Prevalence of Sporadic Vestibular Schwannoma: Reconciling Temporal Bone, Radiologic, and Population-based Studies

Automatic Segmentation of Vestibular Schwannoma From MRI Using Two Cascaded Deep Learning Networks

OBJECTIVE

Automatic segmentation and detection of vestibular schwannoma (VS) in MRI by deep learning is an upcoming topic. However, deep learning faces generalization challenges due to tumor variability even though measurements and segmentation of VS are essential for growth monitoring and treatment planning. Therefore, we introduce a novel model combining two Convolutional Neural Network (CNN) models for the detection of VS by deep learning aiming to improve performance of automatic segmentation.

METHODS

Deep learning techniques have been employed for automatic VS tumor segmentation, including 2D, 2.5D, and 3D UNet-like architectures, which is a specific CNN designed to improve automatic segmentation for medical imaging. Specifically, we introduce a sequential connection where the first UNet's predicted segmentation map is passed to a second complementary network for refinement. Additionally, spatial attention mechanisms are utilized to further guide refinement in the second network.

RESULTS

We conducted experiments on both public and private datasets containing contrast-enhanced T1 and high-resolution T2-weighted magnetic resonance imaging (MRI). Across the public dataset, we observed consistent improvements in Dice scores for all variants of 2D, 2.5D, and 3D CNN methods, with a notable enhancement of 8.86% for the 2D UNet variant on T1. In our private dataset, a 3.75% improvement was reported for 2D T1. Moreover, we found that T1 images generally outperformed T2 in VS segmentation.

CONCLUSION

We demonstrate that sequential connection of UNets combined with spatial attention mechanisms enhances VS segmentation performance across state-of-the-art 2D, 2.5D, and 3D deep learning methods.

LEVEL OF EVIDENCE

3 Laryngoscope, 135:1301-1308, 2025.

Prevalence of infratentorial superficial siderosis in a large general population sample from the UK Biobank

BACKGROUND

Classical infratentorial superficial siderosis (iSS) is considered a rare but potentially disabling neurological disorder. It results from slow chronic blood extravasation into the cerebrospinal fluid and deposition of the iron degradation product hemosiderin within the subpial layers of the central nervous system. Susceptibility-weighted (SW) magnetic resonance imaging (MRI) is the reference diagnostic modality. Few studies have described the population prevalence of cerebellar or infratentorial siderosis, and there are none from the UK population. The aim of this cross-sectional observational study was to estimate the prevalence of iSS in the UK Biobank sample using pre-defined radiological criteria.

METHODS

We reviewed SW MRIs of participants from the UK Biobank, looking for the radiological features of classical iSS: involvement of infratentorial structures (superior vermis, cerebellar folia, brainstem, or craniocervical junction). We calculated the point prevalence as the number of identified cases per total number of cases reviewed and 95% confidence intervals (CI) using Wilson's Score formula.

RESULTS

Of 10,305 SW MRIs reviewed, five cases with radiological features of iSS were identified demonstrating cerebellar/superior vermis involvement. The estimated prevalence of iSS was calculated as 48.5 (95%CI 20.7-113.5) cases per 100,000 population.

CONCLUSIONS

This is the first study to estimate iSS prevalence in the UK population. The prevalence of iSS is higher than that reported for other rare neurological and neuro-otological disorders, suggesting an important unmet healthcare need for early diagnosis and targeted management strategies. Further studies are needed to determine the clinical associations and prognostic significance of radiologically defined iSS in the general population.

Vestibular Schwannoma-Related Increased Labyrinthine Postgadolinium 3D-FLAIR Signal Intensity and Association with Hearing Impairment

BACKGROUND AND PURPOSE

Vestibular schwannomas (VSs) are benign neurogenic tumors commonly associated with progressive unilateral hearing loss, tinnitus, and vestibular symptoms. Growing evidence links signal changes in the VS-adjacent labyrinth with sensorineural hearing loss. This study seeks to quantify the association of labyrinthine signal on postgadolinium 3D-FLAIR imaging correlates with hearing loss and to evaluate potential longitudinal changes over time.

MATERIALS AND METHODS

Selected patients were identified from a prospectively maintained VS registry. Mean signal intensity ratios of the bilateral labyrinth and pons were measured on 3D-FLAIR postgadolinium MRI. Correlations with paired audiometric data, including pure tone average (PTA), word recognition score (WRS), and American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) hearing class within 1 year, were evaluated.

RESULTS

One hundred twenty-five studies obtained from 2015 to 2022 among 66 patients undergoing observational management for sporadic VS were analyzed. Increased signal intensity was noted in the VS-affected labyrinth/contralateral labyrinth (mean ratio 1.56, SD 0.58). Increased signal intensity was associated with increased PTA on both labyrinthine (correlation coefficient [CC] 0.20, P = .03) and pontine comparisons (CC 0.24, P = .006), and with decreased WRS on pontine comparisons (CC -0.18, P = .04). Increased signal intensity was significantly associated with nonserviceable AAO-HNS C/D hearing when intensities were compared with the pons (P = .01) but not the contralateral labyrinth (P = .1). Among 44 patients with available follow-up, no statistically significant associations were identified between audiometric data and signal changes over the same interval.

CONCLUSIONS

Increased 3D-FLAIR postgadolinium labyrinthine signal is associated with sensorineural hearing loss; however, its relationship with hearing trajectory remains unclear. Overall findings suggest that while postgadolinium 3D-FLAIR techniques are sensitive to inner ear involvement associated with VS, the driving mechanism and their temporal relationships with labyrinthine signal intensity and hearing impairment remain unknown.

Optimal Timing of Primary Radiosurgical Treatment of Growing Vestibular Schwannoma: Insights From Salvage Microsurgery Outcomes

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

A historical cohort study.

SETTING

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

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.

Analgesia After Vestibular Schwannoma Surgery in Europe-Potential for Reduction of Postoperative Opioid Usage

OBJECTIVE

Excessively prescribed opioids promote chronic drug abuse and worsen a highly prevalent public health problem in the era of the opioid epidemic. This study aimed to (a) determine general analgesic prescription patterns after surgery for vestibular schwannoma (VS) with a focus on opioid prescription rates, (b) identify risk factors for receiving narcotics for postoperative pain management, and (c) highlight the feasibility of opioid-free analgesic treatment strategies.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral center.

PATIENTS

A total of 105 adult inpatients who underwent VS surgery.

INTERVENTIONS

Analgesic prescription patterns were evaluated, and factors associated with opioid prescriptions were identified.

MAIN OUTCOME MEASURE

Number of prescribed analgesics.

RESULTS

Metamizole (=dipyrone) and acetaminophen (=paracetamol) were the most frequently prescribed non-opioid drugs. Sixty-three (60%) patients received an opioid with a median intake of 23.2 ± 24 mg of oral morphine equivalents. Only 10 (9.5%) individuals received opioids for longer than postoperative day 1. Subjects with small tumors undergoing middle cranial fossa tumor removal (p = 0.007) were more likely to receive opioid drugs. In contrast, patients undergoing retrosigmoid craniotomy required fewer opioids for pain control (p = 0.004). Furthermore, individuals receiving opioids were prone to obtain higher dosages of acetaminophen (odds ratio 1.054, 95% confidence interval 1.01-1.10, p = 0.022).

CONCLUSIONS

Opioids for acute postoperative analgesia after VS surgery may be necessary in many patients. However, middle- and long-term pain control can be accomplished using non-opioid treatment regimens, resulting in a reduction in opioid prescriptions and the accompanying negative effects on individual and public health.

Intraoperative Electrical Stapedius Reflex Testing to Monitor Cochlear Nerve Integrity during Simultaneous Vestibular Schwannoma Resection and Cochlear Implantation

OBJECTIVE

To compare the utility of intraoperative electrically evoked auditory brainstem response (eABR) and electrically evoked stapedial reflex testing (eSRT) for cochlear nerve integrity monitoring during simultaneous translabyrinthine resection of vestibular schwannoma (VS) and cochlear implantation.

STUDY DESIGN

Historical cohort study.

SETTING

Tertiary academic referral center.

PATIENTS

Eleven patients (12 cases) who underwent translabyrinthine tumor resection with simultaneous placement of a standard, unmodified cochlear implant (CI).

INTERVENTION

A CI placed at the beginning of the operation before tumor resection to facilitate intraoperative cochlear nerve monitoring through a CI-delivered electrical stimulus.

MAIN OUTCOME MEASURE

Correlation of intraoperative monitoring outcomes with postoperative CI performance.

RESULTS

Among the 12 cases (median age, 47 years), eABR waveforms were present at the conclusion of tumor resection in 10, including 6 that achieved open set speech perception. Of the 2 cases with negative eABR, 1 achieved open set speech perception. By contrast, of the 8 cases with a positive eSRT response, 7 achieved open set speech perception. Of the 4 cases with a negative eSRT response, none achieved open set speech perception. The 3 cases that did not receive auditory stimulation included 2 with positive and 1 with negative eABR; all 3 had a negative eSRT response.

