NLRP3 inflammasome activation in human vestibular schwannoma: Implications for tumor-induced hearing loss

Targeting the NLRP3 inflammasome in cochlear macrophages protects against hearing loss in chronic suppurative otitis media

The activation of the NLRP3 inflammasome has been linked to several inflammatory and autoinflammatory diseases. Despite cases of potential hearing improvement in immune-mediated diseases, direct evidence of the efficacy of targeting this mechanism in the inner ear is still lacking. Previously, we discovered that macrophages are associated with Sensorineural Hearing loss (SNHL) in Chronic Suppurative Otitis Media (CSOM), the leading cause of this permanent hearing loss in the developing world and incurring costs of $4 to $11 billion dollars in the United States. However, the underlying mechanism remained unknown. Here, we investigate how macrophages drive permanent hearing loss in CSOM. We first confirmed the occurrence of NLRP3 inflammasome activation in cochlear macrophages in CSOM. We then revealed that Outer Hair Cells (OHCs) were protected in CSOM by macrophage depletion and subsequently confirmed the same protection in the NLRP3 knockout condition. Furthermore, we showed that therapeutic inhibition of NLRP3 inflammasome activation and downstream inhibition of IL-1β protects OHCs in CSOM. Collectively, our data demonstrates that the main driver for hearing loss in CSOM is NLRP3 inflammasome activation in cochlear macrophages and this is therapeutically targetable, leading the way for the development of interventions to prevent the leading cause of permanent hearing loss and a costly disease in the developed world.

Long-Term Hearing Outcome For Vestibular Schwannomas After Microsurgery And Radiotherapy: A Systematic Review and Meta-Analysis

OBJECTIVE

Hearing loss is a common symptom associated with vestibular schwannoma (VS), either because of the tumor's effects on the cochlear nerve or due to active treatments such as surgery or stereotactic radiosurgery (SRS). Treatment decisions for VS are based on factors including tumor size, hearing status, patient symptoms, and institutional preference. The study aimed to investigate long-term auditory outcomes in VS patients undergoing active treatments with a hearing preservation intent.

DATA SOURCES

A systematic literature review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, searching Scopus, Pubmed, and Web of Science databases from inception to January 2024.

REVIEW METHODS

Studies meeting inclusion criteria, including a minimum 5-year follow-up and assessment of pre- and posttreatment hearing outcomes, were included. Pooled prevalence estimates for serviceable hearing after SRS and microsurgery were calculated using MetaXL software. Risk of bias assessment was performed with the Risk of Bias in Non-randomized Studies of Interventions tool.

RESULTS

Nine studies met the inclusion criteria, with 356 patients included for analysis. The pooled prevalence of maintaining serviceable hearing after SRS at 10 years was 18.1% (95% confidence interval [CI]: 1.7%-43.3%), with wide prediction intervals indicating variability in outcomes. Microsurgery demonstrated a higher prevalence of maintaining long-term serviceable hearing, with a pooled estimate of 74.5% (95% CI: 63.5%-84.1%).

CONCLUSION

This systematic review underscores the importance of long-term follow-up in evaluating auditory outcomes in VS treatment. Despite the biases inherent to pretreatment patients selection, hearing preservation microsurgery for sporadic VS removal demonstrated favorable and stable long-term serviceable hearing.

Exploring Inner Ear and Brain Connectivity through Perilymph Sampling for Early Detection of Neurological Diseases: A Provocative Proposal

Recent evidence shows that it is possible to identify the elements responsible for sensorineural hearing loss, such as pro-inflammatory cytokines and macrophages, by performing perilymph sampling. However, current studies have only focused on the diagnosis of such as otologic conditions. Hearing loss is a feature of certain neuroinflammatory disorders such as multiple sclerosis, and sensorineural hearing loss (SNHL) is widely detected in Alzheimer's disease. Although the environment of the inner ear is highly regulated, there are several communication pathways between the perilymph of the inner ear and cerebrospinal fluid (CSF). Thus, examination of the perilymph may help understand the mechanism behind the hearing loss observed in certain neuroinflammatory and neurodegenerative diseases. Herein, we review the constituents of CSF and perilymph, the anatomy of the inner ear and its connection with the brain. Then, we discuss the relevance of perilymph sampling in neurology. Currently, perilymph sampling is only performed during surgical procedures, but we hypothesize a simplified and low-invasive technique that could allow sampling in a clinical setting with the same ease as performing an intratympanic injection under direct visual check. The use of this modified technique could allow for perilymph sampling in people with hearing loss and neuroinflammatory/neurodegenerative disorders and clarify the relationship between these conditions; in fact, by measuring the concentration of neuroinflammatory and/or neurodegenerative biomarkers and those typically expressed in the inner ear in aging SNHL, it could be possible to understand if SNHL is caused by aging or neuroinflammation.

Single-cell RNA sequencing analysis of vestibular schwannoma reveals functionally distinct macrophage subsets

BACKGROUND

Vestibular schwannomas (VSs) remain a challenge due to their anatomical location and propensity to growth. Macrophages are present in VS but their roles in VS pathogenesis remains unknown.

OBJECTIVES

The objective was to assess phenotypic and functional profile of macrophages in VS with single-cell RNA sequencing (scRNAseq).

