Midline Suboccipital Approach Research Articles

Occipital Sinus-Sparing Linear Paramedian Dural Incision: A Technical Note and Case Series for Median Suboccipital Approach

Durotomies, traditionally used during the midline suboccipital approach, involve sacrificing the occipital sinus (OS) with consequent shrinking of the dura, risk of venous complications, difficulty performing watertight closure, and a higher rate of postoperative cerebrospinal fluid (CSF) leaks. The present technical note describes the OS-sparing linear paramedian dural incision, which leads to a decrease in the risk of complications during the median suboccipital approach in our case series. The OS-sparing linear incision technique involves a dural incision placed 1cm lateral to the OS. The angle of view of the microscope is frequently changed to overcome the narrowed exposure of the linear durotomy. Copious irrigation with saline prevents drying of the dura. A running watertight closure of the dura is performed. The overall results of 5 cases are reviewed. The cases were 3 tumors and 2 cavernomas. The OS was preserved in all 5, and no duraplasty was needed. The average dura closure time was 16.8minutes. No CSF leak occurred, and no wound complications were observed. A gross total resection of the lesion was achieved in all the patients. The mean follow-up was 10.2months, and there were no late complications related to the dura closure. In comparison to the types of durotomies conventionally used for the midline suboccipital approach, the OS-sparing linear paramedian dural incision entails lower risks of bleeding, venous complications, CSF leaks, and infections by avoiding duraplasty. Validation of this technical note on a larger patient cohort is needed.

Accessory nerve meningioma. A case report and literature review

Meningiomas arising from accessory nerve sheath without dural attachment are rare. To date, only 5 cases are described in the literature. A 53-year-old male presented with long history of occipital pain and headaches. Magnetic resonance imaging revealed a small intradural extramedullary contrast enhanced tumor at the level of foramen magnum. The patient underwent microsurgical resection through minimally invasive midline suboccipital approach. According to intraoperative findings, cystic tumor arose from the left accessory nerve without dural attachment. Gross total resection was achieved without damage to the nerve. Histological analysis revealed angiomatous meningioma. Postoperative period was uneventful without new neurological symptoms. Meningiomas can rarely arise from accessory nerve sheath and mimic schwannoma. These tumors may be totally resected without damage to accessory nerve using minimally invasive surgical approaches.

Glioependymal cyst in the medulla oblongata – A case report

Background: Glioependymal cysts (GECs) are rare benign lesions that can be found anywhere along the neuroaxis, with most of the reports denoting supratentorial location. Here, we introduce a rare case of successfully treated glioependymal cysts lying in an uncommon location, namely medulla oblongata. Case Description: A 69-year-old lady presented with progressive unsteadiness and swallowing disturbances, and brain magnetic resonance imaging showed a dorsally located lesion within the medulla oblongata; based on the presentation and radiological features, surgical intervention was deemed mandatory. The suboccipital midline approach was used to perform marsupialization of the cyst with shunting through a syringosubarachnoid shunt to prevent future recurrence, and the patient outcome was improved. Conclusion: Medulla Oblongata’s location for glioependymal cysts proposed unique diagnostic and operative challenges that may require highlighting for practicing neurosurgeons.

10159-STMO-7 INTRAOPERATIVE MRI SURGERY FOR POSTERIOR FOSSA LESIONS

Abstract Background: Intraoperative MRI (iMRI) is an important modality in brain tumor surgery to identify residual tumors, however, it is problematic due to patient positional limitations. In this study, we investigated the usefulness of iMRI for posterior fossa lesions. Materials and Methods: Of 320 cases of brain tumors removed using iMRI from June 2016 to April 2023, 24 cases of posterior fossa lesions were included. Tumor type, approach method, imaging availability, tumor removal rate, and complications were examined retrospectively. Results: Tumor types included 8 gliomas, 5 epidermoid cysts, 4 meningiomas, 3 metastatic brain tumors, 1 schwannoma, and 3 others. Eleven patients underwent midline suboccipital approach in the supine position, 8 patients underwent lateral suboccipital approach, 2 patients underwent occipital transtentorial approach, and 2 patients underwent anterior transpetrosal approach in the supine position. transpetrosal approach in 2 cases and subtemporal approach in 1 case. iMRI showed residual lesion in 14 of 24 patients. More than half of the gliomas and epidermoid cysts had intraoperative residual disease, whereas only one meningioma did. Total resection was achieved except for one case of intentional residual schwannoma and two cases of glioma. Discussion: iMRI requires the upper body to fit within a gantry, and it is difficult to image in the park bench position. However, various approaches is possible by using a supine-lateral or semi-prone position. In the concorde position, where the fourth ventricle and upper cerebellum are approached, it is useful to insert a mat in the anterior thoracic and raise the upper body. For tumors in the dorsal brainstem and upper cerebellum, the occipital transtentorial approach was used. iMRI is effective in the removal of all tumors, including gliomas in intramedullary tumors and epidermoid cysts in extramedullary tumors. Conclusion: iMRI can be used in posterior cranial fossa lesions.

