Dural-based large B-cell lymphoma masquerading as a tentorial meningioma.

A 53-year-old woman presented with a 2-week history of headache and vertigo. Computed tomography revealed a hyperdense tumor, measuring 30 × 31 × 36 mm in diameter, in the anteromedial parts of the cerebellar hemispheres. Cerebral magnetic resonance imaging 10 days later revealed an apparent extra-axial tumor with broad attachment to the medial tentorium cerebelli and rapid growth to a diameter of 40 × 41 × 46 mm. Cerebral angiography revealed no obvious feeding vessels or tumor stains. The patient underwent biopsy through the left occipital transtentorial route. The histological appearance was consistent with diffuse large B-cell lymphoma. Intracranial lymphoma may present as a dural tumor that mimics a meningioma. Rapid tumor growth incongruous with benign meningiomas should be assumed to be possible lymphoma, and prompt biopsy should be performed.

Simulation of the occipital transtentorial approach incorporating visualization of the cerebellar tentorium using three-dimensional computed tomography angiography and gadolinium-enhanced T1-weighted magnetic resonance imaging: technical note.

The occipital transtentorial approach (OTA) is one of the useful approaches to the lesions of the pineal region, dorsal brainstem, and supracerebellar region. However, a wide operative field is sometimes difficult to obtain due to the tentorial sinus and bridging veins. This study evaluated the usefulness of preoperative simulation of OTA, specifically including the cerebellar tentorium in 9 patients. All patients underwent computed tomography angiography and venography and gadolinium-enhanced three-dimensional T1-weighted magnetic resonance images (Gd-3D-T1WI). The images were fused, and the cerebellar tentorium, vessels, and tumor were manually extracted from Gd-3D-T1WI to obtain the simulation images. Visualization of the cerebellar tentorium could discriminate between bridging veins from the occipital lobe and cerebellum, and recognize the site of bridging to the tentorial sinus and variants which may interfere with the tentorial incision. Simulation of the tentorial incision was also possible based on the relationships between the tumor, tentorial sinus, bridging vein, and cerebellar tentorium. The simulation suggested that safe tentorial incision was difficult in two sides because of the crossed tentorial sinus draining the left basal vein and draining veins from the glioblastoma. The OTA was performed in eight cases, and no difficulty was experienced in the tentorial incision in all cases. The simulation findings of the bridging vein and tentorial sinus were consistent with the intraoperative findings. Preoperative simulation including the cerebellar tentorium is useful for determining the optimum and safe side and required extent of the tentorial incision necessary for tumor resection with the OTA.

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.

Outcomes and surgical approaches for pineal region tumors in children: 30 years' experience.

OBJECTIVE: Pineal region tumors account for 2.7%-11% of all CNS tumors in children. In this series, the authors present their surgical results and long-term outcomes from a pediatric pineal region tumor cohort. METHODS: A total of 151 children aged 0-18 years were treated from 1991 to 2020. Tumor markers were collected in all patients; if positive, chemotherapy was performed, and if negative, biopsy was performed, preferably endoscopically. Resection was performed when there was a residual germ cell tumor (GCT) lesion after chemotherapy. RESULTS: The distribution based on histological type, as verified by markers, biopsy, or surgery, was germinoma (33.1%), nongerminomatous GCT (NGGCT) (27.2%), pineoblastoma (22.5%), glioma (12.6%), and embryonal tumor (atypical teratoid rhabdoid tumor) (3.3%). A total of 97 patients underwent resection, and gross-total resection (GTR) was achieved in 64%; the highest GTR rate (76.6%) was found in patients with GCTs, and the lowest (30.8%) was found in those with gliomas. The supracerebellar infratentorial approach (SCITA) was the most common, performed in 53.6% of patients, followed by the occipital transtentorial approach (OTA), performed in 24.7% of patients. Lesions were biopsied in 70 patients, and the diagnostic accuracy was 91.4. The overall survival (OS) rates at 12, 24, and 60 months as stratified by histological type were 93.7%, 93.7%, and 88% for patients with germinomas; 84.5%, 63.5%, and 40.7% for patients with pineoblastomas; 89.4%, 80.8%, and 67.2% for patients with NGGCTs; 89.4%, 78.2%, and 72.6% for patients with gliomas; and 40%, 20%, and 0% for patients with embryonal tumors, respectively (p < 0001). The OS at 60 months was significantly higher in the group with GTR (69.7%) than in the group with subtotal resection (40.8%) (p = 0.04). The 5-year progression-free survival was 77% for patients with germinomas, 72.6% for patients with gliomas, 50.8% for patients with NGGCTs, and 38.9% for patients with pineoblastomas. CONCLUSIONS: The efficacy of resection varies by histological type, and complete resection is associated with higher OS rates. Endoscopic biopsy is the method of choice for patients presenting with negative tumor markers and hydrocephalus. For tumors restricted to the midline and with extension to the third ventricle, a SCITA is preferred, whereas for lesions with extension toward the fourth ventricle, an OTA is preferred.

