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Atlas of Neurosurgical Anatomy

John L. Fox

Atlas of Neurosurgical Anatomy The Pterional Perspective With a Contribution by Bengt Ljunggren Illustrated by David M. Klemm

With 171 Illustrations in 329 Parts, 133 in Full Color

Springer-Verlag New York Berlin Heidelberg London Paris Tokyo

JNtN L. Fox, M.D. Clinical Professor of Surgery. Division of Neurosurgery, Uni"ersity of Nebraska Medical Center, Omaha, NE68105, USA H ENGT LJUNGGREN, M.D.

Professor. Department of Neurosurgery, Uni,'e rsity Hospital, Uni,'c rsity of Lund, 22185 Lund,Sweden

Illttilmtor D AV ID M.

K L EMM

Medical lIIustralOr. Ed ucational l\ledia Production and Services. GeorgelOwn University Medical Center, Washington, DC 20007, USA Portions of the wor k on this atlas were carried OUI by Dr. J. L. Fox at the following institutions: Universi ty of Zurich, Zurich, Swiuerland (1973-1974); West Virginia University Med· ical Center. Morgantown. West Virginia (1975-1982); King Faisal Specialist Hospital and Research Centre, Ri yadh, Saud i Arabia (1983-1985); Georgetown Unil'ersity Medical Center, Washington. D.C. (1985-1987); and University of Nebras ka 1-.ledica l Center. Omaha, Nebraska (1987 -1988). The senior author is grateful for their support in this academic en· d eavor.

On IM/TQnl coveT: Fig. 7. 13/p. 138. Library of Congress Cataloging-in-Publication Data Fox, J ohn L., 1934Atlas of neurosurgical anatomy: the plerional perspective f J ohn L. Fox with a contribution by Hengl Ljunggren ; illustrated by David M. Klemm. p. cm. Includ es bibliographies and index. \. Brain-Anatomy-Atlases. 2. Brain-Surgery- Atlases. [. Ljunggren, SengI. II. Title. [DNLM: !. Nervous Syslem-anatomy & histology-atlases. 2. Nen'ous System-surgery-atlases. WL 17 F792aJ QM455. F65 1989 61 1.8-dcl9 DNLMIDLC 88·39319 Printed on add·free paper o3:l 1989 by Springer-Verlag New \orlo: Inc. Softcovcr repri nt oTlllc hardcover 1st edition 1989 All rights reserved. This work may not be trans lated or copied in wbole or in pan without the writlen permission or the publisher (Springer-Verlag, 175 Fifth A"enue, New York, NY 100 [0. USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or d issimilar methodology now known or hereafte r de· "e1oped is forbidden. The use of general descriptive names, trade names, trademarks, etc. in this publication, even if the former are not especiaJl ~' identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone. While the advice and information in this book are believed to be trueand accurate althe date of going to press, neilher the authors nor the editors nor the publisher can acce pt any legal responsibility for any errors or omissions that may be made. The publisher makes no ,,'ar· ranty, express or implied. wi th respect to the material contained herein.

Typeset, printed, and bound by Universitatsdruckerei H. Sturtz AG. Wunburg, Federal Republic of Germany.

9 8 765 4 3 2 1 e-[SBN-1 3: 978-1-4613-8823-4 lSBN- 13: 978-1-4613-8825-8 00[: 10. 1007/978-1-46 13-8823·4

Dedicated to James Winston Watts, M.D., Professor Emeritus, Department of Neurological Surgery, George Washington University Medical Cente'r, Washington, D.C.

Foreword

During the past 15 years, several publications on neurosurgical techniques, often with special emphasis on surgical anatomy. have appeared in the literature. Howevel; this book by J ohn L. Fox goes far beyond an ordinary effort. This extraordinary work, Allas of Neurosurgical Anat011o/: The Pte1'ional Perspective, has its or igins in the author's many years of devotion, exhaustive labors, and experience as a teacher in the operating theater (to wh ich his many residents will attest). This surgeon, born in Billings, Montana, in the ycar of 1934, authored one of his first publications as a senior resident in 1964. The tide, " Differentiation of Aneurysm from Infundibulum of the Posterior Communicating Artery," presaged his future recognition as an intracran ial aneu rysm surgeon. Now Professor Fox is known throug hout the world not only for h is many publications on su bjects in neuroscience and clinical neurosurgery, but also for his teaching methods, which utilize both television demonstrations a nd color slides of live neurosurgical anatomy in realistic depth and clarity. Such talents as a teacher have led J ohn Fox to be called forth as an instructor and lecturer in many neurosurgical seminars and courses both here and abroad, East a nd West. His presentations with color photographs showi ng true visual images now are captured with perfection in this atlas. Such photographs, with accompanying instructions and descriptions on approaches to aneurysms and tumors, have left a prominent and lasting impression on everyone who has had the opportunity to attend his lectures. This book gives us images in livin g color, images curremly unsurpassed by any other work and well illustrated as the su rgeon actually sees them. The excellent accompanying and instructive drawings help carry the reader and observer step by step through the intricacies of cisternal anatomy and pathways of intracranial surgery. This publication is divided into e ight chapters, starti ng with the history of the pterional approach in neurosurgery. The inclusion of this interesting and instructive chapter gives us an added evolutionary insight. It is co-authored by Professor Bengt Ljunggren, whose interest and expertise in neurosurgical history and aneurysm surgery are well known. Professor Ljunggren, from the University Hospital of Lund in Sweden, fascinates the reader with his accounts of the early evolution of techniques for turning the cranial fl ap. The next three chaplers by Dr. Fox carry us through in strumentation and positioning, photographic technique, and cranial anatomy. His final four chapters take us from the sylvian fissure into and thro ugh

VIII

Foreword

the carotid, chiasmatic, and inter pedu ncu lar cisterns and their en virons. Such anatomy could never be so well illustrated before the days of the operating microscope. I have followed the career of john Fox for nearly 30 years, includ ing the time since his days as a student and resident at the George Washington Un iversity Medical Cen ter through his appointment as Professor of Neurological Surgery at the same institution in Washington, D.C., on Ju ly I, 1974. Subseque nt yea rs have shown that Professor Fox not only is singularly and eminently qualified and gifted as an author of such an atlas, but also continues to have the energy and drive to give future students, anatomists, neurologists, and neu rosu rgeons such a lasting work on intracranial surgery via the pterional perspecti ve. L UDW IG

G. K EMPE, M.D.

Professor of Neurological Su rgery and Research Professor of Anatomy University of South Carolina Charleston , South Carolina

