Predicting Basal Cochlear Length for Electric-Acoustic Stimulation

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Abstract
Over the last 5 years, a new implantation method, the combined electric-acoustic stimulation (EAS) of the inner ear, has been successfully implemented in several clinical studies.1-4 This method provides bimodal stimulation with a cochlear implant and a conventional hearing aid in the same ear. Candidates for EAS have relatively good residual hearing in the low frequencies (corresponding to apical parts of the cochlea) but substantial hearing loss in the high-frequency range, which makes adequate speech recognition impossible, even with high-power hearing aids. To ensure bimodal stimulation, at least some residual hearing must be preserved, and apical cochlear damage should be minimized. To this end, a properly performed EAS procedure stimulates the basal cochlear regions electrically while leaving the more apical portions free of an electrode carrier.1 These apical areas are responsible for low-frequency hearing and contain still-working structures, which can be stimulated with or without a conventional hearing aid, depending on the extent of residual function.