ABSTRACT
OBJECTIVE: To evaluate the efficacy of sound stimulation for enhancing drug distribution in the cochlea's perilymph, crucial for treating one of the most inaccessible organs and a major disability factor worldwide. DESIGN: A systematic scoping review following PRISMA guidelines was conducted, analysing studies on cochlear fluid dynamics influenced by sound stimulation. Data were collected from PubMed and Google Scholar using both MeSH and non-MeSH terms, with exclusions for unrelated topics. STUDY SAMPLE: Thirteen studies met the inclusion criteria, providing insights into the mechanics of cochlear perilymphatic flow and its potential enhancement through sound stimulation. RESULTS: The review highlights two primary mechanisms capable of inducing significant perilymphatic flow from the base towards the apex: complex audible sound stimulation creating a "streaming channel" and low-frequency stimulation at high intensity. Despite the theoretical potential, the clinical applicability of these techniques remains unproven, and the safety of low-frequency, high-intensity stimulation for the cochlea and vestibular system should be demonstrated. CONCLUSIONS: Sound stimulation appears to be a viable method for inducing perilymphatic movements, potentially improving drug delivery to remote cochlear regions. Future research should focus on the clinical safety and efficacy of these stimulations to fully utilise this approach in therapeutic applications.
ABSTRACT
OBJECTIVE: Severely asymmetrical hearing loss (SAHL) is characterized by a moderately severe or severe hearing loss in one side and normal or mildly impaired controlateral hearing in the other. The Active tri-CROS combines the Contralateral Routing-of-Signal System (CROS, or BiCROS if the best ear is stimulated) and the stimulation of the worst ear by an in-the-canal hearing aid. This study aims to evaluate the benefit of the Active tri-CROS for SAHL patients. STUDY DESIGN: This retrospective study was conducted from September 2019 to December 2020. SETTING: Ambulatory, tertiary care. PATIENTS: Patients were retrospectively included if they had received the Active tri-CROS system after having used a CROS or BiCROS system for SAHL for at least 3 years. MAIN OUTCOME MEASURES: Audiometric gain, signal-to-noise ratio, spatial localization, and the Abbreviated Profile of Hearing Aid Benefit and Tinnitus Handicap Inventory questionnaires were performed before equipment and after a month with the system. RESULTS: Twenty patients (mean, 62 yr old) with a mean of 74.3 ± 8.7 dB HL on the worst ear were included. The mean tonal hearing gain on the worst ear was 20 ± 6 dB. Signal-to-noise ratio significantly rose from 1.43 ± 3.9 to 0.16 ± 3.4 dB ( p = 0.0001). Spatial localization was not significantly improved. The mean Tinnitus Handicap Inventory test score of the eight patients suffering from tinnitus rose from 45.5 ± 18.5 to 31 ± 25.2 ( p = 0.016). CONCLUSIONS: The Active tri-CROS system is a promising new therapeutically solution for SAHL.