Link, Michael J.

Objectives This video was aimed to describe the surgical indications, relevant anatomy, and surgical steps of retrosigmoid approach for resection of a large cystic vestibular schwannoma (VS). Design The operative steps are described in a surgical instructional video. Setting The surgery took place at a tertiary skull base referral center. Participant Patient is a 62-year-old man who reported with right sided profound hearing loss with no word recognition, progressive dizziness and tinnitus, excruciating burning pain in the V2 distribution of right trigeminal nerve, wide-based gait, and a right cerebellopontine angle (CPA) cystic VS measuring 3.3 cm. Main Outcome Measures The large cystic VS was resected through retrosigmoid approach. Results The surgery resulted in removal of the large cystic VS with initial delayed facial weakness that completely resolved (House Brackmann grade 1) by 3 month follow-up. The patient had no other postoperative complications and is convalescing well from the procedure. Conclusion Cystic VS presents some unique challenges compared with their solid counterparts. The cystic tumor capsule may be very adherent to the adjacent structures, and distinguishing thin cyst walls from the arachnoid of the CPA, can be quite challenging. The retrosigmoid approach provides adequate surgical exposure for VS tumor resection.The link to the video can be found at: https://youtu.be/sFNvRWG465Q.

Glioblastoma (GBM) of the internal auditory canal (IAC) is exceedingly rare, with only 3 prior cases reported in the literature. The authors present the fourth case of cerebellopontine angle (CPA) and IAC GBM, and the first in which the lesion mimicked a vestibular schwannoma (VS) early in its natural history. A 55-year-old man presented with tinnitus, hearing loss, and imbalance. MRI identified a left IAC/CPA lesion measuring 8 mm, most consistent with a benign VS. Over the subsequent 4 months he developed facial weakness. The tumor grew remarkably to 24 mm and surgery was recommended; the main preoperative diagnosis was malignant peripheral nerve sheath tumor (MPNST). Resection proceeded via a translabyrinthine approach with resection of cranial nerves VII and VIII, followed by facial-hypoglossal nerve anastomosis. Intraoperative frozen section suggested malignant spindle cell neoplasm, but final histopathological and molecular testing confirmed the lesion to be a GBM. The authors report the first case in which absence of any brainstem interface effectively excluded a primary parenchymal tumor, in particular GBM, from the differential diagnosis. Given the dramatic differences in treatment and prognoses between malignant glioma and MPNST, this case emphasizes the importance of surgical intervention on an aggressively growing lesion, which provides both the best probability of local control and the critical tissue diagnosis.

Background: The Acoustic Neuroma Association (ANA) is a national, nonprofit organization, focused on the education and support of patients with vestibular schwannoma (VS). The aim of the present study is to characterize the profile of ANA survey respondents and compare them with non-ANA patients evaluated at a single tertiary academic referral center to investigate the potential influence of selection bias. Methods: A prospectively maintained VS quality-of-life (QOL) database, comprised of patients evaluated at the authors’ center and members of the ANA, was queried. Demographic variables, patient-reported symptoms and tumor characteristics, as well as patient-reported outcome scores were captured. Health-related QOL was evaluated using the disease-specific Penn Acoustic Neuroma QOL (PANQOL) questionnaire. Multivariable regression models were fitted for PANQOL domain and total scores as well as satisfaction with treatment adjusting for baseline demographics, symptoms, and PANQOL scores. Results: A total of 1,060 patients (802 [76%] ANA respondents) were analyzed. Overall, ANA patients were slightly younger (mean age: 59 vs 60 yr, p = 0.145), more likely to be women (72 vs 55%, p < 0.001), and had a larger tumor size (overall p < 0.001). Furthermore, a significantly higher proportion of ANA patients were more likely to undergo microsurgery (57 vs 21%) or radiation (21 vs 8%) and less likely to be managed with observation (16 vs 65%, overall p < 0.001). A significantly higher proportion of ANA patients reported hearing loss (95 vs 88%, p < 0.001), tinnitus (80 vs 73%, p = 0.034), dizziness (78 vs 64%, p < 0.001), headache (56 vs 45% p = 0.003), and facial paralysis (37 vs 12%, p < 0.001). On multivariable analysis, ANA respondents exhibited significantly lower PANQOL scores for hearing (OR: 0.47, 95% CI: 0.35–0.64, p < 0.001), balance (OR: 0.51, 95% CI: 0.38–0.70, p < 0.001), pain (OR: 0.63, 95% CI: 0.46–0.86, p = 0.004), facial function (OR: 0.58, 95% CI: 0.42–0.80, p = 0.001), energy (OR: 0.44, 95% CI: 0.32–0.59, p < 0.001), anxiety (OR: 0.54, 95% CI: 0.40–0.74, p < 0.001), general (OR: 0.72, 95% CI: 0.53–0.98, p = 0.03), and total QOL (OR: 0.40, 95% CI: 0.30–0.55, p < 0.001). No statistically significant difference was seen with regard to treatment satisfaction. To determine the true clinical relevance of these differences, the two groups were compared using the minimal clinically important difference (MCID) for each domain. MCID is defined as the smallest difference in score in the domain of interest that patients perceive as important, either beneficial or harmful. The domains for hearing, balance, energy, anxiety, and total QOL reached their respective MCID thresholds, indicating that the ANA cohort has QOL scores that are clinically, perceptually worse for these domains compared to the non-ANA group. Conclusion: These data help delineate some of the inherent limitations and biases associated with survey studies incorporating data from national patient support organizations. The population profile of ANA survey respondents likely differs significantly from the greater population of patients with VS that may be encountered at a tertiary referral center.

