Extracellular vesicles derived from human vestibular schwannomas associated with poor hearing damage cochlear cells

"To implant or not to implant": electrically evoked auditory brainstem response audiometry for decision-making in vestibular schwannoma resection with CI

Vestibular schwannomas (VS) are often associated with debilitating hearing loss. Therefore, preservation and rehabilitation of hearing have become major therapeutic goals of VS management. Recently, cochlear implantation (CI) has been established as an effective treatment option for VS-associated hearing loss. Nevertheless, the integrity and proper function of the cochlear nerve must be evaluated before conducting CI to ensure optimal CI outcomes. Various methods to determine cochlear nerve integrity and functionality have emerged in the last few years. Of these, the use of electrically evoked auditory brainstem response audiometry (eABR) in particular has been proven to be a meaningful tool for monitoring cochlear nerve health during VS surgery. Here, the cochlear nerve can be electrically stimulated using an intracochlear test electrode before, during, and after tumor extirpation. Subsequently, the resulting brainstem responses can be measured and interpreted accordingly to obtain direct information on the cochlear nerve function. This allows for continuous monitoring of cochlear nerve function throughout the course of VS surgery and aids in the decision-making for CI candidacy. Finally, in the case of preserved brainstem responses, CI can be performed instantly after VS extirpation. This simultaneous approach offers several advantages over two-staged procedures and has been shown to be an efficient and safe procedure for restoring hearing after VS removal.

Single-cell transcriptomic atlas reveals increased regeneration in diseased human inner ear balance organs

Mammalian inner ear hair cell loss leads to permanent hearing and balance dysfunction. In contrast to the cochlea, vestibular hair cells of the murine utricle have some regenerative capacity. Whether human utricular hair cells regenerate in vivo remains unknown. Here we procured live, mature utricles from organ donors and vestibular schwannoma patients, and present a validated single-cell transcriptomic atlas at unprecedented resolution. We describe markers of 13 sensory and non-sensory cell types, with partial overlap and correlation between transcriptomes of human and mouse hair cells and supporting cells. We further uncover transcriptomes unique to hair cell precursors, which are unexpectedly 14-fold more abundant in vestibular schwannoma utricles, demonstrating the existence of ongoing regeneration in humans. Lastly, supporting cell-to-hair cell trajectory analysis revealed 5 distinct patterns of dynamic gene expression and associated pathways, including Wnt and IGF-1 signaling. Our dataset constitutes a foundational resource, accessible via a web-based interface, serving to advance knowledge of the normal and diseased human inner ear.

miR-431 secreted by human vestibular schwannomas increases the mammalian inner ear's vulnerability to noise trauma

Introduction

Vestibular schwannoma (VS) is an intracranial tumor that arises on the vestibular branch of cranial nerve VIII and typically presents with sensorineural hearing loss (SNHL). The mechanisms of this SNHL are postulated to involve alterations in the inner ear's microenvironment mediated by the genetic cargo of VS-secreted extracellular vesicles (EVs). We aimed to identify the EV cargo associated with poor hearing and determine whether its delivery caused hearing loss and cochlear damage in a mouse model in vivo.

Methods

VS tissue was collected from routinely resected tumors of patients with good (VS-GH) or poor (VS-PH) pre-surgical hearing measured via pure-tone average and word recognition scores. Next-generation sequencing was performed on RNA isolated from cultured primary human VS cells and EVs from VS-conditioned media, stratified by patients' hearing ability. microRNA expression levels were compared between VS-PH and VS-GH samples to identify differentially expressed candidates for packaging into a synthetic adeno-associated viral vector (Anc80L65). Viral vectors containing candidate microRNA were infused to the semicircular canals of mice to evaluate the effects on hearing, including after noise exposure.

Results

Differentially expressed microRNAs included hsa-miR-431-5p (enriched in VS-PH) and hsa-miR-192-5p (enriched in VS-GH). Newborn mice receiving intracochlear injection of viral vectors over-expressing hsa-miR-431-GFP, hsa-miR-192-GFP, or GFP only (control) had similar hearing 6 weeks post-injection. However, after acoustic trauma, the miR-431 group displayed significantly worse hearing, and greater loss of synaptic ribbons per inner hair cell in the acoustically traumatized cochlear region than the control group.

Conclusion

Our results suggest that miR-431 contributes to VS-associated hearing loss following cochlear stress. Further investigation is needed to determine whether miR-431 is a potential therapeutic target for SNHL.

Stem cells as potential therapeutics for hearing loss

Hearing impairment is a global health problem. Stem cell therapy has become a cutting-edge approach to tissue regeneration. In this review, the recent advances in stem cell therapy for hearing loss have been discussed. Nanomaterials can modulate the stem cell microenvironment to augment the therapeutic effects further. The potential of combining nanomaterials with stem cells for repairing and regenerating damaged inner ear hair cells (HCs) and spiral ganglion neurons (SGNs) has also been discussed. Stem cell-derived exosomes can contribute to the repair and regeneration of damaged tissue, and the research progress on exosome-based hearing loss treatment has been summarized as well. Despite stem cell therapy's technical and practical limitations, the findings reported so far are promising and warrant further investigation for eventual clinical translation.