Experience and Balance: Long-Term Trends in Preferred Skull Base Approach for a Case Series of Cavernous Malformation Resections.

Skull base approaches are a foundation of modern cerebrovascular surgery; however, their application over time has varied. To assess trends in skull base approach selection for cavernous malformation (CM) resection. This is a retrospective case series of all first-time CM resections by a single surgeon from 1997 to 2021. Cases were classified by craniotomy and approach. Four sets of common comparator skull base approaches were identified by coauthor consensus: pterional and orbitozygomatic; retrosigmoid, extended retrosigmoid (xRS), and far-lateral; suboccipital and torcular; and trans-cerebellar peduncle (MCP) and transcerebellopontine angle. Counts were binned by 5-year or 10-year clusters for descriptive statistical assessment of temporal trends. In total, 372 primary CM resections met the study criteria and were included. Orbitozygomatic approach use increased during the second 5-year period, after which the pterional approach rapidly became and remained the preferred approach. During the first two 5-year periods, the far-lateral approach was preferred to the retrosigmoid and xRS approaches, but the xRS approach grew in popularity and accounted for >50% of operations in this comparator group. Trans-MCP use compared with the transcerebellopontine angle approach closely mirrored the change in xRS use. The midline suboccipital approach accounted for a larger proportion (range, 62%-88%) of cases than the torcular approach (range, 12%-38%) across all periods. The xRS and trans-MCP approaches have been increasingly used over time, while the orbitozygomatic and far-lateral approaches have become less common. These trends seem to reflect versatility, efficiency, and safety of these techniques.

A system of anatomical triangles defining dissection routes to brainstem cavernous malformations: definitions and application to a cohort of 183 patients.

Anatomical triangles defined by intersecting neurovascular structures delineate surgical routes to pathological targets and guide neurosurgeons during dissection steps. Collections or systems of anatomical triangles have been integrated into skull base surgery to help surgeons navigate complex regions such as the cavernous sinus. The authors present a system of triangles specifically intended for resection of brainstem cavernous malformations (BSCMs). This system of triangles is complementary to the authors' BSCM taxonomy that defines dissection routes to these lesions. The anatomical triangle through which a BSCM was resected microsurgically was determined for the patients treated during a 23-year period who had both brain MRI and intraoperative photographs or videos available for review. Of 183 patients who met the inclusion criteria, 50 had midbrain lesions (27%), 102 had pontine lesions (56%), and 31 had medullary lesions (17%). The craniotomies used to resect these BSCMs included the extended retrosigmoid (66 [36.1%]), midline suboccipital (46 [25.1%]), far lateral (30 [16.4%]), pterional/orbitozygomatic (17 [9.3%]), torcular (8 [4.4%]), and lateral suboccipital (8 [4.4%]) approaches. The anatomical triangles through which the BSCMs were most frequently resected were the interlobular (37 [20.2%]), vallecular (32 [17.5%]), vagoaccessory (30 [16.4%]), supracerebellar-infratrochlear (16 [8.7%]), subtonsillar (14 [7.7%]), oculomotor-tentorial (11 [6.0%]), infragalenic (8 [4.4%]), and supracerebellar-supratrochlear (8 [4.4%]) triangles. New but infrequently used triangles included the vertebrobasilar junctional (1 [0.5%]), supratrigeminal (3 [1.6%]), and infratrigeminal (5 [2.7%]) triangles. Overall, 15 BSCM subtypes were exposed through 6 craniotomies, and the approach was redirected to the BSCM by one of the 14 triangles paired with the BSCM subtype. A system of BSCM triangles, including 9 newly defined triangles, was introduced to guide dissection to these lesions. The use of an anatomical triangle better defines the pathway taken through the craniotomy to the lesion and refines the conceptualization of surgical approaches. The triangle concept and the BSCM triangle system increase the precision of dissection through subarachnoid corridors, enhance microsurgical execution, and potentially improve patient outcomes.