Preface

After completing a three-volume book entitled inlmcranial Aneurysms published by Springer-Verlag in 1983, this authorcomin ued to compile a set of surgical photographic slides that served well for teaching anatomy at neurosurgical rounds, meetings, and workshops. But preservation of these images for futu re sLUden ls required their publication in a more permanent form. The plerional approach to cenain imracranial problems is being used with increasing frequency, and the photographs presented here give us the plerionai, or frontolatera l, perspective - a perspective that is turned upside-down and obliqued in comparison with most standard anatomical illustrations. Yet, th is is the vlew as seen by the neurosurgeon. For ease of comparison, all photOgraphs are oriemed as if a right-sided operation is being performed. In one sense, this atlas becomes "volume 4" of Intracmnial Aneurysms. However, em phasis is on live anatomy and its variations rather than on pathology. h is for this reason that this author omitted cases with basal tumors, for such masses often distort and compress the vessels and cranial nerves beyond dear recogni tion . The earthly finality of death is mitigated by the deeds one does during his or her life. One then leaves behind the results of interaction with others. As physicians we hope to have mostly benefined our patients. Sometimes we fail. This atlas nOl only is in memory of those failures. but also is a photographic epitaph of some of those very patiems, however few in number. For the many patients who survive the neurosurgeon's hand and return home to family, the surgeon can gain more than any ephemeral fame, fonune , or feeling of "well done." The neurosurgeon, more importantly, can be both a catalyst inspiring younger surgeons to greater heights and a teacher leaving behind works upon which others can build. The author, the con tributor to the chapter on history, and the artist hope that this atlas will serve such lasting purposes. J owe a debt of gratitude to my friend and colleague Professor Bengt Ljunggren at the Departmem of Neurosurgery of the University Hospital, The University of Lund, Sweden. Begin ning with the 1889 work of the German surgeon Wilhelm Wagner. Professor Ljunggren contributes a vital perspective to the history in Chapter 1. Special credit is due to David M. Klemm , medical ill ustraLOr at the Georgetown University Medical Cemer in Washington , D.C., where I carried out part of the work on this book. He drew and labeled all the illustrations that accompany the color photographs. JOHN

L. Fox

Contents

Foreword by LUDWIG C. KEMPE. Preface . . . . . . . . .

VII

IX

H istory of the Pterional Approach and JOHN L. Fox

BENGT LJUNCGREN

2

Instrumentation and Positioning

11

3

Photographic Technique . . .

33

4

Cranial Anatomy and the Cranial Flap

37

5 The S),lvian Fissure

55

6 The Carotid Cistern and Environs.

93

7 The Chiasmatic Cistern and Environs

123

8 The Ambient and I nterpeduncular Cisterns

165

Ind ex

20 1

1 History of the Pterional Approach BENGT LJUNGGREN

Introduction Many surgical a pproaches have been proposed in order to facilitate exposure of lesions in the skull-base region wi th a minimum of brain retraction [I, 3, 12, 15, 18, 19,24,29,32-34,37, 39, 40, 49]. The pterional a pproach [0 th e circle of Willis and its environs is routinely used by many surgeons. A pterional approach implies that a small skull flap is raised with the pterion (Creek pterion, wing [ II ]) - the craniometric point located undern eath the tcmporalis muscle and form ed by the junction of the fronta l, parietal , and te mporal bones with the g reat sphe noid wi ng bone - in the center of the base of the flap (Fig. 1.1 ). Additional drillin g down of the sphe noid ridge allows a low basal exposure along the skull base. Equipped with

Fig. 1.1. Close-u p view of left

side of dry skull with sutures between the frontal (F), parietal (P), temporal (1),

sphenoidal (S), and zygomatic (l) bones outlined by black ink.

and JOH N L. Fox

today's microsurgical instrume nts, the ne u rosu rgeon finds that the pterional approach to skull-base lesions is a more natural and easier procedure than earl ier-day operations. Yet, there is a fascinating hiSlOrica l background over the last 100 years, that form s the basis o f the present-day pterional approach. There are several pioneers who made mo numental contributions to the development of this access to deep-seated cran ial-base lesions.

Wilhelm Wagner and His Osteoplastic Method followin g studies on human cadavers for several years, Wilhelm Wagner (1848 -1900) became the first su rgeon in the world to raise a

2

I. HislOry of the Pterional Ap proach

bone flap (temporal in site) out of the cranial vault in a living person , kee p it attached to the overlying soft tissue (perioste um, tempora l muscle, and scalp), a nd then replace the fla p (after evacuation of a la rge epidu ral hematoma) [4, 44]. Wagner used hammer and chisel to raise the bone flap. The patient, a 27year-old man with skull-base frac tures a nd the clinical picture of increasin g intracranial pressure, underwent su rgery on the second day fol lowing a seve re head injury. He was in a poor condition p rior to the ope ratio n. Following evacuation of the hematoma, it was appa rent thal the intracranial pressure had become normalized , bUl the patient did not recove r a nd d ied 24 hou rs after surger y. At a uto psy Wagne r fou nd no signs of di st urbed nutrition in the te mporal, omega-sha ped fl ap that he had raised to allow e vacuation of the now-absent hematoma. He concluded that his osteoplastic method was an excellen t procedu re that resulted in a good ex posure of lace rations of the middle me ningeal artery in the middle cranial fossa. He also suggested that his osteoplastic method could be used to ex plore and resect other intracra nial lesions such as brain abscesses, e pile ptic scars, a nd brai n tumors [44]. Two years later (1891 ) Wagne r rightly claimed priority for the introduction of the use of the above-described , intraoperative osteoplastic bone flap to ex plore intracran ial lesions. He e mphasized that such fl aps appea red to heal quickly and withou t compl ications when attachme nt to the soft tissue was retained during surgery [45]: "The osteoplastic method of trepanation is no morc difficult or da nge r. ous than an explorative laparotomy. " In 1895 Wagner publi shed two cases of success ful evacuation of e pidural hematomas throu gh his then innovative osteoplastic procedure. In this paper [46) he again e mphasi;r.ed th e adva ntages associated with tempora ry resect ion of a large bone fl ap for cx ploration of the middle meningeal bra nches. In 1909 Ha rvey Cushing [5] described Wagne r's original procedure to explore and decompress cerebral lll mors, which otherwise proved to be inoperable, using" the usua l osteoplastic method of exploration ." He summarized [5]: '~ n osteoplastic resection, whatever tools may be e mployed , has doubtless come to be made, in the hands of all , unde r