METHODS

scRNAseq was carried out in three VS samples to examine characteristics of macrophages in the tumour. RT-qPCR was carried out on 10 VS samples for CD14, CD68 and CD163 and a panel of macrophage-associated molecules.

RESULTS

scRNAseq revealed macrophages to be a major constituent of VS microenvironment with three distinct subclusters based on gene expression. The subclusters were also defined by expression of CD163, CD68 and IL-1β. AREG and PLAUR were expressed in the CD68+CD163+IL-1β+ subcluster, PLCG2 and NCKAP5 were expressed in CD68+CD163+IL-1β- subcluster and AUTS2 and SPP1 were expressed in the CD68+CD163-IL-1β+ subcluster. RT-qPCR showed expression of several macrophage markers in VS of which CD14, ALOX15, Interleukin-1β, INHBA and Colony Stimulating Factor-1R were found to have a high correlation with tumour volume.

CONCLUSIONS

Macrophages form an important component of VS stroma. scRNAseq reveals three distinct subsets of macrophages in the VS tissue which may have differing roles in the pathogenesis of VS.

Immune Profiling of Secreted Factors from Human Vestibular Schwannoma Cells and Tumor-associated Macrophages

OBJECTIVES

This study compared the immune-related secretory capacity of human vestibular schwannoma (VS) and tumor-assisted macrophages (TAMs) with their normal counterparts (Schwann cells [SC] and peripheral blood monocyte-derived macrophages [Mo-MFs], respectively), and examined relationships with presurgical hearing and tumor size.

METHODS

VS tumors (n = 16), auditory nerve (n = 1), blood (n = 9), and great auricular nerves (n = 3) were used. SCs (S100B+ ) and TAMs (CD68+ ) were isolated from VS tissue for culture. The secreted levels of 65 immune-related factors were measured and compared using unpaired t-tests with Welch correction (schwannoma vs. SCs) or Mann-Whitney tests (TAMs and Mo-MFs). Associations between factor concentration and word recognition (WR), pure-tone average (PTA), and tumor size were evaluated with Spearman correlation.

RESULTS

Secreted factors with significantly higher concentrations in schwannoma versus SC supernatants included IL-2 and BAFF, whereas MMP-1, IL-6, FGF-2, VEGF-A, MIP-3α, and GRO-α concentrations were significantly higher in TAMs versus Mo-MFs (all p < 0.05). Worse WR was significantly associated with higher secretion of fractalkine, eotaxin-3, CD30, and IL-16 by VS cells; IP-10, eotaxin-3, multiple interleukins, GM-CSF, SCF, and CD30 by TAMs; and TNF-α and MIP-1α by Mo-MFs (all p < 0.05). Worse PTA was significantly correlated with higher secretion of IL-16 by VS cells (p < 0.05). Larger tumor size was significantly correlated with higher secretion of eotaxin by VS cells, and of IL-7, IL-21, and LIF by TAMs (all p = 0.017).

CONCLUSIONS

Differential secretion of immune-related factors was observed in schwannoma versus normal SCs and in TAMs versus Mo-MFs, some of which were correlated with worse hearing and larger VS tumors.

LEVEL OF EVIDENCE

N/A Laryngoscope, 134:S1-S14, 2024.

Evidence for inflammation in normal-appearing brain regions in patients with growing sporadic vestibular schwannoma: A PET study

Background

Nonauditory symptoms can be a prominent feature in patients with sporadic vestibular schwannoma (VS), but the cause of these symptoms is unknown. Inflammation is hypothesized to play a key role in the growth and symptomatic presentation of sporadic VS, and in this study, we investigated through translocator protein (TSPO) positron emission tomography (PET) whether inflammation occurred within the "normal appearing" brain of such patients and its association with tumor growth.

Methods

Dynamic PET datasets from 15 patients with sporadic VS (8 static and 7 growing) who had been previously imaged using the TSPO tracer [11C](R)-PK11195 were included. Parametric images of [11C](R)-PK11195 binding potential (BPND) and the distribution volume ratio (DVR) were derived and compared across VS growth groups within both contralateral and ipsilateral gray (GM) and white matter (WM) regions. Voxel-wise cluster analysis was additionally performed to identify anatomical regions of increased [11C](R)-PK11195 binding.

Results

Compared with static tumors, growing VS demonstrated significantly higher cortical (GM, 1.070 vs. 1.031, P = .03) and whole brain (GM & WM, 1.045 vs. 1.006, P = .03) [11C](R)-PK11195 DVR values. The voxel-wise analysis supported the region-based analysis and revealed clusters of high TSPO binding within the precentral, postcentral, and prefrontal cortex in patients with growing VS.

Conclusions

We present the first in vivo evidence of increased TSPO expression and inflammation within the brains of patients with growing sporadic VS. These results provide a potential mechanistic insight into the development of nonauditory symptoms in these patients and highlight the need for further studies interrogating the role of neuroinflammation in driving VS symptomatology.