CONCLUSIONS

Intraoperative eSRT using an unmodified CI is a promising new method for monitoring the integrity of the cochlear nerve during simultaneous VS resection. eSRT response at the conclusion of tumor resection strongly correlated with CI open set speech capacity. Although still useful, eABR was less reliable at predicting postoperative hearing outcomes in this series.

Long-Term Prospective Quality-of-Life Outcomes in 445 Patients with Sporadic Vestibular Schwannoma

OBJECTIVE

To evaluate the long-term changes in sporadic vestibular schwannoma (VS) disease-specific quality-of-life (QOL) outcomes.

STUDY DESIGN

Prospective longitudinal study using the Penn Acoustic Neuroma Quality of Life (PANQOL) Scale.

SETTING

National survey.

PATIENTS

Patients with sporadic VS who completed a baseline survey before treatment and at least one follow-up survey recruited through the authors' center and through the Acoustic Neuroma Association.

INTERVENTIONS

Observation, microsurgery, radiosurgery.

MAIN OUTCOME MEASURES

Changes in PANQOL scores from baseline to most recent survey.

RESULTS

Among 445 eligible patients the mean duration of follow-up was 4.4 (SD, 2.3) years, including 122, 218, and 105 in the observation, microsurgery, and radiosurgery groups, respectively. Patients managed with observation ( p = 0.03) or microsurgery ( p < 0.001) demonstrated improvement in anxiety scores. Changes in facial function scores differed significantly by management group ( p = 0.01), with patients undergoing microsurgery demonstrating a mean decline of 10 points in facial function scores compared with mean declines of 3 for those managed with observation or radiosurgery. Hearing loss scores decreased similarly over time for all three groups ( p = 0.3). There were minimal changes in total PANQOL scores over time across all management groups ( p = 0.5).

CONCLUSIONS

Long-term changes in total QOL among VS management groups are not significantly different. Microsurgery may continue to confer an advantage regarding improvement in anxiety postoperatively, but with a greater decline in facial function when compared to observation or radiosurgery. Long-term declines in hearing loss scores were not statistically significantly different among groups.

Comparing Cochlear Implant Outcomes in 100 Patients With Sporadic Vestibular Schwannoma Managed With Observation, Radiosurgery, or Microsurgery: A Multi-Institutional Review

OBJECTIVE

To compare cochlear implant (CI) speech perception outcomes in patients with sporadic vestibular schwannoma (VS) managed with observation, radiosurgery, or microsurgery.

STUDY DESIGN

Retrospective review.

SETTING

Eleven tertiary academic medical centers.

PATIENTS

One hundred patients with sporadic VS who received an ipsilateral CI.

INTERVENTIONS

Ipsilateral cochlear implantation.

MAIN OUTCOME MEASURES

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.

Documented Initial Growth Does Not Necessarily Indicate Treatment for Sporadic Vestibular Schwannomas

OBJECTIVE

To report the natural history of vestibular schwannoma (VS) who elected an initial period of observation and identify prognostic factors. To describe the natural history of growing VS, identify prognostic factors, and review the most recent literature.

STUDY DESIGN

Prospective cohort study and literature review.

SETTING

Tertiary referral center.

PATIENTS

Adult patients diagnosed with a VS between January 1998 and February 2023.

INTERVENTION

Magnetic resonance imaging surveillance.

MAIN OUTCOME MEASURES

Growth-free survival and subsequent growth-free survival considering significant growth as a change in size of ≥2 mm.

RESULTS

Of 430 patients undergoing observation with serial magnetic resonance imaging, 193 (44.9%) demonstrated significant growth at a median of 1.6 years (interquartile range, 0.94-3.51). Of the 193 patients who presented an initial episode of growth, 137 elected to continue to be observed. Of those, 83 (60.6%) presented a second episode of growth at a median of 1.43 years (interquartile range, 1.00-2.49). The subsequent growth-free survival rates (95% confidence interval) at 1, 3, 5, 7, and 10 years were 91.79% (87.26-96.56%), 64.44% (56.56-73.42%), 52.52% (44.23-62.35%), 42.23% (33.92-52.56%), and 36.11% (27.89-46.76%), respectively. Univariate and multivariate Cox regression analyses showed that EC tumor location and initial growth rate were significant predictors of subsequent growth.

CONCLUSIONS

Close observation after documentation of growth is an appropriate management in well-selected cases given that only around 56% of the tumor will continue to grow. Extracanalicular tumor location and initial growth rate are promising prognostic factors to help determine which patient would be a better candidate for close surveillance after initial documentation of growth.

Hearing Function after CyberKnife for Vestibular Schwannoma: A Systematic Review

Introduction  CyberKnife (CK) radiosurgery is a treatment strategy for vestibular schwannoma (VS). Objectives  To evaluate hearing preservation (HP) after CK for VS. Data Synthesis  The study was conducted following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement, and it was registered at the International Prospective Register of Systematic Reviews (PROSPERO, under number CRD42021250300). The inclusion criteria were based on the population, intervention, comparison, outcome, timing and study design (PICOTS) strategy: population - patients with VS; intervention - CK; Comparison - none; Outcome - serviceable HP defined by Gardner and Robertson as grades I or II, or by the American Academy of Otolaryngology and Head and Neck Surgery as classes A or B; timing - mean follow-up longer than 1 year; and study design - retrospective or prospective studies. The exclusion criteria were: studies not published in English; studies published before January 2000 and after October 2021; and studies only including patients with neurofibromatosis type 2 or submitted to a previous treatment. The PubMed/MEDLINE, EMBASE, Web of Science, Cochrane Library, LILACS, and IBECS databases were used and last searched on October 27th, 2021. Statistical heterogeneity was assessed using I 2 statistics. The appraisal checklist was used to assess the risk of bias in the included studies. A total of 222 studies were analyzed, and 13 were included in the synthesis, which represents 493 participants with serviceable hearing before intervention. The mean HP rate after CK using a random effects model was of 68% (95% confidence interval [95%CI]: 59-76%) at a mean follow-up of 42.96 months. Conclusion  The longer follow-up period was associated with a lower HP rate after CK radiosurgery for VS in the qualitative synthesis.

Managing vestibular schwannomas with radiosurgery and radiotherapy: AGREE II appraisal of clinical practice guidelines

INTRODUCTION

Vestibular schwannomas (VSs) are rare, benign intracranial tumours that have prompted clinical practice guideline (CPG) creation given their complex management. Our aim was to utilize the Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument to assess if such CPGs on the management of VSs with radiosurgery and radiotherapy are of acceptable quality.

METHODS

Relevant CPGs were identified following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocols. Experienced reviewers then extracted general CPG properties and rated their quality via the AGREE II instrument. Intraclass correlation coefficients (ICCs) were quantified to assess interrater reliability.

RESULTS

Nine CPGs on the management of VSs with radiosurgery and radiotherapy were identified. All CPGs were created in the past six years and developed recommendations based on literature review and expert consensus. One guideline was deemed as high quality with seven others being moderate and one being low in quality. The clarity of the presentation domain had the highest mean scaled domain score of 96.0%. The domains of stakeholder involvement and applicability had the lowest means of 49.2% and 47.2%, respectively. ICCs were either good or excellent across all domains.

CONCLUSION

Current CPGs on the management of VSs with radiosurgery and radiotherapy are of acceptable quality but would greatly benefit from improvements in applicability, stakeholder involvement, editorial independence and rigour of development. We recommend CPG authors reference the European Association of Neuro-Oncology (EANO) guideline as a developmental framework with the Congress of Neurological Surgeons/American Association of Neurological Surgeons (CNS/AANS) CPG being a valid alternative.

Vestibular Schwannoma and Tinnitus: A Systematic Review of Microsurgery Compared to Gamma Knife Radiosurgery

Background: Vestibular schwannoma (VS) is a benign tumor of the eighth cranial nerve formed from neoplastic Schwann cells. Although VS can cause a variety of symptoms, tinnitus is one of the most distressing symptoms for patients and can greatly impact quality of life. The objective of this systematic review is to comprehensively examine and compare the outcomes related to tinnitus in patients undergoing treatment for VS. Specifically, it evaluates patient experiences with tinnitus following the removal of VS using the various surgical approaches of traditional surgical resection and gamma knife radiosurgery (GKS). By delving into various aspects such as the severity of tinnitus post-treatment, the duration of symptom relief, patient quality of life, new onset of tinnitus after VS treatment, and any potential complications or side effects, this review aims to provide a detailed analysis of VS treatment on tinnitus outcomes. Methods: Following PRISMA guidelines, articles were included from PubMed, Science Direct, Scopus, and EMBASE. Quality assessment and risk of bias analysis were performed using a ROBINS-I tool. Results: Although VS-associated tinnitus is variable in its intensity and persistence post-resection, there was a trend towards a decreased tinnitus burden in patients. Irrespective of the surgical approach or the treatment with GKS, there were cases of persistent or worsened tinnitus within the studied cohorts. Conclusion: The findings of this systematic review highlight the complex relationship between VS resection and tinnitus outcomes. These findings underscore the need for individualized patient counseling and tailored treatment approaches in managing VS-associated tinnitus. The findings of this systematic review may help in guiding clinicians towards making more informed and personalized healthcare decisions. Further studies must be completed to fill gaps in the current literature.