Anatomical Step-by-Step Dissection of Midline Suboccipital Approaches to the Fourth Ventricle for Trainees: Surgical Anatomy of the Telovelar, Transvermian, and Superior Transvelar Routes, Surgical Principles, and Illustrative Cases.

Introduction Safe, effective access to the fourth ventricle for oncologic resection remains challenging given the depth of location, restricted posterior fossa boundaries, and surrounding eloquent neuroanatomy. Despite description in the literature, a practical step-by step dissection guide of the suboccipital approaches to the fourth ventricle targeted to all training levels is lacking. Methods Two formalin-fixed, latex-injected specimens were dissected under microscopic magnification and endoscopic visualization. Dissections of the telovelar, transvermian, and supracerebellar infratentorial-superior transvelar approaches were performed by one neurosurgery resident (D.D.D.), under guidance of senior authors. The dissections were supplemented with representative clinical cases to highlight pertinent surgical principles. Results The telovelar and transvermian corridors afford excellent access to the caudal two-thirds of the fourth ventricle with the former approach offering expanded access to the lateral recess, foramen of Luschka, adjacent skull base, and cerebellopontine angle. The supracerebellar infratentorial-superior transvelar approach reaches the rostral third of the fourth ventricle, the cerebral aqueduct, and dorsal mesencephalon. Key steps described include positioning and skin incision, myofascial dissection, burr hole and craniotomy, durotomy, the aforementioned transventricular routes, and identification of relevant skull base landmarks. Conclusion The midline suboccipital craniotomy represents a foundational cranial approach, particularly for lesions involving the fourth ventricle. Operatively oriented resources that combine stepwise neuroanatomic dissections with representative cases provide a crucial foundation for neurosurgical training. We present a comprehensive guide for trainees in the surgical anatomy laboratory to optimize familiarity with fourth ventricle approaches, mastery of relevant microsurgical anatomy, and simultaneous preparation for learning in the operating room.

Classification and microsurgical treatment of foramen magnum meningioma

BackgroundTo investigate the classification and microsurgical treatment of foramen magnum meningioma (FMM).MethodsWe retrospectively analyzed 76 patients with FMM and classified them into two classifications, classification ABS according to the relationship between the FMM and the brainstem and classification SIM according to the relationship between the FMM and the vertebral artery (VA). All patients underwent either the far lateral approach (54 cases) or the suboccipital midline approach (22 cases).ResultsOf the 76 cases, 47 cases were located ahead of the brainstem (A), 16 cases at the back of the brainstem (B), and 13 cases were located laterally to the brainstem (S). There were 15 cases located superior to the VA (S), 49 cases were inferior (I), and 12 cases were mixed type (M). Among 76 cases, 71 cases were resected with Simpson grade 2 (93.42%), 3 with Simpson grade 3 (3.95%), and 2 with Simpson grade 4 (2.63%). We summarized four anatomical triangles: triangles SOT, VOT, JVV, and TVV. The mean postoperative Karnofsky performance score was improved in all patients (p < 0.05). However, several complications occurred, including hoarseness and CSF leak.ConclusionABS and SIM classifications are objective indices for choosing the surgical approach and predicting the difficulty of FMMs, and it is of great importance to master the content, position relationship with the tumor, and variable anatomical structures in the four “triangles” for the success of the operation.

Duraplasty with autologous nuchal ligament fascia to reduce postoperative complications in pediatric patients undergoing neoplasia resection with a suboccipital midline approach.