The CXCL12-CXCR4-NLRP3 axis promotes Schwann cell pyroptosis and sciatic nerve demyelination in rats

Studies have shown that the activation of the NOD-like receptor protein 3 (NLRP3) inflammasome is detrimental to the functional recovery of the sciatic nerve, but the regulatory mechanisms of the NLRP3 inflammasome in peripheral nerves are unclear. C-X-C motif chemokine 12 (CXCL12) can bind to C-X-C chemokine receptor type 4 (CXCR4) and participate in a wide range of nerve inflammation by regulating the NLRP3 inflammasome. Based on these, we explore whether CXCL12-CXCR4 axis regulates the NLRP3 inflammasome in the peripheral nerve. We found that CXCR4/CXCL12, NLRP3 inflammasome-related components, pyroptosis-related proteins and inflammatory factors in the sciatic nerve injured rats were markedly increased compared with the sham-operated group. AMD3100, a CXCR4 antagonist, reverses the activation of NLRP3 inflammasome, Schwann cell pyroptosis and sciatic nerve demyelination. We further treated rat Schwann cells with LPS (lipopolysaccharide) and adenosine triphosphate (ATP) to mimic the cellular inflammation model of sciatic nerve injury, and the results were consistent with those in vivo. In addition, both in vivo and in vitro experiments demonstrated that AMD3100 treatment reduced the phosphorylation of nuclear factor κB (NF-κB) and the expression of thioredoxin interacting protein (TXNIP), which contributes to activating NLRP3 inflammasome. Therefore, our findings suggest that, after sciatic nerve injury, CXCL12-CXCR4 axis may promote Schwann cell pyroptosis and sciatic nerve demyelination through activating NLRP3 inflammasome and slow the recovery process of the sciatic nerve.

Cytokine Profiling of Cyst Fluid and Tumor-Associated Macrophages in Cystic Vestibular Schwannoma

BACKGROUND

The vestibular schwannoma (VS) secretome can initiate monocyte recruitment and macrophage polarization to M1 (proinflammatory) and/or M2 (protumorigenic) phenotypes, which in turn secrete additional cytokines that contribute to the tumor microenvironment. Profiling cyst fluid and cerebrospinal fluid (CSF) in cystic VS provides a unique opportunity to understand mechanisms that may contribute to tumor progression and cyst formation.

HYPOTHESIS

Cystic VSs secrete high levels of cytokines into cyst fluid and express abundant M1 and M2 macrophages.

METHODS

Tumor, CSF, and cyst fluid were prospectively collected from 10 cystic VS patients. Eighty cytokines were measured in fluid samples using cytokine arrays and compared with normal CSF from normal donors. Immunofluorescence was performed for CD80 + M1 and CD163 + M2 macrophage markers. Demographic, audiometric, and radiographic information was obtained through retrospective chart review.

RESULTS

Cyst fluid expressed more osteopontin and monocyte chemotactic protein-1 (MCP-1; p < 0.0001), when compared with normal CSF. Cyst fluid also expressed more protein ( p = 0.0020), particularly MCP-1 ( p < 0.0001), than paired CSF from the same subjects. MCP-1 expression in cyst fluid correlated with CD80 + staining in VS tissue ( r = 0.8852; p = 0.0015) but not CD163 + staining.

CONCLUSION

Cyst fluid from cystic VS harbored high levels of osteopontin and MCP-1, which are cytokines important in monocyte recruitment and macrophage polarization. MCP-1 may have a significant role in molding the tumor microenvironment, by polarizing monocytes to CD80 + M1 macrophages in cystic VS. Further investigations into the role of cytokines and macrophages in VS may lead to new avenues for therapeutic intervention.

Identification of immune-related candidate biomarkers in plasma of patients with sporadic vestibular schwannoma

Vestibular schwannoma (VS) is an intracranial tumor arising from neoplastic Schwann cells and typically presenting with hearing loss. The traditional belief that hearing deficit is caused by physical expansion of the VS, compressing the auditory nerve, does not explain the common clinical finding that patients with small tumors can have profound hearing loss, suggesting that tumor-secreted factors could influence hearing ability in VS patients. We conducted profiling of patients' plasma for 66 immune-related factors in patients with sporadic VS (N > 170) and identified and validated candidate biomarkers associated with tumor size (S100B) and hearing (MCP-3). We further identified a nine-biomarker panel (TNR-R2, MIF, CD30, MCP-3, IL-2R, BLC, TWEAK, eotaxin, and S100B) with outstanding discriminatory ability for VS. These findings revealed possible therapeutic targets for VS, providing a unique diagnostic tool that may predict hearing change and tumor growth in VS patients, and may inform the timing of tumor resection to preserve hearing.

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.

Drug Repositioning for Refractory Benign Tumors of the Central Nervous System

Drug repositioning (DR) is the process of identifying novel therapeutic potentials for already-approved drugs and discovering new therapies for untreated diseases. DR can play an important role in optimizing the pre-clinical process of developing novel drugs by saving time and cost compared with the process of de novo drug discovery. Although the number of publications related to DR has rapidly increased, most therapeutic approaches were reported for malignant tumors. Surgical resection represents the definitive treatment for benign tumors of the central nervous system (BTCNS). However, treatment options remain limited for surgery-, chemotherapy- and radiation-refractory BTCNS, as well as malignant tumors. Meningioma, pituitary neuroendocrine tumor (PitNET), and schwannoma are the most common BTCNS. The treatment strategy using DR may be applied for refractory BTCNS, such as Grade 2 meningiomas, neurofibromatosis type 2-related schwannomatosis, and PitNETs with cavernous sinus invasion. In the setting of BTCNS, stable disease can provide significant benefit to the patient. DR may provide a longer duration of survival without disease progression for patients with refractory BTCNS. This article reviews the utility of DR for refractory BTCNS.

