Anat Clin (1985) 7 : 3-13 (~ Springer-Verlag 1985
Anatomical bases of medical, radiological and surgical techniques Anatomical basis of the microsurgical approach to the pineal gland JJ Moreau l, R R a v o n ~, M Caix 2, G S a l a m o n 3, G Brassier 4 and S Velut 4 i Service de Neurochirurgie, CHU Dupuytren, 2, avenue Alexis-Carrel, F 87032 Limoges, France 2 Laboratoire d'Anatomie, Facult6 de M6decine et de Pharmacie, 2, rue du Docteur-Marcland, F 87032 Limoges Cedex, France 3 Laboratoire de Neuroradiologie et de Microradiographie, U6 INSERM, 280, rue Sainte-Marguerite, F 13009 Marseille, France 4 Service de Neurochirurgie, CHU Pontchailloux, rue Henri-le-Guillou, F 35053 Rennes Cedex, France
S u m m a r y . The microanatomic study of the pineal region was made from 18 cadaver brains. The purpose of this paper is to describe the surgical a n a t o m y needed to approach this area, which is deeply located and in the midline, by analysing the different methods of approach.
Bases anatomiques de l'abord microchirurgical de la glande pin6ale REsumE. L'Etude m i c r o a n a t o m i q u e de la region pinEale a 6t6 rEalisEe ~ partir de 18 pi~ces anatomiques. Ce travail se propose de fournir les d o c u m e n t s anatomiques nEcessaires h l ' a b o r d de cette region, mEdiane et profonde, en analysant ses diffErents modes d'approche. K e y w o r d s : Pineal gland - Pineal region - Surgical a n a t o m y - Microsurgery.
The pineal gland (epiphysis) has always interested anatomists and physiologists. In fact, the earliest research done o n the epiphysis dates from 300 B.P. It is interesting that Descartes (1596-1663) believed that the center of the soul was located in the pineal gland, and that the gland was able to move under the influence of a "rational m i n d " (Fig. 1). A n anatomical study was carried out on 18 subjects (Moreau 1983). Vascular injections of neoprene latex were performed, either on fresh subjects which were then placed in formol for four weeks, or on subjects
Offprint requests : Dr JJ Moreau
Fig. 1 "The soul contained in the gland senses or will sense movements which have as their starting point the gland itself" (The philosophical works of Descartes, F Alquie). The figure shows how a person measures distance by his sense of touch. Descartes resolves the question, in this case, to a changing of position of the gland ~ L'~me contenue dans la glande se rend compte ou se rendra compte des mouvements dont le point de depart est la glande elle-mEme r>(Les oeuvres philosophiques de Descartes, F Alquie). La figure a trait h une appreciation de la distance par le toucher, Descartes rdsout la question en invoquant, en ce cas, un changement de position de la glande
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JJ Moreau et al. : The anatomical basis of the microsurgical approach to the pineal gland
already formolized by carotid injection, according to Wincler's technique, frozen and then defrozen. The method consisted in a catheter injection of the two inner carotids, the two vertebrals and the two jugular veins. After rinsing in water and insuffiation of air, a single syringe injection of latex was made, coloured red for the arteries and blue for the veins. These specimens are ready for dissection two days later, the time required for the latex to set. It is then possible to dissect the specimen for the vessels remain fairly supple and can be sectioned without the product running out. These specimens served for a study of the surgical approache. Dissection was performed under microscope (Zeiss and Wild, model M3), the subject being placed in the usual operation positions. Other specimens were examined by CT scan (scanner model ND 8000 C.G.R.) in the three spatial planes : horizontal, sagittal and frontal. With the information obtained from these, we were able to illustrate the surgical approaches. The epiphysis lies in the fossa separating the superior colliculi (colliculus superior), and is appendaged to the posterior pole of the third ventricle, the posterior commissure (commissura posterior) and the two thalami (thalamus). The vascular elements of the tela choroidea of the third ventricle (tela choroidea ventriculi tertii) are situated above this area, on top of which is the body of the fornix leading posteriorly into the two crura of the fornix between which the great cerebral vein of Galen (V. cerebri magna) is found.
