Relative Importance of Monaural Sound Deprivation and Bilateral Significant Hearing Loss in Predicting Cochlear Implantation Outcomes

Objectives: Making evidence-based recommendations to prospective unilateral cochlear implant recipients on the potential benefits of implanting one or the other ear is challenging for cochlear implant teams. This particularly occurs in cases where a hearing aid has only been used in one ear for many years (referred to here as the "hearing ear"), and the contralateral ear has, in essence, been sound-deprived. In such cases, research to date is inconclusive, and little anecdotal evidence exists to inform the debate and support best clinical practice.

Design: Retrospective data on speech recognition outcomes of 16 adult participants who received a cochlear implant in an ear deprived of sound for a minimum of 15 yr were analyzed. All subjects were implanted through the Quebec Cochlear Implant Program and were provided with personalized intensive rehabilitation services. Data obtained from clinical records included demographic data and speech recognition scores measured after implantation with the sentences of a multimedia auditory test battery in the auditory-only condition. Speech recognition outcomes were compared with the duration of auditory deprivation in the implanted ear, bilateral significant hearing loss, and auditory stimulation before bilateral significant hearing loss.

Results: Using nonparametric correlation analyses, a strong negative correlation was demonstrated between speech recognition scores and the duration of bilateral significant hearing loss and with the duration of auditory stimulation before bilateral significant hearing loss. No significant correlation with the duration of auditory deprivation or with the duration of prior auditory stimulation in the implanted ear was found.

Conclusions: These findings suggest that functional outcomes of cochlear implantation for unilateral sound deprivation may be more strongly influenced by central processes than peripheral effects stemming from the deprivation per se. This indicates the relevance of considering the client's history of binaural hearing rather than the hearing in each ear individually when discussing possible outcomes with a cochlear implant.