Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Frontotemporal and Orbitozygomatic Craniotomies.

Introduction Although many neuroanatomic atlases have been published, few have detailed complex cranial approaches and pertinent anatomic considerations in a stepwise fashion intended for rapid comprehension by neurosurgery students, residents, and fellows. Methods Five sides of formalin-fixed latex-injected specimens were dissected under microscopic magnification. The frontotemporal and orbitozygomatic approaches were performed by neurosurgical residents and fellows at different training levels with limited previous experience in anatomical dissection mentored by the senior authors (M.P.C. and M.J.L.). Meticulous surgical anatomic dissections were performed until sufficient visual and technical completion was attained, with parameters of effectively demonstrating key surgical steps for educational training purposes. Following the completion of dissection and three-dimensional photography, illustrative case examples were reviewed to demonstrate the relative benefits and optimal applications of each approach. Results The frontotemporal and orbitozygomatic approaches afford excellent access to anterior and middle skull base pathologies, as well as the exposure of the infratemporal fossa. Key considerations include head positioning, skin incision, scalp retraction, fat pad dissection and facial nerve protection, true or false MacCarty keyhole fashioning, sphenoid wing drilling and anterior clinoidectomy, completion of the craniotomy and accessory orbital osteotomy cuts, dural opening, and intradural neurovascular access. Conclusion The frontotemporal and orbitozygomatic approaches are core craniotomies that offer distinct advantages for complex cranial operations. Learning and internalizing their key steps and nuanced applications in a clinical context is critical for trainees of many levels. The orbitozygomatic craniotomy in particular is a versatile but challenging approach; operative-style laboratory dissection is an essential component of its mastery and one that will be powerfully enhanced by the current work.

A Cadaveric Feasibility Study of the Biportal Endoscopic Transfrontal Sinus Approach: A Minimally Invasive Approach to the Anterior Cranial Fossa.

BACKGROUND AND OBJECTIVES: The trans-sinus transglabellar and bifrontal approaches offer direct access to the anterior cranial fossa. However, these approaches present potential drawbacks. We propose the biportal endoscopic transfrontal sinus (BETS) approach, adapting endoscopic endonasal approach (EEA) techniques for minimally invasive access to the anterior fossa, reducing tissue manipulation, venous sacrifice, and brain retraction. METHODS: Six formalin specimens were used. BETS approach involves 2 incisions over the medial aspect of both eyebrows from the supraorbital notch to the medial end of the eyebrow. A unilateral pedicled pericranial flap is harvested. A craniotomy through the anterior table of the frontal sinus (FS) and a separate craniotomy through the posterior table are performed. Two variants of the approach (preservative vs cranialization) are described for opening and reconstruction of the FS based on the desired pathology to access. Bone flap replacement can be performed with titanium plates and filling of the external table defect with bone cement. RESULTS: Like in EEA, this approach provides access for endoscope and multiple working instruments to be used simultaneously. The approach allows wide access to the anterior cranial fossa, subfrontal, and interhemispheric corridors, all the way up to the suprachiasmatic corridor and through the lamina terminalis to the third ventricle. BETS provides direct access to the anterior fossa, minimizing the level of frontal lobe retraction and providing potentially less tissue disruption and improved cosmesis. Cerebrospinal fluid fistula risk remains one of the major concerns as the narrow corridor limits achieving a watertight closure which can be mitigated with a pedicled flap. Mucocele risk is minimized with full cranialization or reconstruction of the FS. CONCLUSION: The BETS approach is a minimally invasive approach that translates the concepts of EEA to the FS. It allows excellent access to the anterior cranial fossa structures with minimal frontal lobe retraction.

Photogrammetry scans for neuroanatomy education - a new multi-camera system: technical note.