The genetic landscape and possible therapeutics of neurofibromatosis type 2

Neurofibromatosis type 2 (NF2) is a genetic condition marked by the development of multiple benign tumors in the nervous system. The most common tumors associated with NF2 are bilateral vestibular schwannoma, meningioma, and ependymoma. The clinical manifestations of NF2 depend on the site of involvement. Vestibular schwannoma can present with hearing loss, dizziness, and tinnitus, while spinal tumor leads to debilitating pain, muscle weakness, or paresthesias. Clinical diagnosis of NF2 is based on the Manchester criteria, which have been updated in the last decade. NF2 is caused by loss-of-function mutations in the NF2 gene on chromosome 22, leading the merlin protein to malfunction. Over half of NF2 patients have de novo mutations, and half of this group are mosaic. NF2 can be managed by surgery, stereotactic radiosurgery, monoclonal antibody bevacizumab, and close observation. However, the nature of multiple tumors and the necessity of multiple surgeries over the lifetime, inoperable tumors like meningiomatosis with infiltration of the sinus or in the area of the lower cranial nerves, the complications caused by the operation, the malignancies induced by radiotherapy, and inefficiency of cytotoxic chemotherapy due to the benign nature of NF-related tumors have led a march toward exploring targeted therapies. Recent advances in genetics and molecular biology have allowed identifying and targeting of underlying pathways in the pathogenesis of NF2. In this review, we explain the clinicopathological characteristics of NF2, its genetic and molecular background, and the current knowledge and challenges of implementing genetics to develop efficient therapies.

Correlation between genotype and phenotype with special attention to hearing in 14 Japanese cases of NF2-related schwannomatosis

NF2-related schwannomatosis (NF2) is an autosomal dominant genetic disorder caused by variants in the NF2 gene. Approximately 50% of NF2 patients inherit pathogenic variants, and the remainder acquire de novo variants. NF2 is characterized by development of bilateral vestibular schwannomas. The genetic background of Japanese NF2 cases has not been fully investigated, and the present report performed a genetic analysis of 14 Japanese NF2 cases and examined genotype-phenotype correlations. DNA samples collected from peripheral blood were analyzed by next-generation sequencing, multiplex ligation-dependent probe amplification analysis, and in vitro electrophoresis. Ten cases had pathogenic or likely pathogenic variants in the NF2 gene, with seven truncating variants and three non-truncating variants. The age of onset in all seven cases with truncating variants was < 20 years. The age of onset significantly differed among cases with truncating NF2 variants, non-truncating NF2 variants, and no NF2 variants. However, the clinical course of tumor growth and hearing deterioration were not predicted only by germline pathogenic NF2 variants. The rate of truncating variants was higher in the present study than that of previous reports. Genotype-phenotype correlations in the age of onset were present in the analyzed Japanese NF2 cases.

Efficacy of Cochlear Implantation in Neurofibromatosis Type 2 Related Hearing Loss

OBJECTIVE

To investigate the results of cochlear implantation in subjects with neurofibromatosis type 2 (NF2) and bilateral vestibular schwannomas (VS).

STUDY DESIGN

Retrospective case series.

SETTING

University-based tertiary referral center.

SUBJECTS

Five subjects with NF2 and severe-to-profound sensorineural hearing loss.

INTERVENTION

Cochlear implantation.

MAIN OUTCOME MEASURE

Surgical outcomes and audiometric performance after cochlear implantation.

RESULTS

Five subjects (3 female, 2 male) were included in the study. The mean age at the time of implantation was 54 years old (range 35-78 years). Follow-up after cochlear implantation averaged 38 months (range 21-106 months). In the 5 implanted ears, 2 had no prior treatment, 1 had undergone prior radiation therapy, 1 underwent prior microsurgical removal, and 1 underwent prior microsurgical removal with adjuvant radiation therapy. The mean ipsilateral VS dimensions at time of implantation were 14 mm × 7.2 mm × 6.1 mm (mediolateral × anteroposterior × craniocaudal). Following cochlear implant activation, all 5 subjects achieved sound awareness, open set speech recognition, and 4 continue to be daily users of the devices.

CONCLUSION

Cochlear implantation is a viable hearing rehabilitation option for subjects with NF2 and severe-to-profound sensorineural hearing loss. All subjects reported benefit with their cochlear implant, including open set speech recognition, enhanced lip-reading skills and environmental awareness of sound. Four subjects continued to demonstrate improved open-set speech recognition at the time of their last evaluations.

Clinical Characteristics and Corticosteroid Responses of Acoustic Neuroma Treated as Idiopathic Sudden Sensorineural Hearing Loss

BACKGROUND

Few investigations have been conducted on the clinical characteristics of the differential diagnosis of acoustic neuroma with acute sensorineural hearing loss and idiopathic sudden sensorineural hearing loss. The aim of the study was to investigate the clinical characteristics of the differential diagnoses between acoustic neuroma and idiopathic sudden sensorineural hearing loss.

METHODS

The medical records of patients with acute sensorineural hearing loss (142 ears), including acoustic neuroma (19 ears) and idiopathic sudden sensorineural hearing loss (123 ears), who underwent audiometric and hematologic examinations and received systemic corticosteroid treatment, were retrospectively reviewed.

