Microneurosurgical Atlas

Kenichiro Sugita

Microneurosurgical Atlas With the Assistance of Shigeaki Kobayashi

With 456 Figures (Including 202 Colored Illustrations by the Author)

Springer-Verlag Berlin Heidelberg NewYork Tokyo

Preface The operations I perform every year never fail to provide me with new insights into the practice of neurosurgery, and lead me not infrequently to new ideas concerning surgical techniques or equipment. The present work is a kind of surgical diary of a neurosurgeon who, he would like to think, is ever improving his skills. Although there have already been many distinguished publications, the book will, I believe, be of particular help to young neurosurgeons. I perform only a hundred or so operations a year, selected because of their technical difficulty. As difficult or unusual cases are rather few, it is important that every practising neurosurgeon should record those he encounters in exact detail. I would like especially to suggest to young surgeons that they draw detailed operative pictures of such cases, as I have done. The collection will become an important and valuable private text in the future. In the past 18 years I have performed about 2000 operations under the microscope. I have selected for this atlas about 100 of the cases I have dealt with in the past 8 years. I treat the technical problems of each operation in considerable de-tail, and I have included all my unsuccessful cases as they taught me more than the successful ones. I drew each picture of the operative findings from memory soon after the opera-tion, without the aid of photographs or videotapes, and there may therefore be occasional minor inaccuracies in the anatom-icai relationships or size. In particular, the size of an aneurysm or tumor may sometimes have been represented larger than in actually was; this is a common problem in immediate postoperative drawings. The operating fields have been recon-

structed as they would appear with considerable retraction of the brain, though the actual field was usually no more than one third or one fourth of that shown; cotton patties used for covering the cortex are omitted in the drawings. In the majority of cases I performed the operation with my associates, all of whom have more than 10 years' clinical experience in neurosurgery. Such splendid teamwork as exists in our group is one of the most important factors in successful surgery, and for this purpose our system of stereoscopic assistant microscopes is indispensable. I wish to extend my warmest thanks for their constant support to all my associates in the university hospitals of Shinshu and Nagoya and in the affiliated hospitals of Aizawa, Showainan, Seguchi, Ko-moro, Shinonoi, Kobayashi, Suwa and Nagoya Red Cross. Chukyo, Ohgaki, Yokkaichi, Ichinomiya, Tajimi, Tosei, Oka-zaki, Handa, Anjo, Nishio, Toyohashi, and Saiseikai-Shi-zuoka. To my mentors, Dr. YOSHIYA MIURA, Prof. NAOKI KAGEYA^IA. Prof. GENYO MITARAI, Prof. KEIICHI MURATA, Prof. HAJIME NAGAI and Prof. OSAMU SATO at Nagoya University and Prof. TRAUGOTT RIECHERT and Prof. ROLF HASSLER at the University of Freiburg, I owe a great and long-standing debt of gratitude. My thanks are due also to Mr. P.E. DAVENPORT of Shinshu University at editing the English and to Mr. JORG KUHN of Springer Verlag in Heidelberg, a medical illustrator of unique talent, for valuable suggestions. Lastly I wish to thank the publishers for their friendly cooperation in the preparation and publication of the work. KENICHIRO SUGITA

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Contents I General

VII

Considerations

1 Patient's Position . . . . . . . . . . . . . . .

3 Anterior Communicating Artery Aneurysm 1

2 Skin Incision and Bone Flap . . . . . . . . . .

2

3 Retraction of the Brain . . . . . . . . . . . . . 4 Preservation of Bridging Veins . . . . . . . . . .

2 2

II Instrumentation

Case 15 Direct Retraction of Body (rt) . . . . . . . Case 16 Temporary Clipping (rt) . . . . . . . . . Case 17 Double Clipping: Clip Blade Covered with Silastic Tube (rt) . . . . . . . . . . . . . Case 18 Double Clipping (rt) . . . . . . . . . . . Case 19 Two Cases with Ring Clip (It) . . . . . . . Case 20 Giant Aneurysm (It) . . . . . . . . . . .

44 46 48 50 52 54

4 Distal Anterior Cerebral Artery Aneurysm

П1 Aneurysm

General Considerations in Surgery of Aneurysms . A

General Considerations . . . . . . . . . . . . . .

56

Aneurysms of the Anterior Circle of Willis . . .

1 Operating Microscope . . . . . . . . . . . . .

3

2 Operating Chair . . . . . . . . . . . . . . . 3 Operating Table . . . . . . . . . . . . . . . 4 Instrument Table . . . . . . . . . . . . . . . 5 Head Frame and Multipurpose Head Frame . . . 6 Self-Retaining Retractor and Tapered Brain Retractor (Spatula) . . . . . . . . . . . . . .

4 4 5 6

7

8 Suction . . . . . . . . . . . . . . . . . . . 9 Silver Dissector . . . . . . . . . . . . . . . .

7 9

10 Four-Pronged Hook . . . . . . . . . . . . . . 11 Cotton Patty . . . . . . . . . . . . . . . . .

9 9

12 Microscope Sterilization . . . . . . . . . . . .

9

1 Carotid Artery Aneurysm . . . . . . . . . . .

1 0 15 16 16

1 8

20 22 24 26

2 Middle Cerebral Artery Aneurysm

56 58 60

6

7 Bipolar Forceps . . . . . . . . . . . . . . .

Case 1 Ophthalmic Artery Aneurysm: Optic Nerve Retraction (rt) . . . . . . . . . . . . . Case 2 Triple Aneurysm (rt) . . . . . . . . . . Case 3 Carotid Bifurcation Aneurysm (rt) . . . . . Case 4 Medially Projecting Aneurysm: Clipping and Puncture (rt) . . . . . . . . . . . . . . Case 5 Ventrally Protruding Aneurysm Obliterated with Ring Clip (It) . . . . . . . . . . . Case 6 Aneurysm with Trigeminal Neuralgia (rt) . . Case 7 Wide-Necked Aneurysm Obliterated with Two Ring Clips (It) . . . . . . . . . . . . . Case 8 Large Aneurysm Obliterated with Two Ring Clips (It) . . . . . . . . . . . . . . . . Case 9 Large Aneurysm Obliterated with Three Clips (rt) . . . . . . . . . . . . . . . . . .

Case 21 Prevention of Narrowing of the Parent Artery (Two Clips) (rt) . . . . . . . . . . . . . Case 22 Prevention of Narrowing of the Parent Artery (Three Clips) (rt) . . . . . . . . . . . . . Case 23 Large Aneurysm (Two Clips) (rt) . . . . . .

28

Case 10 Large Aneurysm Obliterated with Two Clips 3 (rt) . . . . . . . . . . . . . . . . . . . 34 Case 11 Giant Aneurysm Obliterated with Two Long Clips (It) . . . . . . . . . . . . . . . . 36 Case 12 Large Aneurysm: Body Clipping (It) . . . . 38 Case 13 Dilatation of the Trifurcation: Clipping and

В Aneurysms of the Posterior Circle of Willis

General Considerations for Basilar Artery Aneurysms

62

1 Basilar Bifurcation Aneurysm . . . . . . . . . .

66

Case 24 Anteriorly Projecting Aneurysm (rt) . . . . Case 25 Retraction of Three Arteries (rt) . . . . . . Case 26 Clipping Between Perforators (rt) . . . . . . Case 27 Application of Straight Ring Clip (rt) . . . . Case 28 Clipping Through the Opticocarotid Space (rt) Case 29 Puncture of Body (rt) . . . . . . . . . . . Case 30 Undipped Aneurysms (rt) . . . . . . . . .

66 68 70 72 74 76 78 82

2 Basilar-Superior Cerebellar Artery Aneurysm

Case 31 Case 32 General Considerations . . . . . . . . . . Case 33 Double Clipping (rt) . . . . . . . . . . . 82 Case 34 Intraoperative Shortening of the Blade (rt) . . 84 Direct Retraction of Aneurysm (It) . . . . . 86 Case 35 Approach Above the Carotid Artery Case 36 Bifurcation (rt) . . . . . . . . . . . . . 88 Undipped Aneurysm with Bilateral Approach 90 Distal Superior Cerebellar Artery Aneurysm (It) . . . . . . . . . . . . . . . . . . . 92

82

3 Proximal Posterior Cerebral Artery (PI) Aneurysm Case 37 Trapping of PI (rt) . . . . . . . . . . . . 94 Case 38 Angled Ring Clip: Associated with AVM (It) 96 Case 39 Associated with Agenesis of the Carotid

Artery (It) . . . . . . . . . . . . . . . . 98 4 Distal

Posterior Cerebral Artery Aneurysm Case 40 Removal of the Parahippocampal Gyrus (rt) 102 Case 41 Double Clipping in a Case Associated with TIA (It) . . . . . . . . . . . . . . . . . 104 Case 42 Giant Aneurysm: Cutting and Double Clipping (rt) . . . . . . . . . . . . . . . 106

VIII

Contents

5 Basilar Trunk Aneurysm

7 Posterior Fossa AVM

Case 43 Double Aneurysm via Transsylvian Approach (rt) . . . . . . . . . . . . . . . . . . . 108 Case 44 Direct Retraction of the Pons (It) . . . . . . 110 Case 45 Vertebral Union (rt) . . . . . . . . . . . 112 Case 46 Giant Aneurysm: Undipped (rt) . . . . . . 114

Case 73 In the Vermis: Concorde Position (Bilateral) 172 Case 74 Giant AVM in the Vermis (Bilateral) . . . . 1 7 4 Case 75 In the Tonsil (rt) . . . . . . . . . . . . . 176

6 Vertebral Artery Aneurysm

Case 76 Feeding from the Superior Cerebellar Artery (rt) . . . . . . . . . . . . . . . . . . . 178 Case 77 In the Cerebellopontine Angle (It) . . . . . 180 Case 78 Cerebellar . . . . . . . . . . . . . . . . 182

8 Hemangioma . . . . . . .

General Considerations . . . . . . . . . . . . . . 1 1 6 Case 47 Bayonet Clip for a Large Aneurysm (rt) . . . 118 Case 48 Clipping by Interchange of Two Clips (It) . . 120 Case 49 Aneurysm Close to a Midline (rt) . . . . . 122 Case 50 Aneurysm Close to a Midline (It) . . . . . . 124 Case 51 Body Clipping (rt) . . . . . . . . . . . . 126 Case 52 Body Clipping (Dissecting?) (rt) . . . . . . 128 Case 53 Semifusiform Pointing Toward the Approach (It) . . . . . . . . . . . . . . . . . . . 130 Case 54 Ring Clip for Preservation of a Perforator (It) 132 Case 55 Large Fusiform Aneurysm with Three Ring Clips (It) . . . . . . . . . . . . . . . . 134

General Considerations . . . . . . . . . . . . . . 1 Temporal Lobe AVM . . . . . . . . . . . . .

136 138

144

Case 59 Precentral: Small Residual (rt) . . . . . . . Case 60 Close to Broca Area (It) . . . . . . . . . . Case 61 Under Broca Area (It) (Parasylvian Fissure) Case 62 Large AVM (It) . . . . . . . . . . . . . Case 63 Large AVM: Breakthrough (rt) . . . . . . Case 64 Large AVM: Breakthrough (rt) . . . . . .

3 Interhemispheric AVM

. . . . . . . .

144 146 148 150 152 154 156

Case 65 Anterior Portion (rt) . . . . . . . . . . . 156 Case 66 Anterior Portion: Residual Nidus (rt) . . . . 1 5 8

4 Intraventricular AVM

. . . . . . . . . .

160

General Considerations . . . . . . . . . . . . . .

160

General Considerations . . .

f. . . . . . . . . .

1 Anterior Skull Base Meningioma . . .

185 188

Case 79 Optic Nerve (rt) . . . . . . . . . . . . .

188

Tuberculum (It) . . . . . . . . . . . . . Tuberculum (Medial) (Bilateral) . . . . . . Tuberculum (rt) . . . . . . . . . . . . . Tuberculum (rt): Metal Shield . . . . . . .

190 192 194 196

2 Sphenoidal Ridge Meningioma . . . . . 200

Case 56 Anterior Portion (It) . . . . . . . . . . . 138 Case 57 Anterior Portion with Aneurysm (It) . . . . 1 4 0 Case 58 Posterior Portion (It) . . . . . . . . . . . 142

2 Central Area AVM

178

V Meningioma

Case 80 Case 81 Case 82 Case 83

IV Arteriovenous Malformation

172

Case 67 Anterior Portion of the Ventricle (It) . . . . 1 6 0 Case 68 Posterior Portion of the Ventricle (It) 162

5 AVM in the Basal Ganglia . . . . . . . . . . . 164 Case 69 Feeding from Posterior Communicating Artery (rt) . . . . . . . . . . . . . . . . . . . Case 70 Feeding from Ml, Al, and PCA (It) . . . .

164 166

6 AVM Around the Tentorial Edge . . . . . . . . . Case 71 Above Quadrigeminal Plate (rt) . . . . . . Case 72 On Lateral Pons (It) . . . . . . . . . . .

168 168 170

Case 84 Over Orbital Area (It) . . . . . . . . . . Case 85 Anterior Temporal Fossa (rt) . . . . . . . Case 86 Huge Meningioma (rt) . . . . . . . . . .

3 Intraventricular Meningioma

. . . .

200 202 204 206

Case 87 In Trigonum (rt and It) . . . . . . . . . .

206

4 Parasagittal and Falx Meningioma

. . .

Case 88 Anterior Parasagittal Sinus (Bilateral) . . . . Case 89 Unilateral Falx (rt) . . . . . . . . . . . . Case 90 Bilateral Falx (rt) . . . . . . . . . . . .

208 208 210 212

5 Tentorial and Posterior Fossa Meningioma General Considerations . . . . . . . . . . . . . . 2 1 4

Case 91 Anterior Tentorium (It) . . . . . . . . . .

216

Case 92 Medial Tentorium and Clivus: Involvement of Vth Nerve (rt) . . . . . . . . . . . . . . 218 Case 93 Medial Tentorium and Clivus: Drilling off Pyramid (rt) . . . . . . . . . . . . . . . 220 Case 94 Medial Tentorium: Combined with Suboccipital Approaches (rt) . . . . . . . . 222 Case 95 Large Medial Tentorium: Sacrifice of Posterior Choroidal Artery (It) . . . . . . . 224 Case 96 Bilateral Occipital Lobes: Visual Cortex (rt) 226 Case 97 Posterior Tentorium (rt) . . . . . . . . . 228 Case 98 Posterior Tentorium (It) . . . . . . . . . . 230 Case 99 Lateral Pyramid (It) . . . . . . . . . . . 232

Contents

VI Neurinoma and Other Brain Tumors

IX

4 Glioma . . . . . . . . . . . . . . . . . . . .

248

General Considerations . . . . . . . . . . . . . .

248 249 255

1 Acoustic Neurinoma . . . . . . . . . . . . . .

237

Case 103 Gliomas in the Thalamus and Adjacent Regions . . . . . . . . . . . . . . . .

2 Trigeminal Neurinoma . . . . . . . . . . . . .

244

Case 104 Optic Glioma . . . . . . . . . . . . . .

Case 101 Subtemporal Approach (rt) . . . . . . . .

244

References

3 Epidermoid Tumor . . . . . . . . . . . . . . .

246

Case 102 Cerebellopontine Angle (It) . . . . . . . .

246

I General Considerations 1 Patient's Position

The position of the patient's head is of enormous importance in the operation under an operating microscope. There are two points to which particular attention must be paid, One is the height of the patient's head, which should be above the level of the heart in order to lower both venous and intra-cranial pressure. We make it a rule in the supine and prone positions to elevate the upper half of the operating table by about 30 degrees; raising the head more than 45 degrees runs the risk of air embolism. The second point is that the main operating procedure can and should be performed with the microscope at a constant perpendicular visual axis by rotating and/or tilting the patient's head. Working under a microscope at an oblique angle for a long period is very tiring. Intraopera-tive correction of the head position to either side can be easily done by rotating the head frame or tilting the operating table sideways. However, it is difficult to correct the degree of flexion or extension of the head once surgery starts, and it is therefore important to position the head properly in the vertical axis prior to surgery: the chin up or down in the supine position, and the vertex up or down in the lateral position (Figs. 1-1 and 1-2). Fig. 1-1. Usual positioning of a patient. The upper portion of the

30 ±5'

operating table is elevated 30+5 degrees Fig. 1-2. a Importance of patient's head: chin up or down, b In order to see the base of the skull, the surgeon often has to change the observation angle from A to В during surgery. When looking through the microscope at angle A the eye-piece can be changed to a straight I type, but when observation from В is necessary the surgeon has to take up a very awkward position as if he is looking at his own stomach. In this case he can either move to the side or lower the I patient's head, or use a rectangular eye-piece if one is available

General Considerations 2 Skin Incision and Bone Flap

The skin incisions for different procedures have been discussed by many authors. I would just add here that we should whenever possible preserve the superficial extracranial arteries because bypass surgery between extra- and intracranial arteries may be necessary later in rare cases. The smaller the skin incision and bone Пар are, the shorter will the operating time be. We should avoid making an unnecessarily large bone flap, though it is true that an intraoperative problem such as sudden brain edema will be more severe with a smaller craniotomy. When approaching the skull base, it is very important thai the bone edge of the lateral side be removed as far as possible. and the lateral extent of the craniotomy should be the longer.

uously for more than 10 min, the retractor should be moved to another part of the cortical surface or released for a few minutes. Such intermittent retraction is especially important in operations on elderly patients and around critical areas such as the pons and medulla. The force and distance of retraction are of course of similar importance. It is better to use two or three tapered brain retractors than an ordinary non-tapered one with a tip wider than 8 mm. The surgeon must not forget to feel the consistency of the brain with his fingers while fixing a brain retractor to the self-retaining retractor. When some hardness is fell through the retractor. local brain edema is likely to appear postoperatively. The surgeon has to learn to judge the safety range of retraction with his fingers.

3 Retraction of the Brain

4 Preservation of Bridging Veins

Reduction of brain volume and gentle retraction of the brain are two important tactics. Administration of diuretics such as Mannitol, drainage of ccrcbrospinal fluid and hyperventila-tion are commonly used techniques which it is unnecessary lo describe here. When the patient is elderly, there is usually plenty of space in the operating field even before brain retraction because the brain tends to be atrophic. Here, however, there is a particular danger of postoperative complications: the brain of an elderly patient is hard and inelastic, so that even minimal brain retraction may result in postoperative brain edema, contusion, or intracerebral hcmatoma. The brain of a young patient, in contrast, is usually very tight at the beginning of the operation but gradually becomes slack thanks to its elasticity, and generally tolerates stronger retraction well. The importance of gentle retraction increases w;ith the age of the patient. Intermittent retraction using tapered brain retractors is recommended. Beside specific techniques such as dissection around an ancurysm and preservation of the facial nerve in acoustic neurinoma surgery, gentle yet adequate retraction of the brain is the most decisive general factor in minimizing postoperative complications. When the brain has to be retracted contin-

It is clear that preservation of a big vein can improve operative morbidity especially in those cases where excessive brain retraction is required in combination with preexisting edema or where the vein is draining an arteriovenous malformation. We have used a method for preserving large bridging veins intraoperative]у by_stripping them from the cortex. After an ordinary craniotomy and dural opening, and before starting brain retraction, the arachnoid and the cortex around a big bridging vein are dissected free for a length of 10 to 20 mm distally (to the brain side) from the cortical edge. The length of stripped vein depends upon the width of brain retraction necessary for the subsequent procedure. Enough subarachnoid space is thus obtained, and the portion of the vein close to the sinus could easily be stripped merely by dissecting the arachnoid. However, the distal portion of the vein usually remains tightly adherent to the arachnoid. Therefore, it is usually safer to avoid injury to the vein wall by sucking the smallest possible portion of the cortex, if it is not a critical area such as a motor strip, and small tributaries of the vein are occasionally sacrificed if necessary. Retraction of the brain slightly distant from the vein then makes visualization of a deep-seated lesion possible without sacrificing the vessel (Fig, T-

3).

II Instrumentation 1 Operating Microscope The operating microscope is one of the most important instruments in modern neurosurgery. The history and technical aspects of the microscope have been discussed in many papers; here I would just briefly stress five important properties which the instrument must possess for neurosurgical application: (1) The objects can be seen clearly and sharply through the lens system. (2) Illumination is strong and the illuminated field wide. Multiple sources of illumination are especially useful in neurosurgical applications because one beam may sometimes be obstructed in a deep and narrow field by a bone Fig П-l. Operating microscope Nagashima

Pre II-I. Operating microscope Nagashima Ty-pe III:: with pedal-controlled X-Y shifter and elec-tromagnetic suspension lock and a pair of stereo scopic assistant microscopes

Ty-pre IV; with pedal-controlled X-Y shifter and elec-tromagnetic spension lock. Upper: A usual as-sambly with a pair of stereoscopic assistant micro-scopes.Lower: Set-up of beam splitter for a nar-now operating field such as in

edge or other object. (3) Rotation and tilting of the microscope body can be performed easily and quickly. (4) Vertical shifting can be done at two different speeds: fast and slow. (5) Accessory systems can be implemented easily when needed. Today each surgical speciality, such as ophthalmology, otology, or orthopedics, has a different type of operating microscope built to fit the requirements of its own field. An operating microscope designed specifically for neurosurgical purposes is no less necessary. Fifteen years ago I designed an operating microscope, type I, with two stereoscopic assistant scopes. A stereoscopic view is essential for an assistant surgeon who wants not only to gain the same experience as the

transsphenoidal pituitary surgery.

Instrumentation chief surgeon but also to actually assist him. Usually I can operate with my own two hands and those of up to two assistants, which makes operative procedures quick and efficient. Such multi-handed surgery is impossible with a conventional non-stereoscopic assistant scope. With the use of these stereoscopic scopes we have developed excellent teamwork in our surgery. Our newly designed microscope, types III and IV, has two new suspension systems with a remote-controlled threedimensional shifting system and a magnetic lock system for all joints of the suspension. With the aid of the three-dimensional microshifter controlled by a footpedal we can adjust the focus of the microscope and keep the operative target in the center of the microscopic field without using our hands. When we need to move the microscope over a distance or to an oblique angle the magnetic lock joints make rapid adjustment of the microscopic focus possible. All future operating microscopes for neurosurgery should be equipped with these systems (Figs. II-l and II-2). 2 Operating Chair

introduced 14 years ago, and is still in use at some of our affiliated hospitals. Our newly designed chair, type II, can be called a floating operating chair. It is suspended by a horizontal arm attached to a pole in the floor. The suspension arm rotates like a fan around the main stand within a range of 180 degrees, and its length can be varied from 50 to 100 cm. All joints of the suspension system have magnetic locks. Up-and-down motion of the chair is controlled by a pedal. All joints other than that for vertical motion are loosened when another pedal is held down so that the chair can be moved smoothly whenever the surgeon wishes. The chair and footplate are in one piece. There are sixteen pedal switches in the footplate, all arranged from the viewpoint of human engineering, and the necessary footwork can be mastered in about 30 min. The pedals emit different musical sounds while pushed, which enables quick correction if the wrong pedal is pushed and also informs the assistant surgeons and scrub nurse which pedal is pushed (Fig. II-3).

A good operating chair is an important piece of equipment, although some neurosurgeons prefer to operate standing. If a person wants to write neatly it is necessary that he be seated. If he wants to write comfortably for some length of time, the chair or stool must be positioned properly. A comfortable chair allows a surgeon to operate efficiently with much less fatigue. The indispensable conditions for an operating chair are easy up-and-down motion, easy mobility on the floor, a built-in footplate, and proper arrangement of multiple foot-switches. An operating chair of our design, type I, was first

The operating table of our design, Mizuho 7000, has three advantages. The table can be lowered to 40 cm above the floor, and thus allows us to keep the patient's head higher than his heart in various operating positions such as the lateral, Concorde and sitting, while at the same time keeping his head at a suitable height in relation to the surgeon. There is a large space under the head portion of the table because the supporting base is toward the foot of the table, so the surgeon's chair and the assistants' feet do not get in each other's way. The greatest advantage of the table is that it

3 Operating Table

Fig. II-3. a Floating chair (Mizuho); 16 pedal switches on the footplate, b Operating chair type I (Nagashima)

Fig. П-4. Operating table (Mizuho); the lowest position is 40 cm from the floor, horizontal microshifting controlled by pedal is optional

is equipped with a remote-controlled microshifter for the hori-zontal plane. With the aid of this an object under the microscope can be kept in the center of the microscopic field by pedal control; the system is especially useful when the operating microscope in use is not equipped with a remote control system.. The remote control pedals for the operating table are built into the footplate of the operating chair (Fig. II-4). Instrument Table The importance of the instrument table has not been stressed in the past. It would seem to be a matter of more concern to the scrub nurse than to the surgeon. However, it is clear that an instrument table that over-rides the operating table is more convenient than one placed at its side. Supporting poles for the over-riding table should be placed on one side of the operating table only. Because we need to change the patient's head level frequently during the operation, the table must be easily movable. The height of the instrument table and nurse platform of our design are electrically changeable. On the bottom surface of the instrument plate is an alarm system to warn of contact with the patient or other objects, such as the respiratory tube. On the platform there is a movable chair, which lessens the fatigue of the scrub nurse (Fig. П-5).

Fig. II-5. Instrument table (Mizuho); heights of the table and platform are electrically controlled by pedal switches. Note the chair for scrub nurse. Arrow: Safety alarm for contact

Instrumentation 5 Head Frame and Multipurpose Head Frame (Sugita Frame)

The frames enable fine retraction work of the brain under the operating microscope. We feel that it is impossible to operate properly without this system, which consists of two main semicircular frames and various accessories. A basic frame for fixing the patient's skull has six holes for skull fixation pins. Ordinarily, we use four pins in appropriate holes. Such fourpoint fixation is better than the three-point fixation of the Mayfield system because each pin exerts less force and yet the fixation of the patient's head is firmer. With our system the patient's head can be rotated intraoperatively even while brain retractors are in use. The multipurpose semicircular frame is applied at a right angle to the above base frame; its plane is set almost horizontal to the floor. The following accessories are attached to it: sliding bases for self-retaining retractors, instrument boxes holding forceps and suction, L-shaped handrests which can be used also as bases for self-retaining retractors, and a handrest and slim semicircular frame for the opposite side of the multipurpose frame; the slim frame has a plate for cotton patties and anchors for spring hooks. With the aid of this assembly more than four self-retaining retractors can be safely based on sliding bases and handrests round a full 360 degrees. The sliding base is very convenient for fixing the self-retaining retractor in an ideal curve and for keeping the retractor tip precisely and safely in the depth of the operating field. The handrest is used for the left hand of a right-handed surgeon in a long operation where fine suction work is necessary, for

Fig. II-6. Sugita mutipurpose head frame (Mizuho); (A) basic frame. (B) handrest and a base (Q for a selfretaining retractor. (D) Instrument holder. (£) Semicircular frame for a cotton plate (G) and skin flap hooks (F). (If) Skull frame with 4 pins. (7) Suspension connected with operating table. (K) Selfretaining retractor. (L) Tapered spatula. (M) Lake retractor. (N) Sliding base for selfretaining retractor

instance the dissection around an aneurysm; it is also occasionally used for the right hand when clipping in an unusual direction (Fig. II-6).

6 Self-Retaining Retractor and Tapered Brain Retractor (Spatula)

In the previous section the importance of brain retraction was noted. The self-retaining retractor and multipurpose head frame are indispensable tools for placing the tapered tip of the retractor with precision. The self-retaining retractor, such as that of Leyla, is one of the most important instruments introduced into modern neurosurgery. Our newly designed selfretaining retractor is made of titanium, which has reduced the weight to 170 g, about half that of a conventional retractor made of stainless steel. Its shape is noteworthy: it is tapered, with a base of 15 mm and an end of only 9 mm. Consequently, the fixation force at the base is about half that of a conventional self-retaining retractor and yet the tip can be fixed exactly and steadily at critical brain tissues (Fig. II-7). We have also introduced a tapered spatula in three widths: 2, 4 and 6 mm at the tip. The base of all the spatulas is about 20 mm wide. The tapered shape of the tip means that less brain tissue is retracted in the depths close to a critical area than with a usual retractor. The finer the retraction becomes the more such tapered retractors are needed. In the past we developed a tapered retractor the edges of which were bent over and which was quite flexible. Although cortical injury could be

7 Bipolar Forceps

Fig. II-7. Light-weight tapered self-retaining retractor made of titanium (Mizuho); 160 g

avoided with the bent edge, it disturbed the surgeon's view. It is very important to be able to retract by as little as 1 or 2 mm in an approach under the microscope. Generally we should apply a wider tapered retractor or an ordinary one at the initial stage of an approach to the base of the skull and then select the finest one for retraction around vital structures such as cranial nerves, vessels and aneurysms. The cortex and other important structures must be covered with cotton patties when retracted, though the patties are omitted in most of the pictures in this atlas to show the anatomical relationships in detail (see Fig. II8A, В, С).

Many kinds of bipolar forceps are now commercially available. It is important that a surgeon get accustomed to forceps of various shapes at the tip: sharp and dull, straight and curved. It is recommended that electrically insulated forceps (except for the tips) be used because they are likely to come into contact with brain retractors or brain tissue where electrical leakage could occur. One of the problems that occur when using bipolar forceps is adhesion of clots at the tips. Many attempts have been reported to lessen this: saline irrigation, use of a special metal with high heat-conduction at the tip. implanting a thermocouple in the tip with a feed-back control system or an impedance feed-back system. I always have a spare pair of forceps connected to a generator standing by, so that those that become clotted can be cleaned immediately by the scrub nurse. We now use bipolar forceps with tips of a metal that has high heat conductance because tissue adherence caused by coagulation is less with such a metal (Mizuho Co.). The output current should be changed frequently during procedures in critical areas and vascular surgery. For this purpose we use a small sterilized output controller which is controlled inside the operating field by an assistant surgeon (Tokairika Co.).

8 Suction }

A suction is another important tool, especially in aneurysm surgery. An inexperienced neurosurgeon tends to concentrate his attention on his dominant hand holding the forceps or dissector, but he should not forget that the suction in his other hand may accidentally poke an aneurysm, resulting in rupture. Suction tubes must possess a finger hole with which

A

Fig. II-8. Tapered brain retractor. (A) 6 mm. (B) 4 mm, (C) 2 mm in width at tip. (D, E) ho^k. (F) Flexible silver dissector (Mizuho)

Instrumentation the sucking pressure can be controlled. A fine tube of less than 1 mm in diameter should be used when operating around an aneurysm or critical tissues. We have designed a special suction hand-piece with a counterbalance and easily exchangeable suction tips. The counterbalanced hand-piece lessens the fatigue and pain in the fingers which develop during a long operation, and is less likely to cause accidental injury to an aneurysm or important tissues because it is balanced so that the tip does not dip under its own weight. Various shapes and lengths of suction tip can be easily exchanged on the handpiece, thus avoiding delay when a tip becomes obstructed (Fig. II-9, upper). In contrast to fine suction work such as that in aneurysm

a tumor. A very large suction with a diameter of 4 mm is held in the dominant hand and an ordinary one in the other. The large suction can grossly remove the tumor mass like an ultrasonic suction while the ordinary one is used for sucking blood and keeping the operating field clean. One must be very careful when using such a large suction not to bring it close to critical structures. It is usually used only for intra-capsular decompression (Fig. II-9, lower). The tear-drop tip is undoubtedly useful to avoid injury to neighbouring tissues, but the additional width of this kind of tip impedes very delicate suction work such as the dissection around an aneurysm. When ordinary tips are used they should be checked under a microscope at least once a month because the edge often

surgery, we often use a suction in each hand when removing

becomes irregular and sharp; such inspection

Fig- П-9. Balanced^suction (Mizuho). The 4 mm large ordinary suction (lower in the upper figure) used for special purpose (see text)

Fig. 11-10. Microscope sterilizer (Chiyoda)

is especially important for a small suction usually used for suction and dissection around aneurysms.

9 Silrer Dissector

Rather too many kinds of dissector are available now. Fifteen years ago I designed a flexible silver dissector for aneurysm surgery which we have always found to be very useful and safe. Its tip and edge can easily be reformed with emery paper into any desired shape, sharp or dull, narrow or wide. Probably the more experienced a surgeon becomes, the sharper he vants the tip of the dissector to be (Fig. II-8 F).

11 Cotton Patty

The cotton patty is an important tool used by all neurosurgeons. We use two types: hard Codman patties and soft cellulose patties (Bemsheets). Each comes in different sizes. The former is used for the protection of the cortical surface because it is thick and hard with less adhesiveness to the tissue. The brain must always be completely covered with cotton patties, though they are not shown in the atlas. The Bemsheets, which are made from pure cellulose, have the same appearance as cotton. They are used for dissection, hemostasis and protection against tissue injury with the suction tip inside the exposure because they are softer and thinner and have better absorbent and hemostatic qualities than the Codman patties.

10 Four-Pronged Hook (Sugita Hook) АNOTher

valuable instrument is a four-pronged hook or microrakе retractor. It is used for retraction of an acoustic neurinoma, meningioma, hard glioma and sometimes arteriovenous malformation. It is held by a self-retaining retractor fixed to the multipurpose head frame, as an assistant cannot always hold it steady. Retraction of a tumor with the hook gives an excellent space between the tumor and brain tissue, and the surgeon can devote both his hands to operative procedures without being concerned about retraction. In my opinion operations for such lesions cannot be performed properly without this kind of hook (Fig. II-8 D, E).

12 Microscope Sterilization

An operating microscope covered with a drape is inconvenient to use and is sometimes dangerous as contamination may occur if the drape tears. We have developed an automatic formalin sterilizing system which sterilizes an operating microscope within 30 min. The microscope is covered with a vinyl bag which is connected to two tubes leading to a gas generator. First, 8 ml of formalin is vaporized and circulated through the bag for 15 min. The gas is then neutralized with ammonia gas for a few minutes. Finally, the microscope inside the bag is washed with warmed air which is inspired into the circuit through a millipore filter. Although we used formalin tablets inside a bag for more than 10 years until introducing this system, control of the formalin concentration in the tablets was difficult and powder stuck to the lens of the microscope. The new automatic system is much better than the previous method: the time required for the whole process is short, the formalin is neutralized, and there is no powder to stick to the lens (Fig. 1110).

Ill Aneurysm General Considerations in Surgery of Aneurysms

There are differences of opinion about the indications for a direct attack on an intracranial aneurysm with regard to the timing of surgery, the high risk patient, and the location of the lesion. Grade I and II patients are generally considered to be candidates for acute surgery. We operate in the acute stage also on patients in grade III, and sometimes even IV, who have a big intracerebral hematoma or who are under 50. It is impossible to specify a general age-limit for surgery; even with patients over 75, for example, we operate on those who are physically young in appearance with minimum respiratory and circulatory problems and have worked actively till the SAH. Unlike aneurysms in the anterior circle of Willis, a basi-lar artery aneurysm should be attacked in an acute stage only when the patient is in good condition because the approach to the basilar artery involves a greater invasion of the brain and major arteries. A neurosurgeon who first operates on an aneurysm by himself must have assisted more than 50 such operations performed by expert surgeons and have done over 50 microanastomoses of rat arteries. In his initial cases he should operate with an experienced surgeon as assistant. In the surgery of aneurysms there are many basic principles to be observed and some useful techniques to bear in mind, such as the following. 1. Good angiograms should be obtained in various projections so that the surgeon can understand in detail the anatomical relationships between the aneurysm and its parent arteries. The size and configuration of the neck and body must be checked, and signs of vasospasm and arteriosclerosis must also be looked for. 2. All important instruments, especially clips, must be checked before the operation. 3. Good cooperation with the anesthesiologist and scrub nurse is essential. 4. Special care should be taken when positioning the patient; in particular, the head should be elevated above the heart level. Rotation of the head is also important; about 30 degrees for an aneurysm in the anterior circulation and 45 degrees for an aneurysm located at or around the basilar bifurcation (Fig. III-l). 5. The brain should be made as slack as possible by means of osmotic diuretics, CSF drainage, or hyperventilation. 6. The lateral bone edge of the craniotomy should be removed as far as possible in all aneurysm operations via frontotemporal, subtemporal and lateral suboccipital approaches. 7. The retraction of the brain must be very gentle and as little as possible, especially in an acute case. 8. Never approach an aneurysm directly, especially the dome. Parent arteries adjacent to the aneurysm should first be dissected. We should not work only on one side of the aneurysm but all around it, so that a space for temporary clipping can be obtained. An appropriate clip and clip holder should be at hand at each stage of dissection in preparation for an accidental rupture of the aneurysm.

Fig. III-l. Rotation of the head. (A) About 30 degrees for an aneurysm in the anterior circle. (B) About 45 degrees for an aneurysm at or around the basilar bifurcation

9. Dissection around the neck is the most critical procedure, In most cases the" dissection should be carried out trom the parent artery to the neck, never from the body to the neck. When there is strong adhesion between the aneurysm and the parent artery,dissection should be done so as to peel off the adventitia of the artery, rather than just cutting in the suspected space between the two structures (Fig. III-2). In my experience, the safest dissector is a silver dissector. Dissection with bipolar forceps is sometimes dangerous be-

11

fig. III-2, When the aneurystn is strongly adherent to the parent artery. dissection is done so that the adventitial layer of the parent artery is peeled off rather than directly dissecting the connective

cause the forceps' own opening force may push one of the blades against the aneurysm wall (Fig. HI-3 A). A dissector with a small ball at its tip has also the same dangerous disadvantage as the forceps, and another disadvantage is that, when inserted in a small space, the ball may become hidden behind the aneurysm or parent artery and so be beyond the surgeon's control. possibly resulting in injury to a perforating artery or to the aneurysm wall itself (Fig. III-3B). We have experienced intraoperative aneurysm rupture in less than 3% of our cases; most of these were minor leakages and could be controlled by a small suction. 10. Suction work demands extreme care. Л suction held in the left hand may accidentally injure the body of the aneurysm. Dissection around the aneurysm should be done not with a suction in the left hand but with a dissector held in the right, when the surgeon is right handed. The suction to be used around the aneurysm should be the smallest available and a small piece of cotton should be used with it as much as possible. 11. Direct retraction of parent arteries and the aneurysm is often necessary. Such critical structures are retracted with one or two tapered brain retractors with a tip of 2 mm in width: they are held steady with a self-retaining retractor at-tached to the multipurpose head frame. In this way both hands can be safely used solely for dissection and suction. We have never encountered any trouble or injury with this kind of retraction. and I believe that it is much safer than unsteady jction with a dissector or suction held in the hand (see Cases 15 and 33). 12. Each surgeon has his own preferences when it comes to the selection of clips. We must however select a clip with the most suitable shape and size for the aneurysm neck. The surgeon must have in mind all the different shapes of aneurysm clip available. When dealing with an unusual aneurysm,

it is a good idea to bring a clip close to the aneurysm in the operating field to judge its suitability. 13. The multiple clipping method and shortening of the clip blade should be kept in mind. Application of two and occasionally three or more clips is an important tactic for obliterating large and unusual aneurysms. The actual indications are explained in later sections.

Fig. III-3. Silver dissector is better than forceps or balltip dissector

12

Aneurysm

13 Clip blades can be shortened intraoperatively when necessary in less than one minute. The tips of the blades are cut with an ordinary surgical wire-cutter and the cut ends are smoothed with a diamond drill under the operating micro-scope: the cutter and drill must of course be sterilized. Several actual instances are mentioned in the operative descriptions below (e.g., Case 32). 14. Temporary clipping of the parent artery is a useful lactic with some large or unusual aneurysms. Aneurysm tension decreases by about half when this is done. A clip with a weak pressure of less than 80 g must be used: an ordinary clip with a closing force of over 120 g may well injure the arterial wall. We use such temporary clipping for no more than 10 min at a time, releasing for 4 min to lessen the danger of ischemic complications. Even when temporary clipping needs to be maintained for longer than 10 min, due for instance to injury to the aneurysm or artery, the clip can usually be released for a few minutes while bleeding from a hole is controlled with a cotton patty. 15. Neck ligation is another helpful technique, for use in special cases. For example, when there are multiple aneurysms in the basilar and middle cerebral arteries, the more superficially located middle cerebral artery aneurysm had better be ligated because if it is clipped first, the clip may injure the artery or slip off during the approach to the basilar artery aneurysm. When the number of different kinds of clip at hand is limited, ligation may occasionally be the only way to deal with the aneurysm. 16. Wrapping is generally an uncertain treatment. To accomplish complete wrapping of an aneurysm, the whole of the aneurysm must be isolated. If, though, it can be completely isolated, clipping might well be possible. As far as aneurysms in the anterior circle of Willis are concerned, I have done what is considered to be true wrapping in less than 1% of cases. I have coated a red face of a neck and wrapped a small residual neck with a small piece of cotton or Bemsheets occasionally coated with Biobond (or, recently, fibrin glue) in less than 10%; bipolar coagulation was occasionally added. Our laboratory study shows fibrin glue and Bemsheets to be ihe best materials for wrapping or coating (Case 13). 17. Puncture of the body is often indispensable when the aneurysm pushes against cranial nerves, when a clip slips onto the parent artery, causing stenosis, or when the perforator and parent artery are hidden behind the body. 18. Transient hypotension is occasionally useful. We lower blood pressure to about 70 mm Hg systolic for about 10 min. This produces almost the same effect as temporary clipping of the parent artery in reducing intra-aneurysmal pressure, which facilitates safe clipping.

Fig. ЕП-1. Sugita clip

19. Exploration after clipping should not be neglected. It should be done with extreme care not to move the clip too much. Complete dissection or confirmation of the neck and parent artery is not always necessary if the prcopcrative angiogram is thoroughly analysed. In a very few unusual cases intraoperative angiogram is needed. 20. Clots in the subarachnoid space are removed after clipping in surgery in an acute stage. They are removed as much as possible by tearing the arachnoid in and around the operating field and especially the Liliequist membrane. Tearing the arachnoid facilitates drainage of the bloody CSF postoperatively through a cisternal canula. During removal of the clots we should avoid retracting the brain excessively and injuring fine perforators and veins that are embedded in heavy clots. 21. Postoperative care: The most serious problem we of-ten encounter after surgery of a ruptured aneurysm in an acute stage is vasospasm which occurs in the postoperative period from day 3 to 14. Although various treatments for dilatating the vasospastic vessels have recently been reported, none of these is generally accepted as a definitely effective therapy in clinical cases. There are two measures we can take at present: (1) Improving cerebral circulation in the territory supplied by affected vessels with anticoagulants such as Ticlo-pidine, normoor slight hypervolemia and moderate hyperten-sion. The latter two should not be such as to cause an increase in intracranial pressure; one should also be aware that hypo-volemia is likely to occur when diuretic drugs are used. (2) Decreasing the intracranial pressure not only with cisternal drainage, which is primarily effective for draining bloody CSF, but also with ventricular drainage. Besides usual diuretic drugs such as Mannitol and Glycerol, barbiturate therapy is sometimes very effective when the intracranial pressure is extremely high. We believe that the most important treatments during the period of vasospasm are reducing the intracranial pressure and improving microcirculation.

Aneurysm Clips

Since the introduction of the Schwartz clip 30 years ago many other kinds of clip have been developed. Among them, Scoville, Heifetz and Yasargil clips as well as the Sugita clip have been most commonly used. Each clip has advantages and disadvantages. Indispensable properties of an aneurysm clip are as follows: (1) It is easily handled. (2) The blade tips open wide. (3) It has slim blades. (4) It does not obstruct the surgeon's view. (5) It can be easily removed. (6) The closing force is great enough. (7) Various shapes are available (Fig. III-4). (8) The material has good tissue compatibility. It is a general mechanical property of spring clips that the bottom of the blade has a closing force much greater than the tip, so if an aneurysm has a hard wall or high tension it should be obliterated with the bottom portion of the clip, not with its tips. Frequent reclipping with the bottom portion of the blade should be avoided because of the danger of ather-oma coming off (Fig. III-5). Although the clips of my design are now in use in most countries, there are still many points

14

Aneurysm Fig. HI-5. Closing force at various distances from the bottom to top of clip blades. Curves A, B, C, D, E, and F are for clips of 5, 10, 18, 25, 30, and 40mm blade length respectively

for improvement. More shapes are needed, for example, even though more than 70 are now available. The spring portion too should be made smaller because it sometimes disturbs the surgeon's view.

Clip Applicator and Remover

The Sugita clip applier is available in three different head sizes for ordinary, mini and ultralarge clips, and three head angles (straight, 15 and 30 degrees) for clips of standard size,

and all types should be kept at hand. The spring at the bottom of a Sugita clip applier is deliberately made weak so that the surgeon can open the clip with gentle finger force in order to feel any fine resistance around the clip blade when he applies it. One problem that is encountered due to weakening of the spring is that sometimes the clip cannot be smoothly dislodged from the narrow opening of the head. To avoid such trouble, the spring portion should be gently pushed in the direction of the head prior to each application of a clip to reinforce the spring pressure (but the spring will snap if it is pushed strongly). The multijointed Sano applier is occasionally very useful. A problem with this instrument is that the surgeon cannot get a direct feel of the clip blades while inserting the clip around an aneurysm due to the heavier weight of the applier and its multiple joints. Another Sano applier with a pair of small rotatable parts for holding the clip at the tip of the applier seems to be useful, but as they cannot hold a clip tightly the clip often shifts to an undesirable position when loosened from the applier, and removal of the clip with the same applier is also difficult. Clip removers of straight and angled types have been introduced. Almost all neurosurgeons have experienced the difficulty of regripping a clip with an ordinary applier in a narrow operating field; the clip may even jump out if it is improperly gripped. The new removers are convenient in such a situation since the gripping portion has a wider groove than usual, and the spring portion of the clip can be easily grasped. They are not, however, suited for reapplying the clip (Fig. III-6).

Fig. III-6. Clip applier and remover. (A-C) straight, 15 and 30 degree curved head appliers. (D) Sano's multijoint applier. (E) applier with rotating holder by Sano. (F, G) straight and curved removers

1 Carotid Artery Aneurysm Case 1 Ophthalmic Artery Aneurysm: Optic Nerve Retraction (rt)

\ Residual neck

This 59-year-old woman had an SAH two months before the operation. Operation. The aneurysm could not be visualized at first because it was located behind the right optic nerve. After the dura over the optic canal had been opened a relatively large portion of the roof of the canal was removed with a diamond drill. The bone of the anterior clinoid process over the right carotid artery was not removed. The dura propria of the optic nerve in the canal was opened. Adhesion of the optic nerve to the still unexposed aneurysm was dissected carefully, while the nerve was retracted medially with a tapered brain retractor held with a self-retaining retractor. Retraction was done for no more than 10 min at a time. The ophthalmic artery was identified and the aneurysm was found ventrome-dially to it. A Sugita clip bent sideways, No 11, was applied so that the blade was as parallel to the carotid artery as possible. Although the postoperative course was uneventful, a small residual neck was found on the postoperative angiogram. The postoperative course was uneventful.

Comment. (1) An aneurysm located in the proximal side of the origin of the ophthalmic artery, in the С 2 portion, is one of the most difficult to clip even with wide unroofing of the optic canal. The exact difficulty depends on the location of the neck and the direction in which the aneurysm protrudes, medially (toward the optic nerve) or ventrally (toward the base of the skull). Complete obliteration of the neck with a clip is often impossible unless it is small, for two reasons. The first is that the aneurysm usually protrudes medially from the dorsomedially curved portion of the carotid artery, so a small portion of the neck of either the proximal or the distal side is likely to remain undipped in the case of a wide-necked aneurysm. The second is that the bony structure behind the aneurysm obstructs the insertion of the lower blade of the clip. In three out of eight cases of this kind, including the present one, a small residual neck ( \ ) remained. When the aneurysm is located in the distal portion of the carotid artery complete obstruction of the neck is easier if an angled ring clip is used, as the artery can be included in the ring since there is no bony structure behind the aneurysm here. (2) Removal of the anterior clinoid process over the carotid artery is not necessary in most cases because the main purpose is to mobilize the optic nerve for retraction and not to mobilize the carotid artery, to do which is often hazardous. (3) When intraoperative rupture of the aneurysm occurs in this location temporary proximal clipping is impossible. It is therefore advisable that the cervical carotid artery be preliminarily exposed, although we have never experienced such rupture in our cases. Finger compression of the unexposed cervical carotid artery combined with induced hypotension would also be useful as an emergency measure.

17

1 Dura propria

18

Carotid Artery Aneurysm

Case 2 Triple Aneurysm (rt)

This 63-year-old man had a severe SAH three weeks before the operation, but was neurologically normal at the time of surgery. Operation. A right frontotemporal approach was taken for this triple aneurysm, which consisted of a left carotid artery aneurysm of unusual location, a right proximal carotid artery aneurysm and a right middle cerebral artery aneurysm. The aneurysm in the left carotid artery was approached after that in the right middle cerebral artery had been isolated. Although I hesitated at first about which side of the left optic nerve, above or behind, to insert a clip from, and about the shape of the clip, the aneurysm was successfully obliterated with a bayonet clip, No. 3, by inserting it behind the optic nerve. The second aneurysm, in the right proximal carotid artery, was a technically difficult one. Its dome adhered to the tentorial edge and anterior clinoid process and hid the proximal side of the carotid artery, which was visualized by carefully pushing the medial wall of the aneurysm laterally.

