Arq Neuropsiquiatr 2005;63(1):50-54

Hospital da Força Aérea do Galeão, Rio de Janeiro RJ, Brasil, (HAFG); Hospital Universitário Antonio Pedro da Universidade FederalFluminence, Niterói RJ, Brasil (HUAP); 1Assistente de Neurocirurgia do HFAG; 2Estudante da Graduação da Faculdade de Medicina,da Universidade Federal do Rio de Janeiro (UFRJ) Rio de Janeiro RJ, Brasil; 3Serviço de Neurocirurgia do HFAG e HUAP

Received 23 June 2004. Accepted 27 September 2004.

Dr. José Alberto Landeiro - Avenida Monsenhor Ascâneo 591/202 - 22621-060 Rio de Janeiro RJ - Brasil.

COMBINED SUPRA/INFRATENTORIAL APPROACHTO TENTORIAL MENINGIOMAS

Igor de Castro1, Daniel de Holanda Christoph2, José Alberto Landeiro3

ABSTRACT - In spite of significant advancements in imaging technology, monitoring, and microsurgical techni-ques, complete and safe removal of tentorial meningiomas remains a challenge for most neurosurgeons.Classifications of tentorial meningiomas are revised. The combined supra/infratentorial approach to resectstentorial meningioma is discussed. This approach provides a wider exposure of the supra/infratentorial regionwith less brain retraction. With this approach the occipital lobe and the cerebellum are exposed along thetentorium. Two illustrative cases are presented. The patients were studied with computerized tomogra-phy, magnetic resonance and angiography. The anatomy of the transverse sinus and the confluence of thesinus could be appreciated with these studies. The operative technique is described stepwise. Emphasis isplaced on pre-operative evaluation and surgical technique, leading to a total surgical removal of the lesionwith margins of safety. The goal of surgical treatment of tentorial meningiomas is their complete and saferemoval. With this unique approach we sought to confirm that it offers a safe means of resection not onlythe neoplasm but also the infiltrated dura.

KEY WORDS: tentorial meningioma, surgical approach, supra/infratentorial, combined craniotomy.

A b o rdagem combinada supra e infratentorial aos meningiomas tentoriais

RESUMO - Apesar dos significativos avanços na tecnologia de imagens, nas técnicas de monitorização emicrocirúrgicas, a ressecção completa e segura dos meningiomas tentoriais permanece um desafio paramaioria dos neurocirurgiões. A abordagem supra e infra-tentorial proporciona ampla exposição das regiõessupra e infratentoriais diminuindo a retração cerebral. Com esse tipo de abordagem o lobo occiptal e ocerebelo são expostos ao longo da superficie tentorial. Dois casos ilustrativos são apresentados. Os pacientesforam avaliados com tomografia computadorizada, ressonância magnética e angiografia, o que permitiuestudar a anatomia do seio transverso, a confluência e dominancia dos seios. O objetivo do tratamento ci-rúrgico dos meningiomas tentoriais é a remoção completa e segura. A associação das imagens, o acessocombinado e a técnica microcirúrgica permitem a remoção cirúrgica total deste tipo de lesão e do implantedural com margens de segurança.

PALAVRAS-CHAVE: meningioma tentorial, craniotomia, supra/infratentorial.

The first report of a tentorial meningioma wasin 1833 by Andraal, who discovered a lesion inciden-tally attached to the tentorium1. Tentorial menin-giomas account for 2% to 3% of all intracranial me-n i n g i o m a s2 - 5. In the Cushing and Eisenhard’s seriesof 295 intracranal meningiomas, 11 tumors (3.7%)were attached to the tentorium6. Olivecrona7 s e r i e sincluded 21 tentorial meningiomas representing2.5% of all of their intracranial meningiomas. Hefound in his series 52% of these lesions above thetentorium and 48% below. The transverse sinus wasinvaded in 52%7 . In a such way the first attempt toclassify the tentorial meningioma was made by h i m .To discuss the surgical management of tentorial me-

