Trigeminal Microvascular Decompression and Meckel's Cave Tumor Resection via Retrosigmoid Approach With Suprameatal Extension: 2-Dimensional Operative Video.

The leading cause of trigeminal neuralgia (TGN) relies on the microvascular conflict between the superior cerebellar artery (SCA) loop and the dorsal root entry zone of the trigeminal nerve (TN). However, lesions along the TN have been described as a possible cause of TGN for direct mass effect or indirect vascular transposition. Thus, the surgical approach to TGN in patients harboring cerebellopontine angle or Meckel's cave tumor should be methodically chosen. The retrosigmoid (RS) approach with suprameatal extension offers direct access to the TN in both its cisternal and Meckel's cave segment, allowing optimal TN decompression from vascular and tumoral components. Although the RS approach with suprameatal extension has been described in numerous studies,1-4 videos detailing its key steps in addressing a multicomponent TGN are lacking. In this video, we highlight the case of a 46 year-old woman with 6 months of medically refractory typical TGN with a right en plaque meningioma involving the petrous bone, petroclival junction, Meckel's cave, and tentorium. In addition, magnetic resonance imaging was suspicious for a compressive SCA loop over the dorsal root entry zone. The patient underwent a RS approach with suprameatal extension for subtotal resection of the tumor and microvascular decompression of the TGN. The patient recovered with no complications and TGN resolved.

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.

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.

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.

Tensor Tympani and Stapedial Tendon Reconstruction for Postoperative Hyperacusis after Tendon Lysis for Middle Ear Myoclonus.

OBJECTIVE: To present a method for repair of the stapedial and tensor tympani tendons in a patient with hyperacusis after a tendon lysis procedure. PATIENTS: A 71-year-old professional musician who presented to clinic with debilitating hyperacusis following a tensor tympani and stapedial tendon lysis procedure to treat middle ear myoclonus. INTERVENTIONS: A novel procedure for reapproximation of the tensor tympani and stapedial tendons into their native insertion points using periosteal grafts and nitinol wire. MAIN OUTCOMES MEASURES: Stapedial reflex measurements, uncomfortable loudness level, and subjective patient experience. RESULTS: Postoperatively, the patient had objective improvement in hyperacusis with return of acoustic reflexes in the affected ear and durable improvements in their frequency-specific uncomfortable loudness levels. CONCLUSIONS: This case describes the debilitating complication of hyperacusis following tendon lysis and highlights the importance of maximizing behavioral and medical measures prior to undergoing surgical intervention for middle ear myoclonus.

Risk of Monopolar Electrosurgery in Cochlear Implant Recipients is Nominal: Evidence to Guide Clinical Practice.

OBJECTIVE: Comprehensively assess the prevalence of monopolar electrosurgery-related device complications among cochlear implant (CI) recipients. STUDY DESIGN: Multifaceted retrospective review and survey. SETTING: Tertiary medical center. METHODS: Multifaceted approach including: (i) review of the current literature; (ii) historical review of institutional data from an academic, tertiary CI center; (iii) review of industry data provided by 3 Food and Drug Administration-approved CI manufacturers; and (iv) survey of high-volume CI centers. RESULTS: Literature review identified 9 human studies, detailing 84 devices with 199 episodes of device-cautery exposure. From studies reporting on patients records, no implant showed evidence of damage after exposure. One cadaveric study using dental cautery reported 1 episode of device damage. Review of institutional records did not identify any CI damage in 84 instances of exposure. Data from the 3 major implant manufacturers showed a single report of damage that could be reasonably linked to monopolar electrosurgery, out of a possible 689,426 CIs. Last, a survey of 8 high-volume CI centers did not identify any adverse events associated with monopolar cautery. CONCLUSION: These data estimate the risk of adverse device-related events or tissue injury to be extraordinarily low. Short of operating in immediate proximity to the CI (ie, the ipsilateral temporoparietal scalp), these data indicate that monopolar electrosurgery can be used in the body and the head-and-neck of CI recipients with nominal risk. These findings may guide decision-making in cases that are optimally or preferably performed with monopolar electrocautery and can be used to counsel CI patients following inadvertent exposures.

