High-Resolution Ultrasonography for Peripheral Nerve Diagnostics
A Guide for Clinicians Involved in Diagnosis and Management of Peripheral Nerve Disorders
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High-Resolution Ultrasonography for Peripheral Nerve Diagnostics
A Guide for Clinicians Involved in Diagnosis and Management of Peripheral Nerve Disorders
Einar P Wilder-Smith K Rajendran National University of Singapore, Singapore
Aravinda K Therimadasamy National University Hospital, Singapore
World Scientific NEW JERSEY
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LONDON
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BEIJING
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TA I P E I
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9/14/09 4:46:49 PM
Published by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE
Library of Congress Cataloging-in-Publication Data Wilder-Smith, Einar P. High-resolution ultrasonography for peripheral nerve diagnostics : a guide for clinicians involved in diagnosis and management of peripheral nerve disorders / Einar P. Wilder-Smith, K. Rajendran, Aravinda K. Therimadasamy. p. ; cm. Includes bibliographical references and index. ISBN-13: 978-981-283-903-9 (pbk. : alk. paper) ISBN-10: 981-283-903-8 (pbk. : alk. paper) 1. Nerves, Peripheral--Ultrasonic imaging. 2. Nerves, Peripheral--Diseases--Diagnosis. I. Rajendran, K. II. Therimadasamy, Aravinda K. III. Title. [DNLM: 1. Peripheral Nervous System Diseases--ultrasonography. 2. Peripheral Nerves-ultrasonography. 3. Ultrasonography--methods. WL 500 W673h 2009] RC409.W55 2009 616.8'5607543--dc22 2009035927
British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library.
Copyright © 2010 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher.
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Preface
The clinical neurophysiologist is primarily concerned with being able to provide an accurate diagnosis. Defining the location and extent of a lesion is achieved through a detailed clinical examination with judicious application of additional tests of nervous function. The role of nerve conduction studies and the related techniques of EMG evoked potentials in providing further functional information has been well established. Recently, however, technical advances in imaging techniques have enhanced the scope for providing the clinician with much-improved anatomical information regarding disorders of the peripheral nervous system. The technical advances of high resolution ultrasonography (HRU) have been nothing less than spectacular, enabling hugely improved depiction of peripheral nervous structures in a three-dimensional setting. This technique is set to progress rapidly and become an established adjunct of the clinical neurophysiologist. Combination with color Doppler allows integration of additional information on the vascular supply of the peripheral nerves. However, the main advance brought about by HRU is that it enables accurate localization of peripheral nerve disorders. In addition, it is cheap and readily available, in contradistinction to the costly MRI techniques. A further advantage is that it allows dynamic, real time injections of nerves, which are frequently performed by anesthetists. v
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High-Resolution Ultrasonography for Peripheral Nerve Diagnostics
In this book we aim primarily to provide hands-on information for clinicians involved in peripheral nerve diagnostics, who are often clinical neurophysiologists. We have thus selected topics for which HRU is of particular help in achieving a diagnosis. We are confident that in the near future HRU will become a valuable if not indispensable companion technique for the clinical neurophysiologist. We hope that this book will help provide the user with a crucial, practical link between the anatomy of the peripheral nerves and the use of HRU in the identification of peripheral nerve disease. EP Wilder-Smith, K Rajendran & AK Therimadasamy National University of Singapore, May 2009
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Acknowledgements
Special thanks to Mdm BAY SONG LIN from the Department of Anatomy, Yong Loo Lin School of Medicine, National University Singapore, for her excellent contribution in drawing the anatomical illustrations.
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About the Authors
Professor Einar P. Wilder-Smith, MD (Heidelberg), FAMS (Neurology), DTM & H (London), Senior Consultant, Neurology, National University Hospital, Singapore, 5 Lower Kent Ridge Road, 119074 Singapore, email:
[email protected]
Einar P. Wilder-Smith is Professor in the Department of Medicine, Yong Loo Lin School of Medicine, National University, Singapore. He is also Director of Clinical Neurophysiology, past-President of the Singapore chapter of the International Federation of Clinical Neurophysiology and President of the Chapter of Neurology, College of Physicians, Singapore. He was awarded his MD thesis from the University of Heidelberg, Germany and trained in Neurology at the University of Heidelberg, Germany and at the University of Bern, Switzerland. His research focus is on peripheral nerve disorders, with an emphasis on improving diagnostics and treatment.
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High-Resolution Ultrasonography for Peripheral Nerve Diagnostics
Associate Professor Dr Rajendran K. Department of Anatomy, National University, Singapore, 5 Lower Kent Ridge Road, 119074 Singapore
Rajendran Kanagasuntheram graduated from the Faculty of Medicine, National University of Singapore and practiced general surgery before joining the department of Anatomy where he has served for the past 30 years teaching both medical and dental undergraduates as well as postgraduates. His main interest, besides medical education, has been in the development of multimedia material to enhance the teaching and learning of anatomy.
Therimadasamy AK, BSc, Medical Technologist, Neurology Diagnostic Laboratory, National University Hospital, Singapore, 5 Lower Kent Ridge Road, 119074 Singapore
Aravinda K Therimadasamy BSc, is a medical technologist in the Neurology Diagnostic Laboratory, National University Hospital, Singapore. He graduated in Physical Therapy from Tamilnadu Dr. M.G.R. Medical University, India. He has been involved in many research projects related to the diagnosis of peripheral nerve disorders in various medical conditions including leprosy. His main interests are in developing novel neurodiagnostic tests to identify early dysfunction in different types of nerve fibers.