RESULTS

Hematological examination revealed that the erythrocyte sedimentation rate and fibrinogen values were significantly higher in the idiopathic sudden sensorineural hearing loss group compared to the acoustic neuroma group. Although all patients received corticosteroid treatment, hearing thresholds at the initial examination and 3 months after corticosteroid treatment were significantly higher in the idiopathic sudden sensorineural hearing loss group compared to the acoustic neuroma group at all frequencies. However, hearing recovery was worse in the acoustic neuroma group compared to the idiopathic sudden sensorineural hearing loss group. Furthermore, speech discrimination and short increment sensitivity index tests were not significantly different between the acoustic neuroma and idiopathic sudden sensorineural hearing loss groups.

CONCLUSION

This is the first study to reveal that speech discrimination and short increment sensitivity index tests are not useful for the differential diagnoses between acoustic neuroma and idiopathic sudden sensorineural hearing loss, whereas erythrocyte sedimentation rate and fibrinogen, blood biomarkers of inflammation and blood viscosity, would be considered valuable. Furthermore, acoustic neuroma should be considered in cases where acute sensorineural hearing loss did not recover after corticosteroid treatment, although the initial hearing loss was mild.

Human vestibular schwannoma reduces density of auditory nerve fibers in the osseous spiral lamina

Hearing loss in patients with vestibular schwannoma (VS) is commonly attributed to mechanical compression of the auditory nerve, though recent studies suggest that this retrocochlear pathology may be augmented by cochlear damage. Although VS-associated loss of inner hair cells, outer hair cells, and spiral ganglion cells has been reported, it is unclear to what extent auditory-nerve peripheral axons are damaged in VS patients. Understanding the degree of damage VSs cause to auditory nerve fibers (ANFs) is important for accurately modeling clinical outcomes of cochlear implantation, which is a therapeutic option to rehabilitate hearing in VS-affected ears. A retrospective analysis of human temporal-bone histopathology was performed on archival specimens from the Massachusetts Eye and Ear collection. Seven patients met our inclusion criteria based on the presence of sporadic, unilateral, untreated VS. Tangential sections of five cochlear regions were stained with hematoxylin and eosin, and adjacent sections were stained to visualize myelinated ANFs and efferent fibers. Following confocal microscopy, peripheral axons of ANFs within the osseous spiral lamina were quantified manually, where feasible, and with a "pixel counting" method, applicable to all sections. ANF density was substantially reduced on the VS side compared to the unaffected contralateral side. In the upper basal turn, a significant difference between the VS side and unaffected contralateral side was found using both counting methods, corresponding to the region tuned to 2000 Hz. Even spiral ganglion cells (SGCs) contralateral to VS were affected by the tumor as the majority of contralateral SGC counts were below average for age. This observation provides histological insight into the clinical observation that unilateral vestibular schwannomas pose a long-term risk of progression of hearing loss in the contralateral ear as well. Our pixel counting method for ANF quantification in the osseous spiral lamina is applicable to other pathologies involving sensorineural hearing loss. Future research is needed to classify ANFs into morphological categories, accurately predict their electrical properties, and use this knowledge to inform optimal cochlear implant programming strategies.

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.

The Role of Extracellular Vesicles in Cancer-Nerve Crosstalk of the Peripheral Nervous System

Although the pathogenic operations of cancer–nerve crosstalk (e.g., neuritogenesis, neoneurogensis, and perineural invasion—PNI) in the peripheral nervous system (PNS) during tumorigenesis, as well as the progression of all cancer types is continuing to emerge as an area of unique scientific interest and study, extensive, wide-ranging, and multidisciplinary investigations still remain fragmented and unsystematic. This is especially so in regard to the roles played by extracellular vesicles (EVs), which are lipid bilayer-enclosed nano- to microsized particles that carry multiple-function molecular cargos, facilitate intercellular communication in diverse processes. Accordingly, the biological significance of EVs has been greatly elevated in recent years, as there is strong evidence that they could contribute to important and possibly groundbreaking diagnostic and therapeutic innovations. This can be achieved and the pace of discoveries accelerated through cross-pollination from existing knowledge and studies regarding nervous system physiology and pathology, as well as thoroughgoing collaborations between oncologists, neurobiologists, pathologists, clinicians, and researchers. This article offers an overview of current and recent past investigations on the roles of EVs in cancer–nerve crosstalk, as well as in neural development, physiology, inflammation, injury, and regeneration in the PNS. By highlighting the mechanisms involved in physiological and noncancerous pathological cellular crosstalk, we provide hints that may inspire additional translational studies on cancer–nerve interplay.