Natural History of Serviceable Hearing During Active Surveillance of Nongrowing Sporadic Vestibular Schwannoma Supports Consideration of Initial Wait-and-Scan Management.

OBJECTIVE: The treatment paradigm of vestibular schwannoma (VS) focuses on preservation of neurologic function, with small tumors increasingly managed with active surveillance. Often, tumor size and hearing outcomes are poorly correlated. The aim of the current work was to describe the natural history of hearing among patients with nongrowing VS during observational management. STUDY DESIGN: Historical cohort study. PATIENTS: Adults with sporadic VS. INTERVENTION: Wait-and-scan management. MAIN OUTCOME MEASURE: Maintenance of serviceable hearing (SH) after diagnosis. RESULTS: Among 228 patients with nongrowing VS, 157 patients had SH at diagnosis. Rates of maintaining SH (95% CI; number still at risk) at 1, 3, and 5 years after diagnosis were 94% (89-98; 118), 81% (74-89; 65), and 78% (71-87; 42), respectively. Poorer hearing at diagnosis (hazard ratio [HR] per 10 dB hearing level increase in pure-tone average of 2.51, p < 0.001; HR per 10% decrease in word recognition score of 1.70, p = 0.001) was associated with increased likelihood of developing non-SH during observation. When controlling for baseline hearing status, tumors measuring 5 mm or greater in the internal auditory canal or with cerebellopontine angle extension were associated with significantly increased risk of developing non-SH (HR, 4.87; p = 0.03). At 5 years after diagnosis, 95% of patients with nongrowing intracanalicular VS measuring less than 5 mm maintained SH. CONCLUSIONS: Hearing worsens during periods of nongrowth in sporadic VS. Patients with small (<5 mm) intracanalicular tumors demonstrate robust maintenance of SH over time, reinforcing the consideration of initial observation in this patient subset.

Comparing Speech Recognition Outcomes Between Cochlear Implants and Auditory Brainstem Implants in Patients With NF2-Related Schwannomatosis.

OBJECTIVE: To compare cochlear implant (CI) and auditory brainstem implant (ABI) performance in patients with NF2-related schwannomatosis (NF2). STUDY DESIGN: Historical cohort. SETTING: Tertiary academic center. PATIENTS: A total of 58 devices among 48 patients were studied, including 27 ABIs implanted from 1997 to 2022 and 31 CIs implanted from 2003 to 2022. Three patients had bilateral ABIs, three had bilateral CIs, three had an ABI on one side and a CI on the other, one had a CI that was later replaced with an ipsilateral ABI, and one had an ABI and CI concurrently on the same side. INTERVENTIONS: CI or ABI ipsilateral to vestibular schwannoma. MAIN OUTCOME MEASURES: Open-set speech perception, consonant-nucleus-consonant word scores, and AzBio sentence in quiet scores. RESULTS: Among all patients, 27 (47%) achieved open-set speech perception, with 35 (61%) daily users at a median of 24 months (interquartile range [IQR], 12-87 mo) after implantation. Comparing outcomes, CIs significantly outperformed ABIs; 24 (77%) CIs achieved open-set speech perception compared with 3 (12%) ABIs, with median consonant-nucleus-consonant and AzBio scores of 31% (IQR, 0-52%) and 57% (IQR, 5-83%), respectively, for CIs, compared with 0% (IQR, 0-0%) and 0% (IQR, 0-0%), respectively, for ABIs. Patients with ABIs were younger at diagnosis and at implantation, had larger tumors, and were more likely to have postoperative facial paresis. CONCLUSION: Many patients with NF2-associated vestibular schwannoma achieved auditory benefit with either a CI or an ABI; however, outcomes were significantly better in those patients who were able to receive a CI. When disease and anatomy permit, hearing rehabilitation with a CI should be considered over an ABI in these patients. Tumor management strategies that increase the ability to successfully use CIs should be strongly considered given the high risk of losing bilateral functional acoustic hearing in this population.