Novel standardized indexes of brainstem auditory evoked potentials for predicting hearing preservation in vestibular schwannomas

Hearing preservation (HP) during vestibular schwannomas (VSs) surgery poses a significant challenge. Although brainstem auditory evoked potentials (BAEPs) on the affected side are commonly employed to monitor cochlear nerve function, their low signal-to-noise ratio (SNR) renders them susceptible to interferences, compromising their reliability. We retrospectively analyzed the data of patients who underwent tumor resection, while binaural brainstem auditory evoked potentials (BAEPs) were simultaneously recorded during surgery. To standardize BAEPs on the affected side, we incorporated the synchronous healthy side as a reference (interval between affected and healthy side ≤ 3 min). A total of 127 patients were enrolled. Comparison of the raw BAEPs data pre- and post-tumor resection revealed that neither V-wave amplitude (Am-V) nor latency (La-V) could serve as reliable predictors of HP simultaneously. However, following standardization, V-wave latency (STIAS-La-V) and amplitude (STIAS-Am-V) emerged as stable predictors of HP. Furthermore, the intraoperative difference in V-wave amplitude (D-Am-V) predicted postoperative HP in patients with preoperative HP and remained predictive after standardization. The utilization of intraoperative synchronous healthy side BAEPs as a reference to eliminate interferences proves to be an effective approach in enhancing the reliability of BAEPs for predicting HP in VSs patients.

Identifying Tumor Microenvironment Biomarkers in Adherent and Cystic Vestibular Schwannomas

OBJECTIVE

A subset of vestibular schwannomas (VSs), including cystic tumors, have higher postoperative morbidity because of the presence of adhesions between the tumor, facial nerve (FN), and brainstem. We identify tumor microenvironment (TME) biomarkers to better classify these tumors and predict the degree of tumor adherence.

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary skull base referral center.

METHODS

Adult patients with cystic and solid VS matched in tumor size who underwent surgical resection were included. Expressions of seven biomarkers of extracellular matrix remodeling and tumor immune response were quantified via immunohistochemistry. The distribution of CD45+ immune cells was evaluated in intratumoral and perivascular compartments. The degree of tumor adherence was categorized as none, adherent to FN, or adherent to both FN and brainstem.

RESULTS

Twenty-eight patients were included. Cystic VSs were significantly more adherent than solid VSs ( p = 0.02). Patients with adherent VS had shorter duration of symptoms and were more likely to undergo subtotal resection. In solid tumors, matrix metalloproteinase (MMP)-2 expression ( p = 0.02) and CD163+ macrophage infiltration ( p = 0.007) were correlated with tumor size. Linear discriminant analyses (LDAs) demonstrated MMP-2, MMP-14, CD80, CD163, and perivascular CD45 to be individually predictive of the degree of tumor adherence (all p < 0.05), with perivascular CD45 being the best independent predictor ( p = 0.005). An LDA model including these biomarkers demonstrated 100% accurate discrimination of all three levels of tumor adherence ( p = 0.04).

CONCLUSIONS

Adherent VS have a distinct proinflammatory TME characterized by elevated MMP expression, enrichment of tumor-associated macrophages, and perivascular immune cell infiltration.

Single-cell multi-omic analysis of the vestibular schwannoma ecosystem uncovers a nerve injury-like state

Vestibular schwannomas (VS) are benign tumors that lead to significant neurologic and otologic morbidity. How VS heterogeneity and the tumor microenvironment (TME) contribute to VS pathogenesis remains poorly understood. In this study, we perform scRNA-seq on 15 VS, with paired scATAC-seq (n = 6) and exome sequencing (n = 12). We identify diverse Schwann cell (SC), stromal, and immune populations in the VS TME and find that repair-like and MHC-II antigen-presenting SCs are associated with myeloid cell infiltrate, implicating a nerve injury-like process. Deconvolution analysis of RNA-expression data from 175 tumors reveals Injury-like tumors are associated with larger tumor size, and scATAC-seq identifies transcription factors associated with nerve repair SCs from Injury-like tumors. Ligand-receptor analysis and in vitro experiments suggest that Injury-like VS-SCs recruit myeloid cells via CSF1 signaling. Our study indicates that Injury-like SCs may cause tumor growth via myeloid cell recruitment and identifies molecular pathways that may be therapeutically targeted.

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.

Comparison of Postoperative Outcomes in Cystic Versus Solid Vestibular Schwannoma in a Multi-institutional Cohort

OBJECTIVE

Cystic vestibular schwannomas (cVSs) have more variable and less favorable clinical outcomes after microsurgical resection compared with solid VS (sVS). This study compares the preoperative presentation and postoperative outcomes between cVS and sVS.

STUDY DESIGN

Retrospective cohort study.

SETTING

Two tertiary skull base referral centers.

METHODS

Consecutive adult patients who underwent VS resection from 2016 to 2021 were included. Univariate and multivariate analyses compared differences in baseline symptoms and postoperative outcomes between cVS and sVS.

RESULTS

There were a total of 315 patients (64% female; mean age, 54 yrs) and 46 (15%) were cystic. cVS were significantly larger than sVS (maximum diameter, 28 vs. 18 mm, p < 0.001) and had higher rates of dysphagia and dysphonia preoperatively (p < 0.02). cVSs were more likely to undergo translabyrinthine resection (76 vs. 50%, p = 0.001) and have a higher rate of subtotal resection (STR) compared with sVS (30 vs. 13%, p = 0.003). At latest follow-up, fewer cVS achieved good facial nerve (FN) outcome (House-Brackmann [HB] I/II) (80 vs. 90%, p = 0.048). Subanalysis of cVS and sVS matched in tumor size, and surgical approach did not show differences in the rate of STR or FN outcomes (HB I/II, 82 vs. 78%, p = 0.79).

CONCLUSION

In this large multi-institutional series, cVSs represent a distinct entity and are characterized by larger tumor size and higher incidence of atypical symptoms. Although cVSs were more likely to undergo STR and portend worse FN outcomes than sVSs, this may be due to their larger tumor size rather than the presence of the cystic component.

A Case of Vestibular Schwannoma with Deafness Showing Remarkable Hearing Recovery Following Hearing-Preserving Surgery

Surgery for vestibular schwannoma can be divided into hearing-preserving and nonhearing-preserving surgeries. Hearing-preserving surgery is usually not considered in patients with deafness due to vestibular schwannoma, because hearing is unlikely to improve, and surgery aims to maximize the tumor resection at the expense of hearing. We report an extremely rare case of a 46-year-old man with unilateral profound hearing loss due to a vestibular schwannoma with marked cystic degeneration in the left cistern, which significantly recovered to near-normal hearing levels after hearing-preserving surgery. Hearing loss gradually worsened, and preoperative pure-tone evaluation showed complete hearing loss in the left ear. However, the response to the distortion product otoacoustic emission was preserved, and hearing loss was considered to be retrocochlear. Tumor resection was performed using the retrolabyrinthine approach with continuous monitoring using dorsal cochlear nucleus action potential, auditory brainstem response, and facial nerve function muscle action potential. The cistern portion of the tumor was almost completely resected along with the wall. Postoperatively, the pure-tone threshold on the left side markedly improved. The present case clearly demonstrates the possibility of hearing recovery in patients with retrocochlear hearing loss. We should consider expanding the indications for hearing-preserving surgery.

Stratifying Risk of Future Growth Among Sporadic Vestibular Schwannomas

OBJECTIVE

In certain cases, clinicians may consider continued observation of a vestibular schwannoma after initial growth is detected. The aim of the current work was to determine if patients with growing sporadic vestibular schwannomas could be stratified by the likelihood of subsequent growth based on initial growth behavior.

STUDY DESIGN

Slice-by-slice volumetric tumor measurements from 3,505 serial magnetic resonance imaging studies were analyzed from 952 consecutively treated patients.

SETTING

Three tertiary-referral centers.

PATIENTS

Adults with sporadic vestibular schwannoma.

INTERVENTIONS

Wait-and-scan.

MAIN OUTCOME MEASURES

Composite end point of subsequent growth- or treatment-free survival rates, where growth is defined as an additional increase of at least 20% in tumor volume from the volume at the time of initial growth.