Photogrammetry scans has directed attention to the development of advanced camera systems to improve the creation of three-dimensional (3D) models, especially for educational and medical-related purposes. This could be a potential cost-effective method for neuroanatomy education, especially when access to laboratory-based learning is limited. The aim of this study was to describe a new photogrammetry system based on a 5 Digital Single-Lens Reflex (DSLR) cameras setup to optimize accuracy of neuroanatomical 3D models. One formalin-fixed brain and specimen and one dry skull were used for dissections and scanning using the photogrammetry technique. After each dissection, the specimens were placed inside a new MedCreator® scanner (MedReality, Thyng, Chicago, IL) to be scanned with the final 3D model being displayed on SketchFab® (Epic, Cary, NC) and MedReality® platforms. The scanner consisted of 5 cameras arranged vertically facing the specimen, which was positioned on a platform in the center of the scanner. The new multi-camera system contains automated software packages, which allowed for quick rendering and creation of a high-quality 3D models. Following uploading the 3D models to the SketchFab® and MedReality® platforms for display, the models can be freely manipulated in various angles and magnifications in any devices free of charge for users. Therefore, photogrammetry scans with this new multi-camera system have the potential to enhance the accuracy and resolution of the 3D models, along with shortening creation time of the models. This system can serve as an important tool to optimize neuroanatomy education and ultimately, improve patient outcomes.

Full Recovery of Hearing After Resection of a Large Epidermoid Tumor at the Cerebellopontine Angle: 2-Dimensional Operative Video.

Epidermoid tumors are benign, slow-growing lesions, originating from misplaced ectodermal cells that become trapped during neural tube closure.1 The cerebellopontine angle (CPA) is the most common intracranial location for epidermoid tumors, accounting for approximately 60% of cases.2 Treatment of epidermoid tumors consists of surgical resection, with the goal of gross total resection.3 Here, we describe the case of a patient with a large epidermoid tumor at the CPA causing near-complete hearing loss, who remarkably experienced full recovery of hearing after resection of the tumor. The patient is a 37-year-old woman who presented to our clinic with a CPA tumor causing severe hearing loss consisting of class D hearing and a word recognition score of 5% on audiological examination. Radiographically, the tumor demonstrated significant mass effect on the right cranial nerves VII and VIII with prominent extension into the internal auditory canal. Given the patient's profound hearing loss, she consented to receive a right retrosigmoid craniotomy for resection of the lesion. Although cranial nerves VII and VIII were heavily invested in the tumor, we were able to systematically resect the lesion from the CPA and internal auditory canal, and achieve a gross total resection. Histological examination confirmed the diagnosis of an epidermoid tumor. Remarkably, the patient's audiogram at 3-month follow-up demonstrated complete recovery of hearing in her right ear with a word recognition score of 100% and normal hearing sensitivity across all tested frequencies.

Skull Base CSF Leaks: Potential Underlying Pathophysiology and Evaluation of Brain MR Imaging Findings Associated with Spontaneous Intracranial Hypotension.

BACKGROUND AND PURPOSE: Cerebrospinal fluid (CSF) leaks of the skull base and spine share a common process of CSF volume loss, and yet only the latter has been associated with spontaneous intracranial hypotension (SIH). Despite published claims that only spinal leaks cause SIH, no prior studies have evaluated brain MR imaging in patients with skull base leaks for findings associated with SIH such as dural enhancement. The purpose of our study was to use a validated brain MR imaging scoring system to evaluate skull base CSF leak patients for findings associated with SIH. MATERIALS AND METHODS: We included patients with confirmed skull base CSF leaks and contrast enhanced pre-operative brain MRI. The pre-operative MR images were reviewed for findings associated with SIH using the Bern score. Patient age, presenting symptoms and their duration, and leak site were also recorded. RESULTS: 31 patients with skull base CSF leaks were included. Mean Bern score was 0.9 (range 0-4, SD 1.1), and only 1 patient (3%) had dural enhancement. Mean age was 53 years (range 18-76). Mean symptom duration was 1.3 years, with 22 patients presenting within one year of symptom onset. 23 patients (74.2%) had intraoperative confirmation of leak from the middle cranial fossa, involving the temporal bone, while 7 (22.6%) had leaks from the anterior skull base. One patient, who had dural enhancement, had an infratentorial CSF leak along the petrous segment of the internal carotid artery. CONCLUSIONS: Our study provides further evidence that skull base and spinal CSF leaks represent distinct pathophysiologies and present with different brain MRI findings.ABBREVIATIONS: SIH = Spontaneous Intracranial Hypotension; IIH = Idiopathic Intracranial Hypertension.