ningiomas appropriately, one must be based ontheir site of origin. With this finality many authorsproposed different classifications of the posteriorfossa meningiomas1 , 8 , 9. In the era pre computerizedtomography (CT), the majority of the authors agre-ed that the tentorium was the most common siteof the posterior fossa meningioma10. With the ad-vent of CT in the early 1970s, numerous authors h a v eattempted to lend order to these lesions by assingn-ing classification9 , 1 1 - 1 5. According with Harrison andA l - M e f t y1 6 we find the scheme proposed by Ya s a r g i lwas the one of the most beneficial15,16. The choiceof operative approach depends mainly on the siteof the lesion. The size of the lesion will dictate the

Arq Neuropsiquiatr 2005;63(1) 51

size of the craniotomy. The majority of the pure-ly tentorial tumors can be removed by the authorproposed approach. The combined supra/infraten-torial approach is a modified adaptation of the ap-proach described by Ziyal et al. for pineal tumors1 7.In his publication he mentioned a successful remo-val of 4 tentorial meningioma, but differing fromour approach, a more flap craniotomy and sinusligation were used. The experience gained with theposterior fossa craniotomy stimulated the authorsto perform a single flap craniotomy involving thesupra/infratentorial compartments to remove ten-torial meningiomas1 8. The proposed approachproves to be safe and easy to perform after appro-priate training with the high power surgical drilland craniotomy. There is no need for two or moreflap craniotomies or subocciptal craniectomies. T h epreoperative evaluation and the surgical approachitself will be described in detail.

PREOPERATIVE EVALUATIONIn all patients with tentorial meningiomas, a contrast-

enhanced CT scan and a magnetic resonance (MRI) ofthe brain should be ordered. The CT scan in axial andcoronal views should be carefully evaluated to see therelations of the lesion with the falx and tentorium. TheCT images still provide superior bone detail and are in-valuable where tumors invade bones. The MRI is moreprecise on revealing information about tumor localiza-tion, extension and its relations. Special attention shouldbe given to where the tumor expands mostly into thetwo compartments. In fact with, MR and MR angiogra-phy (MRA) the size, dominance and collateralization ofthe transverse sinuses can be recognized. This factor isessential for this kind of approach. We should obtain allpossible possible about the transverse sinus status. If infil-tration is present, it should be quantified.

Cerebral angiography is sometimes necessary to ob-tain additional information about the arterial and venoussystem. Using the four-vessels angiography we are ableto delineate the vascularity of the lesion and its relation-ship to the various arteries and veins in this area. Thecirculation supplying the tumor is carefully analyzed inorder to plan both endovascular and surgical procedu-res. The vein of Galen, the internal cerebral veins andthe basal vein of Rosenthal should be studied. As wellas the superficial venous system, with the patency of thestraight sinus, and the collateralization and enlargem e n tof the normally present sinus should also be analyzed.Preoperative embolization can be used since it is readi-ly available through a very experienced neuroradiol o g i s tin the procedure. If the embolization is effective the surgi-cal procedure become easier 8.

If the sitting position is planned to approach the ten-torial meningiomas a complete evaluation of the cervi-

cal spine is mandatory. X-rays and MR of the cervical spineshould be studied carefully to avoid complications withthe positioning.

OPERATIVE TECHNIQUEThe patient is positioned in a sitting position, which

is prefer by the senior author (JAL) to deal with lesionsin the posterior fossa for more than fifteen years. Withthis position, the surgical field remains clean during thewhole procedure. The venous pressure is very low andthere is less venous bleeding. The main disadvantage ofthis position is the occurrence of air embolism which israpidly and precisely diagnosed with the trans-esophagealD o p p l e r. The air can be aspirated from the right atriumwith the central lines placed in the correct position pre-o p e r a t i v e l y.