some form of tourniquet, with the omegasha ped fl ap broken off across the thin squamous wing of the temporal bone." Wagner was a self-educated surgeon who, like his great conte mporary colleague from Berlin , Ernst von Bergman n ( 1 836 ~ 1907), had been in volved in the Fra nco- Prussion War in 1870. He devo ted his life to working in the local hospi tal of Kon igshoue, a small tow n in a mining d istrict in Upper Silesia, which in 1880 cou nted 27,600 in habitan ts. Silesia at this time was incorporated into the newly founded German Re ich. In this small place Wagner became a n absolute master surgeon, and like von Be rgmann he ex hibited a pa rticula r interest in cran ial and spina l surgery. While von Bergmann strongly objected to the use of o pening the skull with chisel a nd mallet. this was the technique superbly practiced by Wagner. T he lattcr also publ ished important contributions concerning the operative management of complicated skull fractlll"es [4 3] a nd on fracture di slocations in the cervical spine [47]. His re port on the cli nical diagnosis a nd o perative evacuation of e pidural he ma tomas is a masterpiece [46] . The same ca n be said of the remarkable volume, " Die Verletzu ngen der Wirbelsaule und des Rockenma rks" [47] whic h he published in collaboration with his colleague Stolpe r from nearby Bresla u (Wroclav). Despi te a heavy clinical dail), practice, he not only kept abreast with the surgical litera tu re of the lim e but also followed the litera tu re in general med ici ne and other related bra nches . Wagner was beloved by his patie nts, for he rad iated secu rity a nd goodness and was widely recognized in the whole of Silesia not onl y for his supreme skill but also for his vast medical knowledge and his good reo sui ts in the treatment of nonsurgical d iseases.

Crania] Saws In 1891 Professor (" professeur a la Facuitc libre") J ean Toison from Lille in France repon ed on his use of a chain saw to divide the bone between burr holes from within outward to facilitate raising of osteoplastic skull fl aps [38]. This saw could replace ha mme r and chisels previously used in o pening the cranial va ult. I n his pape r Toison paid much attention to Wagner (already in his title) as the true

de Martel's Skull Trephine and Metal Gu ide

3

pionee r behind the revolutionizing method of Heidelberg, Cermany, Kocher from Bern, raising cranial flaps. He described Wagne r's Swi tzerla nd , Simpson from Edinburgh, Scot" historical con tribution which he first per- land , and Sklifassowsk i from SL Petersburg, formed on a li vin g human on October 1st Russia. In his pioneer pa per Oba linski gives 1889" and continu ed [38], .. Aussi la nou vell e credit to Karl Dahlgren (1864 - 1924), a methode opCraloire inauguree par W Wagne r Swed ish pioneer who, in 1896, had designed a (de Konigshuue) qu i permetde creer une vaste new bone-cutting forceps fo r making linear ouverture a la boite ossellse du crane et de re- cuts in the skull bone and which cut from the fermer, a la fin de I'ope ration, avec de I'os, inside out [6]. With the increasing interest in J'ouvertu re rendue tcmporaire de la trepana- cranial surgery in the first decade of this cention, constilUe-t-ci le un grand progres chirur- tury. the Cigli saw later became recognized also gical. Ce chirurgie n a donne a celle methode in the United States by Harvey Cushing, who operatoire Ie nOIll de rcseClion temporaire du adopted the use of this simplc instrument to dicrane . ., vide the skull bone betwee n two burr holes Toison's saw was fairl y cl umsy and was there- [36]. fore not much used [48]. T hree years later (1894) Leonardo Gigli from Florence, Italy, dede Martel's Skull Trephine and scribed his simple yet clever instrumem, a wire saw to divide bone between two open ings, This Metal Guide tool has come to bea r his name, being called the Gigli saw [ 16, 17). Origina lly, Gigli imemed his In 1908 Count Thierry de Manel (1875- 1940) wire saw to facilit.·ue sym physiotomy in obstetri- presented lhe perfect solution to the rest of the cal surgery. He fini shed his origi nal re port {16], problem of trephinin g wi thout risk of producemphasizing that one dozen saws could be or- in g intracranial damage. As a bo)' de Martel dered from the Hermann HarLel Compa ny in was alread y very inquisitive and enjoyed taking Breslau at the price of 3 German marks plus mechanical things apart to learn how the), op40 pfe nnig for shipping com to an)' forei gn erated [31]. Frequently he dissected the fowl country. He also added that chiefs of clinics being pre pared in the kitchen, and he bought could obta in free samples by just sending in a a skeleton that he displayed as an amiable comrequest. pan ion, de Martel, a dcscenda nt of the Professor Alfred Obalinski from the Jagicl- Mirabeau fa mil)' who played an olltstanding Ionian University of Cracow in Galicia (the role in the French Revolution, was an aristocrat haven of Polish culturc at the time, although fully conscious of his ancestry. At fi rst he was under the government of Vienna) had in- enrolled in a school for the training of entended to describe the use of the Gigli saw for gi neers and later was trained by several French cranial trepanations at the Imernational Con- master surgeons . He beca me especially ingress in Moscow in August 1897. However, he terested in neurosurgical instrumentation . At was prevemed from going and instead pub- the age of 33 he published an article [28] delished his innovative a pplication in the Cen- scri bing two new neurosu rgical instruments. tro/blatt [il r Chimrgie that same ),ea r [30]. In his Today, 80 ),ears later, both are in dail y use by paper Obalinski stated that it had occurred to many thousands of neurosurgeons all over the him that by using a slightly bcnded cannu la as world. In his milestone paper the two instruan inserter, the fl ex ible Gigli saw was ideal for ments he described were (a) a motor-driven introduction between burr holes. He em- tre phine equipped with an automatic disenphasized that the use o f the Gigli saw permits gaging gear that stopped the trephine as soon the safest method of dividing the skull bone as it has penetrated the skull and (b) the metal from the inside to the outside without th e type gu ide for the introduClion of the Gigli saw beof trauma usually seen from the use o f ham- tween separate burr holes. mer and chisel [30]. In Moscow, Emile Doyen When in Paris, de Martel presented his new from Paris demonstrated his own method for automatic trephine, but it was received with deperforming a cra niectomy in front of many rision. He then performed a demonstration prominent professors of surger)" including lI sing a dried skull with a balloon 0 11 the inside von Bergmann fro m Berli n, Czerny from as an im itaLion of the dura mater. With his au-

4

I. History of the Pterional Approach

Fig. 1.2. The " hypop hyseal 0' a pproach of Heuer and Dand y. From Dandy WE (1936) The braill , in Lewis D (cd): WF Prior, P roc/ice of SUrgfly, vol 12.