3D Models as a Source for Neuroanatomy Education: A Stepwise White Matter Dissection Using 3D Images and Photogrammetry Scans.

White matter dissection (WMD) involves isolating bundles of myelinated axons in the brain and serves to gain insights into brain function and neural mechanisms underlying neurological disorders. While effective, cadaveric brain dissections pose certain challenges mainly due to availability of resources. Technological advancements, such as photogrammetry, have the potential to overcome these limitations by creating detailed three-dimensional (3D) models for immersive learning experiences in neuroanatomy. This study aimed to provide a detailed step-by-step WMD captured using two-dimensional (2D) images and 3D models (via photogrammetry) to serve as a comprehensive guide for studying white matter tracts of the brain. One formalin-fixed brain specimen was utilized to perform the WMD. The brain was divided in a sagittal plane and both cerebral hemispheres were stored in a freezer at -20 °C for 10 days, then thawed under running water at room temperature. Micro-instruments under an operating microscope were used to perform a systematic lateral-to-medial and medial-to-lateral dissection, while 2D images were captured and 3D models were created through photogrammetry during each stage of the dissection. Dissection was performed with comprehensive examination of the location, main landmarks, connections, and functions of the white matter tracts of the brain. Furthermore, high-quality 3D models of the dissections were created and housed on SketchFab®, allowing for accessible and free of charge viewing for educational and research purposes. Our comprehensive dissection and 3D models have the potential to increase understanding of the intricate white matter anatomy and could provide an accessible platform for the teaching of neuroanatomy.

Long-term outcome of primary clival chordomas: a single-center retrospective study with an emphasis on the timing of recurrences based on the primary treatment.

OBJECTIVE: This study aimed to provide data on extended outcomes in primary clival chordomas, focusing on progression-free survival (PFS) and overall survival (OS). METHODS: A retrospective single-center analysis was conducted on patients with clival chordoma treated between 1987 and 2022 using surgery, stereotactic radiosurgery, or proton radiation therapy (PRT). RESULTS: The study included 100 patients (median age 44 years, 51% male). Surgery was performed using the endoscopic endonasal approach in 71 patients (71%). Gross-total resection (GTR) or near-total resection (NTR) was attained in 39 patients (39%). Postoperatively, new cranial nerve deficits occurred in 7%, CSF leak in 4%, and meningitis in none of the patients. Radiation therapy was performed in 79 patients (79%), with PRT in 50 patients (50%) as the primary treatment. During the median follow-up period of 73 (interquartile range [IQR] 38-132) months, 41 recurrences (41%) and 31 deaths (31%) were confirmed. Patients with GTR/NTR had a median PFS of 41 (IQR 24-70) months. Patients with subtotal resection or biopsy had a median PFS of 38 (IQR 16-97) months. The median PFS of patients who received radiation therapy was 43 (IQR 26-86) months, while that of patients who did not receive radiation therapy was 18 (IQR 5-62) months. The Kaplan-Meier method showed that patients with GTR/NTR (p = 0.007) and those who received radiation therapy (p < 0.001) had longer PFS than their counterparts. The PFS rates following primary treatment at 5, 10, 15, and 20 years were 51%, 25%, 17%, and 7%, respectively. The OS rates at the same intervals were 84%, 60%, 42%, and 34%, respectively. Multivariate Cox regression analysis showed that age < 44 years (p = 0.02), greater extent of resection (EOR; p = 0.03), and radiation therapy (p < 0.001) were associated with lower recurrence rates. Another multivariate analysis showed that age < 44 years (p = 0.01), greater EOR (p = 0.04), and freedom from recurrence (p = 0.02) were associated with lower mortality rates. Regarding pathology data, brachyury was positive in 98%, pan-cytokeratin in 93%, epithelial membrane antigen in 85%, and S100 in 74%. No immunohistochemical markers were associated with recurrence. CONCLUSIONS: In this study, younger age, maximal safe resection, and radiation therapy were important factors for longer PFS in patients with primary clival chordomas. Preventing recurrences played a crucial role in achieving longer OS.