The clipping was successful though the bony structure behind the aneurysm interfered with the insertion of the lower blad of the clip. The third aneurysm, in the middle cerebral artery was straightforward. The postoperative course was unevent ful. Comment. (1) The aneurysm in the left carotid artery was clipped in an approach from the contralateral side in this case because two more aneurysms were located in the righ hemisphere. However, the contralateral approach to an aneu rysm should be chosen only in an exceptional case becaus temporary trapping is impossible and a catastrophe may ensue if it ruptures. (2) We have operated on eight aneurysms pro truding from the dorsal side of the carotid artery such a in this case. We have encountered intraoperative rupture in three of them and tearing off of the body in one. The incidence of intraoperative bleeding and operative complications was thus very high (50%) in comparison with aneurysms in other locations in our series (3%).

18

Carotid Artery Aneurysm

Case 2 Triple Aneurysm (rt)

This 63-year-old man had a severe SAH three weeks before the operation, but was neurologically normal at the time of surgery. Operation. A right frontotemporal approach was taken for this triple aneurysm, which consisted of a left carotid artery aneurysm of unusual location, a right proximal carotid artery aneurysm and a right middle cerebral artery aneurysm. The aneurysm in the left carotid artery was approached after that in the right middle cerebral artery had been isolated. Although I hesitated at first about which side of the left optic nerve, above or behind, to insert a clip from, and about the shape of the clip, the aneurysm was successfully obliterated with a bayonet clip, No. 3, by inserting it behind the optic nerve. The second aneurysm, in the right proximal carotid artery, was a technically difficult one. Its dome adhered to the tentorial edge and anterior clinoid process and hid the proximal side of the carotid artery, which was visualized by carefully pushing the medial wall of the aneurysm laterally.

The clipping was successful though the bony structure behind the aneurysm interfered with the insertion of the lower blade of the clip. The third aneurysm, in the middle cerebral artery, was straightforward. The postoperative course was uneventful. Comment. (1) The aneurysm in the left carotid artery was clipped in an approach from the contralateral side in this case because two more aneurysms were located in the right hemisphere. However, the contralateral approach to an aneurysm should be chosen only in an exceptional case because temporary trapping is impossible and a catastrophe may ensue if it ruptures. (2) We have operated on eight aneurysms protruding from the dorsal side of the carotid artery such as in this case. We have encountered intraoperative rupture in three of them and tearing off of the body in one. The incidence of intraoperative bleeding and operative complications was thus very high (50%) in comparison with aneurysms in other locations in our series (3%).

19

20

Carotid Artery Aneurysm

Case 3 Carotid Bifurcation Aneurysm (rt)

This 53-year-old man had a mild SAH the day before the operation. Operation. The Sylvian fissure was opened widely. The approach to the aneurysm was performed mainly retrogradely from the M1 portion of the middle cerebral artery rather than from the carotid artery. Perforating arteries were found on both sides of the aneurysm and were dissected from it. Clipping was easy. The postoperative course was uneventful.

Comment. When the intracranial portion of the carotid artery (Cl) is long, the approach to a carotid artery aneursym branching from the distal side of the bifurcation should be done retrogradely from the middle cerebral artery toward the bifurcation because less retraction of the frontal lobe is required. It is important to open the Sylvian fissure widely to facilitate this approach. Another important point is that there are generally more than two important perforators around the bifurcation which must be preserved. When the aneurysm is large we should check for accidental clipping of a perforator behind the aneurysm. продолжение

продол жение

21

22

Carotid Artery Aneurysm

Case 4 Medially Projecting Aneurysm: Clipping and Puncture (rt)

This 64-year-old woman had complained of visual disturbance for the preceding 6 months but experienced no SAH; vision in the right eye was 0.1 and in the left 1.0, and typical left homonymous hemianopia was found. Operation. The right carotid artery was curved laterally and the right optic nerve and right side of the chiasma were stretched dorsomedially. Curiously, the dome of the aneurysm was not located behind the optic nerve but was buried in it. As shown in the figure, two separate nerve structures were identified on both upper and lower sides of the aneurysm. First, a straight clip, 18 mm in length, was placed not close to the parent artery but 3 or 4 mm on the dome side because clipping close to the parent artery causes stenosis when the aneurysm has a wide neck. But the clipping was seen to be only partially successful, as the clip was pulsating. By means of a mirror inserted between the aneurysm and the A1 segment a residual neck was identified. Then a second clip of the same type was applied between the first clip and the carotid artery, upon which pulsation ceased; it was still far enough away from the parent artery for there to be no danger of stenosis. The first clip was then removed. The stretched optic

nerve became nicely slack following puncture of the body, though less than 0.5 ml of blood was extracted. Dissection around the slack aneurysm was abandoned because it seemed likely to injure the optic nerve. Postoperatively, the patient's visual acuity and visual field were fully restored. Comment. (1) It is very unusual that the aneurysm was located not behind the optic nerve but between the bundles of the nerve. After the clipped aneurysm was punctured, the anatomical relation between the two bundles and the aneurysm became clear. It is very rare for the crossed and uncrossed fibers of the optic nerve to be separated by the growth of an aneurysm. (2) Generally, puncture of the aneurysm is not essential even when it presses against cranial nerves, because the mass of the aneurysm will gradually decrease after clipping. However, puncture has the following advantages: it confirms complete clipping, makes it easy to check perforators behind the aneurysm, and facilitates quick recovery of whatever cranial nerve function has been impaired. Dissection around the aneurysm after clipping is unnecessary, and is indeed dangerous as it may injure important structures such as the perforator and nerve.

23

24

Carotid Artery Aneurysm

Case 5 Ventrally Protruding Aneurysm Obliterated with Ring Clip (It)

This 67-year-old woman had a mild SAH two days before the operation. Operation. A left frontotemporal approach was made. The aneurysm was found behind the left carotid artery, protruding ventromedially as shown in the preoperative angiogram. First, the posterior communicating and anterior choroidal arteries

were identified. While the left optic nerve was retracted medially a right-angled ring clip, No. 41, was inserted towards the distal end of the carotid artery and parallel to it. The utmost attention was paid to placing the bottom corner of the ring exactly at the border between the aneurysm and the posterior communicating artery. Time from dura to dura: 40 min. The postoperative course was uneventful (see Case 6).

25

26

Carotid Artery Aneurysm

Case 6 Aneurysm with Trigeminal Neuralgia (rt)

This 5 8-year-old woman had suffered from trigeminal neuralgia on the right side for the previous year without SAH. Operation. A right frontotemporal approach was taken. A large aneurysm was found behind the right carotid artery. Both the right posterior communicating and anterior choroi-dal arteries were found running over the body. Only a small portion of the aneurysm near the neck was visualized. The neck itself could be visualized only with the aid of a mirror because it was located just on the ventral side of the carotid artery. An oblique-angled ring clip, No. 35, was inserted from the carotid bifurcation side so as to place the blade tip behind the posterior communicating artery. The aneurysm was not punctured. Applying a ring clip greatly simplified the procedure, so that the main part of it required only ISmin.The postoperative course was uneventful. The trigeminal neuralgia disappeared about 3 months later.

Comment. (1) An aneurysm that protrudes behind the carotid artery is one of the best indications for a right- or oblique-angled ring clip. Obliteration with a ring clip is much easier than with other methods such as ligation or clipping with a conventional clip. To prevent accidental clipping of important perforators arising from the carotid artery, a clip with the most suitable blade length must be selected. Occasionally it is advisable to shorten the tip of the blade intraoperatively (see Case 32). (2) Special care should be taken to preserve the posterior communicating and anterior choroidal arteries and their branches: the position of the corner of the angled ring clip or the blade tip is the most important point in confirming preservation. When the posterior communicating artery arises from the body itself it can be reconstructed and a second ring clip used to obliterate the aneurysm as in the figure for Case 9. It must be stressed that the blades should be placed at some distance from the carotid artery in the case of a giant aneurysm.

27

1 Right posterior : Right A! : Right M

communicating artery

28

Carotid Artery Aneurysm

Case 7 Wide-Necked Aneurysm Obliterated with Two Ring Clips (It)

This 62-year-old woman had a severe SAH 3 weeks before the operation but her condition gradually improved. Operation. A left frontotemporal approach was made. A large aneurysm with a very broad neck was found protruding ventrolaterally. The oculomotor nerve was identified in the depths between the anterior tentorial edge and the proximal wall of the body. When the body was retracted posteriorly the posterior communicating artery was visualized branching from the proximal side of the base of the aneurysm. First, a long staight clip (18 mm blade, No. 18) was placed on the dome side of the neck as parallel to the carotid artery as possible. Although the posterior communicating artery was preserved, the blade tip obliterated the anterior choroidal artery and its perforator which arose from the ventral surface of the base and ran lateral to the carotid artery. On the second attempt to place the clip more to the dome side the blade slipped back to the same position as in the first trial (A). With the clip in this position an oblique-angled ring clip, No. 37, was placed on the dome side in such a way as to include the first clip in the ring (B). After confirming that the tip of the second clip had not shut off the anterior choroidal artery, the first clip was withdrawn through the ring of

the second. Clipping took 4 min in all. Removal of the first clip resulted in refilling of the dorsal residual portion of the base as the blade length of the second clip (10 mm) was shorter than the first (18 mm). Another clip of the same size as the second was then applied shallowly on the dome side of the neck (C). The anterior choroidal and posterior communicating arteries were preserved. Postoperative course: the patient awoke from anesthesia with right hemiparesis, which lasted for a few weeks. She later returned to full activity. Comment. (1) In this case the postoperative hemiparesis was suspected to be due to involvement of the anterior choroidal artery because the postoperative angiogram showed it to be about half the diameter of that seen preoperatively. Pressure by the blade of the clip was probably the cause, and the complication would have been avoided if the body had been punctured after clipping. (2) In carotid artery aneurysms with a wide neck there are always some difficulties as to how to preserve the posterior communicating and anterior choroidal arteries, how to prevent stenosis of the parent artery, and how to deal with a neck wider than the blade-length of a clip. I believe the best tactics for such problems to be the double clipping method as adopted in this case.

29

1 Left posterior communicating artery 1 L e

ft anterior choroidal artery

3 Left A t

4 Left M,

В

30

Carotid Artery Aneurysm

Case 8 Large Aneurysm Obliterated with Two Ring Clips (It)

This 72-year-old woman had a minor SAH 2 weeks before the operation. She had no neurological deficits, only a slight headache. Operation. A left frontotemporal approach was made. A large semifusiform aneurysm was found protruding mainly ventromedially from the carotid artery. Vasa vasorum, which usually suggest the site of the original parent artery, were seen on the dorsal surface of the aneurysm wall. First, the left optic canal was unroofed and the dura mater of the left optic nerve was cut to facilitate upward retraction of the nerve to expose the body. The medial portion of the aneurysm was clearly visualized by dorsomedial retraction of the nerve, but the retraction was not continued for more than 10 min at a time, following our "intermittent rule" explained in the general considerations. By pushing the side of the body medially, the posterior communicating artery was clearly identified as a degenerated fibrous string. It was of course judged to be unnecessary to preserve this artery, especially as it was not visible in the preoperative angiography. The proximal twothirds of the body was obliterated with an oblique-angled ring clip. No. 37. At the time of clipping transient hypotension of 75 mm Hg was induced for less than 10 min; it reduced the tension in the aneurysm by about a half. The optic nerve was retracted just enough to obtain a space to insert the clip. Then a second ring clip of the same shape with a shorter blade of 7.5 mm was placed on the distal residual body so

as to partially overlap the first clip in a counter direction. The newly constructed carotid artery seemed to have an ample diameter and the anterior choroidal and all perforating arteries around the aneurysm were preserved. The postoperative course was uneventful. Comments. (1) In this case preservation of the posterior communicating artery was unnecessary because it had not been functioning. When it is the main artery supplying the posterior cerebral artery it should be preserved in the way explained in the next case. Generally we must make the utmost effort to preserve the anterior choroidal artery. (2) An important point to remember when applying the angled ring clip to this kind of fusiform aneurysm is that the blade must be placed much farther on the dome side than one might consider necessary, so as to reconstruct the parent artery with a slightly larger outer diameter than that of the normal portion because such a large aneurysm usually has a very thick wall. Another important point is that an angled ring clip should not be replaced on the same wall more than three times in order to avoid the danger of intima or atheroma tearing off; the blade pressure of the ring clip is greater than that of an ordinary clip. (3) When two angled ring clips are necessary for complete obliteration of an aneurysm one of them should be oblique-angled so that the spring portion does not get in the way when applying the second.

31

Left anterior choroidal artery

Fibrous siring of left posterior communicating artery Left P:

32

Carotid Artery Aneurysm

Case 9 Large Aneurysm Obliterated with Three Clips (rt)

This aneurysm was found incidentally 6 months before the operation in a 74-year-old woman. At that time we did not envisage surgery because it was a non-ruptured aneurysm in an elderly patient. However, she had a mild SAH 20 h before the operation; her condition was Hunt and Kosnik Grade II. Operation. A relatively generous right frontotemporal craniotomy was made. A large aneurysm was encountered in the right carotid artery. The carotid wall had been stretched to become semifusiform; the main body of the aneurysm protruded ventrally. Vasa vasorum were seen on the dorsal side of the carotid artery. Without unroofing the optic canal, the posterior communicating artery was found when the right optic nerve was slightly retracted medially and the body was retracted posterolaterally. It appeared to originate not from the carotid artery but from the proximal side of the aneurysm body. It had to be preserved because the preoperative carotid and vertebral angiograms showed that the right posterior cerebral artery was fed by the right carotid artery. First, the proximal carotid artery was clipped with a temporary Sugita clip with a weak pressure of 70 g. A straight ring clip (No. 29, 6 mm blade and 5 mm ring) was then placed on the proximal side of the body perpendicular to the carotid artery which was included in the ring portion of the clip. The intention was to partially obliterate the proximal side of the body and construct there the wall of the posterior communicating artery. The temporary clip was removed in less than 1 min. It took me a while to select a ring clip with a blade length suitable to reach just from the first clip to the distal side of the carotid bifurcation. The No. 37 clip was the right one. This oblique-angled ring clip with a ring of 5 mm and blade of

Posterior communicating artery Anterior choroidal artery

10 mm was inserted from the distal side of the carotid bifurcation to the residual body parallel to the carotid artery so as to construct a new parent artery. The anterior choroidal artery originating from the distal side of the aneurysm body and three perforators from the carotid bifurcation were preserved through the ring. The newly constructed parent artery appeared to be of smaller diameter than normal because the second clip had been placed too shallowly, and it was therefore moved farther onto the body. Finally, a third clip, No. 8, curved and without a ring, was placed on the small residual portion from the distal side of the carotid bifurcation into the ring of the second clip, sparing the anterior choroidal and three perforating arteries. All procedures were completed without any bleeding or other trouble. Postoperative course: The patient regained consciousness fully. She developed hyd-rocephalus and experienced gastrointestinal trouble for a couple of weeks, but two months later she returned home able to walk. Comments. (1) In this case the newly constructed carotid artery was seen to have the same diameter as the normal proximal artery after all three clips had been placed. Although I wanted to move the blade of the second clip further onto the dome side I decided against it because the blade had pressed the neck for more than ten minutes after two replacements and tearing off of atheromas seemed likely. (2) We have experienced 5 other cases where important arteries origi-

1 Right posterior communicating artery

2 Right anterior choroidal artery

3 Right A1

4 Right M1

nated from the body. In all of them we were able to obliterate the body successfully with the multiple clipping method while sparing the arteries and perforators. In the case of aneurysms in the internal carotid and posterior communicating arteries, the posterior communicating artery was occasionally found branching not from the carotid artery but from the proximal side of the body. In such a case 1 recommend that a straight ring clip be placed on the proximal body perpendicularly to the carotid artery to construct (he origin of the posterior communicating artery with the blade and then an angled ring clip applied to the residual main neck with the blade parallel to the carotid artery. For preservation of an anterior choroidal artery in the same place much the same method can be used. (3) In this case, temporary clipping of the proximal carotid artery, not trapping, was done for 1 min. Temporary clipping should be applied as infrequently and for as short a time as possible. The main purpose of the temporary clipping is to decrease the aneurysm tension rather than to protect against massive bleeding from intraoperative rupture. For the latter purpose, temporary clipping may not be too late if applied even after bleeding has started.

2 Middle Cerebral Artery Aneurysm Case 10 Large Aneurysm Obliterated with Two Clips (rt)

Case 10A. This 44-year-old man had a severe SAH 15 days before the operation. CT scan revealed a large intracerebral hematoma in the right temporal lobe. For ^a couple с>£ days in the acute stage he was in Grade IV, but improved to Grade III in ten days. Operation. A right frontotemporal craniotomy was performed. The right Sylvian fissure was opened. A small portion of the aneurysm neck was seen and the proximal parent middle cerebral artery was identified. Without visualizing the right carotid artery, the arteries around the aneurysm and its neck and body were isolated. One of the M2 arteries was found behind the proximal side of the aneurysm when the latter was retracted. The usual contour of the trifurcation (actually bifurcation) of the middle cerebral artery was seen; the largest distal middle cerebral artery originated from the aneurysm. First, a temporary Sugita clip with a closing force of 70 g was applied to the right M1. Although the temporary clipping reduced the aneurysm tension by about 50%, a straight clip of 20 mm in length, No. 19 A, was placed on the body but slipped to the side of the trifurcation, narrowing the parent artery; its tip partially occluded the smaller artery branching from the proximal side. At this point the body was punctured without removing the clip, and it shrank (A). The clip was removed after a second clip of the same size had been applied

to the dome side not parallel but obliquely to the first clip; the temporary clip was also removed. Clipping took 8 min. The trifurcation was found to be sufficiently wide but a residual aneurysm remained between the clip and the distal bifurcation. An additional small clip of 5mm, No. 1, was placed on the residual portion (B). The hematoma in the right temporal lobe was evacuated and the wound closed. Postoperative course: The patient was discharged without any neurological deficits 2 weeks later. Comment. Within a period of 2 months we had the unusual experience of dealing with three middle cerebral artery aneurysms of similar size and location to this case (Case 10 В: lower X-ray pictures). All three were obliterated with the same method of double clipping, by which we were able to easily construct an ample trifurcation and to spare the parent arteries. In all three aneurysms a combination of a clip more than 18 mm long and a small clip was necessary. The clips were placed obliquely to each other. Although we may think of various methods for a large aneurysm outside the operating theater we are apt to forget them while actually dealing with it. For a large aneurysm we should be prepared to utilize multiple tactics in various combinations: transient hypotension, temporary clipping, puncture of the body, and multiple clipping.

1 Right Mj 2 Right M2

36

Middle Cerebral Artery Aneurysm

Case 11 Giant Aneurysm Obliterated with Two Long Clips (It)

This 54-year-old carpenter had an SAH 16 days before the operation. Operation. A left frontotemporal craniotomy was performed. A giant aneurysm was soon found on opening the Sylvian fissure. The left carotid artery and proximal side of the parent artery were isolated for possible temporary clipping. Both the walls of the trifurcation of the middle cerebral artery and the aneurysm neck were very hard with yellowish arteriosclerotic changes. An ultralong clip of 24 mm, No. 19C, was applied to the aneurysm body, about 5 or 6 mm distant from the bifurcation without hypotension or temporary clipping. The clip blades, however, were seen to open with pulsation. When a second clip of the same length was added parallel to and partially crossing the first clip to reinforce its pressure, the pulsation ceased. Only a very small amount of blood was obtained on puncturing the body. On the postoperative left carotid angiogram the aneurysm and the residual neck, which had purposely been left unincluded in the clip, had disappeared. Postoperatively, the patient developed slight aphasia, which gradually improved. Comment. A useful tactic for dealing with a giant aneurysm is, after temporary trapping of the parent arteries, to cut the body, evacuate the atheromas inside, and clip the neck.

This method is best if an ultralong clip is not available, though the period of temporary clipping should be as short as possible and deep-seated aneurysms are more difficult to handle than those in the middle cerebral artery. In contrast, application of an ultralong clip is very simple. When applying a long clip to a large aneurysm with a thick atheromatous wall, and . especially one in a very arteriosclerotic parent artery, the blade should be placed far from the neck; as a rule I place it at I a distance twice the diameter of the parent artery. The diameter of the reconstructed parent artery after clipping should be greater than that in its normal proximal portion; the actual size depends on the width of the neck and the hardness of its wall. If the blade is placed close to the parent artery as in an ordinary aneurysm, stenosis or obliteration of the parent artery are much more likely to occur because thick atheromas are usually present inside the wall of a giant aneurysm. Another useful technique with a large aneurysm is to reinforce the closing pressure of the first clip with an additional clip or one which we call ,a booster clip.; As the tension in the aneurysm increases with diameter, double application is absolutely necessary. The second clip can be placed either parallel to the first clip or overriding it; for the latter method, special booster clips of various forms have been designed.

38

Middle Cerebral Artery Aneurysm

Case 12 Large Aneurysm: Body Clipping (It)

This 57-year-old woman had a severe SAH 24 h before the operation. She was admitted to our affiliated hospital in Grade III 6 h after the SAH, and Barbiturate therapy was started. Operation. A relatively large left frontotemporal cranio-tomy was made because there was a hematoma in the left temporal lobe. An angry red brain was encountered. The bulging slackened following ventricular drainage. First, the left carotid and proximal middle cerebral arteries were approached and a space for temporary clipping was obtained with minimal brain retraction. A wide opening of the Sylvian fissure brought into view the medial portion of the aneurysm and all parent arteries of both proximal and distal sides, while preserving the big Sylivian vein. The giant aneurysm projected

pwpcwiiovuaity toward ttm surgeon, (in the. picture it has been

drawn for convenience as if it were projecting laterally). One distal middle cerebral artery arose from the medial portion of the aneurysm. The proximal and the other distal arteries were located on the ventromedial side of the aneurysm and their junctions were hidden by the aneurysm neck. With the aid of temporary clipping on the proximal artery a straight ultralong clip of 24 mm was placed almost at the middle of the body. The temporary clipping of the M1 lasted 2 min, and without this the main clipping would have been impossible because the aneurysm was much larger than the maximum opening of the blades and was very tightly expanded. A bayonet clip (not shown in the picture) was placed on the first clip to prevent slipping even though the first clip had not opened with arterial pulsation. A large residual portion of

the aneurysm remained around the origins of the three involved arteries; it was about twice the width of the parent artery. Because the wall of the residual portion was apparently quite thick and the point of rupture was ascertained to be on the lateral side of the obliterated body, it was wrapped with a piece of muscle, the edges of which were tightly closed with a clip. The clots around the aneurysm, located mainly along the lateral side of the body, were removed. Drains from the left lateral ventricle and the cistern were left in place. The main procedure from dural opening to dural closure took an hour and a half. Hardly any blood was lost. Postoperative course: The Barbiturate therapy was continued, and the EEG recorded with a Berg-Fourier analyser showed a normal pattern of therapy without asymmetry. From day 5 after the operation, however, renal dysfunction appeared and progressed rapidly. The patient died on day 10 due to uremia. Comment. (1) The position of the clip in this case was quite proper for the reasons described in the previous case. Though a small portion of the aneurysm remained at surgery, it disappeared on the postoperative angiogram. The patient was operated on within 24 h in Grade III. Although routine preoperative laboratory data showed no abnormality of kidney function, the Barbiturate therapy is suspected to have aggravated the potential renal dysfunction. (2) Important j points to remember when clipping a large or giant aneurysm: Case 12 cont'd on p. 40

1 LeftM,

продолжение

продол жение

1 LeftM1

41

42

Middle Cerebral Artery Aneurysm

Case 14 Giant Aneurysm: Clipping and Removal (rt)

X-Ray Picture. The CT scan showed a huge high-density mass of 5 x 5 x 6 cm in the right parietotemporal area. The density of the peripheral border changed on contrast enhancement. The right carotid angiogram demonstrated only a small aneurysm of 1 cm in diameter. Curiously, no distal parent artery of the aneurysm was revealed on the angiogram. This 14year-old boy had an episode of left hemiparesis one month before the operation, and this gradually improved. Operation. A generous right frontotemporal craniotomy was made. The sphenoidal and anterior temporal bone edges were rongeured off to the point where the aneurysm dome adhered. The chiasmal area was approached with retraction of the anterior frontal lobe, securing the carotid and the proximal middle cerebral arteries. In retrospect, so extensive an approach was unnecessary because the unruptured aneurysm bad a strong wall and the parent arteries were easily isolated. The Sylvian fissure could be widely opened from the distal direction toward the trifurcation by retraction of only the frontal lobe. The anteromedial portion of the aneurysm, the trifurcation and the temporopolar artery (early bifurcation) were easily dissected because there was no adhesion by the SAH. To ascertain the origin of the aneurysm, the ascending frontoparietal artery was traced distally from the trifurcation but could not be properly identified because the huge, hard aneurvsm overhung it. An ultralong clip of 4 cm was placed on the body but did not completely occlude it because the aneurysm was too hard. An incision was made in the distal body and the intracapsular organizing clots were removed to facilitate retraction of the proximal portion of the aneu-

rysm. Removal of these intracapsular clots enabled lateral mobilization of the aneurysm, and thus visualization of the proximal parent artery with the aid of a mirror. The distal parent artery could not be found during this dissection or\ with posterolateral retraction of the body. The proximal parent artery was obliterated with a temporary clip. The aneurysm body was opened wide and the clots inside further evacuated. A small amount of fresh blood was encountered around the small hole of the neck but there was no further flow. Checking the parent arteries around the neck was easy now because we could move the aneurysm wall; absence of the distal parent artery was confirmed. The proximal parent artery was coagulated and cut, and a small Week clip was left on the artery as a marker. The proximal portion of the body was resected, but total removal of the aneurysm was abandoned because of strong adhesion of the distal body to the normal brain. The postoperative course was uneventful and the patient recovered fully. Comment. This was an unusual aneurysm with no distal parent artery. Probably the distal artery had been embolized and had become organized. On the preoperative angiogram many fine collateral circulating arteries were found in the territory of the right anterior cerebral artery. Regarding the operative technique for such a huge aneurysm. the lateral bone edge should be removed as much as possible to gain an ample operative field: a more direct and somewhat rougher approach than usual may be allowed because the wall is far stronger than that of an ordinary aneurysm. Cutting the body to evacuate the contents after trapping the parent arteries facilitates subsequent procedures when an aneurysm is large.

43

1 Right M1 2

Right M2

3 Anterior Communicating Artery Aneurysm Case 15 Direct Retraction of Body (rt)

This 52-year-old woman suffered a mild SAH while hospitalized in our University Hospital for Cushing's disease, for which she had been receiving treatment for the previous 5 years. The operation was performed on the sixth day after the SAH. Operation. As usual, with the patient in the supine position and the head higher than the level of the heart, a right frontotemporal craniotomy was made. After as much as possible of the right sphenoidal ridge had been removed, the right Sylvian fissure was opened and the basal portion of the frontal lobe was retracted with a tapered spatula of a rather wide tip. Two or occasionally three tapered retractors with tips of 2 mm in width were applied around the aneurysm; they were moved every 10 min. The distal portions of the bilateral anterior cerebral arteries (Al) were easily seen. Two accessory anterior communicating arteries were found. A small portion of the right gyrus rectus was removed in order to identify the bilateral distal anterior cerebral arteries (A2). Although the right A 2 and the neck of the aneurysm were isolated, the left A2 was hidden by the body. Retraction of the left side of the aneurysm toward the right enabled the left A 2 to be seen; it adhered strongly to the aneurysm like the brim

of a hat. The body was retracted directly with a tapered brain retractor held by a self-retaining retractor attached to the multipurpose head frame, and with a clear view of and around the left A2 thus obtained the artery was successfully dissected. I used both my hands, the right for dissecting and the left for suction. Dissection was very difficult because the adhesion was tight as if the artery and aneurysm were one body. Clipping was successful on the third attempt. The first time, the clip was placed too close to the anterior communicating artery and the second time it went too far onto the body due to the broad neck. No perforating artery was seen behind the clipped neck. The postoperative course was uneventful. Comment. (1) A recommendable technique, and one that is routine with us, is to use a number of tapered spatulas with a tip of 2 mm in width around an aneurysm. The use of tapered spatulas enables the surgeon to obtain a better space by retracting the cortex less than with a conventional \ untapered spatula. (2) We^ always adhere to the principle of | intermittent retraction of brain_ andj/essels, retracting for 10 min at most and then releasing for 5 while the spatula is moved to another area. (3) One of the difficulties in the pterional approach to an anterior communicating artery aneurysm

45

1 Left A: 2 Right A, 3 Right A4 Left A2"

is that the parent arteries of the side contralateral to the approach are often completely hidden by the ancurysm and adherc strongly to it as in the present case. Ordinarily, one dissects the adhesion with a dissector in the dominant hand and retracts the body with a suction held in the other, but it is sometimes dangerous to retract a ihin-wallcd aneurysm with the suction. I recommend direct retraction of the body with a tapered retractor of 2 mm. This should never be held by an assistant surgeon but by a light-weight self-retaining retractor, in order to secure steady and delicate retraction. When a conventional, heavier self-retaining retractor is used its tip >inks slowly under its own weight, resulting in injury to the aneurysm wall. It is possible only with a light-weight selfretaining retractor to feel the pressure being used for retraction. Experience is necessary before one can tell the safety limit for the retracting force. Generally, of course, the retractor is placed on the whitish portion of the body with thicker wall; a portion with a thin red wall must not be retracted. Another rule of thumb is that as the size of an aneurysm increases, the body will tolerate stronger retraction.

46

Anterior Communicating Artery Aneurysm

Case 16 Temporary Clipping (rt)

This 58-year-old man suffered an SAH 2 days before the operation. Operation. As usual a right frontotemporal craniotomy was made and an aneurysm was soon found. The ventral side of the body adhered widely to the chiasma and other structures of the base of the skull. Its upper portion impinged on the left frontal lobe and the wall here was reddish and so thin that the swirling stream of blood could be seen through the membrane. Except for this part dissection around the neck was not difficult and a space was made behind it. The right Al and A 2 were isolated but the left Al and A 2 could not be seen as they were situated behind the aneurysm which adhered tightly to the left frontal lobe. We chose preliminary clipping of the aneurysm rather than dissection around the body to identify the left arteries. It was temporarily closed with a bayonet clip 12 mm long, No. 14, which was intentionally inserted past the end of the neck. The body was punctured after the wall had been thickened by bipolar coagulation, and the whole of it was dissected from the surrounding tissues. A hole was made in the portion that had compressed the frontal lobe. As the isolated body still disturbed the operative

view it was partially cut with scissors, and all the structures behind it became visible. The left A2 and one perforator were identified; they had been included in the temporary clip. A small bayonet clip, No. 3, was applied above the first clip in order to remove the latter. Then another No. 3 clip was placed snugly on the neck sparing the left A 2 and the perforator. Finally, the left Al was identified behind the anterior communicating artery. The postoperative course was uneventful. Comment. When a dome with a thin wall adheres strongly to a surrounding structure and not all the parent arteries can be identified, a recommendable procedure is to isolate the dome after the body of the aneurysm has been preliminarily clipped. This is much safer than directly dissecting the dome from surrounding structures, which involves the risk of rupture. A bayonet-shaped clip is useful for such preliminary clipping as it makes it easier to apply a second clip parallel to the first; an ample gap can be obtained between the spring portions of the first clip and the second and this gap also facilitates insertion of the clip applier. The second clip may be of bayonet shape instead of the first.

1 Right A! 2 Right A2 3 Left A,

48

Anterior Communicating Artery Aneurysm

Case 17 Double Clipping: Clip Blade Covered with Silastic Tube (rt)

This 55-year-old man had undergone a successful operation for an aneurysm of the posterior inferior cerebellar artery three years earlier. At that time the anterior communicating artery was normal. He complained of headache three weeks before the operation. Operation. A right frontotemporal craniotomy was made as usual. The approach to the aneurysm was not started anteriorly to the aneurysm but posteriorly to the anterior communicating artery, so as to identify the parent arteries first. All four parent arteries and perforators were isolated. The main body was found projecting into the prechiasmatic cistern and it was tightly adherent to the surrounding tissues. A daughter dome was located over the anterior communicating artery pro-

jecting toward the surgeon. The aneurysm originated not from one side but from two thirds of the circumference of the anterior communicating artery. The two domes belonged to one body. If only one clip were to be used a large residual neck would remain. Therefore a first straight clip, No. 2, was applied to the main aneurysm body and a second L-shaped clip of 5 mm blade length, No. 5, was placed on the residual portion, so as to cross the blades of the first clip at a right angle. Before the second clip was applied its blades were covered with silastic tube (made from shunt tube), in order to fill up the gap under the blades caused by the tips of the clip over-riding the blades of the first clip. The lower blade of the second clip was positioned blindly, but by moving the clipped body we were able to confirm that the two clips were snugly positioned. Finally, two pieces of muscle were placed between the right optic nerve and the spring portions of the two clips to prevent injury to the nerve. Comment. Double clipping is often a useful technique for an aneurysm of unusual shape, such as one without a small or simple neck. A combination of two clips makes possible a great variety of overall blade shapes (see Case 8). In this case silastic tube was used to fill the gap made by crossing two clips. Recently, instead of using such tubing, we often shorten the blade intraoperatively to the desired length by cutting the tips with a sterilized wire-cutter and filing the cut end with a diamond drill. The necessary instruments are available in any operating theater, and the procedure takes only about a minute (see Case 32).

49

1 Right A 1 2 Left A2 3 Right A2 4 Left A2

50

Anterior Communicating Artery Aneurysm

Case 18 Double Clipping (rt)

postbp.

This 58-year-old man suffered a severe SAH two weeks before the operation. Operation. An approach to the anterior communicating artery was made through a right frontotemporal craniotomy in the usual manner. The region around the aneurysm was clearly seen after dissection of the interhemispheric fissure and retraction of the right and left frontal lobes with three tapered retractors without removing the gyrus rectus. The four parent arteries were found behind the aneurysm. The shape of the aneurysm was unusual, and it was larger than suspected from the preoperative angiogram. It had bulged directly from the anterior communicating artery without a neck. First, complete clipping of the whole base of the aneurysm was attempted with a bayonet clip, No. 13, but this caused stenosis of the

junction of the left Al and A2, so the same clip was reapplied obliquely to the base, leaving a small portion of the dome undipped. A curved clip, No. 8, was used to occlude the residual portion. Finally the body was punctured, but did not slacken very much apparently because the major portion of it contained organizing clots. The postoperative course was uneventful. Comment. Although double clipping was certainly indicated for this aneurysm, the blades of both clips were unnecessarily long, especially those of the second clip. Recently we use miniclips, Nos. 81-88, in cases like the present one. If such miniclips are not available it is recommended that the blades of an ordinary clip be shortened intraoperatively with a wire-cutter and diamond drill.

52

Anterior Communicating Artery Aneurysm

Case 19 Two Cases with Ring Clip (It)

Case 19-1. This 58-year-old man had a severe SAH 2 days before the surgery. His condition was Grade II at the time of the operation. Operation. The patient was operated on in a supine position as usual; a ventricular drain was inserted into the right ventricle. A left frontotemporal craniotomy was made because the right proximal anterior cerebral artery (Al) was not seen on the preoperative angiogram. After the Sylvian fissure was opened widely the left frontal lobe was retracted. The Al segments of both sides were easily identified but the aneurysm was located in such a high position that the left gyrus rectus had to be partially removed. The aneurysm projected posteriorly and both A2s were over-riding the body. The right A2 was easily dissected from it but the left one adhered tightly, and as the body was beneath the artery the dissecting procedure would have had to be performed blind; we therefore decided against dissection. After confirming that there were no perforators behind the neck, an oblique angled ring clip, No. 32 (5 mm blade, 3.5 mm ring), was applied so as to include the left A 2 in the ring. Finally as many as possible of the clots in the interhemispheric fissure were removed, as were those in the prepontine cistern. The ventricular drain was connected to the external drainage system. The postoperative course was uneventful.

Case 19-2. This 66-year-old woman suffered a severe SAH three weeks before the operation. Operation. The aneurysm was found to arise from the whole anterior communicating artery with a wide neck that included the junctions of both A2s. The right proximal A2 could be dissected from the aneurysm but dissection of the left one was far more difficult because of tight adhesion. An oblique-angled ring clip, No. 36 (7.5 mm blade, 5 mm ring), was applied to the neck so as to place the blade tip behind the right proximal A 2 and the curved corner of the blade at the proximal origin of the left A2. Although a small perforator was found branching from the ventral surface of the junction of the right Al and A2 before clipping, we were able to preserve it by taking care with the direction of insertion of the lower blade. The postoperative course was uneventful. Comment. A useful application of the angled ring clip is for an anterior communicating artery aneurysm. An aneurysm here often has a broad neck and sometimes the adhesion between the parent artery and the aneurysm is too tight to isolate the artery without causing rupture. In such an instance application of an angled ring clip greatly simplifies the procedure. When the neck originating from the anterior communicating artery is wide, the blade of the angled clip can be placed parallel to the parent artery without causing kinking. Another important point is preservation of perforators originating from the back wall of the anterior communicating artery.

53

54

Anterior Communicating Artery Aneurysm

Case 20 Giant Aneurysm (It)

The 67-year-old woman had had an SAH 10 years earlier. Recently she had developed memory disturbance and mild urinary incontinence due to obliteration of the foramen of Monro caused by a giant aneurysm. Operation. A frontotemporal craniotomy was made on the left side because the giant aneurysm was seen to project mainly into the right hemisphere from the anterior communicating artery' on the anteroposterior view in the preoperative angiogram. Ventricular drainage was instituted in the right anterior horn, and this markedly slackened the brain. The vascular complex of the anterior communicating artery was easily identified. As the aneurysm was so big, more of the left rectal gyms was removed than in an ordinary aneurysm operation in this location. The neck was located at the right side of the origin of the right A2, overlying the aneurysm dome. Both Al s and the left A 2 were also overlying the dome but they were easily isolated. Dissection of the right A 2 was, however, very difficult due to its tight adhesion to the dome. About 80% of the operating time was spent on isolating this artery. At first, clipping was attempted with a right-angled ring clip. No. 41 (5 mm blade. 5 mm ring), including the right distal A 2 in the ring. However, it produced a marked stenosis at the origin of the right A 2. Next a curved clip, No. 8, was inserted from the distal side of the neck to position the blade as far from the parent artery as possible. Nevertheless the portion of the right A2 over the aneurysm neck was slightly narrowed, but not enough to cause any ischemic complication.

Other parent arteries were well preserved. The dome was neither punctured nor dissected. From dura to dura: 2 h. Almost no blood-loss. Two days after the operation a ventriculoperitoneal shunt was done. Postoperatively the mental disturbance and urinary incontinence gradually improved, and disappeared in about 6 months. Comment. In the territory of the anterior cerebral artery as well as of the middle cerebral we have frequently found a giant aneurysm with a big organized dome; it is usually large on the CT scan but small on the angiogram. The present case is one of 6 in our series. For such aneurysms we should select an approach to the neck not over the dome but from where the neck can be seen without retracting the dome; the principle is basically the same as that for an ordinary aneurysm. More retraction of the brain would have been necessary for the approach, and clipping would have been more difficult, if an interhemispheric or a right subfrontal approach had been chosen because the immobile hard dome would have hidden the neck. Puncture of the aneurysm would help to position the blade better on the dome by reducing intraluminal tension but it does not usually decrease the aneurysm volume because the major portion of the aneurysm is organized. In the present case total resection of the aneurysm was decided against because the mass of a completely clipped aneurysm usually decreases in the course of time, and removal would have injured perforators of the parent arteries and important surrounding tissues.

1 Right A!

2 Left Аг 3 Left A2

4 Right A3

4 Distal Anterior Cerebral Artery Aneurysm

General Considerations

In the routine approach to a distal anterior cerebral artery aneurysm the patient is placed in the supine position, with the head elevated above the heart level. The head is placed straight at the beginning of the operation and is rotated as needed during the operation. The chin is up, but slightly less so than in the usual subfrontal approach by a frontotemporal craniotomy; the craniotomy should be extended anteriorly to just above the orbital ridge. A unilateral right frontal mid-line craniotomy is made with a semicoronal scalp incision. The approach is usually made from the right side for both right and left anterior cerebral artery aneurysms, although some unusual giant aneurysms may have to be approached bilaterally. The bone flap is turned as close to the sagittal sinus as possible and the midline bone edge is rongeured obliquely until the sagittal sinus is partly seen. Cortical bridging veins larger than medium size are best preserved by taking an approach between the veins which are isolated from the cortex by cutting the arachnoid around them (Fig. 1-3, p. 2, preservation of bridging vein). The medial surface of the frontal lobe can easily be retracted until the edge of the falx is

seen. It should be kept in mind that the deeper frontal surfaces of both sides in the interhemispheric fissure apparently have only one thin arachnoid layer. Thus the deeper surface of the medial frontal lobe cannot be retracted without various degrees of damage. We use more than two tapered brain retractors; retraction of the contralateral left cortex is often helpful. It is occasionally difficult to find the aneurysm, which is usually located at the junction of the A2 and A3. It should be remembered that the right artery is sometimes located in the left side of the operating field and is embedded in the contralateral frontal lobe. When a small portion of the proximal parent artery is found, further proximal dissection of the parent artery is unnecessary. There is less danger here of intra-operative rupture of the aneurysm than in other locations because blood pressure is lower and temporary trapping of the parent artery is easier. The distal anterior cerebral artery aneurysm projects toward the approach and its neck is located behind the dome at the bifurcation, trifurcation or occasionally quadrifurcation of the parent artery. Postoperative pooling of blood in the interhemispheric space should be avoided because CSF circulation here is poorer than in other areas, and postoperative neurological deficits such as disorientation and incontinence due to vasospasm may result.

Case 21 Prevention of Narrowing of the Parent Artery (Two Clips) (rt)

This 52-year-old man had a severe headache, probably the first SAH, 2 years earlier. The second attack with headache, vomiting and dizziness appeared three weeks before the operation. Operation. As described in the basic principles, a unilateral right midline frontal craniotomy was made. An aneurysm was found embedded in the medial cortex of the right frontal lobe, its base hidden by the expanded dome. Pushing the dome to the right with a tapered retractor made it possible to see

the base of the aneurysm which had arisen from the trifurcation without forming a neck. Obliteration of the aneurysm with a single clip seemed likely to cause stenosis of the trifurcation because the proximal and distal parent arteries formed a sharp angle. Therefore, with the intention of reconstructing the parent artery here using two clips, a first straight clip, No. 15, was applied obliquely to the body instead of directly on the neck. Then a right-angled ring clip. No. 41 (5 mm blade, 5 mm ring), the proximal blades of which were covered

57

] Right A2 Left A3 5 Right A3 4 Falx

with silastic tube, was applied lo the residual neck so as to cross the first clip almost at a right angle. The postoperative angiogram showed the parent artery patent without stenosis. Comment. For unusual or giant ancurysms, a good technique is to trap the parent artery, puncture the dome to col-lapse it, and then clip the aneurysm using two clips. This is another good way to preserve the parent artery without producing stenosis or a residual neck. An angled ring clip was selected in this case because a branching artery located dose to the residual portion of the aneurysm limited the direction from which a clip could be applied; the ring itself was unnecessary but the distance from the angled comer to the spring portion made it easier to place the clip properly. An Lshaped dip can also be used.

58

Distal Anterior Cerebral Artery Aneurysm

Case 22 Prevention of Narrowing of the Parent Artery (Three Clips) (rt)

This 63-year-old woman had an SAH 2 days before the operation. No high-density area was found on the CT scan and there were no deficits on neurological examination. Operation. The approach was the same as in the previous case. The prechiasmatic cistern was opened and the CSF suctioned, which made the brain slack. The approach to the aneurysm was planned according to the angiographic findings; dissection was not made from the anterior side of the aneurysm (through the frontal tip), but posteriorly, where the proximal parent artery was easily identified. The aneurysm was located on the top of the azygos anterior cerebral artery. The bilateral distal anterior cerebral arteries (A 3) and a right fron-topolar artery were found branching from the trifurcation of the azygos artery at a right angle. The dome projected toward the approach. The proximal parent artery and the aneurysm together formed the shape of a mushroom. The body was hard and far larger than suspected from the preoper-ative angiogram. As I thought that a simple clipping would cause stenosis of the trifurcation I decided to use two clips. First an oblique-angled ring clip, No. 37 (10 mm blade, 5 mm ring), was placed on the aneurysm base slightly on the dome side. Total obliteration of the body was not achieved even with a 10 mm blade: a residual portion 2 or 3 mm wide was

found beyond the tip. Next a straight clip, No. 1, the tips of which were coiled with surgical thread, was placed over the first clip at a right angle. The purpose of the coiled thread was to decrease the gap created by crossing the two clips. After the dome had been totally isolated by clipping, a slight oozing occurred from it. A third clip, another No. 1, was therefore placed on the first to reinforce its pressure, and this stopped the oozing. Finally, some muscle was wrapped around the aneurysm. The postoperative course was uneventful, though the angiogram showed what appeared to be a small residual neck. Comment (1) The reason for the oozing after two clips were applied is probably that the first clip had not completely closed the aneurysm because of the hard irregular wall. Another reason may be that the second clip had not completely obliterated the residual portion of the neck because there was still some gap between the blades of the first due to the thick wall; the third clip completely closed the first, which in turn resulted in the closure of the second. I think the latter explanation is the more likely. This triple clipping was in fact unnecessarily clumsy. We should have first applied a straight clip where we put the second and then an angled clip where we placed the first, without crossing the previous clip. (2) All the cases presented here were clipped with angled L-shaped clips with or without a ring. In our 23 cases of distal anterior cerebral artery aneurysm such L-shaped clips were used in 12 cases (see Case 22-2). The other aneurysms were simply clipped with a straight or curved clip. Many of the aneurysms in this territory project toward the approach and the neck is behind the dome. In such an instance the blade of the clip must be positioned at a right angle to the approach, and this is the reason for the frequent use

of an L-shaped clip. The reason for selecting an angled ring clip is that clipping is possible without inserting the clip-applier deep into the narrow operating field thanks to the added length proved by the ring.

59

60

Distal Anterior Cerebral Artery Aneurysm

Case 23 Large Aneurysm (Two Clips) (rt)

This 56-year-old policeman had had an SAH 10 years earlier. The second attack was 6 weeks before the operation. At the time of surgery no neurological deficits were observed even though there was slight hydrocephalus. Operation. Following institution of lumber drainage, a right unilateral anteromedial frontal craniotomy was performed. In retrospect, the frontomedial corner of the craniotomy should have been made larger because the small remaining distance of 8 mm from the bone edge to the frontal base disturbed the surgeon's view. Only one small cortical vein was sacrificed but dissection of the interhemispheric surface was not easy because of unusually strong adhesion after the two episodes of SAH. Many small veins on the cortical surface had to be coagulated and cut. After cutting the genu of the corpus callosum, the distal side of the azygos A 2, the bilateral A3s and the aneurysm were all visible. As the preoperative angiogram had shown, the aneurysm was located much deeper than the usual aneurysm in this region and it was very large. Many small arteries branched around the trifurcation; they were all preserved except for a small one. All the parent arteries were isolated from the aneurysm. It was a very difficult one to clip as it was based on the posterior side of the trifurcation which had widened and formed a part of the neckless aneurysm. Stenosis of the trifurcation or a large residual portion of aneurysm would have resulted if a single clip had been used to obliterate it. So, first, a temporary clip was applied to the azygos A2. This resulted in a decrease in the tension of the aneurysm by about half. The temporary clipping was continued for 10 min at a time and normal circulation was restored intermittently by loosening the clip for 4 or 5 min. A long straight clip of 21 mm was placed on the distal half of the dome posterior to the trifurcation. Then an oblique angled ring clip, No. 36 (7.5 mm blade, 5 mm ring), was in-

serted from the proximal side to form a right angle to the first clip and positioned on the residual aneurysm on the proximal side, thereby preserving the azygos A 2 with the ring. As a gap between the tip of the second clip and the blade of the first was found, the second clip was exchanged for one a little longer of the same shape (10 mm blade). Total obliteration of the dome was successful although a small residual portion around the trifurcation remained. The postoperative angiogram showed obliteration of the aneurysm but also what might have been a residual dilatation. The postoperative course was a little troublesome. The CT scan showed a low density in the right frontal lobe and the patient developed urinary incontinence and disorientation for three weeks, after which the neurological deficits began to improve. Three months later slight disorientation remained. Comments. (1) The low density in the right frontal lobe could be the result of either brain retraction or temporary clipping. I wonder whether we should have made a bilateral frontal craniotomy and retracted the bilateral frontal lobes to deal with such an unusual aneurysm. Would the damage to the frontal lobe have been less this way? Generally speaking the operating field obtained with a bilateral craniotomy is wider than with a unilateral one, necessitating less retraction of the brain, although the operative invasion is bilateral. (2) A straight clip has the advantage of reducing the size of a large aneurysm to facilitate the placing of an angled ring clip, which does not open as wide as a straight clip. The question as to which direction a ring clip should be inserted from depends on the anatomical relationships among the aneurysm, the parent arteries, and surrounding structures. It is most important not to leave a gap between the blades of two clips when double or triple clipping is done.