The authors sought to explore the safety and efficacy of an autologous nuchal ligament for dural repair in pediatric patients undergoing tumor resection through a suboccipital midline approach. Pediatric patients diagnosed with posterior fossa neoplasia who underwent surgery through a suboccipital midline approach were retrospectively reviewed. The patients were divided into artificial graft and autograft groups according to whether artificial duraplasty material or autologous nuchal ligament was used to repair the dura. Postoperative complications were reviewed and analyzed, including CSF leak, pseudomeningocele, and meningitis, during hospitalization and follow-up. Univariate and multivariate logistic regression analyses were used to investigate the relationship between duraplasty material and postoperative complications, as well as other risk factors for postoperative complications. Furthermore, multinomial logistic regression analysis was used to clarify which postoperative complications the autologous nuchal ligament tended to reduce. This retrospective study included 66 pediatric patients who underwent tumor resection through a suboccipital midline approach. The clinical baseline characteristics were comparable between the two groups. The results showed that the autograft group had significantly fewer postoperative complications, especially pseudomeningocele, compared with the artificial graft group. Moreover, the time required to repair the dura in the autograft group was significantly less than that in the artificial graft group. Further results revealed that the duraplasty material, ependymoma, preoperative severe hydrocephalus requiring an external ventricular drain (EVD), and postoperative hydrocephalus exacerbation were independent risk factors for postoperative complications. In particular, the autologous fascia of the nuchal ligament tended to reduce pseudomeningocele more than CSF leak and meningitis. However, compared with pseudomeningocele and CSF leak, both ependymoma and postoperative hydrocephalus exacerbation were more likely to increase the occurrence of meningitis. In contrast, preoperative severe hydrocephalus requiring EVD led to increased rates of postoperative complications. For pediatric patients with intracranial tumors who need to undergo resection through a suboccipital midline approach, dural repair using the nuchal ligament is safe, cost-effective, and time saving and significantly reduces postoperative complications.

Microsurgical Management of Fourth Ventricle Lesions Via the Median Suboccipital Keyhole Telovelar Approach.

In this 2-year retrospective analysis, 13 patients with fourth ventricle lesions who underwent microsurgical resection via the midline suboccipital keyhole telovelar approach were analyzed. This is the first study to investigate the surgical outcome and complications of using this approach to resect various types of lesions in the fourth ventricle. We aimed to clarify whether this approach has met its promise of lesion dissection. Three patients (23.1%) had intraoperative extraventricular drains. There were no immediate postoperative deaths. Gross total resection was achieved in 84.6% of the cases. The Fisher exact test showed there was no statistically significant correlation between lesion location, lesion size, brainstem invasion, and extent of resection. About two third (69.2%) of the cases were free of complications. New or worsening gait/focal motor disturbance (15.4%) was the most common neurological deficit in the immediate postoperative period. One patient (7.7%) had worse gait disturbance/motor deficit following surgical intervention. Two patients (15.4%) developed meningitis. Two patients (15.4%) required postoperative cerebrospinal fluid diversion after tumor resection, of these 2 patients, 1 (7.7%) eventually needed a permanent shunt. There were no cases of cerebellar mutism and bulbar paralysis. The median suboccipital keyhole telovelar approach provides relative wide access to resect most fourth ventricle tumors completely and with satisfactory results. In contrast, this requires the appropriate patient selection and skilled surgeons.

ATRT-18. Atypical Teratoid/Rhabdoid Tumor in Children: Case Reports from Indonesia

Atypical teratoid/rhabdoid tumor (AT/RT) of the central nervous system is a sporadic and highly malignant tumor that usually affects very young children and is typically deadly despite very aggressive treatment. The optimal treatment for AT/RT remains unclear, including surgery, radiotherapy, and chemotherapy. Here we report cases of AT/RT in Indonesia. Case 1: A three-year-old girl came with worsening intermittent headaches with projectile vomiting, progressive and insidious right spastic hemiparesis, and slowly progressive weight loss three months before admission. She had septate multiloculated hydrocephalus. Head MRI demonstrates a solid lobulated mass with heterogeneous enhancement and MRS shows an aggressive metabolite pattern, arising from posterior fossa extending into the cerebellum and cerebellopontine angle, causing severe obstructive hydrocephalus. She underwent tumor resection with a midline suboccipital approach, then continued with craniospinal irradiation with dose of 36 Gy in 20 fractions then followed by 18 Gy in 10 fractions booster to posterior fossa, making the total dose to posterior fossa (the tumor) to be 54 Gy. Case 2: A twenty-month-old baby with a history of recurrent seizures, tremors, and less activity in the last two months. She had spasticity with hyperreflexia. She has been referred to our center for further evaluation and management after biopsy and VP shunt surgery at the previous hospital. Head CT scan demonstrates a large solid heterogeneous mass in the right hemisphere cerebral, causing midline shift and hydrocephalus. After the VP shunt was repaired, she underwent Head Start III chemotherapy protocol cycle 1. Both pathology examinations of the patients revealed a hypercellular tumor with prominent hyperchromatic nucleoli and loss of INI-1 staining on immunohistochemistry consistent with an ATRT diagnosis. Unfortunately, both patients died due to severe sepsis after treatment. Although AT/RT has become increasingly recognized, prognosis of ATRT is generally unfavorable, especially in developing countries.