[71 .

LOmatic trephine he drilled a hole in this sk ull without puncturing the balloon a nd commented [31 ], "Well, as yo u call see, this treph ine can be operated by a n imbecile" ("ct bien comme valis voycz, Messieurs, cc trepan pellt manie meme par un imbecile"). American neurosurgeons were even more reluctant to accept de Mart.e1's e lectric dri ll. By the late 1930$ it was used routinely in Sca ndinavia, France, Germany, a nd Central Europe. Yet in Boston in 1948 its lise was rejected even at the Massachuseus General Hospital. The burr holes were done ma nuall y (and laboriously!) with Hudson drills. It was said that electric drills were not used because Cushing had once stated that such drills caused too much vibration transmitted to the brain (Bakay L, personal communication, 1974).

de Martel a lso had designed a hemostatic forceps, a self-reta ining cerebral retractor, and a specia l surgical chair supporting the patient for operatin g on posterior fossa tumors with the patient in the siuing position. He was the pioneer neurosurgeon in France who fou ght a nd overcame the difficulties of blood loss and inadequate posterior Fossa visualization common to neurosu r ger y during the first qua rter of this centu ry. He had lost his only son in World War I. In 1938, at the Annual Cong ress of the De utsche Gesellschaft fUr Chirurgie. de Martel gave an impassioned speech about the necessity of continued friend ship between French and German su rgeons, a speech that was followed by thunderous applause. Two years later, on Ju ne 14, 1940, as Hitler's troops occupied Paris, de Martel commited suicide [31].

Hagerstown, Maryland, pp 145, 583-585. Reprinted with permission of Practice of Surgery Ltd .

From a "Hypophyseal" to a More Pterional Approach

5

Fig. 1.3. Another view of the "concealed incision" (behind the hairline) of Heuer and Dandy. From Dand y WE (1936) The brain, in Lewis D (ed): WF

Prior, Practice of Surgery, \'01 12. Hagerstown, Mary· land, pp \45.583-585. Reprinted with permission of Practice of Surgery Ltd . [7].

From a .. H ypophyseaJ" to a More Pterional Approach

In 1962 George "{ayes, one of Dandy'S stud ents and former chief of neurosurgery at The Walter Reed Army Medical Center 111 Washington, D.C., briefly illustrated his frontotemporal approach in a publication with Slocum [20]. One of their figures showed " ... the visualization of an aneurysm of the anterior communicating artery as exposed through a small Dandy pituitary lype o f flap. " Hayes and his colleagues commonly used this approach to the base of the brain (Hayes GJ , personal com munication, 1974). In 1963, before the period of microneurosurgery, Lougheed and co-workers [27] stated that their operative procedure was car· ried out "through a fronto temporal bone flap

In 1918 Waller Dandy took the liberty to report for George Heuer, one of his younger colleagues, on a " hypophyseal" a pproach to pituitary tumo rs [23]. Heuer later described this approach in more detail and used it for selIaI' and suprasellar LUmors [21, 22]. In the 1940s Dandy made some modifications [7 - 10] and this lype of cranial opening became popularly known in the United States as the " Dandy nap " (Figs. 1.2-1.4). This hypophyseal approach used a skin incision concealed behind the hairline.

L History of the Plerional Approach

6

A.

I

OpenonS .r.·chnldl ~r ,

betw~~

optic n. ad

GJrotid L

;-

Fig. 1.4. Dandy's approach to an intracranial aneurysm. Fro m Dandy WE (1944 , reprilHcd 1969) Intracranial Arterial Aneurysms. New York, Hafner.

Ski n irn:: i$ion

Fig. 1.5. The ptcrional craniotOmy flap as o utlined by Kempe. From Kempe LG [25] .

)mal\cr Copyright ]944 by Comstock Publishing Company, Inc. Re printed by permission of Cornell University Press [9].

with removal o f the pterion and a bit of the outer third of the lesser wing ohhe sphenoid. " Ludwig Kempe. who succeeded Hayes at T he Walter Reed Army Medical Ce nter, Ilicely illustrated various features of the plcrional approach (Fig. 1.5) in his 1968 two-volume alias, OPerative Neurosurgery [25] . Of interest is the description given to the critical burr hole placed at the junction of the temporal line, the zygoma tic process of the frontal bone, and the orbital ridge. At The Walter Reed Army Hospital this became known as the " psychopathic poi m " [14, 26, 4 1], probabl y in reference to the disposition of the surgeon should the residem fail to place the burr hole correctly! Subseque mly Fox learned the pterionaltcchnique of cran ial ope ning [ 13, 14] by observing or assisting George Hayes, Lud wig Kempe, and Hugo Rizzoli , Dand y'S last neurosurgical reside m o Barnes Woodhall, a nother of Da ndy'S trainees, simila r! y used the pte rional a pproach at Duke University (Woodhall B, personal communicatio n, 1980). With the imroduction of microncurosurg ical techniques, Gazi Ya~argil illustrated his

Bibliography Fig. 1.6. Diagram of skull with area usually included in a pterional flap although modified by various surgeons. From Fox JL [14].

microtechnical pterional approach [51, 54], which was a refinement of his 1969 frontotemporal descri ption [50]. He emphasized the sma ll , low basal expos ure by drilling down the sphenoid bone. At that time the basic difference between his published description and that of Ke mpe's [25] was the use of microtechnique, sphenoid bone dri lling, a wider opening of the sylvian fi ssu re, the placement of the posterior burr holes more a nteriorly (making it a frolHos phenoidal craniotomy), a nd the avoidance of retraction on the temporallobe [54]. Ya~argil and co-workers used the pterional approach for lesions in the interpeduncular cistern [52], in which situation the posterior clinoid process is a landmark that, on occasion, may hinder a clear ex posure [35]. The skin incision likewise has changed with the needs and preference ofth e individual surgeon. Dand y's original incision is illustrated in Figs. 1. 2 through 1.4. Kempe's incision (Fig. 1.5) permitted greater exposure of the temporalis mu scle as well as a more basal exposure . Various surgeons at times extend the fronta l limb a shon distance into the skin of the forehead above the junction of the medial twO thirds and lateral one third of the eyebrow. This might permit a shorter scal p incision, but itdid make part of the surgical sca r visible after hair regrowth . Ya~arg il 's incision was longer but re ma ined concealed beh ind the hairli ne while descending low enough to perm it a lower, basal a pproach [53, 54]. The pterional approaches at times can inju re the fromalis