Abstract Selected upper cerebellopontine angle (CPA)/petroclival region lesions can be visualized and resected through a middle fossa approach with anterior petrosectomy. This approach is particularly well suited for tumors that extend from the CPA into Meckel's cave or the middle cranial fossa. We present the case of a 55-yr-old man who presented with sudden left-sided hearing loss, with complete recovery after medical treatment. MRI demonstrated a left 1.8 cm contrast-enhancing upper CPA lesion with extension into Meckel's cave most consistent with a trigeminal schwannoma. The patient initially opted for observation. MRI 11 mo later showed notable enlargement in the tumor, and the patient started to experience left-sided neuralgic face pain. The decision was made to perform surgery. Documented and verified informed consent was obtained A step-by-step surgical video with surgical anatomy images highlights the 5 steps followed by the authors to perform an anterior petrosectomy. The dura mater was opened parallel to the superior petrosal sinus both in the infratentorial and supratentorial spaces in order to clip and coagulate the superior petrosal sinus and divide the tentorium. The lesion was fully visualized and the trigeminal nerve was clearly identified displaced inferiorly but not splayed by the tumor, making the diagnosis of trigeminal schwannoma unlikely. The lesion was debulked and dissected off the brainstem as well as the trigeminal nerve with the final view of intact nerve fascicles entering the posterior aspect of Meckel's cave. Pathology returned as a WHO grade 1 meningioma. The patient recovered well with only mild facial hypesthesia and complete tumor resection on follow-up imaging.

OBJECTIVEMiddle fossa surgery is challenging, and reliable surgical landmarks are essential to perform accurate and safe surgery. Although many descriptions of the middle fossa components have been published, a clinically practical description of this very complex anatomical region is lacking. Small structure arrangements in this area are often not well visualized or accurately demarcated with neuronavigation systems. The objective is to describe a “roadmap” of key surgical reference points and landmarks during middle fossa surgery to help the surgeon predict where critical structures will be located.METHODSThe authors studied 40 dry skulls (80 sides) obtained from the anatomical board at their institution. Measurements of anatomical structures in the middle fossa were made with a digital caliper and a protractor, taking as reference the middle point of the external auditory canal (MEAC). The results were statistically analyzed.RESULTSThe petrous part of the temporal bone was found at a mean of 16 mm anterior and 24 mm posterior to the MEAC. In 87% and 99% of the sides, the foramen ovale and foramen spinosum, respectively, were encountered deep to the zygomatic root. The posterior aspect of the greater superficial petrosal nerve (GSPN) groove was a mean of 6 mm anterior and 25 mm medial to the MEAC, nearly parallel to the petrous ridge. The main axis of the IAC projected to the root of the zygoma in all cases. The internal auditory canal (IAC) porus was found 5.5 mm lateral and 4.5 mm deep to the lateral aspect of the trigeminal impression along the petrous ridge (mean measurement values). A projection from this point to the middle aspect of the root of the zygoma, being posterior to the GSPN groove, could estimate the orientation of the IAC.CONCLUSIONSIn middle fossa approaches, the external acoustic canal is a reliable reference before skin incision, whereas the zygomatic root becomes important after the skin incision. Deep structures can be related to these 2 anatomical structures. An easy method to predict the location of the IAC in surgery is described. Careful study of the preoperative imaging is essential to adapt this knowledge to the individual anatomy of the patient.

