Faculty Bibliography

OBJECTIVE:NF2-related schwannomatosis (NF2-SWN) is an autosomal dominant genetic disorder characterized by the development of schwannomas, meningiomas, and spinal ependymomas. Treatment with bevacizumab, a monoclonal antibody against VEGF, has been shown to result in decreased vestibular schwannoma size and hearing improvement in ~50% of NF2-SWN patients. It is unknown whether the same degree of benefit is seen in younger patients compared with older patients. The objective of this study is to determine the association between age and bevacizumab treatment outcomes in NF2-SWN. STUDY DESIGN/METHODS:Retrospective cohort study. SETTING/METHODS:Tertiary referral center. PATIENTS/METHODS:Thirty-seven patients with NF2-SWN. INTERVENTIONS/METHODS:Bevacizumab. MAIN OUTCOME MEASURES/METHODS:Change in tumor size of 20% or more. RESULTS:This study includes 37 patients with NF2-SWN who were treated with bevacizumab at our institution between 2014 and 2024. They were divided into 2 groups: 22 adults over the age of 25 (26 to 71 y) and 15 adolescent and young adult (AYA) patients under the age of 25 (12 to 24 y). The median treatment duration was 2.1 years. A significantly higher proportion of AYA schwannomas (37.5%, n=9) exhibited radiographic tumor progression during the treatment period compared with those of the older patient group (11.9%, n=5) (P=0.026), despite similar pre-treatment growth rates. There was no significant difference in the proportion of older and younger patients with hearing decline, improvement, or stability (P>0.05). CONCLUSIONS:AYA patients were significantly more likely to exhibit progression of tumor growth during bevacizumab treatment compared with older patients, though no significant differences were detected in hearing outcomes.

OBJECTIVE:To characterize patient outcomes after primary stereotactic radiosurgery (SRS) for the management of sporadic facial nerve schwannoma. STUDY DESIGN/METHODS:Retrospective cohort study. SETTING/METHODS:Six tertiary referral centers across the United States and United Kingdom. PATIENTS/METHODS:Adults undergoing SRS from 2000 through 2023 for sporadic facial nerve schwannoma along any segment of the facial nerve were included. Patients with NF2-related schwannomatosis were excluded. INTERVENTION/METHODS:Stereotactic radiosurgery. MAIN OUTCOME MEASURE/METHODS:Long-term tumor control. RESULTS:Among 60 patients meeting inclusion, the median age at SRS was 52 years (IQR: 41 to 64) with a median tumor size of 19.5 mm (IQR: 14.7 to 22.8). Tumors commonly involved the internal auditory canal (73%), cisternal (49%), geniculate/labyrinthine (47%), and tympanic segments (22%). Two patients experienced SRS failure and underwent salvage treatment; salvage-free survival rates (95% CI; number still at risk) at 1, 3, 5, and 10 years after SRS were 100% (100 to 100; 55), 100% (100 to 100; 36), 100% (100 to 100; 18), and 87% (72 to 100; 9), respectively. Among 31 (52%) patients with House-Brackmann (HB) grade I facial function at presentation, only 6 demonstrated worse facial function at a median of 3.2 years (IQR: 1.7 to 6.6) after SRS. Of 18 patients with serviceable hearing (AAO-HNS class A/B) at SRS, 13 maintained serviceable hearing at a median of 1.0 years (IQR: 0.5 to 4.9) of post-SRS audiometric follow-up. CONCLUSIONS:Durable tumor control after primary SRS for sporadic facial nerve schwannoma is achieved in most patients. Among those with HB grade I facial function at presentation, treatment with SRS harbors limited additional risk of facial paresis beyond observation alone.

OBJECTIVE/UNASSIGNED:We sought to consolidate the anatomical findings from radiologic research and prior surgical literature to develop a stepwise surgical approach utilizing cadaveric specimens which can serve to improve the accuracy and scalability of surgical apical cochleostomies in the future. METHODS/UNASSIGNED:Cadaveric temporal bone dissections, with subsequent image documentation and distance measurements to confirm surgical accuracy. RESULTS/UNASSIGNED:All four temporal bones (100%) that were drilled utilizing the newly developed surgical approach had an accurately placed apical cochleostomy. No inadvertent entry into the middle turn of the cochlea occurred. There was no violation of the labyrinthine facial nerve, or carotid artery. CONCLUSIONS/UNASSIGNED:Preliminary findings are promising for the described steps to achieve a substantial improvement in apical cochleostomy accuracy, with reduced trauma compared to historically taught techniques.