61

продолжение

продол жение

В Aneurysms of the Posterior Circle of Willis General Considerations for Basilar Artery Aneurysms Approach Routes. Two main approaches are in use today; the frontotemporal and the sub temporal. We select between these according to the location of the aneurysm in the basilar artery or to other considerations such as the presence of more than one aneurysm. The fronlolcmporal approach is used for the majority of aneurysms in the upper portion of Lhc basilar artery, while the sublemporal is limited to basilar trunk aneurysms and to ihosc basilar artery ancurysms in an acute stage, or with the dome pointing posteriorly, or accompanied by circulation deficits or a previously clipped aneurysm in the carotid artery. The advantages of the frontotemporal approach are that less brain retraction is required than in the subtemporal approach, the anatomical orientation of the vessels in_and around the basilar bifurcation can be discerned more easily because the approach is relatively from the front, and the structures of the contralateral side can be better seen. The disadvantages of this approach are that the major arteries such as the carotid and middle cerebral must often be retracted and the operating field is narrower in lateral width and deeper than in the subtemporal approach. The subtemporal approach has the following disadvantages: Retraction of the temporal lobe causes postoperative complications more frequently than the frontotemporal approach, especially when an aneurysm of the basilar bifurcation is located high. The oculomotor nerve jnter feres with surgical maneuvers, and postoperative palsy may occur. The isolation of contralateral structures is often difficult. The advantages of the approach are that the operating field is wide in the frontooccipital direction and there is no need to retract the major arteries. The subtemporal approch is best for aneurysms protruding posteriorly from the basilar artery and for basilar trunk aneurysms.

Fig. III-7. Patient position

Fig. HI-8. Various routes to the basilar artery aneurysm: (7) from laterally to the posterior communicating artery; (2) between perforators of the posterior communicating artery; (3) through the optico-carotid space; (4) above the carotid bifurcation

1. Frontotemporal Approach (Pterional and Transsyl-vian). In the supine position the patient's head is elevated above the level of the heart, rotated to the side opposite to the approach, and fixed in the Sugita skull fixation frame to which a multipurpose head frame is attached (Fig. JTT-7). The side of the craniotomy is decided by the location of the aneurysm in relation to the parent artery. Cerebral dominancy is not the primary concern but easiness of approach to the neck. For example, the majority of basilar bifurcation aneurysms and aneurysms originating from the right basilar-superi-or cerebral artery are approached from the right, while a left-sided craniotomy is used for aneurysms located left of the midline. The operative procedure becomes much more difficult when an aneurysm is located in the side contralateral to the craniotomy even by such a short distance as 2 or 3 mm. The skin incision and the bone flap are the same as those for ordinary aneurysms in the anterior circle of Willis. However, the sphenoidal ridge must be removed far more extensively than is necessary for aneurysms of the anterior circle. Great attention must be paid to the retraction of both skin Пар and muscle layer because they disturb the surgeon's view in the same way as the sphenoidal ridge. Sacrifice of the bridging veins of the temporal tip is unnecessary except in some

63

unusual cases such as a huge aneurysm where the tip must be retracted posteriorly. The Sylvian fissure must be opened s wide as possible, especially in the case of a high-positioned ifurcalion aneurysm. All high-positioned aneurysms can be •rtially visualized by retracting the ventroposterior portion f the frontal lobe, namely the medial bide of the Sylvian ssure. From here there are three routes to the aneurysm self: ( 1 ) through the lateral side of the carotid artery, (2) etween the carotid artery and the optic nerve, and (3) above he carotid bifurcation (Fig. 111-8). I) Route through the lateral side of the carotid artery: This jute is used in ihc majority of cases, over three quarters f our series. After dissection of the arachnoid around the irolid artery and optic nerve, the oculomotor nerve is care-jHy dissected from the temporal tip. When the temporal lobe feeres strongly to the oculomotor nerve the adherent arachnid is not dissected from the nerve but from the temporal ibe in order (o preserve nerve function. The temporal lobe .retracted laterally with a tapered retractor. Liliequist's mcm-raue is opened wide. When the membrane is hard due to, rvere SAH. sectioning should be started from its anterior! onion because there is a large space behind the membrane' не without any important structures. The approach should Г course be made without medial retraction of the carotid г middle cerebral arteries until it is impeded by the narrow-ess of ihe operating field. When these vessels arc retracted boost all aneurysms of the basilar bifurcation come into jght. The С1 or M1 portion is gently retracted medially with •nimal force and for the shortest possible time. We keep > our principle of intermillcnt retraction {retraction for D mm and release for 4 min) and try not to retract so strongly I to compromise the blood circulation. When the С1 or M1 iretracted medially, the first branch from the M l , the tempo•I polar artery, often hinders the retraction. When this hapot> the temporal polar artery is isolated distally from the nponU arachnoid to permit further retraction, or is sacriiood when it is small. In the operating field below the level f the carotid artery, the posterior communicating and its nadung arteries are located over the aneurysm and its par-tf arteries. Although the posterior communicating artery and ft perforators completely cover the aneurysm in the begin-*_ Meticulous dissection of the perforators creates enough

Fig. IH-9. Selection of a route in relation to the position of the basilar bifurcation: (/) When the bifurcation is low, approach is made from the lateral side of the posterior communicating artery. (2) When the bifurcation is high, approach is attempted between perforators of the posterior cornmunicating artery

space to visualize it. In a quarter of our scries the approach to the aneurysm was performed in the medmf side of the posterior communicating artery through these perforators (Fig. III-9 — 10). Even if an approach can be made in the lateral side of the posterior communicating artery, the tapered brain retractor, which retracts the Cl or M1 medially, is often moved down to include the posterior communicating artery. In some cases it is inserted as deep as the mammillary body over the optic tract. When a basilar bifurcation aneurysm is unusually large or located in a high position it is recommended that the temporal lobe be retracted posteriorly and a space obtained there. One indispensable procedure is the isolation and preservation of the perforators around the aneurysm. which are described in a later section. (2) The route between the carotid artery and optic nerve: We call this space the ^opticocarotid space'". This route should be taken when the carotid artery cannot be retracted medially because of marked lateral protrusion or a hard arter-iosclcrotic arterial wall. We have used the route in about 15% of cases. The optic nerve is retracted medially with a tapered retractor after the dura of the posterior edge of the optic canal has been cut and, occasionally, the optic canal unroofed. Retraction of the optic nerve must follow the intermittent rule of retraction. Lateral retraction of the carotid artery is done only occasionally: the space thus created would only be small because of the Al. The posterior communicating and its perforating arteries run posterolaterally to the route of approach. The approach is easier when the proximal anterior cerebral artery (A 1) is looping or redundant and the length of the carotid artery to the carotid bifurcation is great. A

64

Aneurysms of the Posterior Circle of Willis

clip with a longer blade is more often necessary than in the route along the lateral side of the carotid artery because the clip-applier cannot be inserted into the narrow opticocarotid space (Case 28). (3) The route above the carotid bifurcation: This route is chosen only in the rare case when neither of the two above routes can be used. It is facilitated when the length of the intracranial portion of the carotid artery is short and the At is not stretched. Behind the carotid bifurcation many perforators are found including the posterior communicating and anterior choroidal arteries. These arteries must be retracted laterally with a tapered retractor following the intermittent principle. They are often in a bundle, which it is better not to separate when retracting (Case 34). 2. The Sub temporal Approach. We use this approach for all basilar trunk ancurysms and for those basilar artery ancurysms in an acute stage, or with the dome pointing posteriorly, or accompanied by circulation deficits or a previously clipped ancurysm in the carotid artery. A lumber drainage is instituted preoperatively when the operation is not done in an acute stage. An anterior temporal eraniotomy is made and as much as possible of the lateral bone edge is removed. The temporal lobe must be retracted gently and slowly; patience when retracting the temporal lobe and while draining CSF is important. (1) Approach to an aneurysm in the distal basilar artery: Sectioning of the tentorial edge is unnecessary. The oculomotor nerve is protected by covering it with a small cotton patty and holding it down gently with a tapered retractor rather than retracting with a hand-held suction. A suction held in the surgeon's non-dominant hand may easily damage the nerve. The anatomical relationships of the posterior communicating and the posterior cerebral arteries appear more complicated than in the frontotcniporal approach. (2) Approach to a basilar trunk aneurysm: The temporal eraniotomy is made a little more posteriorly. Slightly less retraction of the temporal lobe is necessary than in [he subtemporal approach to a basilar bifurcation aneurysm. When the tentorium is cut

Fig. III-JO. An approach between perforators of the posterior communicating artery is indicated when (/) the PI is unusually short, (2) the posterior communicating artery is strongly stretched, and/or (.?) the posterior communicating artery is large and strongly protruding laterally

the trochlear nerve should not be injured. When this nerve is hidden under the tentorium, the latter is cut at the point posterior to where the nerve goes behind it, or the location of the nerve is first ascertained with the aid of a mirror. The oculomotor nerve generally presents no problem. But if it gets in the way during the procedure, the nerve should be lightly retracted with a 2 mm spatula connected to a selfretaining retractor rather than moved back and forth w i t h < a suction or other instrument. The tentorium should be opened wide. Removal of the petrosal edge sometimes helps to visualize the aneurysm. Direct retraction of the pons is occasionally necessary. _i

Fig. Ш-11. Perforating arteries around the basilar bifurcation (see text)

65 3. Preservation of the Perforating Arteries Around the Aneurysm. The majority of postoperative complications result from damage to these perforators. Perforating arteries shrink and become very small due to mechanical stimulation during dissection; nevertheless, it must be kept in mind that they are all important and the utmost efforts should be made to preserve them. (1) The perforators from the posterior_cQrn-municating artery supply the anterior hypothalamus and thal-amus (Fig. III-ll; 1). It is not difficult to preserve them, but even if some are injured the complication due to a small lesion in the thalamus is usually transient. (2) The perforators branching from the PI segment of the posterior cerebral artery !

supply the posterior thalamus, and are located around the basilar bifurcation aneurysm (Fig. III-ll; 2). Although they can be preserved in the case of a small aneurysm, the perforator in the contralateral side of a giant aneurysm is often clipped accidentally. (3) The perforators originating from the dorsal side of thebasilar artery supply the peduncle (Fig. III-11; 3). Injury to these is the most serious, causing hemiplegia and severe disturbance of consciousness. Clipping of an aneurysm projecting from the dorsal side of the basilar artery toward the occipital involves a high risk of obliterating them, possibly resulting in fatal deficits. It is important to remember, especially in the surgery of basilar aneurysms, that the tips of the clip should not extend past the far end of the neck.

1 Basilar Bifurcation Aneurysm Case 24 Anteriorly Projecting Aneurysm (rt)

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This 58-year-old man had a mild SAH 11 days before the operation. At the time of surgery his neurological condition was normal except for a slight headache. Operation. A right frontotemporal craniotomy was made. The Sylvian fissure was opened wide; the temporal bridging veins were all preserved. The right carotid artery protruded laterally but its wall was reddish and soft without evidence of sclerosis. No resistance was felt through the retractor when the artery was retracted medially. Heavy cloting was present in and around the right posterior communicating artery and the basilar bifurcation. The posterior communicating artery •was not isolated from the clots but was retracted together with the carotid artery. After meticulous dissection around the basilar bifurcation the four parent arteries (i.e. the bilateral Pis and posterior cerebellar arteries) and the aneurysm neck were visible. When we were ready to try clipping, a wider фасе was found to be necessary in the right anterior temporal

fossa to enable insertion of the clip in a relatively horizontal direction, and the temporal lobe was therefore retracted posterolaterally after the bridging veins had been sectioned from it. A straight clip 10 mm long (No. 2) was placed on the neck, preserving a perforator which was branching from the right proximal PI and running behind the neck. The postoperative course was uneventful. Comments. We have operated on four cases where the domes were projecting anteriorly from the basilar bifurcation on the lateral view of the angiogram. The operations were easier than those for aneurysms projecting upward. Retraction of the temporal lobe is not usually necessary as often as cutting of the Sylvian bridging veins, though these were sacrificed in less than about 20% of our series. Sacrifice of the veins to facilitate wide retraction of the temporal tip should be decided at the stage of dissection and clipping of the aneurysm.

68

Basilar Bifurcation Aneurysm

Case 25 Retraction of Three Arteries (rt)

The 64-year-old woman had an SAH 14 days before the operation. Operation. A right frontotemporal approach was taken. Further removal of the sphenoidal ridge was necessary after the intradural approach to the aneurysm had begun because the ridge remaining disturbed the surgeon's view. As usual, the Sylvian fissure was opened wide, and the arachnoid around the carotid artery and Liliequist's membrane were removed. Though the main bridging veins of the temporal tip were sacrificed retraction of the temporal tip was inadequate to obtain an appropriate space. The right posterior communicating artery was found to be short and stretched. The right P2 portion was unusually concave and protruded frontome-dially, overlying the basilar bifurcation area. Here three tapered retractors were applied to retract these two arteries; although this facilitated visualization of the surgical target the space obtained was still small. (The actual space was smaller than that shown in the picture). The retractors did not obstruct the circulation through the carotid and posterior cerebral arteries but they appeared to be compromising a couple of smaller perforators from the posterior communicating artery. The principle of intermittent retraction was followed

even for these small perforators. The right PI segment was very short and strongly adherent to the aneurysm body, and a small but critical perforator was located between the right PI and the aneurysm, which made the procedure extremely difficult. Most of the operating time was spent on isolating these arteries with meticulous care not to injure the aneurysm neck. During the dissection in this region I explored the space between the right superior cerebellar artery and the right P1 and found there the right wall of the bottom portion of the aneurysm. I thus found a way in which the aneurysm could be obliterated together with the right PI, should it rupture prematurely. In the meantime, the difficult dissection between the aneurysm neck and right P1 was steadily advancing. The left side of the aneurysm and the left P1 segment were easily isolated. A straight clip of 18mm in length was placed on the neck. A piece of muscle was interposed between the right Cl and the spring portion of the clip to prevent injury to the carotid artery. The operation time was four and a half hours and blood-loss was less than 200 ml; this was one of the longest operations for a basilar artery aneurysm. The postoperative course was uneventful except for a transient slight oculomotor paresis on the first night.

69

1 Posterior communicating artery 2 Optic tract

70

Basilar Bifurcation Aneurysm

Case 26 Clipping Between Perforators (rt)

This 46 year-old woman had an SAH 2 weeks before the operation. At the time of operation she was free of neurological deficits. Operation. A right frontotemporal craniotomy was made and as much of the sphenoidal ridge as possible was removed. The brain was relatively tight. Fortunately the right carotid artery was beautifully reddish and not protruding laterally, indicating the absence of sclerosis of the arterial wall. An unruptured aneurysm was found on the posterior side of the right carotid bifurcation. This was easily isolated from the surrounding tissues and was just covered with a cotton patty. We then continued our approach to the basilar bifurcation aneurysm. When the right carotid artery was retracted medially we avoided retracting the portion containing the aneurysm. The right posterior communicating artery was found to be maximally stretched so a space was made between the perforators branching from it. The tapered spatula retracting the carotid artery was inserted deep, behind the right optic tract. Three perforators were found on each side of the aneurysm. All the parent and perforating arteries were isolated without difficulty. While the posterior communicating and its perforating arteries were retracted laterally with a spatula that had been retracted the temporal lobe. A straight clip of 10 mm was placed on the neck, clipping it well but causing stenosis at the origin of the right posterior cerebral artery. Although I tried to reposition the clip on the dome side the stenosis of the right P1 remained. The problem was that the

applier touched the carotid artery, and a larger space for its insertion could not be obtained. (The actual space was far narrower than shown in the picture.) As a result it was possible only to twist the applier, which succeeded only in moving the tips of the blade farther onto the dome side while the bottom portion of the clip remained where it was. The first clip was removed and a bayonet clip, No. 14, was applied. The result was satisfactory, with no stenosis of the right posterior cerebral artery. The bayonet shape enabled the clip blades to be placed on the dome side although the applier was inserted into the same narrow space as in the previous trial. The aneurysm of the right carotid bifurcation was simply clipped. Two pieces of muscle were interposed between the clip head and the oculomotor nerve. Postoperative course: The patient did not awake from anesthesia until the next morning. She experienced slight disturbance of consciousness for a week but recovered in a month. Postoperative angiogra-phy was refused by the patient. Comment. In this case the space through which we had to approach the aneurysm was very narrow, though it is drawn larger than it actually was in the picture to make the anatomical relationships clear. It should be kept in mind that a clip of different shape, such as the bayonet, can easily solve a difficulty encountered in the application of a usual straight clip. We should operate with clips of all shapes in mind and select the most appropriate one. Of course, changing the position or angle of the microscope as well as the operating chair will sometimes help in the successful clipping of an aneurysm.

71

! Right posterior cerebral artery (narrowing) I Left posterior cerebral artery _: Basilar artery

72

Basilar Bifurcation Aneurysm

Case 27 Application of Straight Ring Clip (rt)

This 62-year-old nurse had complained of headache and dizziness for a long time due to essential hypertension. A basilar bifurcation aneurysm was found incidentally by digital subtraction angiography. She had several episodes of TIAs with transient hemiparesis on the right side. Operation. A right frontotemporal craniotomy was made. The right carotid artery was markedly arteriosclerotic with a whitish-yellow wall but the carotid bifurcation and M1 portion of the middle cerebral artery were almost normal with reddish wall. Under intermittent retraction of the carotid artery the dilated basilar bifurcation was visualized. Dissection around the neck was not easy because it was wide and bulged against both P1 origins. The biggest obstacle in the operating field, however, was the large right posterior communicating artery, which was relatively short and located just above the neck. Cutting it would have made the clipping procedure much easier, but I wanted to maintain collateral circulation to the right posterior cerebral artery because there was a high possibility of causing stenosis of the proximal P1 with neck clipping. First, an „ultralong straight clip was inserted close to the neck but the tight space between the sphenoidal bone and the posterior communicating artery made this difficult (the picture does not show the real narrowness). Then a straight ring clip, No. 31 (12 mm blade, 5 mm ring), was placed on the neck preserving the posterior communicating artery through the ring. In the first two trials with the ring clip a Sano applier was used and the clip slipped off (see below). The final clipping was done with an ordinary Sugita applier with angled head. During the clipping procedure tran-

sient hypotension of about 70 mm Hg was induced intermittently for less than 10 min at a time. Postoperative course: The patient developed right hemiplegia and mental deterioration for a couple of weeks, though no abnormal density was found on the postoperative CT scan. The complications gradually improved, though six months later a mild right hemiparesis remained. Comments. (1) Sectioning of the posterior communicating artery would probably cause no postoperative neurological deficits in the majority of cases where the artery is small. However, it should not be done until all trials have proved unsuccessful. (2) A straight ring clip was used to preserve the posterior communicating artery. In the region around the basilar bifurcation we have used a ring clip far less than in other areas. With the subtemporal approach as reported by Drake and Peerless a ring clip would be used more frequently to spare the posterior cerebral artery. (3) A Sano applier II, which has small rotatable clip holders at the applier tip, is sometimes useful. One disadvantage of this applier is encountered at the moment when the clip is loosened: the clip tends to rotate and slip off the neck, especially when the latter is wide. (4) Two possible causes of the postoperative complications in tHs case~come to mind Г accidental clipping of the perforator from the left posterior cerebral artery or circulatory disturbance in the territory of the left carotid artery during transient hypotension. I believe the latter explanation to be the more likely one because the patient had TIAs before the operation and no low density was found on the postoperative CT scan.

73

74

Basilar Bifurcation Aneurysm

Case 28 Clipping Through the Opticocarotid Space (rt)

The 64-year-old woman had a severe SAH 2 weeks before the operation. At the time of surgery her neurological condition was Hunt and Hess Grade II. Operation. A right frontotemporal craniotomy was made and the sphenoidal ridge was removed as far as the orbital fat. The approach to the basilar bifurcation aneurysm was very difficult for the following reasons: 1. An aneurysm found in the right middle cerebral artery protruded anteriorly, that is, the dome faced the operating field and, in consequence, the Sylvian fissure could not be opened wide and neither the frontal nor the temporal lobe could be retracted enough. 2. The right carotid artery protruded laterally, so that an approach from the lateral side of the carotid artery was impossible. 3. Massive hard clots occupied the basal cistern and covered the target arteries and perforators. Hence, the approach between the right optic nerve and the carotid artery (the opti-cocarotid space) was chosen, retracting the optic nerve medially. In retrospect, the optic canal should have been unroofed because the traction on the optic nerve was excessive. The gentle looping of the right Al segment helped the approach very much. Two or three very small perforators from the carotid artery to the optic nerve were sacrificed. In the bottom of the operating field we encountered two difficulties: high position of the basilar bifurcation and obstruction by the aneurysm of the left posterior cerebral artery, which was only identified after the aneurysm had been collapsed with

a clip. First, the longest ordinary clip (18 mm, No. 18) was tried but it could not be inserted close to the aneurysm because the head of the clip applier was larger than the opticocarotid space. An ultralong clip of 25 mm (No. 19C) was then applied. The ultralong blade enabled insertion of the clip even through the head of the applier was outside the opticocarotid space. However, it was not possible to keep both blades of the clip in view simultaneously because of the very narrow operating field. The first clipping was unsuccessful because the head of the applier touched the anterior clinoid process, causing the applier to be pulled upward when the clip was loosened. When the second trial was made the systemic blood pressure was lowered by Trimethaphan (Arfonad) to 50 mm Hg for a few minutes; the transient hypotension made clipping very easy. After the basilar artery aneurysm had been clipped the right middle cerebral aneurysm was obliterated. Comments. (1) An ultralong clip is absolutely indispensable in certain cases when we approach a basilar artery aneurysm through the narrow space between the optic nerve and the carotid artery as well as in the lateral approach of the carotid artery. It often happens that the head of the clip applier cannot be inserted into the opticocarotid space which is narrower than the applier. When a longer clip is used the head does not block the surgeon's view. The large shadow on the postoperative angiogram, though, is certainly grotesque. (2) In 15% of our series of the basilar artery aneurysm the approach was made through the opticocarotid space.

75

76

Basilar Bifurcation Aneurysm

Case 29 Puncture of Body (rt)

This 47-year-old woman had an SAH 12 days before the operation. She developed mild liver dysfunction but was neurologically sound. Operation. In the usual way, the right sphenoidal ridge was removed as extensively as possible till the orbital fat was partially seen. The right carotid artery was soft without arteriosclerotic change but protruded laterally. First, an approach from the lateral side of the carotid artery was attempted. However, only the right side of the aneurysm could be seen even with medial retraction of the carotid artery. We therefore approached the aneurysm through the opticocarotid space. Fortunately this was wide and all the important perforators from the posterior communicating and carotid arteries were easily dissected and preserved. The aneurysm was fully round and protruded anteriorly. Dissection around it was not difficult with the exception of the right proximal posterior cerebral artery (PI), which was strongly adherent to the base of the aneurysm. As the angiogram had shown, the right posterior communicating artery was large and was the main feeder to the right posterior cerebral artery, while the right PI was small. I thought therefore that isolation of the right P1 from the aneurysm was unnecessary and that it might be clipped together with the aneurysm. First an ultralong clip of 25 mm was placed on the middle portion of the body, including the right P1, but it slipped toward the basilar bifurcation, resulting in stenosis of the left PI. Without removing the clip I punctured the body, which however only partly collapsed.

A second clip was placed on the dome side but it also slipped toward the first because the aneurysm was still receiving a partial blood supply from the distal side of the right P1 and had not become completely slack. The distal PI was clipped without removing the first clip; this time puncture made the aneurysm collapse completely (Fig. B). The right PI could now be easily isolated. An ultralong clip of 21 mm (No. 19 A) was positioned a little on the dome side of the collapsed aneurysm preserving both Pis. The first clip on the neck and the temporary clip on the distal PI were removed. A small residual neck remained near the bifurcation which was seen on the postoperative angiogram. During these procedures the systolic blood pressure was unintentionally lowered to about 40 mm Hg for 15 min with a high concentration of halothane in an attempt to induce a mild hypotension. Postoperative course: The patient's consciousness was disturbed for three days and then gradually improved. Bilateral oculomotor nerve palsy continued for 3 months and then improved to partial paresis. Comments. This aneurysm was one of those large basilar artery aneurysms which could be clipped. The postoperative complication of the third nerves in this operation we suspected to have been caused by accidental clipping of some perforators behind the aneurysm, leading to midbrain ischemia. They could have been found and preserved, had I checked the space after clipping. It would not have been difficult because the aneurysm was completely collapsed, although the clip head may have hindered manipulation in the narrow field.

77

I

78 __ Basilar Bifurcation Aneurysm Case 30 Undipped Aneurysms (rt)

Case 30-1. This 58-year-old woman had suffered from vertigo and double vision due to bilateral abducens palsy for the previous few months; there was no episode of SAH. Operation. A large right frontotemporal craniotomy was made. A pterional-transsylvian approach was taken. The right carotid artery was soft and protruded slightly in the lateral direction. The aneurysm could be seen with gentle retraction of this artery. The basilar artery was already dilated below the origin of the superior cerebellar artery (SCA). The aneurysm hid the proximal segment of the right oculomotor nerve. The four vessels, bilateral SCAs and P1 s, were all branching from the aneurysm body, which projected posteriorly (occipi-tally). Clipping was thought to be impossible with this approach, so a subtemporal approach was tried. Here too, however, it was impossible to expose the body sufficiently to clip

it because by this time brain had become tight. Postoperative course: Immediately after the operation a hematoma was found in the right temporal lobe on CT scan; it was evacuated after reopening the bone flap. For one week the patient was semicomatose with right oculomotor palsy and hemiparesis, which gradually improved. One month later she could walk with mild hemiparesis. Two years later she died from a severe SAH. Comment. In the majority of cases the operative findings can be anticipated from the preoperative angiogram. In this case I should not have made a direct approach from the frontotemporal route because the branching of the four distal vessels from the body was visible on the angiogram and the dome was projecting posteriorly to the basilar artery. It might have been possible to clip successfully from the lateral side via a subtemporal approach.

79

: I ? 4

Basilar artery Right superior ccrebellar artery Left superior cerebellar artery Right posterior communicating artery продолжение

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80

Basilar Bifurcation Aneurysm

Case 30 Undipped Aneurysms (rt)

Case 30-2. This 65-year-old woman had developed disturbance of consciousness two months earlier and was getting worse. Advanced hydrocephalus due to obstruction of the third ventricle by a huge aneurysm was the cause of the severe neurological deficits. After ventriculoperitoneal shunt she made a remarkable recovery but slight disorientation remained. Operation. A right frontotemporal craniotomy was made. The Sylvian fissure was opened wide. The temporal bridging veins were sacrificed, in this case, at the initial stage to mobilize the temporal lobe because the aneurysm was located extremely high. The posterior communicating artery was small, running in the center of the operating field. It was cut near its junction with the right posterior cerebral artery, which created a wide space. The basilar bifurcation was visualized relatively easily by medial retraction of the right M1 segment. The four arteries, i.e. the bilateral superior cerebellar and pos-

terior cerebral, were clearly identified but all four branched not from the basilar artery but perpendicularly from the wall of the aneurysm itself. The biggest problem was that the body of the aneurysm was hidden behind critical structures such as the hypothalamus and mammillary body and only the neck was visible even with maximal retraction of such structures, including the optic tract. If the aneurysm body had been widely isolated it would have been possible to puncture it with the basilar artery temporarily clipped and to place a clip on the body far from the neck. Actually no attempt at clipping was made because the space was too narrow. Postoperative course: The patient awoke uneventfully. She was slightly disoriented but was able to lead an almost normal life. She died suddenly 4 months later. Comment. If the aneurysm had been located a little lower, or if sectioning of the structures covering the body had been possible, the body could have been clipped.

81

1 Basilar artery 2 Right superior cerebcllar artery

3 Left superior ccrcbellar artery 4 Right P! 5 Left Pl

2 Basilar-Superior Cerebellar Artery Aneurysm

General Considerations

,

The approach to aneurysms based at the origin of the superior cerebellar artery (SCA) is, with a few exceptions, technically easier than that to aneurysms in the basilar bifurcation. Most of such aneurysms are located between the SCA and the posterior cerebral artery. Low position of the neck by 3 or 4 mm from the basilar bifurcation makes the approach easier. The fact that the aneurysms are usually located on the side of

the approach and do not extend beyond the basilar artery also facilitates the approach. The number of perforators around the aneurysm is less and their preservation is easier than those around a basilar bifurcation aneurysm. The side for the craniotomy is decided according to the side of the aneurysm in relation to the basilar artery except in an unusual case where the artery is situated too far laterally. In the majority of cases an approach can be made in the lateral side of the carotid artery. Postoperative mortality and morbidity are lower than for basilar bifurcation aneurysms in our series.

Case 31 Double Clipping (rt)

This 52-year-old man developed a mild Weber's syndrome, with right oculomotor nerve paresis and left hemiparesis for the previous few months. He had no SAH. Operation. A right frontotemporal approach was made as usual. The right carotid artery was found to be yellowish but was soft enough to allow medial retraction. The right oculomotor nerve was not seen; it would most likely be located

posterolateral to the aneurysm. A large aneurysm neck occupied the junction of the right superior cerebellar artery (SCA) and PI. The left SCA and PI were difficult to see because the basilar trunk had apparently rotated to the left. At first the aneurysm obstructed the view of the proximal segment of the right PI. It had two portions: one smaller portion on the neck side was soft and had a red face with a thin

83

1 Basilar artery 2 Right superior cerebellar 3 Right Pt

4 Right posterior perforators

wall, while the larger portion of the body was hard like a stone and 90% of it was hidden under the temporal lobe and tcntorium. Dissection around llie neck was easy because the aneurysm had not ruptured. First, a bayonet clip 12 mm long (No. 14) was placed on the body of the smaller portion as near the neck as possible. Clips of various shapes were tried to obliterate the residual portion of the neck because it was not a simple shape and was located in a narrow space. Though a J-shapcd clip seemed the most suitable, il was impossible to insert a clip with such a large curved blade. As the second best choice a medium-sized bayonet clip 1 0 m m long (No. 13) was applied, resulting in successful obliteration except for a very small wall, which was covered with a piece of Bemsheets. Two pieces of muscle were interposed between the clips and the carotid artery. Comments. Double clipping of the neck is often used in unusual aneurysms which do not have a simple neck. I recommend a bayonet type as the first clip when the aneurysm is located in a narrow operating field. If the blade of a J-shapcd clip had been shortened by the method which is explained in the next case the double clipping would have been unnecessary or the neck would have been completely obliterated. The operation was performed before 1 conceived the method of intraoperative shortening of the blade.

artery communicating artery and its

84

Basilar-Superior Cerebellar Artery Aneurysm

Case 32 Intraoperative Shortening of the Blade (rt)

This 22-year-old man had been operated on for a distal anterior cerebral artery aneurysm which had ruptured. An aneurysm in the right superior cerebellar artery was unruptured. His father also had had an SAH and was found to have an aneurysm which was successfully obliterated. Operation. A right frontotemporal craniotomy was done. The brain was tight in the initial stage because of the patient's age, but became slack enough later. The aneurysm was found close to the posterior clinoid process without medial retraction of the right carotid artery. The preoperative angiogram had clearly shown its unusual location. In addition to the narrow operative field, the aneurysm dome pointed toward the approach, and obliteration was impossible with a usual straight, bayonet or curved clip unlike aneurysms in the distal anterior cerebral artery. A J- or L-shaped clip seemed to be the best selection in this case. The distal end of the blades, however, was a little too long to be passed through the narrow space defined by the posterior clinoid, the third nerve, and the middle cerebral artery. One possible solution to this difficulty was to remove the posterior clinoid process. Rather than do this, however, I shortened the tip of a J-shaped clip, No. 23, by about 2 mm with a diamond drill; the procedure was completed within 2 min. The shortened clip could be inserted easily and obliterated the aneurysm without any trouble. Postoperative course: uneventful.

1 Basilar artery 2 RighL superior eerebellar artery 3 Right P,

Comments. (1) Cutting the blade tip by only 1 mm made clipping very easy. We should keep in mind the method of intraoperative shortening of the blade because the variety of the clips is limited in both shape and length. Intraoperative bending or reshaping of the blades may, however, be dangerous and is not recommended. (2) The brain of a young patient is usually very tight at the beginning of the operation. However, a gentle and slow retraction will provide an ample space because the young brain is soft and elastic. Contrarily, the aged brain is already slack but much care should be taken when retracting it because it is hard and less tolerant to external force. (3) In my experience the basilar bifurcation is lower in young people than in the elderly. Hence the aneurysm was located very close to the posterior clinoid process in this case.

86

Basilar-Superior Cerebellar Artery Aneurysm

Case 33 Direct Retraction of Aneurysm (It)

M

This 71-year-old man fell from a motorbike and sustained head injuries. On admission a high density was found in the left thalamus on a plain CT scan, which was misdiagnosed as a posttraumatic hematoma or infarction. It did not change during the follow-up study, however, and angiography showed it to be an aneurysm. He had developed mild palsy of the left oculomotor nerve and slight right hemiparesis several days before the head trauma. Operation. A left frontotemporal craniotomy was made. The brain was exceptionally tight like that of a young man, though the intraoperative water-balance was 800 ml less input than output. Fortunately the left carotid artery was not sclerotic and was retractable medially without resistance, again like a young patient. Three tapered retractors were applied to three different structures: the carotid artery, posterior cerebral artery, and temporal lobe. The retractor on the temporal lobe was moved down to directly retract the aneurysm away from the left PI in the final stage for clipping. The most difficult procedure was the dissection between the aneurysm and the left PI where strong adhesion was encountered even in this unruptured aneurysm. After much time had been spent on the dissection a dark space behind the left PI and the aneurysm was seen. An 18mm straight clip was placed on

the neck. During insertion I felt a fine resistance at the tip between the aneurysm and PI. Although the clip closed well enough it seemed to be positioned incorrectly. Bleeding occurred at the time of second closing of the clip probably because it was positioned a little too shallowly. As the bleeding was controllable with the smallest suction the clip was immediately advanced a little further and moved close to the basilar artery. Obliteration was successful. The entire period from initial insertion of the clip to the final closure was perhaps less than 10s. All perforators around the aneurysm were preserved. Postoperative course: Subdural effusion was found for a few weeks. For one week mild disorientation was noticed with slight oculomotor nerve paresis. One month later he had recovered fully without Weber's syndrome. Comment. We use direct retraction of the aneurysm and the parent artery, which leaves both hands free for dissection and suction. A steady retraction of the aneurysm with a tapered brain retractor connected to a self retaining retractor is safer than pushing with a suction. I have experienced slight intraoperative bleeding like that in this case in less than 5% of our series, during dissection between the aneurysm and the parent artery or when dissection around the aneurysm was not complete as in this case.

8'

1 Basilar artery 2 Left superior cerebellar artery 3 Left?!

Basilar-Superior Cerebellar Artery Aneurysm Case 34 Approach Above the Carotid Artery Bifurcation (rt)

This 57-year-old man was admitted to our hospital immediately after an SAH. Right carotid angiography showed an aneu-rysm at the MCA trifurcation which was considered to have ruptured and was clipped within 24 h. Postoperative four vessel angiography revealed two more aneurysms at the origin of the right SCA and in the left MCA beside the clipped one. An approach to the basilar aneurysm was made 1 month later, when the patient's liver function had normalized. Operation. The right frontotemporal craniotomy wound was reopened and the sphenoid ridge was further cut away close to the anterior clinoid process. Wide opening of the Sylvian fissure was limited by the previously clipped MCA aneurysm, which projected laterally and was embedded in the temporal lobe; it was not touched. The main trunk of the MCA was exposed only on the frontal side. The intradural portion of the ICA was found to be unusually short and sclerotic. Furthermore, the back wall of the ICA adhered to the posterior clinoid process. The opticocarotid space was narrow, making approach difficult in this direction, but the basilar aneurysm was partially visualized through it. We realized that an approach either lateral or medial to the ICA was not feasi-

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ble. The A1 segment of the anterior cerebral artery was freed from the base of the frontal lobe. The anterior choroidal artery and posterior communicating artery with its branches were found running from behind the ICA to the base of the brain in the form of a wide bundle. Without separating these fine arteries it was possible to visualize both the basilar artery and aneurysm. The neck of the basilar aneurysm was easily dissected from the PI segment, but dissection between the aneurysm and the superior cerebellar artery was much more difficult. The aneurysm appeared to arise from the origin of the superior cerebellar artery. Although we were able to visualize these structures by changing the angle of the microscope, placing a clip was difficult because of the narrow exposure, encumbered with the bundle of perforators and the posterior communicating artery. However, direct retraction with a 2 mm tapered brain retractor provided ample exposure through this opening. Dissection around the neck of the aneurysm and clipping took approximately 30 minutes, with the bundle of perforating vessels continuously retracted. Clipping was performed using an 18mm straight clip, No. 18, with a straight applier. The first trial resulted in kinking of the

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90

Basilar-Superior Cerebellar Artery Aneurysm

Case 35 Undipped Aneurysm with Bilateral Approach

rt. CAG lat.

This 65-year-old woman had a severe SAH three weeks before the first operation. At the time of operation her neurological condition was Grade II. 1st Operation. A left frontotemporal craniotomy was made. The approach to the basal cistern was difficult and troublesome for the following reasons: (1) The left carotid artery protruded so far laterally that it was adherent to the oculomotor nerve. (2) A small first branch of the middle cerebral artery, the temporal polar artery, tore away from the parent artery with just gentle retraction of the temporal lobe; the bleeding was easily controlled. (3) The dome of the aneu-rysm pointed toward the approach. (4) The posterior communicating and its perforating arteries were covered with old clots and adhered to the surrounding tissues. First, the aneu-rysm was approached through the left opticocarotid space. The left SCA, right P1 and broad neck of the aneurysm were found but the left PI could not be seen. The route through the space distal to the carotid bifurcation was also difficult because there were so many perforators here (A). Next, an approach from the lateral side of the carotid artery was made with medial retraction of the carotid. The left posterior communicating artery was of small diameter and was short, tight and partially embedded in the dome, to which clots had made its perforators adhere strongly. Isolation of these arteries, therefore, was almost impossible. With this approach the left SCA and the neck portion near the left SCA were identified

but the left proximal PI could not be seen because it was behind the body (B). Any further approach was abandoned. 2nd Operation. A right frontotemporal approach was made 3 weeks after the first operation. The right carotid artery was not protruding laterally in contrast to the left carotid. A large space could be obtained by the approach in the lateral side of the carotid artery. The left SCA, right PI, neck portion and perforators from the basilar bifurcation were all clearly seen. The left posterior cerebral artery (PI), however, could not be identified even with maximal retraction of the structure behind the right optic tract, which probably retracted even the mammillary body. The neck of the aneurysm went from the origin of the left SCA to the distal end of the left P1 segment (C). Partial clipping of the proximal side of the neck including the left PI could have been done easily, but good collateral circulation from the small left posterior communicating artery could not have been expected and the possibility of ischemic complications in the territory of the left posterior cerebral artery was therefore high. Postoperative course: Uneventful. The patient is working 3 years later. Comments. (1) The aneurysm had a very wide neck extending from the left SCA to the mid-portion of the left P1 as suspected from the angiogram. Had the left posterior communicating artery been bigger, clipping of the aneurysm including the P1 would have been possible. I have successfully obliterated many other aneurysms with a neck as broad as

91 1 Basilar artery

2 Left superior cerebellar artery 3 Left?!

4 Right superior cerebellar artery

5 Right P1 6 Left posterior communicating artery

_

7 Right posterior communicating artery

in this case; meticulous dissection between Ihc aneurysm and PI allowed successful clipping though no space was seen on the angiogram. This was the only case in our series of 29 SCA aneurysms where the aneurysm could not be clipped. The opcereration was undertaken six weeks after the SAH and at a ::me when the prospective mortality with surgery was less than 30%; we should not try such an adventurous procedure when the risk of mortality is above 30%. This aneurysm should be grouped with those of the PI segment rather than the SCA. (2) The anatomical features of the carotid artery, whether it is protruding laterally or whether it is sclerotic, are

important in selecting the route to the aneurysm in and around the basilar bifurcation, asMn this case. It is usually possible to determine a feasible approach by assessing the internal carotid artery on the anteroposterior view of the angiogram. The distance of the carotid bifurcation from the midline is the most important factor determining the degree of lateral protrusion of the carotid artery; if the distance is great an approach lateral to the carotid artery would be difficuIt, especially when the artery has severe arteriosclerotic change (X-ray picture, arrows in the lower column). Tn the latter kind of case an approach through the opticocarotid space can be taken, or if the intracramal portion of the carotid artery is short a route distal to the carotid bifurcation can be tried. Of course, a subtcmporal approach would be a good aternative.

92

Basilar-Superior Cerebellar Artery Aneurysm

Case 36 Distal Superior Cerebellar Artery Aneurysm (It)

This 47-year-old man had an SAH two weeks before the operation. No neurological deficits were observed at the time of surgery. Operation. A left frontotemporal craniotomy was made. The Sylvian fissure was opened and the left temporal lobe was retracted laterally. The approach to the aneurysm was made in the lateral side of the left carotid artery, and I discovered that I had made a mistake in taking the transsylvian approach because although the proximal parent artery of the aneurysm was visible the aneurysm and its distal side were hidden by the tempral lobe. All the bridging veins of the temporal tip were cut and the temporal lobe was retracted posteriorly with removal of the temporal tip. The tentorium was opened posterior to the aneurysm, which was strongly adherent to the oculomotor nerve and peduncle. Dissection of the adhesion around the aneurysm was most difficult. A bent

clip, No. 4, was inserted from the distal side of the aneurysm as parallel to the parent artery as possible; the clipping was successful. During dissection of the adhesion and clipping the oculomotor nerve was moved strongly back and forth. Postoperative course: Uneventful except for left third nerve palsy which persisted for 4 months. Comment. As this operation was one of the earliest in our series of vertebrobasilar artery aneurysms, two mistakes were made. The operation would have been much easier if a subtemporal approach had been taken, and it would have been unnecessary to sacrifice the bridging veins and temporal tip. If the oculomotor nerve had been directly retracted with a tapered retractor during dissection and clipping, as we did in later cases, the postoperative palsy would have been minimal.

93

1 Basilar artery 2 Left superior cerebellar artery 3 LeftP2 4 Left posterior communicating artery

3 Proximal Posterior Cerebral Artery (PI) Aneurysm

Case 37 Trapping of PI (rt)

Angiogram: (T) Before 1st operation. (2) One month after 1st operation. (3) 6 months after 1st operation. (4) After 2nd operation.

This 31-year-old man developed Weber's syndrome with right oculomotor nerve palsy and left hemiparesis 3 months before the operation. 1st Operation. In the usual manner, a right frontotemporal approach was made. Medial retraction of the right carotid artery made visible a large double-domed aneurysm. One dome was located on the medial side of the P1 segment and the other between the right superior cerebellar (SCA) and posterior cerebral arteries (PCA). The oculomotor nerve was found to be very thin and almost disappeared over the bottom of the aneurysm body. The posterior communicating artery was not directly connected with the PCA but with the aneurysm neck (A). After the larger aneurysm in the lateral side of the P1 was clipped repeated trials to obliterate the smaller aneurysm on the medial side of the P1 were made but were unsuccessful because none of the clips available at that time could be inserted perpendicularly to the neck but only obliquely and they slipped distally (B). If a ring clip had been available the neck would have been obliterated successfully because the

force of the blade is greater, and the origin of the posterior communicating artery could have been spared. The first operation had ended in partial clipping of the aneurysm located between the right superior cerebellar artery and the PI segment of the right posterior cerebral artery. The postoperative course after the first operation: Weber's syndrome improved moderately. About 6 months later, however, the patient complained of worsening diplopia and left hemiparesis. The second operation was done 7 months after the first. 2nd Operation. The approach was made through the same route as the previous operation. We encountered considerable trouble in the initial stage, as the spring portion of the clip applied in the previous operation was strongly adherent to the right carotid artery, making it difficult to remove; it was separated from the artery only after gentle and patient dissection. It was also blocking any further approach to the aneurysm. The main aneurysm located between the right SCA and PCA at the previous operation was found to have undergone granulomatous change and so the clip could be easily removed without any resistance or bleeding. The previously undipped portion of the aneurysm had enlarged markedly. Trapping of the P1 segment, where the neck was located, was carried out this time with special attention to maintaining the circulation from the right posterior communicating artery to the PCA: the distal clip was placed sufficiently far from the junction of the posterior communicating artery and the PCA (C). Postoperative course: The immediate postoperative course

95 jftcr the second operation was uneventful without any additional neurological deficits. Weber's syndrome slowly im-

I

I Basil ar artery I Right superior cerebellar artery 5 Right P2 4 Right posterior communicating artery

proved and one year later the patient had recovered fully. Comments. This was an unusual large aneurysm originating from the PI segment of the posterior cerebral artery. The most difficult problem was how to maintain the circulation from ihc posterior communicating artery to the posterior cerebral artery when the PI segment was trapped because the posterior communicating artery was not connected directly with the PCA b u t with the aneurysm neck. That we overcame the problem successfully is suggested by the lack of visual field defects postoperatively and of any low density on the С Т scan.

96 Case 38 Angled Ring Clip: Associated with AVM (It)

Proximal Posterior Cerebral Artery (PI) Aneurysm This 45-year-old man had an attack of headache and vomiting while taking a bath 3 weeks before the operation. A giant AVM was found in the left occipital lobe and an aneurysm in the left posterior circulation on the preoperative angiogram. As the preoperative CT scan showed a high density located not in the occipital area but in the basal cistern the bleeding was thought to have occurred from the aneurysm. Operation. A left frontotemporal craniotomy was made. The left Sylvian fissure was opened very wide. One Sylvian vein which was a drainer from the AVM was big and reddish, though its tension was not high. The left carotid artery protruded laterally and touched the tentorial edge. Although medial retraction of the carotid was thus impossible, the optico-carotid space was wide. The aneurysm body was easily found in the space surrounded ventromedially by the left carotid artery, posterolaterally by the left posterior communicating artery, ventrolaterally by the left optic tract and ventrally by the left A1. In the initial stage, the aneurysm seemed to have originated from the posterior communicating artery; it projected upward and the neck was hidden by the body of the aneurysm. While dissecting around it the neck could be identified at the proximal P2 portion. The aneurysm pushed the

posterior communicating artery medially and partially elevated the optic tract. Numerous perforators branching off the posterior communicating artery adhered strongly to the top of the dome. The posterior communicating and anterior cerebral arteries also were adherent to the dome, but it was decided not to try to isolate them because of the possibility of rupture before the proximal parent artery had been secured for temporary trapping. The proximal side of the parent artery was the P1 segment which could not be seen even after several attempts. An oblique-angled ring clip, No. 35 (5 mm blade, 5 m m ring), was placed on both sides of the proximal Al which was preserved within the ring. During application of the clip the proximal sides of neither the neck nor the parent artery were visible, and we were afraid of rupture of the aneurysm or accidental clipping of critical vessels. Even after clipping, the proximal parent artery could not be seen but the aneurysm slackened slightly and its color darkened as shown in the picture. I hesitated to puncture the body. Immediately after the operation angiography and CT scan were done; the aneurysm had disappeared without stenosis of the parent artery. On the first night right hemiparesis and mydriasis of the left ) pupil were observed, but the patient soon recovered fully.

1 Basilar artery 2 LcftP2

3 Left posterior communicating artery 4 Left optic tract

Comment. In this case it was impossible to visualize not only the neck but also the proximal side of the parent artery. Perhaps a subtemporal approach would have been better because the neck and parent artery would then have been visible. At any rate the angled ring clip proved very useful, although the procedure was hazardous because the position of the blade tip was unclear at clipping.

98

Proximal Posterior Cerebral Artery (PI) Aneurysm

Case 39 Associated with Agenesis of the Carotid Artery (It)

This 43-year-old man had a mild SAH three weeks before the operation. The four-vessel study showed agenesis of the left carotid artery. Operation. A left frontotemporal craniotomy was made. What we took to be the proximal internal carotid artery was very small and it was unclear whether there was any blood flow. There was a possibility that it was in fact the ophthalmic artery. The left posterior communicating artery, on the contrary, was as big as a normal carotid artery and certainly larger than the middle cerebral artery. These arteries were yellowish with hard wall. An approach from the lateral side of the posterior communicating artery failed to make the an-eurysm visible because the posterior communicating artery as well the middle cerebral protruded laterally. Therefore the medial side of the carotid and middle cerebral arteries (Ml) were dissected. In the space medial to the M1 the aneurysm was found projecting medially from the medial side of the posterior communicating artery and behind many perforating arteries. It was yellowish and its wall appeared to have athero-matous changes. A straight clip 10 mm long was inserted between the M1 and A1. The clipping procedure itself was easy, but we made a great mistake in not checking around the aneurysm after clipping. A piece of muscle was interposed between

the spring portion of the clip and a small perforator which was being pressed by the clip and a small perforator which was being pressed by the head of the clip. Postoperative course: On the first and second postoperative day the patient appeared normal but on the third day he developed right hemiparesis and disturbance of consciousness. The postoperative angiogram was performed more than 12 h after the paresis appeared. It showed the clip to have obliterated the left PI and that the blood circulation of the left middle cerebral artery was being maintained through the collateral from the right carotid artery (A). A large low density area was found in the left occipital area on the CT scan (D). Later normal consciousness returned but hemiplegia persisted. Comments. This was a very unusual aneurysm originating from the anteromedial side of the junction of the left posterior cerebral and posterior communicating arteries, combined with agenesis of the ipsilateral carotid artery. We mistakenly judged from the preoperative angiogram that the origin of the aneurysm was in the mid-portion of the posterior communicating artery, and this misunderstanding was not corrected until we saw the postoperative angiogram. Had the region behind the aneurysm been inspected intraoperatively the accidental clipping of the left P1 could have been avoided.