7

"

branches of the facial nerve, a point of recent discussion [2, 55]. Throughout the years neurological surgeons have altered and modified the a pproach to the middle fossa and sellar region. In one form or anOlher the pterion has been incorporated within the reflected bone fl ap in modifications of the "pterional fl a p " (Fig. 1.6). Its evolution from the Heuer-Dand y flap to the Hayes- Kempe flap posteriorly and basally and then to the Yaprgi l nap a nteriorl y a nd basall y has been accompanied by parallel advances in imaging, anesthesia, magn ification, lighting, retraction, instrumentation, and intraoperative e nergy transfer (by laser, ultrasound, electrocautery, and the like). The pterional approach is now finding its place as an important surgical route to t he circle of Wi llis and itsenvirons. T he pioneers who laid the fund amental cornerstones to this procedure include Wilhe lm Wagner, Leonardo Gigli, Alfred Obali nski, Thierry de Martel , George He uer, and Walter Dand y. T hese are the men of years long past to be r emembered by all ne urosurgeons who today regard the pterional approach to the skull base as a n elementary and most obvious and fund a me ntal principle.

Bibliography 1. AI-Mefty 0 (1987) Supraorbital-ptcrional approach to skull base Icsions. Neurosurgery 21: 474-477

2. Aoki N (1987) Incision offacial nerve bra nch al

8

I. History of the Plerionai Approach

aneurysm surgery. (Leuer to the Editor) J Neurosurg 66: 482 3. Brock M, Dietz H (1978) The small frontolateral approach for the microsurgical treatment of intracranial aneurysms. Neu rochirurgia (Stultg) 21: 185- 191 4. Buchfeldcr M, Lju nggren B (1988) Wilhelm Wagner (1848- 1900). Surg Neural, in press 5. Cushing H (1909) A method of combiningexploratio n and decompression for cerebral tumors which prove to be inoperable. Surg Gynecol Obstet 9: 1-5 6. Dahlgren K (1896) Ein neues Trepanationsinstrument. Centralbl Chir 23: 217 -220 7. Dandy ,-\,IE (\936) The brain, in Lewis 0 (ed): PracliceofSurgery, Hagerstown, Md, WIs more light. 8. Turn off bright lights in opcr.lting room (bener conu'ast; surgeon's pupils arc d il'lIcn. rcrruiring less light ). 9. ~ I ake use of inlernal rencctions in surgical wound; a,-oid rencclions back in to the microscope. 10_ Remo" e black paint border aruund glass light dencctor behind objecti ve lens (present in some microscopes). II. Usc 30-70 beam splitrer (70% to side arms. onl), 30% (0 surgeon) inslead of 50-50 beam spliuer. 12. Use greater magnification in e)'cpicces. thercby requ iri n~ less rnagn.i fic3tion (hence less light loss) inside mrr.rosral lobe retractor; unc, uncus; 3, ocu lomotor nerve; fe, tentor ial margin.

186

8. The Ambient and Intt:rpWuncular Cisterns

Fig. 8.20. Another case with view of right lateral portion o f interpeduncu lar cistern after remm'al of mcmbr.mc of Liliequisl. Notc how oculomotor nerve (J) gathers together from a broad band exiting the midbrain. pons. Rostral pons; sea, su perior cerebellar artery; 00, basilar artery near its bifu rcation: Ie, margin of te ntori um; /1, temporal lobe; col, cotlOno id ; rei, retractor: p-2, P·2 artery; p, perforators; 111-2. M-2 artery : mol, M- l artery; ot, optic tract; a-I.

A-I artery; 2, optic ne rve; mem, membrane of Liliequisl (anterior re n ectioll around pituitary stalk); ial, internal carotid artery; pea, posterior communicating artery; aciUl, anterior choroidal artery; pol, P_I artery. Reproduced by permission from Fox JL ( 1985) Microsurgical exposure ofvertebrobasilar aneurysms, in Rand RW (cd): MicrmleUrQS1I1gery, cd 3. Sf Louis, CV Mosby Co, pp 589-599 [3].

Anatomy

Fig. 8.21 . Same case as in Fig. 8.20. Internal carotid artery (ica ), middle cerebral artery (m-I), and posteriorcomm unicating artery (pea) retracted med ially by na rrow retractor (rtt ) to expose ceme r o r imerped uncu la r cistern contai ning aneurysm (an) at bi rurcation or basilar artery (ba). Except at its base, aneurysm is covcred by a carpet or fi brin. p-I. Left (loP) and rig ht (bottom) P- l arteries;sca, right su perior cerebellar a rtery: Ie, margin or tentorium : J,

187

oculomOlOr nen'C; pons. rostral pons; p. one o r several anterior thalamic perrorators rrom postcrior com municaling art.ery; 2. optic nerve; /le, anterior clinoid process:pc, posterior clinoid process. Reprod uced by permission rrom Fox J L (1985) Microneurosu rgical exposure or vertebrobasilar ane urysms. in Ra nd RW (cd): M icrotll'UfOsmgery,ed 3. 51 Lou is. CV Mosby Co, pp 589 - 599 [3).

188

8. The Ambient and Interpeduncular Cisterns

cot

Fig. 8.22. Example of ventral surface of basilar arlcry (ha) in interpeduncu lar cistern flanked by oculomotor nerves (3) . The membrane of Liliequist has been removed. t-sea, Left superior cerebellar aftef),; r-sea, right superior cerebellar artery; ], right and left oculomotor nerves; lie, right posterior clinoid process; pol, left and right P-l arteries; I),

posterior thalamic perforators from pol; *, base of basilar tip aneurysm; ica, internal carotid artery; ret, rClraClOr displacing iea bifurcation medially; aelia, anterior choroidal artery; fl. frontal lobe; col, cottonoid; /l-ret, right temporal lobe re tractor; crossed arrow, malleable dip on caudal end of severed right posterior communicating artery. From Fox [2J.

Anatomy

Fig. 8.23'. Another example of ventral surface of bifurcafion oflhe basilar artery (bba) in Ililerpeduncular cistern between both oculomotor nerves (3). prd, Left (opposite) peduncle (pyramidal tract) of mid brain ;sca. lcft superior cerebellar artery ; bo. basi-

189

iiiI' artery; Ie, margin oftentorium;p-l, right and left pol arteries; all, base of aneurysm at tip of basilar artery; fl-rel, frontal lobe retractor; Col, cottonoids; 11rtt, temporal lobe retractor. From Fox [2].