Withdrawal of bevacizumab is associated with rebound growth of vestibular schwannomas in neurofibromatosis type 2-related schwannomatosis patients.

Background: Neurofibromatosis type 2 (NF2)-related schwannomatosis is an autosomal dominant tumor-predisposition syndrome characterized by bilateral vestibular schwannomas (VS). In patients with VS associated with NF2, vascular endothelial growth factor A inhibitor, bevacizumab, is a systemic treatment option. The aim of this study is to retrospectively evaluate NF2 patient responses to bevacizumab on VS growth and symptom progression. Methods: This is a retrospective analysis of patients seen at the Mayo Clinic Rochester Multidisciplinary NF2 Clinic. Results: Out of 76 patients with NF2 evaluated between 2020 and 2022, we identified 19 that received treatment with bevacizumab. Thirteen of these patients discontinued bevacizumab after median treatment duration of 12.2 months. The remaining 6 patients are currently receiving bevacizumab treatment for a median duration of 9.4 months as of March, 2023. Fifteen patients had evaluable brain MRI data, which demonstrated partial responses in 5 patients, stable disease in 8, and progression in 2. Within 6 months of bevacizumab discontinuation, 5 patients had rebound growth of their VS greater than 20% from their previous tumor volume, while 3 did not. Three patients with rebound growth went on to have surgery or irradiation for VS management. Conclusions: Our single-institution experience confirms prior studies that bevacizumab can control progression of VS and symptoms associated with VS growth. However, we note that there is the potential for rapid VS growth following bevacizumab discontinuation, for which we propose heightened surveillance imaging and symptom monitoring for at least 6 months upon stopping anti-VEGF therapy.

Anatomic Variants in the Anterior Inferior Cerebellar Artery Encountered During Resection of Vestibular Schwannomas.

BACKGROUND AND OBJECTIVES: Vestibular schwannomas (VS) are often phenotypically benign lesions that may be technically challenging to resect because of involvement of neurovascular structures. The anterior inferior cerebellar artery (AICA) is commonly identified near VS, with variable position in relation to the tumor; however, little published literature describes anatomic and pathologic variants of AICA observed during VS resection. METHODS: A prospectively maintained cohort of surgically managed VS with available operative reports and clinical/radiographic follow-up was queried and reviewed for noted aberrations. RESULTS: We identified 66 cases with noted AICA abnormalities among 880 reviewer cases, including 20 loops extending into the internal auditory canal (2.3%), 18 arteries embedded in dura (2.0%), 15 AICA branches directly within VS (1.7%), 8 main trunk arteries coursing between cranial nerves 7 and 8 (0.9%), 3 arteries embedded in temporal bone (0.2%), 1 aneurysm (0.1%), and 1 artery bifurcating cranial nerve 6 (0.1%). The median age of AICA-variant patients was 55 years (range 19-74), and 29 were female (45%). Compared with the other AICA variants, tumors embedded with AICA tended to be larger lesions on maximal axial diameter (2.9 vs 1.6 cm; P = .006), they more commonly underwent less than total resection (73% vs 28%; P = .0001), and they had higher rates postoperative House-Brackmann scores >2 (47% vs 20%; P = .005). Two patients had radiographic and symptomatic postoperative cerebral ischemia or hemorrhage-1 from a bone-encased AICA and 1 from a dural embedded variant. CONCLUSION: Anatomic variants of AICA occur in approximately 7% of VS operations. Most aberrations do not affect surgical or clinical outcomes, and the rate of major vascular injury was low. However, certain types variably add operative time and in the case of AICA encasement in the tumor, likely indicate a more aggressive tumor phenotype with lower rates of gross total resection and high incidences of facial nerve weakness.

Initial Experiences with the Envoy Acclaim® Fully Implanted Cochlear Implant.

