Operative approach to mediosuperior cerebellar tumors: occipital interhemispheric transtentorial approach

The Use of the Suboccipital Transtentorial Approach to the Posterior Inferior Incisural Space

Objective To describe our experience with the microsurgical technique of the suboccipital transtentorial (SOTT) approach in the removal of posterior fossa lesions located in the posterior incisural space. Method Between 2002 and 2020 we reviewed all patients who underwent microsurgical resection of lesions of the posterior incisural space at the Department of Neurosurgery, Essex Neuroscience Centre, London, England (eight patients, male to female 3:5, mean age: 51, range 35-69). We describe the preoperative symptoms, radiological findings, surgical techniques, histology and postoperative outcomes in this cohort of patients. Results Eight patients with tumours located in the posterior incisural space underwent surgery during the study period including four meningiomas (50%), two haemangioblastomas (25%), one metastasis (13%) and one giant prolactinoma (13%). Gross or near total resection was achieved in six patients (75%): the giant prolactinoma could not be radically removed and one of the meningiomas required a small fragment to be left in place to protect the Vein of Galen. No patient developed a visual field deficit due to occipital lobe retraction. One patient developed a temporary trochlear nerve palsy (13%). Five patients had mild disability (Glasgow Outcome Scale (GOS) = 5), and four had moderate disability (GOS = 4). Conclusion In our series, the SOTT approach provided excellent access for all cases of tumours in the posterior incisural space. The tumour's size and relationship to the deep venous system contributed to the choice of approach and in one patient who had previously undergone surgery via the supracerebellar route, the SOTT approach enabled the avoidance of gliotic scar tissue. Success is dependent on careful case selection, though from our series of 8 patients, we conclude that this approach allows safe access to the posterior incisural space, with acceptable outcomes with regard to postoperative disability and cranial nerve palsy. As such, the approach should be in the armamentarium of any neurosurgeon who regularly deals with posterior fossa pathology.

Endoscopic Occipital Transtentorial Approach for Supracerebellar Lesions

The occipital transtentorial approach (OTA), which is often applied for superior cerebellar lesions, has an inevitable risk of homonymous hemianopsia due to the retraction of the occipital lobe. The endoscopic approach provides increased visibility of the surgical field due to the wide-angled panoramic view and is minimally invasive in approaching deep brain lesions compared to the conventional microscopic approach. However, little is known regarding endoscopic OTA for the removal of cerebellar lesions. We experienced a case of a hemangioblastoma in the paramedian superior surface of the cerebellum that was successfully treated with endoscopic OTA combined with gravity retraction while avoiding postoperative visual dysfunction. A 48-year-old woman was diagnosed with a hemangioblastoma in the superior surface of the cerebellum. She underwent tumor removal with endoscopic OTA combined with gravity retraction of the occipital lobe instead of using brain retractors. The narrower space was sufficient for surgical manipulation with a panoramic view obtained by endoscopy. The simultaneous observation of the lesion with both an endoscope and a microscope revealed the superiority of infratentorial visualization with an endoscope. Gross total removal was achieved with no postoperative complications, including visual dysfunction. Endoscopic OTA may reduce the risk of postoperative visual dysfunction because of its minimally invasive nature, which is enhanced when combined with gravity retraction. Additionally, the panoramic view of the endoscope allows favorable visualization of an infratentorial lesion, which is otherwise hidden partly by the tentorium. The use of endoscopy is compatible with OTA, and endoscopic OTA could be an option for superior cerebellar lesions for avoiding visual dysfunction.

Occipital Interhemispheric Transtentorial Approach for Tumors of Posterior Third Ventricular Region: Review of Surgical Results

Background

Controversies exist regarding the ideal surgical approach for tumors in posterior third ventricular region (PTV).

Objective

To evaluate the results of occipital interhemispheric transtentorial (OITT) approach for tumors in PTV.

Materials And Methods

Thirty-three patients underwent surgery via OITT approach for PTV tumors at Sri Sathya Sai Institute of Higher Medical Sciences during the study period of 5 years (June 2011-May 2016). Ideal trajectory for OITT approach was determined by neuronavigation. Endoscope was used for removing any residual lesion at the blind spots.