BACKGROUND AND OBJECTIVES/OBJECTIVE:Surgery in NF2-related schwannomatosis (NF2-SWN) vestibular schwannoma (VS) carries a higher risk of facial nerve damage, hearing loss, and partial resection, than in sporadic cases. Radiosurgery is also associated with higher failure compared with sporadic schwannomas. Nowadays, bevacizumab (BEV) is frequently considered in the NF2-SWN population. However, some patients experience progression despite treatment. Among other surgical risks, in BEV-treated patients, hemorrhage and impaired healing are specific considerations. These concerns have led manufacturers to recommend stopping BEV 6 to 8 weeks preoperatively. The aim of our multicentric study was to assess the perioperative bleeding risk and postoperative outcomes in NF2-SWN patients undergoing VS surgery after preoperative BEV treatment. METHODS:Our retrospective analysis included medical and surgical records along with imaging reviews from 4 high-volume tertiary academic referral centers for NF2-SWN and VS. RESULTS:A total of 21 patients met the inclusion criteria. VS had a mean volume of 13.2 ±7.6 cm3 corresponding to 1 KOOS III and 20 KOOS IV. BEV was stopped at a mean of 5.8 ± 4.0 months before surgery with a total mean treatment duration of 33.7 ± 20.7 months and a monthly dose of 10.2 ± 4.1 mg/kg. Intraoperatively, the tumor was assessed to be bloody by the operating surgeons in 7 patients. Late BEV discontinuation and high cumulative dose independently predicted perioperative bleeding and longer surgery duration. No other complication such as wound dehiscence was reported. CONCLUSION/CONCLUSIONS:Our findings suggest that a higher cumulative BEV dose (∼600 mg/kg) and a longer interval between BEV discontinuation and surgery (∼8 months) are associated with a modest but statistically significant increase in intraoperative bleeding risk. Based on these observations, a BEV-free window between 6 weeks and 6 months (depending on the clinical scenario) before tumor resection seems optimal, particularly for patients with high cumulative exposure.

Congenital cholesteatomas are defined as a collection of epithelium in the absence of prior surgery or pathologic retraction. They are most commonly found in the middle ear and are thought to arise from a residual epithelial rest present since birth; however, a small number of cases present with disease isolated to the mastoid bone. One such case and a review of prior reports are presented. A 29-year-old male with a 2-year history of headaches and no otologic surgery was found to have a destructive mass centered in the right mastoid bone, invading the jugular foramen and posterior fossa without middle ear disease. He underwent a mastoidectomy with complete resection of the cholesteatoma. A literature review identified 21 prior cases of isolated mastoid congenital cholesteatoma. Congenital cholesteatoma should be considered in the differential diagnosis when patients present with postauricular pain or headaches. Mastoidectomy is considered the treatment of choice.

