Journal of Neuro-Oncology 54: 263275, 2001. 2001 Kluwer Academic Publishers. Printed in the Netherlands.

Pineal region tumor: surgical anatomy and approach

Isao YamamotoDepartment of Neurosurgery, Yokohama City University School of Medicine, Yokohama, Japan

Key words: microsurgical anatomy, pineal region, pineal tumor, surgical approach, third ventricle

Summary

The pineal region is one of the surgically inaccessible areas in the brain. Many neurovascular structures form aformidable obstacle to the operative approach to this region. The approaches suitable for reaching the pineal regionare the infratentorial supracerebellar, occipital transtentorial, posterior transcallosal, posterior transcortical andposterior subtemporal routes. Considerations important in selecting one of these surgical approaches are reviewedfrom the anatomical viewpoint.

For neurosurgeons, the pineal region tumor is one of thedifficult ones to expose and remove. The approachessuitable for reaching the pineal region are infraten-torial supracerebellar, occipital transtentorial, poste-rior transcallosal, posterior transcortical and posteriorsubtemporal (Figure 1). Horsely [1] was the first sur-geon to do a direct surgery for the pineal region tumorthrough the posterior fossa. Krause [2] in 1926 suc-cessfully operated on a tumor of the pineal regionthrough the infratentorial supracerebellar approach andStein [3] then modified this approach with the modernmicrosurgical techniques. The occipital transtentorialapproach was first advocated by Brunner [4] and thenPoppen [5] and Jamieson [6] developed and in 1974Lazar and Clark [7] reported their experiences usingthis approach with six cases of pineal region tumor.The posterior interhemispheric transcallosal approachwas originally described by Dandy [8] in 1921. ThenHorrax [9], Kunicki [10], Araki [11] and Suzuki andIwabuchi [12] fostered this approach. Van Wagenen[13] used posterior transcortical approach through thedilated ventricle. Sekhar and Goel in 1992 reported thecombined supra/infratentorial-transsinus approach forthe resection of certain large pineal region tumors [14].

Microsurgical anatomy

Selecting an operative approach to the pineal regiontumor involving the third ventricle requires an

C

ABB

EE

D

Figure 1. Various surgical approaches to the pineal region:(A) infratentorial supracerebellar, (B) occipital transtentorial,(C) posterior transcallosal, (D) posterior transcortical and(E) posterior subtemporal approaches.

understanding of the microsurgical anatomy of theposterior third ventricle. The posterior third ventricleis composed of the roof, floor, posterior wall and bothlateral walls (Figure 2) [15].

264

Corp. Call.

Sept. Pel.

Fornix

F. Monro

Ant. Comm.

Lam. Ter.O. Recess

O. Ch.

Infund. Recess

Infund.

Pit. Grand

III

Tubrer. Cin.

Hypothal.

Pons

Midbrain

Int. Cer. V.

Med. Post. Ch. A.

Thalamus

Suprapineal Recess

PinealPineal RecessPost. Comm.Aqueduct

Hypothal. Sulc.

Post. Perf. Subst.

Mam. B.

Figure 2. Midsagittal section of the third ventricle. The roof extends from the foramen of Monro (F. Monro) to the suprapineal recessand is formed by the fornix and the layers of tela choroidea between which course the internal cerebral vein (Int. Cer. V.) and themedial posterior choroidal artery (Med. Post. Ch. A.). The hippocampal commissure, the corpus callosum (Corp. Call.) and the septumpellucidum (Sept. Pel.) are above the roof. The anterior wall extends from the optic chiasm (O. Ch.) to the foramen of Monro and includesthe upper surface of the optic chiasm, the optic recess (O. Recess), the lamina terminalis (Lam. Ter.), the anterior commissure (Ant.Comm.) and the foramen of Monro. The floor extends from the optic chiasm to the aqueduct and includes the lower surface of the opticchiasm, the infundibulum (Infund.), the infundibular recess (Infund. Recess), the pituitary gland (Pit. Grand), the tuber cinereum (TuberCin.), the mamillary body (Mam. B.), the posterior perforated substance (Post. Perf. Subst.) and the midbrain. The posterior wall extendsfrom the suprapineal recess to the aqueduct and includes the habenulla commissure, the pineal body (Pineal), the pineal recess and theposterior commissure (Post. Comm.). The lateral wall is formed by the thalamus superiorly and the hypothalamus (Hypothal.) inferiorly.The hypothalamic sulcus (Hypothal. Sulc.) forms a groove between the thalamus and the hypothalamus. (From Yamamoto I, Rhoton AL,Peace DA: Microsurgery of the third ventricle: Part 1, Microsurgical anatomy. Neurosurgery 8: 334356, 1981.)

