Falcotentorial meningioma

J Neurosurg 104:47–53, 2006

Falcotentorial meningioma: surgical outcome in 14 patients TAKEO GOTO, M.D., KENJI OHATA, M.D., MICHIHARU MORINO, M.D., TOSHIHIRO TAKAMI, M.D., NAOHIRO TSUYUGUCHI, M.D., AKIMASA NISHIO, M.D., AND MITSUHIRO HARA, M.D.

Department of Neurosurgery, Osaka City University Graduate School of Medicine, Osaka, Japan

M

Object. The authors evaluated their surgical experience over 20 years with 14 treated falcotentorial meningiomas. Methods. In the past 20 years, 14 patients with falcotentorial junction meningiomas were surgically treated. There were seven men and seven women, whose ages ranged from 34 to 79 years. On the basis of neuroimaging studies, the authors analyzed the influence of the anatomical relationship of the tumor to the vein of Galen, patency of the vein of Galen, tumor size, and the signal intensities on the magnetic resonance images to determine possible difficulties that might be encountered during surgery and to prognosticate the outcome of surgery. Depending on the relationship with the vein of Galen, tumors were labeled as either a superior or an inferior type. All tumors were resected via an occipital transtentorial approach. The surgical outcome in eight patients was excellent; in the remaining six patients, it was fair. Of the prognostic factors, tumor location especially seemed to be the most important (p , 0.01, Fisher exact test). The outcome associated with the inferior type of tumor was significantly less optimal probably due to the relationship to the deep veins and the brainstem. In this series, the occlusion of deep veins did not significantly influence outcome. Conclusions. Classification of the tumor location by preoperative neuroimaging studies can be helpful in estimating the surgical difficulty that might be encountered in treating the falcotentorial junction meningioma.

KEY WORDS • meningioma • falcotentorial junction • galenic system

ENINGIOMAS arising from the falcotentorial junction

are relatively rare, and only isolated case reports or small series related to surgical technique are available in the literature.1,5,7,8,11–13,16 Because of the lesion’s depth from the surface and its anatomical proximity with critical neural and vascular structures, surgical access and technique are complex issues. A variety of factors influence surgery and outcome. In this paper, on the basis of our experience, we analyze a set of factors to determine which probably influence surgical outcome. Clinical Material and Methods Patient Population and Tumor Characteristics During the years between 1984 and 2004, 14 patients with falcotentorial junction meningiomas were surgically treated at our institution by the two senior surgeons (A. Hakuba and K.O.). Pineal region meningiomas that did not have a dural base in the falcotentorial region were not included in this series. There were seven men and seven women whose ages ranged from 34 to 79 years (mean 57 years; Table 1). The chief presenting symptoms included severe headache in five, memory disturbance in five, gait disturbance in two, and tinnitus in two patients. All tumors were exposed via an occipital transtentorial approach. The side of the surgical approach was dependent on the predominant side of tumor extension. Four tumors were approached on the right side and five on the left. In five tumors the approach was bilateral because the tumor extended widely on both sides of the midline. Total resection of the tumor was Abbreviation used in this paper: MR = magnetic resonance.

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achieved in 11 patients, and subtotal tumor removal in three. Among the 11 patients, eight had no postoperative neurological worsening except for transient hemianopia; the other three patients experienced postoperative permanent neurological deterioration, including memory disturbance and hemianopia. Among the three patients who had undergone a subtotal tumor removal, no neurological deterioration occurred postoperatively. Surgical outcome was graded as satisfactory in eight patients (Cases 1–8) given that the tumors had been totally removed and there was no permanent neurological deterioration. Outcome was unsatisfactory in six patients (Cases 9–14) because either the lesions were not totally removed or the patients had permanent functional deterioration following total tumor removal.

Analysis of Prognostic Factors

Preoperative neuroimaging investigations included MR imaging, MR venography, and angiography. Apart from evaluating the physical characteristics of the tumor, we evaluated the relationship of the tumor to the great vein of Galen, the patency of the vein of Galen, and the straight sinus. Depending on the relationship of the tumor to the great vein of Galen, tumors were classified into two types: tumors located superior to the vein and compressing it downward were labeled as the superior type, whereas those displacing it superiorly were labeled as the inferior type (Fig. 1). To evaluate prognostic factors, preoperative neuroimaging findings and surgical findings were analyzed in eight patients (Cases 1–8) with satisfactory outcomes and six (Cases 9–14) with unsatisfactory outcomes. Neuroimaging findings were statistically compared between these two groups. 47

T. Goto, et al. TABLE 1 Summary of characteristics in 14 patients with falcotentorial junction meningiomas

Case No.