Sporadic Vestibular Schwannoma Size and Location Do not Correlate With the Severity of Hearing Loss at Initial Presentation

Vestibular schwannoma (VS) is a non-malignant intracranial neoplasm arising from the vestibular branch of the 8th cranial nerve; sensorineural hearing loss (SNHL) is the most common associated symptom. Understanding whether VS imaging characteristics at the time of VS diagnosis can be associated with severity of VS-induced SNHL can impact patient counseling and define promising areas for future research. Patients diagnosed with VS at Massachusetts Eye and Ear (MEE) from 1994 through 2018 were analyzed if magnetic resonance imaging at VS presentation and sequential audiometry were available. Results were compared with original studies available in PubMed, written in English, on VS imaging characteristics and their impact on hearing in patients. A total of 477 patients with unilateral VS from the MEE database demonstrated no significant correlation between any features of tumor imaging at the time of VS diagnosis, such as VS size, impaction or location, and any hearing loss metric. Twenty-three published studies on the impact of VS imaging characteristics on patient hearing met inclusion criteria, with six solely involving NF2 patients and three including both sporadic and NF2-related VS patients. Fifteen studies reported a significant relationship between SNHL and at least one VS imaging characteristic; however, these trends were universally limited to NF2 patients or involved small patient populations, and were not reproduced in larger studies. Taken together, SNHL in sporadic VS patients is not readily associated solely with any tumor imaging characteristics. This finding motivates future studies to define how VS microenvironment and secreted molecules influence VS-induced SNHL.

Accelerated Long-Term Hearing Loss Progression After Recovery From Idiopathic Sudden Sensorineural Hearing Loss

Background and Introduction: Idiopathic sudden sensorineural hearing loss (ISSNHL) is characterized by rapid onset, typically unilateral presentation, and variable recovery. This case-control observational study aimed to improve patient counseling by objectively characterizing long-term hearing loss progression following ISSNHL, using sequential audiometry in the largest-to-date cohort of patients with ISSNHL.

Methods: Patients diagnosed with ISSNHL at a tertiary referral hospital from 1994 through 2018 with sequential audiometry were studied. Case controls with sensorineural hearing loss (SNHL) were matched by age, sex, baseline hearing status, and frequency of sequential audiometry. Hearing loss progression was quantified using Kaplan–Meier (K–M) analysis to account for variable follow-up duration. A subgroup analysis was performed by age, sex, preexisting comorbidities, ISSNHL-associated symptoms, ISSNHL treatment, and degree of post-ISSNHL hearing recovery.

Results: A total of 660 patients were identified with ISSNHL. In patients with post-ISSNHL recovery to good hearing [pure tone average (PTA) <30 dB and word recognition score (WRS) > 70%], median time to progression to non-serviceable (PTA > 50 dB or WRS <50%) SNHL was 16.4 years. In patients with incomplete post-ISSNHL hearing recovery, contralateral ears were also at significantly higher risk of SNHL progression over the following 12-year period. Male sex was associated with increased risk of SNHL progression [odds ratio (OR) 3.45 male vs. female] at 5-year follow up. No other subgroup factors influenced the likelihood of SNHL progression.

Discussion and Conclusion: Patients should be counseled on continued risk to long-term hearing after stabilization of hearing post-ISSNHL, with particular emphasis on greater risk to the contralateral ear in those with incomplete ipsilateral recovery.

Current Understanding of Hearing Loss in Sporadic Vestibular Schwannomas: A Systematic Review

Objective

Hearing loss is the most common initial symptom in patients with sporadic vestibular schwannomas (SVS). Hearing preservation is an important goal of both conservative and surgical therapy. However, the mechanism of SVS-associated hearing loss remains unclear. Thus, we performed this systematic review to summarize the current understanding of hearing loss in the SVS and distill a testable hypothesis to further illuminate its underlying mechanism.

Methods

A systematic review querying four databases (PubMed, Medline, Embase, and Web of Science) was performed to identify studies evaluating hearing loss in patients with SVS and exploring the potential mechanisms of hearing impairment.

Results

A total of 50 articles were eligible and included in this review. After analysis, the retrieved studies could be categorized into four types: (1) 29 studies explore the relationship between hearing loss and the growth pattern of the tumor (e.g., tumor size/volume, growth rate, tumor location, etc.); (2) ten studies investigate the potential role of cochlear dysfunction in hearing deterioration, including structural abnormality, protein elevation in perilymph, and cochlear malfunctioning; (3) two studies looked into SVS-induced impairment of auditory pathway and cortex; (4) in the rest nine studies, researchers explored the molecular mechanism underlying hearing loss in SVS, which involves molecular and genetic alterations, inflammatory response, growth factors, and other tumor-associated secretions.

Conclusions

Multiple factors may contribute to the hearing impairment in SVS, including the growth pattern of tumor, cochlear dysfunction, impairment of auditory pathway and cortex, genetic and molecular changes. However, our current understanding is still limited, and future studies are needed to explore this multifactorial hypothesis and dig deeper into its underlying mechanism.

Optimized preoperative determination of nerve of origin in patients with vestibular schwannoma

In vestibular schwannoma (VS) patients hearing outcome and surgery related risks can vary and depend on the nerve of origin. Preoperative origin differentiation between inferior or superior vestibular nerve may influence the decision on treatment, and the selection of optimal treatment and counselling modalities. A novel scoring system based on functional tests was designed to predict the nerve of origin for VS and was applied to a large number of consecutive patients. A prospective, double blind, cohort study including 93 patients with suspected unilateral VS was conducted at a tertiary referral centre. Preoperatively before tumor resection a functional test battery [video head-impulse test (vHIT) of all semicircular canals (SCC)], air-conducted cervical/ocular vestibular evoked myogenic potential tests (cVEMP, oVEMP), pure-tone audiometry, and speech discrimination was applied. Sensitivity and specificity of prediction of intraoperative finding by a preoperative score based on vHIT gain, cVEMP and oVEMP amplitudes and asymmetry ratios was calculated. For the prediction of inferior vestibular nerve origin, sensitivity was 73% and specificity was 80%. For the prediction of superior vestibular nerve origin, sensitivity was 60% and specificity was 90%. Based on the trade-off between sensitivity and specificity, optimized cut-off values of - 0.32 for cVEMP and - 0.11 for oVEMP asymmetry ratios and vHIT gain thresholds of 0.77 (anterior SCC), 0.84 (lateral SCC) and 0.80 (posterior SCC) were identified by receiver operator characteristic curves. The scoring system based on preoperative functional tests improves prediction of nerve of origin and can be applied in clinical routine.