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Contents
Preface Acknowledgements About the Authors
v vii ix
1. Introduction Technical Considerations of High Resolution Ultrasonography Advantages of HRU Characteristics of Healthy Peripheral Nerves Appearance and identification Measurements Characteristics of Diseased Peripheral Nerves 2. Finding the Nerve Antebrachial Nerves Medial antebrachial (L) Brachial plexus (R) Cervical Roots (C5 & 6) (R) Ilioinguinal Nerve (R) Lateral Femoral Cutaneous (R) Median Nerve (Carpal Tunnel) (R) Peroneal Nerve (Fibular Head) (R) Radial Nerve (Spiral Groove) (R) Radial Nerve (Supinator Canal) (L) xi
1 1 3 3 3 4 6 9 10 10 11 12 13 14 15 16 17 18
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High-Resolution Ultrasonography for Peripheral Nerve Diagnostics
Sciatic Nerve (Proximal) (L) Superficial Peroneal Nerve (Shin) (L) Superficial Radial Nerve (Forearm) (R) Sural Nerve (Lower Calf) (R) Tibial Nerve (Knee) (L) Tibial Nerve (Tarsal Tunnel) (R) Ulnar Nerve (Elbow) (R) Ulnar Nerve (Wrist) (L)
19 20 21 22 23 24 25 26
3. Clinical Applications Common Entrapment Neuropathies Median neuropathies including carpal tunnel syndrome Ulnar neuropathy at the elbow Less Common Entrapment Neuropathies Radial neuropathy Ulnar nerve at the wrist Peroneal neuropathy Lateral femoral cutaneous nerve Ilioinguinal nerve Morton’s neuroma Brachial plexus Tarsal tunnel syndrome Other Conditions Sciatic neuropathy Inflammatory conditions Other Uses Nerve Blood Flow
27 27 27 32 33 35 36 38 39 41 41 42 46 46 46 47 49 50
References Index
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1 Introduction
Technical Considerations of High Resolution Ultrasonography This is primarily a book for the clinician and will therefore not address the technical basis of sonography in any detail. However, it is necessary for the clinician to know about the limitations resulting from the underlying mechanisms of sonography. We will briefly consider these in the following. High resolution ultrasound is based on an electromechanical transducer probe issuing ultrasonic waves which are transmitted into the tissue to be examined. As the ultrasonic waves travel into the tissue, the varying reflective properties of the tissue cause differential reflection, resulting in the waves being reflected back to the transducer at different times. This allows a picture of the tissue to be created; the details of the process can be found in the literature.1 The most commonly used insonation frequencies for HRU range between 7 and 15 MHz, but sometimes, depending on the circumstances, a range of 3–20 MHz is used. Modern transducers have greater resolution, mainly because there are more arrays of transmitting and receiving crystals within them. More technical details can be obtained from expertly summarized publications in the literature.2
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High-Resolution Ultrasonography for Peripheral Nerve Diagnostics
The clinician needs to remember certain simple technical considerations when using HRU: (1) The higher the frequency of the ultrasound probe used, the greater the axial resolution. However, this comes at the cost of less depth of tissue penetration. For example, a 15 MHz probe would be able to reveal superficial structures of up to 1–2 cm with good resolution but would not be able to show the deeper-lying nerves such as the sciatic nerve, which would be best imaged with a lower frequency of 3–7 MHz. (2) Nerves may be difficult to separate out from surrounding fat tissue because of their similar echogenic properties. (3) Bones overlying nerves result in acoustic shadowing and thereby render them invisible. (4) Because of the phenomenon of anisotropy, the ultrasound probe needs constant steering to adjust for the best angle of insonation. Anisotropy describes the property of being directionally dependent. In other words, the ultrasound waves are transmitted in an inhomogenous way and do not reflect evenly in all directions. (5) The pressure applied to the probe will determine the degree of deformation of the underlying structures and for this reason should be kept to a minimum. The examiner needs to remember that instead of applying more pressure on the area of examination, when trying to obtain better ultrasound pictures, a clearer picture is produced with plenty of contact gel in place and if possible using insonation angles which avoid obstructing tissue (fat or bone). In the heat of the battle, it is easy to forget that ultrasonic waves need gel, gel, and gel! In remembering these technical limitations, HRU can be very useful for aiding the diagnosis of many peripheral nerve
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Introduction
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entrapments in the human body, as well as guiding anesthetic nerve blocks and localizing other musculoskeletal elements such as muscles and tendons.
Advantages of HRU
(1) A significant advantage of HRU in contrast to most neurophysiological techniques is that it causes little or no discomfort to the patient. (2) HRU provides real time images of the nerve anatomy and its surrounding structures, and gives clues to the etiology of nerve dysfunction (for example, ganglion cysts as etiology of peroneal nerve palsy, or showing whether trauma has resulted in nerve discontinuity). (3) Compared to MRI, HRU can be performed very fast, is considerably cheaper, and can be combined with anesthetic procedures. (4) Integrated color Doppler allows concomitant measurement of the blood flow of surrounding structures.
Characteristics of Healthy Peripheral Nerves Appearance and identification
Characteristics of peripheral nerves
(1) More echogenicity than muscles but less echogenicity than tendons (2) Honeycomb appearance (3) Less mobility than tendons
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High-Resolution Ultrasonography for Peripheral Nerve Diagnostics
In HRU, normal peripheral nerves have the appearance of being more echogenic than muscles but less echogenic than tendons (Fig. 1). A nerve visualized longitudinally is characterized by tubular, more echogenic (darker) structures separated by less echogenic lighter ones. Thus the hypoechoic fascicles surrounded by hyperechoic perineurium reveal the fascicular structure of peripheral nerves.3 Viewed in transverse cuts this gives rise to the characteristic “honeycomb structure” which nerves are often typified by. Because tendons can sometimes produce a quite similar structural pattern, it is worthwhile to remember that tendons are generally more echogenic (i.e. darker in the ultrasound picture) and characteristically more mobile during extension–flexion maneuvers. In some instances, when differentiation between a tendon and a nerve is difficult, following the structure to an anatomical site where the nerve anatomy is well known can be helpful (such as the ulnar nerve in the ulnar canal at the elbow). Measurements Commonly used nerve measures
Transverse nerve cuts document the cross-sectional surface area, often expressed in cm2. Longitudinal nerve cuts measure the nerve diameter. Make sure that measures are taken inside the hyperechogenic rim of the nerve.
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Introduction
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Fig. 1 Normal appearance of the median nerve at the carpal tunnel. On the top is a transverse sonogram of the median nerve at the level of the distal wrist crease, showing the nerve surrounded by flexor tendons. The crosssectional area of the nerve is 0.08 cm2 (normal < 0.10 cm2). On the bottom is a longitudinal sonogram of the median nerve across the proximal carpal tunnel. The maximum anteroposterior diameter of the nerve is 0.16 cm.
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Cadaver studies have shown HRU to be very precise at measuring the dimensions of the nerve diameter, perimeter and surface area.4 Current technology has an image resolution of around 1 mm. To make the measurements uniform, the diameter/surface area is taken from inside the hyperechogenic rim of the nerve. Using the hyperechogenic rim as measurement is not advisable, since it is known to be variable and provides less consistent measurement. The size of normal nerves follows a Gaussian distribution with little or no effect of age, height or weight. For selected nerves (median, radial, ulnar) men show greater size than women.5 As a rule, it is easier to image upper extremity than lower extremity nerves. This is because lower limb nerve trunks are generally at a greater depth and can have more perineurial fat. In particular, the proximal lower limb nerves exiting the inguinal region can be difficult to image as fat degrades the ultrasonic image quality. The femoral nerve and lateral femoral cutaneous nerve can be especially difficult to image. However, some lower limb nerves are easily imaged, such as the superficial cutaneous nerves like the sural nerve. Characteristics of Diseased Peripheral Nerves Characteristics of diseased nerves in sonography
(1) Nerve enlargement (2) Hypoechoic signal resulting from nerve edema (3) Discontinuity of nerve fascicles — complete or incomplete
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(1) Nerve enlargement
Nerve enlargement is the most common characteristic of nerves observed with HRU and can be seen in nerve entrapment, inflammatory disease, hereditary neuropathies, and nerve tumors. The main ultrasound feature of chronically entrapped nerves is nerve enlargement, which occurs mostly proximal to the site of compression and is a result of nerve edema and increased collagen deposition. Nerve enlargement is best measured in transverse sections using the cross-sectional surface area at predefined anatomical locations. Predefined locations should be adhered to, in order to keep to a minimum the variance from the natural proximal-to-distal thinning of nerves. The measure of the nerve surface area is accepted as most representative in capturing nerve enlargement, since it is least affected by nerves’ variables in symmetry, which can cause diameter measures taken with longitudinal sections to be more variable and so less reliable. Although the overall increase in nerve size is one of the best measures of nerve reaction common to many types of pathology, intraneural increases in fascicular size can also be directly visualized and can be helpful in localizing the exact site of pathology. (2) Hypoechoic signal resulting from nerve edema and other disease patterns
A further measure of nerve pathology is increased or decreased echogenicity of the nerve. This is more difficult to quantify or qualify and interpretation depends on the experience of the examiner.