After appropriate preparation and draping, a U-sha-ped or linear incision is made. The preference of the kindof the incision is dictated by the size of the tumor. Subse-quently the skin flaps and muscle are retracted in a sin-gle layer. The craniotomy is performed in a single piece.The size of the craniotomy is also dictated by the size ofthe tumor. We place burr holes above and below the t r a n s-verse sinus and in a majority of the times, the bone overthe sinus is drilled away. For the superior and inferior c o m-ponents of the craniotomy the craniotome can be per-fectly used after the dura is dissected from the bone (Fig1). After the craniotomy, the dura of the occipital lobeand the suboccipital compartment are exposed. Thetransverse sinus is placed between both compartments.The transverse sinus and its junction with the torcularHerophilli are exposed (Fig 2).

The suboccipital dura is opened in a transverse tri-angular fashion just inferior to the transverse sinus. Thistype of opening facilitates the subsequently water- t i g h tclosure. The cisterna magna is opened to permit the relax-ation of the brain. Then, the occipital dura is opened inthe same fashion, just superior to the transverse sinusand laterally to the superior sagittal sinus. If the liga-tion of the sinus is planned, a judicious investigation withMR, MRA and venous phase of angiography should beperformed. If the sinus is already occluded with tumor,the sinus can be divided and removed. After the duraopening of the both compartments, the surgeon can ap-preciate the wide exposure of the tumor along the ten-torium (Fig 3). Using microsurgical techniques, the sur-geon should start with the evacuation of the tumor c o n-tent. Gentle traction was exerted on the capsule to sep-arate it from the neighboring vasculonervous structu-res. In this maneuver, the surgeon must distinguish thevessels and the nerves that lie outside the tumor and havebeen displaced and stretched from those embedded inthe tumor. In the first situation, the vessels and thenerves must be gently separated and protected withsponges. The small arteries that supply the tumor mustbe identified and not stretched, in order not to tear themat the base of insertion; they should be coagulated andsectioned flush with the tumor. Then the tumor can be

52 Arq Neuropsiquiatr 2005;63(1)

Fig 1. The craniotomy. The burr holes are placed above and be -low the transverse sinus. The craniotome is avoided over thesinus. The drill is used in stead. The tranverse sinus and itsjunction at the sinuses confluence is appreciated.

Fig 2. Dural opening. The opening of the dura is tailored in atransverse triangular fashion to facilitate the closure. The occip -ital and the sub occipital dura are opened independently. Thetransverse sinus is not divided and remains in the middle of thetwo openings.

Fig 3. Tumor visualization. After the dura opening the tumorcan be seen along the tentorial surface. The tumor can be rea -

ched from above or below.

Fig 4. Gross total resection. After the total tumor resection theintegrity of the occipital lobe and cerebellar hemisphere is

completely preserved as well as the venous sinuses.

Arq Neuropsiquiatr 2005;63(1) 53

radically removed. In cases in which the nerves and thevessels are embedded in the tumor, the use of higher m a g-nification and a piecemeal technique removal aroundthose structures should be applied. Often, in some cas-es when there is not a plan at all, it is wise to leave a t h i nlayer of the tumor around the arteries and nerves. For t h o-se kind of microsurgical dissection, a precise bipolar c o a-gulation technique is essential. Usually the tumor displa-ces the normal structures and after the debulking, no r e-traction is really necessary. The use of the Cavitron ultra-sonic surgical aspirator (CUSA) has proved to be useful.It is specially valuable to decompress a large tumor withsoft consistency. After removal of the tumor, the infil-trated dura must be removed as much as possible. Thetentorium is cut just lateral to the straight sinus and to-ward the tentorial notch. To our point of view with thisapproach, one can visualize the entire tentorium fromabove and below, facilitating extremely this dural re-moval. After the complete removal of the tumor and thetentorium, the occipital lobe and the cerebellum are easi-ly visible (Fig 4). Ilustrative cases are demonstrated in figu-res 5 and 6.