Age (yrs), Sex

10 11 12 13 14

49, F 62, F 79, M 57, F 61, M

1 2 3 4* 5 6 7 8 9

49, F 50, F 55, F 54, M 47, M 63, M 34, M 69, M 69, F

Chief Symptom

Extent of Tumor Removal

headache gait disturbance gait disturbance tinnitus memory disturbance

total total subtotal subtotal subtotal

headache headache memory disturbance memory disturbance headache memory disturbance tinnitus headache memory disturbance

total total total total total total total total total

* The MR imaging unit was not used before surgery in this case.

Results Neuroimaging characteristics and surgical results are summarized in Table 2. In the satisfactory-outcome group (Cases 1–8), the tumor did not tightly adhere to the straight sinus, deep veins (great vein of Galen and basal vein), collateral venous channels, or brainstem. Only one patient (Case 3) required suturing of the injured venous wall at a single point during surgical procedures. This situation enabled the surgeons to remove the tumor totally without surgical complication. On the other hand, in the three cases (Cases 9–11) in which there was an unsatisfactory outcome, there was tight adhesion or proximity between the tumor and collateral venous channels of the deep veins. In all of these three cases, there was intraoperative injury to the deep veins or collateral veins during resection of the tumor. All of these patients suffered postoperative venous infarction associated with memory disturbance and hemianopia. The cause of memory disturbance was unclear, although it was

Complications

none none none none transient hemianopia none none none deterioration of memory & hemianopia hemianopia memory disturbance none none none

Follow Up (mos)

238 221 220 217 187 90 70 51 126 72 60 50 41 38

Outcome Group

satisfactory satisfactory satisfactory satisfactory satisfactory satisfactory satisfactory satisfactory unsatisfactory unsatisfactory unsatisfactory unsatisfactory unsatisfactory unsatisfactory

presumed to be due to postoperative dysfunction of the left mesial temporal lobe structures, which was related to compromise of the left basal vein of Rosenthal or the left internal cerebral vein. Based on the lessons learned from our experience with the initial three cases, a small amount of the tumor was left behind to avoid injury to the deep veins, collateral veins, and brainstem in the subsequent three cases (Cases 12–14). Tumor Location Related to the Great Vein of Galen

In the satisfactory-outcome group, seven tumors were classified as the superior type and one tumor as the inferior type. On the other hand, in the unsatisfactory-outcome group all six tumors were classified as the inferior type. The location type was significantly different between the two outcome groups (p , 0.01, Fisher exact test).

Occlusion of the Great Vein of Galen and the Straight Sinus

In the satisfactory-outcome group, preoperative investigations suggested occlusion of the great vein of Galen in one case and of the straight sinus in another case. In the unsatisfactory-outcome group, there were three cases of venous occlusion, one of which involved occlusion of the straight sinus and two of which involved occlusion of both the great vein and the straight sinus. Preoperative investigations in all cases with venous occlusion in both outcome groups demonstrated well-developed collateral venous channels. Occlusion of the great vein of Galen and the straight sinus did not significantly influence surgical outcome (p = 0.34, Fisher exact test).

Tumor Size

FIG. 1. Ilustration demonstrating the location type of the tumor. A tumor located over the vein of Galen and compressing it downward was classified as the superior type, and one situated under the vein of Galen and dislocating it upward was the inferior type.

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Tumor size ranged from 22 to 58 mm (mean 38.6 mm). In the satisfactory-outcome group, tumor size was significantly larger than that in the unsatisfactory-outcome group (mean 6 standard deviation, 44 6 9.4 mm compared with 31.3 6 6.1 mm; p , 0.05, Welch t-test). Magnetic Resonance Imaging Intensity of the Tumor

Eleven patients underwent MR imaging studies before J. Neurosurg. / Volume 104 / January, 2006

Falcotentorial meningioma TABLE 2 Neuroimaging characteristics and surgical findings in 14 patients with falcotentorial junction meningiomas* Occlusion of Deep Veins

Outcome Group

satisfactory satisfactory satisfactory satisfactory satisfactory satisfactory satisfactory satisfactory unsatisfactory unsatisfactory unsatisfactory unsatisfactory unsatisfactory unsatisfactory

Case No.