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Certain etiologies of nerve pathology have been identified to show typical HRU appearances. Neuromas have a characteristic spindle shape inside nerves at the sites of nerve reconstruction. The texture shows up as being of low or mixed echo texture located close to the inner surface of the epineurium.6 HRU is particularly good in the identification of intraneural pathology such as neurilemmoma or for cystic structures.7 The nerve enlargement seen in inflammatory diseases does not show any characteristics of echogeneity. Leprosy, chronic inflammatory demyelinating neuropathy, and multiple and motor neuropathy with multiple motor conduction blocks (MMN) all show (often greatly) enlarged nerves in multiple areas.8 (3) Fascicular discontinuity
With the assessment of nerve trauma, apart from showing the exact site of nerve damage, a very useful HRU feature is that it can help in identifying nerve integrity, i.e. demonstrating nerve continuity. The most useful parameter to use is the hyperechoic outer nerve surface, which corresponds to the continuous epineural perineurium. Another helpful measure is disruption of the fascicular structure within the nerve, best seen with longitudinal views.9
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2 Finding the Nerve
In this section, three figures are included for each nerve: First, a picture of the probe position; second, the anatomical illustration, and third, what is seen on sonography. R denotes the right side, and L, the left side.
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Antebrachial Nerves Medial antebrachial (L)
Anterior Medial antebrachial cutaneous N
Brachial A Cephalic V Biceps M Brachialis M
V V Radial N Basilic V
Medial
Humerus
Median N
Brachioradialis M Ulnar N
Triceps brachii M
Medial antebrachial cutaneous nerve
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(a) The probe is positioned 5–8 cm above the medial epicondyle over the medial aspect of the upper arm. (b) Recognition of the basilic vein enables the nerve to be easily identified.
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Brachial Plexus (R)
Anterior Sternocleidomastoid M
Internal Jugular V Common carotid A
Th gla yroid nd
Scalenus anterior M
Vertebral A
C5 Cervical Vertebral body
C6 C7
Transverse process
Scalenus medius M
Brachial plexus
(a) Probe is placed at about 30° in the coronal oblique plane in the mid-lower region behind the sternocleidomastoid muscle. (b) The three trunks are seen lying between the anterior and medial scalenus muscles. 11
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Cervical Roots (C5 & 6) (R)
Superior Sternocleidomastoid M
Transverse process (posterior tubercle)
C5
Transverse process (anterior tubercle) C6
Lateral
C7
C6 nerve root T1
1s rib
Scalenus medius M Scalenus anterior M
Vertebral A
Cervical 6th root
(a) The probe axis is parallel to that of the cervical spine. (b) The 5th and 6th cervical roots are seen as they exit from the vertebral foramina. 12
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Ilioinguinal Nerve (R)
Anterior External abdominal oblique M Internal abdominal oblique M
Transversus abdominis M Deep circumflex iliac V
Ilioinguinal and iliohypogastric N
Ilium
Femoral N
Right Lateral
Gluteus medius M
Ilioinguinal nerve
(a) The probe is positioned adjacent to the anterior superior iliac spine (ASIS), with the lateral aspect of the probe hugging the ASIS. (b) Ultrasound image showing the three abdominal muscle layers, with the ilioinguinal nerve being found between the internal oblique and transversus muscles.
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Lateral Femoral Cutaneous (R)
Anterior Internal abdominal oblique M
Lateral femoral cutaneous N IIium Femoral N
Right Lateral Iliacus M Gluteus minimus M Gluteus medius M
Lateral femoral cutaneous nerve
(a) The lateral aspect of the probe is positioned on top of the anterior superior iliac spine (ASIS), with the plane of imaging more downwards than in ilioinguinal imaging. (b) The image shows the nerve hugging the iliac bone at the ASIS. 14
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Median Nerve (Carpal Tunnel) (R)
Anterior Flex. carpi ulnaris M Ulnar A Flex. carpi radialis M
Ulnar N Flex. digitorum superfilicalis M
Radial A Medial N
Flex. digitorum profundus M Medial
Abd. pollicis longus M
Ulna Radius
Ext. carpi ulnaris M Ext. digiti minimi M
Ext. pollicis brevis M Ext. carpi radialis longus M Ext. carpi radialis brevis M Ext. pollicis longus M
Ext. digitorum M
Median nerve at the wrist
(a) The probe is held over the distal wrist crease. (b) The median nerve is recognised by its honeycomb structure, being placed more superiorly. 15
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Peroneal Nerve (Fibular Head) (R)
Anterior
Tibialis anterior M
Tibia Medial Common peroneal N
Popliteus M Fibula
Saphenous N Great saphenous V Soleus M
Tibial N
Common peroneal nerve above the fibular head
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(a) The superior aspect of the probe is placed on the fibular head. (b) The nerve must be carefully differentiated from other soft tissue structures such as vessels and tendons.
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Radial Nerve (Spiral Groove) (R)
Anterior Cephalic V
Musculocutaneous N Biceps brachii M
Brachialis M
Median N Radial N
Medial cutaneous N
V
Medial
Humerus
V
Basilic V Ulnar N Brachial A Triceps brachii M
Profunda brachii A
Radial nerve in the spiral groove
(a) The probe is placed at mid-humeral level. (b) The radial nerve is easily seen winding around the humeral shaft under the triceps muscle. 17
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Radial Nerve (Supinator Canal) (L)
Median N
Anterior Ulnar A Radial A Radial N (superficial branch) Brachioradialis M
Ulnar N
Medial Radius Ulnar Radial N (deep branch)
Flex. carpi ulnaris M
Ext. carpi radialis longus M Ext. carpi ulnaris M
Supinator M
Radial nerve (Supinator canal)
(a) With the elbow in a neutral position, the lateral aspect of the probe is over the lateral epicondyle. (b) The two segments of the radial nerve are seen as they traverse the supinator canal. 18
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Sciatic Nerve (Proximal) (L)
Anterior Femoral N Femoral A Femoral V Iliopsoas M Sartorius M
Vastus lateralis M Urinary bladder
Femoral Head
Left Lateral
Rectum
Inferior gemellus M Sciatic N
Gluteus maximum M
Sciatic nerve HRU
(a) The probe is placed at a point about two thirds between the Trochanter major and the tuber ischiadicum. (b) The nerve is deep to the gluteus maximus. 19
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Superficial Peroneal Nerve (Shin) (L)
Anterior Tibialis anterior M Anterior tibial A Flex. digitorum longus M Great saphenous V Saphenous N
Tibia
Soleus M
Superficial peroneal N Peroneus brevis M
Fibula
Medial
Deep peroneal N
Flex. hallucis longus M Peroneal A Gastrocnemius M Small saphenous V
Sural N
Superficial peroneal nerve
(a) The probe is positioned over the lateral lower shin aspect, with the medial probe over the tibial bone. (b) The nerve runs in a plane superficial to the tibial muscle. 20
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Superficial Radial Nerve (Forearm) (R)
Anterior Medial N
Ulnar N
Radial A Brachiaradialis M Superficial Radial N
Basilic V Flex. carpi ulnaris M Flex. digitorum profundus M Ulna
Medial
Radius
Ext. carpi ulnaris M Cephalic V Ext. carpi radialis longus M Supinator M
Superficial radial nerve
(a) At the level of the mid-forearm, the probe is placed more on the radial aspect. (b) The nerve runs next to the radial artery. 21
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Sural Nerve (Lower Calf ) (R)
Anterior Ext. Hallucis longus M
Anterior tibial A
Superficial peroneal N Great saphenous V
Ext. digitorum longus M
Saphenous N
Peroneus brevis M Peroneus longus M
Tibia Fibula
Medial
Short Saphenous V
Tibial A Tibial N Achilles tendon Sural N
Sural nerve above ankle
(a) The probe is placed 5–10 cm above the lateral malleolus. (b) The nerve is anterior and superficial to the Achilles tendon.