99

\ 1 Left posterior communicating artery 2 Agenesis of C2 (7) or ophthalmic artery (?)

102

Distal Posterior Cerebral Artery Aneurysm

Case 40 Removal of the Parahippocampal Gyrus (rt)

This 46-year-old man had an SAH 2 weeks before the operation. At the time of surgery his neurological condition was Grade II. Operation. With the patient in the lateral position a right middle subtemporal approach was made. As the operation was carried out in an affiliated hospital and the patient's position had already been set by assistants I encountered many difficulties, since the head had been fixed incorrectly in the fixation frame and, in particular, the tilting of the head toward the left shoulder was inadequate. The lateral bone edge was removed maximally. The brain was very tight. I asked the anesthesiologist to change from artificial respiration to spontaneous respiration with added hyperventilation for a short period, and also to administer a diuretic drug, Lasix. CSF was slowly sucked from the subtemporal space because a lumber drainage had not been instituted. After waiting for more than 10 min, the brain became slack. With a minimal retraction of the temporal lobe the right trochlear nerve and superior cerebellar artery were visualized in the crural cistern. However, the segment of the right posterior cerebral artery where the aneurysm would be located was completely hidden by the medial side of the temporal lobe. Further retraction

of the temporal lobe was too dangerous because the brain was hard. In order to avoid damage to the lobe, a small portion of the cortex around the aneurysm was sucked. The ventricle was opened a few mm from the cortical surface. After egress of CSF from the ventricle, the procedure became quite easy. The aneurysm could be isolated from the adherent surrounding tissues. Under direct retraction of the body with a tapered retractor, a bayonet-shaped clip curved sideways, No. 7, was positioned on the neck. The postoperative course was uneventful with normal neurological condition. No edema in the temporal lobe was seen on the CT scan. Comments. The process of approach is strongly influenced by the position of the patient and the patient's head. Again, the head must be higher than the heart level and the position should be kept until opening of the crural cistern. Tilting of the head to the contralateral shoulder is also indispensable, as it facilitates visualization of the subtemporal surface while keeping the head above the heart level. Sacrifice of a small portion of the cortex around the aneurysm lessened the need for temporal lobe retraction in this case. Such removal should be resorted to only when further retraction of the brain would be extreme. Sacrifice of the medial subtemporal cortex causes no definitive neurological deficits.

103

\

1 Right distal posterior cerebral artery

2 Right superior cerebellar artery 3 Right temporal horn of the ventricle

104

Distal Posterior Cerebral Artery Aneurysm

Case 41 Double Clipping in a Case Associated with TIA (It)

This 56-year-old man had had TIAs for a couple of years. They occurred at times of hypotension and the angiogram showed obliteration of the left middle cerebral artery with abundant collateral circulation. Recently he had had two mild attacks of SAH within one week so the operation was planned 38 h after the second attack, though in general aneurysm surgery in an acute stage should be avoided when the patient has a major artery obliterated. Operation. With the patient in the left lateral position, the head was tilted toward the right shoulder as much as possible and the head was elevated above the heart level. After ventricular drainage was instituted in the right anterior horn a left middle subtemporal approach was performed with special attention to preserving the superficial temporal artery for bypass surgery at a future date. No big veins were found around the approach route, though a couple of small veins on the subtemporal surface were sacrificed. As one or two aneurysms were suspected to be located in the left superior cerebellar artery the tentorium was opened. When it had been cut. a mirror played a large role in finding the trochlear nerve, which was completely hidden under the tentorium. An aneurysm body was found separately from the superior cerebellar

artery. Next, isolation of the left posterior cerebral artery was started from the proximal to the neck portion. The aneurysm which had appeared likely to be a double aneurysm on the angiogram had a very curious shape. One big branch from the posterior cerebral artery was its parent artery; this was probably the ramus temporalis inferior anterior. The aneurysm was in fact one type of pseudofusiform aneurysm, having no neck. Its base was markedly wide, with the dilatation beginning at the junction of the branching artery. A first clip, No. 1, was placed on the proximal body to spare the parent artery. A second clip, No. 29 (6 mm blade, 5 mm ring), was then tried in order to cross the blade of the first clip with the ring and obliterate the distal body. However, the blades of the second clip were too long (we were afraid that the tips would penetrate the peduncle), so they were shortened about 2mm with a wirecutter and the cut edges were filed with a diamond drill. The shortened clip crossed the first clip and closed the distal body beautifully. One small perforator adherent to the dome was obliterated with the second clip. In addition to the aneurysm, the distal portion of the parent artery was dilated but the wall was apparently normal without a red face or sclerotic change. The dilated segment was covered

10

w i t h muscle. Postoperative course: A slight low density area appeared in the left temporal lobe on the postoperative CT scan for a week. Neurologically the patient was sound. Comments. (1) In patients with severe defects such as obliteration of a major artery, intentional delay in operating is recommended except when the aneurysm is located superficially. We operated on an aneurysm in the right distal posterior cerebral artery with obliteration of the right carotid artery 14 days after SAH. Postoperativcly the patient developed jft hemiparesis and disturbance of consciousness for a couple of weeks. If the patient had been operated on in an acute ^tage the deficits would have been much worse. (2) Institution of ventricular drainage is more favorable than lumbar drainage in aneurysm surgery in the acute stage because lumbar puncture is basically contraindicated for an acute ease and ventricular drainage can be maintained for several days after the operation and so helps to control the postoperative intra-cranial pressure. (3) When the skin incision is made, the intra-cutaneous branch of the external carotid artery should basically be preserved in every case, not only in those with stenosis of the major artery, because all cases with an aneurysm may need bypass surgery in the future. (4) It would be reasonable to section the whole dilated segemenl of the parent artery including the aneurysm and to anastomose the distal segment. However, in a case like the present, where the territory of the left middle cerebral artery was ischemic, disturbance of blood circulation with temporary trapping should be avoided.

1 Left distal posterior cerebral artery 2 Left superior cerebellar artery

106

Distal Posterior Cerebral Artery Aneurysm

Case 42 Giant Aneurysm: Cutting and Double Clipping (rt)

This 45-year-old man had a sudden onset of severe headache and vomiting without loss of consciousness. He developed weakness of the left leg and anisocoria (the left pupil was larger than the right). He was restless and euphoric, but gradually improved. Three weeks later he became depressive. The manicdepressive state was taken to be a typical symptom of temporal lobe involvement. The CT scan showed a massive high density in the right temporal lobe and right posterior ventricle. He underwent surgery 4 weeks after the SAH attack, by which time he was almost normal. Operation. With the patient in the lateral position, the right side of the neck was stretched to bend the patient's head to the left shoulder. A right middle subtemporal approach was taken. CSF drainage, which had been instituted via the lumbar route before the skin incision, helped the approach a great deal. Labbe's vein was outside the operating field. The medial subtemporal surface was strongly adherent to the tentorium, suggesting that the aneurysm would be close by. The adhesion made it impossible to obtain a space and it was therefore very carefully dissected from the tentorium, resulting in visualization of the proximal side of the posterior cerebral artery (PCA) and the trochlear nerve as well. Isolation of the distal side of the PCA was very difficult because it was located deep and, especially, behind the huge aneurysm, which projected toward the approach and blocked any view of the neck. After both proximal and distal sides of the PCA had been isolated for temporary trapping, the aneurysm was dissected from the temporal lobe. The lateral half of the aneu-

rysm came away by itself. After the arachnoid around the aneurysm had been cut many old clots were found in its medial side and dissection here was easy. Under temporary trapping of the PCA for 15 and 35 min intermittently, the large body with a diameter of 25 mm was cut and opened. When the organized clots mixed with hard connective tissues were partially removed, a thin capsule of a true aneurysm, which had been seen on the angiogram, was found; its diameter was about 12 mm. This too was opened. Very hard connective tissue occupied the space between the outer and inner capsules ; it was too hard to remove with suction and apparently strong enough to protect against rebleeding. We therefore decided to try to collapse the whole body rather than remove the outer portion. First, an ultralong straight clip of 24 mm was placed obliquely on the body. It would have been ideal if the blades could have been placed close to the neck parallel to the parent artery, but we had no angled ultralong clip: a straight clip could only be inserted in an oblique direction because of the narrow operating field. Secondly an angled ring clip, No. 43 (10 mm blade, 5 mm ring), was applied crossing over the first clip to obliterate the residual body without closing the parent artery. It was positioned about 6 or 7 mm from the origin of the neck. If it had been placed close to the neck it would have slipped onto the parent artery or, even if it did not slip, the parent artery would inevitably have been obliterated because the aneurysm wall was about 5 mm thick. I expected that a small residual portion would be seen on the postoperative angiogram but that there would be no

107

1 Right distal posterior cerebral artery

possibility of rerupture because the wall of the residual portion was so thick. The clips were covered with a chemical adhesive to prevent slippage. The postoperative course was uneventful except for a depressive state that lasted for a week. Comments. (1) In the initial stage of the operation the aneurysm seemed to occupy almost all the operating field: it was twice the size seen on the angiogram. and identification of the proximal side of the parent artery was very difficult. Securing this is most important. Our experience in our whole series has been that the larger the aneurysm is, the stronger is its wall and we may therefore handle a larger aneurysm a little more roughly than a small one. (2) The consecutive procedures of temporary trapping of the parent artery, evacuation of the intramural content, collapsing of the body and neck clipping are the best way to deal with a giant aneurysm. In this case the capsule and its contents around the neck portion were rather too thick to cut and remove and I was also afraid of tearing the neck during the attempt.

5 Basilar Trunk Aneurysm

Case 43 Double Aneurysm via Transsylvian Approach (rt)

rt transbra

This 58-year-old woman had two SAHs, 20 and 3 days before the operation. At the time of operation she was in Hunt & Botterell Grade II. Operation. A right frontotemporal craniotomy was made. The right carotid artery was retracted medially. The basal cistern was full of thick clots. An aneurysm between the right superior cerebellar and right proximal posterior cerebral arteries was easily isolated because it was unruptured. Clipping was deferred to toward the end. An approach to the basilar trunk aneurysm was difficult. After the right temporal lobe was posteriorly retracted, the tentorium was opened. The aneurysm of the basilar trunk was found lateral to the oculomotor nerve in the depths of the operating field. It began to bleed mildly even before it was touched. Transient hypotension of about 70 mm Hg stopped the bleeding, but when a straight clip was placed on the neck it started again. Apparently paradoxical bleeding was observed: when the clip was closed around the neck bleeding became stronger, while opening the clip reduced the bleeding. I thought the reason for this must have been clipping of the distal side of the parent artery, causing the intra-aneurysmal pressure to increase. The clip apparently slipped from the neck to the parent artery when the applier was loosened, as the applier head moved

laterally due to near-by hard structures. I therefore placed the clip more laterally, pushing the applier to the side. Bleeding stopped and the clipping was successful. The aneurysm of the upper portion of the basilar artery was easily clipped within 1 min. Postoperative course: For 6 days the patient was almost the same as preoperatively. On the 7th day she developed consciousness disturbance and high fever, and started to rapidly deteriorate. That night an internist examined the CSF by lumber tap, but it was not bloody. On the 8th day she died. Comments. This was one of two cases in our series of 140 vertebrobasilar artery aneurysms in which intraoperative bleeding occurred. Aneurysms in the acute stage have a high possibility of intraoperative bleeding because the wall of the bleeding point is still thin. In this case I made two mistakes. One was the timing of the operation. The patient had surgery on day 3 after the second SAH in Grade II. We should delay the operation for basilar artery aneurysms past day 12 except in young patients in good condition. The other was the selection of the approach. An aneurysm of the basilar trunk can be approached more easily through a subtemporal route than through a frontotemporal (transsylvian); in this case especially the subtemporal approach would have been easy because the

10'

basilar trunk protruded laterally. One week after the operation the patient became suddenly worse. Vasospasm was suspected to be occurring; there is a possibility that the lumbar tap may have aggravated the condition.

1 Basilar artery 2 Right superior cerebellar artery 3 Right P, .,

4 Right posterior communicating artery

110

Basilar Trunk Aneurysm

Case 44 Direct Retraction of the Pons (It)

This 39-year-old woman had an SAH 15 days before the operation. She complained of severe dizziness and headache. Operation. With the patient in the lateral position, a left sub temporal approach was taken. The brain was very tight because a lumbar drainage could not be instituted. After waiting for the brain to become slack with the administration of additional diuretic drugs, hyperventilation and sucking of CSF, retraction of the temporal lobe was started gently and slowly. Labbe's vein was not seen inside the operating field, but many bridging veins on the subtemporal surface were encountered and twothirds of them had to be sacrified. After the trochlear nerve was located at the medial side of the in-cisura the tentorium was widely opened. In the center of the operating field the big trigeminal nerve was visible. First, an approach to the basilar artery was made through the lateral (caudal) side of the Vth nerve, where the left abducens nerve was identified at the bottom with direct retraction of the pons. The abducens nerve was adherent to the basilar trunk but no aneurysm was found in this area. Then an approach through the medial side of the Vth nerve was taken. The basilar trunk was located deep in the medial vascular groove of the pons; it was completely hidden by the pons so a relatively strong retraction of the latter was necessary. Removal of the pyramidal edge could have lessened the retraction of the pons and the aneurysm would have been visualized a little better from the anterior (frontal) side, but the air drill was out of order. Dissection around the neck was not difficult except for isolation of many small vessels around the aneurysm. Insertion of a clip was very difficult as the space between the pons and pyramid was very narrow (though an adequate space is shown in the picture). Under strong retraction of the pons with a 2 mm tapered retractor a straight ultralong clip of

21 mm was placed obliquely on the body, but it slipped off. Next I tried to place an L-shaped clip, No. 20, parallel the basilar trunk but this was impossible because the blades were too long and they could not be shortened without a drill. Clipping was finally successful with a curved clip, No. 8. Immediately after obliteration of the aneurysm had been confirmed I found that the clip-applier could not be withdrawn; I felt a strong resistance when I tried to remove it. One of the assistants checked outside the microscope to be certain that the clip had been released from the applier but found that the opened head of the applier had stuck between the pons and the pyramid. Postoperative course: The patient was well for about 12 h postoperatively, but then started to deteriorate due to temporal lobe edema without signs of cranial nerve palsy. She recovered completely 2 weeks later without any neurological deficits. Comments. Because of the young brain, the basilar trunk was deeply hidden by the pons. Contrarily, even strong retraction of the pons caused no neurological deficits thanks to its inherent elasticity. If the patient is older such strong retraction is not permissible. I was nevertheless greatly surprised that the patient did not develop even transient symptoms of pontine damage considering the unprecedented strength of retraction. Since this experience I have tended to retract the pons and medulla a little more than in the past; I now believe them to be almost as tough as other portions of the brain. Of course, retraction of the brainstem has to be done with extreme care: intermittently and with the patient under spontaneous respiration. Drilling off of the pyramidal edge is often very helpful for approaching the basilar trunk and lessening retraction, though it could not be done in this case.

111

продолжение

продол жение

112

Basilar Trunk Aneurysm

Case 45 Vertebral Union (rt)

This 73-year-old woman had an SAH 3 weeks earlier. She developed mental dullness, and moderate hydrocephalus was found on the CT scan a few days before surgery. Operation. With the patient in the lateral position a right middle subtemporal approach was performed after ventricular drainage had been instituted. The brain became nicely slack with CSF drainage. The tentorium was cut to gain a space; it was first opened anterolaterally, upon which bleeding was encountered from the petrosal sinus, and its posterolateral portion was then sectioned without trouble. While old clots were being removed from the prepontine cistern, the aneurysm dome was soon found under the Vth nerve. The Vth nerve could not be retracted because a trial retraction caused severe cardiac arrhythmia. Further visualization of the aneurysm complex was possible only by retracting the pons; retraction was applied intermittently. The location of the aneurysm was complicated. The right vertebral artery had an anomalous fenestration from which a large AICA-PICA was branching. The bilateral vertebral arteries were found in the proximal side of the lesion. The basilar trunk was identified in the distal side of the dome. A bayonet ring clip with 5 mm blade, No. 44, was positioned on the neck, preserving the fenestrating artery through the ring. On exploration, however, the blade tips were found to have partially obliterated the parent artery in the depths. The clip was removed and its blade tips were shortened about 1.5 mm with a diamond drill. The shortened clip was

then placed without difficulty. It seemed to fit on the neck nicely without causing stenosis of the parent artery; two perforators from the accessory artery of the fenestration were well preserved. Although there was a possibility of incomplete obliteration of the neck because we saw a swirling of blood through the wall of the body, additional procedures such as puncturing the dome were deemed hazardous in this narrow and complicated field and therefore were not done. The main procedure took two and a half hours with minimal blood-loss. The postoperative course was uneventful except for a slight, transient motor weakness of the left hand on the first postoperative day. The postoperative angiogram showed that the aneurysm was satisfactorily obliterated. Comments. (1) The choice of approach in this case, subtemporal or suboccipital, was difficult because the basilar union was located high. Either route could have been taken. The subtemporal approach provided a wide working space although we were approaching from the dome side. The accessory trunk of the fenestration could have been cut to facilitate clipping, but we were afraid that the main trunk still could not be entirely visualized. With the suboccipital approach, the accessory and the AICA-PICA trunks would have prevented a satisfactory visualization of the neck, though clipping would have still been possible, probably with a ring clip. In either approach, a certain degree of pontine retraction is unavoidable. Retraction of the trigeminal nerve would have pro-

из

1 Right vertebral artery 2 Left vertebral artery 5 AICA-PICA 4 Fenestration 5 Baailar trunk

6 Petrous vein

vided better visulization of Ihe aneurvsm, which was however not absolutely necessary in this case. (2) Shortening the blade tips with a diamond drill was useful; otherwise, stenosis of the main trunk of the parent vertebral artery would have been unavoidable.

114 Basilar Trunk Aneurysm Case 46 Giant Aneurysm: Undipped (rt) This 8-year-old boy had a pons infarct 2 months before the operation. The hemiparesis of the right side had gradually improved, but a basilar trunk aneurysm found on the angiogram (A) soon after the infarct had grown larger during the two months (B), from semifusiform to true fusiform. Operation. With the patient in the lateral position, a right sub temporal approach was made. The temporal lobe was easily mobilized, preserving Labbe's vein with the aid of lumber drainage. The trochlear nerve was strongly adherent to the right superior cerebellar artery and its isolation from the artery was difficult. The tentorium was easily opened. A large aneurysm was immediately found between the pons and clivus. The trigeminal nerve had been shifted downward. The aneurysm was true fusiform, looking like a balloon catheter in the artery. Its wall on the side of the approach was reddish and thin without vasa vasorum. Many dilated red veins like an AVM were seen on the pons behind the aneurysm, probably due to disturbance of venous return by the lesion. Pushing the aneurysm toward the pons created a big gap between the pons and clivus, and the aneurysm was thus widely exposed. A suitable clipping method for this true fusiform aneurysm was not apparent, and a muscle covering was made over the approach side. We planned to obliterate the proximal parent artery in the future. During the procedures the trochlear nerve was inadvertently cut. Suture approximation of the cut ends was tried but was unsatisfactory. Postoperative course: The neurological condition was almost the same as preoperatively except for slight disturbance of right trochlear nerve function. The boy did not, however, complain of diplopia. The angiogram taken two weeks later showed enlargement of the aneurysm (C). The CT scan and angiogram taken 2 months postoperatively showed that the size of the aneurysm had not changed but more than half of the intraluminal space was thrombosed like a serpentine aneurysm (D). Therefore, with the family's consent, proximal obliteration was deferred. The boy goes to school 2 years later (E). Comments. Three rare conditions coincided in this aneurysm: its location in the basilar trunk, its being a true fusiform aneurysm, and its occurrence in an 8-year-old boy. The incidence of each of the three conditions is less than 1 %; this means a coincidence of the three conditions of less than 0.000001% in all aneurysms. We are still planning temporary obliteration with an intravascular balloon catheter with which neurological deficits can be anticipated before permanent obliteration.

115

1 Basilar trunk

2 Right superior cerebeliar artery

6 Vertebral Artery Aneurysm

General Considerations With vertebral artery aneurysms there is a great difference in technical difficulty between a shallowly-located simple aneurysm and a deeply located or fusiform one. All the cases of vertebral artery aneurysm in this series were approached from a unilateral suboccipital cranicctomy. 1. Timing of surgery: Acute surgery is permissible in a wider range of neurological gradings after SAH than is the case with hasilar artery aneurysms, which have stricter indications for surgery. 2. Anesthesia and positioning: Under general anesthesia spontaneous respiration is maintained during the whole procedure except when hyperventilalion is induced for a tense cerebellum in the initial stage. We have used both lateral and prone patient positions, and although there is little difference between the two I have recently come to favor the lateral position. In keeping with our fundamental principle for all craniotomies the patient's head is kept above the level of the heart (Fig. 111-14). In the prone position the head is rotated more than 45 degrees to the affected side and fixed in the head frame. It is ihen returned to the straight position for the period from skin incision to dural opening because the anatomical orientation to the midline muscle layer and site

Fig. Ill-15

of craniectomy is more easily obtained it this way. When dissection around the aneurysm starts, the patient's head is again turned to the affected side to make the operative field perpendicular. When the aneurysm is difficult to clip Т suggest the surgeon change the position of the chair in relation to the patient's head so that he can more easily insert the clip with his dominant hand. Such a change of position at the time of clipping is recommended for every kind of aneurysm. 3. Skin incision and craniotomy: A lateral smooth S- or unilateral U-shaped skin incision is made (Fig. Ш-15В, C); in the case of a deep-seated or giant aneurysm the U-shaped incision is preferable because the skin and muscle in the lateral side of the operative field obstruct the view less (Fig. III-l 5 B). The lateral suboccipital craniectomy should be made far enough to visualize the sigmoid sinus and occasionally the transverse sinus; the lateral rim of the foramen magnum is removed. It is especially important that the bone edge close to the cisterna magna be extensively removed as when we deal with the sphenoidal edge in the frontotcmporal approach to an aneurysm in the anterior circulation. Removal of the atlas is not necessary except for rare aneurysms, such as one located in the far proximal segment of the vertebral artery: usually enough space for temporary clipping in the proximal vertebral artery is obtained without its removal. 4. Approach to the aneurysm: The aneurysm is located behind a bush-like group of lower cranial nerves which obstruct the approach at the beginning. Slow and gentle dissection of these nerves will enable the aneurysm to be approached without sacrificing any filaments. In the majority of cases one lower cranial nerve, usually the hypoglossal, is wedged in the

117 crotch formed by the posterior inferior cerebellar artery (PICA) and the vertebral artery. After freeing it from the crotch it is often useful to retract it directly with a 2 mm tapered retractor held by a self-retaining retractor. We have successfully preserved the cranial nerves in more than 95% of our cases. Retraction of the medulla with a tapered retractor is also an important procedure in the case of a deep seated aneurysm. Whenever this is done the surgeon must feel the resistance or hardness of the medulla through the retractor to obtain an appropriate force. I would stress the usefulness of a selfretaining retractor of light weight for this purpose. The retraction should never produce any change in vital signs such as respiration and ECG. We have not experienced any postoperative deficits considered to be caused by retraction of the medulla. 5. The dramatic effects of atropine should not be forgotten when any change in the cardiac and respiratory systems occurs on retraction of the medulla or vagus nerve, though the excessive retraction force should of course be reduced first. In some cases we have found no change in vital signs on retraction of the brain stem after preliminary atropine administration. Atropine is also effective for arrhythmia in the postoperative period.

6. Characteristics of the aneurysm: Fusiform aneurysms occur most frequently in the vertebral artery. Sometimes they can be successfully treated just by proximal clipping or ligation. The proximal parent artery must be obliterated close to the aneurysm to preserve the PICA and perforators. Although direct clipping of a true fusiform aneurysm is impossible a couple of cases of clipping of semifusiform aneurysms are illustrated in the following pages. 7. Clipping: Clipping techniques for aneurysms in this location are distinctive in some points. Because of the high incidence of fusiform aneurysms and the presence of numerous filaments of lower cranial nerves, bayonet, ultralong and ring clips are often used. It is important to remember when using such clips that they should not be placed flush with the parent artery, that the maximum opening width of an angled ring clip is less than that of a straight one (so that the latter is useful to reduce the size of a large aneurysm), and that the closing pressure of an angled ring clip is greater than that of regular clips, so such a clip should not be replaced many times. An ultralong clip is useful in some instances when the aneurysm lies at the bottom of a deep, narrow operating field where insertion of the clip holder is obstructed by the medulla, cranial nerves, or bony structures such as a prominent jugular tubercle.

118

Vertebral Artery Aneurysm

Case 47 Bayonet Clip for a Large Aneurysm (rt)

This 39-year-old woman had an SAH 3 weeks before the first operation. She had developed left hemiparesis three days after the attack, which worsened to hemiplegia on the tenth day. The CT scan showed a high density area around the right Sylvian fissure. Two aneurysms, one in the right middle cerebral and the other in the right vertebral artery, were found on the angiograms: the CT findings suggested that it was the one in the middle cerebral artery that had ruptured. The patient underwent the first operation for the middle cerebral artery aneurysm three weeks after the SAH. Though large, it was successfully clipped. After the operation the left motor weakness gradually improved. The second operation for the vertebral artery aneurysm was performed 6 weeks after the attack. Operation. With the patient in the lateral position a right lateral suboccipital craniectomy was performed. Hardly any clots or adhesions were encountered around the aneurysm, which was very large. It was semifusiform, without the usual constriction around the neck. The posterior inferior cerebellar artery (PICA) originated from the border between the parent artery and the aneurysm. Dissection of it from the aneurysm

wall was very difficult. Two fine perforators to the medulla branched off the proximal parent artery close to the aneurysm. The distal segment of the vertebral artery ran downward medially behind the aneurysm and the medulla, which was strongly compressed by the aneurysm. At first we considered using a straight clip, but putting it in place seemed likely j to cause stenosis of the parent and branching arteries or to leave a large residual portion. Thus a bayonet clip 12 mm long was positioned on the aneurysm so as to obliterate the proximal portion of the neck with the angled portion of the blades. The aneurysm was snugly obliterated. All arterial branches and filaments of the lower cranial nerves were perfectly preserved. The postoperative course was uneventful, j The left hemiparesis disappeared about two months later. Comments. It would have been very difficult to place a , straight clip on the best site while preserving the important I branching arteries. The angled portion of the shaft of the bayonet clip was just the right shape to obliterate the aneu rysm snugly, though this kind of clip is generally used to make it easier to keep the neck of the aneurysm and blades of the clip in view during application. j

119

i 1 Right proximal vertebral artery

2 Right disial vertebral artery 3 Right PICA

120

Vertebral Artery Aneurysm

Case 48 Clipping by Interchange of Two Clips (It)

This 62-year-old woman had a sudden onset of nausea, vomiting and vertigo 6 weeks before the operation. She became gradually worse, suffering disorientation and incontinence for 4 weeks. The initial CT scan revealed a large high density area of round shape in the left cerebellum. The subsequent CT taken a week before the operation showed a ring-shaped enhancement of the lesion like that of an abscess but the size of the high density had decreased and there was no perifo-cal low density. The angiogram showed an aneurysm at the left vertebral-PICA junction. Operation. With the patient in the prone position a left suboccipital craniectomy was performed with a left unilateral U-shaped skin incision. The lateral caudal bone edge was removed as far as possible. At first we intended to evacuate the suspected intracerebellar hematoma to make a space to approach the aneurysm. However, the wall of the hematoma was found to be just like that of an aneurysm, and its contents were organizing clots. We then realized that the ring-like enhancement on the CT scan was the organized portion of the aneurysm. Further removal of the intracapsular clot was abandoned, and after the patient's head had been rotated to the left about 45 degrees an approach to the neck of the aneurysm was started. The proximal vertebral artery was found to be small in diameter and sharply kinked at an angle of about 30 degrees. The artery distal to the kink was dilated to more than twice the diameter of the proximal artery. Additional retraction of the cerebellum made visible the base of the aneurysm, which originated from the kinked portion of the parent artery and projected medially into the border area

between the medulla and cerebellum. The IXth and Xth nerves were overriding and stretched strongly by the big body. The PICA was found branching off the corner made by the proximal parent artery and the aneurysm; it was adherent to the proximal vertebral artery. First a long straight clip of 24 mm was applied as far on the body side as possible. The first clipping was unsuccessful because of stenosis at the origin of the PICA and compression of the IXth and Xth nerves between the clip and the aneurysm. The same long clip was then repositioned between the nerves and the body, but the stenosis of the PICA was not completely relieved. Next, a bayonet clip with 13 mm blades was placed on the dome side parallel to the first, which was then removed. The results were beautiful as the PICA was not stenosed and the aneurysm was completely obliterated without injury to the nerves. At this point an unusual phenomenon was noticed: the wall of the base was thinner than that of the dilated parent artery, which appeared fusiform. The second clip was found to be completely closed, whereas the first one, on the parent artery side, had been slightly open. I was somewhat afraid of postoperative complications due to the repeated clipping, especially of the possibility of atheromas or emboli tearing off from the aneurysm. Evacuation of the clot and excision of the aneurysm were abandoned because there were few neurological deficits. The postoperative course was uneventful, and the neurological deficits disappeared gradually, but the postoperative angiogram showed that the vertebral artery distal to the clipping had been obliterated.

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1 Left proximal vertebral artery 2 Left, distal vertebral artery 3 Left PICA 4 Cranial nerves IX., X. 5 Cranial nerves VII, VIII 6 Clots in aneurysm dome

Comments. (1) The huge dome of the aneurysm was misdiagnosed as a hematoma preopcralively though this did not affect the approach. The method used in this case of gradually clipping inwards is one of the important techniques for dealing with a giant aneurysm. Л bayonet clip is often useful for this purpose; the angled portion of the clip is placed away from the first clip, which makes removal of the latter easier. To avoid difficulty in removing the first clip it is also possible to use a clip with blades longer ihan the first so that the heads of the two do not become entangled. (2) The cause of the obliteration of the parent artery is probably that the clip was placed on the neck. Although this is the correct procedure for an ordinary aneurysm. in the case of a giant aneurysm with a thick athcromatous wall the clip must be placed far from the parent artery and a residual neck must be left. (See case 11).

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Vertebral Artery Aneurysm

Case 49 Aneurysm Close to a Midline (rt)

This 62-year-old woman had a severe SAH 18 days before the operation. The vertebral angiogram showed two aneu-rysms at the left superior cerebellar and basilar arteries and at the most distal segment of the left vertebral artery in the midline. The vertebral artery aneurysm was suspected to be the one that had ruptured. Operation. With the patient in the prone position a left unilateral U-shaped skin incision and a lateral suboccipital craniectomy were performed to approach the vertebral artery aneurysm. The lateral side of the aneurysm was seen behind the IXth and Xth nerves. These and the cerebellum were retracted medially with a tapered retractor, but it was difficult to identify the distal sides of the aneurysm and parent artery, which were located almost beyond the midline, and direct retraction of the medulla was necessary. The most difficult procedure in this operation was to isolate a small artery and its perforator which were in close contact with the aneurysm body, covered with old clots; they obstructed the application of a clip. The small artery was isolated but the perforator adhered so strongly that it could not be separated without injury to the aneurysm wall, and sacrificing it was therefore

unavoidable. An ultralong clip of 21 mm was placed on the neck, at first a little too close to the parent artery as it seemed to be causing stenosis of the PICA, so it was shifted slightly to the dome side. Arterial oozing occurred immediately after clipping but was controlled with Oxycel packing under temporary hypotension for a few minutes; the bleeding point was unclear. The postoperative course was uneventful. A left frontotemporal approach to the basilar artery aneurysm was performed 3 weeks later, and clipping was performed without difficulty. Comments. An approach to this aneurysm was impossible without direct retraction of the medulla. An ultralong clip was also indispensable for such an aneurysm as this, located in a deep and narrow operating field close to the midline (the actual field was much narrower than shown in the color figure). A clip of usual blade length cannot be inserted here because the space surrounded by the cranial nerves, clivus, pons and cerebellum is far narrower than the width of the head of the clip applier, whereas an ultralong clip can be manipulated from outside the space without the surgeon's view being obstructed.

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1 Left proximal vertebral artery 2 Left distal vertebral artery 3 Left PICA

4 Direct retraction of the medulla

124

Vertebral Artery Aneurysm

Case 50 Aneurysm Close to a Midline (It)

This 56-year-old man suffered an SAH 2 weeks before the operation. Operation. With the patient in the prone position a left unilateral U-shaped skin incision was made. A relatively large craniectomy was made in the left lateral suboccipital area. After dural opening the patient's head was rotated to the left about 45 degrees. The aneurysm was located very deep, almost in the midline as the angiogram showed. The medulla was retracted medially with a tapered spatula; the retraction continued until clipping was completed. The origin of the PICA and part of the proximal side of the aneurysm neck were thus visualized. The whole of the body of the aneurysm was embedded in the medulla. The three perforators from the PICA to the medulla ran above the aneurysm and disturbed the approach to it. The most difficult part of the operation was the dissection of the PICA from the aneurysm neck and to obtain a space around the aneurysm for clipping because the PICA branched just above the neck and was acutely curved. The distal parent artery was behind the neck. First a bayonet clip with 13 mm blades was placed on the neck under lateral retraction of the PICA. The clip caused partial

stenosis of both the PICA and the distal segment of the parent artery. A second straight clip of 18mm was positioned on the dome side parallel to the first clip, which was then removed. The clipping was successful and all perforators and cranial nerves were preserved. The postoperative course was uneventful except for transient right hemiparesis which improved in four days. Comments. Isolation of the PICA and the clipping were very difficult in this case where the aneurysm was located in a deep, narrow operating field behind the cranial nerves and perforators. The direct retraction of the medulla with a tapered retractor was absolutely necessary. The retraction continued for about one hour without intermission because the operation was an early one of our series and took place before we began to employ intermittent retraction. Fortunately the postoperative hemiparesis was slight and transient. When double clipping in a parallel fashion is anticipated, a bayonet clip should be selected for the first trial, especially in a deep and narrow operating field, because the bayonet shape of the first clip creates a space between the spring portions of the first and second clips, whereby a better view can be obtained and the clip applier can be more easily inserted.

1 Left proximal vertebral artery 2 Left distal vertebral artery 3 Left PICA

126

Vertebral Artery Aneurysm

Case 51 Body Clipping (rt)

This 36-year-old woman had two mild SAHs one month before the operation. Although the patient was congenitally weak with a variety of physical problems, she had recovered fully from the SAH by the time of the operation. Operation. In the prone position a right lateral suboccipi-tal craniectomy was made with a unilateral U-shaped skin incision. A semifusiform aneurysm was soon found behind the IXth, Xth and Xllth cranial nerves. Many vasa vasorum were seen on the medial side of the aneurysm, which indicated, the site of the parent artery; this had been partly suspected from the angiogram. The body of the aneurysm had a smooth gray wall without vasa vasorum. The medial side was carefully dissected from the medulla with lateral retraction of the aneurysm, and the proximal side of the left vertebral artery was found in the depth between the two. Medial retraction of the aneurysm enabled us to identify the distal segments of the right and left vertebral arteries in the lateral side of the aneurysm. A straight clip, 18 mm in length, was placed on the neck under one bundle of the Xllth nerve as parallel to the parent artery as possible, but seemed to be located too deep and was stenosing the parent artery slightly. Next a bayonet clip with a 12 mm blade (No. 14) was placed on the dome side parallel to the first clip, which was then withdrawn. A small purple spot was found on the wall of the proximal vertebral artery; it was wrapped with a piece of muscle. Postoperative course: uneventful. The postoperative angiogram showed a relatively large residual portion.

Comments. (1) A large residual neck was seen on the postoperative angiogram but it had been caused intentionally by positioning the blade on the dome side to avoid stenosis of the parent artery. (2) The approach to the aneurysm was easy in this case because it was located laterally. The difficulty of vertebral artery aneurysm surgery depends largely on the distance from the midline on the anteroposterior view of the angiogram. The height of the aneurysm from the base of the skull is also important. The closer to the midline and the higher from the base an aneurysm is located, the more difficult will the procedure be. However, the angiogram gives only a general idea of the degree of technical difficulty; the operative space defined by the size of the cistern, the angle of the pyramid and the prominence of the jugular tubercle is very important, and as these anatomical features differ considerably from case to case the actual difficulty cannot be known until one looks into the surgical field.

127

1 Right proximal vertebral artery

2 Right distal vertebral artery 3 Left proximal vertebral artery 4 Left distal vertebral artery 5 Right PICA

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128

Vertebral Artery Aneurysm

Case 52 Body Clipping (Dissecting?) (rt)

This 41-year-old man had an SAH 10 days before the operation. He developed right abducens palsy and right hemiparesis. The neurological deficits had improved by the time of operation. Operation. With the patient in the lateral position, a right lateral smooth S-shaped skin incision and lateral suboccipital craniectomy were made. The aneurysm, which was fusiform, was soon found behind cranial nerves IX, X, XI and XII. To identify the neck the medulla had to be retracted medially with a tapered retractor far enough to visualize the origin of the nerves on the medulla. Half of the aneurysm was located behind the anterior surface of the medulla. Three small arteries were found around the aneurysm instead of one large PICA. The lower cranial nerves formed an intricate network over the aneurysm; it was impossible to obtain enough space to insert an ordinary clip by retracting them as they were already stretched by the retraction of the medulla. A straight ring clip, No. 30 (9 mm blade), was placed on the body of the aneurysm, preserving one filament of the Xth nerve through the ring. The blade tip at first partially obliterated the distal vertebral artery, and the clip was therefore rotated so that the tip moved to the dome side. About a half of

the aneurysm was obliterated. A relatively large portion of the base was intentionally left. All the cranial nerves were preserved. A small violet (rather than dark red) spot was found on the lateral surface of the aneurysm near its junction with the proximal parent artery, suggesting dissection beneath the surface. The area was covered with a piece of muscle. Postoperative course: The postoperative angiogram showed a residual neck which had been anticipated from the operative procedure (B). Hypoglossal palsy appeared transiently. The patient recovered fully and returned to his job two months later. A year later, however, he developed dizziness and vertigo. The vertebral angiogram showed complete obliteration of the left vertebral artery, which was suspected to be the cause of the symptoms, and enlargement of the residual portion of the aneurysm of the right vertebral artery (C). It was assumed that the violet spot observed during the operation had bulged but not ruptured. We are planning either a direct approach to the aneurysm again or bypass surgery followed by proximal ligation in the future. We hesitate, however, to carry out either procedure because the contralateral vertebral artery is occluded and the residual portion has not bled.

129

1 Righi proximal 2 Right distal vertebral artery 5 Purple spot suspected dissecting

Comments. The ring clip is occasionally very useful to preserve not only the artery but also a cranial nerve running over the aneurysm. This kind of application of ring clips is encountered more often in aneurysms of the vertebral artery than in other arteries. In the present case the residual portion of he aneurysm should have been completely wrapped, especially as a spot suggestive of dissection was found. Bemsheets and fibrin glue would perhaps have best served the purpose

vertebral artery

130

Vertebral Artery Aneurysm

Case 53 Semifusiform Pointing Toward the Approach (It)

This 41-year-old man had a mild SAH 12 days before the operation, at which time he had hardly any neurological deficits. Operation. With the patient in the half lateral position a left lateral suboccipital craniectomy was made. The IXth and Xth cranial nerves were running over the aneurysm, which was semifusiform with a thin reddish wall. The dome pointed toward the approach. The PICA branched off the parent artery distally to the aneurysm and at a considerable distance from it. Two small arteries feeding the medulla were found close to the aneurysm. The parent artery and the neck were clearly visible on careful retraction of the aneurysm. A J-shaped clip, No. 24 (7.5 mm curved blade), was put in place under temporary hypotension of 75 mm Hg for 5 min. It appeared to be positioned on the best site though a very small portion of the reddish wall remained outside the clip. Muscle

was wrapped around the parent artery. The postoperative course was uneventful. 1 Comments. From the point of view of surgical technique we classify fusiform aneurysms into 4 types: Type 1 is semifu siform with the dome pointing toward the approach; Type 2 is semifusiform with the body protruding laterally (see Case 51 & 52); Type 3 is semifusiform with the body behind the parent artery (see Case 55); Type 4 is true fusiform. A Jor L-shaped clip is the most suitable for Type 1 aneurysms. which are similar to distal anterior cerebral artery aneurysms in that the latter too usually project toward the approach. In the case of a fusiform aneurysm in the vertebral artery it is permissible to place a clip close to the the parent artery when the circulation in the contralateral vertebral artery is adequate because neurological deficits will usually not appear even if the parent artery is somewhat stenosed.

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1 Left proximal vertebral artery 2 Left distal vertebral artery

продолжение

132

Vertebral Artery Aneurysm

Case 54 Ring Clip for Preservation of a Perforator (It)

Case 1

Case 54-1: This 62-year-old man had an SAH two weeks before surgery. At the time of operation no neurological deficits were observed. Operation. With the patient in the lateral position a left lateral suboccipital craniectomy was made. As the head had not been positioned high enough strong venous bleeding was encountered during craniectomy and the cerebellum was bulging in the initial stage. As the angiogram had shown, the aneurysm was located near the midline, which made the approach very difficult. The left PICA was found branching

off the proximal side of the aneurysm and running just above it. One bundle of the Xllth nerve was wedged at the origin of the PICA. Medial retraction of the medulla with a tapered spatula enabled the proximal vertebral artery to be identified. It was sharply kinked behind the aneurysm, as had been suspected from the angiogram. No attempt was made to isolate and mobilize the aneurysm because the thin reddish dome was strongly adherent to the bone, and in addition a branch of the PICA adhered tightly to this reddish area. Isolation of the branch was attempted but it seemed likely to cause

133

1 Left proximal vertebral artery 2 Left distal vertebral artery 3 Left PICA

rupture. The PICA was medially rctraclcd together with the medulla to obtain a space for clipping. An oblique-angled ring clip, No. 34 (10mm blade, 3.5mm ring), was placed slightly to the dome side to avoid stenosis of the parent artery and PICA as well as to preserve the branching artery through the ring. The postoperative course was uneventful. Comments. (1) An ordinary clip could have been applied had the branching artery been isolated from the dome. As it was, applying a ring clip seemed to be an easier and safer way to preserve the artery and avoid the danger of bleeding from the aneurysm during dissection. It is worth remembering that dangerous dissection around an aneurysm can often be avoided by using a ring clip: this is one of the most useful features of this clip. Others include, as already mentioned. His use to reconstruct a parent artery and, because of the length of the ring portion, to serve as an ultralong L-shaped clip. 2) Although the aneurysm does not appear to have been obliterated on the postoperative angiogram, the aneurysm-like contour is the kinked portion of the vertebral artery behind which the aneurysm was located. In the territory of the vcrtcbral artery we occasionally find such a ghost aneurysm on the angiogram (see the angiograms of Case 54-2; typical ghost aneurysm): most of the time the illusion is caused by kinking of the parent artery (A, B). If there is any doubt, an axial view of the angiogram should be taken to differentiate it from a real aneurysm (C).

134

Vertebral Artery Aneurysm

Case 55 Large Fusiform Aneurysm with Three Ring Clips (It)

This 48-year-old man complained of left facial spasm. Angiography revealed an unruptured aneurysm at the left vertebroPICA junction. Operation. The patient was operated on in the prone position via a left lateral suboccipital craniectomy. Although the preoperative angiograms had suggested that clipping of the aneurysm neck would be possible, at surgery a fusiform aneurysm was found. The first clip was applied to the distal portion of the aneurysm to construct a new parent artery (A); it was a straight ring clip (No. 30, 9 mm blade and 5 mm ring). The second clip, which was a right-angled ring clip (No. 42, 7.5 mm blade and 5 mm ring), was placed on the portion of the aneurysm that appeared to form the neck on the preoperative angiograms (B). During application of the second clip the glossopharyngeal and vagus nerves were spared by slipping an L-shaped blade under them. The remaining proximal portion of the body was obliterated with an oblique-angled ring clip (No. 35, 5 mm blade and 5 mm ring) (C). This third clip, its blades pointing proximally, was placed so as to over-

ride the blades of the second clip. After clipping, Gelfoam was placed between the facial-acoustic nerve complex and the anterior inferior cerebellar artery. Postoperatively, the hemifacial spasm disappeared and there were no complications except for transient hearing difficulty on the left side. Comments. In order to construct a parent artery 5 mm in diameter from a large fusiform aneurysm 20 mm in diameter, an opening width of about 14 mm between the blades of an angled ring clip is required (D). Since the maximum opening distance of the largest angled ring clip is only 8 mm (E), to form such a parent artery is impossible. Our recommended method is, therefore, that a straight ring clip is first applied to reduce the size of the aneurysm (F) and then one or two angled ring clips are used to completely close its neck. When the first straight ring clip is applied off-center of the aneurysm an angled ring clip can be placed without crossing the first clip; if the blades of the second clip are too long they can be shortened in the way explained in Case 32.

