Effective, reproducible, and safe delivery of therapeutics into the inner ear is required for the prevention and treatment of hearing loss. A commonly used delivery method is via the posterior semicircular canal (PSCC); however, its specific targeting within the cochlea remains unclear, impacting precision and reproducibility. To assess safety and target specificity, we conducted in vivo recordings of the pharmacological manipulations delivered through the PSCC. Measurements of auditory brainstem response (ABR), vibrometry, and vestibular behavioral and sensory-evoked potential (VsEP) revealed preserved hearing and vestibular functions after artificial perilymph injections. Injection of curare, a mechanoelectrical transducer (MET) channel blocker that affects hearing when in the endolymph, had no effect on ABR or VsEP thresholds. Conversely, injection of CNQX, an AMPA receptor blocker, or lidocaine, a Na ⁺ channel blocker, which affects hearing when in the perilymph, significantly increased both thresholds, indicating that PSCC injections selectively target the perilymphatic space. In vivo tracking of gold nanoparticles confirmed their exclusive distribution in the perilymph during PSCC injection, supporting the pharmacological finding. Together, PSCC injection is a safe method for inner ear delivery, specifically targeting the perilymphatic space. Our findings will allow for precise delivery of therapeutics within the inner ear for therapeutic and research purposes.

Objective: Determine hearing protection use in relation to occupational noise exposure, tinnitus, and audiometry-measured hearing loss in the United States from 1999 to 2016. Study Design: Cross-sectional study utilizing US National Health and Nutritional Examination Survey (NHANES) 1999 to 2016 with occupation, reported occupational noise exposure, hearing protection use, tinnitus, and audiometry-measured hearing loss data. Subgroup analysis divided data into two cohorts early 2000s and 2010s. Setting: Population-based study using NHANES database capturing representative sample of US population. Participants: Individuals with complete data 1999 to 2004 (n = 10,347) and 2011 to 2012 with 2015 to 2016 (n = 9,383). Interventions: Participants self-reported occupational noise exposure lasting more than 4 h/d for more than 3 months. Self-reported hearing protective device uses and tinnitus frequency. Audiometric hearing loss objectively measured. Main Outcome Measures: Hearing protection use. Secondary measures included self-reported bothersome tinnitus and audiometrically measured hearing loss. Results: Across occupations, reported occupational noise exposure was higher in 2010s [32%, 95% CI: 29.6–34.6%] than 2000s [12.5%, 95% CI: 11.2–13.9%], while hearing protection use remained low in 2000s [41.3%, 95% CI: 37.8–44.8%] and 2010s [32.8%, 95% CI: 29.8–35.8%]. Less hearing protection use was associated with absence of bothersome tinnitus. Factors associated with increased hearing protection use were younger age, male sex, college education or higher, and white race in a multivariate model. Conclusions: Reported occupational noise exposure appeared to increase from 2000s to 2010s yet hearing protection use remained stable at low use rate. As noise exposure is a major risk factor for hearing loss, significant education and reinforcement of appropriate hearing protection use for workplace noise exposures is necessary to preserve workers’ hearing.

Background: Skull base tumors can extend into the temporal bone and occasionally even be visible through the tympanic membrane (TM) if they grow into the middle ear cavity. The differential diagnosis of a skull base mass is extensive and ranges from non-tumorous lesions like cholesteatoma to benign tumors like schwannoma and to malignant lesions like metastatic cancer. Optical coherence tomography (OCT) is a noninvasive imaging technique that can image tissue with high resolution in three dimensions, including through structures such as the TM and bone. OCT angiography is also able to assess tissue vascularity. We hypothesized that OCT could help shrink the differential diagnosis in clinic on the day of initial presentation. Specifically, we thought that OCT angiography could help distinguish between highly vascular skull base tumors such as glomus jugulare and other less vascular tumors and middle ear pathologies such as cholesteatoma and schwannoma. Objectives: We sought to determine whether OCT can image through the TM in clinic to distinguish a normal ear from an ear with a mass behind the tympanic membrane. Furthermore, we sought to assess whether OCT angiography can detect vascularity in these masses to help inform the diagnosis. Methods: We designed and built a custom handheld OCT system that can be used like an otoscope in clinic. It is based off a 200 kHz swept-source laser with a center wavelength of 1310 nm and a bandwidth of 39 nm. It provides a 33.4 μm axial and 38 μm lateral resolution. Cross-sectional images of the middle ear space, including OCT angiography, were captured in an academic neurotology clinic. Patients with normal ear exams, glomus tumors, cholesteatomas, and facial nerve schwannoma were imaged. Results: OCT images revealed key structures within the middle ear space, including the TM, ossicles (malleus and incudostapedial joint), chorda tympani, and cochlear promontory. OCT also identified middle ear pathology (using pixel intensity ratio in the middle ear normalized to the TM) when compared with patients with normal ear exams (mean 0.082, n = 6), in all patients with a glomus tumor (mean 0.620, n = 6, p < 0.001), cholesteatoma (mean 0.153, n = 4, p < 0.01), and facial nerve schwannoma (0.573, n = 1). OCT angiography revealed significant vascularity within glomus tumors (mean 1.881, n = 3), but minimal vascularity was found in normal ears (mean 0.615, n = 3, p < 0.05) and ears with cholesteatoma (mean 0.709, n = 3, p < 0.01), as expected. Conclusions: OCT is able to image through the TM and detect middle ear masses. OCT angiography correctly assesses the vascularity within these masses. Thus, OCT permits the clinician to have additional point-of-care data that can help make the correct diagnosis.