Roof

The roof of the third ventricle extends from the fora-men of Monro anteriorly to the suprapineal recessposteriorly and has four layers: upper neural layerformed by the fornix, two membranous layers formedby the tela choroidea and a vascular layer, which con-sists of the medial posterior choroidal arteries and theirbranches and the internal cerebral veins and their trib-utaries, between the space formed by the sheets of telachoroidea called velum interpositum cistern (Figures 2and 3). The fornix is composed of a column, a body anda crus. Both crura are interconnected by a sheet of whitematter called the hippocampal commissure (Figure 3).The lateral margin of the roof is formed by the narrow

cleft between the fornix and the thalamus, that is calledthe choroidal fissure (Figure 3).

Floor

The floor extends from the optic chiasm anteriorly tothe cerebral aqueduct posteriorly and the posterior halfof the floor is formed by the midbrain, which extendsfrom posterior and superior to the medial part of thecerebral peduncles and superior to the tegmentum ofthe midbrain (Figure 2). The mamillary body is an onlyprominence on the inner surface of the floor and theposterior part of the floor of the third ventricle poste-rior to the mamillary bodies is a smooth and concavesurface from side to side (Figure 4).

265

(A)

(C)

(B)

Figure 3. The inferior view of the roof of the third ventricle. (A) The cerebral hemispheres below the roof of the third ventricle havebeen removed to provide the inferior view of the roof. The internal cerebral vein (Int. Cer. V.) and the medial posterior choroidalartery (Med. Post. Ch. A.) course below the fornix and two halves of the thalamus. (B) The medial edges of the thalamus have beenremoved to provide a wider view of the roof. The internal cerebral veins pass posteriorly above the pineal body (Pineal) and jointo form the great vein of Galen (V. Galen). The choroidal fissure (Chor Fiss.) is a cleft between the fornix and the thalamus. (C)The choroidal fissure on each side has been removed to expose the neural layer of the roof. The lateral ventricle (Lat. Vent.) is seenthrough the enlarged choroidal fissure. The hippocampal commissure (Hippo. Comm.) interconnects the medial margins of the cruraof the fornix above the pineal gland. Anterior commissure (Ant. Comm.), foramen of Monro (F. Monro), choroidal plexus (Ch. Pl.),habenular commissure (Hab. Comm.), superior choroidal vein (Sup. Ch. V.), lateral posterior choroidal artery (Lat. Post. Ch. A.) (FromYamamoto I, Rhoton AL, Peace DA: Microsurgical of the third ventircle: Part 1, Microsurgical anatomy. Neurosurgery 8: 334356,1981.)

266

Figure 4. The anterior part of the cerebral hemispheres have beenremoved and the median raphe of the fornix have been openedto expose the full length of the floor of the third ventricle. Thefloor extends from the optic chiasm (O. Ch.) to the aqueduct. Themamillary body (Mam. B.) is an only prominence of the innersurface of the floor. The habenular commissure (Hab. Comm.)forms the upper margin of the stalk of the pineal body (Pineal)and the posterior commissure (Post. Comm.) forms the lowerstalk of the pineal body. The pineal recess is between the twocommissures. Choroidal plexus (Ch. Pl.), superior choroidal vein(Sup. Ch. V.), medial posterior choroidal artery (Med. Post. Ch.A.), foramen of Monro (F. Monro), anterior commissure (Ant.Comm.), infundibular recess (Infund. Recess), optic tract (O. Tr.),optic nerve (O. N.) stria medullaris (Str. Med.), caudate nucleus(Caudate Nucl.) (From Yamamoto I, Rhoton AL, Peace DA:Microsurgery of the third ventricle: Part 1, Microsurgical anatomy8: 334356, 1998.)Posterior wall

The posterior wall within the third ventricle extendsfrom the suprapineal recess above to the cerebral aque-duct below and consists of suprapineal recess, thehabenular commissure, the pineal body and its recess,the posterior commisure and the cerebral aqueduct(Figures 2, 4 and 5). The only structure in the pos-terior wall in the quadrigeminal cistern is a pinealbody and is concealed by the splenium above, thalamusLaterally and the quadrigeminal plate and the vermisbelow (Figures 2 and 6).