Metastasis Associated in Colorectal Cancer 1 (MACC1) mRNA Expression Is Enhanced in Sporadic Vestibular Schwannoma and Correlates to Deafness

Vestibular schwannoma (VS) are benign cranial nerve sheath tumors of the vestibulocochlear nerve. Their incidence is mostly sporadic, but they can also be associated with NF2-related schwannomatosis (NF2), a hereditary tumor syndrome. Metastasis associated in colon cancer 1 (MACC1) is known to contribute to angiogenesis, cell growth, invasiveness, cell motility and metastasis of solid malignant cancers. In addition, MACC1 may be associated with nonsyndromic hearing impairment. Therefore, we evaluated whether MACC1 may be involved in the pathogenesis of VS. Sporadic VS, recurrent sporadic VS, NF2-associated VS, recurrent NF2-associated VS and healthy vestibular nerves were analyzed for MACC1 mRNA and protein expression by quantitative polymerase chain reaction and immunohistochemistry. MACC1 expression levels were correlated with the patients' clinical course and symptoms. MACC1 mRNA expression was significantly higher in sporadic VS compared to NF2-associated VS (p < 0.001). The latter expressed similar MACC1 concentrations as healthy vestibular nerves. Recurrent tumors resembled the MACC1 expression of the primary tumors. MACC1 mRNA expression was significantly correlated with deafness in sporadic VS patients (p = 0.034). Therefore, MACC1 might be a new molecular marker involved in VS pathogenesis.

Hearing Aid in Vestibular-Schwannoma-Related Hearing Loss: A Review

(1) Background: Several types of hearing aids are available for the rehabilitation of vestibular-schwannoma (VS)-related hearing loss. There is a lack of recently published papers regarding this theme. The aim of the present work is to organize current knowledge. (2) Methods: A review of the literature regarding the topics "vestibular schwannoma", "hearing loss", and "hearing aid" was performed. Nineteen studies were thus considered. (3) Results: Conventional hearing aids, contralateral routing of signal (CROS) aids, bone anchored hearing aids (BAHA), and others are available options for hearing rehabilitation in VS patients. The speech discrimination score (SDS) is considered the best measure to assess candidacy for rehabilitation with hearing aids. The best hearing rehabilitative conditions in VS patients when using conventional hearing aid devices are a mild-moderate hearing loss degree with good word recognition (more than 50% SDS). CROS-Aid and BAHA are reported to be beneficial. CROS-Aid expands on the area of receiving hearing. BAHA aids use direct bone-conduction stimulation. Unfortunately, there are no available studies focused specifically on VS patients that compare CROS and BAHA technologies. (4) Conclusions: Hearing aids, CROS, and BAHA are viable options for rehabilitating hearing impairment in VS, but require an accurate case-by-case audiological evaluation for rehabilitating hearing impairment in VS. Further studies are needed to prove if what is currently known about similar hearing illnesses can be confirmed, particularly in the case of VS.

The comparable tumour microenvironment in sporadic and NF2-related schwannomatosis vestibular schwannoma

Bilateral vestibular schwannoma is the hallmark of NF2-related schwannomatosis, a rare tumour predisposition syndrome associated with a lifetime of surgical interventions, radiotherapy and off-label use of the anti-angiogenic drug bevacizumab. Unilateral vestibular schwannoma develops sporadically in non-NF2-related schwannomatosis patients for which there are no drug treatment options available. Tumour-infiltrating immune cells such as macrophages and T-cells correlate with increased vestibular schwannoma growth, which is suggested to be similar in sporadic and NF2-related schwannomatosis tumours. However, differences between NF2-related schwannomatosis and the more common sporadic disease include NF2-related schwannomatosis patients presenting an increased number of tumours, multiple tumour types and younger age at diagnosis. A comparison of the tumour microenvironment in sporadic and NF2-related schwannomatosis tumours is therefore required to underpin the development of immunotherapeutic targets, identify the possibility of extrapolating ex vivo data from sporadic vestibular schwannoma to NF2-related schwannomatosis and help inform clinical trial design with the feasibility of co-recruiting sporadic and NF2-related schwannomatosis patients. This study drew together bulk transcriptomic data from three published Affymetrix microarray datasets to compare the gene expression profiles of sporadic and NF2-related schwannomatosis vestibular schwannoma and subsequently deconvolved to predict the abundances of distinct tumour immune microenvironment populations. Data were validated using quantitative PCR and Hyperion imaging mass cytometry. Comparative bioinformatic analyses revealed close similarities in NF2-related schwannomatosis and sporadic vestibular schwannoma tumours across the three datasets. Significant inflammatory markers and signalling pathways were closely matched in NF2-related schwannomatosis and sporadic vestibular schwannoma, relating to the proliferation of macrophages, angiogenesis and inflammation. Bulk transcriptomic and imaging mass cytometry data identified macrophages as the most abundant immune population in vestibular schwannoma, comprising one-third of the cell mass in both NF2-related schwannomatosis and sporadic tumours. Importantly, there were no robust significant differences in signalling pathways, gene expression, cell type abundance or imaging mass cytometry staining between NF2-related schwannomatosis and sporadic vestibular schwannoma. These data indicate strong similarities in the tumour immune microenvironment of NF2-related schwannomatosis and sporadic vestibular schwannoma.

