and L5 vertebral bodies
instance, spine fracture is often confused for synchondrosis. The C1 vertebra has three primary centres of ossification: the first centre is localised in the anterior arch, while each of the other two is located in half of the posterior arch. C1 anterior arch ossification is marked only in 20% of the newborns and is usually not visualised by radiography in children less than
Spinal dysraphism syndrome involves a large group of congenital spine and spinal cord anomalies. Despite the fact that they all are heterogeneous, they are accompanied by incomplete consolidation of medially located mesenchymal, osseous, and nervous structures. The most simple of them is spina bifida, characterised by inability of bone structures like vertebral arches or interspinous ligaments forming posterior wall of the vertebral canal to consolidate completely. Diagnosis of this pathology is simple (X-ray examination) and does not require complex imaging modalities like CT or MRI. Spina bifida aperta (spina bifida cystica) is described as pathological posterior protrusion of vertebral canal components via a vertebral body defect. Protrusion of dura and pia mater through a posterior vertebral body defect is called pure meningocele. In myelocele, spinal cord elements protrude into the defect zone also. The entire vertebral canal elements protrusion via a vertebral body defect and formation of a cystic lesion-covered by skin outside is called myelomeningocele.
1098
Fig. 15.5a–e CT images on C1 (a) and C2 (b) levels (a 1-month-old
child). Case 1. There is partial ossification of anterior and posterior half of arches, on C2 level, ossification of vertebral body and lateral arches is observed. Case 2. CT on C1 and C2 levels (a 3-year-old child). CT images in axial (c,d) and sagittal (e) planes demonstrate
The term spina bifida occulta is used to describe anomalies that do not invade dermis or epidermis. They include subcutaneous lipomas and simple meningocele; diastematomyelia and thickening of cauda equina nerve roots, spinal lipomas and myelocystocele; terminal thread thickening syndrome (spinal cord tethering syndrome or tethering syndrome); and dorsal dermal sinus. Intradural lipomas are observed usually in caudal parts of the vertebral canal and connected with the epidural space. The term lipomyelomeningocele is used to describe a large-size caudal lipoma involving vertebral canal structures (spinal cord, dura, and arachnoid). MRI has proved to be highly effective for assessing spinal dysraphism. In noninvasive diagnosis of congenital spinal anomalies in paediatric age group, the first place belongs to MRI. It is justified be-
Chapter 15
practically completed ossification arches of the vertebra and two points of ossification in dens. There are the synchondrosis between body and lateral arches C2 as well as between body and dens of C2 (arrow)
cause MRI enables simultaneous whole-spinal cord and SAS imaging.
15.3.1 Dorsal Dermal Sinus Dorsal dermal sinus is identified as medially localised epithelium-lined dural canal, spreading from the skin surface towards the vertebral canal (partial division of cutaneous and neural ectoderma). This pathology can be observed in any spinal segment, but most commonly, it is marked in the lumbosacral region. Sinus depth varies: it may stop at the fascia level, in muscles, or spread to the vertebral canal or spinal cord (or cauda equina roots). In two thirds of observations,
Spine and Spinal Cord Disorders
it penetrates into the vertebral canal lumen. In half of observations dermoid, epidermoid, or lipoma may serve as sinus endpoint. Often one can observe combinations of sinus and skin stigmas, like focal pilosis, nevus, capillary angioma, focal hyperpigmentation, and others. The dermal sinus may cause recurrence of bacterial or virus meningitis. Ultrasound, CT, and MRI are equally useful for an accurate demonstration of dermal sinus extension in the back spine soft tissue. MRI identifies the dermal sinus as a hypointense MR signal line (more apparent on T1-weighted images), spreading from the skin towards the spine, alongside with a hyperintense MR signal from subcutaneous lipid tissues (Figs. 15.6, 15.7). MRI poorly differentiates the dermal sinus in deep-seated structures (muscles, ligaments, dura mater)
1099
due to similar signal characteristics of the above-mentioned formations. CT myelography is preferred for evaluating the intravertebral course of the dermal sinus. MRI is useful in diagnosing of the spinal cord shift (or nerve roots) towards the defected vertebral canal posterior wall, as well as lesions like dermoids, epidermoids, and lipomas in the sinus exit zone.
15.3.2 Lipomas Spinal lipomas are identified as intra-extravertebral mass lesions that consist mainly from the lipid tissues; however, in some cases they may have mesenchymal and neural elements. They form a group of partially or completely encapsulated tu-
Fig. 15.6a–c Dorsal dermal sinus on T3–T4 level (a 2-year-old child). Series of sagittal MRI in T2 (a) and T1 (b) sequences as well in axial plane (c) demonstrate dermal sinus coursing through subcuta-
neous fat and into the subarachnoid space. There are bone defects in the posterior wall of the spinal canal and deformation of posterior spinal cord surface on the level of dermal sinus
Fig. 15.7a–c Dorsal dermal sinus on the T4–T5 level (1-year-old child). Sagittal MRI in T1 (a) and T2 (b) sequences show the sinus tract extending from skin through spina bifida into the subarachnoid
space. Series of axial T1 imaging (c) show the defect of posterior spinal canal wall as a hypointense linear zone on background of high signal intensity of epidural fat
1100
mours, closely connected with the spinal cord and arachnoid. According to their localisation, they are subdivided into three main groups: intradural (extramedullary), lipomyelocele/li pomyelomeningocele (lipomyeloschisis) and lipomas of the filum terminale (Barkovich 2002). Combinations of lipomas with bone changes, in particular with spina bifida, are common. Intradural lipomas make up a group of tumours localised in the vertebral canal. They account for 1% of all primary intraspinal tumours. These tumours have a typical extramedullary or subpial localisation; they occupy predominantly the dorsal spinal cord portion, to which they are often adhered. The majority of lipomas are localised in the cervical and thoracic spine. They are identified as hypodense mass lesions on CT (–60 to 80 HU). MRI also reveals specific manifestations of these tumours: a hyperintense MR signal on T1 and a hypo-isointense signal on T2-weighted imaging (Figs. 15.8– 15.10).
15.3.3 Lipomyelocele/Lipomyelomeningocele (Lipomyeloschisis) Lipomyelocele is one of the forms of spinal dysraphism involving the skin surface: it spreads from the subcutaneous lipid tissues into the vertebral canal via the dorsal vertebral body defect, simultaneously interacting with the spinal cord (dislocation, tethering). There is an interaction between lipoma and the spinal cord within the spinal canal, and no enlargement of ventral SAS is marked. A combination of lipomas with spinal cystic protrusion (subarachnoid space, arachnoid and dura, and spinal cord) is called lipomyelomeningocele. It is
Chapter 15
observed in 20% of patients with mass lesions of lumbosacral region accompanied by skin change (stigmas) and in 20–50% of patients with spina bifida occulta. It is most frequently revealed in girls younger than 6 months of age. Spondylography is excellent in demonstrating bone changes (spina bifida). CT helps to identify lipid tissues of subcutaneous lipoma, which penetrate via a defect zone into the vertebral canal. Thin-slice spiral CT scanning with further reconstructions is more useful for visualisation of the spinal cord and thickened nerve roots than for lipomas (Figs. 15.11, 15.12). T1 sequences demonstrate a hyperintense MR signal from lipomas, which is practically identical in terms of signal characteristics to of the subcutaneous lipid tissues. Lipid tissues protrude into the spinal lumen via a vertebral defect. Lipoma may occupy (or displace) terminal segments of the spinal cord, roots of cauda equina, or filum terminale (Figs. 15.13–15.16). Partial splitting of the posterior surface of the spinal cord (partial myeloschisis) can be combined with lipid tissues. When dealing with cases of lipomyelomeningocele, one can mark a combination of lipoma with the spinal cord outside the spinal canal (depending on the size of the vertebral body defect and cyst volume) (Fig. 15.17). Hydromyelia can be observed in the upper spinal segments. Lipoma of filum terminale follows a similar anatomic structure. It is situated in the central spinal canal portion and can be localised or spread from the conus to caudal parts of vertebral canal along the filum terminale. Being a lipid structure, it has a hypodense features on background of SAS on CT and a typical hyperintense signal on T1 MRI (Fig. 15.18). Saturation methods make MR diagnosis more specific.
Fig. 15.8a–c Intradural lipoma of cervical spine. MRI in T1 (a) and T2 (b) sequences reveals a small hyperintense (in T2) lesion located on
dorsal surface of spinal cord. The lipoma has wide attachment with lateral posterior surface of the spinal cord (c T1 axial image)
Spine and Spinal Cord Disorders
1101
Fig. 15.9a–h Intradural lipoma of thoracic spine. CT in axial (a)
and sagittal (b,c) planes shows low attenuation mass in the dorsal aspect of the spinal canal, small calcifications on the spinal cord surface; lipoma border are visualised. MRI in T2 (d), T1 (e) and T1 with fat sat (f) demonstrate the extended mass lesion with hyperintense signal in standard sequences. Fat-sat technique clearly depicts the decrease of signal intensity from fat tissue. On DWI ADC map (g), lipoma has low diffusion parameters. Bright colour from CSF outlines the lipoma contours
1102
Fig. 15.10a–f Intradural lipoma of cervical and upper thoracic spine. Series MRI in T2 (a) and T1 (b) sequences
demonstrates extended mass lesion with hyperintense signal. With the fat-sat technique, (c T1, d T2) the lipoma shows the typical decrease of signal intensity. Coronal and axial (e,f) T1 images obtain additional information about relationship between lipoma and spinal canal structures. g–i see next page
Chapter 15
Spine and Spinal Cord Disorders
1103
Fig. 15.10g–l (continued) Sagittal (g,h) and coronal (i,j) CT reformations as well as images demonstrate attenuation of lesion in dorsal aspect
of the spinal canal
1104
Chapter 15
Fig. 15.11a–c Schematic illustrating of variants lipomyeloschisis. a Intradural lipoma, b lipomyelocele, с lipomyelomeningocele
Fig. 15.12a–c Lipomyelocele (a 13-year-old child). Sagittal CT reformation (a) and axial images (b,c) reveal extended spina bifida at the
S1–S3 levels. Lipoma that has connection with subcutaneous fat is situated in zone of bone defect (hypodense mass). Tethered spinal cord is attached to the lipoma (arrows)
Fig. 15.13a,b Lipomyelocele (a 6-monthold child). Series sagittal MR T2 (a) and T1 (b) imaging demonstrates the extended lipoma in lumbar spinal canal. Lipoma has a connection with subcutaneous fat. Tethered spinal cord is attached to the lipoma and displaces ahead
Spine and Spinal Cord Disorders
1105
Fig. 15.14a–d Lipomyelocele (a 10-month-old child). Sagittal T2 (a,b), T1 (c,d) images
show the spinal cord tethered by a large lipoma, which has connection with subcutaneous fat through the spina bifida. There is chemical shift artefact between lipoma and spinal cord. There is no enlargement of ventral subarachnoid space. A small hydromyelic cyst in spinal cord is visualised
Fig. 15.15a–c Lipomyelocele (an 8-year-old child). Sagittal (a,b) and axial (c) MRI demonstrate intradural lipoma at the L4–S2 level, which
is connected with subcutaneous fat through spina bifida and attaches to ventrally located spinal cord
1106
Chapter 15
Fig. 15.16a–c Lipomyelocele (a 3-month-old child). Sagittal (a,b) and axial (c) MRI demonstrate intradural lipoma at the L2–S1 level, which is connected with subcutaneous fat through spina bifida and widely attaches to ventrally located tethered spinal cord
Fig. 15.17a,b Lipomyelomeningocele (5-year-old child). Sagittal T2-weighted imaging (a) and T1-weighted imaging (b) show the extension of CSF ventral to the neural placode, which is attached to the dorsal large lipoma. There are signs of tethered syndrome
Spine and Spinal Cord Disorders
1107
Fig. 15.18a–c Lipoma of filum terminale. Sagittal MRI in T1 (a) and T2 (b) sequences as well as axial T1-weighted images (c) shows a thick-
ened filum terminale demonstrating hyperintense signal indicate of fat. The conus medullaris is a normal level
15.3.4 Meningocele Meningocele is identified as an extension of dura mater and subarachnoid through the vertebral defect (Fig. 15.19). There are termed simple posterior, lateral, and anterior (sacral) meningocele. Simple meningocele occurs rarely (approximately 1 in 10,000 newborns, Fig. 15.20). In most congenital cases, spinal cord roots and filum terminale protrude into the cystic cavity; in that case, we deal with meningoradiculocele (Fig. 15.21), or even into the inferiorly located and tethered spinal cord— here we deal with meningomyelocele. Vertebral bone defect at the level of meningocele may be revealed in or on a few vertebral segments. It usually occurs in lumbosacral or sacral
Fig. 15.19 Schema. Meningocele
segments. If the vertebral defect has a superior localisation, then the spinal cord may also protrude into the cystic cavity (Fig. 15.22). MRI is considered a method of choice for primary diagnosis of meningocele, thus providing a better visualisation of all elements participating in the cyst protrusion process (CSF, presence or absence of roots and filum terminale, position of the spinal cord conus and others) (Figs. 15.23–15.25) in comparison with CT. In some cases, MR myelography (based on artefacts, so characteristic of the accelerated blood flow in cystic gates) may be of benefit suggesting relationships that might exist between meningocele and SAS of the spinal cord, (Fig. 15.26). Anterior sacral meningocele is defined as protrusions of dura matter through a sacral vertebral body defect into the pelvic region. This pathology is revealed extremely rarely. Spondylography is useful in demonstrating enlargement of the vertebral canal and sacral vertebral body defects. Sagittal MRI demonstrates the cystic lesion filled with CSF and closely related to the vertebral canal. Large-size meningocele has a typical decrease of MR signal on T2-weighted imaging, caused by CSF turbulence movement in the cystic cavity (Fig. 15.27). In rare cases, cystic hyperpulsation can be so high that MRI reveals a pulsating artefact in a phase-coding direction, typically observed in patients with arterial aneurysms (Fig. 15.28). The presence of trabecular into meningocele cavity restricts of CSF pulsation; MR signal is usually hyperintense on T2weighted images (Fig. 15.29). MRI is good at revealing single or multiple cystic SAS enlargements along spinal cord roots in adults with no signs of spinal injury. Most commonly cystic enlargement is marked in the sacral spine at the caudal level of dural sac (usually
1108
Chapter 15 Fig. 15.20 Simple dorsal meningocele at the level C7–T2 (a 1-year-old child). Sagittal T1-weighted images (exam was per formed on 0.04-T MR system) detects wide bone defect in posterior wall of spinal canal. There is no displacement of the spinal cord. Subarachnoid space is protruded through spina bifida defect up to subcutaneous fat
Fig. 15.21a,b Meningoradiculocele at the S1–S2 level (a 10-year-old child). Series T2-weighted imaging (a) and T1-weighted imaging
(b) reveal the protrusion of subarachnoid space, filum terminale, and spinal roots into the spina bifida defect. There are hydromyelitic cyst in conus and signs of tethered spinal cord
Spine and Spinal Cord Disorders
Fig. 15.22a–c Meningomyeloradiculocele
at the L1–L4 level (a 2-month-old child). T1-weighted imaging (a) and T1-weighted imaging (b) demonstrate the traumatic (during delivery) damage
1109
of T12–L1 vertebrae with antelisthesis at T11 and the protrusion of subarachnoid space, conus of spinal cord, and spinal roots into the wide spina bifida defect
Fig. 15.23a–c Meningomyeloradiculocele of the lumbar spine (1-month-old child). T2-weighted imaging (a) and T1-weighted imaging (b)
show the protrusion of subarachnoid space, partially tethered spinal cord, and spinal roots into the wide spina bifida defect with giant meningocele sac formation
1110
Chapter 15
Fig. 15.24a–c Meningomyeloradiculocele of the lumbar spine (a
1-month-old child). Axial CT demonstrates the spina bifida defect and large meningocele (a). T2-weighted imaging (b) and T1-weighted
imaging (c) in sagittal plane clearly show the protrusion of subarachnoid space, partially tethered spinal cord, and spinal roots into the wide spina bifida defect with meningocele sac formation
Fig. 15.25a–d Meningoradiculocele of the upper thoracic spine (a 1-month-old child). Sagittal MR images in myelography mode (a) and T1 (b) as well as CT reformation (c) and 3D reconstruction (d) show the protrusion of subarachnoid space with arachnoids and spinal roots into the spina bifida at the T1–T2 level. Cystic changes within spinal cord, hydrocephalus of ventricular system, and Chiari I malformation are found
Spine and Spinal Cord Disorders
Fig. 15.26a–f Meningoradiculocele at the S1–S3 level (a 2-monthold child). Sagittal CT reformation (a), axial CT (b,c) demonstrate wide bone defect of posterior spinal canal wall and thickened spinal
1111
roots, which are coursing into meningocele sac. MR myelography images in sagittal (d) and axial planes (e,f) identify the cystic lesion in lumbar region with spinal roots that pass along meningocele walls
1112
Chapter 15 Fig. 15.27a,b Anterior sacral meningocele. Sagittal MR images in T2 (a) and T1 (b) modes reveal large cystic mass into pelvic area. There is hyperpulsation artefact on MRI, especially in T2 regimen. The small bone defect (meningocele gate) with flow void effect is well visualised on T1-weighted imaging
Fig. 15.28a–f Anterior–lateral sacral meningocele. Series coronal
and axial MR images in T2 (a,b) and T1 (c–f) modes reveals giant cystic mass within retroperitoneal space into pelvic area and laterally from low lumbar vertebrae. There is hyperpulsation artefact on MRI,
especially in T1 regimen, which is disturbed the clear visualisation of meningocele walls and its relationship with SAS of spinal canal. A cystic lesion displaces the psoas muscle laterally
Spine and Spinal Cord Disorders
1113
Fig. 15.29a–c Large anterior sacral meningocele. Sagittal MR T2-weighted imaging (a,b) and T1-weighted imaging (c) show large cystic mass into pelvic area with multilobular structure. There is no hyperpulsation artefact on MRI
S1-S3 vertebrae). In medical literature, this process has different interpretations: some authors call it meningocele of neural roots, others, perineural cysts. For us, the second term seems to be more correct because it reflects the origin of this process: there is no dura matter along the walls above-mentioned cysts. The neural root either is revealed in the walls of these cysts or passes through them. It usually has no clinical signs, and if being revealed by MRI, it is considered a diagnostic achievement. Large perineural cysts can also manifest by chronic pain syndrome in the sacral spine, especially in patient’s vertical and sitting positions. MRI is effective in accurate identification of a large-size cystic formation with identical signal characteristics for all imaging modalities, including myelographic visualisation of CSF in the spinal canal. Visualisation of neural roots in the cyst can be obtained only on thin-slice T2 images or an MR myelography program with CSF-motionless regimen. Single cavities can be revealed, but most commonly multiple cystic lesions are visualised. In the thoracic spine, meningocele has lateral paravertebral localisation; in the sacral spine, it is located in the sacrum re-
gion along the spinal roots canals (Figs. 15.30–15.33). Despite the fact that high-resolution MRI is capable of visualising the CSF signal in SAS of the spinal cord and in the meningocele region, sometimes it is very difficult to reveal a relationship existing between these regions or differentiate one region from another. Spiral CTMG is excellent method in solving this problem (Figs. 15.34, 15.35).
15.3.5 Diastematomyelia Diastematomyelia is described as a form of spina bifida occulta manifested by partial or complete division of one or more spinal cord segments or terminal thread. It results in symmetrical or asymmetrical splitting in two of the spinal cord (hemicords). Each half of the spinal cords has a central canal, one ventral, and dorsal roots entering intervertebral canals at the appropriate. There is also the term diplomyelia, which is complete splitting of the spinal cord at one or several spine levels, with two ventral and two dorsal roots being present.
Fig. 15.30a–c Lateral thoracic meningocele. Axial and sagittal MR images in T2 (a) and T1 (b,c) modes reveal cystic lesion at the middle thoracic level with enlargement of intervertebral foramen. There is no obvious relationship between SAS of spinal canal and meningocele on MRI
1114
Chapter 15
Fig. 15.31a–c Sacral perineural cyst. Sagittal and axial MR images in T2 (a,c) and T1 (b) modes show cystic lesion at the lateral part of the
S1–S2 vertebrae with changing of their form. MR signal from cyst is identical with that of SAS of spinal canal
Fig. 15.32a–c Multiple sacral perineural cysts. Sagittal (a) and coronal (b,c) MR T2-weighted images show cystic lesions along spinal roots with enlargement of neural foramina. MR signal from cysts is identical with that of SAS of spinal canal
Spine and Spinal Cord Disorders
Fig. 15.33a–f Multiple sacral perineural cysts. MR T2 (a,b,e,f) and T1 (c,d) images show multiple cystic lesions extending laterally at the S2–S3 level. MR signal from the cyst is identical with that of SAS of spinal canal. The spinal root within the cystic cavity is well identified (arrow)
1115
1116
Fig. 15.34a–i Multiple lateral thoracic and lumbar meningoceles. Sagittal and coronal MR images in T2 (a–d) show multiple meningoceles extending laterally through expanded neural foramina into
Chapter 15
paravertebral space. Axial CT myelography (e–g) and coronal reformations (h,i) reveal penetration of contrast within of cavities of meningocele sacs
Spine and Spinal Cord Disorders
1117
Fig. 15.35a–h Multiple lateral thoracic
meningoceles. Sagittal (a,b) and coronal (c) MR images in T2 show multiple meningoceles extending laterally through expanded neural foramina. One of meningoceles reaches a giant size and compresses the lung apex. Axial CT myelography (d,e) and reformations (f–h) reveal penetration of contrast within of cavity of meningocele sacs
1118
Spinal cord splitting can be combined with osteofibrous and cartilaginous spur in the splitting zone. Diastematomyelia can be divided into two types (A and B), and depending on the size of splitting and formation, of totally (type B) or partially (type A) separated SAS. Standard spondylography often fails to reveal an osteofibrous spur in the zone of splitting. This imaging modality is useful for determining scoliosis accompanied by osteopathology. CT is much more sensitive in depicting the abovementioned spur; however, it rather poorly demonstrates the associated changes in the soft tissue. MRI is useful for assessing spinal cord doubling; however, it fails to identify the bone spur structure (Figs. 15.36–15.38).
15.3.6 Tight Filum Terminale Syndrome (Tethered Spinal Cord Syndrome, or Tethering Syndrome) Tethered spinal cord syndrome results from anomalous tethering of the spinal cord due to shortening and thickening of the filum terminale in the process of its formation. Filum terminale thickening, associated with spinal cord tethering, results in an atypically stretched spinal cord conus (no lumbar
Chapter 15
thickening) and its inferior location. Clinical signs of the disease manifest during a child’s fast somatic growth (between 4 and 8 years and in the adolescent period). In 50% of cases, skin stigmas, haemangiomas, focal pilosis, etc. are observed. MRI identifies thickening of the filum terminale (>2 mm, L5–S1 level) with probable small-size lipoma formation and atypically inferior location of the spinal cord conus (at or below L2) of a stretched form, which is poorly differentiated from the thickened filum terminale. Tethered spinal cord is usually adjacent to the posterior wall of the vertebral canal (no dislocation is possible when changing body position in scanner) and may end in the caudal lipoma (Figs. 15.39, 15.40). T1 MRI is the most informative imaging modality for making the correct diagnosis. It is reasonable to perform such an examination in the abdomen position in order to define mobility of the spinal cord.
15.3.7 Myelocele and Myelomeningocele Myelocele is defined as a form of spinal dysraphism when spina bifida with dorsal myeloschisis and nonenlarged SAS and neural structures are localised in the zone of primary
Fig. 15.36a–c Diastematomyelia with bone spur and tethered spinal cord. MR T2-weighted imaging (a) and T1-weighted imaging (b,c) demonstrate the division of spinal cord at L1–L2 on two portions. There is bone spur that extends from L1 posteriorly
Spine and Spinal Cord Disorders
Fig. 15.37a–i Diastematomyelia with bone spur and tethered spinal cord. MR T1-weighted imaging (a) and T2-weighted imaging (b–d) demonstrate the division of spinal cord at the L1–L2 on two portions. There are segmentation anomalies of T10–T12 and bone spur
1119
that extends from bodies of T11–T12 posteriorly. CT axial images (e,f), coronal and sagittal reformations (g,h) and 3D reconstruction (i view from behind) describe the bone pathology more precisely than MRI does
1120
Chapter 15
Fig. 15.38a–i Diastematomyelia with bone spur (a 5-year-old child). CT axial images (a–f) and 3D reconstructions (g–i) visualise bone spur
at the L5–S1 level and complex character of bone anomaly
Fig. 15.39 The tight filum terminale syndrome (tethered spinal cord) in a 5-year-old child. Sagittal T1-weighted imaging shows thin and elongated spinal cord extending all the way down into caudal lipoma
Spine and Spinal Cord Disorders
Fig. 15.40a–f Tight filum terminale syndrome (tethered spinal cord).
Sagittal T2-weighted imaging (a) and T1-weighted imaging (b,c) show thin and elongated spinal cord extending all the way down into caudal lipoma. There is intramedullary cavity (hydromyelia) within the
1121
spinal cord. Axial images in T2 (d,e) and T1 (f) regimens add information about cystic changes in tethered cord, enlarged spinal canal, and location of terminal lipoma
Fig. 15.41a,b Schema. a Myelocele, b myelomeningocele
1122
midline skin defect. The term myelomeningocele (Fig. 15.41) is used to describe enlarged ventrally located SAS and protrusion of spinal canal structures into the skin defect zone. Most commonly, this pathology is seen in the lumbosacral spine and in a prenatal period (for instance, on ultrasound examination). Certain sex dependence is marked (girls in 77%). As a rule, spondylography reveals a large-size bone defect of the posterior wall of the spinal canal. In 30–35% of cases, it is accompanied by a pathologic vertebral body defect (hemivertebrae, etc.). The risk of infectious complications is extremely high, which is why it is not recommended for this type of pathology to make a diagnosis before surgery. Ideal bone defect closure is achieved within the first 24 h after birth. Preoperative MRI reveals vertebral canal structures (spinal cord, roots, meninx, and SAS) within of zone of protrusion.
15.3.8 Kimmerle Anomaly This is described as a congenital anomaly of the atlas with a partial or complete bone bridge closure above the vertebral artery sulcus, with the latter transformed into the vertebral artery canal (foramen acute). There are two types of anomaly, unilateral and bilateral (Habirov et al. 2003). Clinical symptoms may absent in this type of anomaly, but they can manifest in head turning or flexion, syncope, or vertebral artery syndrome, i.e. vertebral artery narrowing in the bone canal. To define the effect of this anomaly on cerebral blood flow, it is reasonable to perform an ultrasound transcranial Doppler and examination of the neck vessels during head turning or flexion. Diagnosis of this anomaly is possible on lateral spondylograms. Spiral CT reconstructions provide information about pathological changes at the C1 level (Figs. 15.42, 15.43). MRA provides additional informa-
Chapter 15
tion about the vertebral artery state at this level. However, one should be overcautious when assessing the vertebral artery narrowing, taking into consideration the existing physiological curvature of the artery at the C1–C2 vertebral level (most commonly identified as a hypointense MR signal from the vertebral artery lumen) and existing artefacts.
