Occipital Interhemispheric Approach Research Articles

Falcotentorial Meningiomas: Insights from Surgical Strategies and Clinical Outcomes.

Background: Falcotentorial meningiomas are exceptionally uncommon tumors, presenting a challenge for neurosurgeons due to their close proximity to vital structures. Gross total resection represents the standard of treatment for these tumors. However, care must be taken when surgically approaching these lesions, since damaging neurovascular structures may cause unacceptable morbidity. Selecting the optimal surgical approach for each tumor is of paramount importance when treating these patients. Methods: The authors reviewed medical records to identify all patients with falcotentorial meningiomas who underwent resection at the University Hospital of Freiburg between January 2001 and December 2021. Clinical and imaging data, surgical management, and clinical outcomes were analyzed. Results: Falcotentorial meningiomas occurred in 0.7% (15 of 2124 patients) of patients with intracranial meningiomas. Of these 15 patients, 8 were female and 7 male. The occipital interhemispheric approach was used in nine patients, the supracerebellar infratentorial approach in five patients, and the retrosigmoidal approach in one patient. Three patients developed visual field deficits after surgical resection. Incomplete resection was significantly associated with tumor progression (p < 0.05). Conclusions: Individualized surgical strategies, guided by preoperative imaging and classification systems, play a crucial role in optimizing patient care. Among the available approaches, the occipital interhemispheric and supracerebellar infratentorial approaches are frequently employed and considered among the safest options for these tumors.

Occipital interhemispheric transtentorial approach in pediatric patients for lesions of the superomedial cerebellum: operative findings and results.

The occipital interhemispheric transtentorial (OITT) approach is frequently used for accessing the pineal region. There are scarce reports of using the OITT to access superior cerebellar lesions. This approach affords the patient several advantages over traditional posterior fossa approaches. This study is to describe and evaluate clinical outcomes in a single surgeon case series of the OITT approach for pediatric patients with lesions of the superior cerebellum. All pediatric patients who underwent an OITT craniotomy for a superior cerebellar lesion by a single surgeon over a 5-year period were included in this retrospective analysis. Patient demographics and clinical data were collected. Thirteen pediatric patients were identified. Cases included twelve tumors and one arteriovenous malformation. Gross total resection was achieved in 92% of cases. No patients developed posterior fossa syndrome. Two patients had transient homonymous hemianopsia that resolved by 1month post-operatively. There were no permanent neurological deficits. For superomedial cerebellar lesions presenting to the tentorial surface of the superior cerebellum in patients with normal to steep tentorial angles, the OITT approach is effective and safe. This approach has a low risk of posterior fossa syndrome and permanent visual deficits when applied appropriately. Patient selection is critical for maximizing the advantages of the OITT for superior cerebellar lesions.

Herophilus-Galen line as a predictor of extent of resection in the occipital interhemispheric transtentorial approach to pineal tumors in children.

The goals of this study were to evaluate the extent of resection (EOR) obtained with an occipital interhemispheric transtentorial approach (OITA) in a series of pediatric patients with pineal region tumors and to define preoperative radiological factors predictive of the EOR. This is a retrospective cohort study of a series of pediatric patients with pineal tumors who underwent surgery through a microsurgical OITA performed by the senior author during the period from January 2006 to January 2020. The tumor volume was measured preoperatively, and then on sagittal midline cuts the authors identified the most cranial point of the torcular Herophili (defined as the "Herophilus point") and the lowest point of the inferior profile of the vein of Galen (defined as the "Galen point"). The line joining these two points (defined as the "Herophilus-Galen line" [H-G line]) was used to identify the "Herophilus-Galen plane" (H-G plane) perpendicular to the sagittal plane. Tumor volumes located below and above this plane were measured. EOR was evaluated by measuring residual tumor volume visible on T1 volumetric injected sequences of immediate postoperative MRI. Thirty patients were selected for study inclusion. The preoperative mean tumor volume was 15.120 cm3 (range 0.129-104.3 cm3). The mean volumes were 2.717 cm3 (range 0-31 cm3) above the H-G plane and 12.40 cm3 (median 5.27 cm3, range 0.12-72.87 cm3) below the H-G plane. Three patients underwent only biopsy. Of the remaining 27 patients, gross-total resection (GTR; 100% tumor volume) was achieved in 20 patients (74%). In the remaining 7 patients, the mean residual tumor volume was 7.3 cm3 (range 0.26-17.88 cm3). In 3 of these patients, GTR was accomplished after further surgical procedures (1 in 2 patients, 3 in 1 patient) for an overall GTR rate of 85.18%. Larger tumor volume was significantly associated with incomplete resection (p < 0.001). A tumor volume ≤ 2 cm3 above the H-G plane (p = 0.003), linear extension ≤ 1 mm above the H-G line, and pineal histology were predictive of GTR at first OITA procedure (p = 0.001). The H-G line is an intuitive, easy-to-use, and reliable indicator of the superior anatomical limit of visibility during the microsurgical OITA. This anatomical landmark may be useful as a predictor of EOR for pineal tumors performed through this approach. The main limitations of this study are the small number of patients and the exclusively pediatric age of the patient population.