The Effect of Immediate Microsurgical Resection of Vestibular Schwannoma on Hearing Preservation

OBJECTIVE

Evaluate for differences in postoperative hearing in patients who undergo immediate versus delayed hearing preservation microsurgical resection of vestibular schwannomas (VS).

STUDY DESIGN

Retrospective single-institution cohort study spanning November 2017 to November 2021.

SETTING

Single-institution tertiary care hospital.

PATIENTS

Sporadic VS in patients with American Academy of Otolaryngology-Head and Neck Surgery hearing classification A or B, with tumor size less than or equal to 2 cm and undergoing hearing preservation microsurgical resection.

INTERVENTIONS

Delayed surgical intervention defined by time from first diagnostic MRI to date of surgery being greater than 3 months.

MAIN OUTCOME MEASURES

Preoperative and postoperative audiometric performance.

RESULTS

In total, 193 patients met inclusion criteria. Within the cohort, 70 (36%) proceeded with surgery within 3 months of diagnostic MRI with a mean observation time of 62 days, whereas 123 (63%) underwent surgery after 3 months with a mean observation time of 301 days. There was no difference in preoperative hearing between the two groups with word recognition score 99% in early intervention group and 100% in delayed intervention group ( p = 0.6). However, 64% of those who proceeded with immediate surgery had successful hearing preservation, compared to a 42% of those who had delayed intervention ( p < 0.01). In a multivariable logistic regression accounting for preoperative word recognition score, tumor size, and age at diagnosis, the odds of hearing preservation were lower in those who delayed surgery compared to immediate surgery (odds ratio, 0.31; 95% confidence interval, 0.15-0.61).

CONCLUSIONS

Patients who underwent microsurgical resection within 3 months of diagnosis demonstrated a hearing preservation advantage compared to those who did not. Findings of this study highlight the counseling challenges associated with the timing of surgical treatment of VS in patients presenting with good preoperative hearing and small tumors.

Updates on Tumor Biology in Vestibular Schwannoma

Vestibular schwannomas (VSs) are benign tumors that develop after biallelic inactivation of the neurofibromatosis type 2 (NF2) gene that encodes the tumor suppressor merlin. Merlin inactivation leads to cell proliferation by dysregulation of receptor tyrosine kinase signaling and other intracellular pathways. In VS without NF2 mutations, dysregulation of non-NF2 genes can promote pathways favoring cell proliferation and tumorigenesis. The tumor microenvironment of VS consists of multiple cell types that influence VS tumor biology through complex intercellular networking and communications.

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.

Hearing Rehabilitation in Vestibular Schwannoma

The most common complaint among patients with vestibular schwannoma (VS) is hearing loss. This significantly affects the quality of life before, during, and after treatment for patients with VS. Untreated hearing loss in VS patients may even lead to depression and feelings of social isolation. A variety of devices are available for hearing rehabilitation for patients with vestibular schwannoma. These include contralateral routing of hearing signals (CROSs), bone-anchored hearing devices, auditory brainstem implants (ABI), and cochlear implants. In the United States, ABI is approved for patients 12 years of age and older with neurofibromatosis type 2. In the past few years, cochlear implantation has been offered simultaneously or sequentially with tumor resection or irradiation, or even to patients whose VS have been monitored with serial imaging. However, determining the functional integrity of the auditory nerve in patients with vestibular schwannoma is a challenge. This review article consists of (1) the pathophysiology of vestibular schwannoma (VS), (2) hearing loss in VS, (3) treatment of VS and associated hearing loss, (4) options for auditory rehabilitation in patients with VS with their individual benefits and limitations, and (5) challenges in hearing rehabilitation in this cohort of patients to determine auditory nerve functionality. (6) Future directions.

Comparative Transcriptomic Analysis of Archival Human Vestibular Schwannoma Tissue from Patients with and without Tinnitus

Vestibular schwannoma (VS) is an intracranial tumor that commonly presents with tinnitus and hearing loss. To uncover the molecular mechanisms underlying VS-associated tinnitus, we applied next-generation sequencing (Illumina HiSeq) to formalin-fixed paraffin-embedded archival VS samples from nine patients with tinnitus (VS-Tin) and seven patients without tinnitus (VS-NoTin). Bioinformatic analysis was used to detect differentially expressed genes (DEG; i.e., ≥two-fold change [FC]) while correcting for multiple comparisons. Using RNA-seq analysis, VS-Tin had significantly lower expression of GFAP (logFC = −3.04), APLNR (logFC = −2.95), PREX2 (logFC = −1.44), and PLVAP (logFC = −1.04; all p < 0.01) vs. VS-NoTin. These trends were validated by using real-time RT-qPCR. At the protein level, immunohistochemistry revealed a trend for less PREX2 and apelin expression and greater expression of NLRP3 inflammasome and CD68-positive macrophages in VS-Tin than in VS-NoTin, suggesting the activation of inflammatory processes in VS-Tin. Functional enrichment analysis revealed that the top three protein categories—glycoproteins, signal peptides, and secreted proteins—were significantly enriched in VS-Tin in comparison with VS-NoTin. In a gene set enrichment analysis, the top pathway was allograft rejection, an inflammatory pathway that includes the MMP9, CXCL9, IL16, PF4, ITK, and ACVR2A genes. Future studies are needed to examine the importance of these candidates and of inflammation in VS-associated tinnitus.