DISCUSSION

As with all meningiomas, tentorial tumors aremore common in females in middle- to older age.Tentorial meningiomas are relativily rare lesionswhich present difficult diagnostic and surgical pro-blems. Despite the fact that tumors in this locationrepresent less than 3% of all meningiomas, theirfrequent involvement with dural venous sinuses,

deep venous structures, plus the brainstem and thecranial nerves, they have led to interest far excee-ding their rate of occurance16.

The choice for the appropriate surgical approachis based upon the site of origin of the lesion. This i sof paramount importance in determining the easeof resectability. By careful study of the preoperati-ve diagnostic tests, the surgeon should form a m e n-tal image of the location of the tumor and its rela-tionship to major vascular and neural structures.

During the approach, the surgeon must establishclose working with the neuro-anesthesiologist, sus-pending the operation momentarily if any symptomor sign of air embolism is present. The presence ofa well positioned central line and trans-esophagealDoppler is mandatory to avoid any complication.

Numerous authors have attempted to lend o r d e rto these lesions by assingning classification9 , 1 1 - 1 5. Ac-cording with Harrison and Al-Mefty, we find thescheme proposed by Yasargil was the one of themost beneficial1 5 , 1 6. The schematic classificationproposed by Yasargil is very useful. Under his clas-sification, he called T1-T3 the lesions on the innerring or lesions of the incisura - anterior, lateral a n dposterior. T4 and T8 are intermediate ring lesionswith T8 tumors involving the falcotentorial junc-tion. T5-T7 are lesions on the posterior ring, involv-ing the torcular, transverse sinus, and transverse-sigmoid junction respectively15.

The approach presented by us is more indicat-ed to deal with tumors type 4 and 6 according tothis classification. Torcular meningiomas are oftenaddressed separately from other tentorial menin-giomas. Tumors of the torcular region require ex-posure of what has been referred to as all “fourq u a d r a n t s ”6. This includes visualization of the supe-

Fig 5. Pre-operative T1-weigthed MRI with contrast in sagitaland a coronal projections (A) of tentorial meningioma with bothsupra and infratentorial extension and postoperative MRI withcontrast in sagittal and coronal plane (B) depicting the resection.

Fig 6. Coronal T1 weighted MRI (A) with a contrast of an oldpatient with a large tentorial meningioma with supratentorialextension. A immediately postoperative coronal (B) MRI stud -ies displaying total resection.

54 Arq Neuropsiquiatr 2005;63(1)

rior sagittal sinus, torcular Herophilli, both transver-se sinuses, and the occipital sinus proximal and d i s-tal to what is involved with tumor. Tumors that arisefrom the intermediate ring of the tentorium (T4),that do not involve the medial structures and thatdo not invade the dural venous sinuses are, theore-t i c a l l y, the easiest ones to be managed with the pro-posed approach.

In the literature one can find that depending o ntumor extension supra-, infratentorially, or both, aoccipital, suboccipital, or a combined approach m a ybe used.

Where a tumor has only minimal extension intoeither the supra- or infratentorial compartiment,it can be resected via an approach solely on the sideof the sinus with maximum tumor1 6. Originally t h a tthe lateral and medial tumors with solely or main-ly supratentorial development were approachedfrom above. The approach from below was reservedfor meningiomas with subtentorial involvement on-l y. In meningiomas with both supra- and infratento-rial growth, a supratentorial flap was combined wi-th a subocciptal craniectomy5. With our approachthere is no place for craniectomy. However a sin-gle bone flap of the two compartiments can be eas-ily performed. We think that even for a single le-sion occupying compartment a combined cranio-tomy can play an important role. Not only as a wideavenue to remove the tumor but also the infiltrat-ed dura can be easily investigated and removed. I nour approach to tentorial meningioma the resect i o nof a part of the falx or the tentorium is relatively e a s y.