Repeat Radiosurgery for Sporadic Vestibular Schwannoma After Primary Radiosurgical Failure: An International Multi-institutional Investigation.

OBJECTIVE: To describe outcomes of patients with sporadic vestibular schwannoma (VS) who underwent repeat stereotactic radiosurgery (SRS) after primary SRS failure. STUDY DESIGN: Multi-institutional historical cohort study. SETTING: Five tertiary care referral centers. PATIENTS: Adults ≥18 years old with sporadic VS. INTERVENTION: Primary and repeat treatment with SRS. MAIN OUTCOME MEASURE: Microsurgery-free survival after repeat SRS. RESULTS: Across institutions, 32 patients underwent repeat SRS after primary SRS. Most patients (74%) had tumors with cerebellopontine angle extension at primary SRS (median size, 13.5 mm [interquartile range, 7.5-18.8] mm). After primary SRS, patients underwent repeat SRS at a median of 4.8 years (interquartile range, 3.2-5.7 yr). For treatment modality, 30 (94%) patients received gamma knife for primary treatment and 31 (97%) patients received gamma knife as their repeat treatment. Median tumor volume increased from 0.970 cm3 at primary SRS to 2.200 cm3 at repeat SRS. Facial nerve function worsened in two patients after primary SRS and in two patients after repeat SRS. There were no instances of intracranial complications after repeat SRS. Microsurgery-free survival rates (95% confidence interval; number still at risk) at 1, 3, and 5 years after repeat SRS were 97% (90-100%, 24), 84% (71-100%, 13), and 68% (48-96%, 6), respectively. There was one occurrence of malignancy diagnosed after repeat radiosurgery. CONCLUSION: Overall, repeat SRS for sporadic VS has comparable risk profile, but lower rates of tumor control, compared with primary SRS.

Radiation-Associated Vestibular Schwannomas: Case Series and Literature Review.

OBJECTIVES: Radiation treatment, particularly at a young age, creates theoretical risk for long-term adverse radiation effects, including the development of malignancy. The literature is sparse on radiation-induced vestibular schwannomas (VSs). METHODS: A retrospective review was performed for cases of suspected radiation-induced VS at 2 high-volume centers. Only cases where radiation included coverage of the posterior fossa were included with those diagnosed within 3 years of radiation treatment being excluded. Patient and tumor characteristics were collected. A systematic literature review was also performed for any previously published series on radiation-induced VS. RESULTS: Eight cases of radiation-induced VS were identified with a median follow-up 125 months (range 7-131). The median age at incident radiation was 15 years (range 2-46). The median age at VS diagnosis was 57 years (range 26-83) with median interval from radiation to diagnosis of 51-years (range 15-66). The median tumor size was 6 mm (range 3-21). Two patients underwent surgical resection. Lesions were described as soft and highly vascular, with medium to high adherence to the facial nerve. Five articles with a total of 52 patients were identified, median age at VS diagnosis was 42-years (range 23-73) with a median interval from radiation to diagnosis of 19 years (range 15-23). CONCLUSIONS: The development of VS following radiation exposure appears rare and our understanding of the condition remains incomplete. Further studies are required to determine the best management of these patients and determine whether there is a causative relationship between radiation exposure and the development of VS.

Surgical Anatomy of the Retrosigmoid Approach With Transtentorial Extension: Protecting the 4th Cranial Nerve.