Extracellular vesicles from human multipotent stromal cells protect against hearing loss after noise trauma in vivo

The lack of approved anti-inflammatory and neuroprotective therapies in otology has been acknowledged in the last decades and recent approaches are heralding a new era in the field. Extracellular vesicles (EVs) derived from human multipotent (mesenchymal) stromal cells (MSC) can be enriched in vesicular secretome fractions, which have been shown to exert effects (eg, neuroprotection and immunomodulation) of their parental cells. Hence, MSC-derived EVs may serve as novel drug candidates for several inner ear diseases. Here, we provide first evidence of a strong neuroprotective potential of human stromal cell-derived EVs on inner ear physiology. In vitro, MSC-EV preparations exerted immunomodulatory activity on T cells and microglial cells. Moreover, local application of MSC-EVs to the inner ear significantly attenuated hearing loss and protected auditory hair cells from noise-induced trauma in vivo. Thus, EVs derived from the vesicular secretome of human MSC may represent a next-generation biological drug that can exert protective therapeutic effects in a complex and nonregenerating organ like the inner ear.

New developments in neurofibromatosis type 2 and vestibular schwannoma

Neurofibromatosis type 2 (NF2) is a rare autosomal dominant disorder characterized by the development of multiple nervous system tumors due to mutation in the NF2 tumor suppressor gene. The hallmark feature of the NF2 syndrome is the development of bilateral vestibular schwannomas (VS). Although there is nearly 100% penetrance by 60 years of age, some patients suffer from a severe form of the disease and develop multiple tumors at an early age, while others are asymptomatic until later in life. Management options for VS include surgery, stereotactic radiation, and observation with serial imaging; however, currently, there are no FDA-approved pharmacotherapies for NF2 or VS. Recent advancements in the molecular biology underlying NF2 have led to a better understanding of the etiology and pathogenesis of VS. These novel signaling pathways may be used to identify targeted therapies for these tumors. This review discusses the clinical features and treatment options for sporadic- and NF2-associated VS, the diagnostic and screening criteria, completed and ongoing clinical trials, quality of life metrics, and opportunities for future research.

Cervical and Ocular Vestibular-Evoked Myogenic Potentials in Patients With Intracochlear Schwannomas

Objective: To evaluate ocular and cervical vestibular evoked myogenic potentials (oVEMPs and cVEMPs) in patients with solely intracochlear localization of an intralabyrinthine schwannoma (ILS).

Study Design: Retrospective analysis of a series of cases.

Setting: Monocentric study at a tertiary referral center.

Patients: Patients with intracochlear schwannoma (ICS) and VEMP measurements.

Outcome Measures: Signed asymmetry ratio (AR) of cVEMPs and oVEMPs to air conducted sound with AR cut-offs considered to be asymmetrical when exceeding ±30% for cVEMPs and ±40% for oVEMPs with respect to the side affected by the tumor (reduced amplitudes on the affected side indicated by negative values, enhanced amplitudes by positive values); VEMP amplitudes and latencies; tumor localization in the cochlear turn and scala.

Results: Nineteen patients with a solely intracochlear tumor (ICS patients) [10 males, 9 females, mean age 57.1 (SD: 13.4) years] were included in the study. On the affected side, cVEMPs were absent or reduced in 47% of the patients, normal in 32%, and enhanced in 21%. Ocular VEMPs on the affected side were absent or reduced in 53% of the patients, normal in 32% and enhanced in 15%. Latencies for cVEMPs and oVEMPs were not significantly different between the affected and non-affected side. In all patients with enhanced VEMPs, the tumor was located in the scala tympani and scala vestibuli.

Conclusions: As a new and unexpected finding, VEMP amplitudes can be enhanced in patients with intracochlear schwannoma, mimicking the third window syndrome.

Progression of Contralateral Hearing Loss in Patients With Sporadic Vestibular Schwannoma

Background and Introduction: Vestibular schwannomas (VSs) are the most common tumors of the cerebellopontine angle, typically presenting unilaterally with ipsilateral sensorineural hearing loss (SNHL). The mechanism of tumor-induced hearing loss has recently been shown to be related to secreted tumor factors, in addition to mechanical compression of the adjacent auditory nerve, and these factors may percolate through CSF or blood to affect contralateral hearing as well.

Methods: This is a retrospective study of medical records for patients treated for VS at Mass Eye and Ear from January 1994 through October 2018. Included patients had unilateral VS and sequential audiometry allowing for longitudinal assessment of hearing over time. Mass Eye and Ear's audiology database was used to select age- and sex-matched case controls, also with sequential audiometry, from the non-VS population. Subgroup analysis was performed by age, sex, baseline hearing, and tumor size at initial diagnosis. Hearing loss progression was performed using Kaplan-Meier analysis to account for variable follow-up times.