Microsurgical treatment of posterior inferior cerebellar aneurysms based on angioarchitecture supplemented by high-resolution vessel wall MRI: a case series report

BackgroundSurgical treatment of posterior inferior cerebellar artery (PICA) aneurysms is challenging because many are nonsaccular and atherosclerotic. We report our tailored approach to PICA aneurysms, which is based on angioarchitecture...

Dealing with a Pediatric Posterior Fossa Tumor after COVID-19 Infection: Report of One Case

Plain Language SummaryHaving the issue of coronavirus disease 2019 (COVID-19) in mind, there is always a dilemma surrounding elective and non-urgent neurosurgical operations. The unanswered question is regarding whether there is any post-COVID-19 complications that hinder a patient from becoming a candidate for a neurosurgical operation. If that is the case, what should we do?In the present article, we report our single-center experience with an unusual bleeding during the operation of a huge cerebellar tumor in a girl previously infected with COVID-19. In the end, we recommend our experience to our colleagues. Abstract There are still some conditions that pediatric neurosurgeons may face in the context of coronavirus disease 2019 (COVID-19) which have not been fully addressed so far. Authors have postulated an ongoing inflammatory myocardial status in a significant proportion of patients who have recovered from COVID-19. We report our experience with a 10-month-old girl who had recovered form COVID-19 and had a case of fourth-ventricle mass in the midline of the posterior fossa. She was scheduled for microneurosurgical resection of the mass following the insertion of a ventriculoperitoneal shunt. There were no significant issues regarding the induction of anesthesia. A midline suboccipital approach was chosen, and the patient was fully prepared and draped. Suboccipital soft tissues and muscles were dissected layer by layer through the midline avascular line. A marked gush of blood off the midline was observed during the opening in Y of the dura mater. Then, we started to approach the occipital sinus. However, there was an unusual loss of ∼ 200 mL of blood lost from this area. Despite the proper packed-cell transfusion, the patient developed bradycardia and a sudden rhythm of asystole. The cardiopulmonary cerebral resuscitation (CPCR) was initiated immediately. Despite the maximal effort, the heart rate did not change and remained asystole. We recommend that pediatric neurosurgeons postpone the procedures to be performed in patients who have recovered from COVID-19 for more than one month after a thorough preoperative cardiac evaluation has been performed.

Anatomy of the greater occipital nerve: implications in posterior fossa approaches.

Because of its superficial location in the dorsal regions of the scalp, the greater occipital nerve (GON) can be injured during neurosurgical procedures, resulting in post-operative pain and postural disturbances. The aim of this work is to specify the course of the GON and how its injuries can be avoided while performing posterior fossa approaches. This study was carried out at the department of anatomy at Bordeaux University. 4 specimens were dissected to study the GON course. Posterior fossa approaches (midline suboccipital, paramedian suboccipital, retrosigmoid and petrosal) were performed on 4 other specimens to assess potential risks of GON injuries. The GON runs around the obliquus capitis inferior (100%), crosses the semispinalis capitis (100%) and the trapezius (75%) or its aponeurosis (25%). Direct GON injuries can be seen in paramedian suboccipital approaches. Stretching of the GON can occur in midline suboccipital and paramedian suboccipital approaches. We found no evidence of direct or indirect GON injury in retrosigmoid or petrosal approaches. Our study provides interesting data regarding the risk GON injury in posterior fossa approaches. Direct GON injuries in paramedian suboccipital approaches can be avoided with careful dissection. Placing retractors in contact with the periosteum and performing a minimal retraction may help to avoid excessive GON stretching in midline suboccipital and paramedian suboccipital approaches. Furthermore, the incision for retrosigmoid approaches should be as lateral as possible and not too caudal. Finally, avoiding extreme patient positioning reduces the risk of GON stretching in all approaches.