Underneath, the tectum of the midbrain (lamina tecti) disappears below the tentorium cerebelli in front of the vermis (Fig. 2). We can describe the structures which make up the limits of this area. It is through these or between the openings in this area that the surgical approach to the pineal gland must be made. The pineal area is continuous with the upper portion of the superior cistern (cisterna ambiens), which contains the pineal gland, the habenula and a large number of vessels. All of these structures are covered over by the cerebral hemispheres and the corpus callosum. The purpose of this study is to define the microsurgical anatomy of the pineal region. We will review the classical microanatomical findings known about the various structures in this area, along with our own study of these areas encountered in microsurgical approaches.
Anatomical review of the structures of the pineal region (Dejerine 1980) The walls The anterior wall consists of the posterior portion and the base of the third ventricle. The posterior border of the third ventricle is made up from top to bottom of : the base of the pineal gland, the posterior commissure and the opening of the aqueduct of Sylvius (aqueductus cerebri). The base of the third ventricle is limited
Figs. 2-3 2 Mid-sagittal cut. 3 Frontal cut : V3 third ventricle, E epiphysis, F fornix, S splenium, LT tectum of the midbrain (lamina tecti), AC aqueduct of Sylvius (aqueductus cerebri), L lingula cerebelli, T thalamus, VCI internal cerebral vein (V. cerebri internae) 2 Coupe sagittale m6diane. 3 Coupe frontale : V3 troisi~me ventricule, E 6piphysis, F fornix, S splenium, LT lamina tecti, AC aqueductus cerebri, L lingula cerebelli, T thalamus, VCI V. cerebri internae
JJ Moreau et al. : The anatomical basis of the microsurgical approach to the pineal gland
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posteriorly by the pineal gland, and on each side by the habenula (Taenia thalami).
The superior wall consists of the tela choroidea of the third ventricle and of the fornix. The inferior surface of the body of the fornix is attached over its entire length to the choroid plexus by loose connective tissue. These two structures lie on the prominence made by the posterior portion of the thalamus and it is always possible to rouse the external margin to penetrate into the posterior portion of the third ventricle. This is the key to the inter thalamo-trigonal approch. The posterior wall consists of the splenium of the corpus callosum, the tentorium cerebelli and the vermis. It is between and through these structures that the area can be entered by way of the supracerebellar - infra or supratentorial occipital approach. The inferior wall. The paired inferior and superior colliculi and the aqueduct of Sylvius are located here. The area of the corpora quadrigemina is situated above the posterior portion of the cerebral peduncle. This area extends from the postero-superior border of the third ventricle to the anterior margin of the lingula cerebelli. The lateral walls (Fig. 3) are made up of the posterior extremity of the thalamus or pulvinar (pulvinar thalami). It is covered over by the tela choroidea, by the two crura of the fornix (crus fornicis), and by the splenium of the corpus callosum. It also covers the corpora quadrigemiha. At the postero-medial aspect of the pulvinar, on the superior surface, a small triangular structure is found, the base of which is located posteriorly : the habenular trigone (trigonum habenulae). The contents The contents of the pineal region were the main concern of this microanatomical study. The superior cistern bathes all the structures in this area.
The pineal gland is round or conical in shape, averaging 5 to 10 mm in length, 5 to 9 mm width, and 1.5 to 4 mm in thickness. It is very friable, for even the lightest contact can disrupt its surface (Fig. 4). These figures are equivalent to those described by Yamamoto in 1980 : 7.4 mm long, 6.9 mm wide, 2.5 mm thick on average. The distance between the pineal gland and Galen's great vein varies considerably (0 to 15 mm for Yamamoto). Vascularization of the pineal gland is by way of the pineal artery and the pineal veins (Yamamoto 1980) (Fig. 5). In 1969 Plets had already described the very rich blood supply to the epiphysis. The pineal artery, a branch of the medial posterior choroidal artery (rami
Fig. 4 The pineal gland: E epiphysis, CS superior colliculus (colliculus superior), CI inferior colliculus (colliculus inferior) La glande pin6ale : E epiphysis, CS colliculus superior, CI colliculus inferior
choroidei posteriores) vascularizes the pineal gland and the habenular trigone. Most often there is only one artery for each hemisphere and it approaches the gland laterally. Although Wackenheim (1978) recorded that this artery is a single one, other authors (Yamamoto 1980) have shown that an average 1.5 (0 to 5) of the pineal arteries derive from the medial posterior choroidal artery of one hemisphere, and that in 30 % of the cases the gland is vascularized by the branches of the medial posterior choroidal artery of one hemisphere, and of two hemispheres in 70% of the cases. The pineal veins drain venous blood from the pineal gland and the habenular trigone. They are numerous and drain either the ventral surface, the dorsal surfaces, or both surface of the gland (Tamaki 1973). These empty into the internal cerebral veins (v. cerebri internae) and/or into the great cerebral vein of Galen (Yamamoto 1980). According to Yamamoto, an average of 1.9 of the pineal veins (1 to 5) empty into the Galen system. The classification comprises five types according to the mode of drainage into the large-caliber veins. In type 3, the most frequent one, the pineal veins flow into the Galen ampoula.