OBJECTIVES/OBJECTIVE:Real-time monitoring of cochlear function to predict the loss of residual hearing after cochlear implantation is now possible. Current approaches monitor the cochlear microphonic (CM) during implantation from the electrode at the tip of the implant. A drop in CM response of >30% is associated with poorer hearing outcomes. However, there is prior evidence that CM amplitude can fluctuate in a manner unrelated to hearing trauma, leading to false positives. By monitoring another cochlear response, the auditory nerve neurophonic (ANN), a differentiation between CM drops that result in reduced cochlear output from false positives may be possible. The hypothesis tested in the present work was that ANN/CM ratios measured during a CM drop will increase during drops not associated with postoperative hearing loss. DESIGN/METHODS:Twenty-eight adult participants with known CM drops during implantation were taken from a larger data set. This contains adult cochlear implant candidates scheduled to receive a Cochlear Nucleus cochlear implant with either the slim-straight or slim-modiolar electrode array with preoperative audiometric low-frequency average thresholds of ≤80 dB HL at 500, 750, and 1000 Hz in the ear to be implanted. Patients were recruited from eight international implant sites. Pure-tone audiometry was measured postoperatively and 4 to 6 weeks after implantation. Electrocochleography was measured during and immediately after the implantation of the array in response to a 500-Hz, 6-msec pure-tone pip at 110 dB HL. RESULTS:The ANN/CM ratio rose during CM drops in 19 of these patients and decreased in 9. At the follow-up timepoint, patients with a decreasing ANN/CM ratio had a median hearing loss of 29.0 dB, significantly worse than the group with increasing ratio at 13.3 dB ( p = 0.004). Considering only the change in ANN amplitude during a CM drop led to smaller groups (ANN drop during CM drop N = 17, ANN increasing during CM drop N = 6) due to 5 patients having undetectable ANN during the CM drop. Using the ANN alone also led to as poorer prediction of hearing preservation, with median hearing preservation in the ANN increasing group of 12.9 dB, significantly better than the ANN decreasing group of 25 dB ( p = 0.02). The group with a decreasing ANN/CM ratio had maximum CM amplitude immediately after insertion lower than the maximum amplitude reached during insertion (mean maximum postinsertion amplitude of 98% of during-insertion amplitude). In comparison, the ANN/CM ratio increasing group tended to have a larger CM amplitude immediately after insertion (mean maximum CM amplitude postinsertion of 164% of the maximum during-insertion amplitude). CONCLUSIONS:These data show that the ANN/CM ratio is a measure that can differentiate between patients with CM drops that lead to a loss of residual hearing and those that do not. The ANN/CM ratio is easily measured and responds rapidly during a CM drop, showing clinical promise for improving current and developing approaches to intraoperative monitoring.

OBJECTIVE:Limited evidence guides the optimal timing of treatment after the detection of tumor growth during the observation of sporadic vestibular schwannoma (VS). The current work aimed to inform the timing of radiosurgical intervention based on an analysis of patient outcomes among those who ultimately failed stereotactic radiosurgery (SRS) and underwent salvage microsurgery. STUDY DESIGN/METHODS:A historical cohort study. SETTING/METHODS:Seven centers across the United States and Norway. METHODS:Adults with sporadic VS who underwent salvage microsurgery following failed primary SRS were included. The primary outcome of interest was the association between tumor size at the time of primary SRS and the ability to achieve gross total resection (GTR) and maintain postoperative House-Brackmann (HB) facial nerve grade I at the last follow-up after salvage microsurgery. RESULTS:Among 96 patients, the median (interquartile range [IQR]) cerebellopontine angle (CPA) tumor size at primary SRS was 14.5 mm (10.0-19.0). Each 1-mm increase in CPA tumor size at the time of primary SRS was associated with a 13% increased likelihood of near-total/subtotal resection or most recent postoperative HB grade >I (odds ratio [OR] 1.13, 95% confidence interval [CI] 1.05-1.21, P = .001), with an optimal tumor size threshold to distinguish this outcome of 12 mm of CPA extension (c-index 0.73). Similarly, for each 1-mm increase in CPA tumor size at the time of primary SRS, a 9% increase in any postoperative complication with salvage microsurgery was observed (OR 1.09, 95% CI 1.02-1.15, P = .009). CONCLUSION/CONCLUSIONS:Corroborated by size threshold surveillance data informing the timing of primary microsurgical resection, the current study suggests that VS outcomes are optimized when primary radiosurgical intervention is undertaken on growing tumors when they harbor 10-15 mm of cerebellopontine angle extension or less.