Introduction Optimal management of vestibular schwannoma (VS) demands involvement of an experienced multidisciplinary team. As the number of training programs in neurotology and skull base neurosurgery continues to rise, ensuring that trainees are capable of evidence-based decision-making and treatment, whether microsurgical or radiosurgical, is of paramount importance. The purpose of this study is to characterize the landscape of neurotologic and neurosurgical fellowship training programs in North America, with special reference to VS management. Methods A 64-item web-based survey assessing VS practice trends was devised by members of the North American Skull Base Society (NASBS) Research Task Force and distributed electronically to NASBS membership via SurveyMonkey as a cross-sectional study. Participation was entirely voluntary and there was no remuneration for survey completion. The survey link was active from November 29 to December 14, 2016. Results Of 719 members of the NASBS who were emailed a survey link, a total of 57 were returned (8%) completed surveys. Of all respondents, 51 (89%) claimed to have formal training in skull base neurosurgery or neurotology. Thirty-three respondents (65%) were skull base neurosurgeons while the remainder were neurotologists (n = 18; 35%). Institutions with fellowship programs tended to have a higher surgical, radiosurgical, and overall case volume than those with a residency program alone. However, 20% of respondents at institutions with fellowship programs reported evaluating less than 50 new diagnoses of VS per year and 12% reported a surgical case volume of less than 10 cases per year. Conclusion As the number of skull base training programs expands, it is our duty to ensure that trainees gain sufficient experience to enter independent practice with the ability to exercise informed decision-making and safely perform VS surgery and radiosurgery. In the current training climate, implementing multidisciplinary care models, formalized training requirements, and emerging surgical simulators will support the development of minimum proficiencies in VS care.

Objectives Although vestibular schwannomas (VS) are known to cause cranial nerve deficits, cerebellar symptoms, and hydrocephalus, the role of these symptoms as the key driver of presentation from the patient's perspective has not been described. Our objective was to survey a large, retrospective VS cohort to document the patient-reported principal initial symptom, and self-reported tumor size, and to study trends in VS patient presentation. Methods Patients diagnosed with VS at our tertiary referral center and belonging to the Acoustic Neuroma Association (ANA) answered a questionnaire between 2015 and 2017. Demographic data, self-reported tumor size, and symptomatology were analyzed. Results 1,304 patients completed the questionnaire. Tumors were diagnosed from 1966 to 2017 at a mean 51.8 years (range: 8–86 years); 66% were female, and 1.1% had confirmed neurofibromatosis type 2 (NF2). Tumor size was reported using a 6-point scale: 0 to 1 cm (22.9%), 1 to 2 cm (28.7%), 2 to 3 cm (20.5%), 3 to 4 cm (10%), greater than 4 cm (7.2%), and unknown (10.6%). Hearing loss was the most common symptom that led to diagnosis (51.5%), followed by dizziness (17%), tinnitus (11.2%), and incidental diagnosis (10.2%); a fraction that has increased significantly in the last decade (p = 0.022). Larger tumors and NF2 were significantly associated with young age (p < 0.001). Conclusion Our large-scale questionnaire-driven review of 1,304 patients confirms that VS presentations are stereotypical, with most individuals recalling hearing loss, dizziness, or tinnitus as their chief complaint. Many tumors were incidentally diagnosed; an expanding population, attributable to increased access to magnetic resonance imaging (MRI). Large tumors were significantly more prevalent among younger patients at diagnosis, excluding NF2 patients, suggesting a more aggressive tumor biology that remains incompletely understood.