Fully endoscopic occipital transtentorial approach for pineal region tumors.

PURPOSE: Aggressive surgical resection for pineal region tumors, which is a mainstay of management in almost all cases, remains technically challenging because these tumors are located at the geometric center of the brain and surrounded by critical neurovascular structures. Therefore, any refinement in the surgical procedure is desirable. We have recently introduced an endoscope to the occipital transtentorial approach (OTA), which has been one of the most common procedures for reaching the pineal region, to overcome some of the disadvantages of the procedure, including the necessity of a relatively large skin incision and bone opening, the difficulty in orientation due to the obliqueness of the approach, the possibility of retraction injury on the occipital lobe and the corpus callosum, and blind spots at the ipsilateral wall and the roof of the third ventricle. METHODS: We performed endoscopic OTA with corresponding advantages, including less invasiveness by virtue of a small entrance limiting the retraction of the occipital lobe, the elimination of blind spots, and the facilitation of fine manipulation based on the bright endoscopic view even at substantial depth, which is panoramic and can be magnified as needed. This procedure was substantially different from a conventional microscopic OTA, though both use a similar corridor. To maximize maneuverability within the limited space in endoscopic OTA, it was necessary to thoroughly understand each step of the procedure, as well as optimal sequence in the procedure. RESULTS AND CONCLUSION: We found endoscopic OTA to be a promising technique for resectioning pineal region tumors, with the potential for extensive and routine application for surgeons familiar with endoscopic surgery.

Indocyanine green illuminates the way to cut the tentorium in occipital transtentorial approach: technical note.

BACKGROUND AND IMPORTANCE: The occipital transtentorial approach is used to address lesions at the posterior incisural space or upper cerebellum. This approach is rarely used, making standardization of the surgical procedure challenging. Here we describe the effectiveness of indocyanine green (ICG) and dye markings before tentorial incision in charting a safe and bloodless surgical trajectory for improved manoeuvrability. CLINICAL PRESENTATION: The first case was a 40-year-old man with a residual pineal mass after chemoradiation therapy for pathologically-proven germinoma. Surgical resection was performed via left occipital craniotomy. Incision of the left cerebellar tentorium by a radiofrequency knife was preceded by visualization of the straight sinus and venous lake, which were marked with dye, enabling safe entry into the quadrigeminal cistern. Finally, total-resection of the mature teratoma was achieved. The second case was a 50-year-old man with an enhancing mass at the cerebellar vermis and left hemisphere. Left occipital craniotomy was followed by ICG administration, illuminating the straight sinus and a complex structure of dural venous channels, which were marked with dye. This visualization maximized the tentorial incision by carefully avoiding venous structures and widely exposed the upper cerebellum. Subtotal-resection of the tumor was achieved, with a diagnosis of glioblastoma. CONCLUSION: ICG administration and dye marking are feasible and useful methods for precise identification/visualization of venous structures. They enable maximization as well as safe and appropriate tentorial incision to provide a sufficient surgical corridor for the occipital transtentorial approach.

Suboccipital trans-horizontal fissure approach for cerebellar hemorrhage with rupture into the upper fourth and third ventricles: the first clinical experience. Illustrative cases.