We think that, regardless the extension of thet u m o r, with our proposed approach the tumor anddural resection become easier. The goal to avoid re-currence is to remove the tumor and its implanta-t i o n1 9. If the tumor can be removed with a 2-cm mar-

gin of the tentorium peripheral to the tumor atta-chment, the so-called Grade 0 proposed by Kinjo etal. can be achieved2 0. If this kind of resection is donewe diminish the risk of recurrence almost to zero.

REFERENCES1. Yasargil MG, Mortara RW, Curcic M. Meningiomas of the basal poste-

rior cranial fossa In Krayenbhul H (ed): Advances and technical standar-ds in neurosurgery. New York: Springer-Verlag, 1980;7:3-115.

2. Barrows HS, Harter DH. Tentorial meningiomas. J Neurol NeurosurgPsychiatry1962;25:40-44.

3. Castellano F, Ruggiero G. Meningiomas of the posterior fossa. Acta Ra-diol (Stockh) 1953;104:(Suppl):26-69.

4. McCarty CS, Taylor WF. Intracranial meningiomas: experiences at Ma-yo Clinic. Neurol Med Chir (Tokyo) 1979;19:569-574.

5. Guidetti B, Ciappetta P, Domenicucci M. Tentorial meningiomas: surg i-cal experience with 61 cases and long-term results. J Neuro s u rg 1988;69:183-187.

6. Cushing H, Eisenhardt L. Meningiomas. Springfield: Charles C Tho-mas,1938:506-537.

7. O l i v e c rona H. The surgical treatment of intracranial tumors In Lohr HH,Luft R, Olivecrona H, et al (eds). Klinik und Behandlung der raumbeen-genden intrakraniellen Prozesse. Handbuch der neurochirurgie, BandIV. Berlin: Springer-Verlag, 1967;4:179-181.

8. Sekhar LN, Janetta PJ, Maroon CJ. Tentorial meningiomas: surg i c a lmanagement and results. Neurosurgery 1984;14:268-275.

9. Ciric I, Landau B. Tentorial and posterior cranial fossa meningiomas:operative results and long-term follow-up: experience with twenty sixcases. Surg Neurol 1993;39:530-537.

10. Carey JP, Fisher RG, Pelofsky S. Tentorial meningiomas. Surg Neurol1975;3:41-44.

11. Gokalp HZ, Arasil E, Erdogan A, Egemen N, Deda H, Çerçi A. Te n t o r i a lmeningiomas. Neurosurgery 1995;36:46-51.

12. Malis L. Surgical approaches to tentorial meningiomas. In Wilkins RH,Rengachary SS (eds). Neuro s u rgery update: I. diagnosis, operativetechnique, and neuro - o n c o l o g y. New York: McGraw-Hill,1990;399-408.

1 3 . Sen C. Surgical approaches to tentorial meningiomas. In. Wilkins RH,Rengachary SS (eds). Neuro s u rg e r y. New York: McGraw-Hill,1996;917-9 2 4 .

14. Sugita K, Suzuki Y: Tentorial meningiomas, In Al-Mefty O(ed):Meningiomas. New York: Raven Press, 1991:357-361.

15. Yasargil MG. Microneurosurgery. Stuttgart: Thieme, 1996;4B:134-161.16. Harrison MJ, Al-Mefty O. Tentorial meningiomas. Clin Neuro s u rg .

1997;44:451-466.17. Ziyal IM, Sekhar LN, Salas E, Olan WJ. Combined supra/infratentor-

ial-transsinus approach to large pineal region tumors. J Neuro s u rg1998;88:1050-1057.

18. L a n d e i ro JA, Castro ID, Flores MS, Maia OT Jr. Posterior fossa cranioto-my: technical report. Arq Neuropsiquiatr 2000;58:169-173.

19. Simpson D. Recurrence of intracranial meningiomas after surg i c a ltreatment. J Neurol Neurosurg Psychiatry 1957;20:22-39.

20. Kinjo T, Al-Mefty O, Kanaan I. Grade zero removal of supratentorialconvexity meningiomas. Neurosurgery 1993;33:394-399.