The current management of vestibular schwannomas (VS) includes observation, microsurgery, and stereotactic radiosurgery (SRS) or radiotherapy. Both microsurgery (MS) and irradiation have the potential for treatment failures. For microsurgical failures, options include observation, revision surgery, and SRS. SRS is most commonly used, as it carries a low risk of adverse events. Salvage MS following previous MS is reserved for specific cases and is often surgically challenging. For radiosurgical failures, both salvage MS and repeat SRS may be used. Salvage MS following SRS also tends to be challenging, although excellent facial nerve outcomes are achievable. Furthermore, repeat SRS is an emerging concept and should be considered in small tumors that are growing but are asymptomatic. This chapter is aimed at reviewing an approach to failure of primary interventions for vestibular schwannomas, with an emphasis on the time interval between modalities, tumor control rates, functional outcomes, and complications.

OBJECTIVE:To compare cochlear implant (CI) speech perception outcomes in patients with sporadic vestibular schwannoma (VS) managed with observation, radiosurgery, or microsurgery. STUDY DESIGN/METHODS:Retrospective review. SETTING/METHODS:Eleven tertiary academic medical centers. PATIENTS/METHODS:One hundred patients with sporadic VS who received an ipsilateral CI. INTERVENTIONS/METHODS:Ipsilateral cochlear implantation. MAIN OUTCOME MEASURES/METHODS:Pure-tone thresholds, monosyllabic speech perception testing scores, and rates of open-set speech acquisition. RESULTS:Of the 100 patients studied, 54 underwent microsurgery, 26 underwent radiosurgery, 19 continued observation, and 1 underwent multimodal therapy. Among all patients, the median post-implantation pure-tone average was 31 dB (interquartile range [IQR] 25-39 dB) and the median monosyllabic speech perception score was 30% (IQR 0-60%) at a median of 12 months (IQR 5-25 months) post-implantation. Patients who were managed with microsurgery (median speech perception score 11%, IQR 0-52%) exhibited poorer implant outcomes overall compared with those managed with observation (median speech perception score 52%, IQR 40-72%) or radiosurgery (median speech perception score 30%, IQR 16-60%). Open-set speech perception was achieved in 61% of patients managed with microsurgery, 100% with observation, and 80% with radiosurgery. In a multivariable setting, those managed with observation (p = 0.02) or who underwent radiosurgery (p = 0.04) were significantly more likely to achieve open-set speech perception compared with patients who underwent microsurgery. CONCLUSIONS:Cochlear implants offer benefit in selected patients with sporadic VS. Although achieved in over half of people after microsurgery, open-set speech perception is more reliably attained in patients who are treated with observation or radiosurgery compared with microsurgical resection. These data may inform patient counseling and VS tumor management in people who may benefit from implantation.

OBJECTIVE:To characterize transimpedance matrix (TIM) heatmap patterns in patients at risk of labyrinthine abnormality to better understand accuracy and possible TIM limitations. STUDY DESIGN/METHODS:Retrospective review of TIM patterns, preoperative, and postoperative imaging. SETTING/METHODS:Tertiary referral center. PATIENTS/METHODS:Patients undergoing cochlear implantation with risk of labyrinthine abnormality. INTERVENTION/METHODS:None. RESULTS:Seventy-seven patients were evaluated. Twenty-five percent (n = 19) of patients had a TIM pattern variant identified. These variants were separated into 10 novel categories. Overall, 9% (n = 6) of electrodes were malpositioned on intraoperative x-ray, of which 50% (n = 3) were underinserted, 17% (n = 1) were overinserted, 17% (n = 1) had a tip foldover, and 17% (n = 1) had a coiled electrode. The number of patients with a variant TIM pattern and normal x-ray was 18% (n = 14), and the number of patients with normal TIM pattern and malposition noted on x-ray was 3% (n = 2; both were electrode underinsertions that were recognized due to open circuits and surgical visualization).A newly defined skip heat pattern was identified in patients with IP2/Mondini malformation and interscalar septum width <0.5 mm at the cochlear pars ascendens of the basal turn. CONCLUSIONS:This study defines novel patterns for TIM heatmap characterization to facilitate collaborative and comparative research moving forward. In doing so, it highlights a new pattern termed skip heat, which corresponds with a deficient interscalar septum of the cochlea pars ascendens of the basal turn in patients with IP2 malformation. Overall, the data assist the surgeon in better understanding the implications and limitations of TIM patterns within groups of patients with risk of labyrinthine abnormalities.