The medial posterior choroidal artery (fig. 6) is a branch of the posterior cerebral artery (a. cerebri posterior). It numbers from one to three per hemisphere with an average of 1.4 for Yamamoto and 2 to 4 for Baumgartner. In Yamamoto's study the medial posterior choroidal artery is single in 62% of the cases and multiple in 38%, compared with 54% single and 46% multiple arteries reported by Zeal and Rhoton or with 60% single and 40% multiple recorded by Margolis. This artery flows through the superior cistem, travels parallel to the pineal body, then flows over the roof of the third ventricle parallel to and medial to the intemal
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JJ Moreau et al. : The anatomical basis of the microsurgical approach to the pineal gland
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cerebral veins in the midline. It finally vascularizes the choroid plexus of the third ventricle (plexus choroideus ventriculi tertii) through the foramen of Monro (foramen interventriculare). For Lazorthes, Gouaz6, Salomon (1976) the medial posterior choroidal artery divides into two branches : the outer one going to the tela choroidea superior, the inner one to the choroid plexus of the third ventricle.
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Figs. 5-6 S Pineal arteries and veins. E epiphysis, VE pineal vein (V. epiphysis), AE pineal artery (A. epiphysis), VCI internal cerebral vein (V. cerebri internae). 6 The medial posterior choroidal arteries and the Galenic venous system. RCHP medial posterior choroidal artery (rami chorroidei posteriores), VCM great cerebral vein of Galen (V. cerebri magna), VB basilar vein (V. basalis) 5 Art~res et veines pin6ales. E epiphysis, VE V. epiphysis, AE A. 6piphysis, VCI V. cerebri internae. 6 Les art~res choro'idiennes post6rom6dianes et le syst~me veineux de Galien. RCHP rami choroidei posteriores, VCM V. cerebri magna, VB V. basalis
Baumgartner describes a more voluminous medial choroidal posterior artery than the others, running upwards and forwards and passing below the splenium of the corpus callosum to feed the tela choroidea. The other arteries are distributed to the posterior part of the tela choroidea superior; they appear to inosculate with each other with other controlateral arteries, forming a vascular network of large transverse meshes covering the
JJ Moreau et al. : The anatomical basis of the microsurgical approach to the pineal gland posterior face of the mesencephalon. According to Plets the habenula forms a true vascular arterial hilum from which the vessels spread fanwise, irrigating the medial edge of the thalamus. In fact, the most important vascular relationships of the pineal gland are venous, represented by the Galenic venous system (Fig. 6). The proximity of these elements, and the fact that the ligature of the ampulla of Galen or of the two inner cerebral veins at their ending in man has the reputation of being ill-tolerated, means that caution is necessary when microdissecting in the surgical approaches.
The great cerebral vein of Galen averages about 12 mm in length, from 8 to 25 mm for Yamamoto, from 5 to 15 mm for Johanson (1954), receiving the venous drainage from the internal cerebral veins, the precentral cerebellar veins (VV. cerebelli superiores), in 86.4% of the cases in Yamamoto's study, the internal occipital vein (77% of the cases) (V. occipitalis internae), the basilar vein of Rosenthal (51.7% of the cases), (V. basalis), the posterior pericallosal vein (41.5% of the cases), the pineal veins (40.9% of the cases), and sometimes the posterior mesencephalic vein (38.4% of the cases) and the posterior ventricular vein (6.7% of the cases). It is one of the most constant findings in this area and serves as a landmark for the surgical approaches. The basilar vein or basal vein of Rosenthal drains either into the internal cerebral vein or into the great cerebral vein of Galen. Numerous anatomical variations in the drainage of the Rosenthal basal vein have been described, for example the right sinus, the lateral sinus, the petrous sinus. Its proximal portion or posterior mesencephalic segment can be identified by locating the medial posterior choroidal artery as it curves over the vein with its concavity directed antero-superiorly, which makes them both simple to identify (Baumgartner 1981). The internal occipital veins receive venous blood from the inferior and medial surfaces of the occipital lobe, and most often drain into the great cerebral vein of Galen and sometimes in the inner cerebral vein according to Yamamoto, or in the posterior part of the basal vein according to Johanson and Baumgartner. This venous system should be better known and respected. The posterior pericallosal vein arises from the dorsal surface of the corpus callosum and goes around the splenium parallel to the posterior pericallosal artery. It empties into the internal cerebral vein or the great vein of Galen. There are usually two posterior pericallosal veins, but in one case out of three there is only one vein. The precentral cerebellar vein, which originates from the precentral cerebellar fissure, is directed upwards to join the great cerebral vein of Galen in most cases or the
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posterior portion of the internal cerebral vein. It can be single and medial or double and paramedian, the two venous branches then uniting in one single trunk.