1 2 3 4‡ 5 6 7 8 9 10 11 12 13 14

Tumor Location†

superior superior superior superior superior superior inferior superior inferior inferior inferior inferior inferior inferior

Vein of Galen

Straight Sinus

2 2 2 2 2 2 2 1 1 2 2 1 2 2

2 1 2 2 2 2 2 2 1 2 1 1 2 2

* Iso = isointense; NE = not evaluated; 1 = occluded; 2 = patent. † This prognostic factor significantly influenced surgical outcome. ‡ The MR imaging unit was not used before surgery in this case.

the operation; three patients were treated before the era of MR imaging. On T1-weighted MR images, all tumors in the satisfactory-outcome group and five of six tumors in the unsatisfactory-outcome group appeared isointense. Signal intensity on T1-weighted images was not significantly different between the two outcome groups (p = 0.68, Mann– Whitney U-test). On T2-weighted MR images, four tumors were hyperintense and one was isointense in the satisfactory-outcome patients. In the unsatisfactory-outcome group, the tumor was hyperintense in one case, isointense in two cases, and hypointense in three cases. The T2-weighted signal was significantly greater in the satisfactory-outcome group than that in the unsatisfactory-outcome group (p , 0.05, Mann–Whitney U-test). Illustrative Cases

Case 8. This 69-year-old man presented with a 3-month history of gradually progressing severe headache. There was no neurological deficit at the time of admission. Magnetic resonance imaging demonstrated a large mass at

Tumor Size (mm)†

45 40 50 58 32 32 42 53 31 27 38 40 30 30

MRI Signal Intensity T1

NE NE NE iso iso iso iso iso iso iso iso iso iso low

T2†

NE NE NE high high high high high low iso low low iso high

Surgical Findings

Injuy to Deep or Collateral Veins

Suturing of Vein Wall

2 2 1 2 2 2 2 2 1 1 1 2 2 2

2 2 1 2 2 2 2 2 1 1 1 2 2 2

the falcotentorial junction. The size of the tumor was 53 mm in its maximal diameter. On an angiogram and a MR venogram, the tumor was located over the vein of Galen and dislocated it downward and was classified as the superior type. The vein of Galen was occluded at the point of entry into the straight sinus, and the deep venous flow drained through the collateral venous channels into the petrosal vein and the transverse sinus. The tumor was excised via an occipital transtentorial approach. The tumor had a well-defined plane of dissection from the brainstem, vein of Galen, straight sinus, and collateral veins. The tumor could be totally removed and there was no postoperative complication (Fig. 2). Case 13. This 57-year-old woman, who had presented with a 2-month history of tinnitus, harbored an inferior type of falcotentorial meningioma. Although the size of the tumor was not very large (22 mm in its maximal diameter), it was tightly adhered to the great vein of Galen and basal veins. A small portion of the tumor was left behind around these veins to avoid venous damage (Fig. 3). Postoperatively, there was no neurological worsening.

FIG. 2. Case 8. a: Preoperative sagittal contrast-enhanced T1-weighted MR image demonstrating a superior type tumor. b: An MR venogram demonstrating the anatomical relationship between the vein of Galen and the tumor. c: Postoperative sagittal contrast-enhanced T1-weighted MR image showing total removal of the tumor.

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FIG. 3. Case 13. a: Preoperative sagittal contrast-enhanced T1-weighted MR image revealing an inferior type tumor. b: An MR venogram showing the anatomical relationship between the vein of Galen and the tumor. c: Postoperative sagittal contrast-enhanced T1-weighted MR image demonstrating partial removal of the tumor.

Discussion Our study data suggested that the tumor location in relation to the great vein of Galen was the most significant prognostic factor in surgery for the falcotentorial junction meningioma. Occlusion of the galenic system, however, was not an indicator of excellent surgical outcome. The size of the tumor was not necessarily a prognostic factor given that all of the large tumors in our series were the superior type, could be totally resected, and were associated with a satisfactory outcome. Concerning the MR imaging signal intensity, it is clear that the softer meningiomas can be more easily removed than the firmer ones. A review of the literature demonstrates that preexisting occlusion of the galenic system and the subsequent development of collateral venous circulation is an important factor when considering surgery on pineal region tumors, including falcotentorial junction meningiomas.1,3,9,10,14 In such a situation, however, the collateral venous flow must be preserved.1,7 In the present study in cases of the inferior type tumor with an occluded galenic system, dissecting the tumor from surrounding collateral veins and brainstem was TABLE 3 Relationship between tumor location and surgical outcome in 38 cases