Results: A total of 661 patients were identified with VS and sequential audiometry. The population was predominantly female vs. male (368 vs. 293, p = 0.0035), driven primarily by younger patients with Koos 4 tumors (76 female vs. 49 male, p = 0.016). Patients with normal baseline hearing bilaterally (N = 241) demonstrated no significant difference in hearing loss progression in VS-contralateral vs. control ears. Patients with abnormal baseline VS-ipsilateral hearing (N = 190), however, demonstrated significantly higher likelihood of reaching moderate SNHL in VS-contralateral ears. Subgroup analysis by age, sex, and baseline tumor size did not yield any subgroup-specific trends for hearing loss progression.

Discussion and Conclusion: This is the largest study to date tracking long-term bilateral hearing outcomes in patients with VS, and demonstrates that, in patients with abnormal hearing in the VS-ipsilateral ear, there exists a long-term risk of progression to moderate hearing loss in the contralateral ear as well. Combined with the absence of significant changes in word understanding in the affected ears, these findings may provide clues to the nature of tumor-secreted factors involved in VS-associated hearing loss. Female predominance within the VS patient population is confirmed, driven mostly by younger female patients with Koos 4 tumors.

Hearing Improvement after Sudden Sensorineural Hearing Loss as a Predictor of Vestibular Schwannoma

INTRODUCTION

Sudden sensorineural hearing loss (SSNHL) can be the presenting symptom of vestibular schwannoma (VS). Usually, steroidal treatment is given before magnetic resonance imaging (MRI) is performed.

OBJECTIVES

The aim of this study was to investigate whether there is a different pattern of steroidal treatment response after SSNHL in patients with and without a VS, in order to determine whether rapid hearing improvement can serve as a predictor of the presence of VS.

METHODS

Charts of patients with SSNHLs were reviewed. Analysis of the presenting symptoms of patients with an SSNHL with and without a coexisting VS and comparison of the response to steroids of the two groups of patients was performed.

RESULTS

A total of 420 patients were treated for SSNHLs during the study period. Treatment consisted of intraoral prednisone 1 mg/kg/day. The male-to-female ratio was 1.00:1.17, and the median age at diagnosis was 38 years (range 18-82); neither parameter correlated with the presence of VS. MRI scans demonstrated a VS in 20 patients (4.76%). Audiometric testing 7 days after steroidal treatment initiation revealed that the pure-tone average of 240 patients (60%) without VS improved, and that of the 16 (80%) patients with VS improved by the same audiometric criteria (p = 0.0007).

CONCLUSIONS

Improvement of hearing within 1 week after steroidal treatment initiation in patients with SSNHLs may suggest the presence of a VS.

Age-related schwannomatosis with potential exosome-mediated contribution to prostate hyperplasia: a case report and mini-review

A 72-year-old Caucasian man incurring a prostate hypertrophy presented with a right forearm nodule, the growth of which appeared to parallel the rise in his blood prostate-specific antigen (PSA) level. Echographic examination was consistent with a median-nerve schwannoma, and was confirmed upon magnetic resonance imaging (MRI). Excision of the nodule was readily performed without significant neural damage, and its schwannoma nature was confirmed upon immunohistochemistry analysis. Importantly, blood PSA dropped abruptly from ≈13 to ≈5 ng/ml within 2 months postschwannoma resection, a swift drastic reduction unachievable with oral dutasteride alone. However, 6 weeks later, a new nodule became apparent on the back of the left knee and was identified as a second schwannoma, thereby suggesting that its growth could have been stimulated by the resection of the first schwannoma, as previously described for vestibular schwannomas. The second schwannoma was in fact two: the bigger one was in the common fibular nerve and the smaller one in the tibial nerve. Both echography and MRI results were confirmed upon surgical resection of the bigger knee schwannoma. Although the third schwannoma has not yet been resected and formally characterized, we face a schwannomatosis case with an unexpected potential exosome-mediated stimulating effect on PSA secretion (PSA immunohistochemistry was negative on both schwannomas). On the other hand, preliminary genomic analysis showed a deficient balance for chromosome 22, the very chromosome carrying the three main genes involved in schwannomatosis. This age-related schwannomatosis case is thus discussed in light of the following: age-related DNA repair deficiency culminating in loss of chromosome/heterozygosity; CpG methylation/demethylation-based epigenetic aging; age-related functional decline of the immune system responsible for inefficient elimination of abnormal cells and subsequent tumorigenic cell turn-over; exosome-mediated pathologic intercellular communications; and prostate-invading brain neural progenitors as pathologic peripheral nervous system (PNS) cells.