Results

Postoperative magnetic resonance imaging (MRI) performed in all the patients revealed gross total or near-total (>95%) excision of tumor in 31 patients (93.9%). Preoperative neurological deficits improved either completely or significantly following excision of the tumor in 73.3% (11/15) of the patients. Outcome was good (modified Rankin scale ≤2) at discharge in 93.9% (31/33) and at a final follow-up of 3 months or more in 96.8% (30/31) of the patients. None of the patients died during the postoperative period. Complications included upgaze palsy (transient- 6.1% [2/33], persisting- 3% [1/33]), visual field defects (transient- 3% [1/33], persisting- 3% [1/33]), transient third nerve paresis (1/33-3%), transient hemiparesis (1/33-3%), operative site hematoma (1/33-3%), small posterior cerebral artery (PCA) territory infarct (1/33-3%), and small venous infarct (1/33-3%). At least one follow-up MRI could be performed in 23 patients. Final follow-up MRI revealed no recurrence or increase in the size of the residual lesion compared to postoperative images in 20 patients (20/23-87%) and large recurrence in 3 patients (3/23-13%) with high-grade lesions.

Conclusion

Gross total/near-total excision can be performed in majority of the PTV tumors through OITT approach with minimal morbidity and mortality.

Endoscopic high occipital interhemispheric transtentorial approach for lesions in the anterosuperior cerebellum, upper fourth ventricle, and upper dorsal brain stem

BACKGROUND

The occipital transtentorial route is considered the most suitable for surgical treatment of lesions arising from the anterosuperior cerebellum, upper fourth ventricle, and upper dorsal brain stem. Therefore, this study examined the feasibility and effectiveness of the endoscopic high occipital interhemispheric transtentorial approach (EHOTA) for lesions in these areas, in achieving results comparable to the endoscopic OTA (EOTA). EOTA has recently been reported to be an effective procedure for pineal region tumors, having several advantages that include minimal invasiveness with a small entrance limiting the retraction of the occipital lobe, the elimination of blind spots, and the facilitation of fine manipulation due to the bright, magnified panoramic view.

METHODS

By using thirty clinical datasets of venous-phase head CT angiogram, measurements on images were performed and differences between EOTA and EHOTA were identified. In addition, the feasibility of EHOTA was verified with five cadaver heads.

RESULTS

Although the operative field via EHOTA was considered significantly deeper and less maneuverable than with the procedure via EOTA, beneficial angles for manipulation in the superior cerebellum and the fourth ventricle were obtained in EHOTA, on account of their becoming more obtuse. Using EHOTA, it was possible to reach those regions and effectively manipulate all ten sides of the five cadaveric heads, as well as a case with anterosuperior cerebellar cavernous angioma.

CONCLUSIONS

EHOTA, which has the same advantages as EOTA, could prove to be an efficacious procedure for lesions in the anterosuperior cerebellum, upper fourth ventricle, and upper dorsal brain stem.

Selection of surgical approach for cerebellar hemangioblastomas based on venous drainage patterns

Cerebellar hemangioblastomas remain surgically challenging because of the narrow, deep surgical corridors and tumor hypervascularity. Various surgical approaches are used according to the location, but optimal approaches have not been established. We propose a system of surgical approaches based on the venous drainage systems to facilitate surgical planning and achieve acceptable neurological outcomes. Cerebellar hemangioblastomas were divided into five types based on the main drainage systems: suboccipital hemangioblastomas draining to the transverse sinus (TS) or torcula, tentorial hemangioblastomas draining to the tentorial sinus or straight sinus, petrosal hemangioblastomas draining to the superior petrosal sinus (SPS), quadrigeminal hemangioblastomas draining to the galenic system, and tonsillar hemangioblastomas draining to the TS or torcula in conjunction with jugular bulb or SPS. Microsurgical approaches and patient outcome were retrospectively reviewed according to this classification. This study included 17 patients who underwent 21 operations for resection of 19 cerebellar hemangioblastomas, classified into 9 suboccipital, 4 tentorial, 2 petrosal, 2 quadrigeminal, and 2 tonsillar. Standard suboccipital craniotomies were utilized for suboccipital hemangioblastomas, the occipital transtentorial approach (OTA), and supracerebellar infratentorial approach for tentorial hemangioblastomas, the retrosigmoid approach for petrosal hemangioblastomas, OTA for quadrigeminal hemangioblastomas, and midline suboccipital approach for tonsillar hemangioblastomas. Gross total resection was achieved in all patients except one. Two patients with large hemangioblastomas (tonsillar and quadrigeminal) required second-stage operation which finally achieved gross total removal. No single approach had a significantly higher incidence of postoperative neurological deficits. Selection of the optimum surgical approach for cerebellar hemangioblastomas was successful based on the main drainage systems. Understanding of tumor growth and extension with respect to the venous drainage system is critical to select the appropriate surgical approach.