The superior vermian veins result from the union of several veins coming from above the culmen in the fissure between the central lobe and the culmen. They unite into a single trunk which joins the great cerebral vein of Galen or the precentral cerebellar vein. The internal cerebral veins are the most important deep cerebral veins. From their origin at the foramen of Monro, they travel from front to back within the tela choroidea adjacent to the midline. After diverging, they run along the supero-lateral surface of the pineal gland, appearing in the form of a lyre (Johanson 1954). During their flow, numerous subependymal veins drain into them. Caron et al. (1974) report two cases of ligature of the two inner cerebral veins with good clinical tolerance; they explain this by the functional character of the anastomotic veins between the cortical and deep veins.
Approaches to the pineal region Given the depth of this region, and the close vascular elements, in particular the Galenic venous system, expanding lesions of the pineal area are among the most difficult tumors to excise surgically. Twenty to thirty percent of these tumors, however, are benign and radioresistant. Due to this fact, there has been renewed interest in the direct approach to these neoplasms. This surgical procedure makes it possible to obtain a precise histological diagnosis, and evaluate the degree of extension to neighboring vital structures. It is curable when the excision is complete. There are numerous approaches to this area. The depth of the region, the histological characteristics of the expanding lesion, its size, its location, and the preferences of each surgeon all influence the choice of a particular approach.
The parieto-occipital approach of Dandy During this extra-cerebral approach (Dandy 1915) (Fig. 7), the incision through the posterior portion of the corpus callosum permits good exposure to the superior pole of the pineal gland. The great vein of Galen can be rapidly identified and the anterior and lateral surfaces of the epiphysis are seen to be well exposed. The drawbacks of this approach include having to incise the corpus callosum, to sacrifice the posterior parietal veins, to have a suboptimal view of the relationship of the tumor with the tectum of the midbrain, and moreover the internal cerebral veins are in the way of the operative field.
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JJ Moreau et al. : The anatomical basis of the microsurgical approach to the pineal gland
Figs. 7-8
7 Frontal cut by CT scan. Parieto-occipital approach of Dandy. 8 Supratentorial occipital approach. A Mid-sagittal cut by CT scan. The head is flexed forward as in the surgical procedure. B Horizontal cut by CT scan 7 Coupe frontale tomodensitomdtrique. Abord pari6tooccipital selon la technique de Dandy. 8 Voie occipitale sus-tentorielle. A Coupe sagittale m6diane tomodensitom6trique, t6te en position op6ratoire pench6e en avant. B Coupe horizontale tomodensitom6trique
The supra-tentorial occipital approach This was first used by Poppen in 1960, then modified by Jamieson in 1971, and later by Lapras (Capdeville 1974) (Fig. 8). This is also an extra-cerebral route which, after incising the tentorium of the cerebellum, approaches the region by passing between the superior surface of the cerebellum and the great vein of Galen after dividing the superior cerebellar veins. The pineal gland is approached from its inferior and lateral surfaces. The most important vessels in the area are always in view, but on the other hand, invasion of the thalamus is not discovered until the end of the operation. This surgical approach was performed on anatomical specimens injected with latex whose brains were considered normal (Fig. 9). Proper positioning of the head is important. It should be bend