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1 Left proximal vertebral artery 2 Left distal vertebral artery 3 Left PICA

IV Arteriovenous Malformation General Considerations

The operation for an arteriovenous malformation (AVM) other than a small superficial one is one of the most difficult neurosurgical procedures. The technical difficulty depends on the size and location of the lesion. The larger the AVM is, the more difficult is the operation. Even when it is small, great care is needed when it is deeply located, especially if it is close to a critical area. 1. Angiography. The most important preoperative procedure is to obtain a clear three-dimensional impression of the AVM. The operation should not be undertaken without an exact knowledge of the feeders, especially when the lesion is large. When the nidus has multiple feeders and these are hidden by the nidus itself, it is often very useful to prepare a preoperative three-dimensional sketch of them. It is important to know also the number and location of the drainers, especially as some of them may interfere with the approach to the nidus. 2. Anesthesia. Under general anesthesia, intra-arterial pressure and arterial blood gases should be monitored more carefully than in other operations. We presently use induced hypotension of about 65 to 75 mm Hg with sodium nitroprusside only for a short period of about 10 min when necessary. Transient hypotension helps to control bleeding and it seems to be safer than to apply it continuously. We have had cause to use it, however, in less than 20% of cases. 3. Patient's Position. Maintaining an ideal position is a very important tactic. In order to reduce the venous pressure the patient's head should be elevated as high as possible and venous return in the neck should not be disturbed by head flexion; usually the top plate of the operating table is kept tilted about 30 degrees. The most troublesome bleeding occurs not from arteries but from the red veins. Even though the direct supply from the arterial flow through the shunt causes an increased pressure in these, elevating the patient's head reduces the overall venous pressure considerably and makes the operation much easier. Another important point concerning patient position is that the operating field should be maintained in such a way that the microscope is positioned perpenTable IV-1. Surgical results of AVM

dicularly to it; to have to observe the field obliquely is too tiring for the surgeon in a long operation like that for a large AVM. 4. Approach to the Nidus. The selection of the approach is a matter of great importance with a deep-seated AVM or an AVM close to critical structures. In such cases brain retraction is another important problem because the volume of an AVM can be reduced very little throughout the procedure in marked contrast to brain tumors in general. When trying to approach a small subcortical AVM, a direct hit on its sub-cortical location cannot often be expected. Discrimination of its feeder on the cortical surface from normal arteries is usually impossible because it has the same diameter as that of a normal artery. It is recommended in such cases that a draining vein is traced backwards from the cortex; a drainer is red and large even in a small AVM. Orientation to a large AVM, on the other hand, is easy even in a deep subcortical region because there are many large feeders and drainers. Care must be taken, however, when a cortical incision is to be made, especially with a large AVM close to a critical area such as the motor or speech cortex. A larger incision is generally made than for a small AVM because a large open field and considerable retraction are often necessary. 5. Procedure around the Nidus. It is a well-known principle of the AVM operation that all feeders are obliterated before the main drainer is sacrificed. Generally, coagulation of a feeding artery is easier than that of a draining vein because its wall is thick. The further the vessel is from the nidus, , the stronger is its wall, so when bleeding is difficult to control the vessel should be followed some distance from the nidus. When cutting a large drainer temporary clipping should be attempted first. The drainer can then be cut after checking that no swelling of the nidus occurs. Almost all feeders and drainers can be coagulated and cut without using hemoclips, and only large feeders need be ligated or clipped to prevent postoperative bleeding. In the case of a giant AVM coagulation of a large feeder is occasionally impossible without ligation because the maximally dilated wall is too thin. When bipolar coagulation is not effective, bleeding from the nidus is controlled by covering the area with Oxycel

137

and cotton, which are pressed against the nidus with a tapered retractor (Fig. V-1). The utmost care should be taken with red veins, especially when they are behind the nidus deep in the operating field where (he control of bleeding is extremely difficult; it usually occurs at the final stage of the procedure when the remaining vessels, both arteries and veins, are often under high pressure. For this situation we should keep in mind the following points: (1) Bipolar forceps with tips of a metal that has high heat conductance should be used because tissue adherence by coagulation isjess^with such a metal. For-ceps made of titanium arc not used. The forceps should be insulated except for the tips. A weaker current should be used than when coagulating an ancurysm wall. Coagulation with wider forceps should be done with a different current from with narrower ones because the former has low impedance. The output current should be changed frequently. We use a small sterilized output controller inside the operating field which is controlled by an assistant surgeon. This system is especially useful in AVM surgery. (2) Transient hypotension, induced for several minutes at about 70 mm Hg systolic, is often useful to control bleeding and to coagulate the thin wall of vessels. (3) When we encounter a very fragile red vessel which is difficult to coagulate, we should expose the vessel far from the nidus in the normal structure; the farther a red vessel is from the nidus, the stronger is its wall. As such a vessel is often located on the perpendicular wall in the operating field, the microscope should be tilted so as to see it directly with retraction of both the nidus and contralateral cortex (sec Fig. TV-1). (4) Although bleeding from the nidus can usually be conlrolled with Oxycel covering, the bleeding from the normal side should never be controlled only with Oxycel except for very small vessels in a small AVM, but instead the bleeding point should be coagulated completely. When the AVM is located close lo critical areas such as the motor cortex, basal ganglia or brain stem, dissection should be done right on the coils of the lesion, so as to remove only the nidus and cause the least possible damage to the surrounding

Fig.IV-1

tissues. In such situations the connection to a small daughter nidus may be cut accidentally. 6. Classification of Residual Daughter Nidm. I classify a small residual daughter nidus connected to the main one by a band containing both feeders and drainers into three types as illustrated in Fig. TV-2. The residual portion of Type A has only a drainer; it disappears postoperatively. Type В has both feeder and drainer; it is found as a residual AVM cm the postoperative angiogram. Type С has only feeders and it is the most dangerous: if left, severe bleeding is bound to occur either intra- or postoperatively (see Case 74). Although it is possible to remove type В by a second operation, we must never leave a type С nidus. Such a nidus is most likly to be missed when a large AVM is dissected close to its coils in a critical area. Determination of the nature of a nidus should be done cautiously, by, for instance, careful temporary clipping of short duration. When bleeding occurs from a type С nidus intraoperatively. it should be competely controlled even if this involves entering important normal brain. Any conciliatory treatment of the nidus will likely lead to intraop-erative uncontrollable bleeding or postoperative massive hemorrhage, although the nidus may spontaneously thrombose in a rare instance when it is very small. 7. Giant A VM. The character of an AVM varies according to its size. Special tactics are required for a giant larger than 5 cm in diameter. Difficulty may be expected when the preoperative angiogram demonslrates numerous dilated vessels oo the normal cortex surrounding the AVM. and when, at surgery, many red vessels are located widely around the nidus. In such cases the breakthrough phenomenon may develop postoperatively (see cases 63 and 64). Such an AVM ordinarily has a high shunt flow, which causes luxury perfusion e*ca after obliteration of most or all of the feeders. A two-Step operation is one way to pre\ent a breakthrough, which, wbe» it has occurred, is best treated by induced continuous hypotension, occasionally combined with Barbiturate therapy.

1 Temporal Lobe AVM Case 56 Anterior Portion (It)

This 58-year-old man had suffered from seizures for more than 10 years. He had no history of SAH. Operation. With the patient in the supine position the head was elevated above the heart level and rotated considerably to the right with a roll placed under the left shoulder. A left frontotemporal craniotomy was performed. First the left proximal middle cerebral artery was approached to identify the largest feeder, the temporal polar artery, which was temporarily clipped with a small Sugita clip. All of the Sylvian veins were reddish due to arteriovenous shunt. A group of more than 15 small dilated reddish vessels was found on the surface of the temporal lobe around the lateral side of the Sylvian fissure about 3 or 4 cm behind the temporal tip. The nidus was located subcortically in the frontal side of these pathological vessels. The approach to the nidus was begun by coagulating and cutting them and then making a corticotomy of about 3 cm. In the medial side close to the cortical incision a couple of large draining veins were found; they were not touched until isolation of the whole nidus was complete. Dissection and coagulation of the surface of the nidus were done in the following order: anterior, lateral, posterior and medial sides. In the bottom of the operative field and under the nidus were found the largest feeder and drainer. When about 90% of

the nidus had been isolated, a temporary clip was placed on the drainers to the Sylvian veins in order to check if there were any significant feeders left. The clipping did not cause the nidus to swell and it was therefore simply removed. Finally, the entire course of the temporal polar artery was exposed from its origin at Ml to where the nidus had been; this enabled us to find a small residual nidus in the anterior area near the main one. The operating time from dural opening to closure was 2 h and blood-loss was less than 100 ml. The postoperative course was uneventful. No visual field defects were observed and the frequency of the seizures decreased with the medication he had been receiving preoperatively. Comments. (1) This AVM may be classified as belonging to the easy group: it was small, located in a silent area and was not deep-seated. (2) The picture is intended to show the whole nidus and its anatomical relation to the neighboring brain; the cortical incision appears much larger than its actual size of 3 cm. The simultaneous retraction of the cortex with three spatulas is also an exaggeration: it was done with only one at a time while the other retractors were loosened. The actual dissecting field was very narrow and frequently the nidus itself, the surface of which was coagulated, was directly retracted with a tapered spatula. (3) The preoperative angio-

139

1 Left temporal lobe 2 Sylvian vein

gram of this case suggested that the nidus might not be solitar.". Searching for the remaining nidus by dissection along the largest feeder proved very useful.

140

Temporal Lobe AVM

Case 57 Anterior Portion with Aneurysm (It)

This 64-year-old man experienced a severe intracerebral hemorrhage. Serious mental deterioration, right hemiplegia and aphasia appeared. Next day evacuation of the clots in the left temporal lobe was performed without any direct attack on the AVM. The patient improved remarkably, but mild aphasia persisted. He underwent surgery for removal of the AVM 5 weeks after the hemorrhage. Operation. The approach to the AVM was carried out through the craniotomy made in the previous operation. First an aneurysm at the bifurcation of the left middle cerebral artery was approached. It was unruptured and had a very thin, transparent wall. Clipping was successful. Around the aneurysm were found huge dilated veins, whereas all of the Sylvian veins were small and normal in color. The Sylvian fissure was still bulging even though the clots in the temporal lobe had been evacuated at the previous operation. The fissure was opened deep and wide, and three main branches of the distal middle cerebral artery were found there. Numerous feeders branched off these arteries and all were coagulated and cut close to the nidus; discrimination of the feeding arteries from normal ones was difficult. The medial side of the nidus was dissected. Two huge connected drainers were located superficially in the lateral side; the posterior one seemed to go to the vein of Labbe and the anterior one toward the sphenoidal ridge. Without cutting one of them it would have been impossible to dissect the ventrolateral portion of the

nidus. The posterior drainer, which was smaller than the anterior one, was temporarily clipped, and as the nidus did not swell significantly it was coagulated and cut. Dissection of the posterolateral portion now became easy because the nidus was mobile and so could be retracted. However, the isolation of its anteromedial portion under the huge knee of the remaining dilated drainer was a problem, as the latter was still so expanded that it obstructed an approach to the underlying nidus. In addition the stretched Sylvian veins were in the way of retraction of the temporal tip. When the anteromedial portion had been successfully isolated from just a few small feeders, however, the drainer slackened dramatically. After confirming with an ordinary clip that the nidus did not bulge the drainer was cut off from the nidus and the latter removed. The clip was left on the drainer. The inferior horn of the ventricle was opened beneath were the nidus had been. The time from dural opening to closure was 5 h with 200 ml blood-loss. Postoperative course: The preoperative neurological deficits improved. Only a slight speech disturbance remained one month later. Comments. (1) I hesitated to make a direct approach to the AVM immediately after the severe hemorrhage because the patient's condition was too poor and in general rebleeding from an AVM is far less frequent than from an aneurysm. But the removal of clots has to be done as soon as possible in the acute stage when the patient's condition is poor. It

141

I Draining Vein

is our general principle that the AVM is operated on in a chronic stage. (2) Two procedures were the most lime-consummig: one was the dissection of the numerous feeders from ibe middle cerebral arteries to the nidus which were seen on the angiogram. The other was the isolation of the nidus from thc few remaining feeders and drainers under the huge drainer It ihe temporal tip, where the space was very narrow. (3) It was fortunate in this ease that a space around the nidus was easily obtained, except in the anteromcdial portion, due to bematoma and that the nidus was not located around the middle cerebral arteries but confined to the temporal lobe. *-•* It is surprising how much blood is carried into the nidus ~< ча few small remaining feeders, ihe sectioning of which marketly slackens the size of the drainer.

142

Temporal Lobe AVM

Case 58 Posterior Portion (It)

J

This 37-year-old man had a mild SAH 18 days before the operation. Right homonymous hemianopia remained at the time of surgery. Operation. With the patient in the lateral position the head was elevated above the level of the heart and turned toward the right shoulder as far as possible. A left middle subtemporal approach was made. On the anteromedial side of the incisura tentorii the trochlear nerve and large posterior cerebral artery were found; the latter was twice the normal size and had four branches. As it was difficult to decide which of the four branches were feeders, a temporary clip was placed on the three which seemed most likely. The AVM was not seen on the undersurface of the temporal lobe, where only a few small red veins were found. Because the top of the operating table was elevated it was difficult to visualize the most medial portion of the lobe unless the surgeon took an uncomfortable position as if he were looking at his own stomach, so the head was therefore lowered slightly and the most medial portion of the lobe then removed as shown in the bottom color figure, hatched area. The AVM was now clearly visible with minimum temporal retraction. The nidus became very tense when the clip on the suspected feeders was released. After they had been followed close to the nidus they were coagulated and divided. Their obliteration made dissection of the upper half of the nidus easy. When dissection of the ventromedial side was to start I moved from the vertex of the patient's head to the occipital side. This made it possible to see into the depth of the subtemporal area with less retraction of the temporal lobe, though I had to tilt my head to the left. A

large drainer was found in the ventromedial side of the nidus, draining into the straight sinus. The bottom of the nidus extended to the trigone of the ventricle, where it was adherent to the choroid plexus and where a few feeders and drainers were found. They were obliterated. Finally, the largest main drainer in the ventromedial side of the nidus was coagulated and divided after testing the volume change of the nidus with temporary clipping. The time from skin to skin was 5 h, with a blood-loss of 500 ml. The postoperative course was uneventful. The visual field defects improved to quadrantanopia. Comment. •(!) Special care about the patient's position should be taken in the subtemporal approach, especially when dealing with a lesion in the deep medial subtemporal area. The position exerts a great influence upon all kinds of surgical procedures due to such factors as intracranial pressure, venous pressure, temporal lobe retraction and the physical fatigue of the surgeon. It is often recommendable that the surgeon sit on the occipital side of the patient during procedures in the deep medial subtemporal area. Although he has to tilt his head, the temporal retraction required is not excessive and the patient's head can be kept high. (2) Application of a temporary clip to suspected feeders is useful in the initial stage because it is difficult to distinguish the feeding arteries in the narrow operating field. Temporary clipping of a big drainer prior to obliteration is always essential to avoid a possible catastrophe. (3) Removal of the smallest possible amount of temporal lobe is often better than excessive temporal lobe retraction, which would result in more edema or hemorrhage than does removal.

143

Hatched area removed 1 Left distal posterior cerebral artery 2 Main draining vein

2 Central Area AVM Case 59 Precentral: Small Residual (rt)

This 13-year-old boy had suffered seizures for 3 years. Three weeks before the operation he had a hemorrhagic attack, following which left hemiparesis appeared, but it was gradually improving. Operation. A right frontotemporal craniotomy was made. On the cortical surface of the medial side of the Sylvian fissure two small red veins were found but the nidus was located subcortically. A 3 cm cortical incision was made slightly frontal to the cortex over the nidus, which was suspected from the angiogram to be located close to the motor area. The brain was retracted more in the frontal direction than in the posterior to lessen any damage to the motor cortex. At first it was very difficult to distinguish the normal from feeding arteries among those which were running over the nidus, as some of them were suspected to be feeding the motor cortex. Dissection of the nidus was not difficult. At the bottom of it a big drainer was found. A daughter nidus was found in the frontal side of the main one. Immediately after we thought we had isolated the daughter the frontal lobe started to bulge. A quick check in the frontal side of the daughter nidus re-

vealed a large hematoma cavity containing a mixture of fresh and old clots; the cavity had formed at the previous hemorrhage three weeks earlier. The bleeding point was soon controlled, and the swelling of the frontal lobe subsided. The dissection was continued. Although a small portion of the nidus was still suspected to remain in the depth, total removal was abandoned for fear of injury to the pyramidal tract. The large drainer was ligated and divided, and a Week's hemostat clip placed on the cut end. Operation time was 6 h with 400 nil blood-loss. The postoperative course was uneventful. The postoperative angiogram showed a small residual portion in the depth which was supplied by the anterior choroidal artery. We planned to remove the residual portion at a later date. Comments. (1) One worries much about postoperative deficits when dealing with an AVM located close to or inside the motor cortex. In our limited experience, however, the probability of additional postoperative deficits is no different from that in other areas. One reason would be that we try to dissect the AVM as close to the nidus as possible with minimal retraction of the motor cortex; another would be

145

Dolled line: old hematoma

thai after resection of ihc AVM. the blood-flow to the motor cortex improved due to cessation of shunting. (2) Intraoperative brain swelling occurred in three of our 72 cases of AVM. In all of them the bleeding point was a small residual nidus of type C. where there was connection only with the feeder as illustrated in the general considerations. Such swelling becomes severe when the blood flows into the ventricle or a hematoma cavity. We should immediately control the bleeding when it occurs, as in the case of intraoperative rupture of aneurysm. Temporary hypotension helps very much in this situation.

146

Central Area AVM

Case 60 Close to Broca Area (It)

This 51-year-old professional driver had a severe SAH 2 months before the operation. Immediately after the hemorrhage he developed right hemiplegia and global aphasia. At the time of operation slight hemiparesis and mild motor aphasia remained. Operation. A relatively small left craniotomy was made above the lesion. One red vein was found on the surface of the pars opercularis of the inferior frontal gyms in the anterior side of the precentral sulcus. Tracing the red vein from the surface to the depth led us to a small subcortical nidus, which was easily isolated because it was surrounded by old clots and gliosis. The ventricle was opened in the bottom of the operating field. Three main feeders were identified in the location suspected from the angiogram. The color of the only drainer of the AVM changed from red to normal blue when a temporary clip was placed on the neck containing the drainer and two small feeders. This neck was ligated, coagulated and cut. Time from dural opening to closure was less than one

hour with almost no blood-loss. Postoperative course: Except for one seizure the first evening the patient recovered fully without additional deficits. In the follow-up study three months later he showed no motor weakness but a very slight speech difficulty. Comment. (1) I was reluctant at first to operate on this case because 3 months had already passed since the hemorrhage and the lesion was very close to the Broca area. The operation was, however, so easy that all procedures were completed without the need to touch or retract the Broca and motor cortices, owing to the small size of the nidus and the space produced by suctioning the old hematoma. (2) One of our residents had prepared a three-dimensional sketch of the vessels around the lesion, and at surgery all feeders and drainers were encountered exactly as in the drawing. This was a great help, though the surgeon should of course make such sketches himself.

147

1 Вгосa area, suspected

2 Left temporal lobe 3 Left sylvian vein

148

Central Area AVM

Case 61 Under Broca Area (It) (Parasylvian Fissure)

This 26-year-old woman underwent a craniotomy 4 months before the 1st operation in the 8th month of pregnancy. At that time the AVM was misdiagnosed as a glioma because no angiogram was done due to the on-going pregnancy. She delivered a healthy baby by Cesarean section. 1st Operation. In the supine position the patient's left shoulder was elevated and the head rotated until the right side of it was parallel to the floor. A small parietal craniotomy was added to the previous frontal craniotomy. On the cortical surface hardly any pathological findings were observed except for a couple of small red veins. Orientation of the nidus was difficult. First an approach to it was tried along one of the red veins by dissecting the anterior ascending ramus (or anterior horizontal ramus), one of the lateral Sylvian sulci. The attempt was unsuccessful. The Sylvian fissure was then opened wide, whereby one large feeding artery was found. A small nidus was identified in the distal portion of the artery, overriding a big dilated drainer. In the posteromedial side of the nidus a big cyst containing yellowish fluid was opened during dissection. In the depth between the cyst and the drainer a giant varix with a hard wall could be seen. The vessels of the nidus were easily coagulated and divided. But at the final stage when the drainer was about to be cut, it was found by temporary clipping that at least one feeder remained somewhere behind the big drainer. Repeated clipping of various portions of the drainer and further dissection around it were not successful in locating the feeder. One area which could not be investigated was behind the cortex of Broca where

a few drainers were located. Further isolation of these vessels was abandoned for fear of postoperative aphasia as the retraction of the Broca area was already maximal. A second operation was planned after the postoperative angiography. The main procedure took 4 h. Blood-loss: less than 100ml. The patient awoke from anesthesia without neurological deficits. The huge drainer and varix disappeared from the angiogram. 2nd Operation. Three weeks after the first operation. The patient's head was positioned with much care for the approach to the intrasylvian fissure. The position was better than in the previous operation but the skin and muscle layers still disturbed the approach when this was tried from the side of the patient's face. The brain was very slack, a big difference from the previous operation; this was due probably to the collapse of the dilated drainer and the varix with the previous operation. The slack brain facilitated isolation of the nidus from the most medial portion of the brain below the Broca area with minimal brain retraction. The most medial portion of the nidus (slightly anterior to the Week clip placed at the previous operation) had one feeder and four drainers of a usual size. All of these were coagulated and cut, which resulted in a remarkable collapse of the main drainer. The whole nidus was easily removed. From dura to dura: two hours. The postoperative course was uneventful without any deficits. Comments. (1) The approach to the AVM at the first operation was very difficult due to the incorrect position of the patient's head. The AVM itself was located in the depth of the medial side of the Sylvian fissure - the same situation

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149

1 Old hematoma cavity 2 Broca area suspected 3 Left temporal lobe

4 Blood flow meter

„

as in a subtemporal approach to a high-positioned basilar' artery aneurysm. The lateral position, with the surgeon sitting in front of the patient's face, would have been better. In this approach the skin flap is retracted far laterally, and although the bulk of the temporal muscle gets in the way the problem can be solved by cutting the anterior h alf of the muscle and reflecting it posteriorly (lower: arrow A). (2) The second operation was very easy due to the slack brain, which facilitated visualization of the most medial portion of the nidus just under the Broca area, where the final residual feeder was located: the required brain retraction was minimal. The two-stage operation was very successful. If radical removal with excessive brain retraction had been tried at the first operation major deficits such as severe aphasia would have ensued.

В

A Approach to the AVM in the medial side of the deep Sylvian fissure {Case 61) В Approach to superficial AVM (Case 60)

150

Central Area AVM

Case 62 Large AVM (It)

This 58-year-old man had undergone a craniotomy about 30 years earlier and severe right hemiparesis had continued ever since. He had a severe hemorrhage one month before the present operation, developing right hemiplegia following deep coma. The left external carotid artery was embolized before the operation. Operation. A left frontoparietal craniotomy was made. Care was taken to dissect the dura from the nidus and the large drainers. By the time the dura was opened about 1,200 ml of blood had been lost due to strong adhesion, even though the feeders from the external carotid had been embolized. The large AVM was found on the surface of the motor cortex. First the frontal side of the nidus was isolated and then the posterior side. The ventricle was opened under it, and several small feeders and drainers were found there. When almost the whole surface of the nidus had been isolated two large main drainers remained; the lateral one drained into the Sylvian veins and the medial one into the sagittal sinus, though in fact neither was a pure drainer but a complex of multiple drainers and feeders. The lateral complex was obliterated with an aneurysm clip, which, to our suprise, caused the nidus to bulge. Two clips were then positioned on the same area; the bulging stopped. It was suspected that one clip obliterated only a drainer due to insufficient pressure of

the clip. It was then ligated with a thick suture (see the color figure), resulting in a reduction in the size of the nidus by about a half, and was then coagulated and divided. After a few feeders and drainers under the nidus had been treated the main draining complex to the sagittal sinus was ligated. Although this produced neither slackening nor bulging of the nidus the complex was coagulated and cut, and the nidus then was removed without any problems. Blood-loss after dural opening was 200 ml. The time from skin incision to closure was 10 h. The postoperative course was uneventful. The hemiplegia preceding the operation showed a moderate improvement. Postoperative angiography was refused. Comment. (1) The operation was performed without the fear of causing additional deficits as the patient had hemiplegia and a severe hemorrhagic attack. If he had had fewer neurological deficits I would have spent much longer on the operation. (2) When only a clip is applied to a neck containing drainers and feeders its closing force is not strong enough to obliterate all the vessels simultaneously; it can close the drainers but not the feeders. Suture ligation is better but of course it will not serve for temporary test obliteration of a vessel. (3) The postoperative improvement was somewhat surprising, considering that the nidus was located in the motor cortex.

15!

1 Left sylvian vein

2 Superior sagittal sinus 3 Left lateral ventricle

152

Central Area AVM

Case 63 Large AVM: Breakthrough (rt)

lat This 46-year-old man had noticed sensory disturbance in the right (!) side of his body for 4 months before the operation. Operation. A right frontoparietal craniotomy was made. All of the Sylvian veins were reddish and were dilated to three times the normal diameter. Numerous angry dilated vessels were found over the cortex, especially on the frontal lobe. The AVM was not found on the surface but a large drainer was found in the medial side of the Sylvian fissure. The nidus was approached by following the drainer after making a 3 cm cortical incision. Dissection around the posterior (motor cortex) and lateral (Sylvian fissure) sides of the nidus and retraction of the nidus itself with a tapered retractor brought many feeding arteries into sight. Only a few vessels connecting with the nidus were found in the frontal and medial sides. The surface of the nidus was coagulated intensely. When about 95% of it had been isolated a temporary clip was placed on the main and biggest drainer entering the Sylvian veins. This caused oozing from the bottom of the nidus, which we therefore tried to isolate. There were still many drainers and feeders from the anterior cerebral artery which were tightly intermingled, and coagulating them was very difficult because the walls were very thin and the internal pressure high. This proce-

dure took an unexpectedly long time and about 700 ml of blood was lost." Finally, the biggest drainer was ligated, coagulated and divided. Time from skin incision to closure was 9 h and total blood-loss was 1,500 ml. Postoperative course: The patient developed mild disturbance of consciousness, and left hemiparesis which was more dominant in the upper extremity than in the lower. The deficits continued for about two weeks, and he complained of severe headache. During this period induced hypotension of less than 100 mg Hg was maintained. One month later all deficits disappeared. The postoperative CT scan and angiogram taken within a week of the operation showed the typical findings of luxury perfu-sion in the large area around the lesion that had been removed; high density was found in the cortex of the whole right hemipshere on the CT scan and the normal cortical arteries were found to be extremely dilated on the angiogram (B). The CT and angiogram taken one month later showed that these pathological findings had disappeared completely (C). Comments. This was the first case of our AVM series which showed a typical postoperative luxury perfusion. Probably the induced postoperative hypotension contributed to the patient's full recovery. (1) We must anticipate a high possi-

153

1 Right sylvian veins 2 Right frontal lobe 3 Right temporal lobe

bility of postoperative luxury perfusion when such a large number of pathological red vessels are found on the cortex; it can also be suspected from the preoperativc angiogram (see the X-ray picture A It AP CAG). Tt generally occurs in an AVM with a diameter of more than 5 cm. In such cases continuous hypotension should be started immediately after surgery, combined wilh Barbiturate therapy if the luxury perfusion is severe. (2) In large AVMs we have often encountered difficulty controlling the bleeding from the vessels in the final stage, when they seem to become more dilated. The larger the AVM. the more frequently is such difficulty encountered. Accordingly, the final siage is always the most important and ihe most difficult.

154

Central Area AVM

Case 64 Large AVM: Breakthrough (rt)

This 29-year-old man suffered several attacks of focal epileptic seizure. The last attack caused Todd's paresis of the lefl hand. Total hemiparesis of the left side occurred on compression of the right cervical carotid artery at the angiographic study. Il was strongly suspected that a high-flow shunt in the AVM caused a steal phenomenon. Operation. With the patient in the supine position the head was rotated about 90 degrees to the left and elevated about 45 degrees. This head position was ideal, as the lesion was visible wilh the microscope positioned perpendicularly and, in particular, low venous pressure could be maintained. The AVM of about 5 cm in diameter occupied mainly the postcen-tral gyms near the superior sagittal sinus. Us anterior portion did not extend beyond the precentral gyrus but pushed against it. The central sulcus was found between the the nidus and the shifted precentral gyrus. First, dissection of the central sulcus was tried between ihc arachnoid membranes of both sides but turned out to be impossible because the arachnoid w a s strongly adherent to the nidus, so the arachnoid over one side was dissected and reflected over the nidus and the

motor cortex was retracted without the arachnoid. The central sulcus was very deep. The frontal side of the nidus was coagulated over the arachnoid; it was done very quickly without even slight bleeding. Then the lateral and posterior sides of the nidus which were not covered with arachnoid were isolated. The superior sagittal sinus side had no feeders, just the biggest drainer. Several feeders and drainers were located under the nidus. Control of bleeding from these vessels was the only problem in this operation, as it always is at the final stage of removing a large AVM. Hemostasis was also necessary for some period after total removal. Time from dural opening to closure: 4 h 30 min. Total blood-loss was 300 ml. Postoperative course: On the first night the patient's consciousness was clear although severe hemiparesis was present. In the morning his consciousness gradually worsened accompanied by anisocoria. The CT scan showed a hernatoma in the area operated on and the right hemisphere shifted toward the left. The wound was reopened, and the hematoma immediately found and evacuated; no active bleeding point was identified in the lesion. After Barbiturate therapy for a period

3 Interhemispheric AVM Case 65 Anterior Portion (rt)

This 11-year-old boy had suffered frequent seizures for 5 years. Operation. With the patient in the supine position a right unilateral medial frontal craniotomy was made. The anterior medial frontal lobe had no bridging veins, and the lesion was easily approached. The bilateral distal anterior cerebral arteries were retracted to each side with two tapered retractors. Beneath these arteries was the medial anterior cerebral artery from which a main feeder branched. In the bottom of the

operating field a large red vein was found; its color changed remarkably to dark blue when the main feeder from the medial anterior cerebral artery was closed with forceps. The feeders, nidus and drainer were coagulated and divided. A small nidus around the right Heubner's artery was coagulated on its surface but intentionally left because its adhesion was too strong to isolate it without injury to it. The operation was finished within 2 h with minimum blood-loss. Postoperative course: The boy developed slight disorientation which improved after two weeks; it disappeared completely about two months later.

157

1 Chiasm

2 Left A1 3 Right A1

4 Draining vein

158

Interhemispheric AVM

Case 66 Anterior Portion (rt): Residual Nidus

This 54-year-old man had the curious experience of frequently running his car into objects at the left side of the road. He was aware of only a few spells of unconsciousness. No hemorrhagic attack was experienced. Operation. A right unilateral frontal craniotomy was made with the patient in the supine position. Special attention was paid to opening the midline close to the sagittal sinus. Two large red veins draining into the superior sagittal sinus were present in the posterior side of the operating field; they were preserved. First the origin of the anterior cerebral artery was approached; it was an azygos artery. All of the bilateral A1 s, anterior communicating and azygos arteries were twice the normal size. A relatively large right Heubner's artery was found branching from the proximal azygos artery. A large nidus was found under the bilateral distal anterior cerebral arteries. The main feeders seemed to originate only from the

right distal anterior cerebral artery branching from the azygos portion. After coagulating and dividing the feeders and other small vessels, I dissected the nidus. Its anterior portion was easily isolated but the posterior half extended deep into the interhemispheric fissure. Its right side reached the right ventricle, so the right anterior horn was opened. Finally, the biggest drainer, which probably drained into the basal vein, was ligated and cut. The bilateral anterior cerebral arteries were preserved. Six hours from skin incision to closure; 500ml blood-loss. Postoperative course: Resolving mild disorientation continued for a couple of weeks without other deficits. The postoperative angiogram revealed a small residual nidus in the deep interhemisphere. An immediate second operation was postponed due to the disorientation.

1Я

Comments. An interhemispherie AVM is one of the most difficult operations when it is large. Disorientation is often observed as a postoperative deficit; it is transient in most cases but persistent in some due to injury to the normal arteries feeding the corpus callosum and cingulate gyms. Imperfect checking of the bottom of the operating field is likely to leave a residual nidus; ihc checking itself is not difficult because there is usually a large space after removal of the main nidus. In this case, however. 1 did not further dissecl the deeper interhemispheric fissure for fear of causing additional deficits. Another retrospective consideration is that brain retraction would be less with a bilateral frontal cranioiomy than a unilateral one in a case with a laterally wide lesion, though this AVM was removed without much difficulu.

1 Left Ax 2 Right A, 3 Azygous A2

4 Right anterior horn of the ventricle

4 Intraventricular AVM General Considerations

Intraventricular AVM is one of the most dangerous vascular diseases, since hemorrhage from it often results in fatal intraventricular cast formation. Although many authors have reported interhemispheric or transtemporal approaches to the intraventricular AVM, I approach transcortically via the frontal or parietal lobe: transfrontally to an AVM in the anterior half of the ventricle (color figure on p. 161) and transparietally to one in its posterior half (color figure on p. 163). Even

in the left parietal lobe approach additional postoperative deficits have not been experienced. The most important technique in the transcortical approach is the retraction. We apply four tapered retractors circumferentially around the cortical incision. Each retractor is connected to a self-retaining retractor attached to the multipurpose head frame. The brain should never be retracted with more than two retractors simultaneously ; while one side of the brain is retracted the retractor on the contralateral side must be loosened. In this way a sufficient working space can be obtained in the ventricle through a cortical incision of less than 4 cm.

Case 67 Anterior Portion of the Ventricle (It)

I

This 12-year-old boy had had a severe intraventricular hemorrhage one month earlier. He recovered fully one week before the operation. Operation. A left frontal craniotomy was performed. A 3 cm corticotomy was made transversely on the frontal tip starting 2 cm from the midline. A ventricular tap was not done for fear of direct injury to the AVM with the tip of the needle. The left anterior horn was clearly visualized through the 3 cm corticotomy with the aid of tapered retractors. (Although four retractors are shown in use simultaneously in the left upper color figure only two were actually used at a time and the cortical opening was far smaller.) On the anterolateral side of the anterior horn a small portion of the AVM and the previous bleeding point with old clots were

identified. Dissection around the nidus was effected step by step. It was isolated from the lateral wall of the ventricle. In the posterolateral side some grey matter was encountered; it was suspected to be the caudate nucleus. Finally, one big feeder was found under the nidus; this was simply coagulated and divided, which meant that the nidus could be removed. Time from dural opening to closure was one hour; hardly any blood-loss. The postoperative course was uneventful. The CT scan and angiogram showed no residual nidus or low density around the approach. Comments. The surgical procedure was accomplished without any trouble even through a small cortical incision. If the AVM had been larger a slightly longer incision would have been necessary. The approach was made perpendicular

161

~" ~ \

ю the nudlinc and relatively close the sagittal sinus as shown io the lower figures (A). Perhaps the corticotomv should have been made more posterolaterally as shown in the lower figures (B). as in our other cases; the distance from point В to the ventricle is certainly shorter than that from A. The disadvantage of the В approach is. however, the possibility that the AVM might be encountered before the ventricle is reached.

162

Intraventricular AVM

Case 68 Posterior Portion of the Ventricle (It)

This 41-year-old carpenter had a severe intraventricular hemorrhage. Deep coma continued for 3 days, after which his condition improved rapidly. The operation was undertaken 2 weeks after the attack. Operation. With the patient prone the head was kept in a high position by inclining the operating table. A left medial parietal craniotomy was made. A straight cortical incision of 2.5 cm was made laterally from 3 to 5 cm off the midline. A ventricular tap was not tried in order to avoid injury to the AVM with its tip. The patient's head was kept perpendicular to the floor until the ventricle was entered; it was then rotated a little to the left to enable the surgeon to look perpendicularly through the microscope. The ventricle was packed with heavy clotting. Gentle suction of the clots and CSF provided a space and made it possible to identify the nidus. In the beginning a subependymal clot was mistaken for it. After packing the ventricular body with several cotton patties the nidus was isolated. Only a few small feeders were found around it and the drainer was much larger than the feeders. The nidus was removed without any trouble. Time from skin incision to closure was 2:20 h. Blood-loss was about 100 ml. The postoperative course was uneventful.

Comments. (1) Although the ventricle can be easily reached with the patient's head vertical especially in a case without preliminary ventricular tap, it is best to rotate the head after reaching it so that the lesion can be seen perpendicularly through the microscope. (2) As long as the corticotomy has been within 3 cm, or perhaps 4 cm maximally, we have never experienced postoperative deficits. Where to make the cortical incision is also of importance. Our recommendation is that the incision be made not in the center but in the upper (occipital) third of the bone window. The reason for this is that the corticotomy often moves down toward the frontal bone edge of the craniotomy at a later stage due to the collapse of the brain after suctioning of the CSF, especially in hydroce-phalic and elderly cases; retraction of the brain would then be difficult if the incision were made more frontally. (3) Whenever a large cavity is located close to an AVM or hemorrhagic tumor, packing of the space with cotton patties should never be neglected; packing the ventricular body in a case of intraventricular AVM is one example. (4) The reason for using a transparietal approach instead of a transtemporal or interhemispheric route for intraventricular lesions such as the AVM in this case is that we have not experienced postoperative deficits associated with the approach, whereas the transtemporal approach sometimes causes visual field deficits and in the interhemispheric approach the bridging veins obstruct the approach and may be injured, and in addition part of the corpus callosum must be cut.

163

продолжение

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166

AVM in the Basal Ganglia

Case 70 Feeding from Ml, Al, and PCA (It)

This 40-year-old man developed an intracerebral hematoma in the left hemisphere after a traffic accident six weeks before the operation. Unconsciousness continued for a week. Aphasia and right hemiplegia gradually improved. At the time of operation his right upper extremity was still markedly weak and there was a slight speech disturbance. 1st Operation. In the supine position, the head was elevated and rotated to the right about 60 degrees. A large left frontotemporal craniotomy was made. The brain was very tense even with Mannitol and hyperventilation. Numerous large tortuous varices and drainers were identified around the left carotid and middle cerebral arteries. The Sylvian fissure was opened wide. The parent arteries were also 1.5 times larger than normal. One big artery arising from the mid-portion of the M1 was found branching into two: one part went to the nidus and the other to the normal brain. A posterior portion of the pars orbitalis of the inferior frontal gyrus and

an anterior portion of the insular cortex were removed. (The removed portion turned out to be too small when dissection around the posterior portion of the nidus was attempted later.) After obliteration of the main feeder from the M l , two other large feeders from the A1 and anterior choroidal artery were sought. Their identification was, however, very difficult because the nidus and dilated drainers were so big. The nidus was dissected with meticulous attention to avoiding damage to the surrounding critical tissues near the basal ganglia. The upper half was easily coagulated; it became smaller. When dissection was attempted at the back of the nidus strong bleeding occurred and became difficult to control. Transient hypotension of about 70 mm Hg systolic induced with sodium ni-troprusside made bleeding control very easy. The longest time was spent on dissection around the posterior portion of the nidus because the area was very close to the internal capsule. After dissection of about three quarters of the nidus a tempo-

167

гагу clip was placed on the biggest drainer, resulting in neither bleeding nor bulging of the nidus. However, the drainer was left without complete obliteration. Complete isolation of the nidus was attempted but it was very difficult to control bleeding in the deep and narrow operating field. At this point the operation had already taken more than 12h. Total removal in one stage was abandoned. Postoperative course: The right hemiparesis and aphasia became worse for two weeks and then started to improve. One month later the patient was better than he had been preoperatively. The postoperative an-giogram showed moderate decrease of the mass. Two months after the first operation he underwent the second. 2nd Operation. The patient was positioned as before; care was taken to extend the neck with the chin up. After external ventricular drainage had been instituted through the right ventricle the previous cnmiolomy was reopened. The brain was nicely slack. First, an approach was made toward the chiasmatic region to expose the feeders from the distal carotid bifurcation and Al segment. This attempt, however, was hindered by dense adhesion caused by the first operation. The nidus was then dissected as in the previous operation, The lateral posterior portions were easily isolated to the point reached on the previous occasion without much bleeding. Next the dissection of the nidus in the anterolateral side was begun. This portion had not been touched much in the previous operation. Although bleeding from small pathological vessels was sometimes troublesome, it was possible to delin-

eate the antcromedial contour of the nidus with frequent application of induced hypotension as low as 60 mm Hg systotie. As more than 90% of the nidus seemed to have been isolated an 18 mm aneurysm clip was placed on the stalk portion containing a big drainer and some small vessels, which were running medially from the nidus. The tension of the mass weakened, while that of the vessel distal to the clip seemed to increase (see the color figure). Another long clip was temporarily applied to the nidus to shrink its bulk, facilitating ш approach to the deep ventricular side of the AVM. We asked the anesthesiologist to raise the blood pressure to about 100 mm Hg systolic. An egress of CSF from the ventricle was encountered while dissecting in the depth. Around this time a rather rapid bulging of the exposed brain occurred, making it difficult to continue the dissection. The CSF that escaped from the bottom of the operative field was clear, while drainage from the ventricular tube was bloody. The clip placed on the big drainer was immediately removed. It became impossible to continue the procedure because of massive brain edema. The blood pressure was lowered again. The brain softened somewhat with the aid of repeated Manmtol infusion and hyperventilation. Hemostasis was completed and all cotton pledgets were removed. One hemostasis clip was left as a mark on the wall of the vessel which had been tempo-

Case 70 coni'd on p. 168

168

AVM in the Basal Ganglia

Case 70 cont'd

rarily clipped. The wound was closed with the aid of Lyodura; cranioplasty was not performed. Total time was 9 h with 600 ml blood-loss. Postoperative course: Barbiturate therapy was continued for 3 days. The patient awoke well with right hemiparesis and mild aphasia, but consciousness became clouded and the hemiparesis worsened two weeks after the operation; both were progressive. The CT scan showed a large low-density area around the AVM. Signs of central nervous system infection were present. Two months later a hemorrhage occurred and he died 6 months later. The postoperative angiogram showed staining of another nidus posterior to the previous one; it had doubtless been hidden on the preoperative angiogram (see X-ray picture arrows).

6 AVM Around the Tentorial Edge Case 71 Above Quadrigeminal Plate (rt)

Comments. This is one of two fatal cases in our series of 72 AVMs. The attempt to remove it was probably reckless of me at the time; it was too large and too deep in a vital area to be removed without serious trouble. It is worthy of mention, however, that the neurological conditions immediately after both operations were not so bad, although the patient later became vegetative. The cause of the sudden bulging of the brain is not clear. The possibilities are the rather sudden deliberate increase in blood pressure, temporary clipping of a suspected larger drainer, or a combination of both. The postoperative CT scan showed ventricular hemorrhage, most likely subependymal hemorrhage. It is postulated that the temporary clipping obstructed the drainer not from the main nidus but from a residual daughter nidus which was located near the ventricle outside the operating field; it was fed by the posterior medial choroidal artery which had not been obliterated. The residual nidus would belong to Type С (Fig. IV-2, p. 137).

169

1 Right posterior cerebral artery 2 Right cerebellum ? Vein of Galen

This 42-year-old man suffered an SAH with severe headache, dizziness, and slight diplopia 6 weeks before the operation. The symptoms disappeared in one week. Operation. With the patient in the lateral position, the head was rotated a little more than 90 degrees and the right side of the neck strongly stretched toward the left shoulder. A right posterior subtemporal approach was taken with a craniotomy made above the external auditory meatus. The lateral bone edge was removed as far as possible, with care not to injure the transverse sinus. The brain was slack enough without CSF drainage. The subtemporal veins were sacrificed. Retraction of the temporal lobe was easy. In the occipital side of the operating field half of the AVM could be seen. Old clots were found behind the nidus. The icntorium was divided in the posterior side, preserving the trochlear nerve, and the whole nidus came into view. All of the feeders originated from the posterior cerebral artery, not from the superior cerebeUar artery. Coagulation of most of the feeders caused the color of the drainer to change from reddish to dark blue.

After it had been confirmed that temporary clipping of the drainer did not cause the nidus to bulge, the mass was coagMlated as much as possible. However, no attempt was made to remove it for fear of damaging the small normal perforating arteries feeding the tectal area. Operating time was two and a half hours with less than 200 ml blood-loss. The postoperative course was uneventful without additional deficits. Comments. As this AVM occupied only the right side from the midline all procedures, including the approach, identification of the feeders and dissection of the nidus, were easy with the unilateral suboccipital craniotomy. If a larger AVM extends into the contralaieral side other approaches such as the occipital interhemispheric route are necessary. It is generally better to remove the nidus than to leave it even after complete coagulation of feeders, drainers and the nidus itself. This operation was. however, more conservative than in later cases. The case was an earh one of our series where the pexfen-de. tectum and pons were attacked directly. Fortunately, the AVM disappeared on the postoperative angiogram.

170

AVM Around the Tentorial Edge

Case 72 On Lateral Pons (It)

This 42-year-old woman had suffered from tinnitus and hearing difficulty in the left ear for a long time. She had an SAH after blowing her nose. Severe headache, nuchal rigidity and vertigo continued for more than one week. She underwent the operation 3 weeks after the hemorrhage. Operation. With the patient in the lateral position a left middle subtemporal approach was made. The veins of Labbe were easily preserved by isolation from the cortex for a length of about 2 cm. The tentorial edge was divided posterior to the point where the trochlear nerve entered under the tentor-ium. The latter was opened from medial to lateral with special care to avoid injury to the drainers and petrosal sinus. Three feeders branching from the left superior cerebellar artery (SCA) were identified in the medial side of the nidus. The trunk of the SCA running behind the subtemporal area was preserved. Dissection of the nidus from the cerebellum was carried out clockwise from the medial through the posterior to the anterolateral aspect, because all the drainers were located in its anterior side. An old hematoma was found in the cerebellum. The anterolateral surface of the pons appeared under the nidus. Laterally behind the nidus the trigeminal nerve was visible and the facial and acoustic nerves were found far laterally behind large drainers and feeders. During dissection in the anterolateral area of the nidus much time was

spent paying meticulous attention to not damaging the pons, drainers and normal vessels from the anterior inferior cerebellar artery. Temporary clipping with an aneurysm clip of the remaining largest drainer, draining into the petrosal sinus, caused a remarkable bulging of the nidus, suggesting that some feeders remained. Further dissection was therefore done to completely isolate the nidus. A small feeder from the basilar artery was finally found under it. The obliteration of this resulted in shrinkage of the nidus while a temporary clip was applied to the drainer; the latter was then coagulated and divided and the nidus was removed. Four large normal veins around the main drainer were all preserved. The time from dural opening to closure was 3 h with less than 100 ml bloodloss. Postoperative course: Disturbance of touch and pain sensation in the left half of the body including the left face, weakness of the left arm, husky voice and nystagmus appeared. All these symptoms slowly improved. At discharge two months later only some loss of hearing in the left ear was noted. Comments. I was concerned to preserve the normal arteries branching from the basilar and anterior inferior cerebellar arteries which had mingled with the feeders. Although I thought I had preserved all of them, the postoperative deficits, though temporary, suggest that some of them were sacrificed.

1 Left petrous vein 2 Left Labbe vein 3 Left cerebellum

4 Old hemaLoma

7 Posterior Fossa AVM

Case 73 In the Vermis: Concorde Position

This 43-year-old man had an SAH 3 weeks before the operation. Operation. A horseshoe skin incision and suboccipital craniectomy were performed with the patient in the "Concorde landing" position; his head was elevated as much as possible (the operating table was inclined more than 30 degrees), the nucha was stretched maximally and the surgeon sat by the patient's left shoulder. Many red veins and feeders were found around the upper vermis. Two inferior vermian veins running downwards on the vermis were isolated from its surface for about 2 cm; this made it possible to preserve the veins throughout the subsequent procedure. The nidus was found about 15 mm behind the confluens. Without touching the drainers, dissection around the nidus was advanced as far as its bottom, where the main feeders from the bilateral superior cerebellar arteries were located as had been suspected from the angiogram. The main feeders were coagulated and divided. Test clipping of the drainer did not cause the nidus to bulge. Thus, removal of the nidus was simple. Total time from skin to skin was four and a half hours with 600 ml blood-loss, mainly during craniectomy. The postoperative course was uneventful.

Comment. The Concorde position is useful for the approach to lesions just under the tentorium. We sit in the usual position in front of the patient until the dura is opened and then move to the patient's left shoulder. In this way the microscope can be used at a normal angle and still the patient's head can be kept high. Preservation of the inferior vermian vein is usually possible when the lesion is not large. In the majority of cases sacrificing it results in no postoperative deficits. On the other hand, it is to be supposed that preservation of the vein will reduce any postoperative cerebellar edema to various degrees. Unlike in the sitting position an air embolism is not a matter of concern unless the table is inclined more than 45 degrees. Concorde Position. For lesions in the pineal and midline supracerebellar regions such as pineal tumors of various pathologies, midline infratentorial arteriovenous malformations, midline superior cerebellar tumors and some tentorial meningiomas, we utilize an infratentorial supracerebellar approach with the patient in the prone position (Concorde position). Our method is distinctive in that the patient is placed in a prone position with the head flexed and higher than the heart level and the surgeon sits on the left side of the patient. Inclination of the table should not exceed 45 degrees. The main advantages of this arrangement over the sitting position include less fatigue on the part of the surgeon and less possibility of air embolism. The patient's head is flexed, but it should not be bowing down. In order for the surgeon to sit and operate comfortably, it is important to place the patient as far to the left edge of the operating table as possible, and tilt the patient's head slightly to the right when the surgeon is right handed. We prefer the patient to be maintained on spontaneous respiration during the procedure for the reasons described in the chapter on acoustic neurinoma. We use a U-shape (horseshoe) or reverse W-shape skin incision just under the nuchal line for a large or deep-seated lesion. A vertical skin incision is less favorable except for a small superficial lesion because the lateral bands of the muscle disturb the surgeon's vision when a lateral corner of the operating field is dealt with by tilting the axis of the microscope. The muscle layers are cut

173

1 Confluence 2 Inferior vermian vein

in a different plane from the skin incision, The suboccipital craniectomy is made bilaterally to expose both medial halves of the cerebellum. The actual extent of the lateral bone opening depends of course on the nature of the lesion for which the operation is undertaken. Opening the foramen magnum is usually unnecessary. It is imporlanl to remove bone to partially expose the transverse venous sinus. In the Concorde position, the cerebellum sinks by its own weight and only a slight downward retraction of the cerebellum is necessary. The height of the space obtained between the tentorium and the upper surface of the cerebellum is about 2 cm, but this is sufficient to operate on various kinds of lesions under the microscope. The width of about 8 cm in this approach allows the microscope to be used from different angles and the surgeon to use both his hands. A transverse space is usually easier for ihe sunieon and assistants than the vertical.

174

Posterior Fossa AVM

Case 74 Giant AVM in the Vermis (Bilateral)

This 36-year-old man had suffered headache, blurred vision, drunken gait, slurred speech and ataxia for more than one year. The symptoms became worse 5 months before the operation. No seizure or SAH was observed. A three-stage operation was planned because the AVM was large, with multiple high-flow feeders from various directions. 1st Operation. For the purpose of obliterating the feeders from the right superior cerebellar artery (SCA), a right subtemporal approach was taken with the patient in the lateral position. The skin incision had been much discussed before the operation because the contralateral subtemporal and suboccipital approaches were expected to be performed later: the incision line was important for each approach. A subtemporal approach was performed anterior to the vein of Labbe, which was preserved. While the tentorial edge was being opened a big drainer was inadvertently injured with a sharp hook, which caused strong bleeding. The bleeding point was, however, simply controlled with Oxycel with transient hypotension induced for 5 min. Two big dilated arteries, which were a double SCA without branches, were identified in the crural cistern. Both arteries had pathological walls with uneven surface and thin muscle layer; the thinness of muscle layer was indicated by the fact that the vessels did not shrink with bipolar coagulation. They were ligated, clipped with Week's clips and divided. In the medial side of these feeders the normal posterior cerebral artery with a normal appearance was found (the upper color figure). Postoperatively the patient developed euphoria for more than a week without other deficits. Mild renal dysfunction delayed the second operation for a month.