Unilateral Occipital Transtentorial Approach with Multimodal Assistance for Resection of Large Supracerebellar Hemangioblastomas: Preliminary Experience of 2 Cases

BACKGROUND

The surgical resection of large supracerebellar hemangioblastomas (SHBs) is exceptionally challenging due to their vascularity and deep anatomic location and is associated with a high risk of postoperative complications and mortality. Access to the posterior incisural space can be achieved by either an infratentorial supracerebellar approach or occipital transtentorial approach (OTA). However, the optimal surgical strategy has not yet been established. Here, we report 2 cases of large SHBs that were successfully and safely resected via a unilateral OTA with multimodal assistance.

CASE DESCRIPTION

Two patients presented to our hospital with ataxia due to large, solid SHBs. After preoperative embolization, gross total resection of the SHBs was achieved via an OTA. Furthermore, endoscopic assistance was used to resect the remnant portion of the tumor in the second patient. Both patients experienced transient ataxia but were discharged from the hospital without serious complications.

CONCLUSIONS

The combination of an OTA with preoperative embolization and endoscopic assistance may reduce the intraoperative risk and contribute to improved outcome in patients with such clinically challenging tumors.

Hemangioblastomas of the Posterior Cranial Fossa in Adults: Demographics, Clinical, Morphologic, Pathologic, Surgical Features, and Outcomes. A Systematic Review

BACKGROUND

Posterior cranial fossa (PCF) hemangioblastomas are benign, highly vascularized, and well-differentiated tumors with well-described histopathologic features. Although relatively rare, this tumor is the most prevalent primary tumor of the cerebellum in adults.

OBJECTIVE

Because the demographics of patients with such a tumor (as well as the clinical, morphologic, pathologic, surgical features, and outcomes) are not fully understood, we systematized characteristic patient and tumor features.

METHODS

We undertook a systematic review of the English-language literature in PubMed for PCF hemangioblastomas in adults published in the past 31 years. We analyzed geographic distribution and year of publication of articles; demographic data of patients; presenting symptoms and clinical signs; tumor location and morphology; histopathologic features, extent of tumor resection, perioperative blood loss, and postoperative complications; length of hospital stay; and outcomes.

RESULTS

We reviewed 207 articles describing 1759 infratentorial hemangioblastomas in a cohort of 1515 adult patients. We found female predominance in patients with Von Hippel-Lindau disease (VHLD) compared with male predominance in the general patient group. Symptoms of intracranial hypertension were more common in the VHLD group compared with the general group of patients. The cerebellar location was more common in the VHLD group and solid (parenchymatous) tumor was the most common type. Most patients underwent total resection but rate of resection did not differ between the general and VHLD groups. Most patients had a favorable outcome.

CONCLUSIONS

The literature of adult PCF hemangioblastomas is limited and general surgical experience with such tumors is scarce because of their rarity. Rates of postoperative complications and mortality remain higher than expected. However, prognosis and surgical outcomes are generally favorable. Nevertheless, surgery of adult PCF hemangioblastomas is a demanding and challenging task.

