The influence of different speech processor and hearing aid settings on speech perception outcomes in electric...

Electric acoustic stimulation (EAS) is an increasingly popular means of treating individuals with a steeply sloping mid-to-high frequency hearing loss, who traditionally do not benefit from hearing instruments. These persons often have too much residual hearing to be considered for a cochlear implant. Several studies have demonstrated the ability both to preserve the remaining low-frequency hearing in these individuals, and to provide significant benefit through combining a cochlear implant with a hearing aid to amplify the same ear. These improvements in performance have been especially noted in noise. Often overlooked is that these outcomes may be influenced by the fitting parameters of both the cochlear implant and the hearing aid.

This study assessed four EAS subjects, with a minimum of 1 month's EAS use, on eight different fitting parameters. Sentence testing in different noise levels (+15, +10, and +5 dB SPL) was conducted. Subjects also evaluated each condition using a visual analogue scale.

Results demonstrated that a reduced overlap of cochlear implant and hearing aid amplification produced best results across listening conditions.

The hearing aid should be fit to a patient-specific modified audiogram at least up to the point where low-frequency hearing is not measurable. The cochlear implant should be fit from a higher frequency point than is standard in patients without residual hearing in the implanted ear, to provide reduced overlap with the amplification provided by the hearing aid. Therefore, a small amount of overlap between the frequency ranges used by the hearing aid and the cochlear implant seems beneficial.