15.4 Spinal Cord Tumours The first mention of spinal cord tumours dates back to the early nineteenth century when D. Phillips, and then N. Gerutti and C. d’Angers described for the first time clinical signs of spinal cord tumours. First papers about spinal cord tumours in children appeared in the end of the nineteenth century when S. Johnson described lipoma in a 10-year-old child, H. Chiari described an epidermoid cyst, and A.P. Alexandrov and L.S. Minor described extramedullary tumour. In 1935, R. Hamby reported 99 cases of spinal cord tumours in children, based on world reviews. Among the first researches works performed in this field in Russia, were the papers by G.P. Kornyanski (1959) in which he analyzed 53 cases of spinal cord tumours in children; the works by S.M. Shekhanov (1965), an analysis of 69 cases; and the monograph by A.P. Romadanov (1976) Spinal Cord Tumours in which 282 observations of spinal cord tumours were analyzed. By occurrence, spinal cord disorders are traditionally divided into congenital and acquired, by aetiology into inflammatory, degenerative, tumoral and traumatic, and by localisation to dura mater three main categories of tumours are outlined: intramedullary, extramedullary–intradural, and extradural (Fig. 15.44). Spinal cord tumours occur very seldom and make up 2% of all neoplastic processes. Compared with CNS tumours, their
Fig. 15.42a–c Kimmerle anomaly. Sagittal CT reformation (a,b) and 3D reconstruction (c) demonstrate one-sided, ring-like ossification around vertebral artery in place of its passage in vertebral artery’s fissure C1 vertebra (arrows)
Spine and Spinal Cord Disorders
1123
Fig. 15.43a–f Kimmerle anomaly. Multiple-view 3D CT reconstruction (a–f) demonstrate one-sided, ring-like ossification around vertebral
artery in place of its passage in vertebral artery’s fissure C1 vertebra (arrow)
Fig. 15.44a–d Schema. Location of spine and spinal cord tumours. a Spinal cord and meninges (1 spinal cord, 2 dura matter, 3 spinal roots), b intramedullary tumour, c intradural–extramedullary tumour, d extradural tumour
1124
frequency constitutes 1.4–5%. The spinal cord tumour to intracranial tumour ratio is 1:4–1:6 in children and 1:8–1:20 in adults. Children reveal primary spinal cord tumours extremely rarely. According to statistic data, spinal cord tumour is marked in 1:1,000,000 child’s population. Some authors report equal sex distribution of spinal cord tumours, others show female predominance. There is reported a great variety of classifications of spinal cord tumours: • Topographic: distribution by tumour localisation in the spine: cervical tumours, thoracic tumours and lumbar tumours • Histological: three basic types of tumours are defined: gliomas, neurinomas and meningiomas • Anatomic: tumour localisation to dura mater: extradural, subdural-extramedullary and intramedullary (one of the most popular classifications for today) More detailed anatomic classification of spinal cord tumours is represented below: 1. Spinal tumours arising from vertebrae and localised in vertebral bodies 2. Intraspinal localised inside the vertebral canal a. Extradural tumours: i. Primary tumours arising from vertebrae, periosteum, ligaments, dura mater (DM) external layer ii. Secondary tumours growing into the spinal canal from paravertebral tissues and metastases b. Subdural tumours i. Intramedullary ii. Extramedullary, growing from the DM internal layer, denticulate ligaments, pia mater, intradural spinal roots There is also a well-known Ellsberg’s classification of spinal cord tumours by their localisation to the spinal cord: dorsal (backward from a posterior dorsal root of a spinal nerve), dorsolateral (backward from denticulate ligament and dorsal roots), lateral, ventral (upward from anterior roots), and ventrolateral (between denticulate ligament and anterior roots). Clinical symptoms of spinal cord tumours develop slowly in children and adults. Spinal cord tumours in children show no clinical symptoms for a long time due to the great compensatory potential of the spine and spinal cord. Only largesize tumours produce clinical symptoms. Tumours located in the cauda equine have the longest clinical course, while tumours localised in the thoracic spine have the shortest clinical course. There are several stages of tumour growth: gradually progressing, acute, subacute, and remittent. The most frequent paediatric complaint is weakness in extremities, related to spastic or flaccid paralysis. Early-aged groups of children as a rule do not complain of weakness, which is why their motor activity should be thoroughly studied. Pain syndrome is one of the important early symptoms in adults with spinal cord tumours. Most often pain is localised in the spine and occurs in 28–59% of observations. Some patients complain of radicular pain spreading into lower or upper extremities or in the breast. Radicular pain is usually revealed in patients
Chapter 15
with intradural-extramedullary or extradural tumours. In young children, early-stage pain syndrome may manifest by increased irritability. Pelvic dysfunction is marked in 50% of patients with spinal cord compression. However, it is difficult to define physiological urination peculiarities in different age groups as well as disturbed innervation of the urinary bladder. As a rule, the primary symptom of pelvic dysfunction is enuresis. Congenital tumours often exhibit skin changes or stigmas, represented by subcutaneous lipomas, dermal sinuses, capillary haemangiomas, epithelial coccygeal canal, focal pilosis, pigmentation or depigmentation, etc. Curvature of the spine is most commonly revealed in the early-age groups of children, though it may occur in 25% of patients with spinal cord lesions. That is why some authors recommend studying posture in all children under examination in order to ascertain any oncological disease. CSF analysis in patients with spinal cord tumours frequently shows cellular-albuminous dissociations, which result in increased oncotic pressure and decreased CSF resorption, which in its turn leads to a hypertense—hydrocephalic syndrome—the primary clinical symptom of spinal cord tumours.
15.5 Intramedullary Tumours Incidence of intramedullary tumours (IMT) in all age groups is 10–18% of overall spinal cord tumours (Razdolsky 1958; Babchin 1962; Huk 1990; Ahadov 2000); it accounts for approximately 4% of all CNS tumours. IMT incidence in children is slightly higher, 6–10% (about a third of spinal cord tumours). Mainly IMT (according to some data, 95%) are represented by glial tumours. The latter comprises ependymomas (63–65%) and astrocytomas (24–30%), more seldom glioblastomas (7%), oligodendrogliomas (3%), and others (2%) (Jeanmart 1986; Norman 1987). Children show astrocytoma (ASC) predominance over ependymoma (EP) (Ball 1997). Adults reveal ASC predominance in the cervical spine and roughly equal incidence of ASC and EP in the thoracic spine. EP is most commonly seen in the spinal cord conus and lower segments (Zimmerman and Bilaniuk 1992). By origin, intramedullary tumours are described as benign, slowly growing tumours; by tumour growth and localisation, they are considered unfavourable from the point of view of their surgical removal. MRI is considered the leading imaging modality in radiographic diagnosis of intramedullary tumours. It is most sensitive in assessing changed spinal cord size and signal intensity from their tissues. Thus, when there is a suspicion of an intramedullary tumour growth, usually accompanied by thickening of the spinal cord, it is reasonable to use MRI (Miyasaka 1986; Carsin and Gandon 1987; Modic et al. 1989). T1-weighted sequences are considered the most informative for defining tumour localisation and size. Intramedullary tumours possess specific characteristics, which make these tumours different from other neoplasms. Sagittal and axial T1 images demonstrate an enlarged size of the spinal cord with mostly tuberous and uneven contours. Transverse
Spine and Spinal Cord Disorders
measurements show that tumour size in the infiltration zone may exceed its normal size by 1.5–2 times and in some cases, may reach the size of 20–25 mm. As a rule, the tumour involves several spinal segments. The intensity of MR signal on T1-weighted imaging varies from iso- to hypointense signal compared with healthy spinal segments, thus impeding assessment of the tumour extent. Intramedullary tumours have hyperintense signal intensity on T2-weighted sequences compared with normal spinal cord; signal intensity can be heterogeneous. It is practically impossible to determine exact tumour size and borders on T2weighted images, because peritumoral oedema has a hyperintense MR signal and thus merges with the tumour’s signal. MRI with CE allows determining tumour localisation and what is more important, extent of the infiltrative process in spinal cord. The role of contrast media is hard to underestimate when making a differentiated diagnosis of a great variety of intramedullary lesions.
15.5.1 Astrocytoma ASC is the most frequent type of spinal cord tumours in children; it makes up 50–60% of all intramedullary tumours and 4% of all primary CNS tumours. In adults, it is second by incidence after EP and makes up 24–30% of all intramedullary lesions (Manelfe 1992). ASC may develop at any age but most frequently, it occurs in the first three decades of life. ASC is benign in 75% of cases and malignant in 25%, irrespective of patient sex. ACS more often occurs in the thoracic spine followed by the cervical spine level. In the paediatric popula-
Fig. 15.45 Postmortem presentation (a 12-year-old patient). Diffuse
astrocytoma involved entire spinal cord
1125
tion, cervical tumours prevail (Epstein 1982). As a rule, ASC involves several spinal cord segments and in some cases occupies the entire spinal cord (Fig. 15.45). About a third of ASC have cysts of different sizes. Spondylography is not much of help in diagnosis of ACS, because radiographically visible vertebral body changes occur not as often as in EP cases. Myelograms of ASC show features most characteristic for intramedullary type of tumour growth. CT is also of a limited use, although its axial planes may reveal enlarged spinal cord. CT views of tumour density are not considered reliable for assessment of tumour location. Very rarely, it can demonstrate a cystic cavity of central localisation (Fig. 15.46). In the majority of cases, high-protein concentrations in the tumour cyst make it similar to that of brain density and thus, make its differentiation rather difficult. After CE there may appear a heterogeneous rise of density in pathologic tissues. Spiral thin-slice CT with further reconstructions, compared with MRI, has been found to be markedly worse for detecting and interpreting intramedullary changes, though it may visualise spinal cord thickening in the cervical spine (Mironov 2004). Spiral CT myelography has proved to be more informative for evaluation of thickening of the spinal cord and compression of subarachnoid spaces (Fig. 15.47). If we take the informative aspect of all imaging modalities used for visualisation of spinal cord pathology, then, no doubt, MRI is considered a method of choice. Sagittal T1weighted MRI is good at detecting thickening of the spinal cord with uneven and tuberous contours. As for the tumour tissue, it practically does not differ from that of the spinal cord or is slightly hypointense (Figs. 15.48, 15.49). The accompanying cystic pathology has different manifestations in this regimen. Cystic fluid may have MR signal intensity very close to that of CSF or be slightly hyperintense in increased protein concentrations. ASC and peritumoral oedema reveal hyperintense MR signal on T2-weighted sequences (Fig. 15.50). Cystic changes in tumour tissues may lead to T2 lengthening. Haemorrhage is less frequent in ASC than EPs (Figs. 15.51, 15.52). In the majority of cases, ACS exhibits a typical hyperintense T1-weighted signal of a homogeneous or heterogeneous character after the contrast media has been introduced (Figs. 15.53–15.56). In marked enhancement one can see improved differentiation of the tumour and peritumoural oedema (Sze et al. 1988; Parizel et al. 1989; Barkovich 2000). Though contrast-accumulated tumour zone does not reflect
Fig. 15.46a,b Cervical spinal cord astrocytoma. CT images show the enlargement of spinal cord with cystic intramedullary changes
1126
Chapter 15
Fig. 15.47a,b Thoracic spinal cord astrocytoma. CT myelograms show the uneven narrowing of subarachnoid spaces. There is enlargement of spinal cord with uneven contours
Fig. 15.48a–c Spinal cord astrocytoma. Sagittal T2-weighted imaging (a,b) and T1-weighted imaging (c) demonstrate expansion of spinal cord from medulla oblongata to the conus. Tumour has high MR signal intensity from infiltrative part on T2-weighted imaging.
On T1-weighted imaging, signal from tumour’s tissue does not differ with brain. Small cystic lesion in the projection of medulla oblongata is observed on MRI
Fig. 15.49a,b Cervical spinal cord astrocytoma. Sagittal MR images (a T2-weighted imaging, b T1-weighted imaging) show the solid tumour with relatively heterogeneous structure. Spinal cord as well as medulla oblongata are enlarged
Spine and Spinal Cord Disorders
1127
Fig. 15.51a,b Cervical spinal cord astrocytoma. Sagittal MR images
Fig. 15.50a,b Thoracic spinal cord astrocytoma. Sagittal MR images
(a T2-weighted imaging, b T1-weighted imaging) show the solid tumour with relatively homogeneous structure and hyperintense MRsignal. There are rostrally and caudally satiated cystic cavities
(a T2-weighted imaging, b T1-weighted imaging) demonstrate the intramedullary tumour with heterogeneous structure. Cystic components of the tumours have high signal intensity on T2-weighted imaging and hypointense MR signal on T1-weighted imaging. Hypointense MR signal in lower aspects of tumour’s cyst indicates haemosiderin deposition (as a sign of old haemorrhage) arrow
Fig. 15.52a–f Thoracic spinal cord astrocytoma. Sagittal MR images (a,b T2-weighted imaging, c T1-weighted imaging) show the intramedullary tumour with heterogeneous structure. There are many cysts within of tumour tissue with haemosiderin deposition. After CE (d–f), the nodule of tumour became clearly visible
1128
Fig. 15.53a–c Spinal cord astrocytoma. Sagittal MR images. T1weighted imaging before (a) and after (b,c) CE show enlargement of the whole spinal cord. The solid part of the tumour moderately accumulates the contrast medium. There are cystic tumour components rostrally and caudally of enhanced part of neoplasm (enhancement of the tumour cystic walls are observed)
Fig. 15.55a–e Cervical spinal cord astrocytoma (a 15-year-old child). Sagittal MRI in T1 (a), T2* (b) demonstrates local enlargement of cervical spinal cord with hypointense signal intensity on
Chapter 15
Fig. 15.54a,b Cervical spinal cord astrocytoma with spreading on
medulla oblongata. Sagittal MR images. T1-weighted imaging before (a) and after (b) CE demonstrates the intramedullary tumour with heterogeneous structure. Cystic components of the tumours have low signal intensity on T1-weighted imaging. Tumour tissue has moderate enhancement, making visualisation of tumour margins more obvious
T1-weighted imaging and slightly hyperintensity on T2*. Postcontrast sagittal, coronal, and axial images (c–e) show a heterogeneous CE of tumour tissue
Fig. 15.56a–d Thoracic spinal cord astrocytoma. Sagittal T2-weighted imaging (a) and T1-weighted imaging (b) identify an intramedullary tumour, which has heterogeneous structure. There are cystic parts above and below solid tumour. Postcontrast sagittal (c) and coronal (d) images show focal enhancement from infiltrative part of tumour
Spine and Spinal Cord Disorders
real tumour extent in the spinal cord, it correlates with the disturbed BBB, which is of primary importance when choosing a site for of laminectomy or tumour biopsy. In rare cases, there may be present atypical forms of brain tumours involving brain and spinal cord substance. It is practically impossible to diagnose a tumour without target (rarely open) biopsy (Fig. 15.57). Glioblastoma is diagnosed extremely rarely (it makes up 7% of all spinal ASC). Being one of the most malignant tumours, it is characterised by fast (sometimes impetuous) growth and neurological symptoms that are marked in the early stage of spinal tumour development. MRI demonstrates a typical tumour extension along the spinal cord and a vast peritumoral oedema. Contrast-enhanced MRI reveals a heterogeneous tumour with early metastases in the subarachnoid spaces (Fig. 15.58) and unfavourable prognosis. ASC should be differentiated from ependymomas, hemangioblastomas, intramedullary metastases, spinal cord ischaemia, and inflammatory processes (myelitis, multiple sclerosis).
15.5.2 Ependymoma EP is described as the most frequently occurring type of intramedullary tumours in adults over 30. They constitute about 13% of all spinal cord tumours (Youmans 1982) and 65% of all glial intramedullary tumours in adults. EP predominates in males (60%). Patient average age is 40 years. EP is the second frequently occurr in type of intramedullary tumours in children and makes up 30% of all spinal cord tumours. EP starts to grow from ependyma cells of the central canal and spreads along the whole spinal cord length and its filum terminale. In 50–60% of cases, EP is localised in the spinal cord conus and cauda equina roots. It may occur in the cervical and thoracic spinal cord. In the latter, EP causes spinal cord thickening. When localised in the conus and roots, it acquires characteristics of extramedullary tumours. Sometimes EP of this region may totally involve the spinal canal, reaching lengths of 8–12 cm (Figs. 15.59, 15.60). EP belongs to the group of benign, slow-growing tumours. EP differs from other spinal cord gliomas by the abundant blood supply, often leading to development of subarachnoid and intratumoral haemorrhages. EP contains cysts of different sizes in more than 45% of cases. Slow-growing EP, especially in cauda equina roots, may lead to vertebral body changes, Elsberg-Dyke symptome, and excavation of posterior of surface vertebral bodies, demonstrated by radiography. Myelography with water-soluble contrast media is usually useful in detecting spinal cord thickening in the tumour region with different degrees of SAS compression and diffusion of the contrast media in the form of thin strips around the tumour or thickened spinal cord. CT has been proved less effective in diagnosis of EP. CT without CE is uninformative because it is very difficult to differentiate an isodense tumour tissue from the spinal cord (Fig. 15.61). Hyperdensity can be revealed in rare cases—intratumoral acute haemorrhages or calcification (Fig. 15.62). CT with
1129
intravenous enhancement shows varied contrast media accumulation (Fig. 15.63). In some cases, it may result in improved identification of a tumour on CT, especially in sagittal and coronal reformations. CT myelography is considered more informative in diagnosis of EP because it demonstrates the increased volume of the spinal cord and SAS narrowing. In some cases, delayed examination (6–8 hours since endolumbar contrast media introduction) can identify tumour-related secondary syringohydromyelia caused by penetration of the contrast media into cystic cavities. At the same time, despite the fact that CT and spiral CT myelography are sufficient to visualise thickening of the spinal cord at the lesion site, neither of these imaging modalities can confidently differentiate the solid tumour component from the cystic one. MRI is considered a method of choice for diagnosis of EP (like in cases with ASC). MRI is useful in detecting the exact tumour node location and differentiating the solid EP components from the cystic ones. A fusiform thickening of the spinal cord in patients with cervical or thoracic spine tumours appears as a heterogeneous signal from the tumour tissue with tumour-related changes (cysts, haemorrhages, and calcification) on T1-weighted images. The tumour has tuberous contours and is usually reported to have iso-or hypointense MR signal compared with the spinal cord substance (Figs. 15.64, 15.65). EP of cauda equina roots has a typical solid structure. MRI very well demonstrates the vertebral canal lumen occupied by the tumour. Spinal cord conus is usually displaced (Fig. 15.66). It is difficult to differentiate at this level small solid EP from neurinoma of cauda equina roots. EP manifestations on T2-weighted MRI are nonspecific. The tumour solid part usually has a moderately hyperintense MR signal; however, the brightness of signal is not as high as that of a cystic tumour. Peritumoral oedema is identified as a hyperintense signal zone in the form of cone with a tumour-pointed base. In the acute or subacute stage of haemorrhage, the tumour stroma reveals a hyperintense signal on T1-weighted images and a hypo-/hyperintense signal on T2-weighted images. Typical MR manifestation of “old” haemorrhage is a hypointense thin rim, better revealed at the tumour periphery on T2 MRI. It is caused by haemosiderin deposits (Figs. 15.67–15.70). Such a low MR intensity signal can be marked on dynamic postoperative MRI for a long time (Fig. 15.71). Intravenous contrast–enhanced MRI demonstrates a fast and rather homogeneous hyperintense signal from the tumour tissue (Figs. 15.72, 15.73). Differentiation of EP components from tumoral oedema has been markedly improved. However, in clinical practice one may observe a typically low and heterogeneous contrast accumulation in EP or its full absence on contrast-enhanced MRI (Fig. 15.74). Overall, CE is an important part of MRI diagnosis of EP. If primary contrast accumulation by tumour tissues is poor, it is useful to utilise double dosage of contrast media for better visualisation of the disturbed BBB (Fig. 15.75). Accurate diagnosis of small-size tumour nodes accompanied by marked changes (for instance, change of spreading syringohydromyelia) is hardly possible without CE (Fig. 15.76).
1130
Fig. 15.57a–i Wide-spreading astrocytoma CNS (a 2-year-old child). MRI of the entire spine (a–c) demonstrates uneven enlargement of the spinal cord, extending from foramen magnum to conus. There is heterogeneous CE along surface of spinal cord. Lumbar SAS fills by tumour tissue. Brain MRI shows diffuse–focal involvement of brain
Chapter 15
tissue as well supratentorial as subtentorial location (d–f). Postcontrast images (g–i) reveal focal contrast medium accumulation along arachnoids around brainstem and into suprasellar region. There is hydrocephalus with occlusion on foramen of Magendie level
Spine and Spinal Cord Disorders
Fig. 15.58a–f Glioblastoma of cervical spinal cord. T2-weighted imaging (a) and T1-weighted imaging before (b,c) and after (d–f) CE demonstrate marked thickening of spinal cord. There are microhae-
1131
morrhage foci in affecting part of spinal cord. Post-CE images show pronounced contrast medium accumulation in tumour tissue and wide dissemination along arachnoids of spinal cord
1132
Chapter 15 Fig. 15.59a,b Ependymoma of conus spinal cord and cauda equina (a 15-year-old child). Sagittal MRI reveals a solid tumour, which has a isointense signal on T1-weighted imaging (a) and hyperintense signal on T1-weighted imaging (b) at the level T10– L2. The spinal canal is dilated at the level of tumour location
Fig. 15.60a–c Ependymoma of cauda equina. Sagittal MRI visual-
ises a large solid tumour that has hyperintense signal on T2-weighted imaging (a) and isointense signal with spinal cord on T1-weighted imaging (b). Tumour tissue occupies the spinal canal at the T12–
L5 level. Tumour shows the moderate relatively homogeneous CE (c). There is hyperintense signal in conus of compressed spinal cord (myeloischaemia)
Spine and Spinal Cord Disorders
1133
Fig. 15.61a–d Cervical spinal cord ependymoma. Axial CT (a,b) images show enlargement of cervical spinal cord at the C2–C3 level. MRI in T2 sagittal (c) and T1 coronal (d) planes demonstrates intramedullary tumour with solid and cystic components with expansion of medulla oblongata
Fig. 15.62a,b Cervical spinal cord ependymoma (a 12-year-old child). Axial CT without CE reveals a thickening of medulla oblongata. Cystic part of the lesion is hypodense. There are small calcifications in the tumour stroma and its periphery
1134
Chapter 15
Fig. 15.63a,b Lumbar spine ependymoma. Axial CT before (a) and after (b) CE shows solid tumour with small cyst in lateral part on the right, which is occupied lumen of spinal canal. There is no obvious CE
Fig. 15.64a–d Cervical spinal cord ependymoma. Sagittal T2-weighted imaging (a) and T1-
weighted imaging (b) show an intramedullary tumour at the C1–C2 level, which has small cysts (high signal on T2-weighted imaging) in central part. There is oedema of spinal cord extending inferiorly from C2 to C7 levels. Postcontrast T1-weighted imaging in sagittal (c) and coronal (d) planes demonstrates the marked CE of solid part of the tumour
Spine and Spinal Cord Disorders
1135
Fig. 15.65a–f Cervicothoracic spinal cord ependymoma. Sagittal T2 (a) and T1 (b) images show expansion of spinal cord from C3 to T5 levels. Solid part of the tumour has slightly hyperintense signal on T2 and is situated at the T1–T5 levels. There are cystic cavities in upper and lower parts of spinal cord. Postcontrast images (c–f) demonstrate moderate enhancement of the solid tumour. There is no CE in walls of the cystic cavities (which designates them as syringohydromyelic cavities)
1136
Chapter 15
Fig. 15.66a–f Ependymoma of conus spinal cord and cauda equina. MRI in sagittal, coronal, and axial planes (a–f) demonstrates the solid tumour at the T12–L1 levels, which is occupied the spinal canal. Tumour has hyperintense MR signal on T2-weighted imaging and compresses the conus. Tumour looks like an extramedullary lesion
Spine and Spinal Cord Disorders
Fig. 15.67a–d Cervical spinal cord ependymoma. Series T2-weighted imaging (a) and T1-weighted imaging (b) show the
cystic intramedullary lesion at the C1–C6 levels. The cyst has a hyperintense signal in all sequences in comparison with CSF. Arrows indicate the sites of haemosiderin deposition (“old” haemorrhage). Sagittal (c) and coronal (d) postcontrast images identify peripheral CE more clearly distinguishing infiltrative and cystic parts of the tumour
1137
1138
Fig. 15.68a–f Cervical spinal cord ependymoma. Sagittal T2 (a), T1 (b), and coronal FLAIR (c) MR images show heterogeneous tumour with cystic and solid components, invading the medulla oblongata. Hypointense signal on tumour periphery indicates the “old” haem-
Chapter 15
orrhage (haemosiderin deposition). Postcontrast MRI in sagittal (d) and axial (e,f) planes demonstrate the intense heterogeneous enhancement with central necrotic area
Fig. 15.69a–d Ependymoma of conus medullaris. Sagittal T2-weighted imaging (a,b) and T1-weighted imaging (c,d) show the intramedul-
lary tumour expending the conus medullaris. Small foci of hyperintense MR signal on T1 mode represents the subacute haemorrhages
Spine and Spinal Cord Disorders
1139
Fig. 15.70a,b Relapse of conus medullaris ependymoma (a 14-year-old child). Sagittal MRI in T1 (a) and T2 (b) modes reveal a large tumour into the lumbar spine canal, which is extending through the postoperative defect posteriorly. There is subacute haemorrhage (hyperintense signal) in the lower portion of the tumour
Fig. 15.71a–c Follow-up MRI 1 year after resection of cervical spinal cord ependymoma. MRI in T1 (a), T2 (b) and T2* (c) modes dem-
onstrates postoperative changes of spinal cord with haemosiderin deposition and low signal areas in all sequences. There are no signs of ependymoma remnants
1140
Chapter 15
Fig. 15.72a–e Lumbar spine ependymoma (1 year after irradiation therapy). Axial CT (a) reveals the solid tumour that occupies the spinal canal. MRI before (b,c) and after (d,e) CE demonstrates the large tumour with solid structure and marked contrast medium accumulation. Small cysts are better visualised after CE. There are postradiation changes in lumbar vertebral bodies
Spine and Spinal Cord Disorders
Fig. 15.73a–c Ependymoma of conus medullaris (a 14-year-old
child). Series MRI in T2 (a) and T1 after CE (b,c) demonstrate the solid tumour at the L1–L3 levels. Tumour has hyperintense signal on
1141
T2-weighted imaging and marked CE on T1-weighted imaging. There is excavation of posterior surface of vertebral bodies
Fig. 15.74a–c Cervical spinal cord ependymoma. Series of sagittal MRI in T2 (a), T1 before (b) and after (c) CE show intramedullary tumour
with solid structure at the C2–C6 levels. Tumour has a slightly hyperintense signal in comparison to spinal cord and no accumulation of contrast medium
1142
Chapter 15
Fig. 15.75a–h Cervicothoracic spinal cord
ependymoma. Series of sagittal MRI in T1 mode before (a,b) and after standard dose of contrast medium (c,d) demonstrate the intramedullary tumour with heterogeneous structure and CE at the C7–T4 levels. There are no obvious arguments for expanding of the tumour in upper cervical spine. After injection of additional contrast medium dose the foci of contrast accumulation at the C2–C5 levels were found (e,f). Axial T1-weighted imaging after standard dose of contrast medium (g,h upper row) and double-dose CE (g,h lower row) better demonstrates a difference between CE doses
Spine and Spinal Cord Disorders
1143
Fig. 15.76a–f Conus medullaris ependymoma. Series MRI in T2 (a,b) and T1 (c,d) modes demonstrate a syringohydromyelic cyst expand-
ing from the upper cervical spinal cord inferiorly. Postcontrast sagittal (e) and coronal (f) images identify small tumour located in conus medullaris
Use of CE is of great importance for preoperative planning and control of tumour growth or recurrence (Fig. 15.77). Giant-size EP with expressed extramedullary extension is marked very seldom (Fig. 15.78). EP metastases in form of multiple extramedullary nodes of different size may invade SAS of the spinal cord; however, it is a more characteristic feature of the anaplastic group of tumours. Similarly, anaplastic EP can be hardly differentiated from benign tumours by MR manifestations (Figs. 15.79, 15.80).
15.5.3 Oligodendroglioma ODG is revealed significantly rarer compared with the abovedescribed types of glial tumours. According to Zimmerman and Bilaniuk (1988), incidence of ODG does not exceed 4% of all intramedullary tumours. Clinical signs of ODG are similar to those of the other gliomas. Variability of tumour vascularisation may result in haemorrhage that can be revealed by CT. MRI manifestations of ODG are nonspecific. Hyperintense
signal (from methaemoglobin) on T1-weighted images or a hypointense signal (from haemosiderin) on T2-weighted images may be the evidence of haemorrhage.