The superior transvelar approach to the fourth ventricle and brainstem

Objective The superior transvelar approach is used to access pathologies located in the fourth ventricle and brainstem. The surgical path is below the venous structures, through the superior medullary velum. Following splitting the tentorial edge, near the tentorial apex, the superior medullary velum is split in the cerebello-mesencephalic fissure. Using the supracerebellar infratentorial, transtentorial or parietal interhemispheric routes, the superior medullary velum is approached. Splitting this velum provides a detailed view of the fourth ventricle and its floor. Materials and Methods A total of 10 formalin-fixed specimens were dissected in a stepwise manner to simulate the superior transvelar approach to the fourth ventricle. The exposure gained the distance from the craniotomy site and the ease of access was assessed for each of the routes. We also present an illustrative case, operated by the senior author (AN). Results The superior transvelar approach provides access to the entire length of the fourth ventricle floor, from the aqueduct to the obex, when using the parietal interhemispheric route. In addition, this approach provides access to the entire width of the floor of the fourth ventricle; however, this requires retracting the superior cerebellar peduncle. Using the supracerebellar infratentorial route gives a limited exposure of the superior part of the fourth ventricle. The occipital interhemispheric route is a compromise between these two. Conclusion The superior transvelar approach to the fourth ventricle provides a route for approaching the fourth ventricle from above. This approach does not require opening the posterior fossa in the traditional way, and provides a reasonable alternative for accessing the superior fourth ventricle.

Tumors of the superior medullary velum in infancy and childhood: report of 6 cases

OBJECT

The superior medullary velum (SMV) is a thin lamina of white matter located between the superior cerebellar peduncles horizontally and between the midbrain and cerebellum vertically. The SMV has not previously been described as the primary location of a posterior fossa tumor, although it can be secondarily invaded by a tumor from the cerebellum or quadrigeminal plate. This paper aims to define clinical and radiological features of tumors primarily arising from the SMV during childhood.

METHODS

The authors observed 6 infants and children harboring neoplasms of the SMV who were treated at Ann & Robert Lurie Children's Hospital of Chicago (formerly Children's Memorial Hospital) in Chicago, Illinois. Pathological diagnosis of the neoplasms was an atypical teratoid/rhabdoid tumor (ATRT) in 5 patients, and a juvenile pilocytic astrocytoma (JPA) in the remaining child. The tumors were diagnosed during infancy in all patients, with ages ranging from 3 months to 10 months, except for the patient with a JPA (diagnosed at 5 years old). All patients presented with signs and symptoms of increased intracranial pressure due to obstructive hydrocephalus.

RESULTS

Characteristic MRI features were noted, consistent with a mass in both the fourth ventricle and the cerebellomesencephalic fissure and quadrigeminal cistern, resulting in the circumferential displacement of the neural structures surrounding the SMV. The tumor was removed effectively in gross-total fashion through the occipital transtentorial approach in all patients. This approach offers a wide exposure of the region. However, all infants with ATRT suffered tumor dissemination and died between 4 and 11 months after diagnosis, in spite of radical resection and oncological treatment. The 1 child with JPA is alive and well 30 months after tumor resection.

CONCLUSIONS

To the best of the authors' knowledge, this is the first description in the literature that focuses on tumors originating from the SMV. This entity must be promptly recognized on preoperative radiological studies to carefully plan the subsequent surgical and clinical management.

Clinical features and pathophysiological mechanism of the hemianoptic complication after the occipital transtentorial approach

OBJECTIVE

To obtain detailed insight into neuro-ophthalmological characteristics and pathophysiology of hemianoptic complications after occipital transtentorial surgery.

METHODS

We reviewed the cases of 14 patients surgically treated by the occipital transtentorial approach. Treated lesions included 6 posterior third ventricle tumors, including pineal and tectal lesions, 3 falco-tentorial meningiomas, and 5 superior cerebellar lesions. The surgeries were performed by the unilateral occipital transtentorial approach with patients in the prone position.

RESULTS

Visual functions were preoperatively normal in all patients. After surgery, 11 patients (79%) showed hemianoptic complications detected by a confrontation test in the immediate postoperative period. The condition began to improve in the early postoperative days. The visual field recovered completely in 6 patients within 10 days, 2 patients recovered within 3 months, and 3 patients complained of permanent visual field defects. Optometric neuro-ophthalmic evaluation in the early postoperative period failed to detect complete homonymous hemianopsia, but homonymous inferior quadrantanopia and scotomatous defects were observed in 6 patients. These visual field defects were permanent in 3 patients. Postoperative MRI showed no morphological abnormality except these three patients. Atrophic change of the occipital lobe with preservation of striate cortex was associated with persistent visual field defects in two patients. Cerebral blood flow evaluation by single photon emission computed tomography suggested that temporary local hyperperfusion of the retracted occipital region when visual field defect was present.

