In many countries, a single
cochlear implant is offered as a treatment for a
bilateral hearing loss. In cases where there is asymmetry in the amount of sound deprivation between the ears, there is a dilemma in choosing which ear should be implanted. In many clinics, the choice of ear has been guided by an assumption that the reorganisation of the auditory pathways caused by longer duration of
deafness in one ear is associated with poorer implantation outcomes for that ear. This assumption, however, is mainly derived from studies of early childhood
deafness. This study compared outcomes following implantation of the better or poorer ear in cases of long-term hearing asymmetries. Audiological records of 146 adults with
bilateral hearing loss using a single
hearing aid were reviewed. The unaided ear had 15 to 72 years of unaided severe to profound
hearing loss before unilateral
cochlear implantation. 98 received the implant in their long-term sound-deprived ear. A multiple regression analysis was conducted to assess the relative contribution of potential predictors to speech recognition performance after implantation. Duration of bilateral significant
hearing loss and the presence of a prelingual
hearing loss explained the majority of variance in speech recognition performance following
cochlear implantation. For participants with postlingual
hearing loss, similar outcomes were obtained by implanting either ear. With prelingual
hearing loss, poorer outcomes were obtained when implanting the long-term sound-deprived ear, but the duration of the sound deprivation in the implanted ear did not reliably predict outcomes. Contrary to an apparent clinical consensus, duration of sound deprivation in one ear has limited value in predicting speech recognition outcomes of
cochlear implantation in that ear. Outcomes of
cochlear implantation are more closely related to the period of time for which the brain is deprived of auditory stimulation from both ears.