RESULTS

Among 405 patients who elected continued observation despite documented growth, stratification, of volumetric growth rate into less than 25% (reference: n = 107), 25 to less than 50% (hazard ratio [HR], 1.39; p = 0.06; n = 96), 50 to less than 100% (HR, 1.71; p = 0.002; n = 112), and at least 100% (HR, 2.01; p < 0.001; n = 90) change per year predicted the likelihood of future growth or treatment. Subsequent growth- or treatment-free survival rates (95% confidence interval) at year 5 after detection of initial growth were 31% (21-44%) for those with less than 25% growth per year, 18% (10-32%) for those with 25 to less than 50%, 15% (9-26%) for those with 50 to less than 100%, and 6% (2-16%) for those with at least 100%. Neither patient age (p = 0.15) nor tumor volume at diagnosis (p = 0.95) significantly differed across stratification groups.

CONCLUSIONS

At the time of diagnosis, clinical features cannot consistently predict which tumors will ultimately display aggressive behavior. Stratification by volumetric growth rate at the time of initial growth results in a stepwise progression of increasing likelihood of subsequent growth. When considering continued observation after initial growth detection, almost 95% of patients who have tumors that double in volume between diagnosis and the first detection of growth demonstrate further tumor growth or undergo treatment if observed to 5 years.

Epidemiology and Risk Factors for Development of Sporadic Vestibular Schwannoma

Vestibular schwannomas (VSs) are benign, slow-growing tumors of the eighth cranial nerve. Sporadic unilateral VSs constitute approximately 95% of all newly diagnosed tumors. There is little known about risk factors for developing sporadic unilateral VS. Potential risk factors that have been reported are familial or genetic risk, noise exposure, cell phone use, and ionizing radiation, whereas protective factors may include smoking and aspirin use. More research is needed to elucidate the risk factors for development of these rare tumors.

Introducing an Evidence-Based Approach to Wait-And-Scan Management of Sporadic Vestibular Schwannoma

The advent of MRI has led to more sporadic vestibular schwannomas diagnosed today than ever before. Despite the average patient being diagnosed in their sixth decade of life with a small tumor and minimal symptoms, population-based data demonstrate that more tumors per capita are treated today than ever before. Emerging natural history data justify either an upfront treatment approach or the "Size Threshold Surveillance" approach. Specifically, if the patient elects to pursue observation, then existing data support the tolerance of some growth during observation in appropriately selected patients up until a specific size threshold range (about 15 mm of CPA extension). The current article discusses the rationale behind a shift in the existing observation management approach, where initial detection of growth typically begets treatment, and outlines the application of a more flexible and nuanced approach based on existing evidence.

Quality of Life in Sporadic Vestibular Schwannoma

The focus of management in sporadic vestibular schwannoma has dramatically evolved over the last 100 years. The centrality of quality of life (QoL) is being underscored by an ongoing epidemiologic shift toward an older patient demographic that is being diagnosed with smaller tumors and often with few associated symptoms. Two disease-specific QoL instruments have been developed for sporadic vestibular schwannoma: the Penn Acoustic Neuroma Quality of Life Scale in 2010, and more recently, the Mayo Clinic Vestibular Schwannoma Quality of Life Index in 2022. The current article examines disease-specific quality-of-life outocmes in the management of ssporadic vestibular schwannoma.

Preservation of the integrity of facial nerve in vestibular schwannoma microsurgery: A consecutive study of 127 clinical cases focusing on nervus intermedius

Background

Nervus intermedius (NI) injuries are not given enough attention by neurosurgeons during vestibular schwannoma (VS) surgery. Preservation of NI function is essential for the integrity and continuity of the facial nerve, although this can be challenging. We identified the risk factors for NI injury and proposed our experience for optimizing NI preservation based on our cases.

Methods

We retrospectively analyzed clinical data from a consecutive series of 127 patients with VS who underwent microsurgery via the retrosigmoid approach from 2017 to 2021 at our institution. The baseline characteristics of the patients were collected from the medical records, and the incidence of NI dysfunction symptoms was obtained by outpatient and online video follow-up 6 months after surgery. The surgical procedures and techniques used were described in detail. The data were analyzed in relation to sex, age, tumor location (left or right), Koos grading scale, internal acoustic canal (IAC) invasion (TFIAC Classification), brainstem adhesion, tumor characteristics (cystic or solid), tumor necrosis, and preoperative House-Brackmann (HB) grading by univariate and multivariate analyses.

Results

Gross tumor removal was achieved in 126 (99.21%) patients. Subtotal removal was performed on one patient (0.79%). Twenty-three of our cases exhibited facial nerve palsy preoperatively; 21 patients had HB grade II facial palsy, and two had HB grade III. Two months after surgery, 97 (76.38%) patients had normal function of the motor portion of the facial nerve; 25 (19.69%) patients had HB Grade II facial palsy, five had Grade III (3.94%), and zero (0%) had Grade IV. Postoperatively, 15 patients experienced newly gained dry eyes (11.81%), whereas 21 cases of lacrimal disturbances (16.54%), nine of taste disturbances (7.09%), seven of xerostomia (5.51%), five of nasal hypersecretions (3.94%), and seven of hypersalivation (5.51%) were identified in our cases. Univariate and multivariate analyses revealed that the Koos grading scale and tumor characteristics (solid or cystic) were correlated with NI injury (p <0.01).

Conclusion

The data in this study demonstrate that although the motor function of the facial nerve is well preserved, NI disturbance is still common after VS surgery. Maintaining the integrity and continuity of the facial nerve is key to NI function. Performing bidirectional and subperineurium dissection based on even and adequate debulking is beneficial for NI preservation in VS surgery. Higher Koos grading and cystic characteristics of VS are associated with postoperative NI injuries. These two parameters can be used to guide the delineation of surgical strategy and predict the prognosis of NI function preservation.

Genetic variants of cancer‑associated genes analyzed using next‑generation sequencing in small sporadic vestibular schwannomas

Vestibular schwannoma (VS) is the most common tumor of the cerebellopontine angle. Despite the increasing diagnosis of sporadic VS over the past decade, the use of traditional microsurgeries to treat VS has decreased. This is likely a result of the adoption of serial imaging as the most common initial evaluation and treatment strategy, especially for small-sized VS. However, the pathobiology of VSs remains unclear, and elucidating the genetic information of tumor tissue may reveal novel insights. The present study performed a comprehensive genomic analysis of all exons in the key tumor suppressor and oncogenes from 10 small (<15 mm) sporadic VS samples. The evaluations identified NF2, SYNE1, IRS2, APC, CIC, SDHC, BRAF, NUMA1, EXT2, HRAS, BCL11B, MAGI1, RNF123, NLRP1, ASXL1, ADAMTS20, TAF1L, XPC, DDB2 and ETS1 as mutated genes. The current study could not draw any new conclusions about the relationship between VS-related hearing loss and gene mutations; however, it did reveal that NF2 was the most frequently mutated gene in small sporadic VS.

RAD51 Inhibitor and Radiation Toxicity in Vestibular Schwannoma

OBJECTIVE

To describe the RAD51 response (DNA repair) to radiation-induced DNA damage in patient-derived vestibular schwannoma (VS) cells and investigate the utility of RAD51 inhibitor (RI-1) in enhancing radiation toxicity.

STUDY DESIGN

Basic and translational science.

SETTING

Tertiary academic facility.

METHODS

VS tumors (n = 10) were cultured on 96-well plates and 16-well slides, exposed to radiation (0, 6, 12, or 18 Gy), and treated with RI-1 (0, 5, or 10 µM). Immunofluorescence was performed at 6 hours for γ-H2AX (DNA damage marker), RAD51 (DNA repair protein), and p21 (cell cycle arrest protein). Viability assays were performed at 96 hours, and capillary Western blotting was utilized to determine RAD51 expression in naïve VS tumors (n = 5).

RESULTS

VS tumors expressed RAD51. In cultured VS cells, radiation initiated dose-dependent increases in γ-H2AX and p21 expression. VS cells upregulated RAD51 to repair DNA damage following radiation. Addition of RI-1 reduced RAD51 expression in a dose-dependent manner and was associated with increased γ-H2AX levels and decreased viability in a majority of cultured VS tumors.

CONCLUSION

VS may evade radiation injury by entering cell cycle arrest and upregulating RAD51-dependent repair of radiation-induced double-stranded breaks in DNA. Although there was variability in responses among individual primary VS cells, RAD51 inhibition with RI-1 reduced RAD51-dependent DNA repair to enhance radiation toxicity in VS cells. Further investigations are warranted to understand the mechanisms of radiation resistance in VS and determine whether RI-1 is an effective radiosensitizer in patients with VS.

Factors Influencing Personalized Management of Vestibular Schwannoma: A Systematic Review

Management of vestibular schwannoma (VS) is a complex process aimed at identifying a clinical indication for fractionated stereotactic radiotherapy (sRT) or microsurgical resection or wait and scan (WS). The aim of the review was to clarify which patient and tumor parameters may lead to different therapeutic choices, with a view to a personalized VS approach. A systematic review according to Preferred Reporting Items for Systematic Review and Meta-Analysis criteria was conducted between February and March 2022. The authors defined six parameters that seemed to influence decision-making in VS management: 1-incidental VS; 2-tumor size; 3-tumor regrowth after sRT; 4-subtotal resection; 5-patients' age; 6-symptoms. The initial search yielded 3532 articles, and finally, 812 articles were included. Through a qualitative synthesis of the included studies, management strategies were evaluated and discussed. An individualized proposal of procedures is preferable as compared to a single gold-standard approach in VS decision-making. The most significant factors that need to be considered when dealing with a VS diagnosis are age, tumor size and hearing preservation issues.