BACKGROUND: The authors' previous cadaveric study reported a new surgical approach that can expose the deep cerebellar hemisphere, cerebellopontine angle, and upper fourth ventricle through dissection of the horizontal fissure of the suboccipital cerebellar hemisphere. Here, the authors present their experience with the first clinical use of the suboccipital trans-horizontal fissure (SOTHF) approach requiring access to the third and upper fourth ventricle lesions, a challenging compartment to access by traditional approaches. OBSERVATIONS: In cases 1 and 2, computed tomography demonstrated large hematomas in the left cerebellar hemisphere with extension into the third ventricle and/or the upper fourth ventricle, resulting in obstructive hydrocephalus. Large hematomas in both the cerebellar hemisphere and the upper fourth ventricle were successfully removed via an SOTHF approach alone without external ventricular drainage. Furthermore, the hematoma in the third ventricle was removed through the aqueduct in case 2. Access to the upper fourth ventricle and the third ventricle were intraoperatively verified using a neuronavigation system. The patients immediately regained consciousness, and the result of cerebellar function testing was almost normal after the operation. LESSONS: An SOTHF approach can achieve the removal of cerebellar and intraventricular hematomas simultaneously, is a faster and potentially safer method than others, and subsequently allows rapid clinical improvement.

Primary midbrain germinoma relapse-free for 5 years: A case report.

Background: The biology and clinical course of intracranial germinomas differ as per their location of occurrence. Germinoma of the primary midbrain is particularly rare, and its clinical features, treatment strategies, and long-term prognosis remain uncertain. Case Description: A 39-year-old man who had been diagnosed with midbrain germinoma by open biopsy through the occipital transtentorial approach had undergone chemoradiotherapy and achieved 5 years with no recurrence. Conclusion: Germinomas should be considered as a differential diagnosis for adolescents and young adult men with mesencephalic tumors, and reliable sampling followed by chemoradiotherapy must be performed.

Microsurgical approaches to the cerebellar interpeduncular region: qualitative and quantitative analysis.

OBJECTIVE: The cerebellar interpeduncular region (CIPR) is a gate for dorsolateral pontine and cerebellar lesions accessed through the supracerebellar infratentorial approach (SCITa), the occipital transtentorial approach (OTa), or the subtemporal transtentorial approach (STa). The authors sought to compare the exposures of the CIPR region that each of these approaches provided. METHODS: Three approaches were performed bilaterally in eight silicone-injected cadaveric heads. The working area, area of exposure, depth of the surgical corridor, length of the interpeduncular sulcus (IPS) exposed, and bridging veins were statistically studied and compared based on each approach. RESULTS: The OTa provided the largest working area (1421 mm2; p < 0.0001) and the longest surgical corridor (6.75 cm; p = 0.0006). Compared with the SCITa, the STa provided a larger exposure area (249.3 mm2; p = 0.0148) and exposed more of the length of the IPS (1.15 cm; p = 0.0484). The most bridging veins were encountered with the SCITa; however, no significant differences were found between this approach and the other approaches (p > 0.05). CONCLUSIONS: To reach the CIPR, the STa provided a more extensive exposure area and more linear exposure than did the SCITa. The OTa offered a larger working area than the SCIT and the STa; however, the OTa had the most extensive surgical corridor. These data may help neurosurgeons select the most appropriate approach for lesions of the CIPR.

Acute surgery for a case of superior vermian arteriovenous malformation producing raised venous pressure coexisting with basilar-superior cerebellar artery aneurysm presenting subarachnoid hemorrhage; Case report.

BACKGROUND: Superior vermian subtype of arteriovenous malformation (AVM) coexisting with proximal feeder aneurysm on basilar-superior cerebellar artery (BA-SCA) junction is an extremely rare situation. We experienced a case of this rare entity presenting with subarachnoid hemorrhage (SAH), and herein, introduce the outline and clinical features of this experience together with the actual surgical video. CASE DESCRIPTION: A 54-year-old man SAH patient with severe headache, disturbance of consciousness, and left oculomotor palsy was urgently admitted to our hospital. Imaging examination demonstrated superior vermian AVM with BA-SCA aneurysm, and both lesions were treated through two different approaches (left pterional craniotomy in conjunction with zygomectomy, and left posterior interhemispheric occipital transtentorial approach) in acute phase of SAH. Both lesions were completely disappeared postoperatively and the patient's postoperative course was favorable, without symptomatic cerebral vasospasm. Although slight oculomotor palsy remained, the patient recovered well and was transferred to a rehabilitation hospital for further improvement. CONCLUSION: In the cases of AVM coexisting with proximal feeder aneurysm, presenting with SAH, disorders of intracranial venous return associated with an AVM can be a vital hindrance to managing cerebral vasospasm; therefore, treating both lesions in the acute phase may lead to good outcomes.