Introduction: Cochlear implantation has become the standard of care for the treatment of moderate-to-profound bilateral sensorineural hearing loss. However, current technologies, all of which rely on an external sound processor, have intrinsic limitations that prevent certain activities and diagnostics, thus hampering full integration into a patient's lifestyle. The Envoy Medical (White Bear Lake, MN, USA) Acclaim® fully implanted cochlear implant is a new device currently undergoing testing that has been designed to alleviate many of the current constraints by housing all components within the patient, thus allowing for near-constant use in many environments that are not conducive to a traditional cochlear implant. Methods: As part of an Early Feasibility Study, three adult implant candidates were implanted with the Acclaim® cochlear implant. Surgical video and photography were taken, and initial observations were recorded. Implantation with the Acclaim® device is largely similar to a traditional cochlear implant, with modifications to allow room for the implanted sensor as well as the implantation of a battery in the subcutaneous tissues of the chest. Results: This study demonstrates a step-by-step overview of implanting the Acclaim® and discusses initial insight and experiences with the first three implantations with this new device. Conclusions: All three surgeries proceeded without complication, and at activation, all three patients were hearing through their devices. Surgery is more technically challenging compared to a standard cochlear implant, but the skills needed can all be mastered by a dedicated otologic surgeon.

Cochlear Implant Outcomes between Patients with Sporadic and Neurofibromatosis Type 2-Associated Vestibular Schwannoma.

OBJECTIVE: Compare cochlear implant (CI) performance between patients with ipsilateral sporadic vestibular schwannoma (VS) and NF2-related schwannomatosis (NF2). Compare CI performance according to VS management modality. STUDY DESIGN: Historical cohort. SETTING: Tertiary academic center. PATIENTS: Forty-nine patients (52 ears) undergoing cochlear implantation in the setting of ipsilateral sporadic (n = 21) or NF2-associated VS (n = 28). INTERVENTIONS: CI ipsilateral to VS. MAIN OUTCOME MEASURES: Auditory thresholds, consonant-nucleus-consonant (CNC) word scores, and AzBio sentences in quiet scores. RESULTS: Among all patients, median post-CI pure tone average was 28 dB HL (interquartile range [IQR], 21-38), CNC word score was 39% (IQR, 6-62), and AzBio sentences in quiet score was 60% (IQR, 11-83) at a median of 12.5 months postimplantation. Despite the NF2 cohort having larger tumors, when comparing patients with sporadic versus NF2-associated VS, there were no statistically significant differences in CNC word (49% [30-70] vs. 31% [0-52]) or AzBio sentences in quiet (66% [28-80] vs. 57% [5-83]) scores. Regardless of NF2 status, all patients managed with observation, and radiosurgery achieved open-set speech. In patients who underwent microsurgery, 6 (46%) of 13 with NF2 achieved open-set speech recognition compared with 4 (67%) of 6 with sporadic disease. CONCLUSION: Select patients with VS achieve successful hearing rehabilitation with a CI. In this cohort, tumor management strategy significantly influenced CI performance, whereas differences in NF2 status exhibited less effect. Specifically, all patients managed with observation or radiosurgery achieved open-set speech perception, whereas approximately half of people with NF2-related VS and two-thirds of people with sporadic VS achieved this outcome after tumor microsurgery. When disease permits, observation and radiosurgery should be considered in patients who may later pursue a CI.

The Effect of Age on Facial Nerve Recovery After Vestibular Schwannoma Resection.