Introduction: Treatment of vestibular schwannoma (VS) has been extensively studied, but a gap in knowledge exists demonstrating how racial and socioeconomic status influence VS presentation. Our institution has a unique setting with a public safety net hospital (PSNH) and tertiary academic medical center (TAMC) in the same zip code, which we study to evaluate initial VS presentation disparities in patient populations presenting to these hospital settings. Methods: Retrospective chart review was performed of all adult patients (n = 531) presenting 2010 to 2020 for initial VS evaluation at TAMC (n = 462) and PSNH (n = 69). Ethnicity, insurance, maximum tumor size, audiometry, initial treatment recommendation, treatment received, and follow up were recorded and statistical analysis performed to determine differences. Results: Average age at diagnosis (51.7 ± 13.6 TAMC vs 52.3 ± 12.4 PSNH) and gender (58.4% TAMC vs 52.2% PSNH female) were similar. Patients’ insurance (TAMC 75.9% privately insured vs PSNH 82% Medicaid) and racial/ethnic profiles (TAMC 67.7% White and 10.0% Hispanic/Latinx, vs PSNH 4.8% White but 59.7% Hispanic/Latinx) were significantly different. Tumor size was larger at PSNH (20.2 ± 13.3 mm) than TAMC (16.6 ± 10.0 mm). Hearing was more impaired at PSNH than TAMC (mean pure tone average 58.3 dB vs 43.9 dB, word recognition scores 52.3% vs 68.2%, respectively). Initial treatment recommendations and treatment received may include more than 1 modality. TAMC patients were offered 66.7% surgery, 31.2% observation, and 5.2% radiation, while PSNH patients offered 50.7% observation, 49.3% surgery, and 8.7% radiation. TAMC patients received 62.9% surgery, 32.5% observation, and 5.3% radiation, while PSNH patients received 36.2% surgery, 59.4% observation, and 14.5% radiation. Follow up and treatment at the same facility was not significantly different between hospitals. Conclusions: Hearing was worse and tumor size larger in patients presenting to PSNH. Despite worse hearing status and larger tumor size, the majority of PSNH patients were initially offered observation, compared to TAMC where most patients were initially offered surgery.

Novel therapeutic delivery systems and delivery methods to the inner ear are necessary to treat hearing loss and inner ear disorders. However, numerous barriers exist to therapeutic delivery into the bone-encased and immune-privileged environment of the inner ear and cochlea, which makes treating inner ear disorders challenging. Nanoparticles (NPs) are a type of therapeutic delivery system that can be engineered for multiple purposes, and posterior semicircular canal (PSCC) infusion is a method to directly deposit them into the cochlea. We sought to assess PSCC infusion of gold NPs into the cochlea, including the NPs’ distribution and effect on cochlear mechanics. We performed optical coherence tomography (OCT) imaging to monitor PSCC infusion of gold NPs into the cochlear chambers. OCT imaging demonstrated that the infusion specifically targeted the perilymphatic spaces within the cochlea. We assessed cochlear mechanics by using OCT vibrometry to measure sound-evoked movements of the basilar membrane. We found no changes in cochlear mechanics between measurements at baseline, after the PSCC canalostomy, immediately after the infusion, and 1 h after the infusion of gold NPs (p > 0.05, paired t-test). These findings validate the PSCC infusion approach for perfusing the cochlear perilymphatic space with a nanoparticle delivery system. Thus, PSCC infusion of nanoparticles is a feasible therapeutic delivery technique for treating inner ear disorders while preserving residual cochlear function.