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Tibial Nerve (Knee) (L)
Anterior
Patella
Lateral condyle
Medial
Medial condyle
Biceps femoris M Satorius M Gastrocnemius M (lateral head) Common peroneal N
Popliteal A Popliteal V Tibial N
Short Saphenous V
Tibial nerve at knee
(a) The probe is positioned horizontally in the middle of the fossa. (b) Within the neurovascular bundle, the nerve is most superficially situated.
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Tibial Nerve (Tarsal Tunnel) (R)
Posterior Lateral & medial plantar N * Achilles tendon Sural N Small saphenous V Flex. hallucis longus M Tibialis Medial posterior tendon
Peroneus brevis & longus M
Medial malleolus Lateral malleolus Talus
Great saphenous V * Sometimes the calcaneal branch can be identified (see ultrasound picture)
Tarsal tunnel
(a) The anterior aspect of the probe is on the medial malleolus; the posterior aspect on the Achilles tendon. (b) Though the nerve trifurcation is variable, it is often clearly seen lying deep and oblique to vessels. 24
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Ulnar Nerve (Elbow) (R)
Anterior Brachial A Cephalic V
Median N Basilic V Brachialis M
Brachioradialis M
Pronator teres M Medial Epicondyle
Ulnar N
Olecranon of ulna
Anconeus M
Ulnar nerve at elbow
(a) The probe straddles the ulnar sulcus from the olecranon to the medial epicondyle. (b) The nerve is seen hugging the medial epicondyle. 25
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Ulnar Nerve (Wrist) (L)
Anterior Flex. digitorum superfilicalis M Median N Radial A
Abductor digiti minimi M
Abductor pollicis brevis M
Ulnar N Ulnar A Flex. digitorum profundus M Medial
Pisiform Scaphoid Triquetrum
Capitate
Lunate
Ext. carpi ulnaris M
Ext. pollicis brevis M
Ext. pollicis longus M Ext. Carpi Radialis M
Ext. digiti minimi M Ext. digitorum M
Ulnar nerve at wrist
(a) The probe is placed horizontally over the ulnar distal wrist crease. (b) The nerve lies between the pisiform bone and the ulnar artery. 26
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3 Clinical Applications
Common Entrapment Neuropathies In order to obtain the most relevant information, HRU should be performed in parallel with standard nerve conduction. In our experience, this best enables HRU to provide anatomical details complementary to the functional information given by nerve conduction or EMG. Together this information can provide a much more comprehensive picture of the status of the peripheral nerve function/dysfunction.10 Median neuropathies including carpal tunnel syndrome
Carpal tunnel syndrome (CTS) is the most commonly studied condition using HRU, which has shown high diagnostic sensitivity and specificity for supporting a diagnosis of CTS. The literature reports sensitivities and specificities of 70–88% and 57–97%, respectively, with variability accounted for by differing diagnostic criteria and methodology. Studies comparing the sensitivity and specificity of NCV and HRU generally show HRU as having somewhat less or similar sensitivity and specificity to nerve conduction in diagnosing CTS. An advantage of HRU is that it can pick up space-occupying lesions within the carpal canal, such as a persistent median artery, cysts, or ganglions. A further advantage of HRU is when severe damage 27
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to the ulnar and median nerves pushes nerve conduction beyond its limit. In severe polyneuropathies (e.g. Charcot–Marie–Tooth polyneuropathy, uremic or diabetic neuropathy), HRU can be a useful method for providing additional information on whether there is further entrapment.
HRU sensitivity and specificity for supporting a diagnosis of CTS are 70–88% and 57–97%, respectively. The parameter used is the cross-sectional area of the median nerve (> 0.10 cm2). A wrist-to-forearm ratio of > 1.4 increases the sensitivity to near 100%.
There is now good agreement that the median nerve transverse surface area at the level of the distal wrist crease with the wrist in a neutral position is one of the best sonographic measures for detecting CTS.11 Most studies give cut-off values of 9–10 mm2. Figure 2(a) shows typical median nerve enlargement which occurs proximal to the carpal tunnel in a case of CTS. Figure 2(b) shows atypical median nerve enlargement in a 15-year-old boy with idiopathic CTS. Since nerve enlargement in CTS is focal, the inclusion of a comparison with a noninvolved section of the nerve further raises the sensitivity and specificity. The ratio of the median nerve surface area in the wrist to the forearm in normals is 1.0. In one study a ratio of > 1.4 was 100% sensitive for supporting CTS diagnosed by nerve conduction. Nerve enlargement in CTS in the great majority of cases occurs just proximal to the carpal tunnel entrance.12 Enlargement just proximal to the entry into the canal and nerve flattening within the carpal tunnel are the characteristic appearances of the median nerve.
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(a)
(b)
Fig. 2 (a) Typical median nerve enlargement in a patient with CTS. The transverse cut performed at the level of the distal wrist crease in a patient with CTS shows the typical median nerve enlargement (area 0.16 cm2) which occurs proximal to the carpal tunnel. (b) Atypical median nerve enlargement occurring within the carpal tunnel. This transverse section performed over the distal carpal tunnel shows atypical median nerve enlargement occurring within the distal carpal tunnel (cross-sectional area 0.15 cm2).
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However, occasionally median nerve enlargement is seen only within the distal carpal tunnel, which can easily be missed if not sought after in the sonographic evaluation [see Fig. 2(b)]. The anatomical variations of the median nerve are readily identified and assist in the management of medianopathy at the wrist. Common variants include a bifid median nerve, which is often seen together with a persistent median artery (Figs. 3 and 4). In cases of direct trauma to the median nerve, sonography is able to accurately show the level and extent of damage through direct visualization of discontinuous nerve fascicles (Fig. 5).