Gravity Assisted Retraction Less Occipito Transtentorial and Trans-Splenial Approach for Posterior Third Ventricular Dermoid.

BACKGROUND AND INTRODUCTION: A dermoid is an inclusion cyst. Its presence in the posterior third ventricle is highly infrequent. It usually compresses rather than infiltrates the posterior third ventricle's anatomical structures due to a well-defined capsule. Hence, the surgical anatomy in these tumors is less distorted. The approach to the posterior third ventricular tumors depends upon their relation to the galenic venous complex. OBJECTIVE: This video abstract presents a case of the posterior third ventricular dermoid operated by gravity-assisted retraction less occipito transtentorial combined with the trans-splenial approach. SURGICAL TECHNIQUE: A 36-year-old gentleman presented with a headache without any neurological deficits; the magnetic resonance imaging (MRI) revealed a well-defined heterogeneous lesion in the posterior third ventricular region. It was mainly toward the right side, just beneath the splenium, pushing the galenic venous system downward. This made the occipital transtentorial approach favorable as it required the least vessel handling. A right parieto-occipital craniotomy was performed. The patient was placed in a lateral semi-prone position with the head slightly rotated toward the right side with a slight neck extension. This allowed the right occipital lobe to fall away from the Falco-tentorial junction. With sharp dissection, an inter-Rosenthal corridor was made. But as the tumor was higher up in the posterior third ventricle, it was modified to another trans-splenial corridor. Near-total excision was achieved with a thin capsule left attached to the vein of Galen. The capsule was thick, filled with a cheesy white material, and a calcified sebaceous lump within. The postoperative scan showed no residual tumor. RESULTS: The patient had improvement in the headache. There were no field cuts. The histopathology was suggestive of a dermoid cyst. CONCLUSIONS: Dermoid cysts of the posterior third ventricular region are rare, and judicious surgical decisions result in better outcomes.

Removal of pineal region teratomas using occipital transtentorial approach (OTA) technique: Case report and literature review.

INTRODUCTION: The development of improved micro-surgery techniques and neuroanesthesia has become increasingly sophisticated makes open-microsurgery tumor resection a choice for the management of the pineal region. CASE PRESENTATION: An 11-year-old male with a pineal body tumor post ventriculo-peritoneal (VP) shunt, underwent tumor resection. Patients complain of headaches, relieve with medication but often recurrent, and often experience a decrease in consciousness. One month before the procedure, the patient experienced blurred vision, staggering, nausea, vomiting, and decrease of consciousness. The operation is performed with an occipital transtentorial approach (OTA) technique. During surgery, hemodynamics was relatively stable. Postoperatively, the patient underwent controlled ventilation in the intensive care room, and recover significantly within one week. DISCUSSION: Various surgical approaches have been proposed for pineal region tumors. We review the available literature (PubMed) with 11 reported cases of pineal tumor therapy with the occipital transtentorial approach and evaluate general symptoms in clinical manifestations, histopathological features, radiological findings, and survival times to demonstrate therapeutic effectiveness. Several cases of the pineal tumor were also reported using tumor extraction by occipital transtentorial approach. CONCLUSION: The choice of approach is influenced by the location of the tumor, pathology findings, the neurosurgeon's comfort and consideration of the risk of complications.

Exclusive Endoscopic Occipital Transtentorial Approach for Pineal Region Tumors.

OBJECTIVE: Removal of pineal region tumors, which are deeply placed and encircled by intricate neurovascular structures, is challenging to neurosurgeons. The aim of this study was to present our experience with the exclusive endoscopic occipital transtentorial approach (EEOTA) used for removal of pineal region tumors. METHODS: A retrospective review was performed of patients who underwent surgery using the EEOTA to remove pineal region tumors from May 2016 to August 2018. The details of the EEOTA procedure were confirmed. RESULTS: Five patients underwent surgery via the EEOTA for treatment of pineal region tumors. In all cases, it was possible to perform the EEOTA less invasively through a keyhole craniotomy approximately 2.0-2.5 cm in size. The EEOTA produced an excellent view and provided natural and automatic orientation. There was essentially no blind spot in this procedure, even for the floor or ipsilateral wall of the third ventricle. Gross total resection was achieved in 4 cases. In the patient with atypical teratoid rhabdoid tumor, we abandoned gross total resection because of a hardened adhesion to the tectum and the great cerebral vein and its tributaries. Two patients presented with transient upper gaze palsy immediately after surgery but experienced complete recovery during the follow-up period. CONCLUSIONS: The EEOTA is a very promising technique for removal of pineal region tumors and has the potential for extensive and routine application for surgeons familiar with endoscopic surgery.