Predicting cochlear dead regions in patients with hearing loss through a machine learning-based approach: A preliminary study

We propose a machine learning (ML)-based model for predicting cochlear dead regions (DRs) in patients with hearing loss of various etiologies. Five hundred and fifty-five ears from 380 patients (3,770 test samples) diagnosed with sensorineural hearing loss (SNHL) were analyzed. A threshold-equalizing noise (TEN) test was applied to detect the presence of DRs. Data were collected on sex, age, side of the affected ear, hearing loss etiology, word recognition scores (WRS), and pure-tone thresholds at each frequency. According to the cause of hearing loss as diagnosed by the physician, we categorized the patients into six groups: 1) SNHL with unknown etiology; 2) sudden sensorineural hearing loss (SSNHL); 3) vestibular schwannoma (VS); 4) Meniere's disease (MD); 5) noise-induced hearing loss (NIHL); or 6) presbycusis or age-related hearing loss (ARHL). To develop a predictive model, we performed recursive partitioning and regression for classification, logistic regression, and random forest. The overall prevalence of one or more DRs in test ears was 20.36% (113 ears). Among the 3,770 test samples, the overall frequency-specific prevalence of DR was 6.7%. WRS, pure-tone thresholds at each frequency, disease type (VS or MD), and frequency information were useful for predicting DRs. Sex and age were not associated with detecting DRs. Based on these results, we suggest possible predictive factors for determining the presence of DRs. To improve the predictive power of the model, a more flexible model or more clinical features, such as the duration of hearing loss or risk factors for developing DRs, may be needed.

Surgery of the lateral skull base: a 50-year endeavour

Disregarding the widely used division of skull base into anterior and lateral, since the skull base should be conceived as a single anatomic structure, it was to our convenience to group all those approaches that run from the antero-lateral, pure lateral and postero-lateral side of the skull base as “Surgery of the lateral skull base”. “50 years of endeavour” points to the great effort which has been made over the last decades, when more and more difficult surgeries were performed by reducing morbidity. The principle of lateral skull base surgery, “remove skull base bone to approach the base itself and the adjacent sites of the endo-esocranium”, was then combined with function preservation and with tailoring surgery to the pathology. The concept that histology dictates the extent of resection, balancing the intrinsic morbidity of each approach was the object of the first section of the present report. The main surgical approaches were described in the second section and were conceived not as a step-by-step description of technique, but as the highlighthening of the surgical principles. The third section was centered on open issues related to the tumor and its treatment. The topic of vestibular schwannoma was investigated with the current debate on observation, hearing preservation surgery, hearing rehabilitation, radiotherapy and the recent efforts to detect biological markers able to predict tumor growth. Jugular foramen paragangliomas were treated in the frame of radical or partial surgery, radiotherapy, partial “tailored” surgery and observation. Surgery on meningioma was debated from the point of view of the neurosurgeon and of the otologist. Endolymphatic sac tumors and malignant tumors of the external auditory canal were also treated, as well as chordomas, chondrosarcomas and petrous bone cholesteatomas. Finally, the fourth section focused on free-choice topics which were assigned to aknowledged experts. The aim of this work was attempting to report the state of the art of the lateral skull base surgery after 50 years of hard work and, above all, to raise questions on those issues which still need an answer, as to allow progress in knowledge through sharing of various experiences. At the end of the reading, if more doubts remain rather than certainties, the aim of this work will probably be achieved.

A cerebellopontine angle mouse model for the investigation of tumor biology, hearing, and neurological function in NF2-related vestibular schwannoma

Neurofibromatosis type II (NF2) is a disease that lacks effective therapies. NF2 is characterized by bilateral vestibular schwannomas (VSs) that cause progressive and debilitating hearing loss, leading to social isolation and increased rates of depression. A major limitation in NF2 basic and translational research is the lack of animal models that allow the full spectrum of research into the biology and molecular mechanisms of NF2 tumor progression, as well as the effects on neurological function. In this protocol, we describe how to inject schwannoma cells into the mouse brain cerebellopontine angle (CPA) region. We also describe how to apply state-of-the-art intravital imaging and hearing assessment techniques to study tumor growth and hearing loss. In addition, ataxia, angiogenesis, and tumor-stroma interaction assays can be applied, and the model can be used to test the efficacy of novel therapeutic approaches. By studying the disease from every angle, this model offers the potential to unravel the basic biological underpinnings of NF2 and to develop novel therapeutics to control this devastating disease. Our protocol can be adapted to study other diseases within the CPA, including meningiomas, lipomas, vascular malformations, hemangiomas, epidermoid cysts, cerebellar astrocytomas, and metastatic lesions. The entire surgical procedure takes ~45 min per mouse and allows for subsequent longitudinal imaging, as well as neurological and hearing assessment, for up to 2 months.

Inner ear exosomes and their potential use as biomarkers

Exosomes are nanovesicles involved in intercellular communications. They are released by a variety of cell types; however, their presence in the inner ear has not been described in the literature. The aims of this study were to determine if exosomes are present in the inner ear and, if present, characterize the changes in their protein content in response to ototoxic stress. In this laboratory investigation, inner ear explants of 5-day-old Wistar rats were cultured and treated with either cisplatin or gentamicin. Hair cell damage was assessed by confocal microscopy. Exosomes were isolated using ExoQuick, serial centrifugation, and mini-column methods. Confirmation and characterization of exosomes was carried out using transmission electron microscopy (TEM), ZetaView, BCA protein analysis, and proteomics. Vesicles with a typical size distribution for exosomes were observed using TEM and ZetaView. Proteomic analysis detected typical exosome markers and markers for the organ of Corti. There was a statistically significant reduction in the exosome protein level and number of particles per cubic centimeter when the samples were exposed to ototoxic stress. Proteomic analysis also detected clear differences in protein expression when ototoxic medications were introduced. Significant changes in the proteomes of the exosomes were previously described in the context of hearing loss and ototoxic treatment. This is the first report describing exosomes derived from the inner ear. These findings may present an opportunity to conduct further studies with the hope of using exosomes as a biomarker to monitor inner ear function in the future.