Tumor Microenvironment in Sporadic Vestibular Schwannoma: A Systematic, Narrative Review

Although diagnosis and treatment of vestibular schwannomas (VSs) improved in recent years, no factors have yet been identified as being capable of predicting tumor growth. Molecular rearrangements occur in neoplasms before any macroscopic morphological changes become visible, and the former are the underlying cause of disease behavior. Tumor microenvironment (TME) encompasses cellular and non-cellular elements interacting together, resulting in a complex and dynamic key of tumorigenesis, drug response, and treatment outcome. The aim of this systematic, narrative review was to assess the level of knowledge on TME implicated in the biology, behavior, and prognosis of sporadic VSs. A search (updated to November 2022) was run in Scopus, PubMed, and Web of Science electronic databases according to the PRISMA guidelines, retrieving 624 titles. After full-text evaluation and application of inclusion/exclusion criteria, 37 articles were included. VS microenvironment is determined by the interplay of a dynamic ecosystem of stromal and immune cells which produce and remodel extracellular matrix, vascular networks, and promote tumor growth. However, evidence is still conflicting. Further studies will enhance our understanding of VS biology by investigating TME-related biomarkers able to predict tumor growth and recognize immunological and molecular factors that could be potential therapeutic targets for medical treatment.

The NLRP3 inflammasome as a target for sensorineural hearing loss

Sensorineural hearing loss is the most common type of hearing loss in adults and occurs due to damage of the inner ear caused by a range of factors including ageing, excessive noise, toxins, and cancer. Auto-inflammatory disease is also a cause of hearing loss and there is evidence that inflammation could contribute to hearing loss in other conditions. Within the inner ear there are resident macrophage cells that respond to insults and whose activation correlates with damage. The NLRP3 inflammasome is a multi-molecular pro-inflammatory protein complex that forms in activated macrophages and may contribute to hearing loss. The aim of this article is to discuss the evidence for the NLRP3 inflammasome and associated cytokines as potential therapeutic targets for sensorineural hearing loss in conditions ranging from auto-inflammatory disease to tumour-induced hearing loss in vestibular schwannoma.

Increased Circulating Chemokines and Macrophage Recruitment in Growing Vestibular Schwannomas

BACKGROUND

There is evidence that macrophage infiltration in the tumor microenvironment promotes vestibular schwannoma (VS) growth. Efficacy of bevacizumab in NF2-associated VS demonstrates the value of therapies targeting the microvascular tumor microenvironment, and tumor-associated macrophages (TAMs) may represent another druggable target.

OBJECTIVE

To characterize the relationship between growth, TAM infiltration, and circulating monocyte chemokines in a large cohort of patients with VS.

METHODS

Immunostaining for Iba1 (macrophages), CD31 (endothelium), and fibrinogen (permeability) was performed on 101 growing and 19 static sporadic VS. The concentrations of monocyte-specific chemokines were measured in the plasma of 50 patients with growing VS and 25 patients with static VS.

RESULTS

The Iba1 + cell count was significantly higher in growing as compared with static VS (592 vs 226/×20 HPF, P =<0.001). Similarly, the CD31 + % surface area was higher in growing VS (2.19% vs 1.32%, P = .01). There was a positive correlation between TAM infiltration and VS growth rate, which persisted after controlling for the effect of tumor volume (aR2 = 0.263, P =<0.001). The plasma concentrations of several monocytic chemokines were higher in patients with growing rather than static VS.

CONCLUSION

There is a strong positive correlation between TAM infiltration and volumetric growth of VS, and this relationship is independent of tumor size. There is a colinear relationship between TAM infiltration and tumor vascularity, implying that inflammation and angiogenesis are interlinked in VS. Chemokines known to induce monocyte chemotaxis are found in higher concentrations in patients with growing VS, suggestive of a potential pathophysiological mechanism.

Labyrinthine Fluid Signal Intensity on T2-Weighted MR Imaging in Patients With Vestibular Schwannomas Undergoing Proton Radiotherapy: A Longitudinal Assessment

OBJECTIVE

In vestibular schwannoma patients, a loss of signal intensity (SI) on T2-weighted magnetic resonance imaging (MRI) has been reported within the ipsilateral labyrinth. The purpose of this study was to quantitatively evaluate the occurrence and course of this intensity loss in relation to proton radiotherapy and its possible association with hearing loss.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral center.

PATIENTS

Patients who received proton therapy for a vestibular schwannoma and underwent at least two high-resolution T2-weighted cisternographic sequence (constructive interference in steady state/fast imaging employing steady-state acquisition/DRIVE) MRIs and audiometry assessments.

MAIN OUTCOME MEASURES

Relative T2 SIs from the vestibules and basal/apical cochlear turns of the labyrinth, bilaterally.

RESULTS

Ninety-five MRI scans from 34 patients were included. The apical turn of the ipsilateral cochlea showed a lower mean cochlear SI than on the contralateral side (±3.5 versus 5.0). The mean relative cochlear SI did not significantly change after proton radiotherapy. The ipsilateral vestibule showed a higher SI than the cochlea. The relative mean cochlear SI was not directly correlated to (the degree of) hearing loss before or after proton radiotherapy, nor did it predict future hearing loss.