Fig. 3 Bifid median nerve: transverse section of the median nerve at the proximal entry to the carpal tunnel, showing both an enlarged median nerve (cross-sectional area 0.13 cm2, normal 0.10 cm2) and a bifid nerve structure in a patient with CTS.
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Fig. 4 Persistent median artery and bifid median nerve: transverse section of the median nerve in a patient with CTS, showing a persistent median artery when using the color Doppler mode. Note also the bifid median nerve structure marked by the lower arrows.
Fig. 5 Median nerve damage in the forearm: longitudinal section of the median nerve at the level of the forearm in a patient with forearm crush injury, showing fascicular discontinuity and swelling.
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Ulnar neuropathy at the elbow
HRU sensitivity for supporting a diagnosis of ulnar neuropathy at the elbow is 80–93%; HRU specificity, 91–98%. The parameters used are the diameter of the ulnar nerve within the ulnar sulcus (> 2.5 mm) and the cross-sectional area (> 0.10 cm2).
Ulnar neuropathy at the elbow (UNE) is the secondmost-common entrapment neuropathy, after carpal tunnel syndrome, and is usually diagnosed clinically, with additional confirmation through nerve conduction studies. Since the clinical spectrum of UNE is diverse and nerve conduction can pose technical difficulties, sonography is a useful adjunct for ascertaining a diagnosis of UNE. Several comparisons of nerve conduction and HRU in UNE have now been published, though less information on this entity exists compared to CTS. In UNE the ulnar nerve characteristically enlarges within the sulcus ulnaris and ulnar nerve measurements are commonly performed at the level of the medial epicondyle. In a prospective study comparing the ulnar nerve CSA (cross-sectional area) in healthy controls with those of patients with clearly defined clinical and neurophysiological UNE, a cut-off of 0.10 cm2 or higher for the CSA gave a sensitivity of 93% and a specificity of 98%. The CSA gave more accurate results than the maximal nerve diameter. Furthermore, the correlation between motor nerve conduction and the CSA was good. Another advantage of HRU is that it is able to provide information on the etiology of UNE, which can include anconeus epitrochlearis muscle and occult
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ganglia, and to conclusively diagnose ulnar nerve dislocation. Some publications have shown lower sensitivity (50%) for ulnar nerve enlargement in electroclinically diagnosed UNE.13 This lower sensitivity may be due to differing case selection and also highlights that axonal ulnar neuropathy is preferably accompanied by nerve swelling whereas in a third of patients with demyelination on nerve conduction there is no enlargement. An ulnar nerve ratio > 1.5:1 between the ulnar nerve CSA at the medial epicondyle and the midhumeral level has been shown to be a further useful measure (100% sensitivity, 97% specificity), especially in diseases where there is diffuse enlargement of the nerve (Charcot–Marie–Tooth, amyloid polyneuropathy).14 Figure 6 shows ulnar nerve enlargement in UNE in comparison with a normal nerve from a volunteer. High resolution sonography provides reliable information on ulnar nerve luxation, which is of considerable importance to ensuing treatment of the ulnar neuropathy. Our laboratory routinely assesses the presence of ulnar nerve luxation in UNE by imaging with the elbow in full flexion and 80–90° flexion. More than 50% of the nerve crossing the superior aspect of the medial epicondyle constitutes luxation. Figure 7 shows a completely luxated ulnar nerve in full elbow flexion. Less Common Entrapment Neuropathies The anesthetic literature contains many references to the localization of peripheral nerves.15,16 With good technique and knowledge of anatomy, most peripheral nerves can be imaged. It is best to start imaging at an antomical site where the nerve is known to be easily identifiable, such as the ulnar nerve at the elbow, and then follow the nerve in the direction where the lesion is suspected.
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Fig. 6 Ulnar nerve enlargement in ulnar neuropathy at the elbow: transverse sonogram of a normal-sized ulnar nerve behind the median epicondyle (top image). The cross-sectional area is 0.07 cm2. On the bottom is an enlarged ulnar nerve (cross-sectional area 0.15 cm2).
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Fig. 7 Ulnar nerve luxation at the elbow: transverse section of the ulnar nerve performed in full elbow flexion in a normal subject. The ulnar nerve is completely luxated. Its size remains normal (cross-sectional area 0.06 cm2).
Radial neuropathy
HRU is a useful adjunct for investigating acute radial nerve damage, particularly when this accompanies fracture. Often, patients with humerus fracture and acute arm weakness cannot be satisfactorily examined with nerve conduction owing to pain and swelling. However, because of favorable anatomical features, the radial nerve is easily examined using HRU in patients with a suspected radial nerve. Typical findings on acute radial nerve injury indicate nerve swelling or nerve discontinuity. In a case of humerus fracture with repair, HRU was able to successfully pinpoint the site of the radial nerve lesion (Fig. 8).
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Fig. 8 Traumatic radial nerve damage at the spiral groove: longitudinal sonogram of a radial neuropathy in a patient with humerus fracture. The radial nerve is enlarged at the distal exit to the spiral groove. It also shows abnormal echogenicity maximally, just proximal to the radial nerve enlargement. In addition, the longitudinal section demonstrates the fracture of the humerus.
Even the superficial radial nerve can be readily seen as it heads along the forearm next to the radial artery (Fig. 9). In patients with partial weakness of the wrist/finger extensors, HRU can indicate the site of the radial nerve motor branch entrapment within the supinator canal (Fig. 10). Ulnar nerve at the wrist
Although the distal ulnar nerve is partially covered by bone, HRU is able to provide useful imaging into the proximal region of Guyon’s canal.17 Figure 11 shows an enlarged ulnar nerve within Guyon’s canal in a patient with slowly progressive ulnar muscle wasting within the hand.
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Fig. 9 Superficial radial nerve at the midforearm: transverse section at the level of the midforearm in a patient with CMT 1a, showing a greatly enlarged superficial radial nerve (cross-sectional area 0.17 cm2, normal 0.01 cm2) and a greatly enlarged adjacent median nerve (cross-sectional area 1.03 cm2, normal 0.04 cm2) seen in the same section.
Fig. 10 Radial motor branch entrapment within the forearm supinator canal: enlarged posterior interosseous nerve (cross-sectional area 0.11 cm2, normal 0.03 cm2) within the supinator canal in a patient with extensor weakness of the fingers.
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Fig. 11 Traumatic ulnar neuropathy in Guyon’s canal. The transverse sonogram performed at the level of the entry to Guyon’s canal shows an enlarged ulnar nerve. The area of the nerve is 0.16 cm2 (normal 0.05 cm2).
Sonography is particularly good at localizing the exact location of the nerve lesion and demonstrating nerve discontinuity (Fig. 12). Peroneal neuropathy
Probably the most commonly imaged nerve of the lower extremity is the peroneal nerve, which is most often damaged at the fibular head. In a prospective study of peroneal neuropathy, nearly 20% of all cases had an intraneural ganglion of the nerve identified, amenable to surgical intervention.18 Imaging of the peroneal nerve is not easy, due to the many adjacent soft tisse structures, and it is helpful to use color Doppler to differentiate nerve from vessel. Figure 13 shows an enlarged peroneal nerve in a patient with foot drop compared to a normal peroneal nerve.