Surgical Management of Falcotentorial Junction Tumors: A Case Series Report.

ObjectiveThe surgical strategy for falcotentorial junction tumors remains complex. Different approaches are selected according to the location and growth pattern of the tumor and the operator’s experience. This report reviews our single-institution experience in the surgical management of falcotentorial junction tumors.MethodsWe retrospectively reviewed the clinical and imaging data, surgical strategy, and follow-up outcomes of 49 patients treated from 2007 to 2020.ResultAll 49 patients (12 male, 37 female, mean age: 56.3 ± 11.3 years) underwent safe tumor resection. The most common complaints were headache (43%), dizziness (39%), and unstable gait (16%). Thirty percent of the tumors showed calcification, and the computed tomography scans revealed hydrocephalus in 36% of the patients. On magnetic resonance imaging, 43% of the tumors were unilateral. According to the Asari classification, the tumors were divided into inferior (16%), superior (29%), anterior (22%), and posterior (33%) types. The occipital interhemispheric approach (88%) and supracerebellar–infratentorial approach (10%) were primarily used to reach the tumors. The pathology examination results revealed that 85.7% of the tumors were meningioma and 14.3% were hemangiopericytoma. Of the 49 patients, 15 achieved a Simpson grade I resection, and 29 achieved a Simpson grade II resection. The follow-up rate was 77.6% (38/45); 94.7% of patients (36/38) achieved a favorable outcome, and 9 experienced tumor recurrences.ConclusionSurgical approach selection depends on the growth characteristics of the tumor and the degree of venous or sinus involvement. The occipital interhemispheric approach is the most commonly used and safest approach for falcotentorial junction tumors with multiple brain pressure control assistance techniques.

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

Controversies exist regarding the ideal surgical approach for tumors in posterior third ventricular region (PTV). To evaluate the results of occipital interhemispheric transtentorial (OITT) approach for tumors in PTV. 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. 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. 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

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 occipital interhemispheric transtentorial approach (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. By using 30 clinical datasets of venous-phase head computed tomography angiogram, measurements on images were performed and differences between EOTA and EHOTA were identified. In addition, the feasibility of EHOTA was verified with 5 cadaver heads. 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 10 sides of the 5 cadaveric heads, as well as a case with anterosuperior cerebellar cavernous angioma. 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.

Occipital interhemispheric transtentorial approach to a pineoblastoma in a 4-year-old child.

The authors present a pediatric case of a pineoblastoma treated with gross-total removal through an occipital interhemispheric transtentorial approach (OITA). The child presented with acute hydrocephalus that was treated by endoscopic third ventriculostomy (ETV) and tumor biopsy through a single burr hole. Histology revealed a pineoblastoma. Microsurgical total removal was performed 3 months after neoadjuvant chemotherapy. OITA was chosen on the basis of the tumor’s location below the Herophilus-Galen line of sight. In this video, the authors show the positioning, the operating devices, the approach, and the microsurgical dissection, indicating all the neurovascular structures encountered.The video can be found here: https://stream.cadmore.media/r10.3171/2021.4.FOCVID2122.

Hybrid endovascular and microsurgical treatment for a large mesencephalic-cerebellar hemangioblastoma.