8. The Ambient and Interpeduncular Cisterns

190

,.1 '01

Fig. 8.24. Another case illustrating anatomy at j unction o f carotid , interpeduncular, and ambient cisterns after removal of arachnoid membrane of Lilicquist. rei, Retractor displacing internal carotid arte l")' medially; CQl, cou onoids; p, perforators; mol, M- I artery;aw, duplicated anter ior temporal artery;

v, veins; pons, rostral pons;), oculomotor nerve;sco, superior cerebellar artery; 00, basilar artery; pea, posterior communicating artery in carotid cistern; p-2, P-2 artery emering wing of ambient cistern be· tween pons and lemporallobe;p-J, pol artery going medially in interpeduncular cistern. From Fox [2J.

Ana{Qmy

191

". co.

J

/

r )

I

Fig. 8.25. Same case as in Fig. 8.24. View of ventral aspect of bifurcation of basilar artery (boo) and inter· peduncular cistern between oculomO{Qr nerves (3). 00, Basilar artery: sea. right superior cerebellar artery; p-l, right (labeled twice) and lef! P_I arteries; p2, right P-2 arter y; pons, rostral pons; v, veins; ala, an-

terior temporal artery; mol. M-I artery; col, (ot{Qnoid; rel, retra({Qr on ica; p, posterior thalamic perforators; i-sea, left superior cerebellar artery; an, aneurysm of tip of basilar artery;crossed arrow, caudal end of severed posterior commu nicating artery (with malleable dips on it). From Fox [2] .

192

8. The Ambient and Interpeduncular Cisterns

Fig. 8.26. Another example of anatomy at confluence of carotid. lllle rpeduncular, and ambiem cislerns. cau-an, Dura of cavernous si nus containing giant internal carotid artery aneurysm; ica, internal carotid artery exiting from C3\'CrnOUS sinus; 00, basilar ancry; $la, superior cerebellar artery: J, OCU lO ll1 010 l' nerve entering cavernous sinus; pmlJ,

rostral pons; p-2. P-2 artery; crossed arrow points to posterior communicating artery hidden by internal carotid artery; unc, uncus; p. anterior thalamic perforalOr ; acha, anterior choroidal artery; *, bifurcation of internal carotid artery; col, cOllOnoids; fl, froma l lobc; QI, right optic tract; II, lamina terminalis; eli, o ptic chiasm; 2. both optic ne rves. t'rom Fox [2).

193

Anatomy

1I".t

00'

fig. 8.27. A vicw through carotid a nd interpeduncular cistel'lls into prepoilline cistern anterior to the pons (PO"s). ll·rtt , Temporal lobe retractor; col, cot· tonoid; fl·ret, fro ntal lobe retractor; clp. shank of aneurysm clip on an 3mcriorcommunicating a rte ry ancurysm; a· l. A- I artcry; mol . M-l an ery; tmc,

uncus; sea, superior cerebellar anery; an, a neurysm of basilar arte ry (1M) at takeoff of amerior inferior cerebellar anery ; J, oculomotor nerve; pc. posterior cli noid process; ica. internal carotid artery. From Fox [2].

194

8. The Ambicni and Jnterpeduncular Cisterns

Fig. 8.28. Another case with view of carotid , interpeduncula r, and rostral prepontine cisterns. Ie, Ma rgin o f te ntorium ; mem, remainde r of membrane o f Lilicquisl (most removed): rti, temporal lobe retraeLOr ; pons, rostral pons; J, oculomotor ncn'c;jK. post-

crior clinoid process; ac, anterior clinoid process; ica, jlllcrnal carotid artery; 2, o ptic nCl've; QI. optic tract; a-I, A- I artery; m-l, M-I artery; p-2, P-2 artery;p- J. p. I artery; crossed arrou, origin of posterior communicating artery.

Anatomy

fig. 8.29. Same case as in ~ig. 8.28 with medial retraction (1"(/) of the internal carotid artery (ica). 2. Optic ne rve: ac, anterior clinoid process; pc, posterior clinoid process;p·l, left (obscured with blood) and right P- J arteries; " bifurcation of basilar artery; an, aneurysm of b.1silar artery at takeoff of hidden

195

right su pcrior cerebella r artery; ), oculomotOr nen'e entering cavernous sinus; POtU, rostral pons; p, perforator; p-2, right P-2 artery: pea, posterior communicating artel")'; m-l, M·J artel")'; 0-1, A- I artery; 01, optic tract.

196

8. The Ambient and Interpeduncular Cisterns

Fig. 8.30. Same case as in Figs. 8.28 and 8.29. View of bifurcation of basilar artery (boo) in center of imerpeduncular cistern. pol, Left and right po l arteries; J, ocu lo motor ncn"c; all, aneurysm at o rigi n of

superior cerebellar artery (sea); Ie, margin of tenLOriu m; pons. rostral pons; *, bifurcation of imernal carotid artery; ret, retractor displacing imernal carotid artery medially.

AnatOmy

Fig. 8.3 1. Another case, following arachnoid sheath of posterior communicating artery (pea) and iL" an· terior thalamic pe rforators (I) caudally toward inlerpeduncular cistern hidden behind membranc o f Lilic(IUist (mem). Ie, f\hrgin ofte nlOriull1 : ulle. uncus; If·rel, temporal lobe retractor: fl, fronta l lobe; PI', probe rctracting M-I artery (m-I) medially; 01, o ptic

197

tracl;jl-J'et, frontal lobe retractor; a-I, A-I artery; fl, lamina te n ninalis; cit, optic chiasm; iea, internal carotid artery: 011, aneurysm at origin o f posterior communicafing artcry; Gclla, amcrior choroidal artery passing under uncus toward choroid fissurc of lClllporallobe.

198

8. The Ambient and Interpeduncular Cisterns

Fig. 8.32. Same case as in Fig. 8.31 at higher magnificatio n to show anterior thalamic perforators (p) from postcfiorcommunicating artery (pea) and thei r ensheathi ng a rachnoid. ar, Thickened arachnoid

bands within envelope of arachnoid about perforators and posterior communicating artery; un" uncus of right tern poral lobe; adm , anterior choroidal artery; ica, interna l carotid artery; QI , o ptic tract.