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.

Posterior Cerebral Artery Reconstruction by In-Situ Bypass with Superior Cerebellar Artery via Occipital Transtentorial Approach.

BACKGROUND: Posterior cerebral artery (PCA) aneurysms are relatively rare, and neck clipping is often difficult due to their fusiform shape. We report a case of a thrombosed aneurysm of the distal PCA for which curative trapping and parent artery reconstruction by in situ bypass were performed through an occipital transtentorial approach (OTA). CASE DESCRIPTION: A 67-year-old woman had been suffering from numbness in the right face and limbs for 4 months. Radiologic imaging demonstrated a thrombosed aneurysm on a distal portion of the left PCA. Curative trapping of the aneurysm and in-situ bypass between the distal PCA and superior cerebellar artery were performed through the OTA. Before surgery, we had evaluated access to the PCA and feasibility of the bypass in a cadaveric simulation. The PCA was well exposed in the posterior half of the ambient cistern, and the proximity of the distal PCA to the superior cerebellar artery through a tentorial incision was confirmed. CONCLUSIONS: This OTA could represent a useful option for definitive treatment of distal PCA aneurysms.

Meningiomas Originated at the Falcotentorial Region: Analysis of Topographic and Diagnostic Features Guiding an Optimal Surgical Planning.

BACKGROUND: Meningiomas arising at the pineal region are a rare entity and still represent a great neurosurgical challenge given their deep location and critical neuroanatomic relationships. The optimal surgical approach to treat these lesions is still under debate. Our objective is to review the topographic and diagnostic features of these lesions, which can help to guide an optimal surgical outcome. METHODS: We present 2 clinical cases of falcotentorial meningiomas successfully treated at our institution (2016-2017) with different surgical approaches. A literature review is performed, and a description of the classification, anatomic relationships, clinical features, diagnosis, and different surgical options and outcomes of these lesions is presented. RESULTS: The first patient was treated via a supracerebellar infratentorial approach, and the second patient was treated via a parieto-occipital interhemispheric approach. In both tumors, a gross total resection was achieved with no permanent neurologic deficits. In the literature review, gross total resection rates range from 33% to 100%, with no differences regarding the type of meningioma or the surgical approach performed. Permanent neurologic morbidity varies from 0% to 50%, and mortality rates range from 0% to 23%. The distortion and displacement of the vein of Galen and straight sinus represent the most important feature in the decision of optimal surgical approach. CONCLUSIONS: Pineal region meningiomas represent very infrequent, challenging lesions, and their description in the literature is scarce. The systematic topographic classification of these tumors and evaluation of the neuroanatomic structures involved are crucial to guide a safe and optimal surgical approach and achieve satisfactory outcomes.

Multistaged, multidirectional strategy for safe removal of large meningiomas in the pineal region.

OBJECTIVE Pineal region meningiomas are rare and tend to be discovered only after they grow. Several simultaneous multidirectional approaches performed as a single operation have been proposed, but the best strategy to remove these deeply situated large meningiomas involving the deep vital venous system remains to be established. The authors advocate a multistaged, multidirectional approach to safely remove these challenging tumors. METHODS Four consecutive cases of meningioma in the pineal region were treated between April 2013 and June 2016. The 3 large (> 40 mm diameter) tumors were removed via multistaged, multidirectional approaches (2 surgeries in 2 patients and 3 surgeries in 1 patient) with gravity retraction of the occipital or parietal lobe. The large occipital skin incision extending bilaterally was used for the next operation from the contralateral side. Combinations of the occipital transtentorial approach with or without the transfalcine approach, occipital bitranstentorial/falcine approach, combined supra-/infratentorial transsinus approach, and contralateral parietal interhemispheric transcallosal approach were used. RESULTS Transient visual field deficits occurred after 2 of the 8 operations, but all tumors were removed grossly or subtotally without permanent surgery-related morbidity. The galenic venous system and straight sinus remained intact in all patients. During the follow-up period (mean 29.5 months [range 13-52 months]), there were no recurrences after the final operation. CONCLUSIONS A multistaged, multidirectional strategy with an intentional large occipital scalp incision and gravity retraction of the occipital lobe is a good choice for the safe removal of large meningiomas in the pineal region.