The large intracranial hemangioblastoma is a top surgical challenge due to its nature of invading brain parenchyma, tight adherence to the pia, and rich blood supply from numerous pial vasculatures and arteries in the proximity. If the brainstem is involved in the lesion, the surgery will be more dangerous because of potential brainstem impingement. In this illustrative video, we present a case of a 54-year-old male with a large hemangioblastoma at the mesencephalic-cerebellar region, which was successfully treated by hybrid endovascular embolization and microsurgery via an occipital interhemispheric transtentorial approach with minimal intraoperative blood loss and a favorable outcome.The video can be found here: https://youtu.be/pJqFhY_Zhv0.

Unedited microneurosurgery of a falcotentorial meningioma

Background:Falcotentorial meningiomas are pineal region meningiomas that arise from the dura of the tentorium cerebelli and posterior part of the falx. These tumors are commonly supplied by branches of the internal carotid artery such as the meningohypophyseal trunk, inferolateral trunk, and anterior choroidal artery. Less frequently, branches of the ophthalmic artery, vertebral artery, or external carotid artery are also involved. Based on neuroimaging studies, falcotentorial meningiomas may be classified as anterior, superior, inferior, and posterior types. Here, we present an unedited microsurgical resection of a superior falcotentorial meningioma.Case Description:The patient with a meningioma of the posterior inferior falx and a minimal extension to the tentorium underwent sitting praying position and a right occipital interhemispheric approach. Strong retraction of the dura followed a superior sagittal sinus based opening. Careful microsurgical access between the medial surface of the occipital lobe and the falx toward the splenium of corpus callosum allowed us to recognize the lesion. Thus, a cottonoid placed over the cerebral surface avoiding direct contact with the bipolar forceps, and the constant separation of the falx cerebri with the aspiration tube along the access developed a proper surgical route preventing any cortical lesion. Along the approach, cerebrospinal fluid was continuously released from the pericallosal cistern as well. Once well recognized the meningioma, we proceeded with the internal decompression of the lesion using a thumb regulated suction tube and bipolar forceps. Tissue samples from the tumor were taken for the histological diagnosis, and under conventional microsurgical technique, the meningioma was completely removed by piecemeal technique. A small lateral tear on the falx required hemostatic reparation with Tachosil. Water dissection provided us a clear cleavage plane for the microsurgical dissection of the tumor and maintained a clean operative field along the procedure. Occipital arteries running over the lateral surface of the meningioma were carefully dissected and isolated from the lesion, while the deep venous system did not achieve any contact with the tumor. After the ipsilateral component of the meningioma was resected, we intent are dissecting the contralateral segments of the tumor with a curved dissector. At the last stage of the surgery, small incision at a tumor-free segment of the falx allowed us to remove the falcotentorial attachment of the lesion. Under high microscopic magnification, the remaining minimal portion of meningioma extending under the tentorium was coagulated. After complete microsurgical removal of the meningioma, careful homeostasis based on electrocoagulation surgical and Tachosil was achieved. Finally, we performed a surgical wound closure under standard technique.Conclusion:This unedited video offers all detailed aspects for an efficient and safe falcotentorial meningioma microneurosurgery.Videolink:http://surgicalneurologyint.com/videogallery/pineal-meningioma.

Occipital Artery to Posterior Cerebral Artery Bypass Using Descending Branch of the Lateral Circumflex Femoral Artery Graft for Treatment of Fusiform, Unruptured Posterior Cerebral Artery Aneurysm: 3-Dimensional Operative Video.