15.5.4 Hemangioblastoma HMB makes up 1.6–4% of all spinal cord tumours. In about 33% of cases, HMB is combined with manifestations of von Hippel-Lindau disease. As a rule, these tumours have intramedullary localisation but may have an extramedullary location as well. HMB invades thoracic spinal cord in 50% of cases and cervical spinal cord in 40% of cases. As GBM is a richly vascularised tumour, it may clinically manifest by signs of SAH. In the majority of cases HMB is a solitary tumour but in 20% of cases it may be multiple (as a rule, combined with von Hippel-Lindau disease). Up to 60% of patients with HMB often reveal syringohydromyelic cavities. Cystic cavities may be of large sizes and reveal caudal or cranial spreading from the tumour solid node.
1144
Chapter 15
Fig. 15.77a–c Relapse of conus medullaris ependymoma. Sagittal MRI in T2 (a), T1 before (b) and after (c) CE demonstrates three tumoral nodes located at the caudal part of spinal cord. There are postoperative changes in the soft tissue in back
Fig. 15.78a–d Cervicothoracic spinal cord ependymoma. MRI in T2 (a,b) and T1 (c,d)
shows a huge, solid tumour located on the ventral surface of the spinal cord. Tumour has hyperintense MR signal on T2- and hypointense signal on T1-weighted imaging compared with the spinal cord. There is extra- and intramedullary growth of the tumour
Spine and Spinal Cord Disorders
1145 Fig. 15.79 Lumbar spine anaplastic ependymoma. Sagittal T2 (a), T1 before (b) and after (c) CE visualise a large solid tumour with moderate enhancement, which occupied the spinal canal at the L3–S3 levels. There is destruction of S1–S3 vertebrae
Fig. 15.80a–c Lumbar spine anaplastic ependymoma. T2-weighted imaging (a,b) and T1-weighted imaging after CE (c) visualise a heterogeneous tumour with peripheral CE. There are subarachnoid metastases around conus medullaris
Spinal angiography reveals a richly vascularised tumour node with large supplying arteries (Fig. 15.81). When HMB is suspected, it is reasonable to perform selective spinal angiography. Simultaneously, catheterisation of tumour-supplying arteries is undertaken for preoperative vascular embolisation. CT with CE provides good visualisation of the contrastaccumulating HMB (Fig. 15.82). Contrast-enhanced CT more clearly reveals solid and cystic tumour components. MRI usually demonstrates a hypo- or isointense signal on T1-weighted images and a hyperintense signal on T2-weighted images (Figs. 15.83, 15.84). Cystic cavities reveal either a CSF-similar or slightly hyperintense MRI signal. Though MRI manifestations of HMB of the spinal cord have no specific features, there are several signs that might be useful for making the correct diagnosis, namely: • Combination of large-size cysts with a small solid tumour node • Presence of tortuous and enlarged SAS vessels (Fig. 15.85; see Fig. 15.83) • Multiple lesions (von Hippel-Lindau disease) (Fig. 15.86, 15.87) Additional CE helps to reveal its intense accumulation by the tumour. Signal intensity from the walls of syringohydromyelic cysts usually is not increased after CE. The tumour’s arterial vessels remain dark compared with veins (Fig. 15.88). Small-size tumour nodes can be visualised only on contrastenhanced MRI (Fig. 15.89).
Fig. 15.81 Cervical spinal cord hemangioblastoma. Selective spinal
angiography reveals abundant vascularised the tumour at C4–C7 levels: before (on the left) and after (on the right) embolisation
1146
Chapter 15
Fig. 15.82a,b Cervical spinal cord hemangioblastoma. Axial CT before (a) and after (b) CE reveals a small, intensely enhanced nodule
Fig. 15.83a–d Cervical spinal cord hemangioblastoma. MRI in T2 (a) and T1 (b–d) modes visualises intramedullary tumour with isointense
features compare to spinal cord. There are large cystic cavities (hydromyelia) around a nodule. Hypertrophied vessels in subarachnoid space and tumour stroma are observed (arrow)
Fig. 15.84a–c Thoracic spinal cord hemangioblastoma. Sagittal T1-weighted imaging (a–c) demonstrates the extending hydromyelia from
foramen magnum to conus medullaris. There is nodule of tumour at the T7–T8 level (arrow)
Spine and Spinal Cord Disorders
1147
Fig. 15.85a,b Thoracic spinal cord hemangioblastoma. Sagittal T2
images show the nodule of tumour with a lot of pathological vessels. There are hydromyelic cavities above and below the tumour
Fig. 15.86a–c von Hippel-Lindau syndrome. Multiple cervical spinal cord hemangioblastomas. Sagittal T1-weighted imaging (a–c) after CE demonstrates a multiple enhanced lesions. Large vessels in SAS are not enhanced
Fig. 15.87a–c von Hippel-Lindau syndrome. Multiple cervical spinal cord and brain hemangioblastomas (a 15-year-old child). MRI of brain (a) and cervical spine (b,c) with CE shows multiple enhanced lesions
1148
Fig. 15.88a–i Cervical spinal cord hemangioblastoma. MR T2 (a), T1 before (b) and after (c–e) CE reveal intramedullary tumour at the C1–C2 level. There are syringohydromyelic cysts extending inferiorly of nodule. Hemangioblastoma enhances strongly and intensely. Hypertrophied vessels in SAS and tumour stroma are not enhanced.
Chapter 15
Tumour tissue characterises by decrease of diffusion parameters DWI (f), ADC map (g). Fractional anisotropy map (h) and tractography (i, j) demonstrate disruption of fibre tracts at tumour level. j–l see next page
Spine and Spinal Cord Disorders
1149
Fig. 15.88j–l (continued) Tumour has extremely high values of CE on CT (k) and cerebral blood volume on CBV map (l)
Fig. 15.89a–f Thoracic spinal cord hemangioblastoma. Sagittal T2-weighted imaging (a) and T1-weighted imaging (b) shows the syringohydromyelic cysts extending from C2 to T6. There is hyperpulsation artefact within a cavity. Only postcontrast images (c–i) could be able to detect small nodule of tumour at T5 (arrow)
1150
Chapter 15
15.5.5 Rare Intramedullary Tumours Spinal cord metastases occur seldom and make up about 5% of all CNS metastases (Grem 1985; Post 1987). According to autopsy analysis, intramedullary tumours occur in 1–2% of cancer patients, while brain tumours make up 18–24% (Winkelman 1987; Shiff et al. 1996; Crasto 1997; Mortimer 2001). Metastases may be multiple; there can be intramedullary and extradural tumour nodes. Spinal cord metastases are usually caused by primary malignant CNS tumours disseminating along the CSF pathways (medulloblastoma, anaplastic EP, GMB) or a haematogenic tumour disseminating from other organs. Here, most frequent is lung cancer (it makes up 50% of all intramedullary metastases), followed by breast cancer, lymphoma, kidney cancer, and melanoma. MRI is considered a method of choice for identification of spinal metastases. T1-weighted images demonstrate a pathologically decreased intensity signal associated with spinal cord thickening in this zone. Spinal cord tumours surrounded by a perifocal oedema have an iso- or hyperintense signal on T2 MRI. Contrast-enhanced MRI results in improved sensitivity and specificity of diagnosis. Tumour metastases have been known to quickly and intensely accumulate the contrast media, thus providing better visualisation of small intramedullary tumour nodes and tumour-associated metastatic lesions of the spinal cord arachnoid (Crasto 1997; Rallmes 1998). Such tumours like primary lymphoma (Bluemke 1990), schwannoma, hamartoma (Norman 1987), and primary melanoma (Larson 1987) extremely rarely occur in the spinal cord. The bulk of authors believe that MRI cannot be relied on when differentiating between different types of intramedullary tumours. However, there are a number of characteristic features that suggest various types of tumours. Thus, EP has a compact form and a hyperintense MR signal in all scanning regimens. The most characteristic of EP is tumour nodes located in the region of spinal cord conus and epiconus as well as cauda equina roots with their further transformation into extramedullary lesions. ASC cause a fusiform thickening of the spinal cord with vague contours. They exhibit an isointense signal on T1- and hyperintense signal on T2-weighted images. In children, ASC are characterised by diffuse tumour growth and extensive spreading along the spinal cord (sometimes along its entire length). Like EPs, they have cysts. Hemangioblastomas usually look like compact solid nodes with large rostral or caudal cystic cavities. Diagnosis is simplified when von Hippel-Lindau characteristic features are revealed or MRI or selective angiography detects tumour-supplying large vessels. Paramagnetic contrast media are very useful for specifying localisation and extent of intramedullary tumours. Cystic spinal cord changes caused by intramedullary tumours should be differentiated from syringomyelia. Signal intensity exhibited by cystic tumours is higher than that of CSF in SAS and syringomyelia cavities. Internal contours of cystic tumours are vague and rough. As cystic tumours are known to have high protein content, it is characteristic of them to reveal shortened T1 relaxation time consistent with an increase of
Fig. 15.90a,b Syringohydromyelia (a 15-year-old child). Sagittal
MRI (a–b) shows intramedullary cavity extending from C2 to thoracic level. There are a lot of septations inside the cavity.
signal on T1-weighted images. Cystic tumour signal intensity on T2 images is normally higher than that the solid tumour.
15.5.6 Syringohydromyelia Syringohydromyelia is characterised by a presence of longitudinally oriented CSF-filled cavities which have flat internal walls, intersections (synechias) in the cystic cavity, often combined with Arnold-Chiari malformation and hyperpulsation of the cystic content (Figs. 15.90, 15. 91). MRI is unequalled in its ability to demonstrate the extent of spinal cord cysts. Cysts may be localised or may involve the entire spinal cord (Figs. 15.92, 15.93). There are two types of cysts, depending on cyst contours at the junction with healthy spinal cord segments, syringomyelia with high (rounded contour) or low (pointed contour) pressure (Figs. 15.94, 15.95). Spiral CT is informative only for the cervical spinal cord segment, when sufficient differentiation of the spinal cord and SAS is marked. Absence of contrast accumulation by the cystic walls is the characteristic feature of syringohydromyelia (Fig. 15.96), and CE is usually performed in all cases to not to miss a brain tumour (for instance, HMB or EP). In separate cases when there is an evidence of a focal traumatic spine injury, MRI is useful for determining the cause of intramedullary cavity formation (Fig. 15.97).
15.6 Extramedullary–Intradural Tumours Extramedullary–intradural tumours make up 53–68.5% of all spinal cord tumours (Stark and Bradley 1988; Manelfe 1992). Of them, neurinomas and meningiomas occur in 30–40 and 25% of cases (Levy 1982; Solero 1989; Scotti 1992; Kleihues
Spine and Spinal Cord Disorders
1151
Fig. 15.91a–e Syringohydromyelia. Sagittal T2weighted imaging (a,b) and T1-weighted imaging (c,d) demonstrates large syrinx with multiple septations of cervicothoracic spinal cord. MR signal on T1-weighted imaging from cystic fluid is identical to CSF in subarachnoid space. The inner walls of the cavities are even. On T2-weighted imaging, the areas of hypointense signal are observed due to pulsatile motion inside a cavity. DWI map (e) shows the bright red from cystic lesion (area of unrestricted diffusion)
1152
Chapter 15
Fig. 15.92a–e Focal syringohydromyelia
secondary to Chiari I malformation. Sagittal (a,b), coronal (c) and axial (d,e) T2- and T1-weighted imaging demonstrate local intramedullary syrinx at C3–C6 levels. There is Chiari I malformation. Walls of the syrinx are even in all sequences and planes
Fig. 15.93a,b Syringohydromyelia. Sagittal MRI in T1 (a,b) mode shows the intramedullary cavity extending from C1 to the conus medullaris. The inner walls of the cavities are even. MR signal from cystic fluid is similar to CSF in subarachnoid space
Spine and Spinal Cord Disorders
1153
Fig. 15.94a–c Syringobulbia and syringohydromyelia. Sagittal MR T2-weighted imaging (a,b) and T1-weighted imaging (c) shows the large
syrinx with medulla oblongata involvement (syringobulbia). There are many of septations within the cavity. Hyperpulsation artefact is observed on T2-weighted imaging
Fig. 15.95a–e Syringohydromyelia. MRI in
T2 (a,b) and T1 (c–e) modes shows the thin syrinx extending from cervical to thoracic spinal cord. There is Chiari I malformation. The upper and lower margins of syrinx are sharp
1154
Chapter 15 Fig. 15.96a–f Syringohydromyelia. MRI in T2 (a) and T1 (b–f) modes demonstrates the syrinx of the cervical spinal cord with even walls, septations, and hyperpulsation artefact on T2-weighted imaging. There is no focal CE inside the cavity (d–f) after intravenous injection of contrast medium. Upper and lower margins of cavity are rounded
Spine and Spinal Cord Disorders
1155 Fig. 15.97a–f Posttraumatic syringo hydromyelia. MRI in sagittal (a), coro nal (b) and axial (c,d) projections in T2 as well T1 (e,f) modes visualise traumatic disk her niation at the T6– T7 level with local compression of the spinal cord and small syrinx extending inferiorly
1156
2000). Tumours of other histologic origin (angiomas, lipomas, metastases, etc.) are not so frequent. In the paediatric age group, extramedullary–intradural tumours constitute 10–15% of all spinal cord tumours. Of them, the most frequently occurred types of tumours are neurinomas, metastases from primary intracranial tumours, congenital lipomas, dermoids, and epidermoids. Meningiomas in children unlike in adults are practically not revealed (about 3% of observations). These tumours are located between the dura and pia mater. They are characterised by spinal cord compression (not thickening) and SAS enlargement above and below the tumours. Most tumours of this localisation are typically well circumscribed among adjacent structures. The exception is massive metastases in the spinal cord arachnoids with the tumour nodes poorly differentiated from the spinal cord tissue, even in cases with CE. Spiral CT with CE and spiral CT myelography play an important role in assessment of extramedullary lesions, thus allowing determining size and structure of a pathological lesion in a number of cases. Still, according to the majority of reviews, MRI is considered the most informative method of diagnosis of extramedullary–intradural tumours. Additional intravenous CE results in increased MRI sensitivity and improved differentiated diagnosis of tumours and tumour-related pathological changes.
15.6.1 Tumours of the Spinal Nerve: Neurofibromas and Neurinomas (Schwannomas) These tumours make up 30% of all primary spinal tumours, which more often occur in the cervical and thoracic than in the lumbar segments (Woodruff et al. 2000). They have an ovoid form and are 2–3 cm in size (they may reach larger sizes in the cauda equine region). Growing out of sensitive dorsal roots, they form on the posterior-lateral surface of the spinal
Fig. 15.98a–c Intradural extramedullary tumours. Case 1. Lateral X-
ray film of lumbar spine demonstrates excavation of the posterior lumbar vertebrae bodies surface. There are multiple enlargements of neural foramina due to large neurofibroma. Case 2. C1–C2 neu-
Chapter 15
cord. As a rule, these tumours are encapsulated and separated from the adjacent structures; they may also contain cysts of different sizes (Conti et al. 2004). In children the tumours of spinal roots are one of manifestations of neurofibromatosis (type I: neurofibroma, type II: schwannoma) unlike in adults, when they are considered independent tumours. In that case, they can be multiple (Akeson et al. 1994). In 15–25% of cases, these tumours can spread extradurally through the intervertebral foramen, the so-called hourglass- or dumbbell-shaped neurinomas, mostly characteristic for the cervical spine. Such a tumour growth may result in typical bone changes best revealed by routine spondylography (Fig. 15.98). Myelography is informative only for small-size tumours that do not induce spinal cord SAS block. The role of these imaging modality selected for determining a tumour size is considerably reduced in complete SAS compression. At present, when an intradural tumour is suspected (including intramedullary lesions), the majority of scientific centres prefer do not use myelography because it has proved to be highly invasive and non-informative. Compared with spondylography, CT and spiral CT are particularly useful in detecting a tumour or tumour-related pathological changes, especially when dealing with cervical spine or hourglass-shaped tumours (Figs. 15.99–102). Spinal angiography of extramedullary tumours is used on condition of strict indications only; most commonly, it is used for patients with large paravertebral tumours. Here two main tasks are set: first, to define tumour relationship with vertebral and carotid arteries (shifts, deformations, wrapping) and second, to determine blood supply of a tumour (Fig. 15.103). Most neurinomas have a round form and circumscribed contours on T1-weighted images. Tumour intensity signal is practically similar to that of the spinal cord tissue. The spinal cord turns to be shifted aside and contralaterally compressed against the spinal canal wall. Sagittal views in that case seem to be insufficient for defining tumour location and thus it is reasonable to obtain coronal and axial MR planes images. As a rule,
rofibroma. Lateral X-ray film shows enlargement of neural foramen between C1–C2 vertebrae. Axial CT reveals dumbbell solid tumour extending as well into spinal canal as extravertebrally
Spine and Spinal Cord Disorders
1157
Fig. 15.99a–c Dumbbell neurinoma at C3–C4. Series axial CT (a–c) shows the solid tumour extending as well into spinal canal as extraver-
tebrally with enlargement of neural foramen
Fig. 15.100a,b Neurinoma at C1–C3. Axial CT (a) and coronal reformation (b) after CE demonstrates the solid tumour located in the left side of spinal canal (arrow). The spinal cord is dislocated to the opposite side
1158
Chapter 15
Fig. 15.101a–c Dumbbell neurinoma at C2–C3. Series CT with CE (a–c) reveals hypodense lesion extending along the spinal root extravertebrally. There is CE in the tumour capsule
Fig. 15.102a–e Dumbbell neurinoma at C1–C2. Series CT with CE (a, b) demonstrates extramedullary tumour at C1–C2 level extends into the left neural foramen. Sagittal T2-weighted imaging (c) and T1weighted imaging (d) clearly depicts the relationship between tumour and spinal cord. Neurinoma has hyperintense signal on T2-weighted imaging (e)
Spine and Spinal Cord Disorders
1159
Fig. 15.103a–e Neurofibroma at C1–C2. MR T2 (a) and postcontrast T1 (b,c) images demonstrate dumbbell neoplasm with hypointense signal on T2-weighted imaging and marked enhancement on T1-weighted imaging. The spinal cord is partially dislocated. DSA with examination of right vertebral artery territory (d,e) shows vascular mass with blood supplying from short muscular branches of vertebral artery
Fig. 15.104a–c Neurinoma at L1. Sagittal
(a), coronal (b) T1-weighted imaging and coronal T2-weighted imaging (c) demonstrates extramedullary mass lesion with hypointense central part (on T1-weighted imaging), which dislocates conus medullaris. Tumour has hyperintense signal on T2-weighted imaging; the borders of the tumour become poorly distinguished on background high signal from CSF
1160
Chapter 15
Fig. 15.105a,b Neurinoma at L3–L5. Sagittal T1-weighted imaging (a) and T2-weighted imaging (b) show extramedullary lesion that has isointense signal on T1- and hyperintense signal on T2-weighted imaging. High signal from CSF of lumbar spinal canal practically hides a tumour
Fig. 15.106a–d Neurinoma at L1–L2. MR T1-weighted imaging (a,b) and T2-weighted imaging (c,d) demonstrate small extramedullary tumour located between cauda equina roots. On T1-weighted imag-
ing, tumour has isointense with spinal cord MR signal. Signal intensity from tumour tissue is similar with CSF in T2 mode, which is why it looks like cyst in this regimen
Fig. 15.107a–d Multiple neurinomas. Sagittal T1-weighted imag-
nal cord with compression the latter. Postenhanced images (c,d) of cervical and lumbar spine visualise two neoplasms with similar CE patterns. There is local bone excavation to the L2 vertebral body
ing (a) and T2-weighted imaging (b) demonstrate extramedullary tumour at the C3–C5 levels. Neurinoma is located ventrally to spi-
Spine and Spinal Cord Disorders
neurinomas show a hyperintense MR signal on T2-weighted images compared with the signal intensity registered from the spinal cord (Figs. 15.104–15.107). However, the visualisation of tumour becomes valuable because the tumour and CSF intensity signals are practically similar. Neurofibromas usually reveal a hypointense signal on T1- and T2-weighted images compared with the spinal cord signal (Fig. 15.108). The socalled target symptom occurs more often than in neurinomas and appeared as a more intense signal at the tumour periphery than in its central portion. Spinal root tumours are characterised by intense contrast accumulation on contrast-enhanced MRI in 100% cases. The character of contrast media distribution in tumour tissue depends on the tumour structure (solid or cystic types). In all
1161
cases, CE provides improved visualisation of the tumour size and extent, especially in cases of paravertebral tumour growth (Figs. 15.109–112). An additional fat-sat suppressing regimen provides better tumour visualisation on contrast-enhanced MRI (Figs. 15.113, 15.114). MRI without CE usually fails to reveal microneurinomas (5–10 mm) located in the cervical or thoracic spinal canal. High-resolution T2 MRI easily depicts small-size tumour nodes in the lumbar spine where there are many SAS present. CE in these cases helps to differentiate neurinomas from non-tumorous lesions (for instance, cavernomas) (Fig. 15.115). Hyperintense MR signal from SAS impedes visualisation of lumbar cystic neurinomas. Signal intensity from the tumour cystic part and from the CSF in SAS may be identical. Intravenous CE is considered the only
Fig. 15.108a–c Neurofibroma lumbar spine (a 13-year-old child). (X-ray film is presented in figure 15.98a.) MR T2-weighted imaging (a–c)
visualises a huge intraspinal canal tumour with extravertebral extension. There are multiple excavations of the lumbar vertebral bodies due to expansive tumour growth
Fig. 15.109a–e Neurinoma at C2–C3. MRI before (a,b) and after (c–e) CE reveals solid tumour of dumbbell shape following a spinal root. Tumour has a pronounced homogeneous CE
1162
Chapter 15
Fig. 15.110a–d Dumbbell neurinoma at T4–T5. MRI in coronal T2 (a), T1 before (b) and after (c,d) CE clearly demonstrates
the typical shape of this tumour. Tumour has extradural location with local compression of spinal cord. Axial postcontrast T1weighted imaging adds information about relationship between tumour, spinal cord, and lung tissue
Spine and Spinal Cord Disorders
1163
Fig. 15.111a–g Neurinoma at C2–C4. MRI in T2 (a,b) and T1 before (c) and after (d–f) CE reveals nodule of tumour with intense but heterogeneous accumulation of contrast medium. MRI clearly demonstrates intradural extramedullary location of neurinoma. On the ADC map, neurinoma has heterogeneous increase of ADC values compared with spinal cord (g)
1164
Chapter 15
Fig. 15.112a–c Neurinoma at C6–C7. MR T2 (a), T1 before (b) and after (c) CE shows extramedullary tumour with relatively homogeneous
CE. Tumour compresses a spinal cord. There is the widening of the premedullary subarachnoid space below the tumour, a characteristic feature of intradural extramedullary lesion
Fig. 15.113a–e Multiple neurinoma of lumbar spine. MRI in T2 (a), T1 before (b) and after (c–e) CE shows the multiple extramedullary lesions with central cystic component and peripheral CE patterns. Fat-sat technique is better in visualisation of tumour’s location and structure than routing T1-weighted imaging (e)
Spine and Spinal Cord Disorders
Fig. 15.114a–f Neurinoma at L1. Coronal T2-weighted image (a) shows the extramedullary lesion with hyperintense signal, which dislocates the conus medullaris. On fat-sat T1 technique, tumour has similar signal with spinal cord (b). T1-weighted imaging with CE (c)
1165
and fat-sat technique (d–f) after contrast injection demonstrates the shape and accumulation of contrast medium in tumour tissue. Tumour extends into neural foramen on the left
Fig. 15.115a,b Neurinoma at L4. MRI in T2
(a), T1 with CE (b) shows microneurinoma in the lumen spinal canal (arrow)
1166
Chapter 15 Fig. 15.116a,b Multiple neurinomas of lumbar spine. Sagittal MRI in T1 before (a) and after (b) CE reveals two extramedullary tumours at the L4–L5 level. The smallest tumour is 3 mm in diameter
Fig. 15.117a–c Neurinoma at
L2–L3. MRI in T1 (a), T2 (b), and T1 with CE (c) demonstrates extramedullary tumour, which occupies the spinal canal and compresses the conus medullaris. Tumour has intense and heterogeneous CE
Spine and Spinal Cord Disorders
1167
Fig. 15.118a–g Neurinoma at L3 (a 13-year-old child). MRI in T2 (a,b) and T1 (c,d) modes demonstrates extramedullary mass lesion with signal intensity quite similar with CSF in all sequences. The visualisation of tumour structure and shape is possible only after intravenous CE (e–g)
1168
Chapter 15
Fig. 15.119a–d von Recklinghausen’s disease. Multiple neurinomas cervical spinal cord (an 8-year-old child). MRI before (a,b) and after
(c,d) CE demonstrates multiple extramedullary lesions precisely. Tumour has intense and heterogeneous contrast accumulation
method allowing reliable visualisation of cystic neurinomas in the spinal canal lumen (Figs. 15.116–15.118). One of the most typical features of spinal roots tumours is their ability to form multiple nodes of intra-and paravertebral locations, which is more often observed in children with type I and type II neurofibromatosis (von Recklinghausen’s disease) (Khong et al. 2003) (Figs. 15.119–122). When a tumour rises from the intercostals nerve, its single nodes may be seen in the paravertebral region. Neurofibromas are histologically more frequent in these cases. Their clinical signs mainly depend on the size of the tumour and compression of the organs situated in close proximity to the spine, like lungs, in the thoracic spine, kidney, and aorta, and in the lumbar spine (Figs. 15.123, 15.124). In rare cases, extended tumour growth may lead to bone changes better visualised on CT examination (Fig. 15.125). Introduction of new pulse sequences has greatly improved the role of MRI in preoperative planning, thus allowing virtually “entering” the spinal canal and assessing the correlations between the tumour and spinal cord or the tumour and spinal roots (Fig. 15.126). Differentiated diagnoses should be applied to meningiomas, meningocele, sequestered disk herniation, inflammatory radicular diseases (polyneuropathy), subarachnoid metastases, and lipomas. Meningioma is a benign, slowly growing tumour of primary intradural localisation, but may have extra-or extra–intradural locations. According to general statistic data, it is reported as 25–45% of all spinal cord neoplasms. Meningiomas are rare in children. The incidence of spinal meningiomas in children is 2–3%; quite often, atypical radiographic manifestations may be present. Most commonly, meningiomas are localised in the thoracic spinal canal, closely and widely attached to the dura mater.
The majority of meningiomas has an oblong form and unlike neurinomas, may occupy any segment of the spinal canal. They have a typical solid structure. Small calcifications can be detected in the meningioma tissue. Patients with this type of tumour are older than those with neurinomas (mean age over 50; female predominance is marked in 80%) of cases (Boisserie-Lacroix et al. 1987; Nadiri 2000). Neurological symptoms are caused by progression of spinal cord and dorsal roots compression. Spondylograms reveal spinal canal calcifications very rarely. Small-size meningiomas are visualised on myelograms as zones of filling defect of spinal cord SAS. Displacement and compression of the spinal cord are clearly seen. The tumour causing total SAS compression has typical manifestations on myelograms, and only one of the tumour contours is usually revealed. CT myelography is reported to be most sensitive for visualising contrast media in SAS of the spinal cord. CT myelography is efficient in demonstrating tumour contours, due to the ability of contrast media to encircle a neoplasm, even in “totally” occluded SAS (Fig. 15.127). On CT, meningioma shows a subtle hyperdensive features to paravertebral muscles, and after CE it is usually characterised by a homogeneous contrast accumulation. CT is superior to other imaging modalities in demonstrating hyperostosis and calcifications in meningioma’s stroma (Figs. 15.128, 15.129). Spiral 3D CT scanning provides virtual imaging of the spine and spinal neoplasms in patients with calcified tumours (Fig. 15.130). CT scanning is considered an obligatory component of primary diagnosis of extramedullary tumours for patients with suspected pathological bone destructions (Fig. 15.131). Meningiomas, like a neurinoma, show an isointense T1weighted signal to the spinal cord tissue, which in the majority of cases can be differentiated from a hypointense signal registered from the surrounding CSF.