OBJECTIVE: The objective of this study is to assess the influence of age on facial nerve recovery after microsurgical resection of sporadic vestibular schwannoma. STUDY DESIGN: A historical cohort study was performed. SETTING: The study was performed at a tertiary referral center. PATIENTS: The studied cohort included patients with a House-Brackmann (HB) Grade III or worse in the immediate postoperative period. INTERVENTIONS: The studied intervention was microsurgical resection. MAIN OUTCOME MEASURES: The main outcome measure was complete recovery of facial nerve function to HB Grade I at least 12 months postoperatively. RESULTS: There were six patients with intracanalicular tumors and 100 with cerebellopontine angle (CPA) tumors eligible for study. Given the few patients with intracanalicular tumors, no further analysis was pursued in this subset. For patients with CPA tumors, a multivariable analysis of several patient and tumor characteristics demonstrated age at surgery (odds ratio for 10-year increase of 0.68; 95% confidence interval [CI], 0.47-0.98; p = 0.04) and immediate postoperative HB grade (odds ratio for one-grade increase of 0.27; 95% CI, 0.15-0.50; p < 0.001) to be jointly significantly associated with complete recovery to HB Grade I, indicating that the likelihood of complete facial nerve recovery was higher for younger patients and for those with better immediate postoperative HB grades. For example, the predicted probability of complete facial nerve recovery for a 30-year-old with immediate postoperative HB Grade III was 0.76 (or 76% when expressed as a percentage), whereas the predicted probability for a 50-year-old with immediate postoperative HB Grade V was only 0.10. CONCLUSIONS: After considering immediate postoperative HB grade, younger age at surgery was independently significantly associated with complete facial nerve recovery, which can assist in intraoperative decision-making regarding extent of resection and postoperative counseling.

Intraoperative diagnosis of facial schwannomas: a multicenter summation of clinical experience, preoperative avoidance, and intraoperative management protocol.

OBJECTIVE: Preoperative differentiation of facial nerve schwannoma (FNS) from vestibular schwannoma (VS) can be challenging, and failure to differentiate between these two pathologies can result in potentially avoidable facial nerve injury. This study presents the combined experience of two high-volume centers in the management of intraoperatively diagnosed FNSs. The authors highlight clinical and imaging features that can distinguish FNS from VS and provide an algorithm to help manage intraoperatively diagnosed FNS. METHODS: Operative records of 1484 presumed sporadic VS resections between January 2012 and December 2021 were reviewed, and patients with intraoperatively diagnosed FNSs were identified. Clinical data and preoperative imaging were retrospectively reviewed for features suggestive of FNS, and factors associated with good postoperative facial nerve function (House-Brackmann [HB] grade ≤ 2) were identified. A preoperative imaging protocol for suspected VS and recommendations for surgical decision-making following an intraoperative FNS diagnosis were created. RESULTS: Nineteen patients (1.3%) with FNSs were identified. All patients had normal facial motor function preoperatively. In 12 patients (63%), preoperative imaging demonstrated no features suggestive of FNS, with the remainder showing subtle enhancement of the geniculate/labyrinthine facial segment, widening/erosion of the fallopian canal, or multiple tumor nodules in retrospect. Eleven (57.9%) of the 19 patients underwent a retrosigmoid craniotomy, and in the remaining patients, a translabyrinthine (n = 6) or transotic (n = 2) approach was used. Following FNS diagnosis, 6 (32%) of the tumors underwent gross-total resection (GTR) and cable nerve grafting, 6 (32%) underwent subtotal resection (STR) and bony decompression of the meatal facial nerve segment, and 7 (36%) underwent bony decompression only. All patients undergoing subtotal debulking or bony decompression exhibited normal postoperative facial function (HB grade I). At the last clinical follow-up, patients who underwent GTR with a facial nerve graft had HB grade III (3 of 6 patients) or IV facial function. Tumor recurrence/regrowth occurred in 3 patients (16%), all of whom had been treated with either bony decompression or STR. CONCLUSIONS: Intraoperative diagnosis of an FNS during a presumed VS resection is rare, but its incidence can be reduced further by maintaining a high index of suspicion and undertaking further imaging in patients with atypical clinical or imaging features. If an intraoperative diagnosis does occur, conservative surgical management with bony decompression of the facial nerve only is recommended, unless there is significant mass effect on surrounding structures.

Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Far Lateral Approach.

