Anatomy-based fitting for cochlear implant recipients

Frequency-to-place mismatch is the discrepancy between the frequency information delivered by a cochlear implant electrode and the natural cochlear place frequency location that is stimulated. Frequency-to-place mismatch has been shown to negatively influence cochlear implant outcomes. Anatomy-based fitting (ABF) aligns filter frequencies with cochlear frequency place to minimize or eliminate frequency-to-place mismatches. This article reviews the current evidence on variability in electrode array placement, influence of frequency-to-place mismatches on cochlear implant recipient outcomes, and effectiveness of ABF procedures.

Most ABF procedures identify the angular insertion depth of the electrode contacts using imaging, calculate the cochlear place frequency, and then adjust filter frequencies for each electrode contact to match the cochlear place frequencies. While the specific approach varies across ABF procedures, studies generally report improvements in speech recognition in noise, music perception, user satisfaction, and/or sound quality as compared to default maps. What remains unclear are the long-term outcomes between default and ABF procedures, if there is a preferred frequency-to-place function when determining cochlear place, and whether there is an optimal ABF procedure for cochlear implant and electric-acoustic stimulation device users.

Early evidence of cochlear implant recipients listening with ABF maps demonstrates better results compared to maps with default settings.