2nd Operation. Obliteration of the feeders from the left SCA was performed with the patient in the lateral position. It was very difficult to open the tentorium without injuring the trochlear nerve located entirely below it and the strongly adherent dilated feeders and drainers. Two large feeders from the left SCA were ligated and divided. Three drainers running around the feeders, which became soft after obliteration of the latter, were also cut. After the second operation a depressive and drowsy state appeared and the ataxia worsened, though the CT scan showed no new lesion. The angiogram revealed a reduction in size of the nidus (X-ray picture, lower column). 3rd Operation. A suboccipital approach was performed utilizing the Concorde position. A horseshoe skin incision and large suboccipital craniectomy were made. The AVM was found in the vermis. Dissection of the nidus was easy up to the point where we had isolated three quarters of it with less than 100 ml blood-loss. The fourth ventricle was opened under the ventrocaudal portion of the nidus. First, slight bleeding appeared from the side wall of the left cerebellum which had been dissected from the mass. A few minutes later, the bleeding became stronger. While we were dissecting and suctioning around the bleeding point the whole cerebellum became swollen, and the blood pressure fell. A small residual daughter nidus was eventually found in the left cerebellum and the main source of the bleeding was a feeder from the left anterior

Case ~"4 cont'd on p. 176

1 Right superior ccrebellar artery 2 Right Labb6 vein

1 Confluence 2 Bleeding point (Type С nidus)

3 Left posterior lentorium 4 IVth ventricle

176

Posterior Fossa AVM

Case 75 In the Tonsil (rt)

This 60-year-old woman suffered a severe SAH with vomiting, vertigo and ataxia one month before the operation. On the CT scan a large hematoma was found in the right cerbellum. Mild ataxia persisted preoperatively. Operation. With the patient in the prone position, a horseshoe skin incision was made for a suboccipital craniectomy which was a little difficult because the patient's head had not been flexed enough. The cerebellum was not tense. Its surface was normal except for a few red veins over the right tonsil. With retraction of the latter and of the adjacent biventral lobule two large feeders were identified, the bigger one coming from the PICA and the smaller from the AICA. Part of the nidus was found behind the right tonsil; it occupied most of the right tonsil and biventral lobule. After the feeders from the AICA and PICA had been coagulated and divided the right tonsil and a portion of the biventral lobule were removed. The upper three quarters of the nidus was easily dissected almost without blood-loss, but the bottom portion of it resisted dissection; bleeding control of all vessels, small though they were, was very difficult because they had a thin wall under high intraluminal pressure. In particular the narrow operating field under the nidus, close to the medulla, made the procedure very difficult (the actual field was much narrower than that shown in the color figure). After about

90% of the mass had been isolated on 18 mm aneurysm clip was placed on it. The portion above the clip was coagulated and cut. Another clip was placed beneath the first, which was removed, and the residual upper portion again cut off. Such alternate application of two clips enabled us to remove most of the nidus and to obtain a large space. Finally a bent clip, No. 12, was placed on the biggest drainer and the fine vessels, which were intensely coagulated. The clip was left in place. The total time was 5 h and blood-loss was 500 ml. Postoperative course: Ataxia worsened and difficulty in swallowing continued for two weeks. Two months later all deficits disappeared (postop. angiogram: right). Comments. The operation was easier than we had anticipated; the preoperative angiogram suggested that the lesion would be located more in the medullary side close to the cerebellopontine angle. The only difficulty occurred when we attempted to coagulate many small red veins at the bottom of the nidus in the final stage, even though we had already obliterated the two main feeders. Such difficulty usually occurs in the final stage of AVM operations: the bleeding points are located under the nidus, which obstructs the view, and the problem is worse when the nidus is at the bottom of a narrow operating field. One way of coping with this kind of situation is the alternate use of two long clips to enable excision of most of the remaining nidus.

Case 74 cont'd

inferior cerebellar artery. After controlling the daughter nidus, the main nidus occupying the center was removed without trouble. As the cerebellum was still moderately swollen the dura was closed with the aid of wide Lyodura patching. Postoperative course: The patient died after remaining in a deep coma for two weeks. Comments. This is one of the two fatal cases in our series of 72 AVM operations. Obliteration of the bilateral SCAs would have caused the additional neurological deficits of depression and drowsiness after the second operation, though

only the maximally dilated drainers were sacrificed and the normal arteries were not touched. The final direct attack on the AVM was not actually difficult except for the bleeding from the small daughter nidus. It was a typical example of a fatal residual nidus of type C, as explained earlier in Fig. IV-2, p. 137. In this operation I wanted to dissect the nidus from the cerebellum with minimum damage to the normal cerebellum because severe ataxia was already present. For this reason the dissection was carried out too close to the main nidus, missine the daughter nidus.

177

1 Right PICA I Feeding artery 3 Main drainer 4 TVth ventricular floor

8 Hemangioma General Considerations

Although the basic surgical principle for hemangioma is almost the same as for AVM surgery, a few differences are: 1) Hemangiomas are less hemorrhagic than AVMs, though the feeding arteries should be obstructed in the initial stage of the procedure. Generally a hemangioma does not have a high shunt flow. 2) We do not need to pay so much attention to preserving draining veins and may sacrifice them at a relatively earlier stage than in AVM surgery. The number of large dilated draining vessels is much smaller in a hemangioma than

in an AVM. 3) Decreasing the mass by coagulation of its surface and by obliteration of the feeding arteries is done far less with hemangiomas than with AVMs. Hemangioma has the character of a brain tumor such as a hemangioblastic meningioma, and when the mass is large we should remove it piecemeal with the aid of temporary clipping of the mass with an ultralong clip and coagulation of the cut surface. Piecemeal removal can be done more frequently than in an AVM. 4) Usually bleeding control becomes easier in the later stage in hemangiomas, contrary to AVMs where the procedure becomes increasingly difficult.

Case 76 Feeding from the Superior Cerebellar Artery (rt)

This 53-year-old man suffered a sudden onset of nausea, vomiting and ataxia two months before the operation. Operation. With the patient in the lateral position, a right posterior subtemporal approach was made. The temporal lobe was sufficiently retracted without sacrificing the vein of Labbe. The tentorium was opened wide, where the trochlear nerve was identified in the crural cistern. A hemangioma was found laterally along the trochlear nerve and superior cerebel-lar artery. Most of it was located in the cerebellum. Its surface. thoueh hiehlv vascular, was far more easilv coagulated than

a usual AVM. It was easily retracted laterally with a tapered retractor after the surface had been coagulated. A large intracerebellar cyst was found in the lateral side of the tumor, and a large feeding artery was found branching off the SCA on the pontine surface under it. The hemangioma was clearly demarcated from the surrounding tissues. Big drainers were found on both sides, one running to the petrosal sinus and the other toward the straight sinus. Coagulation and section of the former drainer facilitated retraction of the mass to the posterior (occipital) side, sectioning of small feeders, and isolation from the pontine surface. Removal was simple and successful. The time from dural opening to closure was one and a half hours with less than 100 ml blood-loss. The postoperative course was uneventful. Comments. Generally the same precaution should be taken in the operation for a hemangioma as in that for an ordinary AVM: first the feeders are obliterated and then the drainers. We may on occasion proceed differently when, for instance, leaving the drainers till the final stage would cause difficulty isolating the whole mass. The usual hemangioma is not as hemorrhagic as an AVM. Of course, temporary test clipping of the drainer should be done prior to sectioning.

180

Hemangioma

Case 77 In the Cerebellopontine Angle (It)

This 52-year-old man had undergone partial removal of a hemangioma 6 years earlier. He had recently developed ataxia again without other deficits. Operation. With the patient in the lateral position an approach was made through the previous craniectomy. Ventricular drainage was instituted in the left posterior horn. First, an approach to the hemangioma was made from the tentorial

side to identify the trochlear nerve and the superior cerebellar artery from which the biggest feeder branched. The tentorium also had a large feeder, the Bernasconi Cassinari artery, which was seen on the carotid angiogram (arrow). In order to identify and cut these feeders a medial portion of the tentorium was removed. This area was strongly adherent to the tumor due to the previous operation. Then the mass was dissected from the cerebellum. The feeders from the posterior inferior cerebellar artery were obliterated. After isolation from the important tissues including the cranial nerves IV through X, and posterior cerebral and superior cerebellar arteries, the hemangioma mass was easily handled. The anterior inferior cerebellar artery was not found. Bleeding from the hemangioma was rarely encountered. Time from skin incision to closure was 5 h with 600 ml blood-loss, half of which occurred when reopening the previous craniectomy. Postoperative course: The patient awoke well from anesthesia but his left arm was paralysed for two days. It recovered fully two months later. The preoperative cerebellar ataxia gradually improved, and he returned to his previous occupation without handicap. Comments. (1) This operation was much easier than it would have been for an AVM of the same size because the hemangioma was far less hemorrhagic. It is always important to obliterate the feeders as soon as possible. In principle this applies also to other tumors such as hemorrhagic meningio-mas and gliomas. (2) This case was the only one out of over 200 operated on in the lateral position where a complication developed due to incorrect positioning; a bandage pulled the medial side of the left shoulder instead of its top, injuring the left brachial plexus or compromising the blood flow. Fortunately the paresis was only transient.

181

1 Left posterior cerebral artery 2 Left superior cerebellar arlery 3

Ten tori urn

182

Hemangioma

Case 78 Cerebellar

This 42-year-old woman underwent a suboccipital craniectomy 10 years ago after complaining of headache, vertigo, gait disturbance, and diplopia on left lateral gazing. The operative finding was a large intracerebellar cyst; the histological diagnosis was astrocytoma. After the operation she had fully recovered and was working until about 2 months earlier when she began again to experience the same complaints. The vertebral angiography revealed a huge hemangioma in the left cerebellum with extremely high vascularity like an AVM. The preoperative angiogram of the first operation showed a large a vascular area. Operation. With the patient in the prone position, where special care was taken to place her head higher than the heart level, a midline suboccipital skin incision was made; the skin incision in the previous operation had been a right-sided J shape. A left lateral craniectomy was added far enough to visualize the sigmoid sinus. The cerebellum was not tense. The tumor was found on the surface of the left cerebellar cortex. Dissection of it from the cerebellum was not difficult but it was relatively hard like a firm sponge and hemorrhagic. The, main feeder from the left PICA was found in the cisterna magna and was coagulated and divided. The whole surface of the tumor including feeders and drainers was intensely coagulated. Two or three feeders were found on the bottom surface and they too were coagulated. The lateral portion of the tumor was strongly adherent to cranial nerves X and XL The tumor was retracted mainly laterally and caudally because this way retraction was directed toward the bony structure and vital structures were not compressed. The fourth ventricle

was behind the tumor. Although more than 90% of the surface was isolated, some feeding arteries apparently remained because the tumor was still hemorrhagic and its mass did not decrease. Complete isolation from the surrounding tissue was clearly impossible. We had already spent 4 h on the dissection. A decision was made to decrease the mass by piecemeal removal. This started at its medial portion and moved step by step to the lateral. I moved from the midline of the patient to her left side to look at the tentorial side of the tumor. This position was very convenient. After half of the mass had been removed the remaining feeder was found behind a big drainer at the bottom of the tumor. Cutting the feeder resulted in a complete cessation of oozing. Total blood-loss was 1,000 ml; about a half of this was during dissection around the tumor and the rest during piecemeal removal. The total time from dural opening to closing was 7 h. Postoperative course: She awoke fully. On the first night severe nystagmus in almost every direction appeared; it took about two weeks to disappear. She developed mental depression which continued about a month. Three months later she was able to work normally without neurological deficits. Comments. (1) What made this operation so difficult was that one feeder could not be found until the medial half of the tumor had been removed; it was hidden under a big drainer in the lateral side and close to the medulla. (2) If piecemeal removal of the tumor had been done sooner, after obliteration of the main feeder located in the cisterna magna and without spending so much time on dissection around the tumor, removal would have been much easier, the total time

is:

1 Feeding artery from left PICA 2 Spinal cord 3 Floor of the IVth ventricle

much less, and less blood lost. (3) A marked difference between an AVM and a hemangioma is that the latter remains as a large mass until the final stage even after coagulation of the tumor and feeders while the AVM becomes smaller step by step as the operation proceeds. It is a frequent problem with a hemangioma t h a t its mass hinders dissection from structures under it. (4) The patient's position was very important. Elevation of the head about 10 cm above the heart level caused a decrease in oozing of about a half. But when working on the tentorial side with the patient in such a position it is essential that the surgeon sit beside the patient. (5) A frequent postoperative complication of procedures in the cercbcl-lopontine angle is menial depression, which usually responds to antidepressive drugs. The details are discussed in the section on acoustic neurinoma. продолжение

продол жение

V Meningioma General Considerations

The skill and techniques of a surgeon, and what we may call his philosophy, are faithfully reflected in the operative results he obtains in meningioma and neurinoma cases. Total removal of a meningioma is nearly always possible and must be attempted. Radical removal, however, may sometimes cause severe and permanent deficits; the surgeon should take care not to overestimate his own skill. The postoperative condition of the patient is the most important matter, and this must be assured even if it means that a small portion of the tumor has to be left behind. Today, follow-up study is easily carried out with the aid of the CT scan; furthermore the majority of meningiomas grow very slowly. Even if radical removal without deficits is difficult at present and reoperations are sometimes difficult due to adhesion, it may become possible 10 years hence with further technical advancements. 1. The position of the patient's head has a considerable influence on the likelihood of troubles arising during the procedure and on the postoperative results; in principle, the head must be elevated as high as possible to reduce the intracranial and venous pressures. Flexion and rotation of the head must be ideal so that all sides of the mass can be easily visualized with the operating microscope. 2. The craniotomy should be made sufficiently large, though the more cases the surgeon experiences the smaller the craniotomy he tends to make. Every effort to slacken the brain should be made at the beginning of the approach.

185 3. We use an operating microscope from dural opening to closure with frequent changing of magnification. The pedalcontrolled X-Y shifter is more useful in the operation foi large tumors than in that for aneurysms because the microscope must be moved over a very wide area. 4. Dissection of the meningioma attachment: In principle the first step is to dissect the attachment of the meningioma where almost all feeding arteries are located, although this is not always possible. Isolation of the attachment at the initial stage facilitates the subsequent procedures and there is less loss of blood. Even in the case of a huge meningioma a small, but adequate, space to reach the attachment can usually be obtained by retracting the tumor with a four-pronged hook. Dissection of the attachment is possible even in a very smal space when a microscope is used. The most severe bleeding in the whole procedure of removing a meningioma is encountered during dissection of the attachment to the dura or bone. (1) In addition to the basic technique of hemostasis with the bipolar coagulation forceps, it is recommended that the attachment is dissected in a plane a few mm distant from the bone when bleeding from the bone is extremely strong. Coo-trol of bleeding in the portion of the tumor on the bony side is then often much easier than when the bony surface is a1-tacked directly. Of course, the remaining portion is complete, removed together with bone involved by the tumor in the final stage after the main mass has been removed and a lane space obtained. The brisk bleeding which occurs in the attachment in the beginning becomes easily controllable in the final

Table V-l. Surgical Results of Meningiomas

(1) Grade at operation. G I: radical removal. G II: attachment remained. G III: less than 10% of mass remained. G IV: more than 10% remained. (2) Cases J to 5 are described in the text. l Case 83. 2 Case 87 (case 2). 3 Case 91-2. 4 Case 95. 5 Case 97. 6 The 73 y-o patient developed an infarct on the postoperative day in an area unrelated to that operated on and died 2 months later. (3) The above classification is made on the basis of site of tumor attachment. When the attachment was extensive, the tumor is listed according to the location of the main attachment: definite classification was sometimes difficult especially in the cases of posterior tentorial. pyramidal, clival. and posterior fossa meningiomas. (4) The distribution of cases according to location is quite different from those of other reported series because only difficult cases woe referred to me.

186

Meningioma

Fie. V-1

stage because the vessels become thrombosed during the procedure. (2) When severe bleeding which is uncontrollable with bipolar forceps is encountered, the bleeding point is covered with Oxycel and a cotton patty which are pushed against the bone with the suction: this is a standard method. When more time seems to be necessary for hemostasis the patty is held against the bony side by a tapered brain retractor connected to a self-retaining retractor. In this way both the surgeon's hands can be devoted to dissection elsewhere without loss of time. (3) As noted earlier, retraction of the main mass with a fourpronged hook provides a small space between the bone and the mass even at the beginning of the operation when the brain is tight. Although the gap is very small, it is sufficient to separate the attachment under the operating microscope. 5. Bleeding control on the bone: Control of bleeding from a meningioma attachment in the base of the skull where the main feeders are located is an important technique. A piece of bone wax is put on the bleeding point and is pressed with a cotton patty in the usual way. The wax, however, often becomes loose when the patty is removed (Fig. V-1 left). A useful trick in such a situation is our "sandwich method". After the wax is put in place it is covered with a small amount of Oxycel. A cotton patty is put on top of this and all three materials are pushed against the bleeding point for a short

time. After the bleeding has stopped, the patty can be easily detached from the Oxycel covering the wax, so that the wax stays in place. This sandwich method is also useful to control oozing from the removed sphenoidal ridge in aneurysm surgery (Fig. V-1 right). 6. The critical structures around the tumor such as the major arteries and cranial nerves must be identified as early as possible. They are ordinarily located behind the tumor, but localization in the initial stage is frequently possible and is certainly worth trying. Their early identification facilitates speedy removal of the mass without excessive attention to them. On the other hand, it should be remembered that an important structure is sometimes embedded in the mass. When a nerve or artery is not found around the surface of the tumor and is suspected to be embedded in it, dissection of the tumor should be performed tangentially along the suspected course but never across it; in particular, sharp dissection with a knife, monopoiar coagulator or high powered ultrasound suction should be avoided until the structure is found and secured. |It is noteworthy that in neurinomas, unlike meningiomas, cra-:nial nerves (except one from which the tumor has originated) and arteries are always located on the surface of the tumor capsule. 7. Retraction of the meningioma itself is performed with a four-pronged hook, which is one of the indispensable tools

187

for removal of such a tumor. At the beginning of the excision procedure the tumor mass close to the attachment is retracted slightly away from the bony side with the aid of a hook connected to a self-retaining retractor. Although the direction of retraction is toward the brain at this stage, the direct effect on the brain is not great because the large hard mass of the meningioma with its strong attachment to the dura and the bone prevents excessive retraction. The main application of t:he hook is to retract the mass from the brain laterally to the bony side or medially to the falx or tentorium. The hook helps the surgeon the most when he is dissecting the tumor from such critical structures as cranial nerves, main arterial trunks, peduncle and pons (Fig, V-2).

8. The extirpation is better not performed in the usual manner described in textbooks, which say that the central portion should be removed first. Only when the meningioma is soft and avascular is the central portion decompressed. In a hard or hemorrhagic meningioma the attachment of the tumor should be removed first and the portion close to critical structures dissected next or even simultaneously. Removal of the lateral portion makes it possible to obtain a space between the tumor and the brain with minimal retraction of the tumor. Utilizing the space thus obtained the tumor is retracted in all directions with minimal brain retraction and its entire surface is isolated from surrounding tissues; the vessels on the surface can then be coagulated. If the central portion is removed first, bleeding continues until the final stage when all of the arteries and veins located on the surface have been obliterated and the tumor attachment is sectioned. When the mass is hard, central decompression does not facilitate reaching the bottom portion of the tumor where the attachment and important structures are often located unless almost all the contents are removed. It also requires much time, and a considerable amount of blood is lost. We have not used the ordinary ring-cutter of the monopolar high-frequency co-agulator except for some rare hard meningiomas (less than 5% in the series). In our practice, removal of the central portion of the tumor is performed when necessary using a large suction with an inner diameter of 4 mm, held in the surgeon's dominant hand for optimum control of the instrument-Mostly scissors and bipolar coagulator are used. 9. Empirically, a meningioma is usually avascular if haid but hemorrhagic if it is soft. More than 80% of the tumors are not hemorrhagic even if high vascularity is found on the angiogram. More than 30% are as soft as glioma. and arc easily removed with only an ordinary suction. Fortunately, as it is the most difficult, a hard and hemorrhagic mass is very seldom encountered.

1 Anterior Skull Base Meningioma Case 79 Optic Nerve (rt) rt 1

This 48-year-old woman had noticed slight visual disturbance for three years and exophthalmos for two years. On admission her vision was 0.05 in the right eye and 1.2 in the left. The visual field of the right eye was severely restricted. Operation. A right frontotemporal approach was taken. First, the dura was opened and the intracranial portion of the right optic nerve was checked, though the CT scan had shown no positive signs of intracranial mass. A small part of a meningioma was found in the medial side of the optic nerve near the optic canal; this was easily removed. Then the right optic canal and the orbital roof were widely opened. The intraorbital fat and muscles were retracted with the aid of four tapered brain retractors, each of which was held by a selfretaining retractor. The meningioma was found along the whole course of the optic nerve from near the bulbus to the canal. With meticulous care the tumor was detached from the nerve. The ophthalmic artery, however, was not found even in the region close to the carotid artery. The tumor was completely removed, and the dura propria partially resected. Postoperatively, the exophthalmos disappeared and ex-traocular movements were well preserved. The right eye, how-

ever, was blind. Two years later the tumor was found on the CT scan to have recurred around the intraorbital portion of the right optic nerve. The whole of the optic nerve was removed with the meningioma. Comments. (1) It is reported that vision after removal of a meningioma of the intraorbital optic nerve sheath is generally unsatisfactory. Our results in three meningiomas in the same location confirm this, though the postoperative vision was well preserved in other intraorbital meningiomas without attachment to the optic nerve. Total removal of this lesion must include resection of the dura propria, which, however, greatly compromises the blood supply to the optic nerve even without the slightest injury to the nerve itself; hence the postoperative blindness with this lesion. (2) The most troublesome obstacle in the intraorbital operation is the intraorbital fat and muscles; the fat is especially disturbing because it is difficult to retract. One way to deal with this problem is to coagulate the fat with bipolar forceps. Another is to apply multiple tapered brain retractors 2 mm in width, each connected to a self-retaining retractor. Combined use of the two methods gives an excellent operating field.

189

190

Anterior Skull Base Meningioma

Case 80 Tuberculum (It)

This 59-year-old woman had complained of severe headache and vomiting for one month. Three days after deterioration of consciousness had appeared an emergency operation was performed. Operation. A large left frontotemporal craniotomy was made under administration of a large dose of Mannitol and hyperventilation. The brain was tense. A highly vascular tumor was found at a depth of 3 cm from the frontal bone edge. First, the attachment of the meningioma to the orbital roof was dissected with the least possible retraction of the frontal lobe (step 1 in the lower picture). Although every step of the dissection caused considerable hemorrhage, the bleeding was controlled with bipolar coagulation and bone wax with Oxycel. A useful procedure to reduce the operating time was to apply a cotton patty and Oxycel to a bleeding point and hold it gently in place with a tapered retractor connected to a self-retaining retractor; in the meantime the surgeon could continue dissection of another portion. In order to identify the left carotid artery and optic nerve (step 2) and also to drain CSF from the chiasmatic cistern, the lateral side of the attachment was dissected before the medial. Medial retraction of the tumor with a four-pronged hook greatly helped this part of the procedure. After both important structures had beep identified the attachment was quickly dissected, following which the tumor became nonhemorrhagic and obedient. Almost no bleeding occurred during the subsequent dissection. The anterior one fourth of the mass was dissected

en bloc (step 3), and the remaining portion was then removed piecemeal. As the left carotid artery and optic nerve had been separated from the tumor by the arachnoid their isolation was easy, but the left anterior cerebral and anterior communicating arteries were severely involved by the tumor (step 4). All the main arterial trunks were well isolated but one branch of the left frontobasal artery was injured. At the final stage after removal of the mass, the bone of the left orbital roof, anterior clinoid process and optic canal was removed with a diamond drill. The total blood-loss was 800 ml. The operation took three and a half hours. The postoperative course was uneventful". Comments. The most important tactic is to dissect the attachment first. When a meningioma is hemorrhagic its division stops arterial bleeding from the tumor because almost all feeding arteries are located in it. Dissection of the attachment has the further advantage of facilitating mobilization of the mass and identification of the critical structures behind it. A useful technique when dissecting a hemorrhagic attachment is, as noted earlier, to dissect not on the bone but in the tumor a few mm distant from the bone where bleeding is often easier to control. The residual tumor bed on the bony side is removed in the final stage after a large dead space has been obtained. Sites of brisk bleeding on the bony side become very obedient toward the end of the procedure as they thrombose.

191

Dotted line: Tumor

192

Anterior Skull Base Meningioma

Case 81 Tuberculum (Medial) (Bilateral)

This 61-year-old woman had complained of severe bilateral visual involvement for the past year: light perception in the left eye and hand movement in the right. In addition she had suffered a large infarct in the area of the left middle cerebral artery 4 months earlier, on account of which she developed right hemiparesis and aphasia. The angiogram showed a threadlike stenosis of the left carotid artery, and STA-MCA bypass surgery was performed 6 weeks before the operation for the meningioma. Operation. A bilateral coronal skin incision and a bilateral frontal craniotomy were made with care not to injure the artery anastomosed previously. The bilateral craniotomy and atrophic brain enabled us to obtain a wide operating field with minimal brain retraction. The tumor was attached to the dura around the medial side of the right optic nerve; the attachment was easily dissected. The anterior portion of the tumor was removed. Retraction of both lateral sides with a hook helped us to identify the sclerotic carotid arteries and atrophic optic nerves of both sides. As the tumor was not hemorrhagic it could be removed piece by piece with minimum blood-loss. It was located mainly in the prechiasmatic area,

but had spread in every direction and protruded into every narrow gap; bilaterally under the carotid arteries, between the artery and optic nerve symmetrically on both sides, poste-' riorly above the anterior cerebral arteries, between the arteries and the chiasma, and under the chiasma. Half of the protruding portion of the tumor was easily extracted because there was no adhesion to the surroundings, but the rest was adherent to important structures. Dissection around the anterior communicating artery was especially difficult, and a branch from the left anterior cerebral artery had to be sacrificed. In the bottom of the operating field the tumor was easily removed because the surrounding tissues were separated by the strong arachnoid. The dorsum sellae and flattened stalk were clearly seen. After removal of the main mass, the attachment medially beneath the right optic nerve was removed. A small portion under the right optic nerve was left for fear of additional visual deficits. Time from dural opening to closure was 4h with 300ml blood-loss. Postoperative course: For a couple of days consciousness was mildly disturbed. Her vision was the same as it was preoperatively, and the neurological condition did not improve significantly. Comments. It is possible to remove a large mass in this region by a unilateral frontal craniotomy, and we have in fact done this in some cases. The bilateral frontal craniotomy, however, gives a much larger and clearer operating field than the unilateral; the operative procedure is easier and less brain retraction is necessary. Visual disturbance that began more than 6 months before operation generally cannot be improved by surgery in the case of tubercular and parasellar meningio-mas. Postoperative worsening of vision was seen only exceptionally in our series.

1 Anterior communicating artery 2 Pituitary stalk 3 Posterior clinoid process 4 Tumor attachment.

194

Anterior Skull Base Meningioma

Case 82 Tuberculum (rt)

This 47-year-old woman noticed headache and visual impairment about one year earlier. The neurological findings were right hyposmia, right hand tremor, bradykinesia and visual disturbance; visual acuity was 0.2 (c.c) in the right eye and 0.05 (c.c) in the left, with unilateral lower nasal quadrantanop-sia in the right eye. Operation. A right frontotemporal craniotomy was made. The Sylvian fissure was opened wide. The tumor was soon found by retraction of the frontal lobe. It was hard but not hemorrhagic. The attachment to the right anterior clinoid and tuberculum was dissected. The bilateral optic nerves and carotid arteries were identified without difficulty. The tumor was removed piecemeal from the anterior portion to the posterior. While the optic nerve seemed to be elevated by the carotid artery, the optic tract was pushed downward by the tumor, which protruded mainly above the right A1 and partially below and between the distal portion of the right A1 and right optic tract; the right Al and anterior communicating artery \vprp tntallv embedded in the tumor, and it was most difficult

artery, probably Heubner's artery, was sacrificed. In the bottom of the operating field a pituitary stalk was clearly visualized posterior to the chiasma. After the main mass had been removed the attachment around the right anterior clinoid and tuberculum was removed with the dura; the bone was not drilled off but coagulated by monopolar electrocautery because the dura could be smoothly detached from it and it apparently had not been invaded by the tumor. The time for the main procedure was 2 h with 200 ml blood-loss. The postoperative course was uneventful. All neurological deficits improved, especially the patient's vision, which became 1.0 and 0.8 in the right and left eyes respectively. Comments. The operation was easy because the tumor was soft and not very hemorrhagic except for the adhesion involving the bilateral proximal anterior cerebral and anterior communicating arteries. Although the right Heubner's artery was suspectedly sacrificed, no deficits ensued. It was assumed that circulation through the branch had been disturbed by the tumor mass and that collateral flow had developed. In almost

1 Chiasma 2 Pituitary stalk 3 Space after tumor removal

196

Anterior Skull Base Meningioma

Case 83 Tuberculum (rt): Metal Shield

197

This 50-year-old woman underwent a frontal cranioiomy for visual disturbance 25 years ago; the diagnosis at that time was unclear. Her visual disturbance had continued, getting slowly worse. In the last five years she had developed bilateral hemianopsia and her vision was worse than 0.1 bilaterally just before the operation. Operation. A large right frontotemporal craniotomy was made. The Sylvian fissure was opened wide and the right frontal lobe was retracted. The tumor was found immediately. The attachment was mainly to the right anterior clinoid process and the anteromedial portion of the tentorium. Many large feeding arteries were found in this region. Dissection of the attachment lessened the bleeding from the tumor. The. right carotid artery was completely embedded in the tumor and was strongly adherent to it. The tumor was found to haye spread between the right optic nerve and the carotid artery. The bilateral optic nerves were paper-thin. The proximal portion of the right anterior cerebral artery (Al) was entirely embedded in the Vumor, which had also invaded deeply into the hypothalamus. Severe bleeding was encountered during dissection from the right carotid artery close to the anterior clinoid process. A tear in the artery was packed with Oxycel and covered with a cotton patty, resulting in good control of the bleeding. Removal of the tumor advanced

further. The stalk was found in the bottom of the operating field. When about 90% of the mass had been removed, the cotton patty on the carotid artery was removed to complete dissection of the^mass remaining around the artery. The bleeding started again, and this time it was much stronger. Temporary clipping was impossible because the tear was close to the anterior clinoid process, where the arterial wall seemed very weak. Under compression of the cervical carotid artery the bleeding was stopped with Oxycel covered by a cotton patty while maintaining the patency of the carotid. In the meantime much blood was lost. Total removal of the tumor was abandoned; the remaining portion was around the right Al and distal carotid artery. Postoperative course: The patient did not awake and died one week later. Comments. This is one of three deaths in our series of 93 meningiomas; in this case the death was due to a technical failure, in the second to anesthetic failure, and in the third to postoperative coincident infarct. Although the exact cause of death in the present case was unclear, two were suspected: mishandling of the torn carotid artery and/or an overly aggressive attack on the hypothalamus, which the rneningioma had invaded. In retrospect, if excessive maneuvering in the region of the torn carotid artery had not been done the operation could have been successfully completed because the first

198

Anterior Skull Base Meningioma

Case 83 cont'd

control of bleeding worked so well. An arterial wall embedded in a meningioma is often very weak, and should not be handled too much. A two-stage operation should have been done in this case. After this unsuccessful experience the use of a metal shield was developed.

Use of Metal Shield The metal shield, made of stainless steel, has three different sizes: 3 (curvature) x 4 (length) mm, 4 x 5 mm, and 5 x 6 mm. The size of the shield is selected according to the size of the injured artery. It is held with conventional appliers for Sugita, Heifetz and other clips. A small amount of Oxycel is glued to the inner surface of the shield with such glues as Biobond or fibrin glue. While the blood is suctioned, the shield should be placed so that its inner surface pushes against the injured portion of the artery. Bleeding stops almost instantaneously when the shield is correctly applied. After it is kept in this position for about one minute with a holder, it is left for another 5 without a holder. The shield is then detached from the Oxycel. The advantages of the method are that it is simple and requires only a short time to complete hemostasis without the necessity of temporary clipping and circumferential isolation of the artery. The method is applicable for defects in the lateral side of the arterial wall but not for those of the back side nor for large defects. Left: Conventional method of compressing cotton over Oxycel with a suction; compressing with even force is difficult, causing prolonged leakage of blood. Right: Metal shield method; there is almost no space of leakage between the arterial wall and Oxycel under the metal shield.

199

2 Sphenoidal Ridge Meningioma Case 84 Over Orbital Area (It)

This 56-year-old woman had gradually developed visual involvement and exophthalmos of the left eye over the preceeding 10 years. The left eye had recently become totally blind and ophthalmoplegic. Operation. A large left frontotemporal craniotomy was made. The tumor occupied mainly the left anterior temporal fossa and had spread into the chiasmatic cistern and around the left optic nerve and carotid artery. The portions around the optic nerve and carotid artery were easily removed because the adhesion was loose. The tumor was soft and very hemor-rhagic even though the external carotid artery had been obliterated prior to the operation. It had attached mainly to the floor of the anterior temporal fossa and further invaded the orbital roof over the sphenoidal ridge. After the attachment had been roughly dissected the tumor was removed step by step from the anterior portion toward the posterior. Its ventro-posterior portion had reached the left pons through the tentor-ial incision, attaching to the left trigeminal, trochlear and oculomotor nerves and left superior cerebellar artery. The oculomotor nerve ran in a sharp curve over the superior cerebellar artery but its distal contour disappeared. The medial portion of the tentorium had disappeared. After the main mass was dissected, the dura and bone of the temporal fossa, sphenoidal ridge and orbital roof, where the tumor had apparently in-

vaded, were extensively removed with a diamond drill. The whole course of the trigeminal nerve was visualized though about half of the nerve had been sacrificed. At the final stage during removal of the attachment brisk bleeding occurred, suspectedly from the extradural portion of the carotid artery. It was brought under control with Oxycel packing held in place by a tapered retractor. A very small portion of tumor tissue just around this site was left. The time from dural opening to closure was 3 h with 400 ml^lood-loss. The postoperative course was uneventful. The exophthalmos alone resolved.

201

1 Left superior cerebellar artery 2 Orbital fat 3 Dotted line: removed portion

Comments. The extensive radical removal of the attachment from the temporal fossa to the orbital roof was done in this case because the Icfl eye had been blind and ophthalmonoplegic for a long time. However, if the eye is not involved, the utmost care should be taken when working in the anteromedial corner of the tentorium (Parkinson's triangle) in which all the nerves relating to ocular movement arc hidden; leaving this small area untouched is often better for the patient than radical removal.

202

Sphenoidal Ridge Meningioma

Case 85 Anterior Temporal Fossa (rt)

This 48-year-old woman had experienced headache and slight left hemiparesis for about six months. Operation. A large right frontotemporal craniotomy was made; as much as possible of the Sphenoidal ridge was drilled off. The tumor was immediately found after wide opening of the Sylvian fissure. It occupied mainly the right anterior temporal fossa. Lateral retraction of the tumor with sacrifice of the Sylvian veins made it possible to reach the prechias-matic cistern through a very narrow space for the purpose of suctioning CSF. First, the attachment to the posterolateral portion of the sphenoidal ridge and anterior temporal fossa was dissected. After the anterolateral one third of the tumor had been removed the ventromedial portion was retracted laterally to identify the right carotid artery and the oculomotor nerve. These important structures had been shifted markedly to the medial side by the tumor. The posterior extent of the mass had reached the prepontine region. Removal of this portion was not difficult because the important structures such as the basilar artery and nerves were separated from the tumor by the thick Liliequist's membrane. After excision of the main mass, its dural attachment in the anterior temporal fossa was extensively removed. The three divisions, ganglion and root of the trigeminal nerve were clearly seen. The main procedure took two and a half hours with 400 ml blood-loss. The postoperative course w:as uneventful.

Comments. An important part of the procedure to remove a large meningioma is to identify the critical structures such as the optic and oculomotor nerves and the carotid and middle cerebral arteries as soon as possible. Their early identification prevents inadvertent injury and also facilitates quick removal of the tumor. When a critical structure has been identified it should be covered with a different kind of cotton sheet from usual to mark its location; for this purpose we use two kinds of cotton patty, Bemsheets and Codman's patties. It is our practice to use the operating microscope throughout the entire process of removal, so the surgeon's visual field is always very narrow. In such a situation marking a critical structure with a piece of cotton of a different color is very useful because it is usually located behind a large mass. One should remember that in the majority of huge meningiomas important structures are shifted to an unusual place, as in this case where the right carotid artery and oculomotor nerve had been pushed maximally to the medial side.

203

Basilar artery Area where tentorial attachment was removed

204

Sphenoidal Ridge Meningioma

Case 86 Huge Meningioma (rt)

This 12-year-old girl was suffering from mild neurological deficits : impairment of right vision (FC), slight exophthalmos, left homonymous hemianopia, and very mild left hemiparesis for the previous few months. Operation. Feeding arteries from the right external carotid artery had been embolized with Gelform during the selective angiography (Seldinger) before the operation. With the patient in the supine position and the right shoulder and head rotated to the left, a large frontotemporal craniotomy was performed. The temporal bone near the sphenoidal ridge was paper-thin. The tumor protruded on opening of the dura, to which it was not adherent. Its surface was not hard but was highly vascular. The main mass of the tumor, however, was so hard that it could only to be removed by sharp section. It was,

at first, cut with monopolar electrocautery with which more blood was lost than would have been the case with bipolar coagulation. In order to make a space for dissection of the attachment around the sphenoidal ridge, the anterodorsal portion of the tumor was partially removed, but each trial resulted in the loss of about 100 ml of blood because of high vascular-ity. The bleeding was mainly venous. Numerous large dilated veins were found inside the tumor; they were embedded Syl-vian veins. After sectioning of the attachment in the anterior temporal fossa, dissection of the tumor from the surrounding temporal and frontal lobes was easy because the adhesion to the brain was loose. It was difficult to visualize the carotid artery and optic nerve until two thirds of the tumor had been removed. The more it was removed,-the less was the bleeding.

продолжение

продол жение

205

1 Dissected portion at initial step 2 Dissected portion at next step

Although many big veins were still found inside it there were only a few arteries. The carotid artery and major branches of the middle cerebral artery were isolated from the tumor together with the arachnoid and were completely preserved, though they were all thin and had been shifted to an unusual location as the preoperative angiogram had shown. The meningioma had apparently developed on the lateral side of the sphenoidal ridge and mainly in the anterior groove of the temporal fossa. The dura of the attachment was removed and the surrounding portion around the attachment extensively coagulated. Although the preoperative CT scan suggested intraorbital invasion of the tumor, with the optic nerve being pushed medially (arrow in X-ray picture D), at surgery the whole of the orbital contents were found to have been thrust forward by a portion of the tumor through a bone defect in the sphenoidal wing. The orbit was not opened: we decided that if a residual tumor was found in the orbit on the postoper-active CT it would be removed by a second operation. The time from skin incision to closure was 5 h. Blood-loss was 1200 ml. The postoperative course: Hemianopsia, proptosis

and motor weakness disappeared and the impaired vision also improved. The right carotid angiogram taken two weeks later later Snowed the interesting finding of luxury perfusion around the right basal ganglia similar to the findings after removal of a large AVM (X-ray picture B). The angiogram four weeks iter showed that the middle cerebral artery had become al-most normal in size and course (X-ray picture C). Tbe postoperative CT scan revealed that the intraorbital mass shadow

and the shift of the optic nerve had disappeared; this suggested that the tumor had not directly invaded the orbit and had merely pushed the intraorbital contents through the bony defect (X-ray picture; see postop. CT). Comments. If the attachment to the sphenoidal ridge had been dissected earlier less blood would have been lost. Bipolar coagulation is far more useful than monopolar electrocautery in a highly vascular tumor. The laser would have had almost the same effect, as it is effective only for oozing; the bleeding in this case was not oozing but from embedded vessels. It is noteworthy that luxury perfusion may occur in the surrounding brain after removal of a huge vascular tumor such as the one in this case (X-ray picture B,C).

3 Intraventricular Meningioma Case 87 In Trigone (rt and It)

Case 87-1 (right). This 68-year-old man had developed hemihypesthesia two years earlier and moderate motor weakness of the left leg three months before the operation. On admission homonymous hemianopia, hemiparesis and hemihypesthesia were observed on the left side. Operation. With the patient in the lateral position, the head was elevated 30 degrees by inclining the operating table; the face was turned slightly downward so that the right parietal area came to the top of the operating field. A craniotomy of about 8 x 1 0 cm was made, and a linear cortical incision of 3 cm (the color figure). A hard tumor was found at a depth of about 1 cm from the cortex. Four tapered brain retractors each connected to a self-retaining retractor were applied around the cortical incision; two of them were simultaneously used for retraction according to the direction of approach while the others were loose. First, the posterodorsal one fifth of the tumor which had been located just under the cortico-tomy was removed. The space obtained by removal of this portion facilitated further dissection of the tumor surface from the surrounding brain tissue. The tumor was very hard but fortunately was not especially hemorrhagic. At this stage it was still impossible to see the attachment to the choroid plexus of the ventricle behind the tumor because of the size of the mass. The tumor was further reduced by piecemeal removal. After more than half had been resected the attachment to the choroid plexus in the trigone was seen by retracting the tumor with a hook: a couple of feeding and draining vessels were also seen. The attachment was coasulated and divided

at the choroid plexus, which had a normal appearance. Total removal of the tumor was accomplished through a 3 cm cortical incision. A large dead space was created in the brain. The time from dural opening to closure was 2 h with 300 ml blood-loss. The postoperative course was uneventful. The pre-operative homonymous hemianopia improved to a slight quadrantanopia. At the time of discharge a slight left hemiparesis remained. Comments. It was possible to remove the 6 x 7 cm mass through a 3 cm cortical incision as proper use of the four tapered spatulas provided a wide enough operating field. Whereas simultaneous retraction of the brain with all four retractors would give only a fixed space, retraction with one pair while the other pair was loosened created a space that could be shifted in all directions, resulting in a much wider subcortical operating space with only a small cortical incision. Case 87-2 (left). (Neither X-ray nor operative picture is shown). The 57-year-old woman had a relatively short history of mental deterioration and speech disturbance (slow speech and difficulty finding words) of two months' duration. In the two days before surgery symptoms of intracranial hypertension, vomiting, headache and mental disturbance had rapidly progressed. An emergency operation was performed. Operation. With the patient in the prone position, the head was rotated to the left. A craniotomy of 6 x 6 cm was made in the left parietal area. The gyri were completely flat and all the cortical vessels were small and slim. A cortical incision

207

1 Right lateral horn of the ventricle 2 Right posterior horn

of 3 cm was made. A hard and vascular tumor was found it a depth of 3 cm. A posterodorsal quarter of the mass was removed in order to obtain a space for further dissection around it. Posterior retraction of the remaining mass with a hook enabled us to visualize its attachment to the choroid plexus of the lateral ventricle. About two thirds of the feeding and draining vessels in the attachment were coagulated and cut: the rest were hidden behind the still large mass, which was therefore cut in the middle with scissors. When we pulled at the upper half, however, the whole of the tumor came out without resistance as the two halves were apparently still connected. At first only slight bleeding was seen in the bottom of the operating field, but after about 20 s massive pooling of blood appeared and the brain bulged markedly. The bleed-ing point was found in the subependymal layer of the posterior horn of the lateral ventricle; it was mainly venous. Hemostasis was is not difficult but the brain swelling remained unchanged, Although blood transfusion was only about 200 ml behind, the blood pressure was not measurable with a cuffmanomctcr for about 10 min, but the ECG showed no abnormality during this period; the cause of the low pressure was suspected to be the acute brain swelling. The gush of blood from the injured choroid plexus not only filled the ventricle but flew into the subdural space of the intcrhemisphere, temporal fossa and partly the contralateral hemisphere. If the injured vessels had bee:n located intraventricularly there would have been no trou-ble they were mainly in the subependymal brain. The craniotomy was enlaraed on closure and a laree Lvodura

patch was used to cover the swollen brain. The time from dural opening to closure was two and a half hours with 600 ml bloodloss. Postoperative course: Consciousness disturbance continued for two weeks, but gradually improved. Aphasia and right hemiparesis persisted. Comments. This was the only case in which we experienced intraoperativc acute brain swelling and one of two cases which became worse postoperatively in our series of 93 meningiomas. The mishap could have been avoided if we had been a little more careful at the final stage of the removal.

4 Parasagittal and Falx Meningioma Case 88 Anterior Parasagittal Sinus (Bilateral)

This 50-year-old man had suffered from continuous headache for more than two years. For the past three months he had experienced left hemiparesis, slight ataxia of both hands and blurred vision which was suspected to be due to papilloedema. Operation. With the patient in the supine position, the head with the chin down was raised above the heart level by inclining the operating table about 30 degrees. A large bilateral craniotomy was made without bleeding from the sagittal sinus which had been partially obliterated as seen on the angiogram. The brain was slack and the tumor did not protrude. Both sides of the sagittal sinus were ligated and divided. The tumor was soft and non-hemorrhagic, and was easily removed with a large suction of 4 mm in diameter. Rather than the midportion of the falx having disappeared inside the tumor, the meningioma had in fact grown inside the falx because the outer- layers of the falx were found to cover the mass bilaterally. After the upper three quarters had been re-

moved the bottom of the tumor was mobilized to identify the anterior cerebral arteries. These were strongly adherent to the bottom of the tumor, and they were isolated from it very carefully; it was the only stage of the operation where great delicacy was called for. Pieces of the remaining edges of the sagittal sinus were studied histologically by frozen section; no tumor cells were demonstrated. The main procedure took an hour and a half with 300 ml blood-loss. The postoperative course was uneventful. All preoperative deficits disappeared within one week. Comments. (1) Although the preoperative CT scan showed a large tumor, the operation was very simple except for the adhesion to the anterior cerebral arteries, because the meningioma was soft and avascular. Generally, removal of a meningioma is easy when no low density area around the mass is found on the CT scan because adhesion to the surrounding structures is loose without involvement of the vessels on the

209

Left anterior cerebral artery Superior sagittal sinus Left frontal lobe

surface of the tumor. (2) A large suction of 4 or 5 mm in diameter is very useful in removing a tumor. The sucking power of the large suction is almost the same as the expensive ultrasound suction; one disadvantage is that it moves the surrounding tissue while suctioning, but it is simple and available in every operating theater. Such a large tube should not be used in regions close to critical structures because its power is so great, and it is also recommended that it be held in the surgeon's dominant hand for better control.

210

Parasagittal and Falx Meningioma

Case 89 Unilateral Falx (rt)

This 56-year-old school teacher had noticed slight paresthesia in the left side 6 months earlier and left motor weakness 3 months earlier; the symptoms were progressive. She had developed left homonymous hemianopsia, left hemiparesis and amnesia one month earlier, and incontinence and clouding of consciousness appeared three days before the operation. The day before surgery angiography and CT scan were performed ; she was transfered from the neurological department and underwent an emergency operation. Operation. With the patient in the prone position, the head was elevated with the chin up, so that the operative microscope could be applied perpendicularly to the operating field. A unilateral right craniotomy was made in the right medial parietal area. The medial bone edge of the craniotomy was cut just off the midline and sharply beveled over the sagittal sinus. Then the inner beveled edge was removed with a ron-geur far enough to visualize the sagittal sinus without any blood loss. The brain was tight and bulging. Two big cortical veins bridging to the sagittal sinus were isolated from the cortex by cutting the arachnoid covering of the veins. One small cortical vein between the two large ones was sacrificed. Isolation of the big veins for about 2 or 3 cm facilitated retraction of the brain. The attachment of the meningioma to the falx was found with minimal retraction of the medial parietal

lobe between these veins. In addition to the high vascularity of the tumor and the attachment, the brain was bulging, so a medial portion of the parietal lobe above the tumor was removed; this made it easy to dissect the attachment from the falx. At the beginning every step of the dissection of the attachment was accompanied by considerable hemorrhage like a direct attack on the nidus of an AVM; the vessels inside and outside the tumor were so pathological that they could not be coagulated with the bipolar coagulator. The bleeding was controlled by covering with Oxycel and cotton patties. While a bleeding point thus controlled was pushed to the falx side with a tapered retractor, another part was dissected; in this way the whole attachment to the falx was sectioned. Total detachment of the tumor bed from the falx changed the hemorrhagic nature of the tumor, and it could be removed with a suction without excessive blood loss. The lateral body of the ventricle was opened widely as in the case of ventricular meningioma. The falx around the attachment was extensively removed; many arteries in the cut edge of the falx coagulated easily, very different from the problems we had controlling bleeding from the vessels inside the tumor. The dura was easily closed. The total operating time was 6 h with 1800 ml bloodloss. The postoperative course was uneventful. The preoperative neurological deficits disappeared except for quadrantanopia.