CONCLUSION

Hemianoptic visual field defects can recover via inferior quadrantanopia or scotomatous defect. All of these defects are attributable to injury to the optic radiation as well to the occipital lobe. Hyperperfusion of the retracted occipital region may underlie the pathophysiology of hemianoptic complications after the occipital transtentorial approach.

Posterior cranial fossa tumors: Results and prognostic factors in a consecutive series of 14 operated patients by occipital transtentorial approach

BACKGROUND

The objective of our study was to determine the safety and usefulness of performing surgery via occipital transtentorial approach to treat posterior cranial fossa tumors, which is well known as an approach to the pineal region (Poppen's approach).

METHODS

Fourteen patients with posterior cranial fossa tumors were successfully treated using occipital transtentorial approach between 2007 and 2012. The lesions included five meningiomas, three astrocytomas, two metastases, two hemangioblastomas, one cavernoma, and one dysgerminoma.

RESULTS

Lesions were <3 cm in 12 cases and ≥3 cm in two cases. Average Karnofsky Performance Status (KPS) scoring at admission was 88.5. Eleven patients scored ≥70 and seven patients <70. Average age was 43.1 years. All patients underwent surgical treatment by the same surgical team. All tumors were completely removed surgically without any injury to the venous complex and the adjoining structures. There was no incidence of mortality or morbidity in all patients, and all functional outcomes were good to excellent postoperatively. Postoperative computed tomography (CT) imaging revealed that none of the patients had suffered brain damage or infarction around the cerebellum, brainstem, or occipital lobe.

CONCLUSIONS

We found that the use of occipital transtentorial approach is strongly supported by the successful removal of posterior cranial fossa tumors without serious complications. Open microneurosurgery is probably still the most effective therapy in improving survival and KPS in patients with posterior cranial fossa tumors, given that the proper surgical technique is used and complications do not occur. This case study has strongly suggested that this approach is very useful, safe, and accurate for removing the tumors of posterior fossa and evaluating the surrounding anatomy, as well as for determining operative strategy.

Posterior interhemispheric retrocallosal approach to pineal region and posterior fossa lesions in a pediatric population

OBJECT

The purpose of this study was to evaluate the posterior interhemispheric retrocallosal approach (PIRA) for its safety and efficacy in the resection of pineal region and posterior fossa lesions in children.

METHODS

Twenty-nine PIRAs were performed in 26 children between March 1997 and March 2009, and these cases were retrospectively reviewed. There were 15 girls and 11 boys in the series. The median age at the time of surgery was 7 years (range 7 months-17 years). Twenty-seven cases were treated for tumor, 1 for loculated hydrocephalus, and 1 for an aneurysm.

RESULTS

Of the 27 cases treated for tumor, there were 20 (74%) gross-total resections, 5 (19%) subtotal resections, and 2 (7%) biopsies. One bridging vein was sacrificed in 6 cases and 2 bridging veins were divided in 1 case, whereas in 3 cases there was sacrifice of a single deep cerebral vein. No patient developed radiographic evidence of venous infarction. Approach-related complications were low, and included 2 cases of transient homonymous hemianopia. There were no surgery-related deaths.

CONCLUSIONS

This approach allows for ample access to pineal region and posterior fossa lesions, with low postoperative morbidity.

OCCIPITAL TRANSTENTORIAL APPROACH TO THE PRECENTRAL CEREBELLAR FISSURE AND POSTERIOR INCISURAL SPACE

OBJECTIVE

To describe the surgical techniques and postoperative clinical outcomes with the occipital transtentorial (OT) approach in patients harboring lesions arising from the precentral cerebellar fissure, posterior incisural space, and adjoining structures.

METHODS

Twenty-two patients underwent microsurgical resection of intra-axial lesions arising within the precentral cerebellar fissure and posterior incisural space between 1997 and 2006. Patient demographics, presenting symptoms, pathology, and neurological outcomes were retrospectively reviewed. Pre- and postoperative magnetic resonance imaging scans were evaluated to determine the anatomic extensions of the lesion and the degree of surgical resection. Patients with lesions primarily confined to the pineal and posterior third ventricle approached by a supracerebellar infratentorial trajectory were excluded from this study.