Development and validation of a new disease-specific quality of life instrument for sporadic vestibular schwannoma: the Mayo Clinic Vestibular Schwannoma Quality of Life Index

OBJECTIVE

Facial nerve function, hearing preservation, and tumor control have been the primary benchmarks used to assess vestibular schwannoma (VS) outcomes. Acknowledging the frequent discrepancy between what physicians prioritize and what patients value, there has been increasing prioritization of patient-reported outcome measures when evaluating the impact of VS diagnosis and its treatment. Motivated by reported limitations of prior instruments used to assess quality of life (QOL) in patients with VS, the authors describe the development and validation of a new disease-specific QOL measure: the Vestibular Schwannoma Quality of Life (VSQOL) Index.

METHODS

The content development phase comprised identification of clinically important domains and prioritization of feelings or concerns individuals with VS may have. The validation phase encompassed determining how items were grouped into domains and eliminating redundant items. Both phases leveraged data from cross-sectional and longitudinal surveys, expertise from a multidisciplinary working group, and patients with a broad range of experiences with VS (n = 42 during content development and n = 263 during validation). Domain scores from the new instrument were assessed for reliability and correlation with other measures of similar constructs.

RESULTS

The VSQOL Index consists of 40 items that evaluate the impact of VS diagnosis and its management on QOL, treatment satisfaction, and employment and is estimated to take 8-10 minutes to complete. Domain scores range from 0 (worst) to 100 (best) and demonstrate excellent psychometric properties, including content, construct, and convergent validity and both internal consistency (Cronbach's alphas 0.83 to 0.91) and test-retest reliability (reliability coefficients 0.86 to 0.96).

CONCLUSIONS

The VSQOL Index is a valid and reliable measure that overcomes several limitations of prior instruments, including omission or underrepresentation of domains that frequently impact well-being, such as pain, cognition, satisfaction or regret surrounding treatment decisions, and occupational limitations, to comprehensively evaluate the impact of VS diagnosis or its treatment on QOL.

Hearing Preservation in Observed Sporadic Vestibular Schwannoma: A Systematic Review

OBJECTIVE

To characterize the natural history of hearing loss for patients presenting with serviceable hearing (SH) who undergo a wait-and-scan approach for sporadic vestibular schwannoma (VS) using aggregate time-to-event survival analysis.

STUDY DESIGN

Systematic review.

SETTING

Published international English literature, January 1, 2000 to May 31, 2020.

PATIENTS

Patients with sporadic VS entering a wait-and-scan approach with SH at diagnosis.

INTERVENTIONS

Observation with serial MRI and audiometry.

RESULTS

In total, 3,652 patients from 26 studies were included for analysis. Mean age at diagnosis was 58.8 years (SD, 4.1). Mean follow-up was 49.2 months (SD, 26.5). In total, 755 patients (21%) failed conservative treatment and underwent radiosurgery or microsurgery at the time of last follow-up. The average loss to follow-up was 6.9% (SD, 11.1). A total of 1,674 patients had SH at the time of diagnosis. Survival rates for maintaining SH were 96% at 1 year, 77% at 3 years, 62% at 5 years, and 42% at 10 years following diagnosis.

CONCLUSION

In this systematic review, aggregate data from 3,652 patients across 26 studies show consistent patterns in progression of hearing loss during observation for patients with sporadic VS as a function of time. As an easy-toremember conservative benchmark for those presenting with SH at diagnosis: approximately 75% retain SH at 3 years, 60% at 5 years, and 40% at 10 years.

[Vestibular schwannomas - baseline and progress diagnostics]

Vestibular (vestibulocochlear) schwannomas are rare, benign schwannomas of the cerebellopontine angle, the internal auditory canal, or the inner ear. They can occur with or without clinical symptoms. The most common symptoms are unilateral or side-differentiated hearing loss with or without tinnitus and balance disorders. Initial symptomatology is nonspecific in the basic functional diagnosis, raising the question of when a hearing or balance disorder should be thought of as a differential diagnosis of vestibular schwannoma and what diagnostic pathway is appropriate. This concerns not only the confirmation of the diagnosis and the recording of all dysfunctions of the involved cranial nerves in the initial basic diagnostics, but also the procedure in the course and follow-up diagnostics - especially in patients who are subject to an observation strategy. Today, imaging alone is no longer sufficient for differentiated and individualized patient counseling. Due to the increasing detection of smaller tumors on MRI and the growing proportion of nearly asymptomatic patients, a shift in thinking from pure imaging monitoring to a detailed analysis of auditory and vestibular function is timely. In this educational article, diagnostic pathways for a sufficient patient consultation will be compiled. Ultimately, functional examination techniques from follow-up and progression diagnostics will also be included.

Understanding the Molecular Mechanism of Vestibular Schwannoma for Hearing Preservation Surgery: Otologists’ Perspective from Bedside to Bench

Vestibular schwannoma is a clinically benign schwannoma that arises from the vestibulocochlear nerve that causes sensorineural hearing loss. This tumor is clinically and oncologically regarded as a benign tumor as it does not metastasize or invade surrounding tissues. Despite being a benign tumor, its management is difficult and controversial due to the potential serious complications, such as irreversible sensorineural hearing loss, of current interventions. Therefore, preventing hearing loss due to the natural course of the disease and complications of surgery is a challenging issue for an otologist. Improvements have been reported recently in the treatment of vestibular schwannomas. These include advances in intraoperative monitoring systems for vestibular schwannoma surgery where the risk of hearing loss as a complication is decreased. Precise genomic analysis of the tumor would be helpful in determining the characteristics of the tumor for each patient, leading to a better hearing prognosis. These procedures are expected to help improve the treatment of vestibular schwannomas. This review summarizes recent advances in vestibular schwannoma management and treatment, especially in hearing preservation. In addition, recent advances in the understanding of the molecular mechanisms underlying vestibular schwannomas and how these advances can be applied in clinical practice are outlined and discussed, respectively. Moreover, the future directions from the bedside to the bench side are presented from the perspective of otologists.

A Subset of Intracanalicular Vestibular Schwannomas Demonstrates Minimal Growth Over a 10-Year Period

OBJECTIVE

Vestibular schwannomas (VS) commonly undergo magnetic resonance imaging (MRI) surveillance, but long-term data to support the ideal frequency is limited. Herein, we aim to investigate intracanalicular VS growth predictors and long-term growth rates (GR).

STUDY DESIGN

Retrospective chart review.

SETTING

Two tertiary care centers.

PATIENTS

Sporadic intracanalicular VS with initial conservative management and at least two sequential MRIs.

INTERVENTION

Serial MRI.

MAIN OUTCOME MEASURES

VS were categorized by baseline internal auditory canal tertile sublocalization (fundus, midpoint, porus) and size (≤100, 100-200, >200 mm3). Throughout follow-up, volumetric GR (mm3/yr) were determined (baseline-3 yrs, 3-5 yrs, 5-10 yrs) and treatment rates were assessed.

RESULTS

Ninety-nine intracanalicular VS were identified (mean follow-up of 6.1 ± 4.5 yrs). Mean GR before 5-year follow-up were comparable for baseline tertile involvement and size. After 5-year follow-up, mean GR of VS involving the fundus at baseline were lower than those involving the midpoint and fundus (6.17 ± 21.16 and 119.74 ± 117.57 mm3/yr, respectively; p = 0.034). Mean GR of VS with less than or equal to 100 mm3 at baseline (-7.29 ± 25.44 mm3/yr) were lower than those with 100 to 200 mm3 (86.55 ± 103.99 mm3/yr; p = 0.011) and more than 200 mm3 (45.70 ± 35.71 mm3/yr; p = 0.031). Vestibular schwannomas involving the midpoint and fundus had greater treatment rates compared with VS involving only the fundus (p < 0.001).

CONCLUSIONS

Baseline tertile involvement and size may predict long-term intracanalicular VS growth where fundal tumors or those less than or equal to 100 mm3 exhibit little long-term growth. Extending surveillance after 5-year follow-up may be reasonable for fundal VS.