Suboccipital midline approach with C1 laminectomy and C2 partial laminectomy for anterolateral foramen magnum meningioma: A case report

Introduction: Foramen magnum meningiomas (FMMs) arise from meningothelial cells of arachnoid layer in the craniospinal junction. FMMs are rare and comprise only 1.8 to 3.2% of all meningiomas. Patients with FMMs generally have vague symptoms and are often misdiagnosed. Surgical management of FMMs poses a challenge because foramen magnum is a highly complex territory of the skull base and contains many important and vital structures. Up until this date, the surgical approaches for FMMs that arise anterolaterally remain varied. We aimed to present a case of anterolateral FMM that was successfully managed through posterior suboccipital midline approach.Case presentation: A 49-year-old female presented with chief complaint of tetra paresis for the past 4 months. Initially, she was experiencing tingling and numbness on her right neck radiating to her right hand. Her symptoms were worsened, radiating to all of her four extremities along with progressive motor weakness that made her unable to walk. Whole spine MRI was performed and anterior meningioma extending to the right side at the level of foramen magnum was found. The posterior suboccipital midline approach with C1 laminectomy and C2 partial superior laminectomy was performed. The patient made a good recovery immediately after the surgery and there was no recurrence of her symptoms during 4 months follow-up.Conclusion: Surgical approaches for FMM remain varied according to several studies. However, the surgical strategy should be patient-tailored to achieve the maximal resection and prevent morbidity. As for our case, posterior suboccipital midline approach is safe and feasible surgical procedure to treat anterolateral FMM.Keywords: foramen magnum, meningioma, suboccipital midline approach

Endoscopic-Assisted Resection of Anterior Foramen Magnum Meningiomas through a Midline Suboccipital Subtonsillar Approach.

Objective This study was aimed to demonstrate the resection of anterior foramen magnum meningiomas through an endoscopic-assisted posterior midline suboccipital subtonsillar approach. Design This study was designed with illustration of the surgical steps and safety of this approach. Setting Evidence of cerebrospinal fluid (CSF) cleft between the tumor and brainstem on MRI was studied ( Fig. 1A and B ). Preoperative tracheotomy was considered in cases of preoperative dysphagia to prevent any further neurological deterioration due to the bilateral access through the lower cranial nerves corridors. Semisitting position with extensive electrophysiological neuromonitoring and transesophageal echocardiogram was adopted. A standard midline incision with bilateral suboccipital craniotomy and C1-laminotomy was performed ( Fig. 2A ). After partial resection and elevation of the tonsils, tumor was debulked unilaterally around the lower cranial nerves and the vertebral artery, devascularized from the clival dura and then dissected from the brainstem ( Fig. 2B, C ). Endoscopic-assisted removal of its anterior portion followed. The same procedure was repeated from the opposite site for the contralateral portion, before approaching the purely anterior part with endoscope assistance ( Fig. 2D ). Participants Four consecutive patients were included in the study. Main Outcome Measures Grade of tumor resection and outcome (mRS) were primary measurement of this study. Results Clinical outcome and grade of resection are comparable to other series of patient treated with other foramen magnum approaches ( Fig. 1C and D ). Conclusion Anterior foramen magnum meningiomas can be safely removed through this relatively faster midline suboccipital approach with bilateral exposure of lower cranial nerves (CNs) and vertebral arteries and lower approach-related morbidity (no condyle drilling). The surgical corridor is created by the tumor during debulking reducing need for brain retraction and the removal of the anterior dural attachment coagulated under the microscope is verified and completed endoscopically with pituitary curettes (Simpson's grade II) ( Fig. 1C and D ). The link to the video can be found at: https://youtu.be/9eACAJVwQBs .

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 tentorialsinus orstraight 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.

