Mechanisms and Effects of Hearing Loss After Cochlear Implantation

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Project Summary Approximately 22 million Americans have a hearing impairment. Cochlear implants (CIs), a neural prosthesis developed to treat severe hearing loss, have significantly improved speech understanding in quiet for many individuals with hearing loss. However, benefit remains highly variable across the patient population, and speech understanding in noise remains a problem. A recent advance is the Electro-Acoustic Stimulation (EAS) CI, which allows combined electric and acoustic stimulation in the same ear. EAS dramatically improves speech perception in noise, voice recognition, and musical melody recognition. These benefits are proportional to the amount of residual hearing preserved after cochlear implantation. However, 30-55% of EAS CI recipients lose more than 30 dB of residual hearing after implantation, which can negate these benefits. In addition, increased age is associated with greater hearing loss. In order to improve hearing preservation and EAS outcomes, we need to understand the mechanisms of post-implantation hearing loss. Hearing preservation may also improve outcomes for the general CI population. Traditional CI users with hearing preservation have better outcomes even with just the CI alone, suggesting a relationship between hearing preservation and effectiveness of electrical stimulation. In order to improve CI outcomes for all patients, it is critical to understand how and why CI performance is related to residual hearing preservation. In this proposal, we will investigate 1) the potential mechanisms of hearing loss after implantation, and the interaction with age; and 2) the impact of this hearing loss on electrical stimulation with the CI. The findings will guide the selection of more targeted drugs or treatments that improve hearing preservation and general outcomes with CIs.