Spine and Spinal Cord Disorders
1169
Fig. 15.120a–i von Recklinghausen’s disease type II. MRI of brain and spine reveals multiple extra-axial and extramedullary neurinomas,
which are better visualised after CE (a–i)
1170
Chapter 15 Fig. 15.121a–f Recklinghausen’s disease type II. Multiple neurinomas cervical spinal cord. MRI in T2 (a,b) and T1 modes after CE (c–f) demonstrates multiple intramedullary, intradural– extramedullary, and extravertebral tumours
Spine and Spinal Cord Disorders
Fig. 15.122a–f von Recklinghausen’s disease. Multiple neurinomas on the cervical spinal cord. MRI in T2 (a), T1 (b), T2* (c)
and T1 with CE (d–f) shows the multiple extravertebral lesions following the spinal roots in projection brachial plexus
1171
1172
Chapter 15
Fig. 15.123a–f Neurofibroma at L1–L2. MRI in T2 (a,b), T1 before (c) and after (d–f) CE reveals a large nodule of tumour located extravertebrally at level L1–L2 neural foramen. The latter is enlarged. Tumour has mixed signal intensity and heterogeneous CE
Spine and Spinal Cord Disorders
1173 Fig. 15.124a–f Neurofibroma at T6–T8. MRI in T2 (a) T1 before (b) and after (c–f) CE demonstrates a huge paravertebral tumour with hypointense signal from solid component on T2-weighted imaging. Tumour has heterogeneous CE and tendency to extend into neural foramen; there is compression of the surrounding lung tissue
1174
Fig. 15.125a–i Dumbbell neurinoma at T10–T11. Axial CT (a–c) images show a large-size tumour with intraspinal and extravertebral components. There is huge bone erosion with peripheral cortical
Chapter 15
sclerosis associated with tumour. MRI in T2 (d), T1 before (e,f) and after (g–i) CE demonstrates location of the tumour and character of CE
Spine and Spinal Cord Disorders
1175
Fig. 15.126a–d Neurinoma at T10. MR myelography (a) and T1 CE (b,c) images show the dumbbell neurinoma with heterogeneous CE. Tumour dislocates spinal cord laterally. Virtual endoscopy (d) allows a view of spinal canal structures (and the tumour) from inside
Fig. 15.127a–c Meningioma at T1–T2. Axial CT myelograms (a–c) demonstrate the mass lesion (arrow) located ventrally to the spinal cord.
The intrathecal contrast medium clearly outlines the tumour and spinal cord. The latter is compressed and dislocated posteriorly
1176
Chapter 15
Fig. 15.128a–c Meningioma at T1. Axial CT (a), sagittal
(b) and coronal (c) reformations visualise the totally calcified mass lesion
Fig. 15.129a–c Partially calcified meningioma at T2–T3.
MRI in T2 (a) and T1 after CE (b) demonstrates a small size meningioma located posteriorly to spinal cord. The attachment of meningioma to posterior spinal canal wall is well defined. Axial CT (c) shows the calcification in a tumour tissue
Spine and Spinal Cord Disorders
Fig. 15.130a–d Calcified meningioma at C1–C2. Axial CT (a) image and coronal CT reformation (b) visualise calcified mass lesion with wide attachment to lateral canal wall. There is small soft tissue component of meningioma in upper pole of the tumour. 3D reconstruction (c,d) with cutting bone structure visualises inside of vertebral canal
1177
1178
Fig. 15.131a–i Benign meningioma of sacrum (a 17-year-old pa-
tient). Axial CT (a,b), sagittal (c) and coronal (d,e) reformations demonstrate the huge bone destruction of sacrum with soft tissue tumour mass filling the caudal part of spinal canal with extraverte-
Chapter 15
bral extension. 3D reconstructions (f,g) show the size of bone destruction. On MRI with using myelography (h) and T2 (i) modes the tumour has atypical for meningioma MR appearance
Spine and Spinal Cord Disorders
1179
Fig. 15.132a–c Meningioma at C4–C5. MR T2 (a) and T1 (b,c) images show extramedullary laterally situated lesion with spinal cord compression. Tumour has hypointense signal on T2-weighted imaging (possibly due to calcification)
Diagnosis of tumours localised in the upper thoracic spinal cord can be complicated due to the extremely narrow size of the spinal canal in this place. Diagnosis is especially difficult for patients with lateral spinal deformations and marked agerelated degenerative changes of the spine and intervertebral disks (Fig. 15.132). The majority of meningiomas show T2weighted signal intensity similar by to that of the spinal cord tissue. Meningioma stroma shows a hypointense signal and thus is differentiated from a hyperintense CSF signal. However, a number of meningiomas, like intracranial tumours, demonstrate a subtle hyperintense signal on T2-weighted images (Figs. 15.133, 15.134). While calcifications are well visualised on CT, partially calcified meningiomas are better detected on
high-resolution T2 and T2* MRI, showing a hypointense signal (Fig. 15.135). As an exception, atypical forms of meningiomas may occur (Fig. 15.136; see Fig. 15.131). MRI with CE provides increased identification accuracy and thus improved diagnosis of meningiomas. The accumulation of contrast is of an intense and homogeneous character. In a number of cases, high-resolution MRI allows depicting the place of tumour attachment to the dura mater (Figs. 15.137–15.140). CE is extremely useful for demonstrating tumour recurrence in the delayed postoperative period as well as diagnosing multiple meningiomas accompanied by meningotheliomatosis or manifestations of van Recklinghausen’s disease (Fig. 15.141).
Fig. 15.133a–c Meningioma at T1–T2. MRI in T2 (a) and T1 (b) modes demonstrates round extramedullary lesion that has slightly hyperintense signal in all sequences. Coronal T2-weighted imaging (c) adds the information about spinal cord compression
1180
Chapter 15
Fig. 15.134a–c Meningioma at T10–T11. MR T2-weighted imaging (a) and T1-weighted imaging (b,c) reveal extramedullary tumour with
slightly hyperintense signal in all sequences
Fig. 15.135a–c Partially calcified meningioma at C3–C4. MRI in T2 (a,b) and T1 (c) demonstrates intramedullary tumour with hypointense central part (calcification). Spinal cord is dislocated and compressed due tumour
Spine and Spinal Cord Disorders
1181
Fig. 15.136a–c Xanthomatous meningioma at C1–C4. MRI in T2 (a), T1 (b,c) modes demonstrates extradural mass lesion with high signal intensity on T2 and hypointense MR signal on T1-weighted imaging. Spinal cord is compressed and covered by the tumour
Fig. 15.137a–c Meningioma at T7. MRI in T2 (a), T1 before (b) and after (c) CE shows the round tumour situated behind to spinal cord.
Tumour has intense and homogeneous CE
1182
Chapter 15
Fig. 15.138a–d Meningioma at T1–T2. MRI in T2, T1 before (b) and after CE (c,d) visualises extramedullary located tumour with clearly defined attachment on anterior lateral spinal canal wall. There is adjacent dura matter enhancement (arrow)
Fig. 15.139a–f Meningioma at C2–C3. MRI before (a–c) and after (d–f) CE reveals extramedullary tumour with homogeneous structure and enhancement. The accumulation of contrast medium in adjacent dura matter is visible on enhanced MRI
Spine and Spinal Cord Disorders
1183
Fig. 15.140a–f Meningioma at T2–T3. MRI in T2 (a), T1 before (b) and after (c–f) CE reveals extramedullary mass lesion with homogeneous
CE and well defined attachment to the posterior lateral spinal canal wall
In general, MRI differentiates two main types of extramedullary tumours—neurinomas and meningiomas—by the following signs: 1. Location: posterior-lateral localisation is most typical for neurinomas while a posterior spinal canal location is typical for meningiomas 2. Calcifications and hyperostosis are typical for meningiomas but not typical for neurinomas 3. Dumbbell-shaped tumour is typical for neurinomas and not typical for meningiomas 4. CE: more intense and homogeneous for meningiomas and less intense and heterogeneous for neurinomas 5. Intensified contrast accumulation by dura mater at the place of tumour attachment in meningiomas
15.6.2 Metastatic Tumours Mainly, these tumours are the metastatic dissemination of primary malignant brain tumours, often revealed in children (medulloblastomas, anaplastic EPs, germ cell tumours). In rare cases, metastatic EP, pineoblastomas, choroid plexus carcinomas, and glioblastomas are revealed. It is the so-called drop metastases (descending metastases), i.e. dissemination of the tumour cells via CSF in SAS of the spinal cord. These metastatic tumours are usually multiple. Intradural metastatic melanomas, lung and breast cancers, and leukemias can be revealed in adults (Formaglio et al. 1998; Gomori et al. 1998; Kallmes 1998; Collie et al. 1999; Singh et al. 200). As a rule, CT is poor at demonstrating change of density in the spinal canal. Contrast-enhanced MRI nowadays has totally replaced myelography and CT myelography in primary diagnosis of spinal cord metastatic tumours in children and
1184
Chapter 15
Fig. 15.141a–c Multiple meningiomas (meningotheliomatosis). MRI in T2 (a), T1 before (b) and after CE (c) in sagittal plane shows the
multiple extramedullary tumours with intense CE and compression of spinal cord at the level of its location
adults. Contrast-enhanced MRI allows the most adequate diagnosis of spinal cord tumours, small extramedullary and intradural tumour nodes. Standard MRI is poor at differentiating tumour nodes (which have an isointense signal on T1 to the spinal cord and a subtle hyperintense signal on T2 images and thus coincides with the CSF signal on T2 images) from the spinal cord. Tumour nodes become visible only by contrast enhanced MRI (Figs. 15.142–15.148). Moreover, tumours of the spinal cord arachnoids (carcinomatosis) are visualised on postcontrast MR images only (Fig. 15.149). Differential diagnosis is used for primary multiple tumours (hemangioblastomas, astrocytomas, ependymomas, meningiomas, neurinomas), purulent, or granulomatous meningitis, congenital hypertrophic polyradiculoneuropathies, arachnoiditides). Differential diagnosis is also made for single tumours, i.e. all types of extramedullary–intradural neoplasms. Our experience shows that it is extremely difficult at times to determine tumour histology at the preoperative stage (Fig. 15.150–15.152).
15.6.3 Dysembryonic Tumours Intradural dysembryonic tumours (lipomas, dermoid and epidermoid tumours, teratomas) make up 2% of all spinal cord tumours and are usually localised in the lumbar spine. The above-mentioned tumours have an embryonic origin, which is why they are often combined with other types of spinal cord anomalies (Awwad 1987). Lipomas in this group of tumours are characterised by most typical MR manifestations, namely, they have a hyperintense signal and lobular structure on T1 images and a hypointense signal on T2-weighted images (see Figs. 15.8–15.18). Patients with lipomas usually reveal other types of spinal anomalies (vertebral arches inconsolidation), diastematomyelia, and thickening of the filum terminale combined with spinal cord fixation, etc. (Fig. 15.153). Dermoid and epidermoid tumours, teratomas have a variety of MR features reflecting the character of tumour’s structure (Figs. 15.154–15.157). Evidence-based preoperative diagnosis is improved if the dorsal dermal sinus is present; it is usually observed in 30% of dermoid tumours. MRI is considered a method of choice because it is unique in visualising in vivo the inner structure of embryonic tumours. In addition, use of diffusion weighted MRI in diagnosis of epidermoid cysts makes preoperative assessment extremely effective (Fig. 15.158).
15.7 Extradural Tumours
Fig. 15.142a–c Intradural metastases of a germ cell tumour (a 13-year-old child). Sagittal T2 (a), T1 before (b) and after CE (c) demonstrate soft tissue lesion with occupation the lumen of lumbar spine. There are subarachnoid metastases around conus medullaris. Spreading of metastatic process is better estimated after CE
Extradural tumours compared with subdural ones are characterised by histological and biological variability, large size, predominance of malignant tumour types, and marked structural changes of spinal vertebrae. According to different authors’ opinion, extradural tumours make up 16–38% of all extramedullary tumours (Ross 2004). Extradural tumours in children make up about 50% of all extramedullary neoplasms.
Spine and Spinal Cord Disorders
1185
Fig. 15.143a–c Intradural metastases of medulloblastoma. T1-weighted imaging with CE reveals subarachnoid disseminations of tumour along spinal cord surface. There are postoperative changes in subtentorial region (after resection of medulloblastoma)
Fig. 15.144a–c Intradural metastases of neuroblastoma. Series of sagittal images before (a,b) and after CE (c) show the spreading tumour
nodes along subarachnoid space and around spinal cord. There is a hydromyelic cavity in the cervical spinal cord
1186
Fig. 15.145a–i Intradural metastases of medulloblastoma. Case 1.
MRI of brain (a) and spinal cord (b–f) reveals the multiple metastatic foci with spreading along subarachnoid space. The dissemina-
Chapter 15
tion is better visible after CE (a,d,e,f). Case 2. Contrast enhanced MRI (g–i) shows the metastatic subarachnoid dissemination as well intracranial as intravertebral location
Spine and Spinal Cord Disorders
1187
Fig. 15.146a–c Intradural metastases of pineal region germinoma. T2-weighted imaging (a) and T1-weighted imaging with CE (b,c) demonstrate the multiple small metastatic foci in subarachnoid space. They are better seen after CE
Fig. 15.147a–f Intradural intramedullary metastases of a lung carcinoma. T2-weighted imaging (a) and T1-weighted imaging before (b) and
after CE (c–f) reveals metastatic lesion in the cervical spinal cord with heterogeneous enhancement. The primary tumour is also visualised in the left lung on the coronal postcontrast MRI
1188
Chapter 15
Fig. 15.148a–d Intradural metastases of a breast cancer. T1-weighted imaging (a) before and after (b–d) demonstrate intradural lesion around spinal cord at the C3–C4
Fig. 15.149a,b Intradural carcinomatosis of spinal cord. Sagittal T1-weighted imaging before (a) and after (b) CE reveal metastatic dissemination around the entire spinal cord
Spine and Spinal Cord Disorders
1189
Fig. 15.150a–c Ependymoma at L4. T2-weighted imaging (a,b) and T1-weighted imaging (c) demonstrate extramedullary lesion at the cauda equina level
Fig. 15.151a–d Hemangiopericytoma at C7. T2-weighted imaging (a) and T1-weighted im-
aging before (b) and after CE (c,d) demonstrate the extramedullary tumour with imaging features, which are similar to neurinoma or meningioma
1190
Chapter 15
Fig. 15.152a–c Intradural metastasis at L4–L5. T2-
weighted imaging (a) and T1-weighted imaging before (b) and after (c) CE show extramedullary tumour, which is occupied the caudal part of lumbar spinal canal and has homogeneous structure and CE
Spine and Spinal Cord Disorders
1191
Fig. 15.153a–g Lipoma. Case 1. Intradural lipoma at lumbar spinal
canal (a 9-year-old child). T2-weighted imaging (a) and T1-weighted imaging (b,c) demonstrate a large mass lesion with typical for fat MR features. Case 2. Lipoma of filum terminale. CT (d,e) and MRI (f,g) reveal small lipoma with tethered spinal cord and spina bifida defect of the lumbar spine
1192
Chapter 15
Fig. 15.154a,b Epidermoid at L4–L5 (a 7-year-old child). Sagittal T2-weighted imaging (a) and T1-weighted imaging (b) show the large intradural mass located in the lumbar spinal canal. There are signs of tethered of spinal cord and spina bifida
Fig. 15.155a,b Teratoma at L2–L3. T1-weighted imaging (a) and T2-weighted imaging (b) demonstrate mass lesion with heterogeneous structure in the projection of lumbar spinal canal
Spine and Spinal Cord Disorders
Fig. 15.156a–d Dermoid at L2–L4 (a 5-year-old child). Ascending myelography (a) in lateral and anterior-posterior projection reveals a large nodular filling defect at T12–L3. Axial CT (b) demonstrates the mass lesion with multiple hyperdense foci (calcifications) on back-
1193
ground enlargement of vertebral canal. On MRI (0.02 T) in T1 (c) and T2 (d) modes there is a heterogeneous tumour. 1 tumour, 2 spinal cord, 3 subarachnoid space
Fig. 15.157a–d Teratoma at L2–L3. Series of sagittal T2-weighted imaging (a,b) demonstrates the tumour, which has a hyperintense MR
signal compare to spinal cord with peripheral rim of low signal intensity. Tumour has a hyperintense MR signal due to a presence of fat tissue on T1-weighted imaging (c,d)
1194
Chapter 15
Fig. 15.158a–f Epidermoid at L4–S1. Sagittal MRI shows the hyperintense lesion on T2-weighted imaging (a) and isointense on T1-weighted imaging (b). DWI in sagittal projection (c–e) reveals the mass lesion with hyperintense MR signal. Tumour has a heterogeneous colour (low ADC values) on ADC map (f)
Extradural tumours are classified into primary (arising from spine tissues) and secondary (metastatic tumours and tumours growing into the spinal canal from paravertebral tissues) tumours. The majority of extradural tumours are presented by metastatic and primary malignant neoplasms, with the former occurring three to four times more frequent than the latter (Paillas 1976; Ross 2004).
15.7.1 Primary Spinal Tumours These neoplasms are considerably rare in general population and extremely rare in children. According to the international tumour classification, primary tumours and tumoral processes comprise the following neoplasms (briefly):
1. Osteoid tumours: osteomas, osteoblastomas, osteosarcomas (osteogenic sarcomas, osteochondrosarcomas and other types of sarcomas) 2. Cartilaginous tumours: osteochondromas (osteocartilaginous exostosis, cartilaginous exostosis, enchondroma), chondromas, chondrosarcomas, chondroblastomas, chondromixoidal fibromas etc. 3. Giant cell tumours: osteoclastomas, malignant osteoclastomas 4. Miscellaneous osteoid tumours: Ewing’s sarcoma, ossified fibromas (osteofibromas) 5. Bone marrow tumours: plasmocytomas, multiple myelomas, lymphosarcomas, etc. 6. Vascular tumours: haemangiomas, hemangiopericytomas, hemangioendotheliomas, hemangiosarcomas (angiosarcomas), etc.
Spine and Spinal Cord Disorders
7. Other tissue-connecting tumours: fibromas, fibrosarcomas, lipomas, liposarcomas, etc. 8. Other tumours: chordomas, neurofibromas, etc. 9. Tumour-like processes: solitary osseous cysts, aneurysmal bone cysts, eosinophilic granulomas, fibrous dysplasia
15.7.2 Primary Malignant Tumours 15.7.2.1 Vertebral Osteosarcomas Vertebral osteosarcomas (osteogenic sarcomas) occur extremely rarely and make up 3% of all primary sarcomas (Shives 1986). It is the second frequently occurring type of primary bone-involving malignant tumours after multiple myelomas. The incidence peak of spinal osteosarcomas is usually marked at the age of 40, though in a large series of cases this type of tumours may occur any time from 8–80 years. Microscopic tumour analysis shows large-volume osteoid or newly formed bone tissues in the sarcomatous matrix.
Fig. 15.159a,b Osteosarcoma at L4. Sagittal MRI in T1 (a) and T2 (b) modes demonstrates the involvement of body L4. Tumour has the mixed hypo- and hyperintense MR signal. There is infiltration of epidural space with compression of the spinal canal
1195
Only 4% of all tumours are localised in vertebrae and sacrum. Posterior vertebral elements are primarily involved in 50% of cases. The typical feature is spinal canal invasion by a tumour. CT usually demonstrates tumour calcifications; matrix is visible on CT in bone window. A highly mineralised tumour reveals a hypointense MR signal in all scanning regimens on MRI (Ilaslan et al. 2004) (Fig. 15.159). Most often, the tumour has a heterogeneous structure on T1 and T2-weighted imaging (Fig. 15.160).
15.7.2.2 Chondrosarcoma Chondrosarcoma is described as a primary malignant tumour arising form the cartilaginous structures. It is observed in 20% of all malignant bone neoplasms. Spinal chondrosarcoma is rather rare and marked in 4% of cases. Spondylography usually reveals a bone defect zone with calcified matrix. In general, CT and MRI features of osteosarcomas and chondrosarcomas are usually similar. Most often, a heterogeneous tumour with an extravertebral soft tissue component is revealed (Fig. 15.161; Aoki et al. 1991). Radiological manifestations of all types of sarcomas are similar in overall. Spinal imaging demonstrates lytic lesions with pathological signs: cortical bone defect, invasion of the surrounding soft tissues, heterogeneous borders, and lesions of one or several vertebral bodies (Scott 1984: Dahlin and Unni 1986; Dorfman et al. 1998). Osteosarcoma may have an osteoplastic type of growth; however, it usually has a mixed structure: lytic and plastic components with invasion of vertebral bodies, their arches, and spinous processes. In the majority of cases, osteosarcoma reveals diffuse calcium deposits on a background of bone destruction. An osteosclerotic rim may also be formed. Chondrosarcomas on MRI demonstrate pathological changes of structure of vertebral body bones and surrounding tissues. Lytic changes have a hypointense MR signal on T1 images and a hyperintense signal on T2 images; osteosclerosis typically has a hypointense signal on T1 and T2-weighted images. Displacement of cortical bone by tumour’s tissue may be
Fig. 15.160a,b Osteosarcoma at C7–T2. Sagittal MRI in T1 (a) and T2 (b) modes demonstrates the involvement of body C7– T2, with gross paravertebral component and marked compression of spinal cord. Tumour has the mixed hypo- and hyperintense MR signal with haemorrhage foci
1196
Chapter 15
Fig. 15.161a–f Chondrosarcoma. Anterior–posterior X-ray film (a) and axial CT (b,c) demonstrate exostosis derived from lateral surface L5 body. Large soft tissue component with paravertebral location on the left is observed as well. Axial MRI in T2 (d), T1 before (e) and
after CE (f) reveal extravertebral tumour that has heterogeneous signal and CE. There is a dislocation psoas muscle laterally due to the tumour
identified as region of hyperintensity in vertebral body surface. The dura mater is usually resistant to the infiltrative tumour growth and usually shows a hypointense signal line that separates the tumour and spinal canal structures. The latter is better visualised on T2-weighted images. Epidural infiltration of tumour cells is well demonstrated on T1-weighted images. The tumour tissue reveals a hypointense signal compared with epidural lipid tissues.
Spondylography is helpful in 50–70% of cases in demonstrating complete bone defect with amorphous calcifications. Paravertebral tumour growth is often marked. CT better demonstrate large-size bone defects and the inner structure of chordoma. Unlike CT, MRI is considered less informative in detecting bone destruction zones; however, it is useful for assessing the tumour extent in general and epidural tissue growth, in particular (Figs. 15.162, 15.163) (Murphy 1998). Slow but gradual growth of chordoma without marked clinical symptoms, if localised in the sacrum region, sometimes results in formation of giant-size tumours (Fig. 15.164).
15.7.2.3 Chordoma Chordoma arises from remnants of notochord, from which vertebrae and intervertebral disks are later formed. Chordomas make up 4% of all primary malignant bone tumours. They involve sacrum in 50% of cases, clivus in 35%, and vertebral bodies in 15–20% only. Children reveal chordomas extremely rarely.
15.7.2.4 Myeloma Myeloma is described as a malignant tumour characterised by diffuse multicentre bone marrow involvement. Myeloma is considered the most frequent malignant bone tumour; there
Spine and Spinal Cord Disorders
Fig. 15.162a–i Chordoma. Case 1. Chordoma at C7 (a 15-year-old
child). Axial CT (a) image show low-attenuated mass located on the left side of C7 vertebral body. There is local cortical bone destruction and small calcification in lateral part of the tumour. MRI in T2 (b), T1 before (c,d) and after (e,f) CE clearly depict extravertebral tumour
1197
with cystic components and heterogeneous CE. Case 2. Chordoma at S3–S4. MRI in T2 (g) and T1 with CE (h,i) demonstrates intraspinal and extravertebral tumour with hyperintense signal (on T2) and heterogeneous CE. There are multiple cysts which have hypointense signal on T1-weighted imaging
1198
Chapter 15
Fig. 15.163a–c Chordoma at C2. Series MRI in T2 (a,b) and T1 (c) modes visualise extradural mass lesion derived from posterior part body
C2. Tumour has hyperintense signal in T2-weighted imaging and hypointense signal on T1-weighted imaging. There is spinal cord compression
Fig. 15.164a–c Giant chordoma of the sacrum. MRI in T2 (a, c) and T1 (b) modes demonstrates extremely large mass lesion with destruction
of caudal parts of sacrum and paravertebral extension
is marked a male predominance (3–4 newly revealed melanomas per 100,000 annually). Mean age of patients ranges from 40 to 80 years, and myeloma is seldom found in the younger population. Pain syndrome caused by vertebral body pathologic compression in the thoracic and lumbar spine (68%) is reported the leading clinical sign. Diagnosis is based on bone marrow biopsy (Dahlin 1986; Solomon 1984). As myeloma invades the haematopoietic red bone marrow, its localisation in vertebral bodies is typical. MRI is considered the most informative imaging modality for demonstrating myeloma, especially in its early stage compared with CT, which is poor at differentiating myeloma from osteoporosis (Sugimura 1987; Libshitz 1992; Mahnken et al. 2002). Destructed vertebral body (or the whole vertebra) has a hypointense T1-weighted signal compared with healthy vertebral portions (Fig. 15.165). In some cases, focal infiltrations of the epidural space without relevant intravertebral changes may be found (Fig. 15.166). They have a hyperintense signal on T2-weighted images. Sagittal images are informative and
helpful in demonstrating the extent of spinal lesion as well as detecting epidural infiltration and spinal cord compression (if available) (Fig. 15.167, 168). MRI is good at depicting decreased diffuse signal intensity on T1-weighted images in the late disease stage from affected vertebrae.
15.7.2.5 Lymphogranulomatosis (Hodgkin’s Disease) Lymphogranulomatosis (Hodgkin’s disease) is described as a malignant tumour of the lymphoid tissues combined with lymphatic node and bone destruction. Incidence of bone involvement looks like: most commonly, spine is involved, followed by breastbone, pelvic bones, scapula, sacrum, etc. Lymphoid infiltration of the bone marrow results in pathological bone changes of two types, osteolysis and osteosclerosis, revealed on radiograms. Lymphogranulomatosis can be focal or diffuse. MRI manifestations of the disease reflect the character of
Spine and Spinal Cord Disorders
1199
Fig. 15.165a–d Myeloma. Sagittal MRI in T2 (a,b) and T1 (c,d) modes reveal involvement of left part body L1 with paravertebral component
on the left (arrow). Tumour has hypointense signal on T1-weighted imaging as compared with the signal of other vertebral bodies
Fig. 15.166a,b Myeloma. Sagittal T1weighted imaging (a) and T2-weighted imaging (b) demonstrates a focal infiltration of posterior epidural space at T1–T2 level. Hypointense signal between tumour and spinal cord is represented by dura matter. There is spinal cord compression
bone destruction. Osteolysis has a hypointense signal on T1weighted images and a hyperintense T2-weighted signal (Figs. 15.169, 15.170). Combined (mixed) character of the disease is manifested by heterogeneous MR signals in all regimens. MRI in the late stage of the disease reveals enlarged pockets of paravertebral lymphatic nodes (Fig. 15.171). Diffuse spine lesions in patients with blood diseases (leukaemia, myeloleukosis), and lymphomas are difficult to diagnose on spondylography (Pear 1974). In the majority of cases, CT has proved poor at differentiating normal bone structures from infiltrative bone tumours, with exception of the late stage of the disease (Porter 1986). MRI possibilities are different. On T1-weighted images, the pathologic lesion reveals itself as a zone of hypointense signal that replaces bright signal from normal bone marrow (Fig. 15.172). MR manifestations of the solitary lymphoma differ from those of leukaemia infiltrations. Vertebral bodies demonstrate focal zones of decreased signal intensity to the bone marrow. Infiltration of the epidural space with spinal cord compression is typical for lymphomas
(Fig. 15.173). In leukaemia, vertebral body bone marrow (hypointense T1 signal), epidural tissues (infiltration), and dura mater are also involved. Intradural or paravertebral tumour infiltration may also occur. In the terminal disease stage, one may see destruction of the vertebral body bone marrow, skull vault bones, and flat skeleton. All that may cause fracture of vertebral bodies and epidural tumour infiltration with dural compression (Fig. 15.174).