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Fig. 12 Ulnar nerve injury at the distal wrist. The ulnar nerve in a longitudinal view is shown to be discontinuous (long arrow) at a level just proximal to the wrist.
Lateral femoral cutaneous nerve
Evaluating meralgia paresthetica is difficult, as the lateral femoral cutaneous nerve can be technically challenging to test with nerve conduction. High resolution sonography offers an additional diagnostic approach and can be useful for evaluating morphologic change or even an aberrant course of the lateral femoral cutaneous nerve.19 Visualizing the nerve is not easy because of the many other soft tissue structures surrounding the area of the anterior iliac spine, the region where the nerve is typically damaged. Excessive fat and variations in the course of the nerve can greatly impede sonographic visualization. Figure 14 shows an enlarged nerve in a patient with meralgia paresthetica.
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Fig. 13 Common peroneal nerve entrapment at the fibular head. On the top is a transverse sonogram of a normal common peroneal nerve at the level of the fibular head just before its bifurcation. The area of the nerve is 0.06 cm2. On the bottom is a transverse section of an enlarged peroneal nerve (cross-sectional area 0.24 cm2).
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Fig. 14 Enlarged lateral femoral cutaneous nerve in meralgia paresthetica: transverse section of the lateral femoral cutaneous nerve (cross-sectional area 0.12 cm2, normal 0.05 cm2) at the level of the anterior superior iliac spine in a patient with meralgia paresthetica.
Ilioinguinal nerve
The ilioinguinal nerve can be readily visualized if so required, both for demonstration of nerve entrapment and for delivery of anesthesia (see section finding nerve).20 Morton’s neuroma
Sonography is a useful method for demonstrating suspected Morton’s neuromas. Ultrasound appearance is typified by the neuroma appearing as a rounded hypoechoic mass close to the metatarsal heads. Ultrasound is able to identify a metatarsal neuroma correctly in 85% of cases when compared with
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histology. Diagnosis is particularly robust if continuity between the interdigital nerve and the neuroma is seen.21 Brachial plexus
Large portions of the brachial plexus are readily accessible to HRU, which can provide useful information in the workup of both acute and chronic plexus conditions. Detailed knowledge of the anatomy and its variations is crucial before one embarks on imaging. Different techniques can be used to visualize the nerves. The technique of proximal localization at the level of the vertebral foramina and then following the nerves longitudinally and transversely down to the axillary region gives visibility over long stretches of the brachial pleaxus nerves.22 In our experience, using 12 MHz insonation at the middle-to-lower neck viewing between the anterior and the posterior scalene muscles best enables the supraclavicular portions of the brachial plexus to be seen. It is easiest to examine the patient in the sitting position with the head either in the neutral position or rotated away from the side of investigation by 10°–20°. Sonography of the brachial plexus is best commenced by identifying the transverse plane where the upper, middle, and lower trunks can be seen. These appear as a chain of hyperechoic nodules.23 Clarity of nerve delineation varies between individuals because of different neck lengths and the amount of fatty tissue. In individuals with short or fat necks, visualization is more difficult. We have found that a 30° coronal oblique plane in the midlower neck region behind the sternocleidomastoid muscle is a good position to start identification of the three trunks. Once the three trunks can be seen in the transverse plane as they run
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between the anterior and the posterior scalene muscles, we proceed to visualizing the proximal roots of C5–C7. It is more difficult to visualize C8 and Th1 because of the greater depth of tissue penetration and obstruction from the large vessels, and these lower roots can be seen in only about 50% of cases compared to about 90% in healthy people. The three roots C5–C7 can be explored to the level of the foraminal exit with good visualization of the extraforaminal root with longitudinal views. Imaging of the upper portions of the brachial plexus has been found to be increasingly useful in triaging of those with injury. A prospective study investigating whether HRU can improve therapeutic decisions in patients with plexus trauma found the method to be good at detecting nerve discontinuity and therefore triggering early surgical intervention.24 Both partial and complete nerve discontinuity could be frequently identified preoperatively. Nerve discontinuity is described as being associated with swelling of proximal or distal nerve “stumps.” The proximal or distal nerve segments are sometimes described as taking a “wavy” course due to the retraction of the nerve.22 Some report being able to see incomplete or complete disruption of the fascicular structure and disruption of the epineural hyperechogenic structure.24 The ability to screen for parameters which require early surgical peripheral nerve repair due to complete discontinuity or hematoma or other acute space-occupying lesions pressing on the plexus will be increasingly used to improve the outcome of measures in brachial plexus injury.6 Figure 15 shows brachial plexus injury after trauma. The upper cervical roots are well visualized and C5–C7 can be routinely assessed. Figure 16 demonstrates extraforaminal cervical root damage after a road traffic accident. Figure 17 shows greatly enlarged cervical roots typically
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Fig. 15 Brachial plexus injury. The short arrow points to a swollen C5 root (cross-sectional area 0.12 cm2, normal 0.05 cm2) in a transverse section of the interscalenar groove. The long arrow points to the swollen and distorted C6 root, which additionally shows indistinct root borders in the inferior-medial region. The image on the left shows a longitudinal view of the cervical roots (5/6).
Fig. 16 Cervical root injury: longitudinal view of the cervical roots (5/6), showing discontinuity of the C5 root with pseudomeningocoele formation at the C5 root.
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Fig. 17 Enlarged cervical roots in chronic inflammatory demyelinating polyneuropathy. The top row pictures show a longitudinal view of the C5 root (top) and the C6 root (bottom) in a patient with CIDP. Note how the nerve progressively enlarges with increasing distance from the foraminal exit. The bottom picture is a transverse section of the brachial plexus in the same patient at the scalenus gap showing enlarged C5–C7 roots.