Long non-coding RNA BRCAT54 sponges microRNA-21 in vestibular schwannoma to suppress cell proliferation

BRCAT54 (also known as MRPS30 divergent transcript) is an anti-tumor long non-coding RNA (lncRNA) in lung cancer, while its role in vestibular schwannoma (VS) is unclear. We predicted that BRCAT54 could interact with microRNA (miR)-21, which suppresses VS cell proliferation. This study was then carried out to study the interaction between BRCAT54 and miR-21 in VS. A total of 56 VS samples and 42 normal vestibular nerve (VN) samples were included in this study. The expression of BRCAT54 and miR-21 in these samples were analyzed with RT-qPCR. Subcellular location of BRCAT54 in primary VS cells was analyzed by subcellular fractionation assay. The direct interaction between BRCAT54 and miR-21 was analyzed through RNA pull-down assay. Overexpression assay was performed to explore the interaction between BRCAT54 and miR-21. The role of BRCAT54 and miR-21 in primary VS cell proliferation was analyzed using BrdU assay. We found that BRCAT54 was downregulated in VS samples than that in VN samples, while miR-21 was upregulated in VS samples. BRCAT54 and miR-21 were not closely correlated. BRCAT54 was detected in both nuclear and cytoplasm samples, and BRCAT54 directly interacted with miR-21. However, BRCAT54 and miR-21 did not affect the expression of each other. BRCAT54 suppressed primary VS cell proliferation and inhibited the role of miR-21 in promoting cell proliferation. Therefore, BRCAT54 may sponge miR-21 to suppress cell proliferation in VS.

The Role of Endoscopy in the Resection of Sporadic Vestibular Schwannomas: A Systematic Review of Surgical Outcomes

BACKGROUND

Vestibular schwannomas (VS) are benign intracranial tumors originating from the vestibular division of the eighth cranial nerve. Treatment options include microsurgery, radiotherapy, and surveillance. Endoscopy is becoming more widely used as an adjunct in skull base surgery and may influence outcomes in surgically managed VS.

METHODS

A systematic review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies involving endoscope-assisted and fully endoscopic procedures for sporadic VS resection were identified. Facial nerve function, hearing preservation, extent of resection, and complications were analyzed.

RESULTS

Thirty-one studies were included (27 endoscope-assisted, four fully endoscopic). Subgroup analyses were performed to assess outcomes according to tumor size and surgical approach. Overall, endoscopic facial nerve preservation rates were comparable to microsurgical treatment. A subgroup analysis suggested that functional facial nerve preservation rates may be higher when endoscopic assistance is used for smaller (Koos I-II) tumors using the retrosigmoid or translabyrinthine approach. The gross total resection rate for small tumors was higher in retrosigmoid ES-assisted microsurgery (96.2%) compared to rates in the literature for the standard, open retrosigmoid approach. Hearing outcomes were more variable and were under-reported.

CONCLUSIONS

Current data suggest that ES-assisted resection of sporadic VS is not inferior to microsurgical resection with respect to facial nerve outcomes and extent of resection. However, some ES series report poor hearing outcomes, which are under-reported in the literature. Further prospective studies are required to ascertain if endoscopic assistance can improve outcomes for VS resection, particularly for smaller (Koos I-II) tumors.

Changes in pattern of presentation of patients with unilateral vestibular schwannoma over two decades: Influence of cell phone use in early diagnosis

We aimed to study whether the increased use of cell phone in south Asia over the past two decades has impacted presentation of patients with vestibular schwannoma (VS). In this observational cohort study, data on cell phone use and severity of hearing loss and tumor size was collected using a questionnaire through a patient interview (n = 62) in consecutive patients with VS managed between 2017 and 2020. Association between cell phone use and severity of hearing loss and tumor size were studied and compared with our data published earlier when telephone use was not widely prevalent. 71% of the 62 patients (aged between 15 and 81 years) had large or giant VS. Pure tone audiometry showed moderately severe or profound hearing loss in77.4%. Sixty (96.7%) patients used cell phones. 50% of patients complained of difficulty in using their cell phone because of hearing loss. Compared to the earlier era, a higher proportion consulted an ENT surgeon first for hearing loss (59.7% vs 26%; p = 0.0005) and had small or medium sized tumors (29% vs 8%; p = 0.008) with a smaller mean tumor size (3.3 vs 3.9 cm; p = 0.03). Increased cell phone use has led to earlier diagnosis of VS and smaller tumours in recent years when compared to an earlier era. However, the vast majority of patients continue to present with severe to profound hearing loss and large tumors.

Understanding the Radiobiology of Vestibular Schwannomas to Overcome Radiation Resistance

Vestibular schwannomas (VS) are benign tumors arising from cranial nerve VIII that account for 8-10% of all intracranial tumors and are the most common tumors of the cerebellopontine angle. These tumors are typically managed with observation, radiation therapy, or microsurgical resection. Of the VS that are irradiated, there is a subset of tumors that are radioresistant and continue to grow; the mechanisms behind this phenomenon are not fully understood. In this review, the authors summarize how radiation causes cellular and DNA injury that can activate (1) checkpoints in the cell cycle to initiate cell cycle arrest and DNA repair and (2) key events that lead to cell death. In addition, we discuss the current knowledge of VS radiobiology and how it may contribute to clinical outcomes. A better understanding of VS radiobiology can help optimize existing treatment protocols and lead to new therapies to overcome radioresistance.

Global Incidence of Sporadic Vestibular Schwannoma: A Systematic Review

OBJECTIVE

Ubiquitous throughout the literature and during patient counseling, vestibular schwannoma is often quoted to affect about 1 per 100,000 people. Yet, reports from distinct international populations suggest that the incidence is likely much higher. The objective of the current work was to systematically characterize the global incidence of sporadic vestibular schwannoma.

DATA SOURCES

Scopus, Embase, and PubMed.

REVIEW METHODS

Population-based studies reporting incidence rates of sporadic vestibular schwannoma between January 2010 and August 2020 were searched with language restrictions requiring reports to be published in Chinese, English, German, Italian, or Spanish. The protocol was registered with PROSPERO (CRD42021228208) prior to commencement of data collection. PRISMA guidelines for transparent reporting of systematic reviews were followed.

RESULTS

Among 424 citations, 6 publications covering 4 distinct populations from Denmark, the Netherlands, Taiwan, and the United States met inclusion criteria. Most recent incidence rates of among all ages ranged between 3.0 and 5.2 per 100,000 person-years. Highest incidence rates were reported among patients aged ≥70 years, peaking at 20.6 per 100,000 person-years. One study from the United States reported the incidence of asymptomatic, incidentally diagnosed tumors at a rate of 1.3 per 100,000 person-years from 2012 to 2016.

CONCLUSIONS

Recent international incidence rates of sporadic vestibular schwannoma exceed the commonly quoted "1 per 100,000" figure by up to 5-fold among all ages and by up to 20-fold among age groups at highest risk. Based on modern incidence rates, the lifetime prevalence of developing sporadic vestibular schwannoma likely exceeds 1 per 500 persons.

Defining current practice patterns of vestibular schwannoma management in Italy: results of a nationwide survey

Objective

Despite the increasing incidence rate of vestibular schwannomas (VS), controversies in their management are still present.

Methods

A 35-item multiple-choice survey investigating the current practice patterns of VS care was sent to the members of the Italian Society of Otolaryngology, Head and Neck Surgery (SIO) and of the Italian Society of Neurosurgery (SINCH).

Results

Among 66 respondents, 37 (56.0%) claimed to be actively involved in VS management. Most interviewees (35.1%) declared > 20 years of experience and 59.5% claimed to work in an academic practice. The number of cases evaluated in each centre per year varied widely, with 54.0% evaluating > 25 cases/year and only 13.6% > 100 cases/year. Multidisciplinary care for VS evaluation was confirmed by 50.0% of respondents, and multidisciplinary surgical care by 62.2%. Observation and surgery were the most common management options proposed. Further details regarding VS care are presented.

Conclusions

The present study provides the first overview on the current practice patterns of VS care in Italy. Although integrated in most centres, a multidisciplinary model of care needs to be encouraged. Wide heterogeneity in experience and practices is mostly influenced by the surgeon’s different specialties and by the lack of shared guidelines.

Large and small vestibular schwannomas: same, yet different tumors

BACKGROUND

Vestibular schwannomas (VS) present at variable size with heterogeneous symptomatology. Modern treatment paradigms for large VS include gross total resection, subtotal resection (STR) in combination with observation, and/or radiation to achieve optimal function preservation, whereas treatment is felt to be both easier and safer for small VS. The objective is to better characterize the presentation and surgical outcomes of large and small VS.

METHODS

We collected data of patients who had surgically treated VS with a posterior fossa diameter of 4.0 cm or larger (large tumor group, LTG) and smaller than 1.0 cm in cisternal diameter (small tumor group, STG). Statistical significance was defined as p < 0.05.

RESULTS

LTG included 48 patients (average tumor size: 44.9 mm) and STG 38 (7.9 mm). Patients in STG presented more frequently with tinnitus and sudden hearing loss. Patients in LTG underwent more STR than STG (50.0% vs. 2.6%, p < 0.0001). LTG had more complications (31.3% vs. 13.2%, p = 0.049). Postoperative facial nerve function in STG was significantly better than LTG. STG had better hearing preoperatively (p < 0.0001) and postoperatively than LTG (p = 0.0002). Postoperative headache was more common in STG (13.2% vs. 2.1%, p = 0.045). The rate of recurrence/progression needing treatment was not statistically different between the groups (12.5% in LTG vs. 7.9% in STG, p = 0.49). Those patients who required periprocedural cerebrospinal fluid diversion had higher risk of infection (20.8% vs 4.8%, p = 0.022).