RONC-25. A CASE OF PEDIATRIC PONTINE GLIOMA TREATED WITH GAMMA KNIFE SURGERY

BACKGROUNDPediatric brainstem gliomas rarely occur and are a heterogeneous group of diseases, which increases the difficulty of treatment strategy. Here, we present a case of pediatric pontine glioma treated with Gamma Knife surgery (GKS) after open biopsy. CASE DESCRIPTION: An 11-year-old boy presented with diplopia due to the left MLF syndrome. MRI showed a well-circumscribed, protruding tumor with partial gadolinium enhancement in the dorsal pons. An open biopsy was performed via the suprafacial triangle following midline suboccipital approach. Histological examinations revealed high cellularity and mild atypia. Immunohistochemistry demonstrated positive stain for GFAP and Olig2 antibodies, and negative for p53 protein. The Ki67-labeling index was 6.8%. Pyrosequence analysis indicated IDH1/2 wild type (wt), BRAF V600 wt, H3F3A K27 wt, FGFR1 wt, and TERT wt. The final diagnosis was pediatric diffuse astrocytoma, WHO grade II, pons. GKS was performed one month after the biopsy. After transient worsening of the symptom, it disappeared gradually. The tumor is stable for three years with mild shrinkage of the size. DISCUSSION: Gross total resection (GTR) of pediatric low-grade, brainstem gliomas may result in a good prognosis. However, unlike pilocytic astrocytoma, diffuse astrocytoma is not easy to perform GTR without any complications. There are some reports regarding GKS for brainstem gliomas, which prove an increase in progression free survival rate. No marked tumor regression is achieved in our case, but tumor growth is well-controlled so far.CONCLUSIONGKS after biopsy can be a useful treatment option for pediatric low-grade brainstem gliomas.

Midline Suboccipital Subtonsillar Approach in Semisitting Position for Resection of Jugular Tubercle Meningioma: 2-Dimensional Operative Video.

We present a case of a large jugular tubercle meningioma that was removed through a midline suboccipital subtonsillar approach in semisitting position. The patient is a 49-year-old woman with chronic, medication-resistant cephalgias but devoid of any subjective focal neurological deficit. On magnetic resonance imaging (MRI), an extra-axial lesion, originating from the left jugular tubercle was discovered. There was significant obliteration of the peripontine cisternal space, and compression of the adjacent pontomedullary junction; the lesion also extended into the left jugular foramen.On physical exam, an absent gag reflex was noted on the left, as well as a moderate deviation of the uvula to the contralateral side (partial Vernet's syndrome).A gross-total resection was achieved, histopathology confirmed a World Health Organization (WHO) grade I angiomatous meningioma with a low-proliferation index. The patient was discharged home 4 days after surgery with intact function of the lower cranial nerves (CN) following immediate and complete resolution of the preexisting partial CNs IX and X deficits. At 2-year follow-up, there was no indication of intradural residual or recurrence.In summary, the midline suboccipital subtonsillar approach is a simple and effective tool with limited morbidity in the armamentarium for the microsurgical management of pathologies residing in the posterior cranial fossa or the craniocervical junction.Major limitations exist for lesions extending above the internal acoustic canal or those of fibrous consistence featuring widespread adhesion to the ventral brainstem or vascular encasement. Provided the necessary anesthesiological precautions and intraoperative procedures the semisitting position is safe and effective. The link to the video can be found at: https://youtu.be/bbVXagwhDCo .

Anatomic variations of the human falx cerebelli and its association with occipital venous sinuses

Purpose Human falx cerebelli is an important anatomical structure in regard to its relations with venous structures during infratentorial approach to reach cerebellar tumors, vascular malformations, traumatic hemorrhage and Chiari malformations. The present study aim to describe the different types of variations of the falx cerebelli, its morphological features and its association with occipital venous sinuses. Method In this study 49 dura mater was obtained from the Institution of Forensic Medicine. The length, width and the depth of the falx cerebelli were measured using a digital compass. The data obtained were statistically analyzed in relation to age and gender. The relations of the falx cerebelli with the occipital sinus was documented. Histological sections from the falx cerebelli were stained with Hematoxylin Eosin to evaluate the fine structure. Results Among the 49 falx cerebelli examined 36 (73.5%) were classified as normal. The average length, width and depth of the normal falx cerebelli was 3.7, 1.0 and 0.4 cm respectively. Of the 49 falx cerebelli in 1 (2%) case it was absent, in 5 cases (10.2%) duplicate, in 5 cases (10.2%) triplicate, in 1 (2%) case quadruplets and in 1 case (2%) it was five-folded. The proximal and the distal attachments of the falx cerebelli showed 3 types of variations; both attachments triangular, the proximal attachments triangular and the distal ramified and distal attachments triangular and the proximal attachments ramified. The drainage of the occipital sinus of falx cerebelli with variations were evaluated. The increased number of falx cerebelli highly corresponded with the increased number of occipital sinus. Conclusions The dural-venous variation in the posterior cranial fossa can be problematic in various diagnostic and operative procedures of this region. Neurosurgeons should be aware of such variations, as these could be potential sources of haemorrhage during the midline suboccipital and infratentorial approaches.