Estimation of the degree of inner and outer hair cell dysfunction from distortion product otoacoustic emission input/output functions

Abstract

Cochlear hearing loss is one of the most common forms of disability. It frequently relates to selective or combined dysfunction of inner (IHCs) and outer hair cells (OHCs). Current clinical methods do not allow an accurate estimation of the degree of dysfunction of each cell type, yet such estimation could be highly informative for optimizing hearing aid fitting. Here, it is proposed that the degree of IHC and OHC dysfunction may be estimated from DPOAE input/output curves. It is argued that the controversial aspects of the interpretation of these curves may be elucidated by comparing DPOAE input/output curves with corresponding cochlear input/output curves inferred psychophysically in the same subject. The evidence in support of these ideas is reviewed. We conclude that DPOAE input/output curves obtained with current standard clinical parameters may be used to infer the degree of IHC and OHC dysfunction at 4 kHz but not at lower frequencies. Ideas for further research are presented and discussed.