CONCLUSION

Large and small VS present differently. LTG showed more unsatisfactory outcomes in facial nerve function and postoperative hearing despite maximal efforts undertaken toward function-preservation strategy; however, similar tumor control was achieved.

Pre-existing Vestibular Symptoms Are Associated With Acute Vestibular Symptoms After Gamma Knife Therapy for Vestibular Schwannoma

OBJECTIVE

To identify pretreatment variables associated with the development of acute vestibular symptoms after Gamma Knife (GK) treatment for Vestibular Schwannoma (VS).

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary neurotology referral center.

PATIENTS

Patients treated with GK radiosurgery for VS between March 2007 and March 2017 were considered for this study. Patients with neurofibromatosis type II, previous VS surgery, follow-up less than 6 months, or the lack of T2 magnetic resonance imaging (MRI) sequences from the day of treatment were excluded.

MAIN OUTCOME MEASURES

The presence of acute vestibular symptoms arising within 6 months after GK was the main outcome variable. Tumor, patient, and treatment characteristics were gathered from the medical record.

RESULTS

In total, 98 patients met inclusion criteria. The incidence of acute vestibular symptoms occurring within 6 months after GK treatment was 46.9%. Post-GK vestibular symptoms were reported at a significantly higher frequency among subjects who had reported vestibular symptoms before their treatment (p = 0.001). Tumor size was not associated with a propensity to develop acute vestibular symptoms (p = 0.397). The likelihood of receiving a referral to vestibular rehabilitation services was not significantly different among patients with larger versus smaller tumor size, as defined by 1.6 cm and 1.4 cm thresholds (p = 0.896, p = 0.654).

CONCLUSIONS

Inquiries aimed at revealing a history of vestibular complaints may prove useful in counseling patients on the likelihood of experiencing acute vestibular symptoms after treatment of Vestibular Schwannoma with Gamma Knife therapy.

Underreporting of Vestibular Schwannoma Incidence Within National Brain Tumor and Cancer Registries in the United States

OBJECTIVE

Reports using large brain tumor and cancer registries suggest that the incidence of vestibular schwannoma is considerably lower in the United States compared with other countries. The current study compares the incidence and disease characteristics of vestibular schwannoma within a large tertiary referral center's brain tumor and cancer registry using nationally mandated reporting protocols to disease incidence in the same population using an externally validated population-based consortium.

STUDY DESIGN

Population-based study spanning 1,945,007 person-years.

SETTING

Large tertiary referral center.

PATIENTS

Adults with sporadic vestibular schwannoma.

MAIN OUTCOME MEASURE

Disease incidence rates from 2004 to 2016.

RESULTS

From 2004 to 2016, the incidence of vestibular schwannoma in the tumor registry was 1.3 per 100,000 person-years whereas the population-based cohort had an incidence of 4.4 per 100,000 person-years. From 2012 to 2016, the incidence in the tumor registry was 1.4 per 100,000 person-years compared with 5.2 in the population-based cohort. Patients within the population-based cohort were significantly more likely to have smaller tumors at diagnosis (78% intracanalicular versus 45%; p = 0.004) and consequently more likely to undergo management consisting of observation with serial imaging as opposed to treatment with either microsurgery or radiosurgery (71% versus 28%; p = 0.001).

CONCLUSIONS

The reliance on pathology specimens and cancer-related treatment data for the national registration of new cancer and brain tumor diagnoses may introduce selection bias and underreporting of benign brain tumors that frequently involve observation as a primary treatment modality. This selection bias likely accounts for the discrepant incidence rates of vestibular schwannoma reported between the United States and other countries.

Phase 0 Clinical Trial of Everolimus in Patients with Vestibular Schwannoma or Meningioma

Inhibition of mTORC1 signaling has been shown to diminish growth of meningiomas and schwannomas in preclinical studies, and clinical data suggest that everolimus, an orally administered mTORC1 inhibitor, may slow tumor progression in a subset of patients with neurofibromatosis type 2 (NF2) with vestibular schwannoma. To assess the pharmacokinetics, pharmacodynamics, and potential mechanisms of treatment resistance, we performed a presurgical (phase 0) clinical trial of everolimus in patients undergoing elective surgery for vestibular schwannoma or meningiomas. Eligible patients with meningioma or vestibular schwannoma requiring tumor resection enrolled on study received everolimus 10 mg daily for 10 days immediately prior to surgery. Everolimus blood levels were determined immediately before and after surgery. Tumor samples were collected intraoperatively. Ten patients completed protocol therapy. Median pre- and postoperative blood levels of everolimus were found to be in a high therapeutic range (17.4 ng/mL and 9.4 ng/mL, respectively). Median tumor tissue drug concentration determined by mass spectrometry was 24.3 pg/mg (range, 9.2-169.2). We observed only partial inhibition of phospho-S6 in the treated tumors, indicating incomplete target inhibition compared with control tissues from untreated patients (P = 0.025). Everolimus led to incomplete inhibition of mTORC1 and downstream signaling. These data may explain the limited antitumor effect of everolimus observed in clinical studies for patients with NF2 and will inform the design of future preclinical and clinical studies targeting mTORC1 in meningiomas and schwannomas.

Natural History of Growing Sporadic Vestibular Schwannomas During Observation: An International Multi-Institutional Study

OBJECTIVE

Active treatment of small- or medium-sized vestibular schwannoma during wait-and-scan management is currently recommended at most centers globally once growth is detected. The primary aim of the current study was to characterize the natural history of growing sporadic vestibular schwannoma during observation.

STUDY DESIGN

Cohort study.

SETTING

Four tertiary referral centers across the United States and Denmark.

PATIENTS

Patients with two prior MRI scans demonstrating ≥2 mm of linear growth who continued observational management.

INTERVENTION

Observation with serial imaging.

MAIN OUTCOME MEASURE

Subsequent linear growth-free survival (i.e., an additional ≥2 mm of growth) following initial growth of ≥2 mm from tumor size at diagnosis.

RESULTS

Among 3,402 patients undergoing observation, 592 met inclusion criteria. Median age at initial growth was 66 years (IQR 59-73) for intracanalicular tumors (N = 65) and 62 years (IQR 54-70) for tumors with cerebellopontine angle extension (N = 527). The median duration of MRI surveillance following initial detection of tumor growth was 5.2 years (IQR 2.4-6.9) for intracanalicular tumors and 1.0 year (IQR 1.0-3.3) for cerebellopontine angle tumors. For intracanalicular tumors, subsequent growth-free survival rates (95% CI; number still at risk) at 1, 2, 3, 4, and 5 years following the initial MRI that demonstrated growth were 77% (67-88; 49), 53% (42-67; 31), 46% (35-60; 23), 34% (24-49; 17), and 32% (22-47; 13), respectively. For cerebellopontine angle tumors, subsequent growth-free survival rates were 72% (68-76; 450), 47% (42-52; 258), 32% (28-38; 139), 26% (21-31; 82), and 22% (18-28; 57), respectively. For every 1 mm increase in magnitude of growth from diagnosis to tumor size at detection of initial growth, the HRs associated with subsequent growth were 1.64 (95% CI 1.25-2.15; p < 0.001) for intracanalicular tumors and 1.08 (95% CI 1.01-1.15; p = 0.02) for cerebellopontine angle tumors.

CONCLUSIONS

Growth detected during observation does not necessarily portend future growth, especially for slowly growing tumors. Because early treatment does not confer improved long-term quality of life outcomes, toleration of some growth during observation is justifiable in appropriately selected cases.

Investigating Predictors of Increased Length of Stay After Resection of Vestibular Schwannoma Using Machine Learning

OBJECTIVE

To evaluate the predictors of prolonged length of stay (LOS) after vestibular schwannoma resection.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral center.

PATIENTS

Patients who underwent vestibular schwannoma resection between 2008 and 2019.

INTERVENTIONS

Variables of interest included age, body mass index, comorbidities, symptoms, previous intervention, microsurgical approach, extent of resection, operative time, preoperative tumor volume, and postoperative complications. Predictive modeling was done through multivariable linear regression and random forest models with 80% of patients used for model training and the remaining 20% used for performance testing.

MAIN OUTCOME MEASURES

LOS was evaluated as the number of days from surgery to discharge.

RESULTS

Four hundred one cases from 2008 to 2019 were included with a mean LOS of 3.0 (IQR = 3.0-4.0). Postoperatively, 14 (3.5%) of patients had LOS greater than two standard deviations from the mean (11 days). In a multivariate linear regression model (adjusted R2 = 0.22; p < 0.001), preoperative tumor volume (p < 0.001), coronary artery disease (p = 0.002), hypertension (p = 0.029), and any major complication (p < 0.001) were associated with increased LOS (by 0.12, 3.79, 0.87, and 3.20 days respectively). A machine learning analysis using a random forest identified several potential nonlinear relationships between LOS and preoperative tumor dimensions (length, volume) and operative time that were not captured on regression. The random forest model had lower prediction error compared to the regression model (RMSE 5.67 vs. 44.59).