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Fig. 17
(Continued )
seen in chronic inflammatory demyelinating polyneuropathy (CIDP). Tarsal tunnel syndrome
Figure 18 shows an enlarged posterior tibial nerve at the tarsal tunnel in a patient with typical tarsal tunnel syndrome. Other Conditions Sciatic neuropathy
The sciatic nerve is difficult to examine with standard nerve conduction techniques, and indirect diagnosis using EMG is commonly employed to document nerve damage. Over the past 10 years numerous studies — mainly from the anesthetic literature — have shown the sciatic nerve to be imageable over
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Fig. 18 Tarsal tunnel: transverse section of the posterior tibial nerve at the level of the medial malleolus in a patient with typical tarsal tunnel symptoms. The nerve adjacent to the posterior tibial vessels is considerably enlarged (cross-sectional area 0.17 cm2, normal 0.10 cm2).
most of its entirety. A subgluteal approach enables very proximal imaging of the nerve as it emerges under the piriformis muscle.11 The more distal sections of the nerve can be readily demonstrated in the distal thigh using 5–7 MHz frequency. The size of the nerve varies depending on the site and ranges between 3 and 6 mm2 in the cross-sectional area.25 We have found HRU useful for helping determine whether the sciatic nerve is still continuous and for localizing the site of the damage. Figure 19 shows an example of sciatic neuropathy which occurred during hip replacement. Inflammatory conditions Leprosy
In patients experiencing a reversal reaction with neuritis, nerves often show swelling which is gradual and fusiform,
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Fig. 19 Sciatic nerve injury: sciatic nerve injury after a knife stab, seen in a longitudinal section of the nerve at the midthigh level with an increased sciatic nerve diameter (1.18 cm) and loss of continuity of the nerve fascicles.
typically occurring proximal to osteofibrous tunnels.8 For the ulnar nerve, the site of maximum enlargement extends 8–12 cm proximal to the sulcus ulnaris, for the median nerve 6–10 cm above the flexor retinaculum, and for the posterior tibial nerve 4–10 cm proximal to the end of the medial malleolus. During reversal-reaction-induced neuritis, color Doppler shows a greatly enlarged flow detected from the perineural plexus and endoneural vessels. In longstanding multibacillary leprosy, nerves display less enlargement whilst showing profound structural abnormalities, usually with the absence of a discernible fascicular nerve structure. This is thought to be consistent with the progressive collagen deposition and endoneural contraction in chronic advanced leprosy.8
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Chronic inflammatory demyelinating polyneuropathy
Measuring the diameter of the extraforaminal roots in patients with inflammatory root disorders can be useful. Figure 17 shows enlarged extraforaminal cervical roots in a patient with CIDP. One study investigating the role of HRU in CIDP found that in 69% of cases enlarged cervical roots can be demonstrated. The degree of hypertrophy was significantly associated with the CSF protein levels.26 Multifocal motor neuropathy
Several interesting features of using ultrasonography in patients with multifocal motor neuropathy have been documented. Multiple sites of nerve enlargement can be seen along the course of the brachial plexus, median, ulnar, and radial nerves. Moreover, sonography can show abnormalities beyond those expected clinically by showing nerve enlargement without electroclinical abnormalities.27 Other Uses Sonography can aid in the detection of any disease resulting in nerve enlargement and has been proposed as a screening method for detecting patients with Charcot–Marie–Tooth (CMT) disease (type 1A).28 Figure 20 shows a patient with extremely enlarged nerves in CMT type 1A. We have found that HRU may be particularly useful for helping identify cutaneous nerves for biopsy. HRU is also becoming increasingly useful for the exact identification of dystonic or spastic muscles, making it much easier for the injector to accurately identify the muscle to be injected
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Fig. 20 Extremely enlarged nerves in CMT type 1A: transverse section of the median nerve at the midforearm level with a cross-sectional area of 1.03 cm2 (normal 0.04 cm2). Note the varying echogenicity within the nerve and the sometimes greatly enlarged individual fascicles.
with botulinum toxin or other medicines. Ultrasound-guided injection of the iliopsoas muscle with botulinum toxin has recently been found to be useful in patients with camptocormia.29 Recently, sonography has also been shown to be able to identify fibrillation in the muscles which accompany acute denervation.30 Nerve Blood Flow With the introduction of color Doppler, it has become possible to conveniently demonstrate blood flow in structures surrounding nerves or nerve blood flow itself. Hypervascularity of nerves is seen in certain entrapments (CTS) and in inflammatory nerve disease such as occurs in leprosy. Increased blood flow within the carpal tunnel as demonstrated by Doppler has been shown
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to be more sensitive than nerve conduction studies in confirming the diagnosis in those with clinically diagnosed CTS.31 The velocity of the median nerve blood flow is determined by adjusting the color window assessing the shift in the color map, with the distal section of the probe on the distal wrist crease. Since the length of the ultrasound probe is 5 cm, this much of the distal median nerve blood flow can be investigated each time. Maximal intraneural blood flow is assessed with the pulse repetition frequency (PRF) setting at 0.6 kHz and gain at 24, and maximal blood flow is identified by both the intensity and the area of the red and blue coloring scale. Measurement is made in the maximal longitudinal section so as to represent the midline of the nerve, with an incident angle of 60° to the vessel measured. Once the highest area of the intraneural median nerve blood flow on color Doppler is identified, the pulsed Doppler
Fig. 21 Hypervascularity of the median nerve in CTS. This longitudinal section of the median nerve at the proximal carpal tunnel shows an increased subepineural blood flow over a segment of 1–2 cms. This is typically seen in CTS and can be one of the earliest parameters of CTS occurring earlier than nerve conduction changes.
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window (gated at 1 mm) is positioned over the area with the greatest color intensity change, and blood flow patterns are searched for. To detect intraneural blood flow, assessment should only be performed inside the hyperechogenic perineurium. Figure 21 shows hypervascularity in the median nerve proximal to the carpal tunnel in a patient with CTS. Currently the methods of quantifying blood flow are in need of more refinement, and once this is achieved they will further promote the usefulness of sonography in the diagnosis of CTS and possibly other nerve entrapments. Color Doppler is readily used to differentiate structures surrounding nerves (Fig. 22) and is helpful in identifying the persistent median artery within the median nerve (Fig. 4). It can also be useful for delineating the extent of nerve injury in cases of acute blunt trauma (Fig. 23).
Fig. 22 Median neuropathy from a surrounding arteriovenous fistula: transverse section of the median nerve at the level of the upper forearm in a patient with chronic renal failure and a newly created arteriovenous fistula resulting in median nerve causalgia. The median nerve is surrounded and compressed by a “ring of fire” which is formed by the arteriovenous fistula as seen in the color Doppler mode.
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Fig. 23 Distal radial fracture with hypervascularity of the median nerve. The top image shows a longitudinal section of the median nerve at the distal forearm in a patient with distal radial fracture and a median nerve deficit that is more sensory than motor. Note the great increase in the median nerve (mainly extraneural) blood flow. The bottom image shows the unaffected opposite median nerve.