Introduction Skull base neuroanatomy is classically taught using surgical atlases. Although these texts are critical and rich resources for learning three-dimensional (3D) relationships between key structures, we believe they could be optimized and complemented with step-by-step anatomical dissections to fully meet the learning needs of trainees. Methods Six sides of three formalin-fixed latex-injected specimens were dissected under microscopic magnification. A far lateral craniotomy was performed by each of three neurosurgery resident/fellow at varying stages of training. The study objective was the completion and photodocumentation of the craniotomy to accompany a stepwise description of the exposure to provide a comprehensive, intelligible, and anatomically oriented resource for trainees at any level. Illustrative case examples were prepared to supplement approach dissections. Results The far lateral approach provides a wide and versatile corridor for posterior fossa operation, with access spanning the entire cerebellopontine angle (CPA), foramen magnum, and upper cervical region. Key Steps Include The study includes the following steps: positioning and skin incision, myocutaneous flap, placement of burr holes and sigmoid trough, fashioning of the craniotomy bone flap, bilateral C1 laminectomy, occipital condyle/jugular tubercle drilling, and dural opening. Conclusion Although more cumbersome than the retrosigmoid approach, a far lateral craniotomy offers unparalleled access to lesions centered lower or more medially in the CPA, as well as those with significant extension into the clival or foramen magnum regions. Dissection-based neuroanatomic guides to operative approaches provide a unique and rich resource for trainees to comprehend, prepare for, practice, and perform complex cranial operations, such as the far lateral craniotomy.

Predictive Value of K i -67 Index in Evaluating Sporadic Vestibular Schwannoma Recurrence: Systematic Review and Meta-analysis.

Introduction K i -67 is often used as a proliferation index to evaluate how aggressive a tumor is and its likelihood of recurrence. Vestibular schwannomas (VS) are a unique benign pathology that lends itself well to evaluation with K i -67 as a potential marker for disease recurrence or progression following surgical resection. Methods All English language studies of VSs and K i -67 indices were screened. Studies were considered eligible for inclusion if they reported series of VSs undergoing primary resection without prior irradiation, with outcomes including both recurrence/progression and K i -67 for individual patients. For published studies reporting pooled K i -67 index data without detailed by-patient values, we contacted the authors to request data sharing for the current meta-analysis. Studies reporting a relationship between K i -67 index and clinical outcomes in VS for which detailed patients' outcomes or K i -67 indices could not be obtained were incorporated into the descriptive analysis, but excluded from the formal (i.e., quantitative) meta-analysis. Results A systematic review identified 104 candidate citations of which 12 met inclusion criteria. Six of these studies had accessible patient-specific data. Individual patient data were collected from these studies for calculation of discrete study effect sizes, pooling via random-effects modeling with restricted maximum likelihood, and meta-analysis. The standardized mean difference in K i -67 indices between those with and without recurrence was calculated as 0.79% (95% confidence interval [CI]: 0.28-1.30; p = 0.0026). Conclusion K i -67 index may be higher in VSs that demonstrate recurrence/progression following surgical resection. This may represent a promising means of evaluating tumor recurrence and potential need for early adjuvant therapy for VSs.

Classifying the Large Vestibular Aqueduct: Morphometry to Audiometry.

OBJECTIVE: Large vestibular aqueduct (LVA) is the most common inner ear dysplasia identified in patients with hearing loss. Our objective was to systematically quantify LVA morphologies and correlate imaging findings with established audiometric outcomes. STUDY DESIGN: Retrospective review. SETTING: Tertiary referral center. PATIENTS: Patients with large vestibular aqueduct identified radiographically, with or without hearing loss. INTERVENTIONS: Diagnostic only. MAIN OUTCOME MEASURES: Vestibular aqueduct (VA) width at midpoint, width at external aperture, and length were measured on cross-sectional imaging. Morphology was classified as type I (borderline), type II (tubular), or type III (funneled). Audiometric endpoints included air/bone conduction, pure tone averages, and air-bone gaps at 250 and 500 Hz. Statistical associations were evaluated using linear regression models, adjusted for age at first audiogram and sex. RESULTS: One hundred seventeen patients (197 ears) were included, with mean age at first audiogram of 22.2 years (standard deviation, 21.7 yr). Imaging features associated with poor audiometric outcomes were increasing VA width at midpoint and external aperture, decreasing VA length, dilated extraosseous endolymphatic sac, cochleovestibular malformations, and increasing VA type (III > II > I). CONCLUSIONS: Quantitative LVA measurements and a standardized morphologic classification system aid in prediction of early audiometric endpoints.