BACKGROUND AND OBJECTIVES: The retrosigmoid approach with transtentorial extension (RTA) allows us to address posterior cranial fossa pathologies that extend through the tentorium into the supratentorial space. Incision of the tentorium cerebelli is challenging, especially for the risk of injury of the cranial nerve (CN) IV. We describe a tentorial incision technique and relevant anatomic landmarks. METHODS: The RTA was performed stepwise on 5 formalin-fixed (10 sides), latex-injected cadaver heads. The porus trigeminus's midpoint, the lateral border of the suprameatal tubercle (SMT)'s base, and cerebellopontine fissure were assessed as anatomic landmarks for the CN IV tentorial entry point, and relative measurements were collected. A clinical case was presented. RESULTS: The tentorial opening was described in 4 different incisions. The first is curved and starts in the posterior aspect of the tentorium. It has 2 limbs: a medial one directed toward the tentorium's free edge and a lateral one that extends toward the superior petrosal sinus (SPS). The second incision turns inferiorly, medially, and parallel to the SPS down to the SMT. At that level, the second incision turns perpendicular toward the tentorium's free edge and ends 1 cm from it. The third incision proceeds posteriorly, parallel to the free edge. At the cerebellopontine fissure, the incision can turn toward and cut the tentorium-free edge (fourth incision). On average, the CN IV tentorial entry point was 12.7 mm anterior to the SMT base's lateral border and 20.2 mm anterior to the cerebellopontine fissure. It was located approximately in the same coronal plane as the porus trigeminus's midpoint, on average 1.9 mm anterior. CONCLUSION: The SMT and the cerebellopontine fissure are consistently located posterior to the CN IV tentorial entry point. They can be used as surgical landmarks for RTA, reducing the risk of injury to the CN IV.

Treatment modalities and outcomes of granular cell tumors and spindle cell oncocytomas of the pituitary gland: an analysis of two national cancer databases.

BACKGROUND: Spindle cell oncocytomas (SCO) and granular cell tumors (GCT) are rare primary pituitary neoplasms; the optimal treatment paradigms for these lesions are unknown and largely unexplored. Thus, using national registries, we analyze the epidemiology, management patterns, and surgical outcomes of SCOs and GCTs. METHODS: The National Cancer Database (NCDB; years 2003-2017) and the Surveillance, Epidemiology, and End Results Program (SEER; years 2004-2018) were queried for patients with pituitary SCOs or GCTs. Incidence, extent of surgical resection, and rate of postoperative radiation use for subtotally resected lesions comprised the primary outcomes of interest. All-cause mortality was also analyzed via time-to-event Kaplan-Meier curves. RESULTS: SCOs and GCTs have an annual incidence of 0.017 and 0.023 per 1,000,000, respectively. They comprise 0.1% of the benign pituitary tumors registered in NCDB. A total of 112,241 benign pituitary tumors were identified in NCDB during the study period, of which 83 (0.07%) were SCOs and 59 (0.05%) were GCTs. Median age at diagnosis was 55 years, 44% were females, and median maximal tumor diameter at presentation was 2.1 cm. Gross total resection was achieved in 54% patients. Ten patients (7%) had postoperative radiation. Comparing patients with GCTs versus SCOs, the former were more likely to be younger at diagnosis (48.0 vs. 59.0, respectively; p < 0.01) and female (59% vs. 34%, p = 0.01). GCTs and SCOs did not differ in terms of size at diagnoses (median maximal diameter: 1.9 cm vs. 2.2 cm, respectively; p = 0.59) or gross total resection rates (62% vs. 49%, p = 0.32). After matching SCOs and GCTs with pituitary adenomas on age, sex, and tumor size, the former were less likely to undergo gross total resection (53% vs. 72%; p = 0.03). Patients with SCOs and GCTs had a shorter overall survival when compared to patients with pituitary adenomas (p < 0.01) and a higher rate of thirty-day mortality (3.1% vs 0.0%; p = 0.013). CONCLUSION: SCOs and GCTs are rare pituitary tumors, and their management entails particular challenges. Gross total resection is often not possible, and adjuvant radiation might be employed following subtotal resection.

Predicting the Need for Occipitocervical Fusion for Patients with Lower Clival Chordoma: A Single-Center Retrospective Study.