15.7.3 Primary Benign Tumours and Tumour-Like Lesions 15.7.3.1 Osteochondroma Though osteochondroma is one of the most frequently occurred bone tumours (35.8%; Twersky 1978), its spinal localisation ranges 3 from 7%. The tumour is mostly localised in posterior vertebral bodies invading spinous and transverse processes. Osteochondroma is most often revealed in the
1200
Chapter 15 Fig. 15.167a,b Multiple myeloma. Sagittal T1-weighted imaging (a,b) reveals multiple involvement of vertebral bodies and spinous processes of the lumbar spine. There is compression of spinal canal at L4–S1 levels due to infiltration of epidural space
Fig. 15.168a–d Multiple myeloma. Sagittal MRI in T2 (a), T1 (b), and
GRE (c) modes demonstrates a diffuse decrease of signal intensity from vertebral bodies of thoracic spine. There is focal infiltration of posterior epidural space at T10–T11 level with spinal cord compres-
sion. Sagittal postcontrast T1-weighted imaging (d) shows heterogeneous CE from affected vertebral bodies and accumulation of contrast agent into zone of focal infiltration
Fig. 15.169a,b Lymphogranulomatosis (Hodgkin’s disease). Sagittal T2-weighted imaging (a) and T1-weighted imaging (b) reveal diffusion signal changes from the body of T2. The T2 body has slightly hyperintense signal on T2- and hypointense signal on T1weighted imaging. There is no change in the T2 body shape
Spine and Spinal Cord Disorders
1201 Fig. 15.170a,b Lymphogranulomatosis. T1-weighted imaging (a) and T2-weighted imaging (b) show diffuse signal changes from thoracic and lumbar vertebral bodies. There is infiltration of posterior epidural space at T9–T10 levels with spinal cord compression
Fig. 15.171a,b Lymphogranulomatosis. On T1-weighted imaging in sagittal (a) and coronal (b) projections, infiltration and enlargement of paravertebral lymphatic nodes on background involvement of thoracic vertebral bodies are observed
Fig. 15.172a,b Lymphoma. T1-weighted imaging (a) and T2-weighted imaging (b) shows diffuse signal changes from lumbar vertebral bodies, which are slightly hyperintense on T2- and hypointense on T1-weighted imaging. There is a wide infiltration of anterior epidural space
Fig. 15.173a–c Multiple lymphoma. T2-weighted imaging (a) and T1-weighted imaging (b,c) reveal the dumbbell mass lesion at middle thoracic level, with extension into the vertebral canal and compression of spinal cord. Involved vertabrae have hypointense MR-signal on T1 (b)
1202
Fig. 15.174a–i Myeloleukosis. Axial CT in standard (a) and bone
window (b) shows multiple foci of bone destruction. MRI with CE in axial (c) and coronal (d) planes demonstrates the pathological thickening and enhancing of dura matter. The CE in calvarium bone
Chapter 15
foci are visualised as well. Sagittal T2 (e) and T1 (f,g) reveals diffuse changes of signal intensity from vertebral bodies. Some of the vertebral bodies have compressing form. Axial CT images at thoracic level (h,i) shows diffuse bone changes in vertebrae
Spine and Spinal Cord Disorders
1203
cervical spine, but it may develop in the thoracic and lumbar spine as well. It should be noted that three quarters of tumours are diagnosed in patients under 20. Tumour aetiology includes idiopathic tumour types, traumatic injury, and radiation. Osteochondroma is considered one of the most frequent radio-induced benign type of tumour with its postradiation incidence ranging from 6 to 24% (Taitz et al. 2004). X-ray examination usually demonstrates a “lesion on peduncle” or wide-base tumour spreading into cortical bones. Posterior parts of vertebral bodies give growth to this type of tumour (Fig. 15.175). CT is more specific in demonstrating the tumour extent, cartilaginous rim (or calcifications), and mass effect to the spinal canal (Figs. 15.176, 15.177). MRI usually reveals a heterogeneous tumour structure with a hyperintense MR signal from the cartilaginous component and a hypointense signal from calcified and osseous neoplasm portions. MRI unlike CT is capable of detecting spinal canal compression more clearly (Morikawa 1995; Murphey et al. 2001).
15.7.3.2 Osteoid Osteoma Osteoid osteoma comprises about 6% of all benign bone tumours. Most often, it involves lumbar spine (60%) and cervical spine (27%); it is localised in the vertebral arch in 75% of cases. The tumour size is usually 1–1.5 cm. Larger tumours are regarded as osteoblastomas. As a rule, spondylograms reveal a bone darkening with well-defined contours and a surrounding low attenuated zone. The surrounding bone tissues may reveal different expressions of sclerotic changes. CT shows a small-sized, round, hypodense intensity zone with or without calcified inclusions and peripheral sclerosis (Figs. 15.178,–15.180) (Raskas et al. 1992). MRI demonstrates a heterogeneous tumour structure. Calcifications in the neoplasm stroma and sclerosis of the adjacent
Fig. 15.177a–c Osteochondroma T1 (a 16-year-old child). Ascending myelography in anterior–posterior (a) and lateral (b) projections reveals the “stop-contrast” sign at the tumour level. c Axial CT my-
Fig. 15.175 Osteochondroma of the cervical spine. Anterior–posterior X-ray film demonstrates bone exostosis derived from transverse process of C6
Fig. 15.176 Osteochondroma L2. Axial CT reveals tumour on “pe-
duncle” of bone density with low-attenuated centre derived from transverse process of L2
elography demonstrates extradural tumour with hyperdense central part and hypodense periphery. Spinal cord is deviated laterally (arrow). Contrast medium in SAS outlines the spinal cord contours
1204
Fig. 15.178 Osteoid osteoma. Axial CT demonstrates small low-at-
tenuated lesion at S1 level with hyperdense central area calcification
Chapter 15
Fig. 15.179 Osteoid osteoma at T4. Axial CT demonstrates small hyperdense lesion in the left peduncle of T4. There are calcified central parts of the lesion and osteosclerotic changes around osteoma
Fig. 15.180a–c Osteoid osteoma at T9. Axial CT demonstrates typical features for osteoid-osteoma
bones look dark on T1 and T2 MR images, while non-calcified tumour portion on the contrary, looks bright on T2-weighted images (Radcliffe et al. 1998; Liu et al. 2003).
15.7.3.3 Osteoblastoma Osteoblastoma is a rare benign bone tumour that is reported as 1% of all primary bone neoplasms. Its incidence in spinal segments is 40–50% of all observations, though it may affect bony skeleton as well. The tumour is typically localised in posterior and lateral parts of vertebral bodies (Boriani 1992; Murphey et al. 1996; Biagini 2001). Spondylograms and axial CT usually demonstrate an expansive tumour growth with thinning of the surrounding cortical areas (Fig. 15.181). Spondylograms show a combination of a typical low-attenuated tumour with the ossified centre and moderate sclerosis of the adjacent bones. The tumour
contours are always clear. CT and MRI may additionally reveal the soft tissue paravertebral tumour component. The tumour usually has a hyperintense MR signal surrounded by a thin hypointense signal rim (thinned cortical bone portions) on T2-weighted imaging. The tumour is heterogeneous and consists of bone trabeculae, haemorrhages, and calcifications (Fig. 15.182). Osteoblastomas are typically enhanced tumours. 3D CT is particularly important for correct choosing a surgical approach to paravertebral tumours with bone components (Fig. 15.183).
15.7.3.4 Aneurysmal Bone Cyst Aneurysmal bone cyst is considered a tumoral bone lesion of unclear aetiology. It occurs in 2.5% of all primary bone tumours. The bone cyst is described as a balloon-type enlargement of bone cavities of the affected vertebrae. Bone cysts are
Spine and Spinal Cord Disorders
1205
Fig. 15.181a–f Osteoblastoma L3. Axial CT (a,b) shows soft tissue mass lesion in the posterior parts of L3 vertebra. There is compression of
spinal canal. MRI in T2 (c,d) and T1 (e,f) with CE demonstrates extradural tumour with heterogeneous MR signal and moderate CE
marked in 80% of children and young people (under 20 years of age). Vertebral body and its posterior portions are involved usually. Spondylograms reveal a limited bone defect zone surrounded by a new reactive bone tissues, which sometimes have an eggshell-like appearance (Fig. 15.184). A large-size bone cyst may cause vertebral body compression. CT and MRI additionally reveal the cyst’s fluid volume, with specification of general volume changes (Figs. 15.185–15.187).
15.7.3.5 Giant Cell Tumours Giant cell tumours (osteoblastoclastoma) make up approximately 5% of all primary bone tumours and 21% of all benign neoplasms (Schute 1993; Bertoni et al. 2003). Spinal localisation is marked in 3% of cases. They more often occur in adults (over 20) and are extremely rare in children.
Spondylograms demonstrate an expansive lytic vertebral body defect. Sclerotic reaction is rare. CT and MRI visualise a zone of bone destruction with a soft tissue component (rarely cystic component) (Fig. 15.188). MRI with CE reveals a heterogeneous and moderate contrast accumulation in tumour (Fig. 15.189).
15.7.3.6 Chondroma Chondroma belongs to a cartilaginous tumour group. Spinal localisation is very rare and makes up 0.8–5% of all skeletal tumours. It is localised in lateral and posterior part of vertebral bodies, often occurs in the sacral spine. Radiographic features are similar to those of osteochondroma. Combination of CT and MRI allows to more accurately define tumour extent, calcifications, tumour-related bone changes, and any soft tissue component. The tumour has a het-
1206
Fig. 15.182a–d Osteoblastoma at C6 (a 15-year-old child). Axial CT (a) shows a mixed osteolytic and osteoplastic
lesion involving lateroposterior parts of vertebra. There is spinal canal compression. MRI in T2 (b), T1 (c) and T2* (d) modes demonstrates a large extradural tumour with mixed hypo- and hyperintense signal
Chapter 15
Spine and Spinal Cord Disorders
1207
Fig. 15.183a–h Osteoblastoma C7. Axial CT (a,b), reformations (c,d) and 3D reconstructions (e,f) demonstrate tumour with bone density derived from the peduncle and transverse process of the affected vertebra. There is no soft tumour component. CTA with 3D reconstruction defines the relationship between tumour and neck vessels (g,h)
1208
Chapter 15 Fig. 15.184 Aneurismal bone cyst. Anteri-
or–posterior X-ray film shows the expansive and destructive lesion of the right part of vertebral body. There is thinning of cortical layer around the lesion
Fig. 15.185a–c Aneurismal bone cyst C2. Lateral X-ray film (a) show the expansive enlargement of spinous process C2. There is Kimmerle
malformation. Superselective DSA (b,c) demonstrates the moderate supplying of lesion from branches of cervical ascending artery
Fig. 15.186a–c Aneurismal bone cyst S2. Sagittal (a) and coronal (b) MRI in T2 and GRE (c) modes demonstrate cystic lesion within body S2 with “bulbing” of posterior surface
Spine and Spinal Cord Disorders
Fig. 15.187a–i Aneurismal bone cyst T11. Axial CT (a) and coronal (b) and sagittal (c) reformations show the osteolytic lesion affecting the posterior parts of vertebra. Sagittal MRI in T2 (d,e), T1 before (f) and after CE (g) demonstrate extradural tumour with heterogeneous
1209
structure and CE. There is spinal cord compression. Coronal (h) and axial (i) MR images add information about relationship between tumour and spinal cord
1210
Chapter 15
Fig. 15.188a–e Giant cell tumour of lumbar spine (a 13-year-old child). Series of sagittal MRI in T1 (a,b) and T2 (c,d) sequences reveal the large cystic tumour with destruction of L5 vertebra. Cystic and solid tumour components are well defined on axial T2-weighted imaging (e)
Spine and Spinal Cord Disorders
1211
Fig. 15.189a–g Giant cell tumour of thoracic spine. T2-weighted imaging (a) and T1-weighted imaging before (b) and after (c–f) CE demonstrate extradural tumour at the T3 level with homogeneous CE. There is spinal cord compression due to infiltration of epidural space. The bone destruction of vertebra is better visualised on CT images (g)
1212
Chapter 15
Fig. 15.190a–e Chondroma T6. MRI in T2 (a,b) and T1 (c,d) modes demonstrates osteolytic lesion with intraspinal and extravertebral components. Axial T2-weighted imaging (e) is better visualised a tumour location and extending
erogeneous structure on MRI and shows a hyperintense MR signal from the cartilaginous and cystic tumour components, and hypointense MR signal from calcified and ossified neoplasm portions. Unlike CT, MRI is more accurate in determining of compression of the spinal canal (Figs. 15.190, 15.191).
15.7.3.7 Haemangioma Vertebral haemangioma is described as a benign vascular tumour. Autopsy incidence ranges from 8.9 to 12.5%, while clinical incidence is much lower. In 66% of cases, the tumours are identified as solitary lesion, in 34% as multiple lesions. In the majority of cases thoracic spine is involved (60%), which is followed by lumbar (29%), and cervical or sacral segments (11%). Spondylograms reveal typical vertical crossing of the affected vertebral body (caused by trabecular thickening). Trabecular thickenings look like spotted zones on axial CT (Fig. 15.192); they are more apparent on thin-slice spiral CT reconstructions (Fig. 15.193). MRI is considered an extremely sensitive imaging modality in visualising haemangiomas.
The tumour usually has a hyperintense signal on T1- and T2weighted MRI (Pastushyn et al. 1998; Baudrez et al. 2001) (Fig. 15.194). According to some authors, a hyperintense signal is caused not by a haemorrhagic component but rather by lipid deposits in the lesion zone (Baudrez 2001; Bandiera et al. 2002). However, haemangiomas may also show a hypointense signal on T1-weighted images (Fig. 15.195). Sometimes haemangiomas may have an expansive growth reaching large sizes and invading all vertebra components, including vertebral arches, transverse and spinal processes with compressed spinal canal (Fig. 15.196). One can even observe infiltration of the epidural and paravertebral tissues (Figs. 15.197, 15.198).
15.7.4 Secondary Spinal Tumours Secondary spinal tumours include metastatic tumours and tumours, growing into the spinal canal from paravertebral tissues (neuroblastoma, ganglioneuroma, ganglioneuroblastoma, etc.). It should be noted that secondary metastatic tumours of the spine in children occur extremely rarely (Fig. 15.199).
Spine and Spinal Cord Disorders
1213
Fig. 15.191a–i Chondroma T8. Axial MRI in T2 (a–c) and T1 (d,e) sequences demonstrates a large paravertebral tumour with intraspinal canal component. Tumour has marked heterogeneous MR signal in all modes. Axial CT (f,g) and 3D reconstruction (h,i) better visualise spreading of bone changes
1214
Chapter 15
Fig. 15.192a–c Haemangioma. Variant of extending. Axial CT of different patients (a–c) demonstrates the involvement of vertebral body: a part of the body, b whole vertebral body, c whole elements of vertebra
Fig. 15.193a–f Haemangioma at L1. CT examination: axial image (a), coronal (b,c) and sagittal (d) reformations, and 3D reconstructions
(e,f) reveal the typical features of lesion
Spine and Spinal Cord Disorders
Fig. 15.194a–f Haemangioma at T4. MRI in T2 (a), T1 (b,c) modes shows hyperintense signal from affected body T4
vertebra. CT exam better visualises typical haemangioma features and involvement of vertebral elements
1215
1216
Chapter 15
Fig. 15.195a–e Haemangioma. Case 1. MRI in T2 (a) and T1 (b) modes demonstrates multiple thoracic vertebra haemangiomas. The lesions have hyperintense signal in all regimens. Case 2. Haemangioma at T8. MRI in T2 (c,d) and T1 (e) modes shows the haemangioma with hyperintense signal on T2 and hypointense signal on T1 images
Spine and Spinal Cord Disorders
1217
Fig. 15.196a–g Haemangioma at T9 with expansive growth (an 11-year-old child).
Ascending myelography (a) demonstrates the stop-contrast sign at the level of affected vertebra. Axial CT (b) and sagittal MRI in T1 (c) and T2 (d) sequences reveal osteolytic lesion with involvement of posterior vertebral elements. There is marked spinal cord compression due to infiltration of epidural space. The abundant blood supply from intracostal artery is well defined on DSA (e–g)
1218
Chapter 15
Fig. 15.197a–d Haemangioma at T5 with expansive growth. MRI in T2 (a) and T1 (b) modes reveals involvement of body and posterior epidural space at the T5 level vertebra. There is compression of spinal canal structures. Postcontrast axial (c) and sagittal (d) MRI demonstrates mild CE of the lesion
Fig. 15.198a–f Haemangioma T9–T10 with expansive growth. MRI in T2 (a–e) and T1 (f) shows the involvement of two vertebrae with large
paravertebral and intraspinal components. Spinal cord is covered and compressed due to lesion
Spine and Spinal Cord Disorders
1219 Fig. 15.199 Metastases of sarcoma in L5 and ilium. Axial
CT images with CE
Fig. 15.200 Neuroblastoma of lumbar
spine (a 7-year-old child). Axial CT (a,b) demonstrates a large paravertebral tumour extending into spinal canal through enlarged neural foramina (arrow)
15.7.4.1 Neuroblastoma Neuroblastoma is described as a tumour, arising from primitive cells called neuroblasts. Embryologically the latter participates in forming the medullary substance of the adrenal glands and paravertebral perilymphatic ganglia. That is why it is considered that the majority of all neuroblastomas (65%) develop from these very components. Most frequently, the tumour is diagnosed in children around the age of 10 years. According to statistics, the annual tumour incidence in the United States is 7–10 new cases per 1 million children. As the tumour has a tendency to spread via intervertebral foramen into the spinal canal, spondylograms show typical their enlargements. Additionally, vertebral arch erosion, vertebral body excavation, and enlargement of the spinal canal can be revealed. Axial CT (Figs. 15.200, 15.201) and especially coronal MRI are useful in visualising a typical “digital” multilevel expansion of a large-size paravertebral tumour component into the spinal canal (Figs. 15.202, 15.203). MRI is particularly good at demonstrating the invasion of epidural space and spinal cord compression. CT and MRI characteristics of neoplasms are closely related to intratumoral components (calcifications, haemorrhage onset, cysts) (Lonergan et al. 2002; Siegel et al. 2002) (Figs. 15. 204, 15.205). Sometimes tumours with prevailed paravertebral and not intravertebral tumour growth may occur. In this case,
the bulk of the tumour is located either in paravertebral zone (Fig. 15.206) or back of the spine soft tissue (Fig. 15.207).
15.7.4.2 Ganglioneuroma Ganglioneuroma is described as a benign tumour originally arising from ganglion cells (Lonergan et al. 2002). Ganglioneuroma and neuroblastoma do not differ on imaging, if only by a slower growth of the former (Fig. 15.208).
Fig. 15.201 Neuroblastoma of lumbar spine (a 12-year-old child). Axial CT demonstrates a large paravertebral hypodense tumour entering partially in spinal canal through neural foramina
1220
Chapter 15
Fig. 15.202a,b Neuroblastoma of lumbar spine (a 7-year-old child). MRI in T1 mode in sagittal (a) and coronal (b) projections demonstrates a large paravertebral tumour extending in spinal canal through neural foramen at multiple levels with cauda equina compression
Fig. 15.203a–f Neuroblastoma of thoracic and lumbar spine. MRI in T2 (a) and T1 before (b–d) and after CE (e,f) shows a large dumbbell
tumour with extravertebral and intraspinal canal components. Postcontrast images demonstrate homogeneous enhancing lesion
Spine and Spinal Cord Disorders
1221
Fig. 15.204a–e Neuroblastoma at C7–T1. Axial CT (a,b), sagittal reformation (c) and 3D reconstructions (d,e) reveal soft tissue mass lesion
that has intraspinal canal as well as extravertebral components. There are osteolytic changes of posterior vertebral elements. The osteosclerotic changes are seen in vertebral body of T1
1222
Fig. 15.205a–i Neuroblastoma L5–S1 (a 10-year-old child). MRI in T2 (a–c), T1 (d,e) modes reveals a large paravertebral intrapelvic mass lesion with destructive changes of S1 body with its compression. CT
Chapter 15
axial (f,g) images and sagittal (h) and coronal (i) reformations visualise the enlargement neural foramen of sacrum of the right, as well as tumour nodule
Spine and Spinal Cord Disorders
1223
Fig. 15.206a–c Neuroblastoma of lumbar spine. Series MRI in T2 (a), T1 before (b) and after (c) CE reveal the giant tumour’s paravertebral location covering vertebral bodies. The tumour extends through neural foramina in spinal canal. There is moderate CE of tumour tissue
Fig. 15.207a–f Neuroblastoma of lumbar spine with intraspinal metastases. Sagittal MRI in T2 (a), T1 before (b) and after CE (c–f) demonstrate enhanced lesion in the projection of spinous processes L2–L3 vertebrae with spreading into spinal canal
1224
Chapter 15
Fig. 15.208a–f Ganglioneuroma of thoracolumbar spine. Spiral CT in axial planes and multiple reformations shows the large extravertebral
tumour entering into spinal canal through two enlarged neural foramen. There is partial calcification of intravertebral component. There is bone erosion of posterior surface of L1 vertebra
15.7.4.3 Metastases Metastatic tumours are considered one of the most frequently occurring skeletal tumours, in general, and of the spinal tumours, in particular. These tumours include breast cancer, lung cancer, prostate cancer, malignant neoplasms of kidney, and the thyroid gland etc. (Fruhling 1986; Lemort 1986; Ross 2004). Metastases can be solitary or multiple. Spinal metastases are characterised by haematogenous dissemination. Tumour localisation depends on the blood supply in vertebral bodies and distribution of the red bone marrow, i.e. the place where the tumour usually metastasises (Kricun and Kricun 1985). First, the tumour occupies vertebral bodies, gradually involving vertebral arches and spinous processes. Beside that, an epidural tumour can metastasise either from the metastatic focus or paravertebral tumour or directly into the epidural space via the cortical bone of vertebral bodies. Thoracic spine is the most frequent place for metastases (68%) (Gilbert 1978).
Metastases cause compression and hence disturbed blood supply of the spinal cord, thus resulting in fast appearance of progressing clinical symptoms of spinal cord lesions. Radioscintigraphy is considered one of the simplest methods of screening for patients with suspected metastases. However, its insufficient specificity may result in false-positive results for patients with degenerative diseases, Padgett’s disease, and early-stage traumatic vertebral body fractures. Scintigraphy has proven to be not sensitive enough to evaluate myelomas. Recently, a more accurate imaging modality in diagnosis of metastatic lesions of various organs in general, and tumours of the spine, in particular, has become available: whole-body PET (Wahl 2001). Spondylography reveals a tumour in its terminal stage, when bone tissue lysis is markedly expressed. CT and spiral CT are considered more informative and specific imaging modalities in revealing osteolytic bone defects and demonstrating cortical vertebral body destruction with epidural or paravertebral involvement (Figs. 15.209, 15.210). Bone tissue
Spine and Spinal Cord Disorders
1225
Fig. 15.209a–f Cancer metastasis in lumbar spine. Axial CT with CE demonstrates a large heterogeneous tumour with wide bone destruc-
tion. There are necrotic areas in the central part of the tumour
Fig. 15.210a–c Cancer metastasis in T7. Axial CT demonstrates mixed character of bone changes in affected vertebra (mainly osteolytic component)
1226
lysis is more typical for lung cancer metastases. Reactive bone sclerosis is frequently revealed in patients with metastases from prostate gland neoplasms and lymphomas (Fig. 15.211). In some cases, one can simultaneously observe osteolytic and osteoplastic processes (Fig. 15.212). The intervertebral disk in close proximity to the metastatic tumour usually remains intact. Metastasis density is increased after intravenous CE, thus allowing better assessment of paravertebral and epidural tissue invasion. CTMG is necessary only for cases of spinal cord compression or suspected intradural metastases. MR features of vertebral body metastases are nonspecific. As a rule, such lesions are visualised as focal or total lesions of one or several vertebral bodies with surrounding soft tissue involvement. Tumour invasion results in T1 relaxation time lengthening compared with that of the lipid tissues, comprising the bone marrow, and thus reveals a hypointense signal inside the vertebral body on T1-weighted images (Fig. 15.213–15.215). These lesions demonstrate varied signal intensity on T2-weighted images.
Chapter 15
Predominance of the osteoplastic or osteolytic tumour component in the metastatic zone results in varied signal intensity. Osteolytic foci have lengthened T1 and T2 relaxation time. These tumours show hypointense signal predominance on T1-weighted images. They are best visualised on T2-weighted images; these tumours reveal a hyperintense MR signal (Figs. 15.216, 15.217). Dense bone structure formation in the osteoplastic zone results in decreased T1-and T2-weighted signal intensity (Fig. 15.218). However, metastases have a heterogeneous structure and show heterogeneous signal intensity from the lesion zone. MRI is particularly useful in detecting tumour localisation and extent in paravertebral and epidural structures with simultaneous visualisation of the condition of the spinal cord. When using CE, one should keep in mind, that contrastaccumulating metastases become brighter on T1-weighted images. However, intact bone marrow already possesses a hyperintense signal before use of CE. In the end, the metastatic contrast-accumulating focus becomes as bright as well as un-
Fig. 15.211a–f Metastases of prostate cancer in thoracic spine. Axial CT reveals multiple osteoplastic metastatic foci in thoracic vertebra
bodies
Spine and Spinal Cord Disorders
1227
Fig. 15.212a–f Cancer metastases in lumbar spine. Multiple osteolytic and osteoplastic lesions are found in vertebrae and ilium bones on CT
affected bone marrow of vertebral body. The tumour borders are usually erased in these conditions. In addition to signal characteristics from vertebral body bone marrow, a radiologist should pay attention to change of form and size of the damaged vertebral body. GRE programmes have proved to be useful from the point of view of differentiated diagnosis in identifying metastatic foci in vertebral bodies. Metastases have a typical hyperintense MR signal on T1 GRE images (Figs. 15.219, 15.220). Solitary vertebral body damages or compressions are considered complicated from the diagnostic point of view, because compressed traumatic fractures need to be differentiated from “pathological” (tumour) compressions (Fig. 15.221) (Baker et al. 1990; Erly et al. 2006). In that case, MRI visualisation is superior to other imaging modalities. In MRI evaluation of the traumatic and “pathological” vertebral body compression, one should assess signal characteristics of the vertebral body bone marrow. Traumatic vertebral body fracture does not necessarily show change of signal intensity on T1- and T2-weighted images compared with the adjacent vertebral bodies. The ex-
ception is acute and subacute (3 months) vertebral body fractures, which show decreased focal or diffuse signal intensity on T1- and increased on T2-weighted images (Fig. 15.222). At that time, pathological changes in paravertebral tissues at the level of fracture can be additionally revealed. However, these changes have a tendency to disappear gradually, unlike tumour metastases, and MRI will reveal such a change. Multiprojectional MRI provides full information about the topography and anatomical location of the extradural tumour. Sagittal and coronal MRI views demonstrate tumour node location in the spinal canal; they allow defining close relationship existing between the tumour and spinal cord and the tumour and paravertebral structures (muscles, large blood vessels etc). MRI is particularly excellent at visualising paravertebral tumours penetrating into the spinal canal and effecting its substance (different types of sarcomas, neuroblastomas etc.). New vistas appear with a widespread use of spiral CT allowing examination of large anatomic spaces of the spine for a shortened period of time (Fig. 15.223).