RESULTS

Of the 22 patients reported in this series, 17 (77%) had contrast-enhancing lesions, and 5 (23%) had nonenhancing lesions arising from the precentral cerebellar fissure and posterior incisural space. The lesions were oriented dorsomedial to the midbrain and diencephalon in 6 patients (27%), dorsolateral in 14 patients (64%), and lateral in 2 patients (9%). A lateral OT approach directed under the occipitotemporal junction was used in 16 patients (73%), and an interhemispheric OT approach was used in 6 patients (27%). Transient visual field loss occurred in 3 patients (14%); it resolved by the third follow-up month. Gross total resection or near-total resection of the imaging-defined lesion volume was achieved in 19 patients (86%).

CONCLUSION

The OT approaches provide excellent exposure for lesions of the precentral cerebellar fissure, posterior incisural space, and adjacent structures. The lateral OT approach directed under the occipitotemporal junction provides an inline view for lesions situated posterolateral to the brainstem. It also provides an inferiorly directed view under the venous system into the precentral cerebellar fissure and fourth ventricular roof. Visual field deficits are minimized by directing the trajectory under the occipitotemporal junction instead of retracting along the interhemispheric corridor. The interhemispheric OT approach was primarily used for lesions extending superiorly, in the midline or near midline, above the tentorium and venous system into the splenium of corpus callosum, lateral ventricle, and posterior thalamus, where extensive lateral retraction was not required.

Surgical management of cerebellar hemangioblastomas in patients with von Hippel–Lindau disease

Object

Despite the frequency of cerebellar hemangioblastomas in von Hippel–Lindau (VHL) disease, their optimum contemporary management has not been defined, and is made complex because of the multiple, progressive, and protean nature of the tumors found in patients with this disorder. To examine modern management and outcomes of cerebellar hemangioblastomas in VHL disease, the authors reviewed findings in patients with this disease who underwent resection of cerebellar hemangioblastomas.

Methods

Consecutive patients with VHL disease who underwent surgery for cerebellar hemangioblastoma(s) at the National Institutes of Health were included. Eighty consecutive patients (44 female and 36 male patients) underwent 126 operations for removal of 164 cerebellar hemangioblastomas (age at surgery 37.8 ± 10.3 years, follow-up duration 96.0 ± 60.3 months). Serial clinical examinations, imaging studies, and operative records were analyzed.

Results

Symptoms and signs included headache (94 operations; 75%), ataxia (55%), dysmetria (29%), and hydrocephalus (28%). Although the primary objective of surgery was resection of the hemangioblastoma considered responsible for symptoms (136 of the hemangioblastomas [83%]), 28 additional hemangioblastomas (17%) were removed during the same surgeries. Tumors associated with symptoms were larger (diameter 1.8 ± 1.9 cm; volume 2.8 ± 3.4 cm3; p < 0.05) and more likely to be associated with peritumoral edema or peritumoral cysts (100% associated with edema and/or cyst; p < 0.05) than asymptomatic tumors (diameter 1.1 ± 0.9 cm; volume 0.7 ± 0.4 cm3; 18%). More tumors were located in the posterior (74%) compared with the anterior (26%) half of the cerebellum (p < 0.05). Three months after resection, symptom improvement/stabilization had occurred following 124 of the operations (98%). Preoperative hydrocephalus resolved after tumor removal in 33 cases (94%) and did not require cerebrospinal fluid diversion. Long-term imaging follow-up (61.5 ± 15.0 months) revealed no recurrences.

Conclusions

Symptoms and signs caused by cerebellar hemangioblastomas in VHL disease are associated with edema and peritumoral cyst formation/propagation and are treated safely and effectively with resection. Cerebrospinal fluid diversion is rarely necessary after complete tumor removal in patients with preoperative hydrocephalus. Cerebellar hemangioblastomas are preferentially distributed in the posterior half of the cerebellum, as they are in the brainstem and spinal cord. Tumor recurrence is avoided by meticulous extracapsular resection.

Posterior subtemporal transtentorial approach to intraparenchymal lesions of the anteromedial region of the superior cerebellum

Object. To overcome the limitations associated with surgical approaches that have been described for accessing intraparenchymal lesions of the anteromedial region of the superior cerebellum, the authors used a posterior subtemporal transtentorial approach to remove tumors in this region. In this paper they describe the surgical technique that they used as well as the operative findings and clinical outcomes observed in patients who underwent resection of tumors in the anteromedial superior cerebellum.