OBJECTIVE: To assess the impact of tumor extension into the occipital condyle (OC) in lower clival chordoma management and the need for occipito-cervical fusion (OCF). METHODS: A retrospective analysis was conducted on 35 patients with lower clival chordoma. The preoperative area of the intact OCs, Hounsfield units, and the integrity of the apical ligament and the tectorial membrane were assessed using preoperative imaging. RESULTS: Seven (20%) patients were in the OCF group. The OCF group exhibited a higher prevalence of preoperative pain in the neck or head (P = 0.006), ligament absence (P = 0.022), and increased propensity for postoperative wound issues (P = 0.022) than the non-OCF group. The OCF group had less intact OCs (P < 0.001) and higher spinal instability neoplastic score (P = 0.002) than the non-OCF group. All patients with intact OCs < 60% underwent OCF, and those with OCs ≥ 70% were treated without OCF. Those with OCs between 60% and 69% underwent OCF if the ligaments were eroded, and did not undergo OCF if the ligaments were intact. Treatment strategies varied, with endoscopic endonasal approach alone being common. Radiation therapy was administered to 89% of patients. All 3 patients treated with OCF after tumor resection had wound issues; none treated with OCF before resection had wound issues. None developed atlanto-occipital instability. Survival rates did not significantly differ between groups. CONCLUSIONS: In the absence of mobility-related neck pain, patients with lower clival chordoma and intact OC ≥ 60%, intact apical ligament, and intact tectorial membrane, may not require OCF.

Extraocular muscle electromyographic recordings for intraoperative monitoring of cranial nerves III, IV, and VI: a single-center experience with intraorbital electrodes.

OBJECTIVE: The objective of this study was to describe the quantitative features of intraoperative electromyographic recordings obtained from cranial nerve III, IV, and VI neuromonitoring using 25-mm intraorbital electrodes, in the larger context of demonstrating the practicality of this technique during neurosurgical cases. METHODS: A 25-mm-long shaft-insulated intraorbital needle electrode is routinely used at the authors' institution for extraocular muscle (EOM) electromyographic monitoring of the inferior rectus, superior oblique, and/or lateral rectus muscles when their function is at risk. Cases monitored between January 1, 2021, and December 31, 2022, were reviewed for patient demographics, tumor location and pathology, EOMs monitored, pre- and postoperative examination, and complications from electrode placement. Compound muscle action potentials on triggered electromyography, as well as neurotonic discharges on free-run electromyography, were described quantitatively. RESULTS: There were 141 cases in 139 patients reviewed during the 24-month time span, with 278 EOMs monitored (inferior rectus/superior oblique/lateral rectus muscles 68/68/142). Triggered electromyography yielded biphasic or triphasic compound muscle action potentials from EOMs with a mean onset latency of 1.51 msec (range 0.94-3.22 msec), mean maximal peak-to-trough amplitude of 1073.93 µV (range 76.75-7796.29 µV), and high specificity for the channel in nearly all cases. Neurotonic discharges were recorded in 30 of the 278 EOMs (with all 3 muscles represented) and associated with a greater incidence of new or worsened ophthalmoparesis (OR 4.62, 95% CI 1.3-16.4). There were 2 cases of small periorbital ecchymosis attributed to needle placement; additionally, 1 case of needle-related intraorbital hematoma occurred after the review period. CONCLUSIONS: The 25-mm shaft-insulated intraorbital electrode facilitates robust and consistent electromyographic recordings of EOMs that are advantageous over existing techniques. Combined with the relative ease of needle placement and low rate of complications, the technique is practical for neuromonitoring during craniotomies.

Patterns of recurrence and disease progression in patients with positive-margin olfactory neuroblastoma following primary resection.