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Superior sagittal sinus Falx Right occipital lobe Dotted line: Tumor

Comments. This is one of the few cases where more than 1000 ml of blood had to be transfused. There were several reasons for this: it was an emergency operation where the patient had rapidly developed intracranial hypertension; the patient's head was not high enough to decrease the venous pressure; the tumor bed was not detached from the falx at the initial stage because the operation was one of the earlier cases in our series. When the attachment is to the falx, the tumor should be isolated from the normal falx close to the attachment where bleeding control is easy in a highly vascular meningioma. whereas when the tumor is attached to the bone dissection is done close to the attachment.

212

Parasagittal and Falx Meningioma

Case 90 Bilateral Falx (rt)

This 48-year-old woman complained of mild headache and dizziness for several months without neurological deficits. Operation, With the patient prone, the head was fixed in the chin-up position and was elevated 30 degrees by inclining the operating table. A unilateral craniotomy of 5 x 4 cm was made in the right medial parietal area. One large vein, located in the frontal margin of the operative field, was isolated from the cortex by cutting the covering arachnoid; the isolation facilitated its preservation throughout the procedure. One small vein running in the center of the field was sacrificed. The tumor was found 1 cm under the cortex. Its attachment to the falx was found with minimal retraction of the medial parietal lobe. The sagittal sinus had not been involved by the tumor. A thin portion of the medial parietal cortex of about 2 x 3 x 1 cm was then removed. This made it easy to separate the tumor in the right hemisphere from the falx attachment. First the falx around the attachment was extensively coagulated, and then the attachment itself was dissected (lower picture: Step 1, 2). The mass, which had been hemor-rhagic in the beginning, became obedient after isolation of the right side from the falx. The medial portion of the tumor in the right hemisphere was dissected in a wedge shape (Step 3). Then the remaining lateral portion which had been

hidden under the cortex was pulled medially with a hook and dissected; it was removed with minimal brain retraction. This procedure was repeated until the whole mass under the cortex in the 'right hemisphere had been removed (Step 4, 5). Next the mass in the left hemisphere, which had been almost separated from the falx, was removed through the large dead space created in the right hemisphere; its removal was very easily accomplished within 20 min without any damage to the cortex (Step 6). In the bottom of the operating field the tumor extended close to the straight sinus and vein of Galen. Bleeding from the sinus was encountered once but it was well controlled with Oxycel packing. The tumor was radically removed. The time from dural opening to closure was three and a half hours with 200 ml blood-loss (during craniotomy 300 ml of blood was lost). The postoperative course was uneventful. Comments. When the sagittal sinus is not involved a unilateral craniotomy is adequate to remove a bilateral falx meningioma. The craniotomy should not extend over the sinus but only close to it, with beveled cutting of the medial bone edge. When necessary the edge may be additionally removed as far as or just past the side, of the sinus, but removal of the bone above the sinus neveKwidens the operating field and often causes strong bleeding.

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5 Tentorial and Posterior Fossa Meningioma

General Considerations for Posterior Skull Base Meningiomas In the present era of the CT scan tentorial and posterior fossa meningiomas are found more often than in the past: the neurological deficits they produce are usually milder than those prior to the CT era because of earlier detection. As with other tumors, the technical difficulty of their removal depends on their size and location. Removal of such meningiomas in cases with minimal neurological deficits is generally easier than in those with severe deficits, though we have to worry more about additional deficits postoperatively when patients have fewer neurological deficits preoperatively. In the literature prior to the era of the operating microscope the operative results of tentorial and posterior fossa meningiomas were unsatisfactory. Even under the microscope it is still true that surgery for these meningiomas is one of the most difficult procedures. /. Classification of Posterior Skull Base Meningiomas. It is necessary to classify meningiomas in and around the tcntorium and in the posterior fossa further according to their dural attachments. One of the things that enables a more detailed classification to be made is that the preoperative detection of attachments has become possible in the era of the CT scan, though not in all cases. Another important development is that selection of the most adequate approach from among the subtemporal, occipital, suboccipital and combined routes can be decided according to the location of the dural attachment and the main area occupied by the mass. 1 Medial tentorial meningioma. Subdivisions: anterior, middle and posterior 2 Lateral tentorial meningioma. Subdivisions: anterior, middle and posterior 3 Falcotentorial (parastraight sinus) meningioma. 4 Paraconfluence sinus meningioma. 5 Paratransverse sinus meningioma. 6 Clival meningioma. 7 Clivopyramidal meningioma. 8 Clivopyramidotentorial meningioma. 10 Pyramidal (parasigmoid sinus) meningioma. 11 Cerebellar (surface) meningioma. 12 Foramen magnum meningioma. This classification indicates the location of the attachment as well as of the mass. The traditional term, cerebellopontine angle meningiomas, for example, is too broad. Three dural portions of the tentorium, clivus and pyramid surround the space of the cerebellopontine angle. Combinations of these three attachments give 7 divisions, 1 to 2 and 6 to 10 in the above classification, instead of just the one name cerebellopontine angle meningioma. II. Selection of Subtemporal or Suboccipital Approach. Although some neurosurgeons approach all meningiomas in the posterior fossa by a suboccipital route I have operated on meningiomas located close to the upper medial portion of the posterior fossa (around the upper clivus) with a subtem-

poral approach more easily than with a suboccipital. A subtemporal approach to meningiomas around the upper clivus generally provides a wider operating field than a suboccipital; obstructions in the former are the IIIth, IVth and Vth nerves and in the latter the Vllth and VIIIth nerves. 1. Subtemporal approach: 1 Medial tentorial meningioma. 2 Lateral tentorial meningioma. 3 Meningioma of upper portions of the clival, clivopyramidal, medial pyramidotentorial and clivopyramidotentorial areas. 2. Occipital approach (interhemispheric or supratentorial): 4 Posterior tentorial meningioma (supratentorial portion). 5 Falcotentorial (parastraight sinus) meningioma. 6 Paraconfluence sinus meningioma (supratentorial portion). 7 Paratransverse sinus meningioma (supratentorial portion). 3. Suboccipital approach (lateral or middle): 8 Meningioma of lower portions of clival, clivopyramidal and lateral pyramidotentorial areas. 9 Pyramidal (parasigmoid sinus) meningioma. 10 Lateral tentorial (paratransverse sinus) meningioma (in-^ fratentorial portion). 11 Cerebellar (surface) meningioma. 12 Foramen magnum meningioma. ///. Subtemporal Approach for Meningiomas of Tentorial and Upper Clivopyramidal Portions. Ideal positioning of the patient's head and drainage of CSF are very important as in the usual subtemporal approach. As a rule the bone of the lateral side should be removed as much as possible; the degree of temporal lobe retraction required is inversely proportional to the extent of lateral bone edge removal. The craniotomy ; should be made in such a way that the horizontal length along ' the skull base is longer than the height; the lateral width in the subtemporal space facilitates the operative procedure. On the other hand, the width between the tentorium and sub-temporal surface is limited by the temporal lobe retraction. The temporal lobe should be retracted as gently as possible, especially in an elderly patient where the brain tolerates retraction poorly. 1. A meningioma in the anterior tentorium (infratentorial type) is approached through the anterior subtemporal and transsylvian routes combined (Case 91). The tumor is usually easily removable when it is located only on the dorsal surface of the dura (such supratentorial cases as Nos. 84, 85 and 86). The greatest difficulty in this area is encountered when the mass has invaded with strong adhesion under the anteromedial portion of the tentorium where the oculomotor, trochlear and abducens nerves run. Radical removal of this portion often results in ophthalmoplegia, and there is\herefore a problem when no oculomotor paresis is present\ preoperatively (Fig. V-l arrow 1 and 2).

215

Fig. V-3

2. A meningioma in the middle tentorium and clivopyramidal area (the medial side of the middle tentorium) is one of the most difficult benign tumors to deal with. Most of the mcningiomas in this region attach to both the medial side of the tentorium and the upper portion of the clivus and pyramid. When the tumor is found close to the upper clivus and/or the upper medial pyramid on the CT scan a subtemporal approach should be taken (Cases 92 to 95). Contrarily a mass located in the lateral side of the Vllth and Vlllth nerves should be approached through a lateral suboccipital route or combined routes (Cases 100 and 94). As the meningohypo-physial and marginal tentorial arteries (Bernasconi Cassinari) feed all tumors in this region dissection of the tumor should •v started from the anterior portion in order to cut the feeding artery and to decrease bleeding from the tumor in the following stage. A difficult procedure is the removal of the infraten-_ша! portion (clivus and pyramid) when it has spread wide and deep. To obtain a more adequate exposure it is occasionally helpful to drill off the upper edge of the petrous bone (color figure in Case 93) and a combination of the supra-..nd infratentorial routes is also useful (Case 94). Sometimes ;he tumor completely surrounds some of the cranial nerves. When a nerve is not identified, a sharp dissector for sectioning the tumor should be used only along its suspected course. not across it. A troublesome problem is thai critical arteries

such as the basilar, anterior inferior ccrcbellar and pontine perforating arteries are embedded; radical removal should be abandoned when adhesion is too strong. The mass presses strongly against the peduncle and pons, which are, however, often separated from the tumor by a relatively thick arachnoid, making dissection in this region rather easy. 3. A meningioma in the lateral side of the posterior tentorium is usually easier than one in the medial. Care should be taken in handling the transverse and straight sinuses and the sinus confluence. IV. Suboccipital Approach for Posterior Fossa Meningiomas. Removal of meningiomas located around the lower medial portion of the clivopyramidal bone and the foramen magnum is also extremely difficult when the mass is hard and critical structures are embedded. The surgical technique for such tumors is basically the same as that for acoustic neurinomas except that meningiomas have a stronger tendency to entrap the nerves and arteries than do neurinomas. A mass located in the lateral side of the pyramidal bone and the eerebellar surface is, however, easily removed. The supracerebellar infratentorial area is one of the locations in the posterior fossa with a high incidence. We prefer the Concorde position for the approach to meningioma here (see Case 73).

216

Tentorial and Posterior Fossa Meningioma

Case 91 Anterior Tentorium (It)

Case 91-1 (left). This 35-year-old man had noticed hypesthesia in the left face for the previous few months without other deficits. Operation. With the patient in the supine position the right shoulder was elevated and the patient's head rotated more than 45 degrees to the left so as to make possible both transsyl-vian and subtemporal approaches. A large left frontotemporal skin incision was made. First a transsylvian approach was performed, exposing the left optic nerve and carotid artery, which had been displaced by the tumor. The oculomotor nerve was partially embedded in the mass, which seemed rather soft, somewhat like a neurinoma, without a capsule. After identification of these important structures, the anteromedial portion of the tumor was removed; isolation of the third nerve was very difficult. As much of the tumor as possible was removed through this operating field. A middle subtemporal approach was taken next. The posteromedial portion of the tumor was found under the medial tentorial edge. The trochlear nerve was sought without success. Then the tentorium was incised along its surface, first at some distance from the tentorial edge and then toward the edge. The incision caused considerable oozing, but this was controlled by repeated coagulation with bipolar cautery. The trochlear nerve was eventually iden-

tified running over the tumor under the tentorium. The trigeminal nerve was found defining the posterolateral border of the tumor. The abducens nerve was not seen. Great difficulty was anticipated when dissecting the tumor under the trochlear nerve. We started the dissection between the oculomotor and trochlear nerves. The apparent attachment of the tumor to the posterior clinoid process, the posteromedial wall of the left pyramid and the lateral side of the upper clivus was carefully dissected with the bipolar coagulator. Numerous fibrous feeding arteries from the attachment to the tumor were encountered here. When the tumor was detached from its bed it became soft and much less hemorrhagic. It was further resected by suction and bipolar cautery. The medial surface was well demarcated, which made it easy to remove this portion piecemeal. The basilar and left superior cerebellar arteries, as well as the Ilird, IVth and Vth nerves, were all visualized. The tumor bed was coagulated as much as possible. Any attempt at radical excision of the residual tumor was abandoned, because the IVth, Vth, Vlth and, partially, Ilird nerves had been involved in the region of the attachment. More than 90% of the tumor was removed, which meant that the tumor would not be seen on the postoperative CT scan. The time from dural opening to closure was three and

217

a half hours with 400 ml blood-loss. Postoperative course: the facial hypesthesia disappeared but left hearing involvement of about 60 dB was present and it persisted; its exact cause was unclear, but it was possibly due to excessive coagulation of the pyramidal bone. Comments. Although total removal would have been possible a residual tumor was left around the ocular nerves for fear of postoperative diplopia; the patient had been working as a schoolteacher until one week before the operation without any severe deficits. We planned a second operation if a follow-

up CT scan showed recurrence of the tumor or if neurological deficits appeared. The approach using both transsylvian and subtemporal routes was very useful; although most of the task was done via the subtemporal approach, the initial transsylvian exposure facilitated identification and isolation of the carotid artery and oculomotor nerve and also the preservation of the Sylvian bridging veins.

Case 91 cont'd on p. 218

218

Tentorial and Posterior Fossa Meningioma

Case 91 cont'd

Case 91-2 (right). (Shown only by X-ray pictures on p. 216). This 72-year-old woman had suffered from headache for 6 years. Neurological findings were slight ataxia and mild diplopia due to right abducens nerve palsy. Operation. With the patient in the lateral position a large right frontotemporal craniotomy was made to enable both transsylvian and subtemporal approaches. First, after the patient's head had been positioned upwards by tilting the operating table and rotating the head frame, the prechiasmatic cistern was reached via a transsylvian route. Suctioning of CSF produced a beautifully slack brain. The subsequent procedure was much the same as in the previous case. The difference was in the size of the tumor. About 30% of the mass

had to be left because it had spread deeply to the midline and its adhesion to the basilar and branching arteries was very strong. Postoperative course: For about two weeks the patient's neurological and physical condition was poor, but she gradually improved. Two months later she was discharged in much the same condition as before the operation, but with the additional deficit of a slight left hemiparesis. Comments. This is the case with the largest residual portion in our meningioma series. Macroscopic portions were left in 3 cases out of 25 tentorial meningiomas. We had anticipated preoperatively that only partial removal or just decompression would be done in this case because of the patient's age. As it turned out, the postoperative course was a little troublesome even though the removal had been only partial.

Case 92 Medial Tentorium and Clivus: Involvement of Vth Nerve (rt)

This 50-year-old woman underwent subtotal removal of a meningioma through a right suboccipital craniectomy at another hospital 8 years earlier. At that time the right facial nerve was anastomosed with the hypoglossal nerve. Recently she started to complain of headache without neurological deficits. Operation. With the patient in the lateral position a large Jshaped skin incision was made from the lateral suboccipital area to the posterior zygomatic arch in preparation for a suboccipital approach if necessary. A craniotomy was made only in the middle temporal area. Preservation of the veins of Labbe was effected throughout the procedure by removing the arachnoid and a small portion of the cortex around them. Retraction of the middle subtemporal lobe enabled us to identify a small convex meningioma supratentorially. The tumor

was red and highly vascular but was soft enough to remove by suction. After the trochlear nerve had been identified the tentorium was opened from the tentorial edge posterior to its dural entrance. The main tumor mass was located infratentorially with attachment to the pyramidal and clival bone. The superior cerebellar and posterior cerebral arteries were seen by lateral retraction of the tumor with a hook. However, the trigeminal nerve was not found at this stage. The upper portion of the tumor was very carefully cut along the suspected course of the trigeminal nerve as shown in the upper color figure. The nerve was completely embedded in the tumor but was successfully isolated from it. The tumor was easily dissected in the medial, posterior and lateral sides, but dissection of the anterior portion was rather difficult as the tumor had invaded the anterior tentorium and upper portion of the

219

pyramid close to the dural entrance of the trochlear nerve, Meckel's cave and the meatus. ЛИ the critical structures such as the cranial nerves from the TTIrd to the VTTTth and the basilar artery were well isolated from the tumor. Some pieces were left around the internal meatus because the tumor was strongly attached to the acoustic nerve and radical removal from it seemed likely to cause deafness. The time from skin to skin was five and a half hours with 300 ml blood-loss. Postoperative course; The patient was talkative on the first night. On the following day she developed generalized convulsions. The CT scan showed a small high-density area in the right temporal lobe. Euphoria, talkativeness and slight diplo-pia due to trochlear nerve paresis continued for a week. Two weeks later she recovered fully without deficits. Comment. The sectioning of the tumor mass along the course of the trigeminal nerve hidden in it was essential to isolale the nerve without damage. If the mass had been cut across the direction of the nerve at least half of the bundles would have been sacrificed. It is noteworthy that a meningioma may include cranial nerves while a neurinoma only displaces them while growing. Leaving a small amount of tumor around the acoustic meatus was probably the best course; normal hearing acuity wras maintained after the operation and the speed of growth of this tumor was suspected to be slow because the interval between the first partial removal and this second operation was 8 years.

1 Right superior cercbellar artery

2 Basilar artery

3 Pons pushed by tumor

4 Right cerebellum 5 Vein Labbe

6 Tumor attachment

220

Tentorial and Posterior Fossa Meningioma

Case 93 Medial Tentorium and Clivus: Drilling off Pyramid (rt)

This 61-year-old woman had suffered right hearing disturbance for 7 years and right facial pain for 6 months. Her neurological deficits were right corneal hyporeflexia, right deafness, slight ataxia and weak gag reflex. Operation. With the patient in the lateral position a skin incision was made from over the transverse sinus to the posterior zygomatic arch after spinal drainage had been instituted. A craniotomy was made only in the middle subtemporal area. The brain was nicely slack due to the draining of CSF. The middle portion of the inferior temporal lobe was gently retracted. Small pieces of the tumor were visible on the upper surface of the tentorium and a small portion of it was found protruding medially from the tentorial edge. The trochlear nerve was found on the tumor surface. The tentorium was easily cut. The tumor was attached partially to the tentorium and widely to the pyramid and clivus, invading Meckel's cave and spreading over the meatus. The trigeminal nerve identified under the tumor had been compressed flat by it. Meckel's cave had been markedly enlarged by the invasion. The most difficult part of the whole procedure was the dissection of the tumor from the acoustic and facial nerves around the meatus. This area was the deepest in the subtemporal approach and was hidden by the petrosal bone and lateral tentorium including the transverse sinus. The upper edge of the

petrosal bone was drilled off to give a wider operating field. After removal of the tumor the flattened trigeminal and abducens nerves and the basilar artery were seen in the bottom of the field; the-'lateral side of the pons was markedly concave due to compression by the tumor and numerous dilated veins were found on the surface. The time from dural opening to closure was three and a half hours with 200 ml blood-loss. Postoperative course: Right abducens palsy and anesthesia in the right face appeared. The abducens palsy was transient, while paresthesia in the area of the first division of the trigeminal nerve continued for one year. Comments. Removal of the upper edge of the pyramid is often very useful to obtain a wider operating field for approaching deeper into the prepontine area not only for a tumor here but also for basilar trunk aneurysms. Another approach to this area is made by removing the petrosal bone epidurally through the subtemporal space. I find that removal of the upper corner of the pyramid is easier subdurally by a subtemporal approach than by an epidural petrosal approach. We have found tortuous dilated veins on the pontine and medullary surface in five cases with giant aneurysm. neu-rinoma and meningioma. We suspect that long-standing compression of the surface veins by a hard mass causes the development of a collateral network of such tortuous dilated veins.

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Meckel's cave Basilar artery Risht cerebellum

222

Tentorial and Posterior Fossa Meningioma

Case 94 Medial Tentorium: Combined with Suboccipital Approaches (rt)

This 13-year-old boy had complained of persistent headache without other deficits for half a year. 1st Operation. With the patient in the lateral position, a large J-shaped skin incision was made from the lateral Suboccipital area to the posterior zygomatic arch. A right temporal craniotomy was made slightly posteriorly. A subtemporal approach was performed, preserving the veins of Labbe. Hypervascularity was found on the tentorial surface. The tentorium was sectioned in a U-shape from the edge posterior to the dural entrance of the trochlear nerve. The tumor was attached to the center of the infratentorial side of the dissected tentorium; it was very hemorrhagic. It was removed as far as it could be visualized by the subtemporal approach. About a half of the mass was removed in this way. 2nd Operation. Ten days later a right lateral Suboccipital approach was performed using the previous skin incision. Retraction of the superior lateral cerebellum facilitated visualization of the tumor. First, the facial and acoustic nerves were isolated from the tumor. Then, by retracting the tumor with a hook the normal subtemporal cortex could be seen through the tentorial window which had been opened by the removal of the tentorial attachment in the previous operation. The tumor was not hemorrhagic, very different from the hypervas-cularity at the first operation because the feeding arteries (marginal tentorial artery, Bernasconi Cassinari artery, arrow in the X-ray picture) in the attachment had been dissected.

It was easily removed. The postoperative course was uneventful. Sixteen months later, however, the boy developed headache again. The CT scan showed recurrence of the tumor; it was larger than before. 3rd Operation. In the lateral position an approach from the subtemporal and Suboccipital routes was made through the previous craniotomy and craniectomy. A large tumor was found at almost the same site as before. Curiously, it had no dural attachment. Total removal was easy. The postoperative course was uneventful, and the patient has made a full recovery. Comments. (1) This was the first case in our series of dissemination after removal of a benign meningioma. The recurrence was quite unexpected. It is suspected that a small piece of the meningioma was disseminated in the brain in the initial operations and grew over the 16 months. In the four-year follow-up since the third operation no signs of recurrence have been observed either radiologically or neurologically. (2) A two-stage operation first via the subtemporal and then via the lateral Suboccipital route is a useful tactic when a tumor is too large or the patient's condition is poor. The meningioma in this case could have been removed by only the subtemporal approach or by a single operation using both approaches, but the time required would have been excessive. Each procedure in the present case was accomplished in less than 4 h with less than 400 ml blood-loss.

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1 Right transverse sinus

2 Right sigmoid sinus 3 Right vein of Labbe 4 Right cerebellum 5 Pons 6 Tentorium

7 Right superior cerebellar artery

224

Tentorial and Posterior Fossa Meningioma

Case 95 Large Medial Tentorium: Sacrifice of Posterior Choroidal Artery (It)

This 67-year-old woman had developed headache, bradykine-sia and occasional urinary incontinence which were treated as Parkinsonism by an internist for 6 months. Removal of the tumor was carried out following a ventriculoperitoneal shunt operation which improved the incontinence. Operation. With the patient in the lateral position a left subtemporal approach was made. During craniotomy, a drill bar broke and its tip injured the transverse sinus, from which massive bleeding occurred. About 300 ml of blood had been lost before the bleeding was controlled by Oxycel and reflexion

of the adjacent portion of the dura. As the brain was extremely tight despite the preliminary ventriculoperitoneal shunt, a small posterolateral temporal portion of the temporal lobe above the tumor was removed. The tumor was found about 2 cm under the cortex. Sucking of CSF from the anterior crural cistern slackened the brain, and a wide operating field was obtained with minimal temporal retraction. The tumor was located on both sides of the tentorium. The supratentorial portion was soft and nonvascular, in sharp contrast to the hard infratentorial portion. After rough removal of the supratentorial mass the tentorium was dissected around the attachment, which reduced the bleeding from the tumor. The most difficult procedure was the separation of the trochlear nerve, the superior cerebellar, posterior cerebral and their branching arteries from the tumor; adhesion was so strong that about a quarter of the total operative time was spent on their isolation. The bottom portion of the tumor also attached strongly to the cerebellum and pons. Dissection from the cerebellum was far more difficult than that from the pons because the latter was covered with a thicker arachnoid than the cerebellum. The distal posterior cerebral artery was dissected from the tumor in order to remove the posteromedial portion. At this stage one recurrent branch of the distal posterior cerebral artery was sacrificed because it was mistakenly considered

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1 Basilar artery 2 Left posterior cerebral artery 3 Left posterior choroidal artery

4 Left superior cerebellar artery 5 Left cerebellum

to be a feeder of the tumor; it was perhaps the posterior choroidal artery (arrow). Total time was 8 h with 600 ml blood-loss. Postoperative course: Semi-coma and right hemiplegia continued for two weeks, and right hemiparesis and moderate aphasia remained thereafter. Comments. The cause of the postoperative deficits was probably the sacrifice of the left posterior choroidal artery. It is important to remember that, ordinarily, all mcningiomas have their feeding arteries from the dural attachment and never have important feeders from intracerebral arteries other than very small ones. We should never assume arteries in and around the mcningioma to be feeders unless they are in the attachment; if they only pass through the mass they should not be sacrified if they are significant.

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Tentorial and Posterior Fossa Meningioma

Case 96 Bilateral Occipital Lobes: Visual Cortex (rt)

Case 96-1. This 36-year-old woman had complained of headache and shoulder stiffness for 6 years without neurological deficits. Her visual field and acuity were completely normal. Operation. With the patient in the prone position a large Ushaped skin flap was made over the bilateral occipital and suboccipital regions after a ventricular drainage had been instituted in the right anterior ventricle. A right unilateral occipital craniotomy of 5 x 5 cm and bilateral suboccipital craniectomy were performed, removing the bone over the right transverse sinus. The tumor was found about 2 cm under the right medial occipital cortex. Except for its surface, the main mass, about 80% of the tumor, was so solid that it could only be removed with scissors. In order to protect the visual cortex which had been strongly compressed laterally the medial portion of the tumor was first removed in a wedge shape (see Case 90). The space thus created enabled the body of the tumor to be isolated from its attachment to the falx without retraction of either the tumor or the occipital lobe. After the medial portion had been removed the lateral side was very gently retracted medially with a hook. Meticulous attention was paid to separating the tumor from the visual cortex. Isolation was successful without any apparent injury except for the sacrifice of some veins running over the cortex. Next,

removal of the remaining portion in the left hemisphere was begun. Fortunately the adhesion of the tumor to the left visual cortex was loose, so dissection was easy. After a large dead space had been obtained by removal of the main mass in the bilateral occipital lobes, the attachment around the straight sinus and the posterior tentorium was removed without difficulty because the straight sinus had been obliterated through invasion of the tumor, as suspected from the angio-gram. At the anteromedial edge of the falx some difficulty was encountered when isolating the dilated internal cerebral and basal veins, but they were successfully preserved. Finally | the infratentorial portion of the tumor was attacked. The caudal portion was first dissected from the cerebellum. However, when removal of the superior portion close to the tentorium was attempted, it was impossible to visualize the region because the patient was prone with the head considerably elevated for the procedure in the occipital lobe. The operating chair was therefore moved from in front of the patient's head to beside her left shoulder, from which position the following procedures could be done easily and quickly. The tumor attachment in the falx and tentorium was grossly removed; some tissue probably remained close to the confluens because radical attack was avoided here. The time from skin to skin was

1 Confluence 2 Right transverse sinus 3 Talx

4 Right tentorium 5 Right occipital lobe

6 Left occipital lobe

7 Right cerebellum 8 Left cerebellum 9 Vein of Galen

8h with 700ml blood-loss. Postoperative course: Through the first postoperative night she complained of total blindness, which then gradually improved. For the following week she suffered from visual hallucination such as an oscillating pattern composed of lines and stars. Two weeks later her visual acuity became normal with slight left homonymous hemiano-pia. Three weeks later the visual fields were normal. Comments. This mcningioma is called a parastraight sinus mcningioma in our classification. In order to preserve visual function we paid the most meticulous attention to dissection at the visual cortex, and were fortunately successful. Case 96-2 (only X-ray pictures are shown): We operated on a similar patient who had complained of left homonymous hemianopia for one year caused by a meningioma of the falx and straight sinus compressing the right visual cortex. During the operation the visual cortex was found to have been softened and flattened by tumor compression over a long period; it seemed absolutely impossible that the visual field deficits could improve. Suprisingly. however, there was some postoperative improvement.

228

Tentorial and Posterior Fossa Meningioma

Case 97 Posterior Tentorium (rt)

This 58-year-old woman had had slight headache for one year and mild cerebellar ataxia for three months. Operation. With the patient in the prone position the head was moderately elevated and the neck flexed, probably to an excessive degree. A right unilateral U-shaped skin flap and large craniotomy were made over the right occipital and suboccipital areas. The craniotomy was troublesome due to continuous bleeding from the bone edge. After dural opening, ventricular drainage was instituted in the right posterior ventricle. Drainage of CSF facilitated a supratentorial approach to the supratentorial portion of the tumor with minimal occipital retraction. The tentorium was convex but only a small portion of the tumor was bulging out through it. With this approach as much as possible of the tumor around the tentorium was removed. The transverse sinus was also removed; it had been almost completely obliterated. The procedure in this region was easy because the operating field was very wide compared to an infratentorial approach. However, the venous bleeding from the bridging veins, dura and bone surrounding the tumor was as intense as arterial bleeding. I had never experienced this before in usual suboccipital operations; I suspect that it was caused by excessive flexion of the patient's neck or by obliteration of the sinus by tumor infiltration. The latter explanation seems highly likely from the findings of the arteriogram. in which the right transverse sinus was absent and the left one was also narrow. The bleeding de-

creased as more of the tumor was removed. At the final stage, however, massive bleeding was encountered from the confluence when the dura was sectioned close to it. It was controlled with Oxycel and an aneurysm clip which was removed after hemostasis was achieved. Some tumor tissue was probably left around here though the portion had been extensively coagulated. The total time was 8 h with 800 ml blood-loss. The postoperative course was uneventful. Comment. (1) Two points prolonged this operation and caused a large amount of blood-loss: one was the incorrect position of the patient and the other was the smallness of the bone opening. The incorrect position caused an increase in venous bleeding, which was difficult to control and made us hesitate to remove the bone further. If the bone over the confluence and the left side of the suboccipital area had bee^n more widely removed, the operation would have proceeded more smoothly and quickly. Adequate removal of the bone around the confluens and transverse sinus is an important procedure for the removal of a large meningioma via the combined supra- and infratentorial approaches. (2) Tumor infil- ; tration around or into the confluence or the posterior half of the sagittal sinus is the most complicated problem. Successful reconstruction of the sinuses has been reported, but this is something I have never done.

An Accident with a Tentorial Meningioma This 52-year-old woman had suffered left(!) facial pain and hypesthesia of the left(!) trigeminal area with advanced bilateral papilloedema. With the patient in the Concorde position a large occipital U-shaped skin flap was made, and a right occipital craniotomy and bilateral suboccipital craniectomy performed. The tumor was very soft and easily removed with a suction. Its location was almost the same as that of case 92. After intracapsular decompression of the infratentorial portion of the tumor, the surface was dissected from the cerebellum and this portion totally removed. The dura of the occipital pole was then opened and the supratentorial portion was removed. It was not located in the interhemispheric area

229

1 Superior sagittal sinus

2 3 4 5

Right transverse sinus Right tentorium Right occipital lobe Right cerebellum

but in the suboccipital. After the main mass had been removed from both sides of the right tentorium the attachment to the latter was removed as far as the straight sinus, which had been invaded by the tumor. In the depths along this near the vein of Galen, strong venous bleeding was encountered; it was controlled with Oxycel packing. A very small amount of tumor tissue probably remained around the sinus. While the dura was being closed, cardiac arrest occurred immediately after the transient increase of venous pressure induced by compression of the respiratory bag to check for insufficient control of venous bleeding. The patient was at once turned from the prone position to the supine and cardiac resuscitation was tried for more than 10 min; the hypotension continued for more than one hour. The patient was returned to the prone position. Venous oozing was encountered in the whole operating field where it had previously been completely controlled. The bleeding was relieved slightly by a heparin injection as a treatment for D1C. The patient died three days later.

Comments. This was one of the three deaths among the 93 cases in our meningioma series. The cause was suspected to be air emboli, although no exact signs were observed prior to the accident; the anestheologist had frequently checked the arterial CO2 content, cardiac murmur and ECG. The mistake on the part of the surgeon was that the patient was positioned at an unusually steep inclination of about 45 degrees in the prone position and we were not concerned about the possibility of air emboli because we had not previously experienced such a complication in the prone position.

230

Tentorial and Posterior Fossa Meningioma

Case 98 Posterior Tentorium (It)

This 64-year-old woman complained of headache and tinnitus for one year. Operation. With the patient in the Concorde position (see Case 73) a U-shaped suboccipital skin incision and bilateral suboccipital craniectomy were made. The tumor was found superficially between the left transverse sinus and cerebellum. The inferior vermian veins were isolated from the cerebellum by cutting the arachnoid and removing a small portion of the cortex around the veins. The veins were preserved throughout the operation. The central portion of the meningioma was sucked with a big suction, 4 mm in diameter. The decompression facilitated dissecting the tumor from the cerebellum not by cerebellar retraction but by mobilizing of the tumor "witrra~hook. After gross removal of the main mass, the tentor-ial attachment was gently removed together with a surrounding rim of the normal tentorium; special attention was paid

to avoid injury when dissecting the tumor close to the straight sinus. The remaining tentorium around the sinus was intensely coagulated with bipolar cautery. It was unclear, however, whether the tumor had infiltrated into the straight sinus. Total time from skin incision to closure was 3:45 h with 300 ml blood-loss. The postoperative course was uneventful. Comment. The Concorde position was very useful in this case. The entire left posterior tentorium was nicely observed without the need for the surgeon to take up an unusual position. This meningioma was fortunately so soft that most of the mass was easily removed with suction under minimal cerebellar retraction. The softness of the tumor enabled preservation of the inferior vermian veins as well as their isolation from the cortex. Although sacrifice of the inferior vermian veins does not usually cause any complications, their preservation would probably reduce postoperative edema to some extent.

231

1 Inferior vermian vein 2 Straight sinus 3 Left tentorium 4 Left occipital lobe

232

Tentorial and Posterior Fossa Meningioma

Case 99 Lateral Pyramid (It)

This 62-year-old woman developed ataxia over a year earlier. Her recent neurological deficits were left hearing difficulty of 15 dB on audiogram, bilateral pharyngial hyporeflexia and bilateral papilloedema. Operation. With the patient in the prone position a left unilateral U-shaped suboccipital skin incision was made, including the left occipital area for a possible supratentorial approach, though this turned out to be unnecessary. A craniectomy was made in the suboccipital region far enough to visualize the left sigmoid and transverse sinuses and was extended somewhat to the right side. A drainage tube was inserted in the left posterior ventricle, and the bulging cerebellum became markedly slack when CSF drained from the tube. The cisterna magna was first opened, where herniation of the bilateral tonsils was noted. A small portion of the tumor surface was found at the lateral edge of the left cerebellum. A lateral portion of the cerebellum measuring 1.5x3 cm which had been compressed by the tumor was removed. The meningioma was soft but very hermorrhagic. First, the tumor attachment to the lateral area of the petrous pyramid was dissected through a very narrow space obtained by gentle retraction of the tumor in the medial direction. The separation of the attachment reduced the bleeding from the tumor, and about 90% of the mass was easily removed with a large suction. During dissection of the bottom portion of the tumor the posterior inferior cerebellar artery (PICA) was found to be running through it. Its main trunk was isolated but one

distal branch was sacrificed. The left anterior inferior cerebellar artery, which had been suspected from the preoperative vertebral angiogram to be embedded in the upper pole of the tumor, was not found but was believed to have been preserved because no arterial bleeding was encountered during dissection in this region. Cranial nerves V, VII, VIII, IX and X were identified behind the tumor and were preserved. The IXth and Xth nerves had been most intensely compressed and degenerated by the tumor. The dura at and around the attachment was removed and the pyramidal bone under the dura was partially drilled off. Radical removal of the invaded bone was abandoned for fear of CSF leakage and complications with the cranial nerves. The total time was 3:30 h with 400 ml blood-loss. The postoperative course was uneventful. All the preoperative deficits disappeared. Comments. We have operated on 6 similar meningiomas in the lateral pyramidal area. All were easily removed because the cranial nerves were located behind the mass and generally were not involved in the tumor even though the mass was huge. They were very different from the medial pyramidal cases, the "clival meningioma". When the tumor is located only infratentorially, supratentorial craniotomy is unnecessary but the lateral and cephalad edges of the craniectomy should be removed far enough to visualize the transverse and sigmoid sinuses. When the tumor attaches strongly and extensively to the tentorial side, the procedure often becomes easier if the surgeon moves to the side of the patient in the prone position.

233

1 Left petrosal vein

2 Left transverse sinus

3 Left vertebral artery

234

Tentorial and Posterior Fossa Meningioma

Case J 00 Pyramid (rt)

This 62-year-old man had sustained a head trauma 2 weeks earlier. A large CP-angle tumor was found incidentally on the CT scan. The only neurological findings were slight ataxia, horizontal nystagmus and mild hearing difficulty in the right ear. Operation. With the patient in the lateral position, a right lateral suboccipital craniectomy of 3 x 4 cm was made. An attempt to approach the cisterna magna to suction CSF was unsuccessful because the tumor had almost totally occupied the right hemisphere. It was about to develop both upward and downward herniations, so the tentorium was found to be pushed markedly upward. It was very difficult to visualize the tumor in the tentorial side as it was hidden under a roof of the tentorium. Thus intracapsular removal of the tumor was started with the two-suction method and the superficial twothirds was soft enough to be removed with the large suction. After the lateral portion close to the pyramidal bone had been removed to debulk the tumor, the mass was dissected from the cerebellum step by step; part of the border was well demarcated and part strongly adherent. Throughout the procedure retraction of the cerebellum was unnecessary because piecemeal removal of the tumor produced a large space. Contrarily, retraction of the tumor with a hook was very helpful when dissecting the tumor from the cerebellum and pons. The central portion was so hard that it could be removed only with the aid of scissors; it was this portion that had appeared as a high-density area on the CT. In the bottom of the tumor many veins were sacrificed because of their

strong adhesion, but main arterial branches were preserved. After more than 80% of the mass had been removed, the attachment to the pyramid was teased directly off the bone to find the facialacoustic nerve complex. The nerves were found to run downward under the tumor with moderate adhesion to it. They were well preserved together with the associated arteries. The region of the attachment was drilled off and a piece of the bone was sent for histological study. Very small granules with the appearance of fat were found all over the surface of the tumor. Were they part of the tumor? The time for the main procedure was 3 h with 300 ml blood-loss. The postoperative course was uneventful. The facial and co-chlear functions were fully preserved. Comments. (1) Although this large tumor was successfully removed through the window of a relatively small lateral suboccipital craniectomy, such a small craniectomy is sometimes very dangerous. If a swollen cerebellum is encountered, the craniectomy must immediately be enlarged. (2) In the beginning, bleeding from the dura and tumor was heavy, but elevation of the patient's head about 10 to 15 cm and partial removal of the tumor mass markedly reduced the bleeding by decreasing the venous pressure. (3) A large suction 4 mm in diameter was a very useful tool to reduce the mass quickly. However, because of its power, the surgeon must hold it in his dominant hand and it should always be applied in the direction of the center of the tumor, never its border, to prevent suctioning of normal surrounding tissue. It should not be used when working in the bottom of the tumor.

235

1 Right vertebra! artery 2 Right AICA 3 Right pyramid 4 Riaht tentorium

VI Neurinoma and Other Brain Tumors 1 Acoustic Neurinoma

The majority of acoustic neurinomas show very similar pathophysiology and anatomical relationships. As a result the surgical procedure differs little from case to case, and the techniques around the tumor are basically the same, although many surgeons have proposed their own methods. The main differences are in the route of approach, such as the transpyramidal or suboccipital, and in the patient's position, such as sitting or lateral. Today the goal of acoustic neurinoma surgery is the preservation of both the facial and the cochlear nerves,, as well of course as the total removal of the tumor with minimal complications. From the viewpoint of preserving the nerves, the size of the tumor greatly influences the surgical difficulty. In the case of a small tumor, less than 3 cm in diameter, the nerve is almost normal in size without strong adhesion to the tumor. In this section our general principles for the operation on a large neurinoma are described rather than individual cases because the surgical technique was very similar- m the great majority of,cases.

Anesthesia and Patient Position The patient is operated on in the lateral position under general anesthesia with spontaneous respiration. Spontaneous respiration is a more favorable cqndition_ than artificial to keep the intracranial and venous pressures at normal levels, and also to obtain brisk facial nerve response by electrostimulation. Hyperventilation is added at the beginning of the operation when the cerebellum is too tight to open the cisterna magna to suction CSF. Spontaneous respiration is also vital for detecting changes in cardiorespiratory status when excessive traction is applied to the medulla. Another important point is fluid transfusion. Although Mannitol and Furosemide (La-six) are routinely used, the input and output water balance must be maintained such that the fluid transfusion is about 500 ml behind the output both during and after the operation.

237

When placing the patient in the lateral position, care should be taken in the following points (Fig. VI-1): (1) The patient's head is elevated above than the heart level, usually with a 30 degree inclination of the upper portion of the operating table, in order to reduce the intracranial and venous pressures (arrow 1). (2) The affected side of the patient's neck is maximally stretched_ (arrow 4). By stretching the neck, the operative field is visualized without tilting the operative microscope and the patient's shoulder will not be m the way. (3) The head is flexed anteriorly, but not to the degree that the endo-tracheal tube is compressed (arrow 3). In this position the surgeon can sit at the corner of the operating table so that the patient's shoulder does not, get in the way. Some difficulty may be encountered with a short-necked, broad-shouldered patient. (4) The side of the head is positioned parallel to the floor. The head is rotated upward during the approach to the pontine side and is turned downward during that to the meatus by rotating the operating table and head fixation frame. It is usually difficult to change the position obtained by head flexion and neck stretching after the operation starts. (5) The patient's shoulder is placed close to the edge of the operating table on the side where the surgeon sits so that the table gets in the surgeon's way, as_ little as possible^ (arrow 2). The top of the shoulder is pulled moderately in the direction of the foot of the table with a bandage. The arm on the side of the tumor is placed on the armrest to lessen the respiratory load of its weight; the other arm hangs over the edge of the table. Of all the patient positions we have tried, we find the lateral position to be the most recom-mendable, especially for large acoustic neurinomas. Its advantages are as follows: (1) Anesthesia can be carried out under spontaneous respiration, which enables normal venous and intracranial pressures to be maintained; this is especially important in cases of advanced hydrocephalus and also to obtain facial nerve response to electrostimulation because no muscle relaxant is used. (2) The cerebellum sinks_by its own weight, so that cerebellar retraction is usually minimal and is occasionally unnecessary. Cerebellar uncapping is totally unnecessary. (3) The surgeon operates in the usual position with the

Fig. VI-1. Placement of the patient in the lateral position. (1) Upward tilting of the top plate of the operating table about 30 degrees. ( 2 ) Positioning of the patient on the lateral edge of the operating table. (3) Flexing of the head. (4) Stretching of the neck

238

Acoustic Neurinoma

axis of the operating microscope almost perpendicular to the operating field, resulting in less physical fatigue. One disadvantage of this position is the pooling of blood in the field. To solve this problem continuous drainage using a shunt tube is recommended. Generally, however, bleeding from an acoustic neurinoma is mainly venous and is very mild when the patient's head is positioned correctly; it has rarely been a problem in our series, in which the average blood-loss was less than 100 ml during the whole procedure from dural opening to closure.

Operative Procedure

An S-shaped skin incision of about 10 cm is made in the lateral suboccipital area. The fascia and muscle incision is done in a_different plane from that of the skin incision to prevent postoperative CSF leakage. A lateral suboccipital craniectomy of about 4j* 3 cm in size is made so as to partially visualize the transverse and sigmoid sinuses. As the bone in the lateral suboccipital area is very thick, thinning it with a drill makes it easier to obtain a proper lateral opening. It is vital that enough of the bone be removed to visualize the venous sinus. Extending the medial and caudal opening is generally unnecessary (Fig. VI-2). A ventricular drainage or shunt^operation are ordinarily not needed except for some severe cases where the neurological Fig. VI-2. Skin incision and craniectomy

condition is severe due to advanced hydrocephalus. In most cases with large tumors the cerebellum is very tight when the dura is opened even with elevation of the patient's head and hypervcntilation. The First procedure is to approach the cistcrna magna, from which CSF is suctioned. Visualization of the cistern and suctioning of the CSF are somewhat difficult because of the distance between the cistern and the craniectomy and the initial tenseness of the cerebellum, but once the CSF has been suctioned the cerebellum becomes remarkably slack in almost all cases. If it does not, the operation had better be abandoned because of the high risk of postoperative complications. Incorrect positioning of the patient's head is the most likely cause of such a condition. Over-transfusion of fluid, by which we lost one patient, is another possible cause. With slight medial retraction of the cerebellum the tumor comes into view. The exposed surface is coagulated and cut after it has been stimulated to exclude an unusual location of the facial nerve, though this is very rare: it ran across the exposed upper surface in only two cases of our series. Intracapsular decompression is performed using two suctions. When a tumor is large and hard, a large suction of 4 mm diameter is held in the dominant hand and a medium-sized suction in the other. All acoustic neurinomas are removed more or less intracapsularly with this method (Fig. VI-3). It is worth remembering that the nerve is never embedded in the neurinoma, unlike the case of mcningioma. Electrostimu-lation with a high voltage of about 50 to 80 v. is performed from inside the tumor capsule to identify the approximate location of the facial nerve. This has been done successfully in about three quarters of our cases. After intracapsular decompression, dissection around the upper half of the tumor is performed except on the meatus side, which is attacked in the final stage. Care should be taken to isolate the anterior inferior cerebellar artery (AICA) and branching arteries, the petrosal vein and that of the cerebellopontine fissure, and the IXth and th nerves.

Fig. VI-3. Using two suctions for internal decompression

239

Fig. VI-4. Lateral retraction of the tumor with a hook connected to a self-retaining retractor

nerve runs caudally, separately from the other two. The tumor around the nerves is removed piecemeal using a sharp dissector or scissors. The stronger the tumor adheres to the nerve, the more often should the scissors be used in order to minimize nerve injury. Scissors with right angled blades are very useful for this purpose. In some instances the facial nerve is flattened like an arachnoid membrane over the tumor capsule, but will come together to form a bundle like a normal nerve when it is isolated from the tumor without injury (VI-5). As the midportion of the facial nerve is the most strongly adherent to the bottom of the tumor, isolation of this portion should be approached from the meatus side also. As the final step, the meatus is opened with a diamond drill after the dura in the lateral side of the porus has been cut

Afour-pronged hook, a rake,is the most important instrument for acoustic neurinoma surgery (Fig. VI-4, VI-5). It is connected to a self-retaining retractor attached to the multipurpose head-frame. A tumor whose intracapsular content has been removed is retracted laterally from the pons with the hook, thus giving an ample space between the tumor and the pons without mobilization of the latter. The surgeon uses both hands solely to dissect the tumor. The hook retracts the tumor further as the dissection from the pons proceeds. Rough retraction must be avoided lest the pons be injured or the tumor capsule broken. Until the border between the cerebellum and pons is reached, adhesion of the tumor to the ccrebellar cortex is too strong to dissect without injury to the latter. Usually the large vein of the cerebelloponline fissure is found at the border between the cerebellum and pons. Dissection of the tumor from the pons is easier because the pontine arachnoid is much stronger than the cerebellar one. Of course, injury to the vessels on the pontine surface should be avoided. Bleeding on the pontine surface is controlled with Oxycel covering rather than with bipolar coagulation except for bleeding from the cut end of a vessel. The facial nerve should be located as soon as possible. Elec-trostimulation combined with the facial monitor that we have developed is the best way to do this; the instruments and the technique for preserving the facial nerve arc explained later. After removal of the upper half of the tumor, great care is paid to preserving the facial and cochlear nerves at the bottom of the tumor. The facial nerve is ordinarily dissected from the proximal portion close to the pons tow;ard the distal, for two reasons: the facial response evoked by clec-trostimulation sometimes becomes weak due to injury to the nerve when the distal side is dissected first, and the initial approach from the pontine side helps to reduce compression of the pons and cerebellum. The cochlear nerve is commonly located close to the facial nerve while the affected vestibular

Fig. VI-5. Isolation of the thinned-out facial nerve with bipolar forceps connected to a stimulator while retracting the tumor with a hook

and its edge shrunk with the bipolar coagulator. The bone is drilled out to make a hole about 10 mm in diameter, according to the size of the intracanalicular mass. Wider opening enables the tumor to be removed more easily but is more likely to cause postoperative CSF leakage. The chief difficulty is the radical removal of the tumor hiding in the depth of the meatus without damage to the nerves there. It is advisable to isolate the intracanalicular portion of the tumor from the nerve using the bipolar forceps connected to a stimulator with which both isolation and nerve stimulation can be simultaneously carried out. After the nerve has been located (it is usually at the bottom) the residual tumor in the depth of the meatus is removed with a small ring curette, occasionally with the aid of a mirror (Fig. VI-6).

240

Acoustic Neurinoma

After complete hemostasis has been confirmed (Fig. VI-7), the dura is watcrtightly closed, sometimes with the aid of homologous dural graft (Lyodura). Fibrin glue is often used today instead of Biobond for packing the mastoid sinus opened at the time of drilling the porus or craniectomy, and for supplementary sealing of the dural suture lines for watertight closure. The cranicctomy is repaired with a ceramic plate to prevent postoperative CSF accumulation and also for cosmetic purposes, especially in young patients. During the first postoperative night, water balance is maintained wilh input about 500 ml behind output and the patient lies with the head positioned about 30, occasionally 45, degrees higher by inclining the bed.