CONCLUSION

The relative mean cochlear SI on cisternographic T2-MRI in vestibular schwannoma patients is diminished on the treated side, when compared with the ipsilateral vestibule and the contralateral cochlea/vestibule. The SI of the ipsilateral cochlea does not further decrease after proton radiotherapy and seems to be related to the tumor rather than the therapy. The diminished cochlear SI does not correlate with subsequent loss of hearing.

Identification of Immune-Related Candidate Biomarkers in Plasma of Patients with Sporadic Vestibular Schwannoma: Candidate Plasma Biomarkers in Vestibular Schwannoma

Vestibular schwannoma (VS) is intracranial tumor arising from neoplastic Schwann cells, causing hearing loss in about 95% of patients. The traditional belief that hearing deficit is caused by physical expansion of the VS, compressing the auditory nerve, does not explain the common clinical finding that patients with small tumors can have profound hearing loss, suggesting that tumor-secreted factors could influence hearing ability in VS patients. Here, we conducted profiling of patients' plasma for 67 immune-related factors on a large cohort of VS patients (N>120) and identified candidate biomarkers associated with tumor growth (IL-16 and S100B) and hearing (MDC). We identified the 7-biomarker panel composed of MCP-3, BLC, S100B, FGF-2, MMP-14, eotaxin, and TWEAK that showed outstanding discriminatory ability for VS. These findings revealed possible therapeutic targets for VS-induced hearing loss and provided a unique diagnostic tool that may predict hearing change and tumor growth in VS patients and may help inform the ideal timing of tumor resection to preserve hearing.

Tumor Biology and Microenvironment of Vestibular Schwannoma-Relation to Tumor Growth and Hearing Loss

Vestibular schwannoma is the most common benign neoplasm of the cerebellopontine angle. It arises from Schwann cells of the vestibular nerve. The first symptoms of vestibular schwannoma include hearing loss, tinnitus, and vestibular symptoms. In the event of further growth, cerebellar and brainstem symptoms, along with palsy of the adjacent cranial nerves, may be present. Although hearing impairment is present in 95% of patients diagnosed with vestibular schwannoma, most tumors do not progress in size or have low growth rates. However, the clinical picture has unpredictable dynamics, and there are currently no reliable predictors of the tumor's behavior. The etiology of the hearing loss in patients with vestibular schwannoma is unclear. Given the presence of hearing loss in patients with non-growing tumors, a purely mechanistic approach is insufficient. A possible explanation for this may be that the function of the auditory system may be affected by the paracrine activity of the tumor. Moreover, initiation of the development and growth progression of vestibular schwannomas is not yet clearly understood. Biallelic loss of the NF2 gene does not explain the occurrence in all patients; therefore, detection of gene expression abnormalities in cases of progressive growth is required. As in other areas of cancer research, the tumor microenvironment is coming to the forefront, also in vestibular schwannomas. In the paradigm of the tumor microenvironment, the stroma of the tumor actively influences the tumor's behavior. However, research in the area of vestibular schwannomas is at an early stage. Thus, knowledge of the molecular mechanisms of tumorigenesis and interactions between cells present within the tumor is crucial for the diagnosis, prediction of tumor behavior, and targeted therapeutic interventions. In this review, we provide an overview of the current knowledge in the field of molecular biology and tumor microenvironment of vestibular schwannomas, as well as their relationship to tumor growth and hearing loss.

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.

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.

Tumor-Associated Macrophages in Vestibular Schwannoma and Relationship to Hearing

Objective

(1) Characterize the distribution of M1 and M2 macrophages in vestibular schwannomas by hearing status. (2) Develop assays to assess monocyte migration and macrophage polarization in cocultures with vestibular schwannoma cells.

Study Design

Basic and translational science.

Setting

Tertiary care center.

Methods

A retrospective chart review of 30 patients with vestibular schwannoma (VS) was performed. Patients were stratified into serviceable and unserviceable hearing groups. Immunohistochemistry for CD80⁺ M1 and CD163⁺ M2 macrophages was conducted. Primary VS cultures (n = 4) were developed and cocultured with monocytes. Immunohistochemistry for macrophage markers was performed to assess monocyte migration and macrophage polarization.

Results

Although tumors associated with unserviceable hearing had higher levels of CD80 and CD163 than those with serviceable hearing, the relationship was only significant with CD163 (P = .0161). However, CD163 level did not remain a significant predictor variable associated with unserviceable hearing on multivariate analysis when adjusted for other variables. In vitro assays show that VS cells induced monocyte migration and polarization toward CD80⁺ M1 or CD163⁺ M2 macrophage phenotypes, with qualitative differences in CD163⁺ macrophage morphologies between serviceable and unserviceable hearing groups.

Conclusion

Vestibular schwannomas express varying degrees of CD80⁺ M1 and CD163⁺ M2 macrophages. We present evidence that higher expression of CD163⁺ may contribute to poorer hearing outcomes in patients with VS. We also describe in vitro assays in a proof-of-concept investigation that VS cells can initiate monocyte migration and macrophage polarization. Future investigations are warranted to explore the relationships between tumor, macrophages, secreted cytokines, and hearing outcomes in patients with VS.

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.