Figure 5. The anterosuperior view of the posterior wall of thethird ventricle after removal of the upper part of the cerebral hemi-spheres, thalamus and corpus callosum. The suprapineal recessis above the habenular commissure (Hab. Comm.) and the pinealrecess extends into the stalk of the pineal body (Pineal) abovethe posterior commissure (Post. Comm.) and the aqueduct. Lat-eral ventricle (Lat. Vent.), choroidal fissure (Ch. Fiss.), massaintermedia (Massa Int.), infundibular recess (Infund. Reccess),septum pellucidum (Sept. Pel.). (From Yamamoto I, Rhoton AL,Peace DA: Microsurgery of the third ventricle: Part 1, Microsur-gical anatomy. Neurosurgery 8: 334356, 1981.)

Lateral wall

The lateral walls of the third ventricle are formed by thethalamus superiorly and the hypothalamus inferiorly(Figures 2 and 7). The habenulae are small eminenceson the dorsomedial surface of the thalamus just in frontof the pineal body. The habenulae are connected acrossthe midline in the rostral stalk of the pineal body by thehabenular commissure. The massa intermedia connectsthe opposing surfaces of the thalamus and is presentin 76% (15).

Operative approach

Among various surgical approaches for the pinealregion tumors, the posterior transcallosal, posterior

267

Figure 6. The posterior view of the pineal region after removal of the posterior cerebral hemispheres. The third ventricle (3V) has beenopened above the pineal body (Pineal) by removing the tela choroidea in the roof. Corpus callosum (Corp. Call.), lateral ventricle (Lat.Vent.), caudate nucleus (Caudate Nucl.), superior choroidal vein (Sup. Ch. V.), pulvinar (Pulv.), choroidal plexus (Ch. Pl.), superiorcolliculus (Sup. Coll.), inferior colliculus (Inf. Coll.), posterior cerebral artery (P. C. A.) superior cerebellar artery (S. C. A.). (FromYamamoto I, Rhoton AL, Pease DA: Microsurgery of the third ventricle: Part I, Microsurgical anatomy. 8: 334356, 1981.)

transcortical and posterior subtemporal approaches arerarely used because of the adverse effects of dividingthe corpus callosum, incising the parietal cortex and theretracting the temporal lobe. Therefore, the infratento-rial supracerebellar approach and the occipital transten-torial approach are now commonly used.

Infratentorial supracerebellar approach

The infratentorial supracerebellar approach is essen-tially a midline posterior approach to the pineal regionand has several advantages (Table 1) [16,17]. The mainadvantage is that this approach is essentially extra-axialroute to the third ventricle and the pineal region islocated underneath the major deep veins, which dimin-ishes the chance for important neurovascular compro-mise. However, the disadvantage of this approach is anarrow operative field because of the presence of thetentorium, which produces restricted visualization atboth lateral and superior corners [18,19]. Therefore,this approach should not be used when the tumor islarge and extends dorsally above the tentoriaum and/orextends laterally into the trigone of the lateral ventricle.

Fortunately, most of the pineal region tumors are ofmodest size and are located infratentorially. For thesereasons, I prefer this approach in most of the cases ofpineal region tumors.

There are several positions that can be used forthis approach, that is, sitting [16], three-quarter prone[20], lateral decubitus and Concorde positions [21].The advantage of sitting position is that a gravityprovides cerebellum falling away from the tentoriumand minimizes venous pressure, which causes lessbleeding. However, its disadvantages include the riskof air embolism and the discomfort to the surgeon whomust operate with his arms extended and neck hyper-extended to see above the tentorium. The advantageof Concorde position is the lower risk of air embolismand tension pneumocephalus [21], but negates theadvantages of gravity-assisted retractors and hemosta-sis. The indispensable diagnostic procedure to adoptthis approach in sitting position is the evaluation ofthe preoperative sagittal MRI analysis of the angleof the straight sinus [22]. The tumor is easily exposedin the cases of low-angle (Figure 8A) and commontypes (Figure 8B), but the operative field is restricted

268

Figure 7. Midsagittal section of the third ventricle to expose the relationship of the internal cerebral vein (Int. Cer. V.), the great veinof Galen (V. Galen), the basal vein (Basal V.), the medial posterior choroidal artery, splenial artery (Spl. A.). The lateral wall is formedby the thalamus superiorly and the hypothalamus inferiorly. Corpus callosum (Corp. Call.), septum pellicudum (Sept. Pel.), pericallosalartery (Pericall. A.), choroidal plexus (Ch. Pl.), superior colliculus (Sup. Coll.), inferior colliculus (Inf. Coll.), thalamoperforating artery(Th. Pe. A.), foramen of Monro (F. Monro), massa intermedia (Massa Int.), anterior commissure (Ant. Comm.), lamina terminalis (Lam.Ter.), anterior cerebral artery (A. C. A.), optic chiasm (O. Ch.), optic nerve (O. N.), carotid artery (C. A.), posterior communicating artery(P. Co. A.). (From Yamamoto I, Rhoton AL, Peain DA: Microsurgery of the third ventricle: Part 1, Microsurgical anatomy. Neurosurgery8: 334356, 1981.)