CONCLUSIONS

Tumor volume, coronary artery disease, hypertension, and major complications impact LOS. Machine learning methods may identify nonlinear relationships worthy of targeted clinical investigation and allow for more accurate patient counseling.

Sudden and Asymmetric Hearing Loss Among Active Duty Service Members: Underscoring the Importance of Active Screening

Military personnel are at increased risk of asymmetric hearing loss secondary to noise exposure. This report illustrates the importance of expeditiously evaluating for retrocochlear pathology even in young active duty service members with asymmetric or sudden hearing loss. A 36-year-old male presented with right-sided sudden hearing loss and dizziness. Audiometry revealed profound mid-to-high-frequency sensorineural hearing loss in the right ear. A 10-day course of oral steroid therapy and two intratympanic steroid injections were unsuccessful in restoring hearing. MRI revealed a 4.2 cm contrast-enhancing cerebellopontine angle tumor, consistent with a vestibular schwannoma (VS). Microsurgical resection utilizing a retrosigmoid craniotomy approach was performed with near-total resection of the tumor and preservation of the facial nerve but not the cochlear nerve. Despite preservation of the facial nerve, progression of post-operative facial weakness required gold weight placement to prevent exposure keratopathy. The patient had recovered partial function in all facial nerve branches at last follow-up. In light of the rising global incidence of VS, any asymmetric or sudden hearing loss in military service members should be evaluated with audiometry and referral to otolaryngology for workup of retrocochlear pathology.

Utility and value of pre-operative CT and MRI for cochlear implantation in the elderly

PURPOSE

To determine the utility and value of pre-operative imaging among the elderly population ≥70 y.o. with bilateral progressive sensorineural hearing loss undergoing cochlear implantation.

MATERIALS AND METHODS

A retrospective, cross-sectional review was performed at a tertiary referral center between 2010 and 2018 including patients ≥70 y.o. with bilateral presbycusis who underwent preoperative imaging and cochlear implantation. Primary outcome was whether pre-operative imaging changed the surgeon's surgical plan such as side of implant or abort procedure entirely. Patient characteristics including age, sex, side of implant, imaging modality, whether imaging changed surgical plan, and surgical complications were reviewed. One-way analysis of variance with post-hoc tests using the Bonferroni and Fisher's exact test were used to examine differences between groups. Secondary outcome was cost of preoperative imaging.

RESULTS

One hundred thirty-three patients (mean age 79.38 [5.51 SD]) who underwent a total of 142 surgical cases and 147 total scans. There were 92, 27, and 14 patients who underwent CT, MRI, or both, respectfully (n=133). Of the 142 implants that were placed, preoperative imaging did not reveal a contraindication to placing implant on one side over another. Total cost of imaging was $29,694. Estimated cost if 20% of cochlear implant eligible patients ≥70 y.o. underwent imaging is $7,763,490.

CONCLUSION

Decreasing unnecessary preoperative imaging can potentially decrease cost in cochlear implantation. In this sample, preoperative imaging did not affect the surgeon's choice of which side to operate on. However, imaging may provide an anatomic roadmap and contribute to either surgical confidence or caution. With the increasing amount of cochlear implant eligible elderly adults, preoperative imaging needs to be more clearly defined in this unique population.

Inner Ear Enhancement With Delayed 3D-FLAIR MRI Imaging in Vestibular Schwannoma

OBJECTIVES

To evaluate blood-labyrinth barrier permeability using delayed gadolinium enhanced three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) in patients with untreated sporadic vestibular schwannoma (VS) to interrogate the etiopathogenesis of progressive sensorineural hearing loss.

DESIGN

Prospective case series.

SETTING

Single institution tertiary care center.

PARTICIPANTS

Patients with previously untreated small to medium-sized unilateral VS undergoing 3D-FLAIR imaging 10 minutes (immediate) and 5 to 8 hours (delayed) after administration of intravenous gadolinium.

MAIN OUTCOME MEASURES

Comparison of cochlear and vestibular signal intensity ratios (SIRs) across immediate and delayed images and across the tumor and nontumor ear.

RESULTS

Six of eight (75%) patients demonstrated asymmetric enhancement of inner ear structures on delayed contrast-enhanced imaging. Delayed mean cochlea and vestibule SIRs were significantly greater than immediate SIRs (cochlea: 1.91 versus 1.21 [p = 0.02]; vestibule 1.74 versus 1.15 [p = 0.02]). A higher vestibule SIR was statistically significantly associated with poorer pure-tone average and word recognition scores (p = 0.001).

CONCLUSION

Ears with VS exhibited increased enhancement on delayed 3D FLAIR imaging. These findings suggest that alterations in blood-labyrinth barrier permeability may explain progressive sensorineural hearing loss in a subset of patients with untreated VS.

Working Toward Consensus on Sporadic Vestibular Schwannoma Care: A Modified Delphi Study

OBJECTIVE

To address variance in clinical care surrounding sporadic vestibular schwannoma, a modified Delphi study was performed to establish a general framework to approach vestibular schwannoma care. A multidisciplinary panel of experts was established with deliberate representation from key stakeholder societies. External validity of the final statements was assessed through an online survey of registered attendees of the 8th Quadrennial International Conference on Vestibular Schwannoma.

STUDY DESIGN

Modified Delphi method.

METHODS

The panel consisted of 16 vestibular schwannoma experts (8 neurotology and 8 neurosurgery) and included delegates representing the AAOHNSF, AANS/CNS tumor section, ISRS, and NASBS. The modified Delphi method encompassed a four-step process, comprised of one prevoting round to establish a list of focus areas and three subsequent voting rounds to successively refine individual statements and establish levels of consensus. Thresholds for achieving moderate consensus, at ≥67% agreement, and strong consensus, at ≥80% agreement, were determined a priori. All voting was performed anonymously via the Qualtrics online survey tool and full participation from all panel members was required before procession to the next voting round.

RESULTS

Through the Delphi process, 103 items were developed encompassing hearing preservation (N = 49), tumor control and imaging surveillance (N = 20), preferred treatment (N = 24), operative considerations (N = 4), and complications (N = 6). As a result of item refinement, moderate (4%) or strong (96%) consensus was achieved in all 103 final statements. Seventy-nine conference registrants participated in the online survey to assess external validity. Among these survey respondents, moderate (N = 21, 20%) or strong (N = 73, 71%) consensus was achieved in 94 of 103 (91%) statements, and no consensus was reached in 9 (9%). Of the four items with moderate consensus by the expert panel, one had moderate consensus by the conference participants and three had no consensus.

CONCLUSION

This modified Delphi study on sporadic vestibular schwannoma codifies 100% consensus within a multidisciplinary expert panel and is further supported by 91% consensus among an external group of clinicians who regularly provide care for patients with vestibular schwannoma. These final 103 statements address clinically pragmatic items that have direct application to everyday patient care. This document is not intended to define standard of care or drive insurance reimbursement, but rather to provide a general framework to approach vestibular schwannoma care for providers and patients.

Merlin-Deficient Schwann Cells Are More Susceptible to Radiation Injury than Normal Schwann Cells In Vitro

Objectives Vestibular schwannomas (VS) are intracranial tumors, which are caused by NF2 gene mutations that lead to loss of merlin protein. A treatment for VS is stereotactic radiosurgery, a form of radiation. To better understand the radiobiology of VS and radiation toxicity to adjacent structures, our main objectives were (1) investigate effects of single fraction (SF) radiation on viability, cytotoxicity, and apoptosis in normal Schwann cells (SCs) and merlin-deficient Schwann cells (MD-SCs) in vitro, and (2) analyze expression of double strand DNA breaks (γ-H2AX) and DNA repair protein Rad51 following irradiation.

Study Design This is a basic science study.

Setting This study is conducted in a research laboratory.

Participants Patients did not participate in this study.

Main Outcome Measures In irradiated normal SCs and MD-SCs (0–18 Gy), we measured (1) viability, cytotoxicity, and apoptosis using cell-based assays, and (2) percentage of cells with γ-H2AX and Rad51 on immunofluorescence.

Results A high percentage of irradiated MD-SCs expressed γ-H2AX, which may explain the dose-dependent losses in viability in rodent and human cell lines. In comparison, the viabilities of normal SCs were only compromised at higher doses of radiation (>12 Gy, human SCs), which may be related to less Rad51 repair. There were no further reductions in viability in human MD-SCs beyond 9 Gy, suggesting that <9 Gy may be insufficient to initiate maximal tumor control.

Conclusion The MD-SCs are more susceptible to radiation than normal SCs, in part through differential expression of γ-H2AX and Rad51. Understanding the radiobiology of MD-SCs and normal SCs is important for optimizing radiation protocols to maximize tumor control while limiting radiation toxicity in VS patients.