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

In Brief 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. Selecting the most appropriate ear for cochlear implantation with individuals who have been monaurally deprived of hearing for many years is a challenging issue. Some advocate for implanting the most recently stimulated ear, while others will suggest preserving the only stimulated ear. This is a retrospective study of adult participants who received an implant in an ear deprived of hearing for a minimum of 15 yr. The strong relationship found between speech recognition results after implantation and the variables measured in the recently stimulated ear (nonimplanted) suggests that outcomes for unilateral sound deprivation are strongly influenced by central processes.