Table 1. Advantages and disadvantages of the infratentorialsupracerebellar approach

Advantages1. Basically midline and easy orientation2. Extra-axial to the IIIrd ventricle3. Beneath the deep venous system4. Minimal damage to delicate nervous structures5. No morbidity related to parietal or occipital lobeDisadvantages1. Narrow operative field2. May sacrifice lateral bridging vein and/or precentral

cerebellar vein3. May split upper vermis4. Poor visualization of supratentorial structures5. Difficult to reach paremedian lesions in the IIIrd ventricle6. Inadequate view of the posterior floor of the IIIrd ventricle

by the steeply inclined tentorium in the case of thehigh-angle type (Figure 8C), in that case the occipitaltranstentorial or three-quarter prone position would bemore suitable.

The craniotomy or craniectomy should extend justover the transverse sinus and include the torcularregion so that the view is not obscured by overhangingbone. Once the dura is opened, many bridging veinsbetween the tentorium and the superior surface of thecerebellum, including some of the hemispheric and ver-mian veins, and the vein of the cerebellomesencephalicfissure, can be sacrificed without any adverse effectin order to open the quadrigeminal region (Figure 9)[23]. However, a cerebellar swelling following the sac-rifice of the lateral bridging veins have been reported byPage [24]. Therefore, I try to preserve lateral bridgingveins as much as possible. The arachnoid membraneover the quadrigeminal cistern is usually thickenedand opaque in the presence of tumors and is openedby microdissection techniques to expose the precen-tral cerebellar vein. The precentral cerebellar vein maybe sacrificed with impunity to further exposure of thepineal region [16]. However, in rare cases, the vein ofthe cerebellomesencephalic fissure or the superior and

269

(A)

(B)

(C)

Figure 8. Three types of variations of the spatial relationship between the straight sinus and the corpus callosum in midsagittal MRI:(A) low-angle type, (B) common type and (C) high-angle type.

270

Figure 9. Bridging veins between cerebellum and overlying tentorial surface are located medially as well as laterally.

inferior quadrigeminal veins are so well developed thatthe tumor cannot be approached directly from behind.In that case, the tumor should be approached slightlyobliquely between these veins and the basal vein [25].One of the important things to appreciate the deepvenous structures, such as great vein of Galen, internalcerebral veins and the basal vein, is to open the thickarachnoid widely at the initial maneuvers. Once thearachnoid is dissected from these veins, the relation-ship between the tumor and deep venous structures isidentified (Figure 10). As the great vein of Galen andthe internal cerebral veins in the germ cell tumor andteratoma are usually well above the tumor, the tumorcapsule is dissected free from the surrounding struc-tures. If a meningioma is arising at the falacotentorialjunction, these deep cerebral veins are displaced ante-riorly and lie on the anterior surface of the tumor. If aglioma is arising from the quadrigeminal plate, thesevessels are displaced superiorly. What is done at thispoint depends upon the patients pathology. If the tumoris a glioma, a modest decompression should be done.If the tumor is a benign pineal tumor, a total removalis the goal. Some small and well-encapsulated tumorcan be removed without internal decompression. If thetumor is large in size, the capsule is opened and the

tumor is debulked with suction, ultrasonic aspirator andlaser so on. After internal decompression, the superiorand lateral margins of the tumor can be dissected fromsurrounding velum interpositum, pulvinar and walls ofthe third ventricle. Removal of the inferior portion ofthe tumor is the most difficult since it is often adherentto the colliculi. After completion of the tumor removal,the cavity of the third ventricle is visualized with nor-mal neural structure such as foramen of Monro andcerebral aqueduct with the aid of endoscope or den-tal mirror. In sitting position, meticulous hemostasis isvery impornat, but hemostatic agent such as Surgicelshould be placed carefully so that it does not float andobstruct the aqueduct when the third ventricle fills withCSF [26].