Posterior cerebral artery (PCA) aneurysms can be technically challenging lesions due to the intricacy of perforating branches and the relationship to cranial nerves and the brainstem. Fusiform aneurysms of the perimesencephalic segment of the PCA are a rare finding which does not favor direct clip occlusion or reconstruction. In such cases, proximal parent vessel occlusion is an option for aneurysm treatment. Extracranial-intracranial (EC-IC) bypass can be used to revascularize beyond the lesion when considering proximal occlusion. Based on previous literature for occipital artery (OA) bypass and the time-consuming dissection required for OA harvest, an interposition graft was chosen. The descending branch of the lateral circumflex femoral artery (DLCFA) is a good alternative interposition graft with a diameter that is favorable for revascularizing smaller, more distal vessels.This 3-dimensional video presents the case of a 26-year-old female with severe headaches who was found to have unruptured, fusiform aneurysmal dilatations of the PCA. Given the patient's youth and the morphology of the aneurysms, an EC-IC bypass with proximal occlusion was recommended. The DLCFA was used as an interposition graft. The left OA was found to be a suitable donor. A subtemporal approach was used to access the PCA for proximal occlusion. An occipital interhemispheric approach was performed to isolate a suitable recipient segment of the ipsilateral PCA branch for microvascular end-to-side anastomosis. Postoperative catheter angiography showed significant thrombosis of the fusiform aneurysms and a patent EC-IC bypass. Postoperative magnetic resonance imaging showed no infarcts and the patient was discharged neurologically intact.The patient was consented for inclusion in a prospective institutional review board (IRB) approved database from which this IRB approved retrospective report was performed. The consent for intraoperative video and picture use was also obtained.Images in the video between 0:49 and 1:11, © University of Southern California Neurorestoration Center. Used with permission, all rights reserved.

Unedited microneurosurgery of a large recurrent papillary tumor of the pineal region.

Background:Papillary tumor of the pineal region (PTPR) is a new entity introduced in the 2007 World Health Organization (WHO) nomenclature to describe a rare grade II–III pineal lesion with epithelial-like papillary architecture and particular immunohistochemical features. PTPR is extremely rare in children. Herein, we present an unedited gross total microsurgical resection of a histologically confirmed WHO grade III PTPR. Our aim is to demonstrate the efficiency and safety of our microsurgical technique into deep brain territories under the principle “simple, clean, and preserving the normal anatomy.” For this, a posterior occipital interhemispheric approach and a proper praying sitting position were essential.Case Description:A patient with recurrent PTPR after a subtotal resection abroad underwent sitting praying position and left occipital craniotomy. The opened dura based on the superior sagittal sinus was strongly retracted providing hemostasis of the epidural space. The pericallosal cistern was reached by an interhemispheric approach with cerebrospinal fluid release. Under careful navigation, the tumor was recognized. Following high microscopic magnification, tissue samples were obtained for immediate histological studies and internal debulking of the tumor was performed with ring forceps and long bipolar forceps as well. After a careful dissection and devascularization of the lesion, the tumor was softly but constantly pulled out with long ring microforceps in the right hand, whereas a thumb-regulated suction tube in the left hand acted oppositely, detaching the lesion from surrounding structures. Bipolar coagulation forceps were used to shrink the tumor and to remove it by piecemeal reduction. Water irrigation provided a clean surgical field and helped us to separate deep borders of the lesion by water dissection technique. Finally, careful tumor detachment from the deep venous system and meticulous hemostasis of the surgical site ensured a safe surgery. The postoperative course was uneventful. The patient underwent radiohemotherapy as an adjuvant treatment and is alive and free of recurrence almost 4 years after surgery.Conclusion:This unedited video offers all detailed aspects that are, as the senior author JH considers, essential for a neurosurgeon when performing an efficient and safe surgery into the pineal region for this very rarely documented papillary tumor.Videolink:http://surgicalneurologyint.com/videogallery/pineal-region-tumor

Microsurgical Resection After Failed Gamma Knife Radiosurgery of Papillary Tumor of the Pineal Gland.

Abstract Primary papillary tumors of the pineal region (PTPR) are rare entities with distinct histopathological characteristics. Most common surgical approaches include the supra-cerebellar infratentorial corridor or the occipital interhemispheric approach. Gamma knife radiosurgery (GKRS) is an acceptable treatment modality for parenchymal tumors of the pineal gland, and often used as a primary treatment modality for asymptomatic and indolent lesions, and as an adjunct to surgical resection. In this presentation, we describe the surgical nuances of posterior interhemispheric approach in an elderly male with a previously failed empirical GKRS. Intraoperatively, the tumor was mostly avascular, presumed to be due to prior GKRS; however, a good tumor-brain interface allowed a gross total resection of the mass. Histopathological examination of the mass was consistent with PTPR. Post-operative course was uneventful and long-term follow up showed no signs of tumor recurrence. The video discusses radiological findings, clinic-pathological correlates, and emphasizes on key microsurgical techniques including the significance of patient positioning and incision type for meticulous resection of pineal tumors.