Cochlear Dysfunction is not Common in Human Meningioma of the Internal Auditory Canal

HYPOTHESIS

Cochlear dysfunction is not common in human meningioma of the internal auditory canal.

BACKGROUND

Meningiomas arising from the cerebellopontine angle and internal auditory canal typically cause hearing loss. Cochlear dysfunction is known to contribute to sensorineural hearing loss induced by vestibular schwannoma, the most common tumor of the internal auditory canal. Detailed cochlear histopathology in meningioma has not been reported.

METHODS

Retrospective analysis of cochlear histopathology in five unoperated and five operated meningiomas of the internal auditory canal identified after screening human temporal bone collections from three academic medical centers.

RESULTS

While some dysfunction of all analyzed cochlear cell types was identified, a predominant or exclusive loss of hair cells was not observed in any meningioma. Only 14.3% of temporal bones showed significantly more hair cell damage on the side of the tumor when compared with the contralateral ear; cochlear neuronal damage was more prevalent in meningiomas. The incidence of hydrops, perilymphatic precipitate, or endolymphatic precipitate was low.

CONCLUSIONS

Substantial cochlear damage in human meningioma of the internal auditory canal is not common. This may explain the anecdotal hearing improvement observed after surgical resection of meningioma. Our findings underline the importance of developing therapeutic strategies to prevent cochlear neuronal degeneration due to tumors of the internal auditory canal.

Tumor-Penetrating Delivery of siRNA against TNFα to Human Vestibular Schwannomas

Vestibular schwannoma (VS) is the most common tumor of the cerebellopontine angle, and it typically presents with sensorineural hearing loss. The genomic landscape of schwannoma is complex and many of the molecules implicated in VS pathogenesis represent targets not amenable to antibody-based or small molecule therapeutics. Tumor-targeted delivery of small interfering RNA (siRNA) therapeutics provides a direct and effective means to interrogate targets while minimizing off-target effects. To establish a preclinical model for therapeutic inhibition of putative targets in VS, archived tumor specimens, fresh tumor cells derived from patients with sporadic VS, and an established schwannoma cell line were screened. Nanoparticles directed by the tumor-homing peptide iRGD were selectively taken up by primary VS cultures in vitro via interactions with αvβ3/β5 integrins and neuropilin-1 (NRP-1). Cellular uptake was inhibited by a neutralizing antibody against αv integrin in a dose-dependent manner. When applied to primary VS cultures, iRGD-targeted nanoparticles delivered siRNA directed against TNFα in a receptor-specific fashion to potently silence gene expression and protein secretion. Taken together, our results provide a proof of principle for tumor-targeted, nanoparticle-mediated delivery of siRNA to VS and establish a novel platform for the development and pre-clinical screening of molecular therapeutics against VS.

A Unified Methodological Framework for Vestibular Schwannoma Research

Vestibular schwannomas are the most common neoplasms of the cerebellopontine angle, making up 6-8% percent of all intracranial growths. Though these tumors cause sensorineural hearing loss in up to 95% of affected individuals, the molecular mechanisms underlying this hearing loss remain elusive. This article outlines the steps established in our laboratory to facilitate the collection and processing of various primary human tissue samples for downstream research applications integral to the study of vestibular schwannomas. Specifically, this work describes a unified methodological framework for the collection, processing, and culture of Schwann and schwannoma cells from surgical samples. This is integrated with parallel processing steps now considered essential for current research: the collection of tumor and nerve secretions, the preservation of RNA and the extraction of protein from collected tissues, the fixation of tissue for the preparation of sections, and the exposure of primary human cells to adeno-associated viruses for application to gene therapy. Additionally, this work highlights the translabyrinthine surgical approach to collect this tumor as a unique opportunity to obtain human sensory epithelium from the inner ear and perilymph. Tips to improve experimental quality are provided and common pitfalls highlighted.

Neonatal Murine Cochlear Explant Technique as an In Vitro Screening Tool in Hearing Research

While there have been remarkable advances in hearing research over the past few decades, there is still no cure for Sensorineural Hearing Loss (SNHL), a condition that typically involves damage to or loss of the delicate mechanosensory structures of the inner ear. Sophisticated in vitro and ex vivo assays have emerged in recent years, enabling the screening of an increasing number of potentially therapeutic compounds while minimizing resources and accelerating efforts to develop cures for SNHL. Though homogenous cultures of certain cell types continue to play an important role in current research, many scientists now rely on more complex organotypic cultures of murine inner ears, also known as cochlear explants. The preservation of organized cellular structures within the inner ear facilitates the in situ evaluation of various components of the cochlear infrastructure, including inner and outer hair cells, spiral ganglion neurons, neurites, and supporting cells. Here we present the preparation, culture, treatment, and immunostaining of neonatal murine cochlear explants. The careful preparation of these explants facilitates the identification of mechanisms that contribute to SNHL and constitutes a valuable tool for the hearing research community.