Occipital transtentorial approach

The main advantage of occipital transtentorialapproach over the infratentorial supracerebellarapproach is more extensive view of the entire pinealregion (Table 2) [17,19,27,29]. There is significantvariation in the size of the tentorial notch [19,28]. Thetransection and reflection of the tentorium providesan excellent view of the pineal region both above and

271

Figure 10. Infratentorial supracerebellar view into the pineal region. The precentral cerebellar vein (Pre. Cent. Cereb. V.) has been divided.The internal occipital (Int. Occ. V.), basal vein (Bas. V.) and pineal veins (Pineal V.) drain into the great vein of Galen (V. Galen). Thevermis is retracted downward to expose the superior (Sup. Cill.) and inferior colliculi (Inf. Coll.). The posterior cerebral (P. C. A.) andmedial posterior choroidal arteries (Med. Post. Ch. A.) are lateral to the pineal gland (Pineal). Tentorium (Tent.), occipital lobe (Occ.Lobe). Tentorium (Tent.) (From Yamamoto I, Rhoton AL, Peace DA: Microsurgery of the third ventricle: Part 1, Microsurgical anatomy.Neurosurgery 8: 334356, 1981.)

Table 2. Advantages and disadvantages of the occipital transten-torial approach

Advantages1. Wide operative field2. No veins crossing from occipital lobe into superior sagittal

sinus3. Easy visualization of deep venous structure4. Largely extra-axial above the tentorium5. Good visualization of ipsilateral dorsal and lateral extension

of the midbrainDisadvantages1. Risk of damage to occipital lobe or internal occipital vein2. Risk of damage to deep venous structure3. Variation in anatomy of the tentorial notch4. Poor visualization of contralateral half of quadrigeminal

region and ipsilateral thalamus5. May need to split splenium

below the tentorial opening. As there are infrequentlybridging veins between the medial occipital poleand the transverse, straight and sagittal sinuses, theoccipital pole can be retracted superolaterally without

sacrificing these medial bridging veins [29]. However,the inferior cerebral vein, which drains from occipitallobe into the transverse sinus, should be preserved,because its interruption may produce infarction andedema of the occipital lobe [7,30]. The disadvantage ofthis approach is a poor visualization of the contralat-eral quadrigeminal region and ipsilateral pulvinar inthe posterior third ventricle. Therefore, this approachis suitable for approaching tumors in the pineal region,especially those centered at the tentorial edge or aboveand if there is no major extension to the oppositeside [27].

This approach was traditionally performed with thepatient in the sitting position with the attendant riskof air embolism and a high frequency of the postoper-ative visual field defect [6]. An alternative to the sit-ting poisiton is prone, Concorde, three-quarter prone orpark bench position. The advantages of three-quarterprone position are the less risk of air embolism and thereduced retraction of the occipital lobe [20]. Therefore,I prefer three-quarter prone position.

272

One of the important points at the craniotomy is thatthe transverse and sagittal sinuses must be visualizedthrough their extent in the operative field by rongeuror airdrill. After opening the dura, the occipital lobe isexposed. The inferior cerebral vein may occasionallybe seen at the lateral inferior edge of the craniotomy(Figure 11). It is necessary to take care to preserve thisvein to prevent the occipital lobe infarction [30]. Theimportant point here is to avoid excess retraction tothe medial occipital lobe and to preserve the internaloccipital vein. Therefore, the retractor should be placedon the inferior surface of the occipital lobe rather thanon the calcaline fissure. If three-quarter prone positionis used, it is easy to retract the occipital lobe with-out excess retraction pressure, because the gravity fallsthe occipital lobe away spontaneously. The internaloccipital vein usually across from the quadrigeminalcistern to the anteromedial surface of the occipitallobe and sacrificing this vein may cause hemianopsia[31]. However, in my personal experience, an excessiveoccipital lobe retraction takes more part in the causeof postoperative visual field defect than the transec-tion of the internal occipital vein. The retractor is thenadvanced until it reaches the tentorial free edge and

Figure 11. The inferior cerebral vein (arrow) is between the inferior surface of the lateral occipital lobe and the tentorium of transversesinus.

the tentorium is incised to expose the superior cerebel-lar surface along a line parallel and 11.5 cm lateralto the straight sinus from a point anterior to the trans-verse sinus to the tentorial free edge, and then the lat-eral flap is reflected laterally. The dense arachnoid overthe quadrigeminal cistern is opened. One of the dis-advantages of this approaches is that the great vein ofGalen and its tributaries often obstruct the approach tothe pineal region (Figure 12) [27]. To gain more accessto the pineal region, it is necessary to dissect the deepvenous system far laterally as well as the lower portionof the splenium. Fortunately, the splenium is usuallyelevated and thinned by the tumor and therefore canbe spared. This exposure provides sometimes an inad-equate view of the contralateral half of the quadrigem-inal plate and an ipsilateral lateral wall of the thirdventricle. Pineal region tumor may extend inferiorlydown under the vermis. If this is the case, the vermisis divided to expose the lower pole of the tumor. Thesurgeon should be aware that the division of the uppervermis produces little in the way of neurological deficit[29], but the sacrifice of the splenium may produce adisconnection syndrome [17]. The tumor is removedaccording to the principles outlined previously.