OBJECTIVE: Olfactory neuroblastoma (ONB) is a rare, malignant tumor of the sinonasal tract that arises from olfactory epithelium. Although surgery is the preferred first-line treatment, tumor involvement of adjacent structures may preclude the ability to achieve negative margins during initial resection. Herein, the authors examine the oncological outcomes of patients with positive margins after primary resection of ONB, with the aim of determining predictors of disease progression and patterns of recurrence. METHODS: The authors performed an institutional review of 25 patients with positive-margin ONB after resection. Cox survival analyses were used to determine any statistically significant predictors of worse progression-free survival (PFS) and overall survival (OS). RESULTS: A total of 93 patients who were diagnosed with ONB were identified, of whom 25 patients had positive margins following their primary resection. Eleven (44%) had a delayed finding of positive margins that were initially negative in the operating room but returned as positive on final pathology. Four patients had subtotal resection (STR), whereas the remaining patients underwent gross-total resection. Twenty-four patients received adjuvant radiotherapy (96%), and 15 additionally received adjuvant chemotherapy (60%). Fourteen patients (56%) experienced recurrence/progression at a median time of 35 months following resection (IQR 19-70 months). Local recurrence occurred in 10 patients (40%), regional in 9 (36%), and distant metastasis in 2 (8%). In Cox survival analyses, the 5-year PFS and OS were 55.1% and 79.2%, respectively. Kadish stage D was predictive of worse PFS in univariate (hazard ratio [HR] 15.67, 95% CI 3.38-72.61, p < 0.001) and multivariate (HR 15.46, 95% CI 1.45-164.91, p = 0.023) analyses. Hyams grade, adjuvant chemotherapy, and primary radiotherapy were not associated with PFS. Furthermore, Kadish stage D and STR were predictive of worse OS in univariate analysis (HR 12.64, 95% CI 2.03-78.86, p = 0.007; HR 7.31, 95% CI 1.45-36.84, p = 0.016; respectively). However, local and regional recurrence was not associated with worse OS. CONCLUSIONS: Approximately half of patients with positive-margin ONB may experience disease recurrence. Patients with an advanced disease stage (Kadish D) may have a higher likelihood of developing recurrence/progression. Furthermore, patients with tumor burden following resection (STR and Kadish D) may have worse OS. However, in positive-margin ONB with no gross disease following initial resection, the presence of disease recurrence does not significantly alter survival when receiving salvage therapy.

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.

NAB2::STAT6 fusions and genome-wide DNA methylation profiling: Predictors of patient outcomes in meningeal solitary fibrous tumors.

Meningeal solitary fibrous tumors (SFT) are rare and have a high frequency of local recurrence and distant metastasis. In a cohort of 126 patients (57 female, 69 male; mean age at surgery 53.0 years) with pathologically confirmed meningeal SFTs with extended clinical follow-up (median 9.9 years; range 15 days-43 years), we performed extensive molecular characterization including genome-wide DNA methylation profiling (n = 80) and targeted TERT promoter mutation testing (n = 98). Associations were examined with NAB2::STAT6 fusion status (n = 101 cases; 51 = ex5-7::ex16-17, 26 = ex4::ex2-3; 12 = ex2-3::exANY/other and 12 = no fusion) and placed in the context of 2021 Central Nervous System (CNS) WHO grade. NAB2::STAT6 fusion breakpoints (fusion type) were significantly associated with metastasis-free survival (MFS) (p = 0.03) and, on multivariate analysis, disease-specific survival (DSS) when adjusting for CNS WHO grade (p = 0.03). DNA methylation profiling revealed three distinct clusters: Cluster 1 (n = 38), Cluster 2 (n = 22), and Cluster 3 (n = 20). Methylation clusters were significantly associated with fusion type (p < 0.001), with Cluster 2 harboring ex4::ex2-3 fusion in 16 (of 20; 80.0%), nearly all TERT promoter mutations (7 of 8; 87.5%), and predominantly an "SFT" histologic phenotype (15 of 22; 68.2%). Clusters 1 and 3 were less distinct, both dominated by tumors having ex5-7::ex16-17 fusion (respectively, 25 of 33; 75.8%, and 12 of 18; 66.7%) and with variable histological phenotypes. Methylation clusters were significantly associated with MFS (p = 0.027), but not overall survival (OS). In summary, NAB2::STAT6 fusion type was significantly associated with MFS and DSS, suggesting that tumors with an ex5::ex16-17 fusion may have inferior patient outcomes. Methylation clusters were significantly associated with fusion type, TERT promoter mutation status, histologic phenotype, and MFS.

Imaging Findings Post-Stereotactic Radiosurgery for Vestibular Schwannoma: A Primer for the Radiologist.

Noninvasive tumor control of vestibular schwannomas through stereotactic radiosurgery allows high rates of long-term tumor control and has been used primarily for small- and medium-sized vestibular schwannomas. The posttreatment imaging appearance of the tumor, temporal patterns of growth and treatment response, as well as extratumoral complications can often be both subtle or confusing and should be appropriately recognized. Herein, the authors present an imaging-based review of expected changes as well as associated complications related to radiosurgery for vestibular schwannomas.