No. of Patients

Authors & Year

Suzuki, et al., 1984

Odake & Goel, 1992

Sekhar & Goel, 1992 Asari, et al., 1995

Matsuda & Inagawa, 1995 Samii, et al., 1996 Ziyal, et al., 1998

Okami, et al., 2001 present study total

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Tumor Location

superior inferior superior inferior superior inferior superior inferior superior inferior superior inferior superior inferior superior inferior superior inferior

Satisfactory Outcome

1 0 0 0 0 0 2 2 1 0 0 2 1 0 1 0 7 1 18

Unsatisfactory Outcome

0 0 1 1 0 1 0 2 1 1 0 4 0 1 2 0 0 6 20

relatively difficult technically. Resection of the tumor in such cases led to damage of the surrounding structures with additional neurological deficits. It appeared that in cases in which the galenic venous system was patent, the surgical procedure was more difficult because the tumor was tightly adhered to the venous system. To prevent injury to the deep vein, a small amount of the tumor can be left behind around the deep veins to avoid their injury in the context of an inferior type tumor. It was observed that in the case of the superior type tumor, even when the vein of Galen was patent, a careful surgical technique enabled the surgeon to separate the tumor from the vein of Galen. As a result, complete surgical removal could be relatively safely performed in the case of superior type tumors. Several types of collateral venous channels developed as a result of occlusions of the galenic system. Based on our study data, it appears that collateral channels under the thick arachnoid septum might be the most functionally and surgically important collateral veins in surgery for the inferior type tumor, because the tumor tends to adhere to all of the galenic system including possible collateral veins in the same cistern. To evaluate the importance of tumor location as a prognostic factor, we reviewed the literature on falcotentorial junction meningiomas from the past 20 years and found 24 cases to which we could apply our classification system of tumor location on the basis of neuroimages and lesion descriptions (Table 3).1,5,7,8,11–13,16 Of the 38 cases—that is, 14 from the present study and 24 from the literature—18 were included in the satisfactory-outcome group and the other 20

FIG. 4. Graph showing the relationship between the tumor location type and surgical outcome. The location of the tumor was significantly different between the two outcome groups (p , 0.01).

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Falcotentorial meningioma

FIG. 5. Drawings depicting the growing process of the superior type falcotentorial junction meningioma. a: The superior type tumor is originally located in the posterior pericallosal cistern. b: As the tumor increases in size, it pushes down the quadrigeminal cistern, including the vein of the Galen and basal veins. The tumor and deep veins are in different cisterns. There is a thick arachnoid membrane between them.

in the unsatisfactory-outcome group. In the satisfactory-outcome group, 13 tumors were classified as the superior type and the other five as the inferior type. In the unsatisfactoryoutcome group, four tumors were categorized as the superior type and the other 16 as the inferior type. Based on our experience with the cases in our study and those reported in the literature, it appears that there is a significant difference in surgical outcome between superior and inferior types of tumor locations (p , 0.01, Fisher exact test; Fig. 4). The reason for the relative difficulty in surgical removal and outcome between superior and inferior types of tumors could be due to the relationship of the arachnoid membrane to the deep veins, brainstem, and tumor. In the normal anatJ. Neurosurg. / Volume 104 / January, 2006

omy, the thick broad arachnoid membrane, extending from the tentorial ridge to the splenium, clearly separates the posterior pericallosal cistern from the quadrigeminal cistern, which includes the great vein of Galen, basal veins, and dorsal midbrain.2,4,6,15 It is most likely that the superior type tumor, growing inside the posterior pericallosal cistern, might compress deep veins over the arachnoid membrane. In this situation, thick arachnoid membrane septum between two cisterns protects the deep veins from direct tumor invasion, which enables the surgeon to dissect the lesion from the deep veins (Fig. 5). On the other hand, the inferior type tumor, growing in the quadrigeminal cistern, might compress the deep veins and dorsal midbrain in direct contact with 51

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FIG. 6. Drawings depicting the developmental pattern of the inferior type falcotentorial meningioma. a: From its beginning, the inferior type tumor grows upward in the quadrigeminal cistern, which contains the deep veins. b: The larger the tumor grows, the more severe it adheres to the deep veins because it exists in the same cistern with the deep veins and there is no arachnoid membrane separating these two structures.

them. Accordingly, in many cases of the inferior type, the tumor tightly adheres to the vein of Galen, basal vein, collateral veins, and midbrain (Fig. 6). The arachnoid membrane provides a barrier to prevent injury of adjacent arteries and nerves during removal of the meningiomas. This principle can be applied to the falcoten52

torial junction meningioma. Certainly, an invasive meningioma, even if it is the superior type, may have adhesions to the deep veins; in comparison with tumors having the same pathological features, however, the surgical difficulty associated with the inferior type tumor is remarkable. Samii, et al.,11 who defined our inferior type of meningioma as a J. Neurosurg. / Volume 104 / January, 2006