273

Figure 12. Occipital transtentorial view into the pineal region.The right half of the tentorium (Tent.) has been divided. Thecerebellum is retracted inferiorly. The occipital lobe (Occ. Lobe)is retracted laterally to expose the splenium and to show therelationship of the great vein of Galen (V. Galen) and its tribu-taries, including the internal cerebral (Int. Cer. V.), internal occip-ital (Int. Occ. V.) and the basal veins (Bas. V.). Straight sinus(Str. Sinus), posterior cerebral artery (P. C. A.), medial posteriorchoroidal artery (Med. Post. Ch. V.), superior cerebellar artery(S. C. A.), superior (Sup. Coll.) and inferior colliculi (Inf. Coll.).(From Yamamoto I, Rhoton AL, Peace DA: Microsurgery of thethird ventricle: Part 1, Microsurgical anatomy. Neurosurgery 8:334356, 1981.)

Posterior transcallosal approach

The main advantage of the posterior transcallosalapproach is that the pineal region can be reached withan irrelevant to the ventricular size as well as with-out a sacrifice of any important neurovascular struc-tures besides the corpus callosum (Table 3) [17,32].The opening of the tentorium provides the exposure tothe superior portion of the quadrigeminal region. Thisapproach is the shortest access to the pinral region.However, as the galenic system and its tributaries areencountered before the pathological structures [32].

Although a number of options in positioning arepossible in the posterior transcallosal approach, alateral decubitus or three-quarter prone position arecommonly used [32]. These positions provide gravity

Table 3. Advantages and disadvantages of the posterior tran-scallosal approach

Advantages1. Irrevelant to ventricular size2. Largely extra-axial above tentorium3. No disruption of hemispheric tissue4. Shorter transit to the diencephalic roof5. Ability to develop exposure of the entire IIIrd ventricular

cavityDisadvantages1. Damage of parietal bridging veins2. Excessive parietal lobe retraction3. Poor landmark identification4. Split corpus callosum5. Risk of damage to deep venous structures6. Poor visualization of the pineal and quadrigeminal regions

retraction of the inferior hemisphere to assist in thedevelopment of the parafalcine corridor. At cran-iotomy, the medial bone flap over the midline is desir-able to expose the sagittal sinus, but the anterior flapnever reaches as far anteriorly as motor strip [33].The dura is then reflected towards the sagittal sinus.Although there are at times some parasagittal bridgingveins at the posterior one-third of the sagittal sinus, wecan usually go safely to the corpus callosum betweenthe parasagittal bridging veins and thus preserve them.However, it is known that the division of these veinsdoes not significantly compromise venous drainage inthis portion of the hemisphere [32]. The parietal lobe isgently retracted away from the falx to expose the cor-pus callosum. It is generally not necessary to exposethe splenium, but if necessary, either falx, tentoriumor both may be divided to gain a wide exposure of thepineal region. After the division of the arachnoid overthe corpus callosum, the distal anterior cerebral arteryas well as the splenial branches of the posterior cerebralartery are identified. The majority of tumors involvingthe pineal region can be managed without incising thesplenium. In the case of most pineal region tumors, thecorpus callosum and the fornix become thin, and it isrelatively easy to incise the posterior part of the bodyof the corpus callosum and the hippocampal commis-sure to reach the third ventricular cavity. During thecallosal incision, care should be taken not to divide thesplenium to prevent postoperative disconnection syn-drome [33]. If the splenial section is necessary, the leftoccipital region should be protected, because this car-ries the risk of producing an alexia without agraphiaor a right homonymous hemianopsia [32]. As in themost pineal region tumors, the internal cerebral veins

274

are situated over the tumor, and the tumor removal canbe accomplished around these veins with a variety ofmicrosurgical techniques. The quadrigeminal plate andthe brainstem are not well visualized in this approachuntil the tumor has been removed. Therefore, the brain-stem function should be carefully monitored during theoperation [33].

From these characteristics of this approach, the pos-terior transcallosal approach is best suited for the pinealregion tumor that appears to arise in the corpus callo-sum above the vein of Galen and extend into the pos-terior third ventricle [27].

Posterior transcortical approach

The posterior transcortical approach is only indicatedwhen the ventricle is dilated (Table 4) [17,27]. Thisapproach was first performed by Van Wagenen [13]through an extensive parieto-temporal cortical incision.The main disadvantages of this approach are too lateraland too much damage of the cortex [18]. Therefore, theother preferable approach in the posterior transcorticalapproach is through the superior parietal lobule [27].This high parietal transcortical approach is preferredbecause the cortical incision avoids the visual pathwayand speech area.