Salvage radiosurgery following subtotal resection of vestibular schwannomas: does timing influence tumor control?

OBJECTIVE: The goal of microsurgical resection of vestibular schwannoma (VS) is gross-total resection (GTR) to provide oncological cure. However, a popular strategy is to halt the resection if the surgical team feels the risk of cranial nerve injury is imminent, achieving a maximally safe subtotal resection (STR) instead. The tumor remnant can then be treated with stereotactic radiosurgery (SRS) once the patient has recovered from the immediate postoperative period, or it can be followed with serial imaging and treated with SRS in a delayed fashion if residual tumor growth is seen. In this study, the authors evaluated the efficacy of this multimodality approach, particularly the influence of timing and dose of SRS on radiological tumor control, need for salvage treatment, and cranial nerve function. METHODS: VS patients treated with initial microsurgery and subsequent radiosurgery were retrospectively included from two tertiary treatment centers and dichotomized depending on whether SRS was given upfront (defined as before 12 months) or later. Radiological tumor control was defined as less than 20% tumor volume expansion and oncological tumor control as an absence of salvage treatment. Facial and cochlear nerve functions were assessed after surgery, at the time of SRS, and at last follow-up. Finally, a systematic literature review was conducted according to PRISMA guidelines. RESULTS: A total of 110 VS patients underwent SRS following microsurgical resection, with a mean preradiosurgical tumor volume of 2.2 cm3 (SD 2.5 cm3) and mean post-SRS follow-up time of 5.8 years (SD 4.1 years). The overall radiological tumor control and oncological tumor control were 77.3% and 90.9%, respectively. Thirty-five patients (31.8%) received upfront SRS, while 75 patients (68.2%) were observed for a minimum of 12 months prior to SRS. The timing of SRS did not influence the radiological tumor control (p = 0.869), the oncological tumor control (p = 0.560), or facial nerve (p = 0.413) or cochlear nerve (p = 0.954) function. An escalated marginal dose (> 12 Gy) was associated with greater tumor shrinkage (p = 0.020) and superior radiological tumor control (p = 0.020), but it did not influence the risk of salvage treatment (p = 0.904) or facial (p = 0.351) or cochlear (p = 0.601) nerve deterioration. CONCLUSIONS: Delayed SRS after close observation of residuals following STR is a safe alternative to upfront SRS regarding tumor control and cranial nerve preservation in selected patients.

Fluorescein-Assisted Microsurgical Resection of Vestibular Schwannoma: A Prospective Feasibility Study.

OBJECTIVE: To evaluate the optimal dose and timing of administration of sodium fluorescein (SF) for selective fluorescence of sporadic vestibular schwannoma (VS) during microsurgery with the YELLOW 560-nm microscope filter (YE560) and to characterize the potential benefit of this fluorescence as determined by intraoperative surgeon assessment. STUDY DESIGN: Prospective cohort study. SETTING: Tertiary referral center. PATIENTS: Adult patients undergoing VS microsurgery. INTERVENTIONS: Intraoperative intravenous administration of SF and visualization with the YE560. MAIN OUTCOME MEASURES: Time to differential fluorescence, duration of fluorescence, correlation of fluorescence of VS with electrostimulation and white light microscopy visual assessment, and likelihood of surgeons to use SF with the YE560 in future cases. RESULTS: Novel use of SF and YE560 during microsurgery achieved selective fluorescence of VS with capabilities to differentiate nerve fascicles and tumor approximately 30 minutes after administration. Nuances of SF administration and timing are discussed. Seventy-five percent of surgeons observed an excellent correlation of selective fluorescence with white light microscopy. Representative images and cases are presented. CONCLUSIONS: SF and YE560 may be used in VS microsurgery to visually differentiate VS from surrounding nerves. Potential benefits include enhanced visualization of the tumor-nerve interface for tumor dissection and detection of any residual disease, such as in the fundus after hearing preservation microsurgery.