Prevention of postoperative visual field defect after the occipital transtentorial approach: anatomical study.

OBJECTIVE A postoperative visual field defect resulting from damage to the occipital lobe during surgery is a unique complication of the occipital transtentorial approach. Though the association between patient position and this complication is well investigated, preventing the complication remains a challenge. To define the area of the occipital lobe in which retraction is least harmful, the surface anatomy of the brain, course of the optic radiations, and microsurgical anatomy of the occipital transtentorial approach were examined. METHODS Twelve formalin-fixed cadaveric adult heads were examined with the aid of a surgical microscope and 0° and 45° endoscopes. The optic radiations were examined by fiber dissection and MR tractography techniques. RESULTS The arterial and venous relationships of the lateral, medial, and inferior surfaces of the occipital lobe were defined anatomically. The full course of the optic radiations was displayed via both fiber dissection and MR tractography. Although the stems of the optic radiations as exposed by both techniques are similar, the terminations of the fibers are slightly different. The occipital transtentorial approach provides access for the removal of lesions involving the splenium, pineal gland, collicular plate, cerebellomesencephalic fissure, and anterosuperior part of the cerebellum. An angled endoscope can aid in exposing the superior medullary velum and superior cerebellar peduncles. CONCLUSIONS Anatomical findings suggest that retracting the inferior surface of the occipital lobe may avoid direct damage and perfusion deficiency around the calcarine cortex and optic radiations near their termination. An accurate understanding of the course of the optic radiations and vascular relationships around the occipital lobe and careful retraction of the inferior surface of the occipital lobe may reduce the incidence of postoperative visual field defect.

Occipital transtentorial/falcine approach, a "cross-court" trajectory to accessing contralateral posterior thalamic lesions: case report.

Surgical treatment of lesions in the posterior thalamus, especially those extending laterally, is technically challenging because of a deep surgical field, narrow operative corridor, and the surrounding critical neurovascular structures. The authors describe an occipital transtentorial/falcine approach (OTFA) that was successfully used in the treatment of a cavernous malformation (CM) extending laterally from thalamus to midbrain. A 40-year-old man complained of progressive right hemiparesis and numbness. Radiological evaluation revealed a large CM in the left thalamus, surfacing on the pulvinar thalami, and extending 4 cm laterally from the midline. In addition to the usual procedures of a right-sided occipital transtentorial approach, the authors incised the falx cerebri to expand the operative corridor to the left thalamus. They achieved generous exposure of the left thalamus through a "cross-court" oblique trajectory while avoiding excessive retraction on the occipital lobe. The CM was completely removed, and no newly developed or worsening deficits were detected postoperatively. To better understand the OTFA and its application, the authors performed a cadaveric dissection. The OTFA provides increased exposure of the posterior thalamus without cortical incision and facilitates lateral access to this area through the "cross-court" operative corridor. This approach adds to the armamentarium for neurosurgeons treating thalamic lesions.

Total Resection of Brainstem Extension of Tentorial Schwannoma Using an Occipital Transtentorial Approach.

BACKGROUND: Approximately 60 cases of schwannoma unrelated to the cranial nerve have been reported, and only 12 arose from the tentorium. We present a case of tentorial schwannoma extending into the pons and midbrain without cranial nerve involvement, which was almost totally resected with an occipital transtentorial approach. CASE DESCRIPTION: A 37-year-old man was admitted to our institution with memory disturbance beginning 2 years ago and gait disturbance from 1 year ago. Magnetic resonance imaging on admission revealed a heterogeneously enhanced 33 × 33 × 35 mm tumor in the pons and midbrain, and a dural tail sign connecting the lesion to the tentorial edge. Gross total resection of the tumor was performed with an occipital transtentorial approach. The trochlear nerve was identified and preserved, and the tumor did not involve this cranial nerve. The tumor was firmly attached to the edge of tentorium, and extended into the pons with sharp tumor border. Postoperative recovery was good, and brain magnetic resonance imaging performed 2 months after the surgical procedure revealed gross total removal of the lesion without signs of recurrence, but a slightly enhanced lesion in the right edge of the tentorium. CONCLUSIONS: The occipital transtentorial approach provides a direct approach to tentorial schwannoma, resulting in total resection even if the tumor extends into the pons and midbrain.