This approach is usually performed with the patientin the prone position [34]. After craniotomy of a highparietal flap, the cortical incision is made coronallybehind the postcentral gyrus. The main advantage ofthis approach is an easy identification of the junctionof the body and atrium of the lateral ventricle (Table 4)[17]. The taenia fornicis at the trigone is opened toexpose the upper membranous layer of the roof of thethird ventricle by way of the choroidal fissure. Another

Table 4. Advantages and disadvantages of the posteriortranscortical approach

Advantages1. Preservation of visual and speech pathways2. Ease of landmark identification3. Good visualization of the contralateral IIIrd ventricular

cavity4. Ability to develop exposure of the entire IIIrd ventricular

cavityDisadvantages1. Requires hydrocephalus2. Divides parietal region cortex3. Risk of fornix damage4. Risk of damage to the deep venous structures5. Poor visualization of the ipsilateral IIIrd ventricular cavity6. Poor visualization of pineal and quadrigeminal regions

alternative to reach the third ventricular cavity is theincision of the thin medial wall of the lateral ventri-cle formed by the body and the crus of the fornix. Theinternal cerebral vein, the great vein of Galen and themedial posterior choroidal artery and its branches usu-ally block the exposure of the quadrigeminal region.

This approach is essentially a lateral approach with ahigh morbidity resulting from the cortical incision anddoes not provide satisfactory exposure of the typicalmidline pineal region tumor [27].

Combined supra/infratentorial-transsinusapproach to large pineal region tumors

Sekhar and Goel [14] first reported the com-bined supra/infratentorial-transsinus approach for theremoval of a large tentorial meningioma. This approachprovides the greatest exposure for the large pinealregion tumors and requires less brain retraction thanany other approaches to the pineal region [35].

The patient is placed in a semiprone position anda U-shaped scalp incision is made. The craniotomyis then performed in three pieces, with the suboccipi-tal plate removed first. After separating the transversesinus under direct vision, an occipital craniotomy ismade on one side up to the superior sagittal sinus. Afterseparating the sagittal sinus from the bone, the occip-ital craniotomy is performed on the other side. Theoccipital dura is opened in a transverse fashion justinferior to the transverse sinus, dividing the occipitalsinus, if necessary. The occipital dura is then opened onthe inferior side, medial to the sagittal sinus and supe-rior to the transverse sinus. The non-dominant trans-verse sinus and the tentorium are sectioned. A gentleretraction of the occipital lobe as well as the cerebellumprovides an adequate view of the pineal region. Theexcision of the tumor is accomplished in the usual fash-ion. After removal of the tumor, the transverse sinuscan be sutured, if necessary [35].

References

1. Horsley V: Discussion. Proc R Soc Med 3: 2, 19102. Krause F: Operative Freilegung der Vierhugel Nebst

Beobachtungen uber Hirndruck und Dekompression. ZentblChir 53: 28122819, 1926

3. Stein BM: The infratentorial supracerebellar approach topinel lesions. J Neurosurg 35: 197202, 1971

4. Brunner C (cited by Rorschach H): Zur Pathologie und Oper-abilitat der Tumoren der Zirbeldruse. Beitr Klin Chir 83:451574, 1913

275

5. Poppen JL: The right occipital approach to a pinealoma.J Neurosurg 25: 706710, 1966

6. Jamieson KG: Excision of pineal tumors. J Neurosurg 35:550553, 1971

7. Lasar ML, Clark K: Direct surgical management of massesin the region of the vein of Galen. Surg Neurol 2: 1721,1974

8. Dandy WE: An operation for the removal of pineal tumors.Surg Gynecol Obstet 33: 113119, 1921

9. Horrax G: Extirpation of a huge pinealoma from a patientwith pubertas praecox: a new operative approach. ArchNeurol Psychiatry 37: 385397, 1937

10. Kunicki A: Operative experience in 8 cases of pineal tumor.J Neurosurg 17: 815823, 1960

11. Araki C: Removal of the pineal tumor. Gekashinryo 2:517524, 1960 (Jpn)

12. Suzuki J, Iwabuchi T: Surgical removal of pineal tumors(pinealomas and teratomas). Experience in a series of19 cases. J Neurosurg 23: 565571, 1965

13. Van Wagenen WP: A surgical approach for the removal ofcertain pineal tumors: a report of a case. Surg Gynecol Obstet53: 216220, 1931

14. Sekhar LN, Goel A: Combined supratentorial and infraten-torial approach to large pineal-region meningioma. SurgNeurol 37: 197201, 1992