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1. Beekman R, Visser LH. High-resolution sonography of the peripheral nervous system — a review of the literature. Eur J Neurol 2004; 11: 305–314. 2. Erickson SJ. High-resolution imaging of the musculoskeletal system. Radiology 1997; 205: 593–618. 3. Silvestri E, Martinoli C, Derchi LE, Bertolotto M, Chiaramondia M, Rosenberg I. Echotexture of peripheral nerves: Correlation between US and histologic findings and criteria to differentiate tendons. Radiology 1995; 197: 291–296. 4. Kamolz LP, Schrogendorfer KF, Rab M, Girsch W, Gruber H, Frey M. The precision of ultrasound imaging and its relevance for carpal tunnel syndrome. Surg Radiol Anat 2001; 23: 117–121. 5. Heinemeyer O, Reimers CD. Ultrasound of radial, ulnar, median, and sciatic nerves in healthy subjects and patients with hereditary motor and sensory neuropathies. Ultrasound Med Biol 1999; 25: 481–485. 6. Peer S, Harpf C, Willeit J, Piza-Katzer H, Bodner G. Sonographic evaluation of primary peripheral nerve repair. J Ultrasound Med 2003; 22: 1317–1322. 7. Kuo YL, Yao WJ, Chiu HY. Role of sonography in the preoperative assessment of neurilemmoma. J Clin Ultrasound 2005; 33: 87–89. 8. Martinoli C, Derchi LE, Bertolotto M, et al. US and MR imaging of peripheral nerves in leprosy. Skeletal Radiol 2000; 29: 142–150. 55
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9. Karabay N, Toros T, Ademog lu Y, Ada S. Ultrasonographic evaluation of the iatrogenic peripheral nerve injuries in upper extremity. Eur J Radiol 2008. [Epub ahead of print.] 10. Padua L, Martinoli C. From square to cube: Ultrasound as a natural complement of neurophysiology. Clin Neurophysiol 2008; 119: 1217–1218. 11. Karmakar MK, Kwok WH, Ho AM, Tsang K, Chui PT, Gin T. Ultrasound-guided sciatic nerve block: Description of a new approach at the subgluteal space. Br J Anaesth 2007; 98: 390–395. 12. Nakamichi KI, Tachibana S. Enlarged median nerve in idiopathic carpal tunnel syndrome. Muscle Nerve 2000; 23: 1713–1718. 13. Mondelli M, Filippou G, Frediani B, Aretini A. Ultrasonography in ulnar neuropathy at the elbow: Relationships to clinical and electrophysiological findings. Neurophysiol Clin 2008; 38: 217–226. 14. Yoon JS, Walker FO, Cartwright MS. Ultrasonographic swelling ratio in the diagnosis of ulnar neuropathy at the elbow. Muscle Nerve 2008; 38: 1231–1235. 15. Creteur V, Bacq C, Fumiere E, Bissen L, Delcour C. Sonography of peripheral nerves. Part II: Lower limbs. J Radiol 2007; 88: 349–360. 16. Creteur V, Bacq C, Widelec J. Sonography of peripheral nerves. Part I: Upper limb. J Radiol 2004; 85: 1887–1899. 17. Peeters EY, Nieboer KH, Osteaux MM. Sonography of the normal ulnar nerve at Guyon’s canal and of the common peroneal nerve dorsal to the fibular head. J Clin Ultrasound 2004; 32: 375–380. 18. Visser LH. High-resolution sonography of the common peroneal nerve: Detection of intraneural ganglia. Neurology 2006; 67: 1473–1475. 19. Park JW, Kim DH, Hwang M, Bun HR. Meralgia paresthetica caused by hip-huggers in a patient with aberrant course of the lateral femoral cutaneous nerve. Muscle Nerve 2007; 35: 678–680.
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20. Gofeld M, Christakis M. Sonographically guided ilioinguinal nerve block. J Ultrasound Med 2006; 25: 1571–1575. 21. Quinn TJ, Jacobson JA, Craig JG, van Holsbeeck MT. Sonography of Morton’s neuromas. Am J Roentgenol 2000; 174: 1723–1728. 22. Graif M, Martinoli C, Rochkind S, et al. Sonographic evaluation of brachial plexus pathology. Eur Radiol 2004; 14: 193–200. 23. Yang WT, Chui PT, Metreweli C. Anatomy of the normal brachial plexus revealed by sonography and the role of sonographic guidance in anesthesia of the brachial plexus. Am J Roentgenol 1998; 171: 1631–1636. 24. Gruber H, Glodny B, Galiano K, et al. High-resolution ultrasound of the supraclavicular brachial plexus — can it improve therapeutic decisions in patients with plexus trauma? Eur Radiol 2007; 17: 1611–1620. 25. Saranteas T, Kostopanagiotou G, Paraskeuopoulos T, Vamvasakis E, Chantzi C, Anagnostopoulou S. Ultrasound examination of the sciatic nerve at two different locations in the lateral thigh: A new approach of identification validated by anatomic preparation. Acta Anaesthesiol Scand 2007; 51: 780–781. 26. Matsuoka N, Kohriyama T, Ochi K, et al. Detection of cervical nerve root hypertrophy by ultrasonography in chronic inflammatory demyelinating polyradiculoneuropathy. J Neurol Sci 2004; 219: 15–21. 27. Beekman R, van den Berg LH, Franssen H, Visser LH, van Asseldonk JT, Wokke JH. Ultrasonography shows extensive nerve enlargements in multifocal motor neuropathy. Neurology 2005; 65: 305–307. 28. Martinoli C, Schenone A, Bianchi S, et al. Sonography of the median nerve in Charcot–Marie–Tooth disease. Am J Roentgenol 2002; 178: 1553–1556. 29. von Coelln R, Raible A, Gasser T, Asmus F. Ultrasound-guided injection of the iliopsoas muscle with botulinum toxin in camptocormia. Mov Disord 2008; 23: 889–892.
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30. Pillen S, Nienhuis M, van Dijk JP, Arts IM, van Alfen N, Zwarts MJ. Muscles alive: Ultrasound detects fibrillations. Clin Neurophysiol 2009; 120(5): 932–936. 31. Mallouhi A, Pulzl P, Trieb T, Piza H, Bodner G. Predictors of carpal tunnel syndrome: Accuracy of gray-scale and color Doppler sonography. Am J Roentgenol 2006; 186: 1240–1245.
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Index
Brachial plexus
Peroneal neuropathy 38 Radial neuropathy 35, 36 Tarsal tunnel syndrome 46 Ulnar nerve at the wrist 26, 36
11, 42–45, 49
Carpal tunnel syndrome 27, 32 Cervical roots 12, 43–45, 49 Charcot–Marie–Tooth neuropathy 28, 33 Chronic inflammatory demyelinating polyneuropathy (CIDP) 45, 46, 49
Honeycomb structure Ilioinguinal nerve
4, 15
13, 41
Lateral femoral cutaneous nerve 6, 14, 39, 41 Leprosy 8, 47, 48, 50
Entrapment neuropathies — common 27 Carpal tunnel syndrome 27, 32 Ulnar neuropathy at the elbow 32, 34 Entrapment neuropathies — less common 33 Ilioinguinal nerve 13, 41 Lateral femoral cutaneous nerve 6, 14, 39, 41 Morton’s neuroma 41
Median neuropathy 52 Medical antebrachial nerve 10 Morton’s neuroma 41 Multifocal motor neuropathy 49 Nerve blood flow Nerve trauma 8
59
50, 51
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High-Resolution Ultrasonography for Peripheral Nerve Diagnostics
Peripheral nerve characteristics — diseased 6 Peripheral nerve characteristics — healthy 3 Peroneal neuropathy 38 Posterior interosseous nerve 37 Radial neuropathy
35, 36
Sciatic neuropathy 46, 47 Superficial peroneal nerve 20
Superficial radial nerve 36, 37 Sural nerve 6, 22
21,
Tarsal tunnel syndrome
46
Ulnar nerve at the hand 36 Ulnar nerve luxation 33, 35 Ulnar neuropathy at the elbow 32, 34