1228
Fig. 15.213a–i Multiple metastases of breast cancer in thoracic and lumbar spine. Axial CT (a–c) reveals dumbbell tumour at T8 level. There is small bone destruction on transverse process. MRI in T2
Chapter 15
(d,f–i) and T1 (e) modes shows multilevel involvement of the spine. The extending of tumour into spinal canal is better seen on MRI than CT
Spine and Spinal Cord Disorders
1229
Fig. 15.214a–i Solitary metastasis in L3 vertebra. Axial CT (a–c) and MRI in T2 (d,e) and T1 (f–i) demonstrate osteoplastic lesion body L3
with large antevertebral soft tissue component. There is compression of the vertebral body
1230
Chapter 15
Fig. 15.215a–i Multiple metastases of lung cancer in brain and spine. Series of MRI (a–g) demonstrates the multiple involvements of verte-
bral bodies. They are better seen in T1 mode. Axial CT (h–j) visualise osteolytic lesions. k,l see next page
Spine and Spinal Cord Disorders
1231
Fig. 15.215j–l (continued) Intracranial metastases are defined on brain MRI with CE (k,l)
Fig. 15.216a,b Multiple metastases of lung cancer in the spine. Sagittal T1-weighted imaging (a) and T2-weighted imaging (b) demonstrates multiple metastases foci in vertebral bodies. They have hypointense signal on T1- and hyperintense signal on T2-weighted imaging
Fig. 15.217a,b Metastasis in T4. T1-weighted imaging (a) and T2-weighted imaging (b) reveal osteolytic lesion with infiltration of epidural space and compression of spinal canal. The lesion has hypointense signal on T1- and hyperintense signal on T2-weighted imaging
1232
Chapter 15
Fig. 15.218a,b Metastasis of lung cancer at T3. MRI in T1 (a) and T2 (b) modes reveals a mixed character bone changes with osteolytic and
osteoplastic components. There is infiltration of epidural and paravertebral spaces. Tumour compress the spinal cord
Fig. 15.219a–c Multiple metastases of lung cancer in spine. MRI in T2 (a) and GRE (b,c) modes demonstrates a multiple involvement of
vertebrae, which are better seen in gradient echo sequence
Spine and Spinal Cord Disorders
1233
Fig. 15.220a–i Solitary metastasis in the T1 body. MRI in T2 (a,b), T1 (c,d,h) and GRE (e) modes define involvement of vertebral body with changing of it shape and paravertebral extension. Soft tissue masses are better visualised after CE (f,g,i)
1234
Chapter 15
Fig. 15.221a–f Multiple metastases in T11 and L5. MRI of thoracic and lumbar spine reveals the pathological compression of T11, L5 vertebrae due to metastatic bone destruction
Fig. 15.222a,b Traumatic compression of T12 body. MRI in T1 (a) and T2 (b) modes demonstrates changing of vertebral body shape and signal intensity (the increase on T2-weighted imaging). There is no spinal cord compression
Spine and Spinal Cord Disorders
Fig. 15.223a–i Multiple metastases in the spine. Axial CT (a–c), coronal reformation (d) and 3D reconstruction (e,f) demonstrates multiple osteolytic metastases in thoracic spine and ribs. Sagittal (g) and
1235
coronal (h) T2-weighted imaging show the mixed character of signal intensity changes from intra- and extravertebral components. Metastases have the increased diffusion parameters on ADC map (i)
1236
15.7.5 Vascular Spinal Cord Malformations According to the international classification, vascular spinal cord malformations are divided into arteriovenous malformations (AVM), cavernous angiomas, venous angiomas and telangiectasias.
15.7.5.1 Arteriovenous Malformations
Chapter 15
• Anatomic principles and specific blood supply: retromed-
ullary, anterior spinal, intramedullary and extramedullary AVM (Djindjian 1976) • Angiographic signs: dural arteriovenous fistula, intradural and extradural AVM (Koenig et al. 1989) • Anatomic topography and angiographic hemodynamic signs: a group of pathologic vessels with the drained vein, a glomus of small-loop vessels; large-size AVM with large supplying arteries and drained veins, direct arteriovenous shunting (Skorometz et al. 1998; Tissen 2006)
AVM are described as the most frequent spinal cord vascular pathology; according to general data, they make up 60% of all spinal cord vascular malformations. Incidence of spinal cord AVM makes up 4–5% of all pathologic mass lesions of the spinal canal. AVM may occur at any age; however, in the majority of cases it is revealed in young people. AVM was first reported by O. Hebold in 1885 when he described in detail acute symptoms of haematomyelia and transverse lesions of the spinal cord in a girl. According to the Burdenko Neurosurgical Institute’s experience, AVM was revealed in 25% of patients under 16 of the 200 patients who underwent endovascular treatment, thus proving a high frequency rate of AVM in children (Tissen 2006). Spinal cord AVM is predominantly localised in the thoracic and cervical spine; two thirds of patients primarily reveal SAH combined with a signs of spinal cord involvement. At present, there are several classification systems of spinal cord AVM based on:
The guiding principle in diagnosis of spinal cord AVM is selective spinal angiography, which is useful in revealing afferent and efferent vessels of malformation (Fig. 15.224). However, it is an invasive and complicated technique from the point of view of technical performance. That is why it is used only in large specialised clinical centres and mostly at the final stage of treatment to assess blood supply of AVM for their further embolisation. Previously, myelography was used as a method of visualisation of AVM. However, with the widespread use of MRI it is not used much. Nowadays, MRI is considered the main imaging modality for primary diagnosis of vascular spinal cord AVM. At the same time, MRI visualisation of spinal cord AVM is a complicated task. Visualisation of an AVM and evaluation of the AVM–spinal cord relationships depend on MRI resolution abilities. High-field MRI is most effective and provides excellent results (Fig. 15.225). Pathological AVM vessels, lo-
Fig. 15.224a–d Thoracic spinal cord arteriovenous malformation (AVM). MRI in T2 mode (a,b) demonstrates pathological tortuous multiple vessels at cauda equina level in SAS which have a low in-
tense MR signal on T2-weighted imaging due flow–void effect. DSA (c,d) shows AVM and afferent vessel, which is coming from radicular artery
Spine and Spinal Cord Disorders
1237
Fig. 15.225a–c Thoracic spinal cord arteriovenous malformation. T2-weighted imaging in sagittal (a) and coronal (b) projections reveals a
multiple small vessels of AVM in SAS at T9–T11 levels with typical flow–void effect. There is an ischaemic zone into spinal cord (in T2 mode). AVM is not visualised on T1-weighted imaging (c)
cated in the SAS of the spinal cord, show flow–void signal on T1 and T2 images, caused by fast blood flow in the enlarged blood vessels (Figs. 15.226, 15.227). T2-weighted images are most informative. Hypointense signal intensity zones of a characteristic twisted, serpentine-like form can be revealed on MRI. The assessment of AVM on T1-weighted imaging is a difficult task because hypointense signal registered from CSF in the spinal cord SAS complicates the visualisation pathological vessels (Fig. 15.228). MRI is considered highly informative in assessing the AVM location towards the transverse spinal cord diameter. It is clearly seen on axial or coronal images (Fig. 15.229). In addition, MRI is particularly good at visualising the AVM-associated changes in the spinal cord: haematomyelia, myelomalacia, oedema, cyst formation, and atrophy (Figs. 15.230, 15.231). Use of dynamic MRI during endovasal AVM exclusion has proved to be useful in evaluating the condition of AVM vessels. Thrombosed AVM vessels show a bright signal on T1 images due to methaemoglobin formation in the clot (Fig. 15.232). A new approach in noninvasive demonstration of spinal cord AVM is the use of MRA. Several methods can be used simultaneously for obtaining MR angiograms. 2D TOF sequences with and without MR signal suppression by the arterial blood can be used for large-size AVM, predominantly located in the cervical spine. This technique is useful in demonstrating large arteries of the neck and possible blood supply sources of AVM (Fig. 15.233). Additional intravenous CE makes diagnosis of AVM more reliable. AVM vessels become apparent on contrast-enhances MRA (Fig. 15.234). Bolus contrast–enhanced MRA has proved to be most informative in visualisation the feeding arteries of cervical AVM (Fig. 15.235). Contrast enhanced 3D TOF sequences with further postprocessing at the working station are preferred for the diagnosis AVM localised in the thoracic spinal cord (Figs. 15.236, 15.237).
15.7.5.2 Cavernous Angioma Cavernous angioma (CA) rarely occurs in the spinal cord substance in comparison with its intracranial localisation. Clinical signs of the disease are presented by symptoms of intramedullary–subarachnoid haemorrhage, as in AVM. MRI reveals typical features that are similar to intracranial CA localisation. However, only high-field MRI with surface coils is capable to identify a typical haemosiderin rim around CA (Fig. 15.238). T2* MRI is considered more sensitive for patients in a chronic haemorrhage stage (Figs. 15.239, 15.240). Subacute haemorrhage shows a hyperintense MR signal on T1 and T2 images; large-size hematomas may conceal the real size of CA volume (Figs. 15.241, 15.242) .
15.7.5.3 Inflammatory Processes 15.7.5.3.1 Transverse Myelitis Transverse myelitis is characterised by fast development of clinical symptoms of spinal cord involvement. The disease is typical for the young patients. The basic cause of the disease is virus infection. In the acute stage, thickening of the spinal cord can be observed with typical hyperintense T2 signal in MRI. MRI in the terminal stage reveals the descending of spinal cord atrophy (Fig. 15.243).
15.7.5.3.2 Arachnoiditis Arachnoiditis is described as an inflammatory process in the spinal cord arachnoid that can develop after traumatic spinal injuries, meningitis (purulent or tuberculosis), and subarachnoid haemorrhages. It may be the result of surgical
1238
Chapter 15
Fig. 15.226a–d Intramedullary arteriovenous malformation (a 9-year-old child). DSA (a)
reveals the giant thoracic spinal cord AVM. Series of MRI in T2 (b) and T1 (c,d) modes demonstrate AVM, which has a balloon-shaped enlarged vessels with their partial thrombosis (hyperintense signal on T1-weighted imaging). Coronal T1-weighted imaging (d) shows enlarged intercostal artery on the left (arrow)
Fig. 15.227a–c Arteriovenous malformation (a 9-year-old child). T2-weighted imaging images in sagittal (a) and coronal (b) projections re-
veal the pathological vascular structures at the cauda equina level. The signal intensity of vessels is similar to a signal of CSF on T1-weighted imaging (c)
Spine and Spinal Cord Disorders
1239
Fig. 15.228a–c Thoracic spinal cord arteriovenous malformation. Sagittal and coronal images in T2 (a,b) and T1 (c) modes show pathological enlarged vessels in SAS of spinal cord. AVM is better visualised on T2-weighted imaging
Fig. 15.229a–f Thoracic spinal cord arteriovenous malformation. MRI in T2 (a–e) and T1 (f) modes reveals pathological enlarged vessels
of AVM in SAS spinal cord. Pathological vessels are better visualised on T2-weighted imaging. Relationship between AVM and spinal cord could be better estimated on axial images
1240
Chapter 15 Fig. 15.230 Thoracic spinal cord arte-
riovenous malformation (a 70-year-old patient). Sagittal T2-weighted imaging demonstrates pathological enlarged vessels of AVM with typical flow–void effect posteriorly of spinal cord. There is ischaemic oedema of intramedullary location appearing as a hyperintense spreading area on T2-weighted imaging
Fig. 15.231a–f Cervical spinal cord arteriovenous malformation. T1-weighted imaging (a–d) and T2-weighted imaging (e, f) show the microAVM at the C3–C4 level, with signs of acute and subacute haemorrhages
Spine and Spinal Cord Disorders
1241 Fig. 15.232a–d Cauda equina AVM (the state after endovascular embolisation). Series of MRI in T2 (a) and T1 (b–d) modes demonstrate a pathological AVM’s vessels with signs of their thromboses (hyperintense MR signal on T1-weighted imaging)
1242
Fig. 15.233a–f Cervical spinal cord AVM. Series of MRI in T1 (a) and T2 (b,c) modes reveal intramedul-
lary AVM. There are an ischaemic area and haematomyelic focus into the spinal cord (hyperintense MR signal on T2-weighted imaging). 2D TOF MRA shows afferent AVM vessels from left vertebral artery and anterior spinal cord artery (d–f)
Chapter 15
Spine and Spinal Cord Disorders
Fig. 15.234a–f Thoracic spinal cord arteriovenous malformation. T2-weighted imaging (a,b,f) and T1-weighted imag-
ing images before CE (c) reveal a pathological vessels of AVM located around the spinal cord. T1-weighted images after CE (d,e) demonstrate AVM vessels, which accumulated the contrast medium. Ischaemia of spinal cord is visible on T2-weighted imaging
1243
1244
Fig. 15.235a–f Cervical spinal cord arteriovenous malformation. AVM is well defined on sagittal T2-weighted imaging (a) and T1weighted imaging (b). 2D TOF MRA (c) reveals the supplying vessel
Chapter 15
derived from the right vertebral artery. The vascular tangle of AVM is better visualised on contrast enhanced MRA (d). 3D reconstructions of CE MRA add spatial information about AVM (e,f)
Spine and Spinal Cord Disorders
1245 Fig. 15.236a–d AVM of lower thoracic and lumbar spine. Sagittal T2-weighted imaging (a,b) reveals an enlarged vessels in SAS of lumbar spine. 3D TOF MRA with CE demonstrates pathological vessels as areas of contrast accumulation (c,d)
1246
Chapter 15
Fig. 15.237a–g AVM of conus medullaris. MRI in T2 (a) and T1 (b,c) modes demonstrates a widespread AVM with compact vascular glomus at the conus medullaris level. 3D TOF MRA (d,e) with CE shows a relationship between AVM and spinal cord. Pathological vessels are better visualised on MIP reconstructions (f,g)
Spine and Spinal Cord Disorders
1247
Fig. 15.238a–e Conus medullaris cavernous angioma. T2-weighted imaging (a,b) and T1-weighted imaging (c–e) show a small size cavernous angioma at T11–T12 level with typical hypointense haemosiderin rim in all sequences (arrow). There is no CE into angioma (d,e)
Fig. 15.239a–c Cervical spinal cord cavernous angioma. MRI in T2 (a) and T1 (b) modes demonstrates a small size cavernous angioma at the C5–C6 level with typical hypointense rim in T2 mode. The signs of old haemorrhage are visualised, which could be better observed behind of lesion on T2*-weighted imaging (c)
1248
Chapter 15
Fig. 15.240a–c Cervical spinal cord cavernous angioma. T2-weighted imaging (a) and T1-weighted imaging (b) reveal the cavernous angioma at C3–C5 level with hypointense rim in T2 mode. The signs of subacute and old haemorrhages are visualised. Haemosiderin deposits could be better observed with T2*-weighted imaging (c)
Fig. 15.241a–c Thoracic spinal cord cavernous angioma. T2-weighted imaging (a,b) and T1-weighted imaging (c) demonstrate a small size
cavernous angioma with typical hypointense rim in T2 mode and local subacute haemorrhage (hyperintense MR signal on T1-weighted imaging [c])
Spine and Spinal Cord Disorders
1249
Fig. 15.242a–f Cervical spinal cord cavernous angioma. MRI in T2 (a) and T1 (b–f) modes show a small size cavernous angioma at C5–C6 level with caudally and dorsally located subacute haemorrhage (a hyperintense signal on T1-weighted imaging)
1250
Fig. 15.243 Consequences of transverse myelitis (a 9-year-old child). Sagittal T2-weighted imaging reveals descendant spinal cord atrophy below the T8 level
interventions also, injections into SAS of different medical and diagnostic drugs, etc. Infectious processes in subarachnoid and subdural spaces in children are usually proceded by meningitis. The inflammatory process results in arachnoid space desolation, cyst formation, and connective tissue consolidation. MR features of arachnoiditis are nonspecific. Development of commissures results in thickening and adhesions of cauda equine, better demonstrated on T1 images. Postoperative changes may cause deformation of spinal cord surface, change of its form, and dislocation within the spinal canal lumen. Postinflammatory arachnoiditis is characterised by SAS enlargements, and atrophic thinning of the spinal cord with its contours deformation, sometimes of a moderate character (Fig. 15.244). Simultaneously, T2 images demonstrate atypical hypointense signal intensity zones in the SAS resulting from the CSF flow disturbance. The latter may be caused by commissures in the SAS, thus causing CSF circulation disturbances.
15.7.5.3.3 Spondylitis Diagnosis of infectious spinal processes is often complicated due to nonspecific clinical signs of the disease and its latent course. Radiographic visualisation of the early-stage spondylitis is practically impossible due to absence of pathological changes in vertebral body bones. Use of CT with subsequent MRI allows a more frequent diagnosis of the spinal infectious disease in its early stage.
Chapter 15
Infectious emboli usually get into vertebral tissues by haematogenous dissemination. However, they may disseminate from the adjacent infected paravertebral tissues (retropharyngeal abscess, infected dermal sinus, etc.) or directly from the penetrating injury or operational zones. First spondylographic or tomographic manifestations appear 2–8 weeks after first clinical symptoms occur. Radioscintigraphy and CT are considered the most sensitive imaging modalities in the early diagnosis of bone and soft tissue changes. Use of MRI has considerably improved the quality of diagnosis of inflammatory spinal processes, thus allowing simultaneous demonstration of pathological changes in vertebral bodies, paravertebral and epidural tissues in one of the chosen planes. Surface coils and high-field MR tomographs provide high-class quality of visualisation of pathologic changes in spine and the surrounding structures. MRI in patients with bacterial spondylitis and disk inflammations reveals lesions of the vertebral body and the intervertebral disk in form of a pathological hypointense signal on T1-weighted images. Differences that normally exist between disk tissues and vertebral bodies are not seen on these images. Vertebral body lesions look brighter compared with the adjacent ones on T2-weighted images. Disk tissue shows a typically hyperintense T2 signal. Sagittal views are useful for demonstrating the lesion extent, while axial and coronal views are excellent in evaluating the involved paravertebral tissues. Changes of vertebral bodies and intervertebral disks, revealed on MRI, reflect pathological processes typical for osteomyelitis (leukocyte infiltration with bone tissue lysis). MRI is capable of demonstrating pathological epidural tissue involvement accompanied by deformations and compressions of the dural space and its inner structures. Additional CE results in improved visualisation of the damaged vertebral bodies, especially their epidural spaces and paravertebral tissues. The affected vertebral body and intervertebral disk intensively accumulate the contrast media. Spiral CT usually demonstrates bone destructions of the vertebrae; inflammatory processes in epidural tissues are worse visualised on CT than on MRI (Figs. 15.245–15.248). Acute epidural abscess is a rare pathology. Haematogenous dissemination from distant sources is typical for this type of pathology (infections of skin, respiratory pathways, etc). Chronic epidural abscess is usually caused by direct inflammation disseminating from the vertebral body into the epidural space, with purulent infiltrate formation. On MRI, an abscess has a typical convex form. Its signal characteristics are nonspecific (Figs. 15.249, 15.250). Tuberculosis is considered one of the most frequent causes of development of spondylitis. It usually occurs in patients under 20 years of age. Vertebral body destruction is of a secondary character and most commonly caused by haematogenous infectious dissemination from the primarily infectious zone in lung. CT and MRI reveal fragmentation and destruction of one or two adjacent vertebral bodies combined with disk pathology and paravertebral abscesses. There are marked a hypointense signal on T1-weighted images and a hyperintense signal on T2-weighted images (Figs. 15.251–15.253).
Spine and Spinal Cord Disorders
Fig. 15.244a–c Arachnoiditis of spinal cord. The ascendant myelography (X-ray film) reveals stop-contrast sign at the T9 level (a). Sagittal T2-weighted imaging (b) and T1-weighted imaging (c) show the pathological deformation and dislocation of spinal cord. The
1251
contours of the latter are even. There is spread attachment of the spinal cord to the posterior wall of vertebral canal. Intramedullary hyperintense signal on T2-weighted imaging is also observed
1252
Fig. 15.245a–c T6–T8 spondylitis. T2-weighted imaging (a) and T1weighted imaging (b) demonstrate the involvement of bodies T6–T7 vertebrae with partially spreading to body T8. Intervertebral disks have a pathological changes at T6–T8 levels. There is an infiltration
Chapter 15
and small abscess into posterior epidural space. T1-weighted imaging after CE shows a diffuse contrast medium accumulation in affected vertebrae and abscess capsule (arrows)
Spine and Spinal Cord Disorders
1253
Fig. 15.246a–f L4–L5 spondylitis. Coronal (a, c) and sagittal (b) CT reformations reveal a wide destruction zone of cortical surfaces L4, L5
vertebrae. MR images in T2 mode (d–f) show the involvement of intervertebral disk and L4, L5 bodies (heterogeneous hyperintense MR signal)
1254
Chapter 15
Fig. 15.247a–f T4–T5 spondylitis. Series of T2-weighted images (a,b) and T1-weighted images without CE (c,d) demonstrate MR signal
changes from intervertebral disk and bodies of vertebrae at involvement thoracic level. g–i see next page
Spine and Spinal Cord Disorders
1255
Fig. 15.247g–i (continued) T4–T5 spondylitis. T1-weighted imaging images after CE (e–i) visualises an epidural space inflammatory
infiltration
Fig. 15.248a–f T7–T8 spondylitis. T2-weighted imaging (a–c) and T1-weighted imaging (d–f) show changes of signal intensity from vertebral bodies and intervertebral disk at affected level. There is a paravertebral abscess on the right
1256
Chapter 15 Fig. 15.249a,b L5–S1 spondylitis with epidural abscess. Sagittal MR images in T1 (a) and T2 (b) modes reveal pathological changes of vertebral bodies L5, S1, and intervertebral disk. There is an inflammatory infiltration of anterior epidural space. The epidural abscess with compression of spinal canal contents is visualised at L2–L4 level
Spine and Spinal Cord Disorders
Fig. 15.250a–f L5–S1 spondylitis. Series of MRI in T2 (a–d) and T1 with CE (e,f) modes demonstrate pathological signal changes of vertebral bodies and intervertebral disks. There is inflammatory infiltration of anterior epidural space with contrast agent accumulation in affected vertebral bodies and epidural space
1257
1258
Chapter 15
Fig. 15.251a–c L3–L4 tuberculosis spondylitis (a 16-year-old patient). T2-weighted imaging (a,b) and T1-weighted imaging (c,d) show a pathological signal changes from L3–L4 vertebral bodies and intervertebral disk. There are wide “cold” abscesses in the psoas muscle of both sides
Spine and Spinal Cord Disorders
1259 Fig. 15.252a,b Tuberculosis spondylitis. Sagittal T2-weighted imaging (a) and T1weighted imaging (b) demonstrate inflammatory destructions of L4–L5 vertebral bodies and intervertebral disk. The involvement is spreading to surrounded epidural and paravertebral spaces
Fig. 15.253a–c L1–L2 tuberculosis spondylitis. Series of MRI in T2 (a) and T1 (b,c) modes reveal a large paravertebral cold abscesses on background of inflammatory changes of vertebral bodies and intervertebral disk (arrows)
1260
15.7.5.3.4 Demyelinating Disorders of the Spinal Cord Acute disseminated encephalomyelitis is described as an acute autoimmune demyelination of the CNS resulting from previous viral (seldom mycoplasms or bacteria) infections or immunisation. Morphological examination reveals inflammations (perivascular lymphocytic infiltration) of different size in the brain and spinal cord. Overall, MRI picture of the spinal cord is nonspecific and hardly different from that of the demyelinating process, as MS. MRI shows single or multiple foci of the MR signal intensity, better visualised on T2 images. The spinal cord is usually thickened in the pathology zone. CE has usually of a variable character and mostly depends on the disease onset.
Fig. 15.254a–f Acute disseminated encephalomyelitis. Spinal cord
MR examination in T2 (a,b) and T1 with CE (с) reveals pathological foci in cervical and thoracic spinal cord, which have a hyperintense
Chapter 15
In our observations, pathological contrast accumulation zones were larger than in cases of multiple sclerosis (Fig. 15.254). MS is described as a demyelinating disease of the CNS characterised by multiple pathology, remittent course, variability of neurological symptoms and predominant prevalence in young population. However, it makes up 0.4–3% of all children observations of this disease. Mean age of children with clinical MS manifestations is 13 years. There is a generally accepted autoimmune theory of MS occurrence. A longterm latent infection, mostly of a viral origin, is considered the cause of MS development. The disease-provoking factors are spinal cord injury, pregnancy, emotional stress, allergic reactions, etc. Morphologically, MS is characterised by multiple
MR signal. Focus at C3–C4 level has a marked contrast medium accumulation. Brain MR examination shows typical features for this disease: multiple large plaques with CE and oedema (d–f)
Spine and Spinal Cord Disorders
zones of demyelination in the white and grey matter of the brain and spinal cord. If the spinal cord is involved, then pathological changes are usually marked in the cervical segment. One should keep in mind that absence of the accompanying brain lesion does not necessarily mean absence of MS. Usually, MRI reveals zones of pathological change of signal intensity (a hypointense signal on T1 images and a hyperintense signal on T2 images). Contrast media accumulation in the plaques is variable and mainly depends on the stage of pathology development. As a rule, spinal cord is thickened in the zone of “active” plaques (Figs. 15.255–15.258). In the advanced stage of the disease and during a long disease course, atrophic pathological changes of the spinal cord may develop(Fig. 15.259). It is known that MR manifestations of spinal cord lesions in children are somehow different from those of adults. Wide zone of MR signal changes as well as involvement of two to four spinal cord segments and presence of oedema are features more characteristic for the paediatric age group.
15.8 Traumatic Spine and Spinal Cord Injuries The objectives of any diagnosis of spinal injury are to reveal bone fractures, to determine vertebral body forms, to define displacement of vertebral bodies and their fragments, to determine type of accompanying ligamentous injuries and adja-
1261
cent tissues, to evaluate compression of the spinal canal and spinal cord, and to assess damage severity of the spinal cord and roots of spinal nerves. Conventional radiography has proved to be the guiding principle for primary diagnosis of acute spinal injury, especially when neurological symptoms are absent. CT, especially spiral CT, with further image processing at the working station is considered an effective imaging modality for identification of fractures, fractures with dislocations, or cortical fragment displacements as well as visualisation of acute intramedullary haemorrhages. CT is more useful than X-ray and MRI are for evaluating the above-mentioned damages. However, MRI is preferred for visualisation of spinal cord injuries. MRI in the acute spinal injury stage is of a limited use due to the lengthened examination time, frequent use of immobilising ferromagnetic equipment for patients with severe spinal injuries, and low sensitivity in diagnosis of acute hematomas and vertebral body damages. MRI is superior to other imaging modalities when dealing with subacute or chronic spinal injuries, due to its ability to use multiprojections with demonstration of extensive spine and spinal cord segments, to visualise craniovertebral and lumbar-thoracic segments, inaccessible for other methods, as well as to avoid the necessity to use CE. It is recommended to start investigation with large FOV T1-weighted images. They provide good anatomic visualisa-
Fig. 15.255a–c MS. T2-weighted imaging (a,b) and T1-weighted imaging (c) demonstrate an intramedullary focus of hyperintense signal on
T2 and hypointense signal on T1-weighted imaging
1262
Fig. 15.256a–c MS. Sagittal (a) T2- and T1-weighted imaging at C3 show the intramedullary focus, which has a hyperintense signal on T2- and hypointense signal on T1-weighted imaging. MR brain ex-
Chapter 15
amination reveals multiple pathological foci spreading through deep and periventricular white matter on T2-weighted (b) and FLAIR (c) imaging
Fig. 15.257a–f MS. Series of spinal cord MR examination in T2 (a,b) and T1 (c) modes demonstrate pathological foci not accumulating
contrast medium at C1–C3 and T1 levels. Brain MR examination (d–f) reveals a typical features for this disease (multiple foci). One of these foci accumulates the contrast agent (f)
Spine and Spinal Cord Disorders
1263
Fig. 15.258a–f MS. T2-weighted imaging (a,b,e) and T1-weighted imaging images before (c) and after (d,f) CE reveal the intramedullary
hyperintense focus (on T2-weighted imaging) at T5 level, which accumulated contrast medium (on T1-weighted imaging with CE). There is oedema around the pathological focus
1264
Chapter 15
Fig. 15.259a–c MS. Spinal cord (a,b) and brain (c) MR examination in T2 mode shows multiple pathological foci in white matter and asymmetrical brain atrophy
tion of the spine and spinal canal structures. T2-weighted images are preferred for assessing the narrowing of the spinal canal. T1 images are useful for demonstrating vertebral body changes, fragment displacements, traumatic disk herniation, listhesis, haemorrhages, and concomitant injuries or spinal cord deformations. Oedemas, myelomalacia, and necroses associated with spinal cord injury have hyperintense signal and are better detected on T2-weighted images. Subacute epidural or intramedullary haemorrhages show a hyperintense MR signal on T1- and T2-weighted images. MRI is particularly useful for assessing spinal injury sequelae. MRI without endolumbar CE is capable of visualising the spinal cord, change of its form and size, atrophic diffuse or focal changes, as well as hydromyelia cavities and CSF fistulas. MRI has significantly improved diagnosis of transverse tearing of the spinal cord. Though spinal injuries in children are not as frequent as in adults, they pose a potential risk for a child’s life. Anatomic and mechanical differences of spine in children and adults determine the character of traumatic spinal injury. As well, a normally developed child’s spine can be mistaken for a posttraumatic pathology. Knowledge about epidemiology, aetiology, and mechanisms of spinal injury in children as well as peculiarities of spine development in a child are of primary importance for the correct interpretation of neuroradiographic data. According to many reviews, incidence of spinal injury in children makes up 2–3% of all spinal injuries. In the younger ages, the incidence of spinal injury in boys and girls is practically similar; however, it is three times more frequent in adolescent boys than in girls. The spectrum of spinal injuries in children and adolescents slightly varies with the latter, revealing no difference from that of adults. Cervical spine injuries most often occur in a paediatric age group. There is a
close relationship between child’s age and localisation of the damaged cervical vertebra. The above-described anatomic and mechanical features of the forming spine directly correlate with the radiological evidence in paediatric spinal injury. In the early years, a child’s spine is inclined to injuries caused by distraction or rotation forces. In adults dislocations, subluxations, and damages of the spinal cord are more frequent than single fractures, if no radiologic pathological changes have been revealed. Traumatic cervical spinal cord injury is considered closely related to flexion (caused by thickening of the posterior longitudinal ligament) or extension (caused by thickening of interlaminar ligaments and ligamentum flavum) fractures. Traumatic thoracic spinal cord injury caused by destruction forces happens due to a minimal straining ability of the spinal cord in this site. This type of injuries is often combined with an ischaemic lesion of the spinal cord. The latter is caused by compression of the anterior spinal artery in flexion, by damage to the vertebral artery, in extension and rupture of small spinal cord arteries, and in overstretching. Clinical signs of spinal cord injury may occur in the delayed period of injury in the few hours (or even days) after injury.