forward and turned slightly towards the right so that the straight sinus lies obliquely in the anterior-posterior plane and from right to left to ensure good exposure of the tentorium of the cerebellum. The occipital lobe must be carefully raised in order to coagulate the cortico-dural vessels which are often found in the inferior angle and on the inferior surface of the occipital pole. The occipital pole (and not the internal margin) must be spread upwards and outward. It is not necessary to start the incision of the tentorium cerebelli at its free border. This can be done on its surface making a rectilinear incision 1.5 cm away from the straight sinus, 3 to 4 cm in length down to the free border. Sometimes the two layers of the tentorium do not adhere to each other. After dividing the superior cerebellar veins, the retractor is slightly displaced in order to lift outwards the internal surface of
JJ Moreau et al. : The anatomical basis of the microsurgical approach to the pineal gland
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Figs. 10-12 10 ab Mid-sagittal cuts by CT scan. The inll'atentorial suboccipital approach of Krause 11 Frontal cut by CT scan. Transventricular approach of Van Wagenen. 12 Frontal cut by CT scan. Inter thalamo-trigonal approach 10 ab Coupes sagittales m6dianes tomodensitom6triques. Abord suboccipital infra-tentoriel selon la technique de Krause. l l Coupe frontale tomodensitom6trique. Abord transventriculaire selon la technique de Van Wagenen. 12 Coupe frontale tomodensitom6trique. Abord interthalamotrigonal
Figs 9, 13 (pages 10-11) 9 a-e The supra-tentorial occipital approach, cc corpus callosum, vci V. cerebri intemae, vcm V. cerebri magna, vb V. basalis, E epiphysis, cs colliculus superior, cbm cerebellum. 13 a-d The inter thalamo-trigonal approach, a Right frontal horn intraventricular approach. View just before elevating the body of the trigonum and the choroid tissue, m foramen of Monro, vsp V. septi pellucidi, vts V. thalamo striata, tc tela choroidea, p c h plexus choroideus, b View after elevating the body of the trigonum and the choroid tissue f fornix, vci V. cerebri internae, e E epiphysis, ch commissura habenularum, vci V. cerebri internae, d ac aqueductus cerebri, cp commissura posterior, ch commissura habenularum, E epiphysis, vci V. cerebri internae 9 a-e L'abord occipital sus-tentoriel. 13 a-d La voie interthalamo-trigonale, a Abord intraventriculaire come frontale droite. D6but du soul6vement du couvercle v61o-trigonal, b Ecartement du couvercle v61o-trigonal
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JJ Moreau et al. : The anatomical basi~ of the microsurgical approach to the pineal gland
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JJ Moreau et at. : The anatomical basis of the microsurgical approach to the pineal gland
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JJ Morean et al. : The anatomical basis of the microsurgical approach to the pineal gland
the occipital pole. We note in the midline the splenium and the great cerebral vein of Galen. In order to reach the pineal region, the great cerebral vein of Galen must be followed up to the internal cerebral veins. We easily locate the terminal ends of the two large basilar veins, the corpora quadrigemina covered by a dense capillary network, the pulvinar, the posterior portion, the body, and the top portion of the pineal gland.
to the histopathological findings, we irradiate the tumor locally by the stereotaxic insertion of a radioactive substance or we irradiate extemally after placing a ventriculo-peritoneal shunt. If the tumor is larger than 3 cm and is radioresistant, we use a direct surgical approach, the inter-thalamo-trigonal approach, for tumors that have developed anteriorly in this region, and the supratentorial occipital approach for tumors arising posteriorly (Lesoin 1980).
The infra-tentorial supracerebellar approach described by Krause In the approach (cited by Lazar 1974) (Fig. 10), the anterior pole of the epiphysis is very far from the surgeon, and there is a risk of a prolapse of the cerebral hemispheres. This approach is reserved for tumors which have developed posteriorly and infra-tentorially.
The lateral transventricular approach of Van Wagenen described in 1931 After making a right parieto-occipital craniotomy flap, the posterior portion of the third ventricle is entered through the internal surface of the lateral ventricle. This can be a useful approach when there is marked ventricular dilatation (Fig. 11).