15. Yamamoto I, Rhoton AL, Peace DA: Microsurgery of thethird ventricle: Part 1, Microsurgical anatomy. Neurosurgery8: 334356, 1981

16. Bruce JN, Stein BM: Infratentorial supracerebellarapproach. In: Apuzzo MLJ (ed) Surgery of the Third Ven-tricle. Williams & Wilkins, Baltimore, 1998, pp 697719

17. Yamamoto I: Surgical approaches and anatomy of the pinealregion. In: Gibo H (ed) Surgical Anatomy for Microneuro-surgery V. SciMed Publications, Tokyo, 1998, pp 97107(Jpn)

18. Lapras C, Patet JD: Controversies, techniques and strategiesfor pineal tumor surgery. In: Apuzzo MLJ (ed) Surgery ofthe third ventricle. Williams & Wilkins, Baltimore, 1998,pp 787799

19. Reid WS, Clark WK: Comparison of the infratentorial andtranstentorial approaches to the pineal region. Neurosurgery3: 18, 1978

20. Ausman JI, Malik GM, Dujovny M, Mann R: Three-quarterprone approach to the pineal-tentorial region. Surg Neurol29: 298306, 1988

21. Kobayashi S, Sugita K, Tanaka Y, Kyoshima K: Infraten-torial approach to the pineal region in the prone position:concorde position. J Neurosurg 58: 141143, 1983

22. Hasegawa M, Yamashita J, Yamashima T: Anatomical vari-ation of the straight sinus on magnetic resonance imaging inthe infratentorial supracerebellar approach to pineal regiontumors. Surg Neurol 36: 354359, 1991

23. Matsushima T, Rhoton AL, Oliveira E, Peace DA: Microsur-gical anatomy of the vein of the posterior fossa. J Neurosurg59: 63105, 1983

24. Page LK: The infratentorial-supracerebellar exposure oftumors in the pineal area. Neurosurgery 1: 3640, 1977

25. Sano K: Pineal region and posterior third ventricular tumors:surgical overview. In: Apuzzo MLJ (ed) Surgery of the thirdventricle. Williams & Wilkins, 1998, pp 801819

26. Bruce JN, Stein BM: Supracerebellar approach for pinealregion neoplasms. In: Schmidek HH, Sweet WH (eds)Operative Neurosurgical Techniques. W.B. Sounders Co,Philadelphia, 1995, pp 755763

27. Rhoton AL, Yamamoto I: Microsurgery of the third ventri-cle: Part 2, Operative approaches. Neurosurgery 8: 357373,1981

28. Yamamoto I, Kageyama N: Microsurgical anatomy of thepineal region. J Neurosurg 53: 205221, 1980

29. Clark WK, Batjer HH: The occipital transtentorial approach.In: Apuzzo MLJ (ed) Surgery of the third ventricle.Williams & Wilkins, Baltimore, 1998, pp 721741

30. Yamamoto I, Sato H, Sato M: Obliteration and its conse-quences for the deep venous system in surgical approachesto the third ventricle. In: Hakuba A (ed) Surgery of theIntracranial Venous System. Springer-Verlag, Tokyo, 1996,pp 321329

31. Harris W, Cairns H, Adelaide MB: Diagnosis and treatmentof the pineal tumors with report of a case. Lancet 1: 39,1932

32. McComb JG, Levy ML, Apuzzo MLJ: The posterior inter-hemispheric retrocallosal and transcallosal approaches tothe third ventricle region. In: Apuzzo MLJ (ed) Surgery ofthe Third Ventricle. Williams & Wilkins, Baltimore, 1998,pp 743777

33. Hoffman HJ: Transcallosal approach to pineal tumors andthe hospital for sick children series of pineal region tumors.In: Neuwelt EA (ed) Diagnosis and Treatment of PinealRegion Tumors. Williams & Wilkins, Baltimore/London,1984, pp 223235

34. Hongo K, Kobayashi S: The posterior transcorti-cal approach. In: Apuzzo MLJ (ed) Surgery of theThird Ventricle. Williams & Wilkins, Baltimore, 1998,pp 683696

35. Ziyal IM, Sekhar LN, Salas E, Ilan WJ: Combinedsupra/infratentorial-transsinus approach to large pinealregion tumors. J Neurosurg 88: 10501057, 1998

Address for offprints: Isao Yamamoto, Department of Neurosurgery,Yokohama City University School of Medicine, 3-9 Fukuura,Kanazawa-ku, Yokohama 236-0004, Japan; Tel.: 045-787-2663; Fax:045-783-6121; E-mail: yisao@med.yakohama-cu.ac.jp