15.8.1 Cervical Fractures Atlanto-occipital dislocation is described as a rare type of spinal injury, most commonly caused by vehicle or traffic accidents. Combination of sharp flexion or extension loading with dislocations or extensions (stretching), caused by acceleration or inhibition forces, results in craniocervical dislocations. Anterior craniocervical dislocation is considered the most typi-
Spine and Spinal Cord Disorders
cal type of spine injury. However, posterior dislocations may also occur; this type of injury is most typical for children due to anatomic paediatric characteristics, namely, weakness of ligaments, a relatively larger head compared with the spine, horizontal orientation of the atlanto-occipital junctions, and small size of occipital condyles. As a consequence, high mortality rate or marked residual neurological symptoms ensue if the child survives the injury. Radiologic diagnosis is based mainly on lateral spondylograms, which reveal change of width of the atlanto-occipital joint and change of length of the dens-basion line. Additional CT and MRI may reveal oedema and haemorrhage in the soft tissues as well as dislocation and/or compression of medulla oblongata with the following pathological features. C1 fractures. Posterior arch fracture of the C1 vertebra is most frequently revealed and is usually caused by overextension. The fracture line lies in the synchondrosis region more often. This type of fracture may be uni-or bilateral. The most characteristic feature of C1 fracture (axial compression results in the so-called Jefferson’s fracture) is lateral dislocation of the lateral mass of the atlas visible on “open-mouth” radiograms. CT can be additionally used to prove C1 fracture.
1265
C2 fractures (dens fractures). Dens fracture is considered the most typical traumatic cervical injury in children. It results from flexion fracture with the fracture line lying between the C2 vertebral body and dens. Dens remains intact due to its close longitudinal ligamentous connections with the anterior arch of the C1 vertebra. Radiographically C2 fractures are classified into three types depending on the fracture line position. In type I, fracture line lies in the dens apex (occurs rarely), in type II it lies in the dens-axis junction area (roughly two thirds of all fractures), and in type III it lies in the vertebral body (roughly a third of all axis fractures). CT and MRI may additionally provide information about dislocations, associated soft tissue injuries and spinal cord injuries (Figs. 15.260–15.263). Functional sagittal MRI is useful in specifying dislocation of the C2 body parts and compression of the spinal canal. However, a radiologist should be particularly cautious when performing MRI because there is a high risk of damage to the spinal cord. Fractures of the C2 arch are not frequent and are caused by overextension (Hangman’s fracture). Diagnosis is based on degree of the arch fragment displacement into the fracture zone.
Fig. 15.260a–c C2 vertebra odontoid process fracture (a 13-year-old child). Sagittal T2-weighted imaging (a) and T1-weighted imaging (b,c) demonstrate the fracture of C2 vertebra odontoid process, with its displacement posteriorly. The fracture is located above the synchondrosis line
1266
Chapter 15
Fig. 15.261a–c C2 vertebra odontoid process fracture with its displacement. Reformations of spiral CT data in sagittal (a,b) and coronal (c) projections are presented
Fig. 15.262 C2 vertebra odontoid process fracture. T2-weighted imaging (a) and T1-weighted imaging (b,c) demonstrate the C2 vertebra odontoid process fracture with displacement. The fracture line passes through the synchondrosis. The medulla oblongata is compressed
Fig. 15.263 C2 vertebra odontoid process fracture. MRI in GRE (a), T1 SE (b) and T2 (c) modes shows the fracture of the odontoid process
in base level without displacement
Spine and Spinal Cord Disorders
15.8.2 Low Cervical, Thoracic, and Lumbar Spine Fractures Fractures of low cervical spine level are usually observed in children of older age and teenagers. Spinal compressions (flexions) usually cause instable fracture of the anterior vertebral body portion. Bone fragments may be displaced in the spinal canal, thus causing its compression. Vertebral body compression in overextension is a rare event; it usually occurs in severe traumatic spinal injury. Traumatic thoracic spine injuries make up 25% of all spinal injuries. This type of injury usually results from falls or car accidents. Flexion fracture with typical compression of the anterior vertebral body portion is considered the basic mechanism of damage. Fractures can be single or multiple, but all of them are stable. In osteoporosis, vertebral body compression is usually multiple. As inferior-thoracic and superior-lumbar spine levels constantly experience great loadings and motions, the majority of compressed vertebral body fractures occur at these sites. They may be caused by a more severe traumatic impact and thus result in marked dislocations of bone fragments into the spinal canal with compression of the spinal cord and spinal cord
1267
roots. Spondylolisthesis is one of the sequelae of the lumbar spine and usually observed at the L4–L5 level. It is reasonable to perform complex examination of patients with severe spinal injuries, including CT and MRI. Spondylography (mainly used in the initial diagnostic stage), CT with further reformations (or 3D reconstructions) and MRI greatly contribute to the complex evaluation of the character of damage to the spine, paravertebral tissues and spinal cord (Figs. 15.264–15.272).
15.9 Degenerative Spinal Diseases 15.9.1 Ossification of the Intervertebral Disk Ossification of the intervertebral disk is described as a pathology, the cause of which is still unclear. Disturbed blood supply of nucleus pulposus is considered one of the causes. According to another theory, it may be caused by injury or infection. Clinical manifestations of the disease include pain syndrome and limited movement of the spine. A rise in body temperature and increased blood leucocytes may be also observed.
Fig. 15.264a–f Traumatic fracture of body C5 vertebra with dislocation. CT (a,b) and MRI (c–f) reveal a fracture of body C5 with the fragment’s dislocation anteriorly. The posttraumatic myelomalacia into cervical spinal cord is well defined
1268
Chapter 15
Fig. 15.265a–c Traumatic fracture of body C7 vertebra with Urban’s wedge. MRI in T2 (a) and T1 (b,c) modes reveal a fracture of body C7
with clinoid deformation of vertebral body and posterior fragment dislocation. There is compression of the spinal cord
Fig. 15.266a–c Traumatic fracture of body C5 vertebra. MRI in sagittal (a,b) and coronal (c) projections demonstrates the fracture of body C5 without displacement of bone fragments. There is the traumatic myelomalacia into cervical spinal cord
Spine and Spinal Cord Disorders
1269
Fig. 15.267a–c Traumatic fracture of body L1 vertebra. Spiral CT with reformatted images in axial (a), sagittal (b) and coronal (c) projec-
tions shows the fracture of body L1 with dislocation of bone fragments posteriorly. The compression of spinal canal lumen is observed. There is vacuum phenomenon within fracture area at L1–L2 level also
Fig. 15.268a–c Multifragmental fracture of body T10 vertebra. CT with reformatted images shows the fracture body of vertebra with bone fragment dislocation anteriorly and laterally
Fig. 15.269a–c Traumatic fracture of body of the T10 vertebra. 3D reconstructions of spiral CT data demonstrate the abilities of postpro-
cessing in the definition of fracture type and bone fragments dislocation
1270
Chapter 15
Fig. 15.270a–c Traumatic fracture of body L3 vertebra. T2-weighted imaging (a,b) and T1-weighted imaging (c) reveal an uneven decrease in height of vertebra’s body and changes of signal intensity from it (subacute phase)
Fig. 15.271a–c Multiple fractures of bodies T12 and L2 vertebrae due to fall from a great height
Spine and Spinal Cord Disorders
1271
Fig. 15.272a–c Fracture of body T4 on the background of osteoporosis. CT reformation in sagittal projection (a) and MRI in T2 (b) and
T1 (c) modes show the compression of body T4. Patient has diffuse density changes of vertebral bodies which are visualised on CT and T1weighted imaging (osteoporosis)
However, asymptomatic cases may also occur. Spondylograms are excellent for revealing intervertebral ossifications, while CT is particularly useful in diagnosing vertebral disk state. MRI is considered less informative; however, it may better than other imaging modalities depict pathological changes in the adjacent intervertebral disks.
15.9.2 Degenerative Changes of the Intervertebral Disk It is well known that with age intervertebral disks suffer irreversible pathological changes, manifested by change of signal intensity on T2-weighted images. High water content (hydrogen protons) in the intervertebral disk tissue gradually decreases, leading to reduced MR signal intensity. Increase of degenerative changes in intervertebral disks results in decreased MR signal intensity. Degenerative changes in intervertebral disks are considerably rare in children and usually are caused by traumatic spine injury. Pathologic heredity may also be present. Degenerative changes in the disk tissue reveal a reduced T2 signal intensity on MRI and change of the disk form (Figs. 15.273, 15.274). These degenerative changes are frequent in teenagers who participate in active sports (weight lifting, bodybuilding, gymnastics, and ballet) and suffer from chronic spine injuries. Very often intervertebral disk changes are accompanied by changes in the adjacent vertebral bodies thus resulting in Schmorl hernia formation. Similar degenerative processes may occur in marked spinal sclerosis, Scheuerman’s disease and other types of systemic osteochondropathies (Fig. 15.275).
15.9.3 Intervertebral Disk Herniation Neurological manifestation depends on the site of herniation, its size and location (posterior, posterior-lateral, lateral), state of the surrounding tissues and size of the spinal canal. Thus, small-size protrusions may show marked clinical signs like pain or radicular syndromes, while sometimes, clinical signs of a large-size herniation may be minimal. The following types of intervertebral disk protrusions are outline: • Disk protrusion with the asymmetric fibrous ring protruding outside ventral vertebral body and accompanied by degenerative changes of the disk’s tissue • Disk prolapse due to the fibrous ring thinning (without disruption), and nucleus pulposus protrudes outside the posterior border of vertebral body • Disk prolapse (or disk herniation), protrusion of nucleus pulposus outside the fibrous ring results from its disruption • Disk herniation and disk sequestration; disk fragment is protruded in the spinal canal lumen (Fig. 15.276) Progression of posterior or posterior-lateral disk herniation may lead to disruption of the posterior longitudinal ligaments and cause reactive thickening of the dura mater. Disk herniation is better seen on T2-weighted images, as well, a hyperintense MR signal from CSF in SAS allows definition of the boundaries of disk protrusion quite clearly (Figs. 15.277, 15.278). T1-weighted images are particularly useful for identifying spinal cord and spinal roots compression in the intervertebral lumen in the presence of a hy-
1272
Chapter 15
Fig. 15.273a,b Degenerative intervertebral disk disease. Sagittal T2weighted imaging (a) and T1-weighted imaging (b) reveal a deformation of upper and lower surfaces of vertebral bodies with Schmorl nodules. Intervertebral disks have a low intensity signal on T2-weighted imaging
Fig. 15.274a,b Degenerative intervertebral disk disease (a 12-year-old child). Sagittal T2-weighted imaging (a) and T1-weighted imaging (b) images show an uneven decrease in height of intervertebral disks and multiple Schmorl nodules. Also, there is a decrease of signal intensity from disk tissue
Spine and Spinal Cord Disorders
1273
Fig. 15.275a,b Degenerative intervertebral disk disease (a 14-year-old child). Sagittal T2-weighted imaging (a) and T1-weighted imaging (b) demonstrate a decrease in height of intervertebral disks and Schmorl nodules at the lower thoracic level
Fig. 15.276 Schema of various disk herniation types: A normal
disk, B disk protrusion with the asymmetric fibrous ring protruding outside ventral vertebral body and accompanied by degenerative changes of the disk’s tissue, C disk prolapse due to the fibrous ring thinning (without disruption), nucleus pulposus protrudes outside the posterior border of vertebral body, D disk prolapse (or disk herniation), protrusion of nucleus pulposus outside the fibrous ring results from its disruption, E disk herniation and disk sequestration; free disk fragment
1274
Chapter 15 Fig. 15.277a,b Disk herniation at L4–L5. T2-weighted imaging images in axial (a) and sagittal (b) projections reveal the posterior disk herniation with moderate compression of spinal canal lumen
Fig. 15.278 Disk herniation at L4–L5. Sagittal MRI in T2 mode shows a large diffuse posterior disk herniation with pronounced compression of spinal canal
perintense MR signal registered from epidural lipid tissues (Fig. 15.279, 15.280). T2-weighted images are very good at demonstrating external portions of the thinned fibrous ring (a hypointense signal) and protrusion of nucleus pulposus in patients with disk protrusions. Fibrous ring disruption (in cases of disk herniation) can be identified by a typical cessation of the hypointense signal zone around the protruded nucleus pulposus (Fig. 15.281). However, in some cases, it is difficult to differentiate disk protrusion from disk herniation because a hypointense signal from the fibrous ring coincides with a hypointense signal from the posterior longitudinal ligaments, thus prohibiting detection of fibrous ring destruction. In cases with sequestrations of disk, MRI is useful in diagnosing free disk fragments above and under the posterior longitudinal ligament and even in the epidural spaces located at a certain distance from the inter-
vertebral space: superiorly or inferiorly (Figs. 15.282, 15.283). Axial scanning is preferred for obtaining a fuller anatomic topography of transverse disk herniation. It helps to determine posterior, posterior-lateral, or lateral disk herniation and their relationship with spinal canal and intervertebral foramen.
15.9.4 Degenerative Changes of the Vertebral Body Degenerative intervertebral disk changes induce development of the accompanying degenerative processes in the adjacent vertebral bodies. They reveal change of signal intensity on T1and T2-weighted images. In one case, they show a hypointense signal on T1- and T2-weighted images and in another, conversely, hyperintense MR signal. In the former case, a hypointense MR signal in subcortical vertebrae may be explained by
Spine and Spinal Cord Disorders
1275 Fig. 15.279a,b Disk herniation at C3–C4. Sagittal T1-weighted imaging (a) and T2*weighted imaging (b) demonstrate a large posterior disk herniation with spinal cord compression. The degenerative changes of C4–C7 intervertebral disks are observed also
Fig. 15.280a,b Disk herniation at T6–T7. T1-weighted imaging (a) and T2-weighted imaging (b) in sagittal projection show the posterior disk herniation with marked spinal cord compression
1276
Chapter 15
Fig. 15.281 Disk herniation at L5–S1. Sagittal MR images in T2 mode reveal the posterior disk herniation with fibrous rim rupture (also dura mater probably) and free disk fragment formation
Fig. 15.282a,b Disk herniation (sequestered) at L5–S1. T1-weighted imaging images in sagittal and axial projections demonstrate a large posterior lateral disk herniation with sequestered fragment located into anterior epidural space at L5 body level
Fig. 15.283a–c Disk herniation at L5–S1 (sequestered). Sagittal and axial images show a large disk herniation with sequestered fragments
(a–c)
Spine and Spinal Cord Disorders
1277
Fig. 15.284a,b Disk herniation at L4–L5. Sagittal MR images in T2 (a) and T1 (b) modes demonstrate a large disk herniation with displacement of disk cephalad tissue from disk space. There are degenerative changes into L4, L5 vertebral bodies on T1weighted imaging
development of a sclerotic process and loss of the bone marrow lipid component, while in the latter, there is the lipid bone marrow component prevailing over sclerosis (Fig. 15.284).
15.9.5 Spinal Canal Stenosis The term spinal canal stenosis is used to describe spinal canal narrowing regarding its normal size. This is a systematic process resulting from simultaneous growth of the degenerative changes in intervertebral disks and facet joints, with further development of osteoarthritis and osteophytes. Most commonly, stenosis develops in the lumbar or cervical spine. Sagittal and axial T1-weighted images usually demonstrate compression of the dural sac and loss of epidural lipid tissues in the zone of narrowing. Thickening of ligamentum flavum and degenerative changes of interarticular surfaces of facet joints with preserved bone osteophytes are visible on MR tomograms. Hypertrophy of ligamentum flavum is caused by its chronic traumatic injury (Fig. 15.285). Spinal canal stenosis is better revealed on sagittal T2weighted images because better CSF visualisation is reached
in this regimen (Figs. 15.286, 15.287). Axial tomograms are useful for evaluating spinal canal narrowing and size of the spinal canal. However, CT has proved to be more helpful in providing information about change of bone structures and facet joints.
15.9.6 Bechterew’s Disease Bechterew’s disease (also known as Strümpell-Marie-Bechterew’s disease, idiopathic ankylosis spondyloarthritis, and ankylosis spondylitis) is described as an inflammatory disease of spine and joints. Genetic factors, particularly the HLA-B27 antigen, play an important role in the origin of the disease (Pederson et al. 2008). It is present in 90–95% of patients: in approximately 50% of first-degree relations, and only in 7–8% in the whole population (Coates et al. 2008). The first signs of disease most commonly occur in the younger population, with no gender predominance. However, Bechterew’s disease in females is less expressed and has a nonspecific disease course. Pathomorphological basis of the disease is inflammatory enthesopathy: inflammation of tendons, ligaments,
1278
Chapter 15
Fig. 15.285a,b Central spinal stenosis due to thickening of ligamentum flavum at L3–L5 levels. MRI in T2 (a) and T1 (b) sequences reveals a stenosis of spinal canal due to hypertrophy of ligamentum flavum and degenerative changes of intervertebral disks
Fig. 15.286a,b Stenosis of cervical spinal canal. Sagittal MRI in T2* (a) and T1 (b) modes reveals strongly pronounced degenerative changes of intervertebral disks and vertebral bodies with multiple disk herniations (diskosis). Subarachnoid spaces and spinal cord are compressed at disk herniations levels
Spine and Spinal Cord Disorders
1279 Fig. 15.287a,b Stenosis of cervical spinal canal. Sagittal MRI in T1 (a) and T2 (b) modes demonstrates strongly pronounced degenerative changes of intervertebral disks and vertebral bodies, with disk herniations at C3–C4 and C4–C5. Subarachnoid spaces and spinal cord are compressed at C3–C5 levels. There is a small focus of myelomalacia at the C5 level on T2-weighted imaging
fibrous portions of intervertebral disks, capsules of joints in bone-adjoined places, inflammations of bone tissues (osteitis), and synoviitis. Iliosacral joints and facet joints, fibrous intervertebral disks, and large extremity joints are mostly damaged. Spinal changes—spondyloarthritis—observed in Bechterew’s disease, can accompany other diseases: psoriatic arthritis, Reiter’s syndrome, etc. The guiding symptom of the disease is inflammation of iliosacral joints, sacroiliitis. In Bechterew’s disease the so-called beggar’s pose develops: marked kyphosis of the thoracic spine with a bent head and flexion of the knee joints, thus compensating upward transfer of the centre of gravity. The classic form of the disease is mainly characterised by spinal involvement. However, peripheral joints and other organs and systems may be also involved in the process. Eye lesions in the form of unilateral iriocyclitis is typical for the disease. A number of patients develop aortitis, resulting in the aorta valve insufficiency. The disease is complicated by amyloidosis, with dominating kidney pathology in 5–6% of cases. Sometimes, fibrosis of the superior lobe of the lung develops. X-ray examination has proved to be useful in diagnosis and differentiation of Bechterew’s disease. The most stable sign of the disease is sacroiliitis, revealed in the early stage. X-ray films demonstrate vague contours of iliosacral joints and subchondral osteosclerosis. Sacroiliitis is mostly bilateral and relatively asymmetrical. With time (some years after the disease onset), ankylosis of iliosacral joints develops. Radiographic changes in other spine structures are clearly observed much later after sacroiliitis has been formed. Osteitis is typical for this disease; it is described as a destructive bone process, predominantly involving anterior vertebral body edges. It re-
sults in change of form into that of an open square, usually revealed in the lumbar spine. Bone involvement can be observed in other spinal segments, thus causing localised pathological changes. Syndesmophytes develop simultaneously with osteites. They are described as ossified external portions of the fibrous intervertebral disks. They first occupy thoracolumbar and lumbosacral segments. X-ray exams identify them as linear, vertically pointed, thin bone bridges connecting vertebral body edges. Gradually, syndesmophytes involve other spinal segments (cervical spine, ranking last), and the spine looks like a bamboo stick on radiograms (typical and late symptom of Bechterew’s disease). Overall, CT confirms radiographically revealed pathological changes (Fig. 15.288). MRI is very poor at demonstrating affected bone or calcifications. Early-stage MRI demonstrates diffuse–focal multilevel changes of the MR signal from vertebral bodies, mainly from the vertebral arch and articular processes of the thoracic and lumbar spine (moderate hyperintense signal on T2 images and a hypointense signal on T1 images) (Fig. 15.289). In the late stage of the disease, ankylosis of the facet joints develops; it is visible on lateral X-ray film at the cervical level; ankylosis in other spine segments is visible on oblique views only. Ossification of the joint capsules, vertebral body osteoporosis, and ossification of intervertebral disks also are observed. Differentiated diagnosis is usually preformed for lumbar spine osteochondrosis accompanied by radicular syndrome. Forestier’s disease looks similar to Bechterew’s disease on Xray film, but is typical for elderly patients. It is characterised by ossification of the anterior longitudinal ligaments and absence of sacroiliitis.
1280
Chapter 15
Fig. 15.288a–c Bechterew’s disease. Spiral CT with sagittal reformations shows multiple syndesmophytes along the anterior spine surface
Spine and Spinal Cord Disorders
1281
Fig. 15.289a–f Bechterew’s disease. Series of MRI in T2 (a–c) and T1 (d–f) modes demonstrate multiple diffuse-focal MR signal changes from vertebrae (bodies, pedicles and articular processes) at the thoracic level
1282
Chapter 15
Refere n c e s Ahadov T, Panov V, Ihoff U (2000) Magnetic-resonance tomography of spine and spinal cord. Medicine, Moscow, p 748 (in Russian) Akeson P et al (1994) Radiological investigation of neurofibromatosis type 2. Neuroradiol 36:107–110 Aoki J et al (1991) MR enchondroma and chondrosarcoma: Rings and arcs of Gd-DTPA enhancement. J Comput Assist Tomogr 15:1011–1016 Aubin ML, Jardin C, Bar D et al (1979) Computerised tomography in 32 cases of intraspinal tumor. Neuroradiology 681–92 Awwad EE, Backer R (1987) The imaging of an intraspinal cervical dermoid tumor by MR, CT and sonography. Comput Radiol 11:169–173 Babchin IS (1962) [Chap. 1, Tumors of spinal cord.] In: Petrov NN, Kholdin SA (eds) [Malignant tumours, vol 3.] Medicine, Leningrad, pp 510–552 (in Russian) Baker L, Goodman S, Perkash I (1990) Benign versus pathologic compression fractures of vertebral bodies: assessment with conventional spin-echo, chemical-shift, and STIR MRI. Radiology 174:495–502 Ball W (1997) Pediatric neuroradiology. Lippincott-Raven, Philadelphia, p 789 Bandiera S et al (2002) Symptomatic vertebral haemangioma: the treatment of 23 cases and a review of literature. Chir Organi Mov 87:1–15
DeLaPaz R et al (1985) High field thin-slice surface coil MRI of spine and spinal cord. Science of MR in Medicine, 4th annual meeting, London, UK Djindjian M, Hurth M, Houdart R (1970) Angiography of the spinal cord. University Park Press, Baltimore Dorfman HD et al (1998) Bone tumours, 1st edn. Mosby, St. Louis, pp 353–440 Epstein F, Epstein N (1982) Intramedullary tumors of the spinal cord. Pediatric neurosurgery: surgery of the developing nervous system. Grune & Stratton, New York, pp 529–540 Erly, Oh E, Outwater E (2006) The utility of in-phase imaging in differentiating malignancy from acute benign compression fractures of spine. AJNR Am J Neuroradiol 27:1183–1188 Formaglio F et al (1998) Meningeal metastases: clinical aspects and diagnosis. Ital J Neurol Sci 19:133–149 Fruhling J (1986) Radiology of the spine: tumors. In: Jeanmart L (ed) Tumors. Springer, Berlin Heidelberg New York, pp 103–115 Gilbert R, Kim J, Posner J (1978) Epidural spinal cord compression from metastatic tumor: diagnosis and treatment. Ann Neurol 3:40–51 Gomori J et al (1998) Leptomeningeal metastases: evaluation by gadolinium enhanced spinal magnetic resonance imaging. J Neurooncol 36:55–60
Barkovich A (1996) Pediatric neuroradiology. Lippincott-Raven, Philadelphia, p 668
Grem J, Burgess J, Trump D (1985) Clinical features and natural history of intramedullary spinal cord metastases. Cancer 56:2305–2314
Barkovich A (2000) Pediatric neuroimaging, 3rd edn. Lippincott Williams & Wilkins, Philadelphia
Habirov FA (2003) [Clinical neurology of spine.] Methodical Textbooks, Kazan, Russia (In Russian)
Baudrez V et al (2001) Benign vertebral haemangioma: MR histological correlation. Skeletal Radiol 30:442–446
Haughton V, Williams A (1982) Computed tomography of the spine. Mosby, St. Louis
Biagini R et al (2001) Osteoid osteoma and osteoblastoma of the sacrum. Orthopedics 24:1061–1064
Huk W, Gademann G, Friedmann G (1990) Magnetic resonance imaging of central nervous system diseases. Springer, Berlin Heidelberg New York
Bluemke D, Wang H (1990) Primary spinal cord lymphoma: MR appearance. J Comput Assist Tomogr 14:812–814 Boisserie-Lacroix M, Kien P, Caille J (1987) Imaging of intradural extramedullary tumours: neurinomas and meningiomas. J Neuroradiol 14:66–81 Boriani S et al (1992) Osteoblastoma of the spine. Clin Ortho Rel Res 278:37–45 Brant-Zawadzki M, Norman D (1987) MRI of the central nervous system. Raven, New York Carsin M, Gandon Y (1987) Rolland MRI of the spinal cord: intramedullary tumours. J Neuroradiol 14:337–349 Coates LS et al (2008) Real life experience confirms sustained response to long-term biologics and switching in ankylosing spondylitis. Reumatology (Oxford) 47:897–900 Collie D et al (1999) Imaging features of leptomeningeal metastasis. Clin Radiol 54:765–771 Conti P et al (2004) Spinal neurinomas: retrospective analysis and long-term outcome of 179 consecutively operated cases and review of literature. Surg Neurol 61:34–43 Crasto et al (1997) MRI diagnosis of intramedullary metastases from extra-CNS tumors- Eur Radiol 7:732–736 Dahlin D, Unni K (1986) Bone tumours: general aspects and data on 8,542 cases, 4th edn. Thomas C. Thomas, Springfield, Ill.