Losartan prevents tumor-induced hearing loss and augments radiation efficacy in NF2 schwannoma rodent models

Hearing loss is one of the most common symptoms of neurofibromatosis type 2 (NF2) caused by vestibular schwannomas (VSs). Fibrosis in the VS tumor microenvironment (TME) is associated with hearing loss in patients with NF2. We hypothesized that reducing the fibrosis using losartan, an FDA-approved antihypertensive drug that blocks fibrotic and inflammatory signaling, could improve hearing. Using NF2 mouse models, we found that losartan treatment normalized the TME by (i) reducing neuroinflammatory IL-6/STAT3 signaling and preventing hearing loss, (ii) normalizing tumor vasculature and alleviating neuro-edema, and (iii) increasing oxygen delivery and enhancing efficacy of radiation therapy. In preparation to translate these exciting findings into the clinic, we used patient samples and data and demonstrated that IL-6/STAT3 signaling inversely associated with hearing function, that elevated production of tumor-derived IL-6 was associated with reduced viability of cochlear sensory cells and neurons in ex vivo organotypic cochlear cultures, and that patients receiving angiotensin receptor blockers have no progression in VS-induced hearing loss compared with patients on other or no antihypertensives based on a retrospective analysis of patients with VS and hypertension. Our study provides the rationale and critical data for a prospective clinical trial of losartan in patients with VS.

Genomics, Epigenetics, and Hearing Loss in Neurofibromatosis Type 2

OBJECTIVES

In this review, we discuss current knowledge about the genetics and epigenetics of vestibular schwannoma (VS) in relation to hearing loss. A multistep and sequential genetic algorithm suitable for the identification of Neurofibromatosis Type 2 (NF2) constitutional and somatic mutations is discussed.

DATA SOURCES, STUDY SELECTION

A review was performed of the English literature from 1990 to 2019 using PubMed regarding genetics and epigenetics of vestibular schwannoma and NF2.

CONCLUSION

NF2 is a genetic disorder characterized by NF2 mutations that affect the function of a tumor suppressor called merlin. In particular, individuals with NF2 develop bilateral VS that can lead to hearing loss and even deafness. Recent advances in genetic and epigenetic studies have improved our understanding of the genotype-phenotype relationships that affect hearing in NF2 patients. Specific constitutional NF2 mutations including particular truncating, deletion, and missense mutations have been associated with poorer hearing outcomes and more severe clinical manifestations. Epigenetic events, such as DNA methylation and histone modifications, also contribute to the development and progression of hearing loss in NF2 patients. Furthermore, the accumulation of multiple NF2 and non-NF2 genetic and epigenetic abnormalities at the level of the tumor may contribute to worse hearing outcomes. Understanding genetic and epigenetic signatures in individual NF2 patients and particularly in each VS will allow us to develop novel gene therapies and precision medicine algorithms to preserve hearing in NF2 individuals.

Clinical severity of serum S100A12 levels in patients with osteoarthritis and S100A12 open inflammation of osteoarthritis model by NLRP3

Osteoarthritis is a common chronic bone and joint disease, which is characterized by degenerative changes and destruction of articular cartilage, secondary hyperostosis. This study aimed to investigate the clinical severity and mechanism of S100A12 in patients with osteoarthritis. Serum samples were obtained from patients with osteoarthritis or normal volunteer in Minhang Branch of Yueyang Hospital of Integrated Traditional Chinese and Western Medicine affiliated to Shanghai University of Traditional Chinese Medicine (Shanghai, China). C57BL/6J mice performed Resection of the medial collateral ligament and medial meniscus as mice model. MC3T3-E1 cells were induced with 100 ng of LPS as vitro model. The serum level of S100A12 was increased in patients with osteoarthritis. Similarly, S100A12 levels of serum and bone tissue from mice model of osteoarthritis were also higher than those of sham group. Over-expression of S100A12 promoted inflammation levels while down-regulation of S100A12 decreased inflammation levels in in vitro model of osteoarthritis. NLRP3 is an important target of S100A12 in pro-inflammation effects of osteoarthritis. NLRP3 was involved in the effects of S100A12 on inflammation in in vitro model of osteoarthritis. S100A12 also accelerated inflammation by NLRP3 in mice model of osteoarthritis. We conclude that serum S100A12 levels was a possible clinical severity, open inflammation of osteoarthritis model by NLRP3 and its receptors may be effective in preventing the development of osteoarthritis.

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.

The inflammatory microenvironment in vestibular schwannoma

Vestibular schwannomas are tumors arising from the vestibulocochlear nerve at the cerebellopontine angle. Their proximity to eloquent brainstem structures means that the pathology itself and the treatment thereof can be associated with significant morbidity. The vast majority of these tumors are sporadic, with the remainder arising as a result of the genetic syndrome Neurofibromatosis Type 2 or, more rarely, LZTR1-related schwannomatosis. The natural history of these tumors is extremely variable, with some tumors not displaying any evidence of growth, others demonstrating early, persistent growth and a small number growing following an extended period of indolence. Emerging evidence now suggests that far from representing Schwann cell proliferation only, the tumor microenvironment is complex, with inflammation proposed to play a key role in their growth. In this review, we provide an overview of this new evidence, including the role played by immune cell infiltration, the underlying molecular pathways involved, and biomarkers for detecting this inflammation in vivo. Given the limitations of current treatments, there is a pressing need for novel therapies to aid in the management of this condition, and we conclude by proposing areas for future research that could lead to the development of therapies targeted toward inflammation in vestibular schwannoma.