Preservation of the Facial Nerve

Fig. VI-6. Removal of a residual portion of tumor from the depth of the meatus with a smalt ring curette

The identification and preservation of the facial nerve are two of the most important matters in neurinoma surgery. The need for gentle and meticulous dissection of the nerve from the tumor is obvious. Here Т should like to stress the usefulness of our new instrumentation, which consists of an ordinary bipolar forceps connected to an electrical stimulator and a sound monitor for facial movements. Anesthesia is better maintained with spontaneous respiration because muscle re-

Fig. VI-7. After removal of the tumor. ( 1 ) Right vertebral artery; (2) Right superior cerebellar artery; (3) Right petrous vein

241 laxant, necessary for artificial respiration, interferes with the facial response to electrical stimulation. Two bfp'olar forceps arc kept on hand; one is connected to the stimulator while the other is used for coagulation. The former is used simultaneously for dissecting the tumor and stimulating the nerve while the stimulating current is applied continuously. From 20 to 80 volts are used until the facial nerve is located, after which 1 to 4 volts are used with a duration of 1 msec and frequency of 4 Hz. The minimum voltage necessary to elicit responses must be used because the nerve becomes exhausted. Care should be taken in the following points: (1) The bipolar forceps must be insulated except at the tips to avoid leakage of current into the surrounding tissues. When insulated for-ceps are not available, ordinary forceps can be temporarily insulated with a small sheet of adhesive surgical drape or' a thin silastic tube. (2) A marker, such as a piece of thread, is attached to the connecting cable to distinguish the stimulating forceps from the coagulating. (3) The accessory nerve, which is always present in the operating field, is stimulated occasionally throughout the procedure in order to check that the circuil from the stimulator is active. The facial monitor is also checked by tapping on the patient's head or the head-frame. In one case the facial nerve was inadvertently sacrificed because we did not notice that the stimulator had been disconnected. (4) The response of the masseter muscle evoked by the motor root of the trigeminal nerve should not be mistaken for that of the facial nerve. In a large neurinoma both nerves are very close to each other. Touching the temporal area and feeling the muscle movement through the drape is the best way to avoid error (Fig. VI-8). Conventionally the patient's face is observed during stimulation by the anesthesiologist or. jmcilliary_ personnel under the drapes. Continuous observation throughout the procedure is impossible unless the patient is in the sitting position, and

Fig, VI-8. Facial movement monitor system. (A) Usual bipolar coagulating forceps connected to a high frequency generator. (B) Usual bipolar coagulating forceps connected to electrostimulator. (C) Pair of accplerometers connected to amplifier and speaker

Fig. Vl-9. A case where the facial nerve was sacrificed because its course was unusual. See text

prolonged communication between the surgeon and anesthesiologist is inconvenient. To overcome these problems we developed a sound monitor of facial movement, consisting of a pair of accelerometers, an amplifier, and a speaker. Acceler-ometers weighing 3 g, which transform mechanical movement into an electric current, are attached to the orbicularis oculi and oris muscles. The facial movements produced by stimulation of the facial nerve in the operating field are converted to sound by means of the acceleromcter, amplifier, and speaker. Thus the surgeon is always able to recognize facial responses without asking the anesthesiologist (Fig. VI-8). About a half of the time for the main procedure is spent on identification and preservation of the facial nerve: a much longer time is necessary for preserving the cochlear nerve. In our series, the operation on cases whose facial nerve had been sacrificed"in other hospitals took only half as long as the average. The facial nerve should, as already noted, be identified as soon as possible with the aid of the stimulator and monitor. After internal decompression the tumor is easily mobilized to identify the nerve. When it is found, the part of the tumor contralateral to it can be removed, which reduces pressure on the nerve. Then the proximal portion of the nerve close to the pons is visualized (and confirmed by stimulation with the bipolar forceps) in the narrow space obtained by lateral retraction of the tumor with the hook. Isolation of this part of the nerve from the tumor is usually not difficult. If dissection is started from the meatus side, the nerve on the ponlinc side will become occasionally unresponsive to stimulation even though it maintains its anatomical continuity because electrical conduction is disturbed by surgical maneuvers at the distal portion in the meatus. The strongest adhesion of the facial nerve to the tumor is commonly encountered in the mid-portion between the pons and the meatus, and the dissection here has often to be done from various directions. A scissors or micro-knife should be used rather than a dull-edeed dissector or a curette. It is sometimes verv dif.fi-

242

Acoustic Neurinoma

cult to isolate the thin nerve without leaving fragments of the tumor on it. After as much as possible of the intracranial portion has been removed the intracanalicular tumor is attacked. The roof of the meatus on the approach side is removed with a diamond drill without breaking the intracanalicular dura. Injury to the dura and the exposed side of the tumor does not usually produce any problems because the facial nerve tends to be in the bottom half of the canal in most cases, but in one unusual case the facial nerve was sacrificed at the time of drilling as the intracanicular portion of the nerve was on the exposed surface of the tumor even though the intracranial portion had been at the bottom of the mass (Fig. VI-9). The more the bone is drilled away the easier it is to remove the tumor, though the possibility of CSF leakage will increase (Fig. VI-6). Generally, the intracanalicular portion of the nerve is adherent to the dura rather than to the tumor. The dissection in the deepest part of the canal hidden by the bone is carried out with a small flexible curette with a thin blade, occasionally with the aid of a mirror. It is very useful in the intracanalicular procedure to use the forceps

Fig. VT-10. Audiograms of Cases 1 to 6 with tumor sizes of 30, 32, 35, 40, 45, and 48 mm, respectively. Open circles: preoperative levels. Solid squares: postoperative levels. Open arrow: preoperative scaleout. Solid arrow: postoperative scale-out

connected to the stimulator for dissection and stimulation simultaneously. Dissecting the nerve without the stimulating forceps and facial monitor is like passing through a mine-field without a mine-detector. In 92% of our cases the anatomical continuity of the facial nerve was preserved. In some of the cases of the remaining 8%, partial facial function was maintained even though the nerve appeared to have been sacrificed. Contrarily, severe palsy was observed at discharge in about 10% of cases although the nerve was well preserved both anatomically and physiologically. In almost all of these cases the palsy showed improvement after one or, occasionally, two years. Severe palsy was observed in less than 10% of large neurinomas of more than 3 cm in diameter. Three patients underwent fa-

243 cial-hypoglossal nerve anastomosis with favorable results. Facial nerve function was excellent in all cases of small neurin-oma.

Preservation of the Cochlear Nerve In our experience, as in the literature, cochlear nerve function was preserved in cases in which some hearing ability had remained preoperatively; postoperative improvement was observed only in very rare cases. Previously the action potentials driven by clicks in the affected ear were directly recorded from the cochlear nerve in the operating field. However, such a method of detection is applied only in those cases in which preoperative hearing function has been well preserved because it takes too long. Gentle and meticulous dissection is really the only way to preserve the nerve. In principle, identify the facial nerve by the method explained earlier as soon as possible; some structures similar to a nerve bundle will be found close to the facial nerve on the pontinc side. One of these is the cochlear nerve and the other the vestibular, though differentiation is impossible. Both structures are isolated from the tumor more gently than the facial nerve, as the cochlear nerve is far more vulnerable than the latter. One of the two bundles may be preserved and the other vanish on the tumor surface on the side contralateral to the facial nerve. In patients whose hearing was functioning preoperatively the vanishing nerve may reasonably be suspected to be the vestibular nerve. We must exercise far greater thoroughness and gentleness when isolating such structures than when working on the facial nerve only, though the time required and the surgeon's fatigue increase accordingly. Auditory function was preserved postoperatively in 8 of 18 patients who preoperatively had retained hearing acuity above 70 dB as confirmed by audio-gram. The size of the tumor in 8 patients was 18, 28, 30,

32, 35, 40, 45 and 48 mm as measured on the CT. Hearing acuity improved postoperatively in two cases of cystic tumor, 32 mm and 45 mm in diameter. The postoperative audiograms in these cases showed that the fibers for high pitch are more easily damaged by surgical manipulation than those for low pitch (Fig. VI-10).

Operative Results We operated on 95 acoustic neurinomas; 87 of them were larger than 3 cm. Complete removal of the tumor was achieved in 94% of the cases. One patient died due to brain edema caused by overtransfusion on the first postoperative night. This case was the only one of direct operative death during hospitalization. We lost one 4 months postoperatively due to pneumonia and another died 16 months postoperatively due to a large infarction in the pons, which had been invaded by residual tumor. Among the postoperative complications, CSF rhinorrhea was encountered in 15%; most developed in the earlier cases of our series and three-fourths were transient. When it occurs, conservative treatment with Manni-tol and glycerol is started, and the patient's head is kept raised. If there is no improvement in 5 days, lumbar drainage is tried. Ventriculoperitoneal shunt is required in a case with hydroce-phalus. Surgical repair was necessary in 4 early cases of our series. In 4 patients the long tract sign of sensory and/or motor dysfunction was observed 2, 3, 10, and 12 months later. A noteworthy complication was mental depression, which was observed in about one third of the cases. It disappeared over a period of a few weeks and antidepressive drugs were often very effective. It is likely that surgical maneuvers in the ponto-medullary area induce a disturbance of cathecholamine metabolism. We have experienced similar depression after operations on other posterior fossa tumors.

2 Trigeminal Neurinoma

General Considerations We operate on almost all trigeminal neurinomas through a sub temporal approach. Removal of a trigeminal neurinoma is generally easier than that of an acoustic neurinoma for the following reasons: (1) The operative exposure in the subtemporal approach is wider. (2) The trigeminal neurinoma does not involve neighbouring cranial nerves as much as the acoustic neurinoma where the facial nerve is always closely associated. (3) Postoperative complications are generally milder except when complete palsy of the first trigeminal

branch occurs, though this is rare. In three cases where the neurinomas occupied only the suboccipital space a lateral suboccipital approach was taken like that for an acoustic neurinoma. In comparison with the subtemporal approach, the suboccipital one is more difficult because the operating field is narrow and deeper. However, the operation is a little easier than that for an acoustic neurinoma of the same size because the surrounding cranial nerves can easily be isolated. The postoperative course of all 16 cases was uneventful and additional sensory disturbance was observed in 6 cases.

Case 101 Subtemporal Approach (rt)

This 57-year-old woman had been deaf in her right ear since childhood, due suspectedly to otitis media. She had recently developed clouding of consciousness and mild left hemiparesis. The trigeminal function was normal. Operations. With the patient in the lateral position, a right medial subtemporal approach was made. In the beginning the brain was tense and temporal retraction was difficult because no lumbar drainage had been instituted. After CSF was suctioned from the crural cistern the temporal retraction became easy. The tumor was partially identified medial to the tentorial edge. The tentorium was cut counter-clockwise from the posterior portion and opened widely; the flap was reflected and pulled anteriorly with a thread. The trochlear nerve was isolated from the medial surface of the tumor. Many bundles of the trigeminal nerve were found on the tumor surface; threefourths of them were successfully isolated. Some had vanished in their course and mingled with the tumor capsule; this was the point where the tumor probably developed. Isola-

tion of the nerve bundles facilitated removal of the tumor mainly with suction and partly with scissors. The mass was shaped like a dumb-bell; the larger portion was located in the posterior fossa and the smaller in Meckel's cave together with the Gasselian ganglion. Meckel's cave was markedly enlarged. Some small fragments of the tumor remained around the nerve bundles, probably less than 1 % of the total mass. Finally, one bundle was anastomosed at three points with 10-0 sutures. The main procedure from dural opening to closure took 2h with 200ml blood-loss. Postoperative course: The patient's neurological deficits disappeared quickly. However, dysfunction of the first division of the right trigeminal nerve, which was normal preoperatively, continued for one year. Comments. Retraction of the temporal lobe should be done patiently until opening the crural cistern from which CSF is suctioned; it is especially important when lumbar drainage has not been instituted. Lumbar drainage is strongly recommended for the subtemporal approach.

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1 Right superior cerebellar artery 2 Basilar artery 3 Meeker s cave 4 Tentorium

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Case 102 Cerebellopontine Angle (It)

This 46-year-old woman had undergone partial removal of the tumor in another hospital 10 years previously. Recently she developed gait ataxia and paresthesia in the left side of the face. On examination a marked atrophy of the left mas-seter muscle and advanced cerebellar ataxia were observed. Operation. With the patient in the lateral position a left lateral suboccipital craniectomy was performed wide enough to partially visualize the transverse and sigmoid sinuses, as in the operation for acoustic neurinoma. First, the cisterna magna was opened to suction CSF; the cerebellum became very slack. The tumor was visualized without cerebellar retraction. Intracapsular decompression was performed. The whitish contents were soft and were removed easily using tumor forceps and suction. After the lower cranial nerves had been identified, the exposed side of the tumor was dissected from surrounding structures such as the cerebellum, tentorium and pyramidal bone. Removal of this portion was easy because there were no important structures in the way. Contrarily, dissection of the lower half of the tumor was very difficult because it was strongly adherent to many critical structures such as cranial nerves III to VIII, arteries and the pons. The trigemmal. acoustic and facial nerves had been displaced cau-dallv. The triseminal nerve had been stretched and Meckel's

cave was enlarged; this was the reason one of the main preoperative deficits was trigeminal nerve dysfunction. The facial nerve was identified with electrostimulation. The facial and acoustic nerve complex was incorporated in the somewhat thickened capsule. Some portions of the capsule which were strongly adherent to the facial nerve were not dissected. The tumor had spread supratentorially in the medial side of the tentorium, where it had compressed the posterior cerebral and superior cerebellar arteries and the oculomotor and trochlear nerves. The trochlear nerve was visualized with a mirror; it had been considerably displaced. The upper dorsal portion of the tumor had spread close to the quadrigeminal region. The capsule was adherent to a wide area of the pontine surface, and its removal in this area was the most difficult part of the operation. Only the loosely adherent pieces were teased off and about one third was left to avoid excessive injury to the fine vessels on the pontine surface, which was very soft. Finally, the basilar arterial trunk and all cranial nerves from ITT to XII were visualized. The postoperative course was uneventful. The neurological deficits improved gradually. Comments. (1) For such a large tumor as this a subtemporal approach would have been better for removal of the upper portion of the tumor (tentorial side), but removal of

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1 Basilar artery 2 Left superior cerebellar artery 3 Left posterior cerebral artery 4 Meckel's cave 5 Tumor capsule

the lower half (spinal side) by this approach would have been even more difficult than it was. (2) The exposed pons was surprisingly soft; it had probably become edcmatous. A similar condition was encountered in an operation for a large acoustic neurinoma. The neurological deficits were often minimal even with such a soft pons. (3) It might have been possible to dissect the capsule attached to the pons without causing severe deficits had we spent a great deal of time on the procedure. However, we thought that subtotal removal was acceptable because such small fragments of epidermoid would be less likely to grow significantly.

4 Glioma

General Considerations Surgical therapy for glioma and other malignant tumors is not ajmighty but it is still the first choice before radiation and chemotherapy. The CT scan has contributed not only to diagnosing brain tumors but also to evaluating the results of surgical therapy. The surgeon can operate with accurate information from the CT as to the extent of a tumor and its anatomical relation to the critical brain structures. The residual mass of the tumor, which had previously been known only from the report of the surgeon, can now be clearly visualized in the postoperative CT scan. In the near future intraoper-ative CT scan will come, to be more widelv utilized in operations on malignant tumors to determine the extent of the residual mass. Basically, though, advances in chemotherapy and immunological therapy for glioma are most needed, as for cancer. Although the statistics on the survival periods show no significant difference between subtotal and radical removal of malignant gliomas, radical removal of benign gliomas is clearly better than partial. Tt is always a problem how much of the surrounding tissues where tumor cells have probably invaded should be removed in addition to the tumor mass itself. Malignant tumors occupying a silent area can be extensively removed together with the surrounding normal structure like a lobectomy. However, when a tumor is located in or close to a critical area, sharp dissection of the tumor from the surrounding tissue should be done as in the surgery for meningiomas. Although many unsolved problems remain, our surgical techniques for glioma are as follows. 1. For dissecting the border between the tumor and the surrounding tissues, we use a cotton patty (a piece of Bernsheets 1 x 1 or 2 x 2 cm) held with forceps. The patty is changed about every jialf minute because the rough surface of the cotton soon-bccornes smooth with dissected tissue; its initial roughness is very suitable for gentle dissection. Through the patty held in the forceps, the surgeon can feel the delicate difference in hardness between the tumor tissue, gliosis, and edematouslirain, though the difference in color is also helpful. The isolation of the tumor from the surrounding tissues in this way is reasonable because some portion of the brain should be removed along with the tumor. The method is also applicable to the intrasellar procedure for pituitary adenomas (see figure at bottom). 2. A large suction 4 mm in diameter is often useful for removal of both soft and hard gliomas; the sucking power is almost the same as that of an expensive ultrasound suction. It is simple to handle and available in any operating theater. The tube must of course have a small hole for finger control of suction pressure. Care should be taken not to remove nor-mal surrounding tissues. To prevent this, it is recommended that the large suction be held in the dominant hand andjm ordinary one in the other. In this way dissection of the tumor and suctioning of blood can be effectively performed (see Fig. II-9, p. 8 in the section on instrumentation). 3. The surface of the normal brain is covered at every step with a larger cotton sheet, produced by Codman Co., which is harder than Bemsheets. The latter are best suited

for dissection and hemostasis because they are softer, nonbonded and non-woven, providing an excellent capability of hemostasis in the operating field. On the other hand, the former is harder and less adhesive to the brain surface. Covering the surface of normal areas is important for the following reasons: (1) In the small visual field under the operating microscope, the covering provides a good landmark by which the surgeon can recognize the regions already dissected around a large tumor. (2) The border between the tumor and normal surrounding brain is at first easily dissected by the aid of difference in color. However, the appearance of normal dissected brain becomes pathological because of minor bleeding while another area is being dissected. In general, the normal brain should be covered as soon as the plane is made. The use of two different kinds of cotton patty, one for normal brain and the other for dissection, is highly recommendable. 4. The special retraction work in glioma surgery is another important technique especially in the case of a deep-seated tumor; it is equally useful in the removal of meningiomas and neurinomas. For example, a large thalamic glioma can be removed through a small cortical incision of 3 cm with the aid of multiplej.apered retractors. A four-pronged hook is useful with certain harder gliomas. A brain retractor with a bent.tip., about 2 mm in width, is also helpful for retracting a soft tumor, like Heifetz's brain retractors. This kind of retractor can be made intraoperatively by^bending the tip with clamp forceps.________ 5. In the case of a large glioma. which is usually accompanied by high intracranial pressure and vascularity with marked perifocal edema, initial quick debulking of the mass is more important than tedious hemostasis and removal; the decompression reduces hemorrhage and provides a large working space. Needless to^ say, the position of the patient's head is also important to decrease venous pressure, thus minimizing unnecessary blood-loss.

Case 103 Gliomas in the Thalamus and Adjacent Regions

We made a direct approach to thalamic and paraventricular gliomas in 42 cases, mainly through a parietal or frontal cortical incision of 3 cm in length. In the majority of cases subtotal removal was successful without postoperative complications. It has been our experience that gliomas in the thalamus and adjacent areas can be removed with slight or almost no postoperative deficits as long as the tumor mass only is removed. 1. Importance of topographical orientation of a deepseated glioma: (1) Although preoperative study of the tumor location on the CT scan is important, its topographic relations have to be kept in mind during the operation. For this purpose it is useful to reconstruct the location of the tumor threedimensionally from the CT scan. This can be done simply, without a special computer system. Ordinary CT scan films are projected onto a wall with an overhead projector and magnified to actual size. The details of each slice are traced with a felt-tipped pen onto a transparent film held over the image on the wall. The resulting sketches are separated by transparent plastic sheets 10 mm in thickness, and the whole is put into a plastic frame. The three-dimensional reconstruction to actual size thus obtained provides accurate orientation of the tumor both pre- and intra-operatively (see figure at right). (2) Most neurosurgeons have experienced difficulty with the anatomical relation between the border of deep-seated tumors and the critical structures of the internal capsule, thalamus and basal ganglia while dissecting and removing such tumors. Keeping three-dimensional orientation is usually difficult under the operating microscope, though the microscope makes it easier to distinguish clearly the difference in appearance of normal and pathological tissue, and to dissect the tumor gently from surrounding tissues. (3) The ventricle is the most important landmark in the operation for deep-seated tumors. Although the surgeon must remember the patient's head position before covering with the drape, intraoper-ative visualization of the ventricle is the best confirmation of the anatomical relation when removal of the tumor has been started in the depth. If the ventricle has collapsed or is absent, the removal of a thalamic tumor is very difficult because proper orientation cannot be made. 2. Thalamic and paraventricular gliomas in the anterior portion of the ventricle: With the patient in the supine position a frontal craniotomy is made. A frontal ventricular tap is performed and then a cortical incision of 3 cm is made. An approach to the anterior horn of the ventricle is made through this incision and the tract of the ventricular tap. The patient's head is kept straight till the anterior horn of the ventricle is reached. It is then rotated so that the ventricle can be seen perpendicularly without tilting the microscope. Four tapered brain retractors are placed around the approach made through the 3 cm incision. Care should be taken that all four retractors are not in use simultaneously but the brain is retracted with only two of them at a time according to the direction of approach while the other two are released. When a small tumor is removed in an approach through the anterior ventricle, the foramen of Monro, choroid plexus and

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prominence of the caudate nucleus are usually identified intraventricularly. However, when a tumor is large it is difficult to identify these structures and to differentiate between nor mal and pathological structures. The three-dimensional orien tation obtained from the CT scan, the difference in appearance of normal and pathological tissue under the microscope, and the difference in tissue hardness as felt with a small cotton patty held with forceps all facilitate the removal of the tumor. 1 Although the thalamus does not particularly differ in appear ance from other structures the caudate nucleus is somewhat different, having a striped greyish pattern. When this is reached, further removal should be abandoned. In our ex- ] perience, almost no additional deficits appear when only the tumor is removed, even in the depths around the basal ganglia and thalamus as long as these structures are not in sulted, i 3. Thalamic and paraventricular gliomas in the posterior half of the ventricle: In the prone position the patient's head is positioned straight on the head frame. A medial parietal craniotomy is made, and a ventricular tap toward the tri-gone is performed. Tracing the path of the tap an approach to the trigonum is carried out through a cortical incision of about 3 cm made in the medial parietal area. Once a successful approach has been made and the location of the ventricle well orientated, the patient's head is rotated toward the affected side to enable the surgeon to use the microscope perpendicularly. The trigonum, as well as the lateral body and inferior horn of the ventricle, are the most important landmarks for dissection of the tumor. When these structures have been deformed by the tumor, the position and course of the choroid plexus provide useful information for orientation. The corner of the trigonum which consists of the pulvinar and dorsome-dial nuclei of the thalamus can be attacked as deep as 10 mm without severe postoperative deficits. Injury to the ventricular surface generally causes no neurological deficit.

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Case 103-1 Gliomas Around the Anterior Half of the Ventricle

This 18-year-old boy suffered from anorexia nervosa and slight mental deterioration a year before surgery. His weight had decreased from 42 to 28 kg. Operation. A right transventricular approach was made through a frontal corticotomy of 4 cm. The tumor mass and surrounding cysts were grossly removed. Pathological reports were various, suprasellar germinoma, craniopharyngioma, and epidermoid carcinoma. Postoperatively no additional neurological deficits were found and the anorexia nervosa improved moderately. Irradiation was done. The boy is alive and well three years later.

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Case 103-2 Gliomas Around the Anterior Half of the Ventricle

This 74-year-old man noticed a slight left hemiparesis 6 months before surgery; it gradually progressed. Operation. A small portion of tumor was found superficially and just posteriorly to the Rolandic fissure. Total removal was successful because the tumor was well demarcated. Postoperatively the left hemiparesis improved and the patient is alive two years later.

Comments. 1) We planned partial removal of the tumor preoperatively because the preoperative CT scan showed that the tumor had invaded diffusely in the central area. Surprisingly, however, the tumor was found to be completely separated from the motor cortex by the Rolandic fissure which was very deep with a strong arachnoid like the Sylvian fissure. 2) Although we, were initially reluctant to perform total removal in this case because of the patient's age and the site of the tumor the surgery was successful. In such an elderly patient who seems likely to get over a surgical invasion with low possibility of postoperative additional deficits a direct attack is acceptable because the speed of tumor growth is slow. On the other hand we must remember that deficits already present in an elderly patient are unlikely to improve.

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Case 103-3 Gliomas Around the Anterior Half of the Ventricle

This one and a half-year-old boy had undergone an emergency operation a week before the surgery at another hospital; inner decompression of the right frontal lobe was performed because of severe herniation syndrome. The left hemiplegia continued at the time of the operation. Operation. A red hemorrhagic tumor occupied the center of the right hemisphere. Total removal was successful through the wound of the previous operation. The histological diagnosis of the tumor was ependynoma. Postoperative course: The left hemiplegia gradually improved. Three months later the boy could use his left hand and walk. However, he died two years later due to dissemination of the tumor to the whole central nervous system.

Comment. Postoperative improvement of the left hemiplegia surprised us: the structure of the internal capsule could not be found in the postoperative CT scan. This may indicate that the brain of a young child has a large potential for bilateral control.

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Case 103-4 Gliomas Around the Posterior Half of the Ventricle

This 48-year-old man had noticed headache and slight right hemiparesis about 6 months before the surgery. Operation. With the patient in the prone position a corticotomy of" 3 cm was made in the left medial parital cortex. The tumor was totally removed through the small corticotomy (see arrow). The histology was astrocytoma. Postoperatively the patient showed no additional deficits and the hemiparesis was lightly improved. Comment. Whenever we directly attack such deep-seated tumors as in this case we face a very difficult decision: subtotal or total removal of the bottom portion because it is located close to critical structures such as the internal capsule. The decision for subtotal or total removal is based on the by clearness of the tumor border and severity of the preoperative neurological deficits.

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Case 103-5 Gliomas Around the Posterior Half of the Ventricle

This 2-year-old boy developed right hemiparesis following a convulsion a month before surgery. The symptom became worse. Operation. With the patient in the prone position gross total removal of the tumor was performed through a cortico-tomy of 4 cm in the left medial parietal lobe. The histology was ependymoma. Postoperatively the boy recovered fully without any deficits. He died, however, one and a half years later due to recurrence.

Comment. Surgery for malignant tumors is only a temporary treatment, especially as the speed of growth of a brain tumor is very high in children. We need new therapeutic tactics developed from new fields such as immunology, genetics and biotechnology.

255 Case 104 Optic Glioma We have experienced 14 cases of optic glioma (excluding pure intraorbital glioma), 13 of which underwent a craniectomy. Most of them were diagnosed and operated on before the era of the CT scan. Though our experience is limited we should like to classify them into two groups: infant and child type. The optic glioma of infant type was characterized by early onset of the symptoms, usually at an age of less than one year, severe clinical signs including intracranial hypertension, and a tendency to grow large; the histological picture showed undifferentiated malignant astrocytoma. In the child type, the initial symptoms occurred after 2 years of age and were mild, and the histology was benign, showing a differentiated type of astrocytoma. The preservation of vision is the main purpose of the operation for optic glioma of the child type, while radiation therapy following a shunt operation is the first choice for the typical infant type. Operation. Infant Type. Operative findings in 4 of 5 optic gliomas of the infant type were more or less the same: the tumor was so huge that the bilateral optic nerves and chiasma were extremely swollen, and it was difficult to identify their anatomical contours. The bilateral carotid arteries were shifted laterally and the bilateral Al segments were narrow, producing a large indentation on the surface of the tumor. The tumor compressed the hypothalamus (D in the picture). Child Type: The location and size of the gliomas in the child type were very variable. In every case the unilateral optic canal was enlarged as was the optic nerve before entering and after exiting it. Most of the tumors were confined to the unilateral optic nerve or partially involved the chiasma.

Fig. VI-11. Follow-up studies of 8 eyes of 4 cases of optic glioma. Visual acuity of 5 eyes improved postoperatively before radiation

The operative procedure was planned according to the grade of preoperative vision, the period from onset of the symptoms, and the size of the tumor. In patients with very slight visual disturbance, only decompression of the optic canal was performed in anticipation of favorable effects from postoperative radiation therapy (A). In those whose vision was moderately impaired, the optic canal was unroofed, the optic sheath cut longitudially to decompress the nerve fibers, and the tumor partially removed with weak suction (B). In cases where unilateral vision had been severely impaired for more than

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Case 104 cont'd

3 months, the affected nerve was cut as close as possible to the end of the tumor in the nerve or the chiasma in order to preserve vision in the unaffected side (C). Postoperative course: All 9 cases of the child type were uneventful. The visual acuity and field improved postoperatively before radiation therapy in 6 cases. The improvements were in visual acuity rather than in visual field, however. In the follow-up of over 6 years the results continued to be satisfactory. In the infant type, 4 of 5 cases died; one was completely blind and showed poor physical development.

Comment. All of the tumors in our infant cases were too large to remove totally. Radical removal is possible if the tumor is of medium size and if sacrifice of vision is accepted. Although some authors have reported good natural courses in optic gliomas without operation, our results in the child type objectively showed quick recovery of vision after surgery, as shown in Table VI-1 and Fig. VI-12. We should not forget that the purpose of the operation is not total excision of the tumor but preservation of vision because optic glioma usually grows very slowly as it is said to be a hamartoma.

Table VI-1. Clinical and Histological Findings of Optic Glioma

Radiological sellar findings. J/co: intermediate type of J- and co-shapes. N: normal shape. Surgical findings. A. B. C. and D: same as in the color figures, Orb: intraorbital tumor. Histology. JA: juvenile astrocytoma. AA: adult astrocytoma. Follow-up. Frame: patient died.

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Laine E, Galibert P, Lopez C, et al (1963) Aneurysmes arterioveineux intra-duraux (developpes dans 1'epaisseur de la dure-mere) de la fossa posterieure. Neurochirurgie 9:147-158 Lamas E, Lobato RD, Esparza J, et al (1977) Dural posterior fossa AVM producing raised sagittal sinus pressure. Case report. J Neurosurg 46:804-810 Locksley HB (1966) Report on the cooperative study of intracranial aneurysms and subarachnoid hemorrhage. Section 5, Part 1, Natural history of subarachinoid hemorrhage, intracranial aneurysms and arteriovenous malformations. J Neurosurg 25:219-239 Long DM, Seljeskog EL, Chou SN, et al (1974) Giant arteriovenous malformations of infancy and childhood. J Neurosurg 40:304— 312 Luessenhop AJ, Ferraz FM, Rosa L (1982) Estimate of the incidence and importance of circulatory breakthrough in the surgery of cerebral arteriovenous malformations. Neurol Res 4:177-189 Luessenhop AJ, Mujica PH (1981) Embolization of segments of the circle of Willis and adjacent branches for management of certain inoperable cerebral arteriovenous malformations. J Neurosurg 54:573-582 Luessenhop AJ, Presper JH (1975) Surgical embolization of cerebral arteriovenous malformations through internal carotid and vertebral arteries. J Neurosurg 42:443-451 Luessenhop AJ, Rosa L (1984) Cerebral arteriovenous malformations. Indications for and results of surgery, and the role of intravascular techniques. J Neurosurg 60:14—22 Luessenhop AJ, Gennarelli ТА (1977) Anatomical grading of supratentorial arteriovenous malformations for determining operability. Neurosurgery 1:30-35 Lussenhop AJ, Rosa L (1984) Cerebral arteriovenous malformations. Indications for and results of surgery, and the role of intravascu-lar techniques. J Neurosurg 60:14—22 Malis LI (1982) Arteriovenous malformations of the brain. In: Youmans JR (ed) Neurological Surgery. Saunders, Philadelphia, vo!3, pp. 1786-1806 Manaka S, Izawa M, Nawata H (1977) Dural arteriovenous malformation treated by artificial embolization with liquid silicone. Surg Neurol 7:63-65 Martin NA, Wilson CB (1982) Medial occipital arteriovenous malformations. Surgical treatment. J Neurosurg 56:798-802 Maspes PE, Marini G (1970) Results of the surgical treatment of intracranial arteriovenous malformations. Vase Surg 4:164-170 Matsumura H, Makita Y, Someda K, et al (1977) Arteriovenous malformations in the posterior fossa. J Neurosurg 47:50-56 Mingrino S (1978) Supratentorial arteriovenous malformations of the brain. In: Krayenbuhl H (ed) Advances and technical standards in neurorosurgery. Springer, New York, pp. 93-123 Moody RA, Poppen JL (1970) Arteriovenous malformations. J Neurosurg 32:503-511 Morello G, Borghi GP (1973) Cerebral angiomas. A report of 154 personal cases and a comparison between the results of surgical excision and conservative management. Acta Neurochir (Wien) 28:135-155 Mori K, Murata T, Hashimoto N, etal (1980) Clinical analysis of arteriovenous malformations in children. Childs Brain 6: \ 3-25 Mullan S, Brown FD, Patronas NJ (1979) Hyperemic and ischemic problems of surgical treatment of arteriovenous malformations. J Neurosurg 51:757-764 Mullan S, Kawanaga H, Patronas NJ (1979) Microvascular embolization of cerebral arteriovenous malformations. A technical variation. J Neurosurg 51:621-627 Nornes H, Grip A (1980) Hemodynamic aspects of cerebral arteriovenous malformations. J Neurosurg 53:456-464 Olivecrona H, Rives J (1948) Arteriovenous aneurysms of the brain: their diagnosis and treatment. Arch Neurol Psychiat 59:567-602 Parkinson D, Bachers G (1980) Arteriovenous malformations. Summary of 100 consecutive supratentorial cases. J Neurosura 53:285299

267 Patterson RH Jr, Voorhies RM (1977) Surgical approaches to intracranial and intraspinal arteriovenous malformations. Clin Neurosurg 25:412-424 Pellettieri L (1980) Surgical versus conservative treatment of intracranial arteriovenous malformations. Acta Neurochir [Suppl] (Wien) 29:1-36 Ferret G, Nishioka H (1966) Report on the cooperative study of intracranial aneurysms and subarachnoid hemorrhage. Section VI. Arteriovenous malformations. An analysis of 545 cases of craniocerebral arteriovenous malformations and fis-tulae reported to the cooperative study. J Neurosurg 25:467-490 Pertuiset B, Ancri D, Clergue F (1982) Preoperative evaluation of hemodynamic factors in cerebral arteriovenous malformations for selection of a radical surgical tactic with special reference to vascular autoregulation disorders. Neurol Res 4:209-233 Pia HW (1975) The acute treatment of cerebral arteriovenous angiomas associated with hematomas. In: Pia HW, Gleave JRW, Grote E, et al (eds) Cerebral angiomas. Advances in diagnosis and therapy. Springer, Berlin, Heidelberg, New York, pp. 155-177 Riechart T, Mundinger F (1964) Combined stereotaxic operation for treatment of deep-seated angiomas and aneurysms. J Neurosurg 21:358-363 Samson D, Ditmore QM, Beyer CW Jr (1981) Intravascular use of isobutyl 2-cyanoacrylate: Part 1. Treatment of intracranial arteriovenous malformations. Neurosurgery 8:43-51 Spetzler RF, Wilson CB, Weinstein P, et al (1977) Normal Perfusion pressure breakthrough theory. Clin Neurosurg 25:651-672 Stein BM, Wolpert SM (1980) Arteriovenous malformations of the brain. Arch Neurol 37:69-75 Stein BM, Wolpert SM (1980) Arteriovenous malformations of the brain. I: Current concepts and treatment. Arch Neurol 37:1-5 Stein BM (1984) Ateriovenous malformations of the medial cerebral hemisphere and the limbic system. J Neurosurg 60:23-31 Stein BM (1971) The infratentorial supracerebellar approach to pineal lesions. J Neurosurg 35:197-202 Steiner L, Leksell L, Forster DMC, et al (1974) Stereotactic radiosurgery in intracranial arterio-venous malformations. Acta Neurochir [Suppl] (Wien) 21:195-209 Suzuki J, Onuma T, Kayama Т (1982) Surgical treatment of intracranial arteriovenous malformations. Neurol Res 4:191-207 Trumpy JH, Eldevik P (1977) Intracranial arteriovenous malformations: conservative or surgical treatment? Surg Neurol 8:171-175 Verbiest H (1962) Arterial and arteriovenous aneurysms of the posterior fossa. Psychiat Neurol Neurochir 65:329-369 Viale GL, Turtas S, Pau A (1980) Surgical removal of striate arteriovenous malformations. Surg Neurol 14:321-324 Wilson CB, U HS, Dominigue J (1979) Microsurgical treatment of intracranial vascular malformations. J Neurosurg 51:446-454 Wolpert SM, Stein BM (1979) Factors governing the course of emboli in the therapeutic embolization of cerebral arteriovenous malformations. Radiology 131:125-131 Wolpert SM, Stein BM (1975) Catheter embolization of intracranial arteriovenous malformations as an aid to surgical excision. Neuro radiology 10:73-85 Yamada S (1982) Arteriovenous malformations in the functional area: surgical treatment and regional cerebral blood flow. Neurol Res 4:283-322 Yasargil MG, Jain KK, Antic J, et al (1976) Arteriovenous malformations of the splenium of the corpus callosum: microsurgical treatment. Surg Neurol 5:5-14 Yasargil MG, Jain KK, Antic J, et al (1976) Arteriovenous malformations of the anterior and the middle portions of the corpus callosum: microsurgical treatment. Surg Neurol 5:67-80

IV Meningioma Adegbite AB, Khan MI, Paine KW, et al (1983) The recurrence of intracranial meningiomas after surgical treament. J Neurosurg 58:51-56 Bonnal J, Brotchi J, Born J (1979) Meningiomas of the lateral portion of the sella turcica. Acta Neurochir [Suppl] (Wien) 28:385-386 Bonnal J, Thibaut A, Brotchi J, et al (1980) Invading meningiomas of the sphenoid ridge. J Neurosurg 53:587-599 Carella RJ, Ransohoff J, Newall J (1982) Role of radiation therapy in the management of meningioma. Neurosurgery 10:332-339 Chan RC, Thompson GB (1984) Morbidity, mortality, and quality of life following surgery for intracranial meningiomas. A retrospective study in 257 cases. J Neurosurg 60:52-60 Crompton MF, Gautier-Smith PC (1970) The prediction of recurrence in meningiomas. J Neurol Neurosurg Psychiatry 33:8087 Derome PJ (1977) The transbasal approach to tumors invading the base of the skull. In: Schmidek HH, Sweet WH (eds) Current techniques in operative neurosurgery. Grune & Stratton, New York, pp 223-245 Fornari M, Savoiardao M, Morello G, et al (1981) Meningiomas of the lateral ventricles. Neuroradiological and surgical considerations in 18 cases. J Neurosurg 54:64-74 Fujii K, Lenkey C, Rhoton AL Jr (1980) Microsurgical anatomy of the choroidal arteries: Lateral and third ventricles. J Neurosurg 52:165-188 Giombini S, Solero CL, Lasio G, et al (1984) Immediate and late outcome of operations for parasagittal and falx meningiomas. Report of 342 cases. Surg Neurol 21:427-435 Gragorius FK, Hepler RS, Stein WE (1975) Loss and recovery of vision with suprasellar meningiomas. J Neurosurg 42:69-75 Grand W, Bakay L (1975) Posterior fossa meningiomas. A report of 30 cases. Acta Neurochir 32:219-233 Hakuba A, Huh CW, Tsujikawa S (1979) Total removal of a parasagittal meningioma of the posterior third of the sagittal sinus and its repair by autogenous vein graft. J Neurosurg 51:379-382 Hieshima GB, Everhart FR, Mehringer CM, et al (1980) Preoperative embolization of meningiomas. Surg Neurol 14:119-127 Jefferson A, Azzam N (1979) The suprasellar meningiomas: a review of 19 years' experience. Acta Neurochir [Suppl] (Wien) 28:381-384 Kadis GN, Mount LA, Ganti SR (1979) The importance of early diagnosis and treatment of the meningiomas of the planum sphenoidale and tuberculum sellae: a retrospective study of 105 cases. Surg Neurol 12:367-371 Kameyama M, Seki H, Ogawa A, et al (1980) A giant meningioma of the third ventricle. Neurol Med Chir (Tokyo) 20:1055-1060 Kobayashi S, Okazaki H, MacCarty CS (1971) Intraventricular meningiomas. Mayo Clin Proc 46:735-741 Kobayashi S, Kyoshima K, Nakagawa F, et al (1980) Diploic meningioma of the orbital roof. Surg Neurol 13:277-281 Kobayashi S, Gibo H, Sugita K, et al (1980) Werner's syndrome associated with meningioma. Neurosurgery 7:517-520 Konovalov AN, Fedorov SN, Faller TO, et al (1979) Experience in the tratment of the parasellar meningiomas. Acta Neurochir [Suppl] (Wien) 28:371-372 Ley A, Gabas E (1979) Meningiomas of the tuberculum selae. Acta Neurochir [Suppl] (Wien) 28:402-404 Logue V: Surgery of supratentorial meningiomas: a modern series. J Neurol Neurosurg Psychiatry 37:1277 MacCarty CS, Taylor WF (1979) Intracranial meningiomas: experiences at the Mayo Clinic. Neurol Med Chir (Tokyo) 19:569-574 Malis LI (1976) Tumors of the parasellar region. In: Thompson RA, Green JR (eds) Neoplasia in the central nervous system. Advances in neurolgy, vol 1-5. Raven Press, New York, pp 281-299

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269 cerebrospinal fluid leak after translabyrinthine surgery. Am J Otol4:126-128 House WF (ed) (1968) Monograph II. Acoustic neuroma. Arch OtoIaryngol88:576-715 House WF, Luetje CM (1979) Acoustic tumors, vol 2. University Park Press, Baltimore Kasantikul V, Netsky MG, Glasscock III ME, et al (1980) Acoustic neurilemmoma. Clinicoanatomical study of 103 patients. J Neurosurg 52:28-35 Kaye AH, Hahn JF, Kinney SE, et al (1984) Jugular foramen schwannomas. J Neurosurg 60:1045-1053 King TT, Morrison AW (1980) Translabyrinthine and transtentorial removal of acoustic nerve tumors. Results in 150 cases. J Neurosurg 52:210-216 Kobayashi S, Sugita K, Gibo H, et al (1983) Contralateral pontine hemorrhage as a complication of acoustic neurinoma surgery. SurgNeuroll9:117-119 Kurze Т (1978) Microsurgery of the posterior fossa. Clin Neurosurg 26:463-478 Lang J (1981) Facial and vestibulocochlear nerve, topographic anatomy and variations. In: Samii M, Jannetta PJ (eds) The cranial nerves. Springer, Berlin Heidelberg New York, pp 363-377 Levine RA, Ojemann RG, Montgomery WW, et al (1984) Monitoring auditory evoked potentials during acoustic neuroma surgery. Insights into the mechanism of the hearing loss. Ann Otorhinolaryngo!93:116-123 MacCarty CS (1975) Acoustic neuroma and the suboccipital approach (1967-1972). Mayo Clin Proc 50:15-16 Malis LI (1975) Microsurgical treatment of acoustic neurinomas. In: Handa H (ed) Microneurosurgery. pp. 105-120 Martuza RL, Ojemann RG (1982) Bilateral acoustic neuromas: clinical aspects pathogenesis, and treatment. Neurosurgery 10:1-12 Matsushima T, Rhoton AL, Oliveira E, et al (1983) Microsurgical anatomy of the veins of the posterior fossa. J Neurosurg 59:63105 McKenzie KS, Alexander F, Jr (1955) Acoustic neurinoma. Clin Neurosurg 2:21-30 Millesi H, Meissl G (1981) Intraneural topography of the extracranial facial nerve. In: Sammi M, Jannetta PJ (eds) The cranial nerves, pp. 394-402, Berlin Heidelberg New York, pp 394-402 Morrison AW, King TT (1973) Experiences with a translabyrinthinetranstentorial approach to the cerebellopontine angle. Technical note. J Neurosurg 38:382-390 Mount LA (1945) The lateral position for operations in the cerebellopontine angle. J Neurosurg 2:460-461 Nedzelski JM, Tator CH (1980) Surgical management of cerebellopontine angle tumors. J Otolaryngol 9:105-112 Ojemann RG (1979) Microsurgical suboccipital approach to cerebellopontine angle tumors. Clin Neurosurg 25:461-479 Ojemann RG, Crowell RC (1978) Acoustic neuromas treated by microsurgical suboccipital operations. Prog Neurol Surg 9:337-373 Ojemann RG, Levine RA, Montgomery WM, et al (1984) Use of intraoperative auditory evoked potentials to preserve hearing in unilateral acoustic neuroma removal. J Neurosurg 61:938-948 Olivecrona H (1967) Acoustic tumors. J Neurosurg 26:6-13 Oppel F, Mulch G, Brock M, et al (1981) Indications and operative technique for endoscopy of the cerebellopontine angle. In: Samii M. Jannetta PJ (eds) The cranial nerves. Springer, Berlin Heidelberg New York, pp 429-437 Ouaknine GE (1981) Microsurgical anatomy of the arterial loops in the Ponto-cerebellar angle and the internal acoustic meatus. In: Samii M. Jannetta PJ (eds) The cranial nerves. Springer, Berlin Heidelberg New York, pp 378-390 Piffko P. Pasztor E (1981) Operated bilateral acoustic neurinoma with preservation of hearing and facial nerve function. ORL 43:255^261 Rand R\V. Kurze Т (1968) Presentation of vestibular. cochlear. and

facial nerves during microsurgical removal of acoustic tumors. Report of two cases. J Neurosurg 28:158-161 Rand RW, Kurze Т (1965) Facial nerve preservation by posterior fossa transmeatal microdissection and total removal of acoustic tumors. J Neurol Neurosurg Psychiatry 28:311-316 Ransohoff J, Potanos J, Boschenstein F, et al (1961) Total removal of recurrent acoustic tumors. J Neurosurg 18:804-810 Rhoton AL Jr (1976) Microsurgical removal of acoustic neuromas. Surg Neurol 6:211-219 Rhoton AL Jr (1974) Microsurgery of the internal acoustic meatus. Surg Neurol 2:311-318 Rhoton AL Jr (1979) The suboccipital approach to removal of acoustic neuromas. Head Neck Surg 1:313-333 Rhoton AL Jr, Kobayashi S, Hollinshead WH (1968) Nervus intermedius. J Neurosurg 29:609-618 Rushworth RG, Sorby WA, Smith SF (1984) Acoustic neuroma in a child treated with the aid of preoperative arterial embolization. Case report. J Neurosurg 61:396-398 Samii M, Ohlemutz A (1981) Preservation of eighth cranial nerve in cerebello-pontine angle tumors. In: Samii M, Jannetta PJ (eds) The cranial nerves, Springer, Berlin Heidelberg New York, pp 586-590 Samii M (1981) Preservation and reconstruction of the facial nerve in the cerebellopontine angle. In: Samii M, Jannetta PJ (eds) The cranial nerves. Springer, Berlin Heidelberg New York, pp 438-^150 Sheptak PE, Jannetta PJ (1979) The two-stage excision of huge acoustic neurinomas. J Neurosurg 51:37-41 Shimizu H, Masuzawa H, Sano К (1979) Bilateral acoustic tumors: Its clinical features and surgical treatment. Neurol Med Chir (Tokyo) 19:623-627 Smith MFW, Clancy TP, Lang JS (1977) Conservation of hearing in acoustic neurilemmoma excision. Trans Am Acad Oph Oto-laryn 84:704-709 Smyth GD, Gordon DS, Campbell R, et al (1982) The facial nerve in acoustic neuroma surgery. J Laryngol Otol 96:335-346 Sterkers JM (1981) Retro-sigmoid approach for preservation of hearing in early acoustic neuroma surgery. In: Samii M, Jannetta PJ (eds) The cranial nerves. Springer, Berlin Heidelberg New York, pp 579-585 Sugita K, Kobayashi S, Mutsuga N, et al (1979) Microsurgery for acoustic neurinoma-lateral position and preservation of facial and cochlear nerves. Neurol Med Chir (Tokyo) 19:637-641 Sugita K, Kobayashi S (1982) Technical and instrumental improvements in the surgical treatment of acoustic neurinomas. J Neurosurg 57:747-752 Tarlov E (1980) Total one-stage suboccipital microsurgical removal of acoustic neuromas of all sizes. Surg Clin North Am 60:565-591 Thompson J (1976) Suboccipital removal of acoustic neuromas. Results of 125 operations. Acta Otolaryngol 81:406-414 Wanxing С (1981) Preservation of facial and acoustic nerves in the total removal of large and small acoustic tumors. Report of two cases. J Neurosurg 54:268-272 Wigand ME, Haid T, Berg M, et al (1981) Early diagnosis and transtemporal removal of small nerve VII and VIII tumors. In: Samii M, Jannetta PJ (eds) The cranial nerves. Springer, Berlin Heidelberg New York, pp 569-574 Yasargil MG, Fox JL (1979) The microsurgical approach to acoustic neurinomas. Surg Neurol 2:393-398 Yasargil MG, Smith RD, Gasser JC (1977) Microsurgical approach to acoustic neurinomas. In: Krayenbuhl H (ed) Advances and Technical Standards in Neurosurgery, Springer. Wien New York, pp. 93-129 Zlotnik EL Sklyut I A. Smeyanovich AF. et al (1979) Total removal of acoustic neurinomas. J Neurosurg 50:170-173

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