Ilaslan H et al (2004) Primary vertebral osteosarcoma: imaging findings. Radiology 230:697–702 Jeanmart I (1986) Radiology of the spine: tumours. Springer, Berlin Heidelberg New York, pp 118 Kallmes D, Gray L, Glass J (1998) High-dose gadolinium-enhanced MRI for diagnosis of meningeal metastases. Neuroradiology 40:23–26 Khong PL et al (2003) MR imaging of spinal tumours in children with neurofibromatosis I. AJR Am J Radiol 180:413–417 Kleihues P, Sobin LH (2000) World Health Organization classification of tumors Cancer. 88:2887 Koenig E, Thron A, Schrader V (1989) Spinal arteriovenous malformations and fistulae: clinical, neuroradiological and neurophysiological findings. J Neurol 236:260–266 Koenig M et al (1989) Spinal arteriovenous malformations and fistulae: clinical, neuroradiological and neurophysiological findings. J Neurol 236:260–266 Kricun R, Kricun M (1994) (eds). MRI and CT of the spine. Case study approach. Raven, New York, p 392 Larson TC III, Houser OW, Onofrio BM, Piepgras DG (1987) Primary spinal melanoma. J Neurosurg 66:47-49
Spine and Spinal Cord Disorders Lemort M, Divano L, Jeanmart L (1986) Radiology of the spine: tumors. In: Jeanmart L (ed) Tumors. Springer, Berlin Heidelberg New York, pp 81–101 Levy W et al (1982) Spinal cord meningioma. J Neurosurg 57:804–812 Libzshitz H et al (1992) Multiple myeloma: Appearance at MR imaging. Radiology 182:833–837 Liu P et al (2003) Imaging of osteoid osteoma with dynamic gadolinium-enhanced MR imaging. Radiology 227:691–700 Lonergan G et al (2002) Neuroblastoma, ganglioneuroblastoma and ganglioneuroma: radiologic-pathologic correlation. Radiographics 22:911–934 Mahnken A et al (2002) Multidetector CT of the spine in multiple myeloma: comparison with MR imaging and radiography. AJR Am J Radiol 178:1429–1436 Manelfe C (1992) Imaging of the spine and spinal cord. Raven, New York, p 890 Mironov S, Morozov A, Belyaeva A et al (2004) X-ray diagnostics of the primary tumours and tumour-like disorders of spine. Medicine, Moscow, p 248 (in Russian) Miyasaka K, Akino M, Abe S, Isu T, Iwasaki Y, Abe H (1986) Computed tomography and magnetic resonance imaging of intramedullary spinal cord tumors. Acta Radiol 369:738–40 Modic M, Pavlicek W, Weinstein M (1984) MRI of intervertebral disk disease. Radiology 152:103–111 Modic M, Masaryk T (1988) Degenerative disk disease. In: Stark D, Bradley W (eds) Diagnostic radiology: categorical course in MRI. North American Tower Books, Oak Brook, Ill, pp 625–708 Modic M, Masaryk T, Roos J (1989) MRI of the spine. Year Book Medical, New York, p 870 Morikawa M et al (1995) Osteohondroma of the cervical spine: MR findings. Clin Imaging 19:275–278 Mortimer N, Hughes D, O’Byrne KJ (2001) Intramedullary spinal cord metastasis. Lancet Oncol 2:607 Murphey M et al (1996) Primary tumours of spine: Radiologicpathologic correlation. Radiographics 16:1131–1158 Murphey M et al (2000) Imaging of osteochondroma: variants and complications with radiologic-pathologic correlation. Radiographics 20:1407–1434 Murphy J et al (1998) CT and MRI appearances of thoracic chordoma. Eur Radiol 8:1677–1679 Naderi S (2000) Spinal meningiomas. Surg Neurol 54:95 Nikolsky VA (1947) [Primary intravertebral tumors. Clinics, pathology, surgery.] Feniks, Rostov-na-Donu, Russia (In Russian) Norman D, Brant-Zawadzki M (eds) (1987) The spine: MRI of the CNS. Raven Press, New York Paillas J, Alliez B, Pellet W (1976) Primary and secondary tumors of the spine. In: Vinken P, Bruin G (eds) Handbook of clinical neurology, vol 2, pt. 2. North-Holland, Amsterdam 19–54 Parizel P, Baleriaux D, Rodesch G (1989) Gd-DTPA enhanced MRI of spinal tumours. AJR Am J Radiol 152:1087–1096 Pastushyn A et al (1998) Vertebral haemangiomas: diagnosis, management. Natural history and clinicopathological correlates in 86 patients. Surg Neurol 50:535–547 Pear B (1974) Skeletal manifestations of the lymphomas and leukemias. Semin Roentgenol 9:229–240
1283 Pedersen OB et al (2008) Ankylosing spondylitis in Danish and Norwegian twins: occurrence and the relative importance of genetic vs. environmental effectors in disease causation. Scand J Rheumatol 37:120–1126 Porter B, Shields A, Olson D (1986) MRI of bone marrow disorders. Radiol Clin North Am 24:1131–1135 Post MJ (ed) (1984) CT of the spine. Williams & Wilkins, Baltimore, p 659–695 Radcliffe S et al (1998) Osteoid osteoma: the difficult diagnosis. Eur J Radiol 28:67–79 Rallmes D et al (1998) High dose gadolinium-enhanced MRI for diagnosis of meningeal metastases. Neuroradiology 40:23–26 Raskas D et al (1992) Osteoid osteoma and osteoblastoma of the spine. J Spinal Disord 5:204–211 Razdolsky I (1958) [Tumors of spinal cord and spine.] Foliant, Leningrad (In Russian) Ross J, Masaryk T, Modic M (1987) Postoperative cervical spine: MR assessment. J Comput Assist Tomogr 11:955–962 Scott G (1992) Neuroradiological diagnosis of spinal cord tumors. In: Harwood Nash DC, Pettersson H (eds) Neuroradiology. Mosby, St. Louis Shiff D et al (1996) Intramedullary spinal cord metastases: clinical features and treatment outcome. Neurology 47:906–912 Shives T, Dahlin D, Sim F (1986) Osteosarcoma of the spine. J. Bone Joint Surg 68:660–668 Shutte H et al (1993) Giant cell tumor in children and adolescents. Skeletal Radiol 22:173–176 Siegel M et al (2002) Staging of neuroblastoma at imaging: report of the radiology diagnostic oncology group. Radiology 223:168–175 Singh S et al (2002) MR imaging of leptomeningeal metastasis: comparison of three sequences. AJNR Am J Neuroradiol 23:817–821 Skorometz A, Tissen T, Panyushkin A, Skorometz T (1998) Vascular disorders of the spinal cord. SOTIS, St. Petersburg, p 526 (in Russian) Solero C et al (1989) Spinal meningiomas: Review of 174 operated cases. Neurosurgery 125:153–150 Solomon A, Rahamani R, Seligsohn U et al (1984) Multiple myeloma: early vertebral involvement assessed by computerised tomography. Skeletal Radiol 11:258–261 Stark D, Bradley W (1988) Magnetic resonance imaging. Mosby, St. Louis, p 1516 Sugimura K, Yamasaki K, Kitagaki H et al (1987) Magnetic resonance imaging of the spine-differentiation by T1 and T2 relaxation times. Nippon Igaku Hoshasen Gakkai Zasshi 47:714–21 Sze G, Krol G, Zimmerman R (1988) Intramedullary disease of the spine: diagnosis using Gd-DTPA-enhanced MRI. AJR Am J Radiol 151:1193–1204 Taitz J et al (2004) Osteochondroma after total body irradiation: an age-related complication. Pediatr Blood Cancer 42:225–229 Thijssen H, Keysen A, Hortink M et al (1979) Morphology of the cervical spinal cord on computed myelography. Neuroradiology 18:57–62 Tissen T (2006) [Endovascular treatment of arteriovenous malformations of the spinal cord.] Medicine, Moscow, 357 (in Russian)
1284
Chapter 15
Twersky J, Kassner E, Tenner M, et al (1975) Vertebral and costal osteochondromas causing spinal cord compression. Am J Roentgenol Radium Ther Nucl Med 124:124–128
Winkelman M et al (1987) Intramedullary spinal cord metastases. Diagnostic and therapeutic considerations. Arch Neurol 44:526–531
Twersky J et al (1975) Vertebral and costal osteochondromas causing spinal cord compression. Am J Roentgenol Radium Ther Nucl Med 124:124–128
Youmans J (1982) Neurological surgery. Saunders, Philadelphia
Valk J (1988) Gd-DTPA in MRI of spinal lesions. AJR Am J Radiol 150:1163–1168 Wahl R (2001) Current status of PET in breast cancer imaging, staging, and therapy. Semin Roentgenol 36:250–260 (review)
Woodruff J et al (2000) Schwannoma. In: Kleihues P, Cavanee W (eds), Tumours of the nervous system. IARC Press, Lyon, pp 176–184 Zimmerman R, Bilaniuk L (1988) Imaging of tumours of the spinal canal and cord. Radiol Clin North Am 26:965–1007
Subject Index
A abscess 8, 21, 179, 605, 612, 868, 898, 902, 904, 907, 913, 949, 952, 955, 957, 959, 961, 965, 969, 975 acute disseminated encephalomyelitis (ADEM) 700, 1033, 1058, 1063, 1064 ADEM. see Encephalomyelitis, acute disseminated adenoma, pituitary. see pituitary adenoma adrenoleukodystrophy 22, 1003, 1005, 1006, 1008, 1060, 1085, 1086 amyloid angiopathy 179, 197, 198, 1075, 1082, 1083, 1091 amyotrophic lateral sclerosis (ALS) 1075, 1079, 1086, 1091 aneurysm 106, 160, 168, 171, 172, 179, 188, 190, 199, 200, 204, 205, 206, 221, 222, 232, 238, 242, 246, 270, 277, 290, 302, 605, 703, 881 aneurysmal bone cyst 1204 angiitis 167, 168, 975, 1064 angioma 309, 320, 1237 anterior sacral meningocele 1107 antiphospholipid syndrome 168 arachnoid cysts 9, 69, 71, 74, 77, 80, 467, 598, 605, 1044 arachnoiditis 1237, 1250 arteriovenous fistula 179, 204, 251, 253, 277, 302, 1236 arteriovenous malformations (AVM) 7, 251, 277, 309, 1236 arteriovenous shunt. see arteriovenous fistula arteritis 167, 168, 171, 179, 205, 963, 965, 1054 astrocytoma 8, 12, 19, 20, 22, 62, 333, 335, 336, 340, 348, 352, 358, 383, 389, 392, 395, 397, 398, 401, 407, 415, 422, 425, 430, 461, 489, 591, 618, 640, 1124, 1125 atherosclerosis 87, 101, 106, 107, 109, 139, 153, 154, 160, 172, 206, 242 atlanto-occipital dislocation 1264 atlas 29, 232, 497, 522, 617, 963, 965, 969, 985, 1122, 1265 axonal injury, diffuse (DAI) 1054 B bacterial infections 605 Binswanger’s disease. see Hypertensive encephalopathy chronic Bourneville-Pringle syndrome. see Tuberous sclerosis brain death 881, 887
C capillary hemangioblastoma. see hemangioblastoma carcinoma 412, 503 carcinomatosis 418, 1184 cavernous angioma 179, 193, 195, 247, 269, 309, 311, 316, 489, 510, 785, 1237 cavernous malformation 251 cephalocele 31 cerebellopontine angle 71, 651, 661, 669, 672, 680, 727, 881 cerebral contusions 808 cerebral infarction 964 cerebritis 868, 949, 961, 965, 972, 975 cerebrohepatorenal syndrome. see Zellweger syndrome chemodectoma 334 chemotherapy 22, 436, 440, 457, 491, 1022, 1026, 1027 chondrosarcoma 334, 445, 617, 785, 793, 1195 chordoma 334, 574, 585, 617, 1196 choriocarcinoma 334, 489, 491, 501, 523 choroid plexus carcinoma 334, 335, 412, 430 choroid plexus papilloma 334, 335, 412 circle of Willis 161, 199, 200, 529, 567, 869, 975 colloid cyst 334, 415, 467, 471 cortical dysplasia 21, 50, 53, 418, 422, 1005 craniopharyngioma 334, 415, 556 cryptococcosis 972, 973, 985, 986 cysticercosis 612, 949, 993, 995 cysts –– arachnoid 9, 69, 71, 74, 77, 80, 167, 181, 464, 467, 476, 574, 598, 605, 719, 733, 831, 841, 849, 910, 925, 960 –– choroids plexus 467 –– colloid 334, 415, 464, 467, 471 –– dermoid 334, 464, 467, 510, 580, 581, 672 –– ependymal 407, 429, 464, 471 –– epidermoid 9, 334, 464, 467, 489, 510, 574, 580, 581, 672, 1099, 1122, 1184 –– porencephalic 50, 57, 464, 476, 890, 941 cytomegalovirus 984, 986, 1049, 1070, 1071 D DAI. see Axonal injury, diffuse
1286
DAVF. see Dural arteriovenous fistula demyelinating disease 1033 demyelination 975, 987, 1003, 1004, 1006, 1008, 1010, 1013, 1020, 1022, 1023, 1025, 1026, 1029, 1033, 1034, 1035, 1036, 1039, 1042, 1044, 1047, 1048, 1049, 1054, 1060, 1062, 1063, 1064, 1069, 1260, 1261 Dens fracture 1265 dermal sinus 1098, 1099, 1184, 1250 dermoid cyst 334, 582 diastematomyelia 1098, 1113, 1118, 1184 diffuse axonal injury 1054 disc herniation 1088 disease –– Alexander 1004, 1006, 1010, 1012 –– Binswanger 1033, 1049 –– Canavan 22, 1005, 1006, 1008, 1010 –– congenital 29, 80, 160, 167, 464, 467, 672, 964, 988, 1003, 1097, 1124 –– degenerative 93, 196, 200, 201, 519, 562, 733, 1003, 1013, 1023, 1033, 1078, 1079, 1096, 1122, 1179, 1224, 1267, 1271, 1274, 1277 –– Huntington 1075, 1084, 1085, 1091 –– Krabbe 179, 1004, 1005, 1006, 1012 –– neurodegenerative 1058, 1075, 1091 –– parasitic 612 –– Parkinson 1075, 1076, 1078, 1091 –– Pick 1079, 1080 –– von Recklinghausen 60, 160, 573, 1168 –– Wilson 1003, 1005, 1016, 1020, 1028, 1075, 1077 DNET. see Neuroepithelial tumor, dysembryoplastic dorsal dermal sinus 1098 duplicated spinal cord (diplomyelia) 1113 dysembryoplastic neuroepithelial tumor. see DNET dysraphism –– myelomeningocele 29, 1097, 1118, 1122 –– tethered spinal cord 1107, 1118 –– tethered Spinal Cord 1118 E echinococcus 997 empty sella 531, 532 empyema 8, 172, 890, 898, 904, 913, 945, 946, 947, 949, 961 encephalitis 167, 898, 902, 945, 961, 973, 975, 976, 978, 979, 984, 985, 986, 987, 988, 989, 993, 995, 1003, 1006, 1033, 1047, 1048, 1060, 1062, 1063, 1064, 1069, 1070 encephalomalacia 8, 36, 58, 106, 136, 139, 176, 979, 985, 1049 encephalopathy 107, 109, 197, 418, 969, 986, 987, 1004, 1016, 1022, 1023, 1026, 1028, 1029, 1033, 1035, 1049, 1070, 1071, 1076, 1079, 1082, 1083, 1088 eosinophilic granuloma 476 ependymitis 412, 849, 898, 907, 945, 952, 959, 963, 965, 985 ependymoma 19, 195, 333, 335, 395, 406, 407, 415, 422, 425, 430, 489, 618, 628, 631, 640, 651, 1124, 1129 epidermoid cyst 334, 467, 470, 1122 epidural empyema 946 epilepsy 7, 12, 21, 46, 50, 53, 60, 277, 418, 865, 985, 988, 1016, 1069, 1085
Subject Index
F fifth ventrivle (sp) 464 fractures 807, 808, 813, 831, 841, 854, 857, 862, 864, 865, 868, 869, 881, 898, 910, 912, 913, 1097, 1224, 1227, 1261, 1264, 1265, 1267 fungal infection 969, 972, 1070 fusion 25, 80, 1096, 1097 G germinoma 334, 489, 491, 497, 579 glioblastoma 8, 20, 22, 333, 335, 336, 352, 461, 462, 489, 510, 631, 691, 957, 1062, 1129 glioma 8, 60, 62, 335, 336, 397, 406, 440, 457, 461, 510, 523, 574, 617, 618, 643, 1054, 1070 gliosarcoma 333, 334, 335, 388 gliosis 136, 139, 145, 242, 251, 265, 808, 890, 892, 925, 986, 993, 1003, 1004, 1013, 1022, 1035, 1037, 1039, 1047, 1049, 1062, 1069, 1075, 1076, 1077, 1078, 1080, 1083, 1085 glomus tumor. see paraganglioma granular cell tumor. see Pituicytoma granuloma 457, 476, 481, 574, 965, 975 H haemorrhage –– acute 109, 167, 181, 813, 821, 831, 844, 848, 849, 851, 963, 975, 979, 1023, 1029, 1033, 1042, 1054, 1058, 1064, 1081, 1250, 1260 –– amyloid 179, 197, 1082 –– intracranial 179, 199, 200, 207, 247, 430, 501, 672, 831, 854, 868, 945, 975 –– intraventricular 192, 562, 564, 849, 854, 868, 995 –– subarachnoid 166, 179, 188, 255, 849, 854, 925, 993 hamartoma 53, 62, 65, 334, 415, 418, 585, 591, 1150 head injuries 854 hemangioblastoma 65, 395, 422, 617, 628, 643, 1143 hemangioma 407 hemangiopericytoma 785, 796 hematoma 9, 181, 703 hemosiderosis (superficial siderosis) 190 herniation 31, 35, 43, 179, 340, 821, 844, 1064, 1088, 1168, 1264, 1271, 1274 herpes encephalitis 986 herpes simplex 975, 976, 985 heterotopia 39, 49, 415, 585 HIE. see hypoxic-ischemic encephalopathy histiocytoma 334, 388, 785, 793 HIV encephalitis 986, 987 HIV infection. see also AIDS HIV myelopathy 1058 holoprosencephaly 41, 42, 43, 58, 1012 Huntington disease 1091 hydranencephaly 57, 58 hydrocephalus 29, 31, 36, 39, 40, 42, 43, 53, 57, 58, 60, 69, 71, 74, 83, 175, 193, 213, 651, 849, 854, 868, 881, 890, 907, 909, 910, 919, 921, 924, 925, 926, 929, 930, 933, 941, 960, 961, 963, 965, 969, 972, 973, 975, 985, 987, 988, 993, 1004, 1023, 1035, 1044, 1080, 1085 hydromyelia 29, 925, 1100, 1264
Subject Index
hygroma 841 hypertension 80, 107, 139, 154, 175, 179 hypertensive encephalopathy 197 hypotension 60, 103, 105, 1023, 1078 I immune deficiency syndromes. see also AIDS infarction –– anoxic 105 –– arterial 109, 179, 196, 199, 727 –– cerebellar 53, 392, 618, 640, 643, 892, 979, 1013, 1085 –– cerebral 31, 58, 77, 87, 101, 103, 106, 151, 160, 166, 172, 196, 199, 213, 311, 321, 323, 415, 481, 755, 808, 1060, 1070, 1075, 1080, 1082, 1083, 1091 –– cortical 50, 960, 961, 965, 1004, 1005, 1008, 1035 –– lacunar 107, 109, 139, 158, 1079 –– multiple 65, 158, 168, 199, 369, 481, 523, 612, 651, 719, 785, 952, 963, 997, 1033, 1034, 1070, 1075, 1077, 1091, 1145 –– subacute 119, 182, 311, 831, 844, 848, 849, 985, 1016, 1022, 1025, 1026, 1033, 1062, 1064, 1237, 1264 –– venous 172, 251, 320, 321, 323, 425, 531, 700 infections 106, 168, 290, 432, 476, 605, 612, 865, 868, 898, 945, 949, 960, 964, 969, 972, 975, 976, 978, 979, 985, 988, 1063, 1064, 1070 inflammation 19, 167, 172, 436, 612, 898, 902, 904, 910, 945, 949, 973, 975, 979, 993, 1034, 1277, 1279 infundibulum 529, 531, 545, 598, 612, 808 injuries. see trauma intradural neoplasms 1184 intrasellar cysts 532 intravertebral disc herniation. see Schmorl node K Krabbe disease 179, 1004, 1005, 1006, 1012 kyphosis 1279 L lacunar infarction 107, 112, 139, 145, 158 Langerhans cell histiocytosis 432, 591 leptomeningeal 151, 168, 197, 415, 418, 436, 857, 904, 963, 973, 975, 1082 leukodystrophy 21, 1004, 1006, 1008, 1010, 1012, 1013, 1028, 1029 leukoencephalopathy 418, 440, 457, 987, 1004, 1006, 1008, 1013, 1022, 1023, 1026, 1027, 1033, 1054, 1063, 1070 leukomalacia 60, 1049 ligamentum flavum 1264, 1277 lipoma 39, 334, 476, 489, 510, 531, 785, 1098, 1099, 1100, 1118, 1122 lipomyelomeningocele 1098, 1100 lissencephaly 46, 985 LMMC. see lipomyelomeningocele lymphoma 20, 22, 334, 418, 432, 436, 437, 440, 441, 1070, 1150, 1199 M macrocephaly 1004, 1008, 1012, 1016 Marfan syndrome 160, 167, 206, 207
1287
medulloblastoma 334, 395, 407, 412, 415, 430, 617, 618, 628, 640, 643, 1150 megalencephaly 53, 58, 1013 melanocytoma 334 melanoma 65, 195, 334, 440, 445, 450, 461, 464, 691, 705, 711, 802, 1150 meningioma 22, 62, 222, 334, 406, 412, 415, 489, 519, 594, 614, 669, 670, 711, 719, 722, 723, 733, 738, 745, 753, 755, 767, 768, 778, 779, 781, 785, 796, 802, 1086, 1168, 1179 meningitis 167, 898, 904, 907, 912, 913, 960, 961, 963, 965, 969, 970, 972, 975, 976, 986, 988, 993, 995 meningocele 31, 1097, 1098, 1107, 1113, 1168 meningoencephalitis 890, 913, 963, 975, 979, 984, 985 metastasis 131, 179, 195, 196, 205, 260, 358, 383, 412, 440, 445, 450, 457, 461, 462, 481, 489, 497, 614, 631, 643, 711, 949, 957, 1027, 1039, 1226 microcephaly 46, 53, 979, 985, 988 moyamoya 12, 15, 160, 161, 162, 163, 166, 179, 198 MS. see Multiple sclerosis mucocele 567, 612 mucopolysaccharidoses 1005 multiple myeloma 481 multiple sclerosis (MS) 158, 166, 168, 323, 418, 457, 700, 949, 969, 987, 1006, 1012, 1026, 1033, 1034, 1129, 1260 myelocele, lipomyelomeningocele vs. 1097, 1118 myelocystocele, terminal 1098 myeloma 481, 1196, 1198 myelomalacia 1237, 1264 myelomeningocele, MMC 1097, 1118, 1122 myelopathy 986, 987, 1022, 1026, 1027, 1033, 1058, 1070, 1071, 1088 N nerve sheath tumors. see also Neurofibroma neurilemmoma. see schwannoma neuritis 984, 1034, 1035, 1042, 1064, 1070 neuroblastoma 334, 336, 429, 430, 510, 617, 796, 1212, 1219 neurocutaneous disorders 60 neurocysticercosis 467 neuroectodermal tumor, primitive (PNET) 19, 334, 425, 429, 430, 691 neuroepithelial cyst. see Ependymal cyst neuroepithelial tumor, dysembryoplastic (DNET) 334, 336, 401, 422 neurofibroma 62, 334, 1156 neurofibromatosis –– neurofibromatosis type 1 60 neurosarcoidosis 167, 168, 440, 969, 1054 O oligodendroglioma 333, 335, 395, 397, 415, 418, 425, 430, 489, 618, 802, 1143 osteoblastoma 1204 osteochondroma 1199, 1203, 1205 osteoid osteoma 1203 osteoporosis 481, 1198, 1267, 1279 osteosarcoma 432, 445, 793, 1195
1288
P pachygyria 46, 53 paraganglioma 334 Parkinson disease 1075, 1076, 1078, 1091 pineal cyst 519 pineoblastoma 334, 464, 489, 506, 510 pineocytoma 334, 489, 506 pituitary adenoma 205, 222, 334, 532, 535, 537, 552, 612, 1044 pituitary apoplexy 556 plasmacytoma 334, 481 pleomorphic xanthoastrocytoma 333, 335, 336, 395 PNET. see Neuroectodermal tumor, primitive porencephalic cyst 50, 57, 464, 476, 890, 941 postoperative complications 946 primitive neuroectodermal tumor (PNET) 19, 334, 425, 429, 430, 691 prolactinoma 535 R radiation 1, 2, 3, 9, 12, 17, 20, 25, 41, 171, 172, 179, 457, 490, 491, 497, 585, 793, 808, 1022, 1026, 1027, 1039, 1054, 1058, 1093, 1203 rhabdomyosarcoma 334, 617, 785, 793, 796 S SAH. see Subarachnoid hemorrhage sarcoidosis 168, 612, 614, 969, 1054, 1070 sarcoma 432, 617, 793, 796, 986, 1194 schizencephaly 49 schwannoma 62, 651, 1150, 1156 scoliosis 1118 sickle cell 15 simple meningocele 1107 sinus thrombosis 172, 175, 191, 276, 277, 290, 304 spina bifida aperta 1097 spina bifida cystica 1097 spina bifida occulta (posterior element incomplete fusion) 1098, 1100, 1113 spondylitis 1250, 1277 spondylolisthesis 1267 spondylosis 1088 stroke 8, 15, 20, 58, 88, 101, 103, 106, 107, 109, 111, 113, 119, 131, 136, 139, 145, 151, 152, 154, 158, 160, 163, 166, 167, 168, 171, 172, 175, 179, 260, 340, 401, 422, 457, 700, 924, 945, 1004, 1016, 1049, 1054
Subject Index
Sturge-Weber syndrome 60, 62, 476 subacute necrotizing encephalomyelopathy. see Leigh syndrome subarachnoid hemorrhage (SAH) 166, 179, 188, 255, 849, 854, 930, 998, 1143, 1236 subependymoma 333, 335, 397, 407, 415, 643 superficial siderosis 190 syndrome –– antiphospholipid 168 –– immune deficiency 945, 960, 979, 985, 986, 989 –– Leigh 1004, 1005, 1016 –– Marfan 160, 167, 206, 207 –– Sturge-Weber 60, 62, 179, 476 –– Wyburn-Mason 253 syphilis 153, 167, 605, 963, 964, 1058 syringohydromyelia 1129, 1150 systemic lupus erythematosus 167, 168, 197, 205, 432 T teratoma 334, 395, 489, 491, 497, 501, 574, 580, 581 tethered spinal cord 1107, 1118 thrombosis –– arterial 58, 87, 93, 101, 109, 151, 153, 167, 265, 309, 311 –– venous 171, 172, 175, 191, 276, 277, 291, 295, 304, 322, 907 toxoplasmosis 58, 440, 985, 986, 988, 989, 1070, 1071 transverse myelitis 979, 984, 1035, 1237 trauma 160, 171, 172, 204, 302, 531, 612, 807, 831, 844, 848, 854, 857, 862, 881, 892, 1035, 1054 tuberculosis 153, 167, 605, 612, 700, 964, 965, 969, 986, 1070, 1237, 1250 tumors 19 V vascular lesions 171, 207, 242, 579, 963, 986 vasculitis 12, 15, 101, 139, 167, 168, 171, 179, 198, 205, 963, 975, 984, 985, 986, 987, 1033, 1035, 1042, 1054, 1064, 1070 vein of Galen malformation 276, 277 ventriculitis 868, 898, 907, 913, 949, 959, 961, 993 ventriculomegaly 890, 959, 979, 985 W Wallerian degeneration 145, 829, 1005, 1060, 1088, 1091 Wegener granulomatosis 167 Wilson disease 1075