The inter-thalamo-trigonal approach This is also a transventricular approach following a right frontal incision (Delandsheer 1978, Jomin 1980) (Figs. 12, 13). The body of the trigonum and the choroid tissue are raised by grasping the external border of the tela choroidea which permits entry into the third ventricle. We locate the right internal cerebral vein at its origin at the foramen of Monro. We follow along the superior convexity of the vessel down to its entrance with the opposite internal cerebral vein into the great cerebral vein of Galen. The origin of the left internal cerebral vein is found easily because it is near the midline, turning and then returning to the midline near its proximal end. The tectum of the midbrain is very far away. We approach the base of the pineal gland and can distinguish easily the pineal recess, the habenula, the posterior commissure and the habenular commissure (commissura habenularum). Conclusion The direct surgical approach to the pineal region remains difficult. We recommend the following therapeutic guidelines in the presence of an expanding lesion in this area: a stereotaxic biopsy, depending on the clinical findings, along with a CT scan (Pecker 1979). If the tumor is small in volume and is radiosensitive according
References Alquie F (1963) (Euvres philosophiques de Descartes. Ed Gamier fr&es, Paris. Baumgartner J, Toumade A, Plas JY (1981) Etude anatomochirurgicale de la voie d'abord de la toile choroidienne suprrieure du troisirme ventricule. Neurochirurgie 27 : 97-102 Capdeville J (1974) Les tumeurs de la rrgion pinrale, thrse Lyon Caron JP, Debrun G, Sichez JP, Comdy J, Lacour P (1974) Ligature des veines cerrbrales internes et survie. A propos de 2 pinralomectomies. Neurochirurgie 20 : 81-90 Dandy WE (1915) Extirpation of the pineal body. J Exp Med 22 : 237-247 Dejerine J (1980) Anatomie des centres nerveux, Tome 1, Masson, Paris Delandsheer JM, Guyot JF, Jomin M, Scherpereel B, Laine E (1978) Acc~s au troisi~me ventricule par voie interthalamo-trigonale. Neurochirnrgie 24:419-422 Jamieson KG (1971) Excision of pineal tumours. J Neurosurg 35 : 550-553 Johanson C (1954) The central veins and deep dural sinues. An anatomical and angiographic study. Acta Radiol (Stock) 107: 1-184 Jomin M, Lesoin F, Delan'dsheer JM, Laine E (1980) Int&~t de la voie interthalamo trigonale dans le traitement des tumeurs du troisirme ventricule et de la rrgion 6piphysaire. Neurochirurgie 26 : 171-177 Lapras C (1978) Rrsultats du traitement chirurgical par abord direct occipital supra-tentoriel des tumeurs pinrales. A propos de 50 observations. Communication ~ la Socirt6 de Neurochirurgie de Langue franqaise Lazar ML (1974) Vein of Galen aneurysm : successful excision of a completely thrombosed aneurysm in an infant. Surg Neurol 2 : 22-24 Lazorthes G, Gouaz6 A, Salamon G (1976) Vascularisation et circulation de l'encrphale, Tome 1 Masson, Paris Lesoin F (1980) Les tumeurs de la rrgion pinrale, Thrse Lille Margolis MT, Newton TH, Hoyt WF (1974) Gross and Roentgenographic anatomy - Pathology. Radiology of the skull and brain, CV Mosby, St Louis, vol. II, book 2 : 1551-1627 Moreau JJ (1983) Anatomie microchirurgicale de la rrgion pinrale, Th~se Limoges Pecker J, Scarabin JM, Vallre B, Brucker JM (1979) Treatment in tumours of the pineal region : value of stereotaxic biopsy. Surg Neurol 12:341-348 Plets C (1969) The arterial blood supply and angioarchitecture of the posterior wall of the third ventricle. Acta Neurochir 21 : 309-317 Poppen JL (1960) An atlas of neurosurgical techniques. WB Saunders, Philadelphia Salamon G (1971) Atlas de la vascularisation artrrielle du cerveau chez l'homme. Sandoz, Pads Van Wagenen WP (1931) A surgical approach of the removal of
JJ Moreau et al. : The anatomical basis of the microsurgical approach to the pineal gland certain pineal tumors : report of a case. Surg Gynecol Obstet 53 : 216-220 Wackenheim A, Babin E (1978) Tomodensitom6trie cranio-c6r6brale. Masson, Paris Yamamoto I, Kageyama N (1980) Microsurgical anatomy of the pineal region. 1 Neurosurg 53 : 205-221
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Zeal AA, Rhoton AL Jr (1978) Microsurgical anatomy of the posterior cerebral artery. J Neurosurg 48 : 534-559 Tamaki N, Fujirawa K, Matsumoto S, Takeda H (1973) Vein draining the pineal body (anatomical and neuroradiological study) J Neurosurg 39:448-454