AnalOmy

Fig.8.33. Same case as in Figs. 8.3 1 and 8.32. Arach noid membrane of Liliequ ist has becn dissected away. Note how pterional approach can gi\·c panoramic vicw of chiasmatic, lamina terminalis, carotid, ambielll, and interpeduncular cisterns. 2, Both optic nerves; eh, optic chiasm; It. lamina termi nalis; 01, right optic tract; a.-I, A-I artery; p, per-

199

forators ; m-J, M-l artery; m-2, M-2 artery; ar, arachnoid sheath; aeM, anterior choroidal artery; ita, internal carotid artery; an, aneurysm; pea, posterior communicating artery; 00, basilar artery; p- l , P-I artery; p-2, P-2 a rte ry:), oculomotor nerve ; sea, origin of right superior cerebellar artery.

200

8. T he Ambient and Interpeduncular Cisterns

Fig. 8.34. Another case illustrating bifurcation of basilar artery (boo) in interpeduncular cistern. I-sea, Left superior cerebellar artery; pc. posterior clinoid process; ), left (h idden in shadows) and right oculomotor nerves; v, vein; r-sea, or igin of right superior cerebellar artery; {1-J, right and le ft pol ar-

teries in interped uncular cistern; pea, posterior communicating artery; p-2, origin of right P·2 artery; p, perforators; Il-ret, temporal lobe retractor ; unc, uncus; mol, r.1- 1 artery; ot, optic tran; ha, artery of Heubncr;jl, frontal lobe; a-I, A- I artery; aCM, anterior choroidal artery; ica, internal carotid artery.

Index

A Abducens nerve, 171 Acoustic nerve, origi n of, 17 1 Adhesions arachnoid membra ne, 94 between fro ntal and te mporal lobes. 56, 71 carotid arlery aneurysm to ocu lomoto r nerve, 111 fron tal lobe to oplic tract, 10. Ambient ciste rn, 165-200 anatomy of, 172, 199 body of, 169 j unction with ca rotid and interpeduncular ciste rns. 169, 172, 190, 192 j unction wi th sylvian and chiasmatic cisterns, 169 Aneurys m anterior cere bral artery A- I, 92, 16 1 anle rior choroidal artery. 92. 108 at o rigin, 84, 115, 183 anterior communicating ar· lery, 124 , 132, 137, 139, 140, 143- 144, 193 hypothalamic perfo rators stuck to, 125, 149 basilar artery_ Stt Basilar aftery. aneurys m o f internal carotid artery. See Carotid artery, internal, a neurysm of middle cerebral arte ry M- I al bifurcation, 76-77 d ome in temporal lobe, 75 fl anked by tem poral and fro ntal M-2 arte ries, 7879

posterior cerebral an ery P- I, 120 posterior commun icati ng ar· tery, 11 4. 178 at o rigin. 11 5- 11 6, 183184,197 at superio r cerebellar artery origin , 180. 185, 196 Aqueduct of Sylvius, 166 Arachnoid , 156, 174- 175 anterior re fl ection at pituitary sta lk, 125, 186 between frontal and tem poral lobes, 72 sc\'e red by microscissors, 56,84 between left optic nerve and frolltallobe. 140 between optic nerves, 98-99. 102, 116, 132-134, 148, 160 coveri ng inte rnal carotid artery and o ptic ne rve, 53, 74 d iste nded by cerebrospinal fl uid , 56. 59 at inte rhemispheric fissu re, 144, 150, 153-155, 160 at pituitary stalk, 138, 169 surgica l opelling of, 57, 8788, 177 and sepa ration by fo rceps blades, 64-65, 67 at sylvia n fissure. 146 Arachnoid bands o r fibers, 57, 87.90-91, 11 7. 153 at anterior cerebral artery A- I, 84, 127, 16 1- 163 in arachnoid envelope of thalamic perfo rators and posterio r communicating

artery. 198 between hypothalamic perforators and o ptic tract, 81 between midd le cerebral arte ry branches, 56, 70-

73 between middle cerebral M- l artery and temporal lobe. 80 between sylvia n vessels and pia, 63 at illlernal carotid artery, 67. 11 6 at lamina terminalis cistern , 125.14 1 at o ptic nerve/carotid a rtery j u nctio n, 67 at posterio r communicating artery, 83 in subd ura l space, 56, 58, 60-6 1 at sylvian fissure base. 56, 65-66 Arachnoid membrane of Liliequist, 68-69, 93-94, 98100, 103- 104. 107, 111 112, 116. 11 8. 125, 134, 138, 141 , 146- 148, 15 1, 165- 166, 184 adhesions o f, 94 attachme nts of, 98 coloratio n o f. 97 medial portion of, 185 at pituita ry stalk, 125, 138. 147- 148, 186 reflection of, 98 removal of, 188 surgical opening o f. 177 th ickening after he morrhage. 170, 176, 182

202

Index

Arachno id sheath of posterior communicating artery. 176 o f thalam ic perforators, 120 from posterior communicating an ery. 172, 197-

198

B Basilar ane ry. 39, 44-45, 69, 84, 107, 114 , 152. 171 ,

177, 190,192,199 aneurysm of. 179 at anterior infe rior (erebel· lar artery takeoff. 193 at bifurcation, 82, 18018 1, 187 at superior cerebellar arteryorigin, 185, 195 at tip. 18S-189, 191 bifurcation of, 166. 168, 183, 195--196, 200 between oculomotor nerves, 19 1 medullary perforators from, 11 5 near bifurcation, 186 origin of superior cerebellar artery. 165. 175, 179 relation to dorsum sellae, 168 relation to third ventricle.