Abscess in the Splenium of the Corpus Callosum Treated with Direct Drainage via an Occipital Interhemispheric Approach

Lesions in the corpus callosum typically represent malignant tumors such as glioblastoma or lymphoma, because of its compact structure comprising tightly packed white-matter tracts. Brain abscess is rarely seen in the corpus callosum. To the best of our knowledge, solitary bacterial abscess confined to the splenium of the corpus callosum has not been reported previously. We report the case of a 72-year-old woman with rapidly progressing disturbance of consciousness following 1 week of antibiotic treatment for bacterial meningitis. Magnetic resonance imaging demonstrated a ring-enhancing round mass located in the splenium of the corpus callosum on gadolinium-enhanced T1-weighted imaging, also showing a bright signal on diffusion-weighted imaging. The patient underwent occipital craniotomy and direct drainage of the lesion in the splenium through the interhemispheric fissure and achieved complete recovery. Brain abscess should be considered among the differential diagnoses for lesions in the splenium of the corpus callosum. An occipital interhemispheric approach to the splenium might be an important option in cases of brain abscess.

The role of surgery in treatment of pineal germinoma: A case report

Objective – The aim of this case report is to present the results of surgical treatment of a patient with the pineal germinoma. Case report – A 12-year-old patient presented with two months history of headache, nausea, and vomiting, following by neuro-ophthalmologic disturbances (Parinaud syndrome). Computed tomography of the head showed a 3 cm mass in the pineal region, followed by obstructive hydrocephalus, and magnetic resonance imaging showed a pineal gland lesion with heterogeneous enhancement on contrast studies, with surrounding peritumoral edema, suggesting pineal germinoma. The patient underwent surgery to place a ventricular-peritoneal shunt, and second surgery using the occipital interhemispheric transtentorial approach to remove the tumor totally. Conclusion – Pineal germinomas that compress adjacent structures result in a typical clinical syndrome with endocrine malfunction, hydrocephalus or neuro-ophthalmological disturbances. A multimodality approach, including chemotherapy, radiotherapy and surgery, can offer excellent chances of free survival, and even cure.

Occipital-posterior cerebral artery bypass via the occipital interhemispheric approach

Background:The unavailability of the superficial temporal artery (STA) and the location of lesions pose a more technically demanding challenge when compared with conventional STA-superior cerebellar or posterior cerebral artery (PCA) bypass in vascular reconstruction procedures. To describe a case series of patients with cerebrovascular lesions who were treated using an occipital artery (OA) to PCA bypass via the occipital interhemispheric approach.Methods:We retrospectively reviewed three consecutive cases of patients with cerebrovascular lesions who were treated using OA-PCA bypass.Results:OA-PCA bypass was performed via the occipital interhemispheric approach. This procedure included: (1) OA-PCA bypass (n = 1), and combined OA-posterior inferior cerebellar artery and OA-PCA saphenous vein interposition graft bypass (n = 1) in patients with vertebrobasilar ischemia; (2) OA-PCA radial artery interposition graft bypass in one patient with residual PCA aneurysm.Conclusions:OA-PCA bypass represents a useful alternative to conventional STA-SCA or PCA bypass.

Meningioma of the pineal region

Abstract Meningiomas rarely occur in the pineal region, but they can reach huge diameters. We presented the case of a patient with a very large meningioma of the pineal region (6x5x4 cm). The tumor, developed from the falcotentorial junction, was totally removed via an occipital interhemispheric transtentorial approach with minimal postoperative neurological deficits. The postoperative course was complicated with an acute internal hydrocephalus that needed temporary placement of an external ventricular drainage. The supratentorial surgical corridors allow for increased exposure and are best suited for falcotentorial meningiomas.