Introduction Although numerous anatomical and operative atlases have been published, those that have focused on the skull base either have provided views that are quite difficult to achieve in the operating room to better depict surgical anatomy or are written at the level of an audience with considerable knowledge and experience. Methods Five sides of three formalin-fixed latex-injected specimens were dissected under microscopic magnification. A posterior petrosectomy approach was performed by three neurosurgical residents at different training levels with limited previous experience in anatomical dissection mentored by the senior authors (C. L. W. D. and M. J. L.) and a clinical skull base fellow with additional anatomical dissection experience (M. P. C.). Anatomical dissections were performed until the expected level of dissection quality was achieved to demonstrate each important step of the surgical approach that would be understandable to all trainees of all levels. Following dissection education, representative case applications were reviewed. Results The posterior petrosectomy (also known as presigmoid retrolabyrinthine approach) affords excellent access to cranial nerves III to XI and a diverse array of pathologies. Key steps include positioning and skin incision, scalp and muscle flaps, burr holes, craniotomy flap elevation, superficial mastoidectomy, otic capsule exposure and presigmoid dura decompression, primary presigmoid durotomy, inferior temporal durotomy, superior petrosal sinus ligation, tentorium sectioning, and final exposure. Conclusion The posterior petrosectomy is a challenging approach; thorough operative-style laboratory dissection is essential to provide trainees with a suitable guide. We describe a comprehensive approach to learning this technique, intended to be understandable and usable by a resident audience.

Objective: To evaluate quality-of-life (QOL) in patients with sporadic vestibular schwannoma (VS) with particular focus on those recently diagnosed. Study Design: Cross-sectional survey, Penn Acoustic Neuroma Quality of Life (PANQOL) instrument. Setting: Acoustic Neuroma Association and a single tertiary referral center. Patients: Patients with sporadic VS. Main Outcome Measures: Domain-specific and total PANQOL scores comparing treatment modalities after adjusting for baseline covariates of interest. Results: Among all 1,288 respondents there were 229 (18%) who were recently diagnosed and had not yet selected a treatment modality, 303 (24%) who were observed, 185 (14%) who underwent radiosurgery alone, 507 (39%) who underwent microsurgery alone, and 64 (5%) who underwent radiosurgery and microsurgery. After adjusting for covariates of interest, total PANQOL scores were highest for the observation cohort (65; 95% CI 62–68), lowest for patients treated with multimodality therapy (56; 51–61) and those recently diagnosed (58; 55–62), and intermediate for those who received microsurgery alone (60; 58–62) and radiosurgery alone (61; 57–64) (global comparison, p = 0.001). When comparing groups that received single-modality therapy, there were no statistically significant differences in total PANQOL scores at short (0–5 yr), intermediate (6–10 yr), or long-term (≥11 yr) follow-up after adjusting for baseline covariates (all, p > 0.05). Conclusion: A new diagnosis of VS frequently imparts significant anxiety on the patient and leads to a temporary reduction in QOL. Notably, anxiety domain QOL scores among patients with newly diagnosed VS are poorer than patients who have observed their tumor for 6 months or longer. When feasible, an initial period of observation may afford patients valuable time to reconcile with the new diagnosis, to learn more about treatment options, and to discover whether there is tumor growth. In turn, this valuable information can be used to inform sound decision-making regarding tumor management.

Introduction Large and even moderate sized, extra-axial cerebellopontine angle (CPA) tumors may fill this restricted space and distort the regional anatomy. It may be difficult to determine even with high resolution magnetic resonance imaging (MRI) if the tumor is dural-based, or what the nerve of origin is if a schwannoma. While clinical history and exam are helpful, they are not unequivocal, particularly since many patients present with a myriad of symptoms, or conversely an incidental finding. We present an atypical appearing, asymptomatic CPA tumor, ultimately identified at surgery to be a trigeminal schwannoma. Case History A 40-year-old man presented with new-onset seizure. MRI identified an incidental heterogeneously contrast-enhancing CPA lesion (Fig. 1A–D). The tumor was centered on the internal auditory canal (IAC) with no tumor extension into Meckel's cave, IAC or jugular foramen. Audiometry demonstrated 10db of relative left-sided hearing loss with 100% word recognition. Physical examination was negative for focal neurologic deficits. A retrosigmoid craniotomy was performed and an extra-axial, yellow-hued mass was encountered and resected, which was ultimately confirmed to originate from the trigeminal nerve (Video 1). Gross total resection was achieved, and the patient recovered from surgery with partial ipsilateral trigeminal sensory loss and no other new neurologic deficits. Conclusion Pure CPA trigeminal schwannomas are rare, but should be considered in the differential for enhancing CPA lesions. Although, Meckel's cave involvement is frequently observed, it is not universal, and pure CPA schwannomas of all cranial nerves IV–XII have been reported in the literature.The link to the video can be found at: https://youtu.be/AlodYCu70F8.