168

lip of, 165, 18 1 tru nk of. 183 ventral surface of at bi furcation, 189, 191 nan ked by ocu lomotor nerves, 188

Basilar vein of Rosenthal, 165, 174

Bone nap attached to temporalis muscle, 40, 49 frontotemporal, 39-40 sutures for reattachment of, 40, 49 Bone-removal instrume nts, 24 Bonewax, use of, 24 Bridging artery from anterior communicating artery to left A-I, 126, 162 to left A-2, 11 2, 126, 153154, 157 Bridging veins between temporal lobe and sphenoparietal sinus, 4 1, 56,

66,74 electrocoagulatio n of, 56, 68 BUTT holes, 40, 48, 50

C Carotid artery, internal, 52, 6 1, 65-66, 77, 91, 110- 112, 135, 140, 145, 150-153, 159, 162- 163, 166, 169, 174- 176, 179- 184,IS6ISS, 193- 195, 197- 198 aneurysm of, 89-90, 104, 160, 192, 199 ad hesion to ocu lomotor nerve, II I adhesion to temporal lobe,

100 adhesion to tentori um ,

101

at anterior cho roidal artery takeoff, 84 at bifurcation , 57,85. 112113, 121 , 156- 157 arachnoid bands on, 67 ,11 6 arachnoid co,"ering of, 53, 74 athe rosclerotic, 63, 80, 10 1102, 107, 147- 148 bifurcatwn of, 79, 81, 84, 134 , 153, 156- 158, 192. 196,200 branches of, 57, 79 exit from cavernous sinus,

192 lateral retraction of, 103 left, 106, 114, 117- 11 9, 138, 146-147 bifurcation of, 138 long, 95, 98--99, 102 medial retraction o f, 109 origi n of anterior choroidal artery, 95, 100, 104, 13'1, 144, 152, 183 origin of posterior communicating artery, 95, 98, 100-101 , 104-105, I I I, 134, 141-142, 144 , 152153, 179,184, 194 ostium of, 167 perforatOrs from , 11 3- 114 ,

158 to anterior perforated substance, 118 at bifurcation, 11 8, 185 hypo physeal, 95, 99, l iS, 120, 125, 138 hypothalamic, 8 1, 95, 102-

103, 106, 11 8, 148, 159,

179 thalamic, anterior, 95, 102- 103, 120,172, 179 relation to carotid cistern, 93 relation to posterior clinoid process, 96, 114- 115 unusual, 170, 178 relation to posterior communicating artery, 192 right, 106, 114 , l iS, 138, 146, 148 bifurcat ion of, 12 1, 139 short, 95, 100-10 I sympathetic fibers on , 96, 11 6 view 10 optic tract, 103 Carotid cistern , 93- 12 1, 123, 128, 14S, 152 analOmy of, 93-97, 162, 172, 199 exposure of, 52 j unction with ambient and interpeduncular cisterns, 172, 190, 192 structures in, 96 Cavernous sinus, 95, 98 internal carotid artery exit from , 192 oculomotor nerve in , 170,

174

e ntrance of, 192, 195 unusual veins in , 97, 11 8-- 119 Cerebellar artery. anterior inferior aneurysm at takeoff from basilar artery, 193 right, 171 Cerebellar artery, superior, 165, 166.170, 174 , 183, 190, 192- 193 aneurysm at origin o f, ISO, IS5, I96

branch of, 179 le ft , 114 , 17 1, ISO, 188-- 189, 191,200 origin from basilar artery, 165,175,179 rig ht, S2, li S, 17 1, 177, l SI, 187- ISS, 191 aneu rys m at takeoff from basilar artery, 195 origin of, 199,200 separated by oculomotor nerve, 186 Cerebellum, 166 middle peduncle of, 17 1

203

Index tentorium of. See Tentorium cerebelli vermis of, 169 Cerebral arteries, anterior, 124,

167 A- I artery, 77, 85, 91, 93- 94, 10 1, 11 0, 11 3- 115. 118, 120, 123, 124, 133-135, 178-179, 182, 193-195, 197, 199-200 aneurysm of, 92, 16 1 arachnoid band over, 84, 127, 161- 163 hypoplasia of, 125. 146147, 149 left, 11 9, 125, 126, 136140,143- 144,149- 157, 159- 160. 162- 163 bridging artery to anterIOr communicating artery, 127, 162 origi n of, 82-83. 100, 108. 11 7,176 perforators from, 57. 7980,82,84,92,106.141142, 161 - 163, 170, 184, 186, 199 relation to artery o f Heubner, 95 right. 125. 126, 136- 140, 143-144 , 150-163 j unction with right A-2,

11 2 transsylvian view of, 82-83 A-2 artery, 126, 156-157 and common tru nk for artery of Heubner and right fro ntopolar artery, 126, 15 1 left. 137. 139- 140, 144, 153- 158, 160 bridging artery from anterior communicating artery. 112, 126, 1 53~ 154, 157 origin of, 159. 163 rig ht, 120, 137. 139- 140, 143, 149. 153- 158, 160 j unctio n with anterior communicating artery, 144

ju nction with rig ht A- I ,

11 2 origin of, 163 accessory. 126, 156- 157 o rigin o f, 127. 160 in chiasmatic cistern, 55

Cerebral arteries, mid d le. 55 branches of, 56, 57,60,66, 70-71,75,86-90,133 M- I arte ry. 84-85, 93, 94, 118, 120, 123, 14 1- 142, 144, 162-163, 179,182, 193-195, 197, 199-200 aneurysm o f at bifurca tion, 76-77 dome in temporal lobe,

75 nan ked by temporal and frontal M-2 arteries, 78-79 deep in sylvian fissu re, 89 emering sylvian fissu re, 8 1 frontal artery from, 75, 89 left, 11 9 long, 67, 78 origin of, 82-83, 106, 108, 112- 11 3, 11 5, 117 perforators fro m, 57.798 1,89-92,125,1 46- 147, 170, 181, 184-187, 190191,200 short, 57, 79 transsylvian view of, 82-83 variations in, 57 , 75 M-2 artery, 83, 90,157, 185186,199 aneu rys ms at bi fu rcation at M- I.77 dee p branches of, 87 fronta l artery from, 61, 76, 80,88, 146 variations in, 57, 75 Cerebral arteries, posterior. 108-109, 166- 167 1'-1 artery, 175 , 179, 183, 185-186, 194 aneurysm of, 120 ascending. 169 course o f, 170, 172, 190 left, 17 1, 181, 187- 189, 191. 195-196,200 origi n o f. 165 perforators from, 165, 168, 181,188,195 right, 180- 18 1, 187-189, 191, 195-196,200 short, 165 P-2 artery, 109, 114-1 15, 165, 176- 177,179. 183, 185, 192. 194 course of. 170 entering ambient cistern, 175, 190

left, 18 1 perfo rators from, 186, 190--19 1 right, 171, 180- 18 1. 19 1, 195 origin of. 200 relatio n o f P- 1 and 1'-2 to posterior communicating artery. 170, 172, 174. 186,199 Cerebral peduncle, 166 Cerebrospinal fluid circulation of, 94 in d istension of arachnoid membrane, 56, 59 drainage by lu mbar puncture, 40-4 1 fl ow through interpedu ncular cistern, 165, 166 in midbrai n se