Occipital interhemispheric transtentorial approach to the superior cerebellum

The occipital interhemispheric transtentorial approach is commonly used for pineal region tumors. However, there are few reports of this approach for lesions in the superior cerebellum. We present a 47-year-old male patient with an incidental cystic lesion in the superior cerebellum, detected on MRI consistent with cerebellar hemangioblastoma. The patient initially underwent stereotactic radiosurgery. After 5 months he presented with dizziness. A repeat MRI scan revealed an interval increase in lesion size. We performed surgery using the occipital interhemispheric transtentorial approach to remove the lesion. There were no intraoperative complications and the patient tolerated the procedure well. We describe our approach, supplemented by a short video, and review operative approaches to the superior cerebellum.

Aneurysm on the Cortical Branch (P4 Segment) of the Posterior Cerebral Artery -Case Report-

A 75-year-old woman presented with a rare aneurysm on the distal portion (P(4)) of the posterior cerebral artery (PCA) causing subarachnoid hemorrhage (SAH) and manifesting as sudden onset of headache, nuchal rigidity, and nausea. Computed tomography on admission revealed thin SAH in the left parietooccipital sulcus. Cerebral angiography demonstrated a small saccular aneurysm on the cortical branch of the left PCA. The aneurysm was successfully clipped via the occipital interhemispheric approach. Distal PCA aneurysms frequently affect middle-aged persons and tend to be small, with good clinical course but may cause visual field defects. Direct aneurysm clipping is recommended for patients without visual defect from the onset. Parent artery occlusion by the endovascular technique should be considered for patients with visual loss caused by the initial hemorrhage.

Occipital inter-hemispheric approach for lateral ventricular trigone meningioma

The optimal surgical approach for a trigone meningioma is still controversial. Here, we report two patients with trigone meningioma treated successfully via an occipital inter-hemispheric and trans-cortical approach in the lateral semi-prone position. A 53-year-old woman was admitted to a local hospital with sudden transient dizziness and vomiting. The CT brain scan demonstrated a right intra-ventricular tumour. She was therefore transferred to our hospital for surgical treatment. The other patient was a 67-year-old woman who was admitted to a local hospital after a traffic accident and a CT brain scan revealed an incidental right intra-ventricular tumour. After referral to our hospital, periodic MRI examinations revealed gradual tumour enlargement within a one-year period. Neither of the patients had any neurological deficits, including in the visual fields. The head of each patient was positioned so that the tumour-containing right ventricle was oriented downwards and laterally. An occipital inter-hemispheric approach was performed and using a navigation system, the tumour was identified about 1 cm in depth from the cortical surface. After the medial part of the tumour was debulked, the posterior and then the anterior choroidal blood supplies to the tumour were identified. Occlusion of these vessels achieved tumour haemostasis. The tumours were totally removed via a 1.5-cm cortical incision. Brain retraction was minimal because the right hemisphere was pulled down by gravity. Therefore, the para-splenial cisterns were easily accessed, resulting in early release of cerebrospinal fluid. Post-operative MRI showed complete removal of the tumour and the patients had no neurological deficits. Anti-epileptic medication was withdrawn one week after the operation. The occipital inter-hemispheric fissure lacks important bridging veins. The approach used and patient positioning minimized damage to the lateral aspect of the optic radiation and the corpus callosum. Except in patients with very large trigone meningiomas, this approach is useful for decreasing the risk of post-operative hemianopsia or epilepsy, and possibly speech disturbance, even in patients with a tumour in the dominant hemisphere.

Occipital interhemispheric approach without excision of tentorium for the tumor in the medial temporal region: technical note

Background An occipital interhemispheric approach for the lesions in the middle part of the medial temporal region has been reported. However, this approach usually requires the excision of the tentorium to provide satisfactory exposure. In this case, we used this approach without the excision of the tentorium to remove the parahippocampal gyrus tumor, which was located superolateral to tentorial edge in the middle part of the medial temporal region. Case Description A 22-year-old man who had seizures for 3 years presented with a tumor in the right parahippocampal gyrus. The tumor was successfully removed by the occipital interhemispheric approach without the excision of the tentorium. The postoperative course was uneventful. Conclusions An occipital interhemispheric approach without the excision of tentorium is a feasible and safe approach for parahippocampal tumors superolateral to tentorial edge, even in a case where the tumor is deeply located in the middle part of medial temporal region.