Methods. The consecutive patients with anteromedial superior cerebellar tumors who underwent resection performed using the posterior subtemporal transtentorial approach at the National Institutes of Health were included in this study. Clinical, neuroimaging, and operative results were analyzed.

Three patients (two men and one woman) with anteromedial superior cerebellar tumors (two hemangioblastomas and one pilocytic astrocytoma) underwent resection via this approach. All the tumors were larger than 3 cm in diameter (range 3.1–3.5 cm). This approach provided excellent surgical access and permitted complete tumor resection in each case. The patients remained neurologically unchanged compared with preoperative baseline findings at the last follow-up examination (conducted at 4, 18, and 42 months postoperatively). One patient displayed a mild transient confusion immediately after surgery, but it resolved within 6 days.

Conclusions. The posterior subtemporal transtentorial approach provides excellent access to the anteromedial superior cerebellar region. This approach permits resection of large lesions in this location, while avoiding many of the limitations associated with other approaches to this site.

Three-dimensional Computed Tomography Angiography of the Galenic System for the Occipital Transtentorial Approach

The venous variations of the galenic system were evaluated using three-dimensional computed tomography angiography (3D-CTA) to assess the influence on the occipital transtentorial approach in 150 patients who underwent 3D-CTA as a routine screening examination for cerebrovascular diseases. The variations of the vein of Galen with its tributaries, the tentorial sinus, and the veins around the tentorium were evaluated in multiple intensity projections and stereoscopic images. The angle between the vein of Galen and the straight sinus was 67.1 +/- 31.9 degrees (mean +/- SD). Observation of the pineal body from the direction of the approach tended to extend to the quadrigeminal bodies in acute angle cases, and to the third ventricle in obtuse angle cases. Bilateral internal cerebral veins (ICVs) joined in the anterior portion were associated with a long vein of Galen, or in the posterior portion with a short vein of Galen. The distance between the bilateral ICVs was 4.66 +/- 2.28 mm (mean +/- SD), and the shape of the space could be classified as spindle, parallel, hairpin, and round types. The basal vein could be classified into well-developed, hypoplastic, hardly recognized, and mimicking two basal veins because the tributary did not join but ran parallel to the basal vein. The drainage pathways lead to the anterior or posterior portion of the vein of Galen, the ICV, the tentorial sinus, and the superior petrosal sinus. The various types of the tentorial sinus and primitive tentorial sinus which might be sacrificed during section of the tentorium were confirmed. The inferior cerebral vein draining to the tentorial sinus could be seen. 3D-CTA could also demonstrate the presence, the course, and the drainage points of the internal occipital vein, the precentral cerebellar vein, the posterior pericallosal vein, and so on. 3D-CTA is useful to evaluate the variations of the venous system and the relationship with the tumor, and for preoperative simulation and intraoperative navigation of the occipital transtentorial approach.

Surgical treatment of posterior fossa tumors via the occipital transtentorial approach: evaluation of operative safety and results in 14 patients with anterosuperior cerebellar tumors

OBJECT

To determine the safety and usefulness of performing surgery via the occipital transtentorial approach to treat anterosuperior cerebellar tumors, evaluation of 14 patients was performed over a 5-year period.

METHODS

The study was performed in 14 patients, aged 6 months to 71 years, who harbored anterosuperior cerebellar tumors of the posterior fossa including four hemangioblastomas, three cerebellar astrocytomas, three medulloblastomas, two metastatic tumors, one recurrent astrocytoma, and one rhabdoid cell tumor. All patients underwent surgical treatment by the same surgical team and via the same surgical approach. Endoscopy combined with neuronavigation was used for large, deep-seated tumors extending to the fourth ventricle. Of the 14 patients, total or gross-total removal was achieved in 12 patients and subtotal removal in two patients. There was no incidence of mortality or morbidity in the 14 patients, and all functional outcomes were good to excellent postoperatively. Postoperative magnetic resonance imaging revealed that none of the patients had suffered brain damage or infarction around the cerebellum, brainstem, or occipital lobe.

CONCLUSIONS

Although this study was the first in which a specific examination of the efficacy of the occipital transtentorial approach in patients with anterosuperior cerebellar tumors was undertaken, our findings suggest that this surgical approach is very useful, safe, and accurate for removing the primary tumor and evaluating the surrounding anatomy, as well as for determining operative strategy.