Falcotentorial meningioma posteromedial tentorial edge tumor, reported on the surgical difficulty associated with the inferior type of meningioma and suggested that a subtotal tumor removal be performed to prevent unacceptable morbidity. In our study it is clear that the surgical difficulty involved in removing the falcotentorial junction meningioma depends mainly on the anatomical relationship between the tumor and the deep veins. Considering the surgical risk involved in excising the inferior type of meningioma, a combination of subtotal tumor resection and stereotactic radiotherapy might be recommended. As a surgical strategy, there may be some opinion on the occipital transtentorial approach for inferior type tumors. With inferior tumors located below the vein of Galen, a supracerebellar approach might be advantageous because the vein of Galen would not be directly in harm’s way. Surgeons would not have to work through the vein and its tributaries. Hereafter, we must consider a supracerebellar approach to inferior type tumors. Conclusions Classification of tumor location by using preoperative neuroimaging studies can assist the surgeon in evaluating the extent of possible surgical difficulties and in predicting the outcome. References

1. Asari S, Maeshiro T, Tomita S, Kawauchi M, Yabuno N, Kinugasa K, et al: Meningiomas arising from the falcotentorial junction. Clinical features, neuroimaging studies, and surgical treatment. J Neurosurg 82:726–738, 1995 2. Day JD, Koos WT, Matula C, Lang J: Color Atlas of Microneurosurgical Approach. Cranial Base and Intracranial Midline. Stuttgart: Thieme, 1997, pp 260–267 3. Horrax G: Extirpation of a huge pinealoma from a patient with pubertas praecox: a new operative approach. Arch Neurol Psychiatry 37:385–397, 1937 4. Lang J: Clinical Anatomy of the Posterior Cranial Fossa and Its Foramina. New York: Thieme, 1991, p 65 5. Matsuda Y, Inagawa T: Surgical removal of pineal region me-

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ningioma—three case reports. Neurol Med Chir (Tokyo) 35: 594–597, 1995 Matsuno H, Rhoton AL Jr, Peace D: Microsurgical anatomy of the posterior fossa cisterns. Neurosurgery 23:58–80, 1988 Odake G: Meningioma of the falcotentorial region: report of two cases and literature review of occlusion of the galenic system. Neurosurgery 30:788–794, 1992 Okami N, Kawamoto T, Hori T, Takakura K: Surgical treatment of falcotentorial meningioma. J Clin Neurosci 8 (Suppl 1): 15–18, 2001 Poppen JL, Avman N: Aneurysms of the great vein of Galen. J Neurosurg 17:238–244, 1960 Sakaki S, Shiraishi T, Takeda S, Matsuoka K, Sadamoto K: Occlusion of the great vein of Galen associated with a huge meningioma in the pineal region. Case report. J Neurosurg 61: 1136–1140, 1984 Samii M, Carvalho GA, Tatagiba M, Matthies C, Vorkapic P: Meningiomas of the tentorial notch: surgical anatomy and management. J Neurosurg 84:375–381, 1996 Sekhar LN, Goel A: Combined supratentorial and infratentorial approach to large pineal-region meningioma. Surg Neurol 37: 197–201, 1992 Suzuki M, Sobata E, Hatanaka M, Suzuki S, Iwabuchi T, Makiguchi K: Total removal of a falcotentorial junction meningioma by biparietooccipital craniotomy in the sea lion position. A case report. Neurosurgery 15:710–714, 1984 Weir BKA, Allen PBR, Miller JDR: Excision of thrombosed vein of Galen aneurysm in an infant. Case report. J Neurosurg 29: 619–622, 1968 Yas¸argil MG: Microsurgical Anatomy of the Basal Cisterns and Vessels of the Brain, Diagnostic Studies, General Operative Techniques and Pathological Considerations of the Intracranial Aneurysms. Microneurosurgery, Vol 1. Stuttgart: Thieme, 1984, pp 46–47 Ziyal IM, Sekhar LN, Salas E, Olan WJ: Combined supra/infratentorial–transsinus approach to large pineal region tumors. J Neurosurg 88:1050–1057, 1998

Manuscript received May 26, 2005. Accepted in final form September 29, 2005. Address reprint requests to: Kenji Ohata, M.D., 1-4-3 Asahimachi, Abeno-ku, Osaka 545-8586, Japan. email: kohata@med. osaka-cu.ac.jp.

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