Coordinated Same- or Next-Day Radiosurgery and Cochlear Implantation for Vestibular Schwannoma.

OBJECTIVE: To describe the experience and results from coordinated and closely scheduled radiosurgery and cochlear implantation (CI) in a vestibular schwannoma (VS) cohort. PATIENTS: Patients with VS who underwent radiosurgery followed by CI on the same or next day. INTERVENTIONS: Interventions included sequential radiosurgery and CI. MAIN OUTCOME MEASURES: Tumor control defined by tumor growth on posttreatment surveillance and audiometric outcomes including consonant-nucleus-consonant words and AzBio sentences in quiet. RESULTS: In total, six patients were identified that met the inclusion criteria, with an age range of 38 to 69 years and tumor sizes ranging from 2.0 to 16.3 mm. All patients successfully underwent radiosurgery and CI on the same or immediately successive day. Postoperatively, all patients obtained open-set speech recognition. Consonant-nucleus-consonant word scores ranged from 40 to 88% correct, and AzBio scores ranged from 44 to 94% correct. During posttreatment magnetic resonance imaging surveillance, which ranged from 12 to 68 months, all tumors were noted to be adequately visualized, and no tumor progression was noted. CONCLUSION: Coordinated radiosurgery and CI can be safely performed in patients with VS on the same or next day, serving to decrease burden on patients and increase access to this vital rehabilitative strategy.

Salvage Microsurgery Following Failed Primary Radiosurgery in Sporadic Vestibular Schwannoma.

Importance: Management of sporadic vestibular schwannoma with radiosurgery is becoming increasingly common globally; however, limited data currently characterize patient outcomes in the setting of microsurgical salvage for radiosurgical failure. Objective: To describe the clinical outcomes of salvage microsurgery following failed primary stereotactic radiosurgery (SRS) or fractionated stereotactic radiotherapy (FSRT) among patients with sporadic vestibular schwannoma. Design, Setting, and Participants: This was a cohort study of adults (≥18 years old) with sporadic vestibular schwannoma who underwent salvage microsurgery following failed primary SRS/FSRT in 7 vestibular schwannoma treatment centers across the US and Norway. Data collection was performed between July 2022 and January 2023, with data analysis performed between January and July 2023. Exposure: Salvage microsurgical tumor resection. Main Outcomes and Measures: Composite outcome of undergoing less than gross total resection (GTR) or experiencing long-term facial paresis. Results: Among 126 patients, the median (IQR) age at time of salvage microsurgery was 62 (53-70) years, 69 (55%) were female, and 113 of 117 (97%) had tumors that extended into the cerebellopontine angle at time of salvage. Of 125 patients, 96 (76%) underwent primary gamma knife SRS, while 24 (19%) underwent linear accelerator-based SRS; the remaining patients underwent FSRT using other modalities. Postoperative cerebrospinal fluid leak was seen in 15 of 126 patients (12%), hydrocephalus in 8 (6%), symptomatic stroke in 7 (6%), and meningitis in 2 (2%). Each 1-mm increase in cerebellopontine angle tumor size was associated with a 13% increased likelihood of foregoing GTR (64 of 102 patients [63%]) or long-term postoperative House-Brackmann grade higher than I (48 of 102 patients [47%]) (odds ratio, 1.13; 95% CI, 1.04-1.23). Following salvage microsurgery, tumor growth-free survival rates at 1, 3, and 5 years were 97% (95% CI, 94%-100%), 93% (95% CI, 87%-99%), and 91% (95% CI, 84%-98%), respectively. Conclusions: In this cohort study, more than half of patients who received salvage microsurgery following primary SRS/FSRT underwent less than GTR or experienced some degree of facial paresis long term. These data suggest that the cumulative risk of developing facial paresis following primary SRS/FSRT by the end of the patient's journey with treatment approximates 2.5% to 7.5% when using published primary SRS/FSRT long-term tumor control rates.