Abstract
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.
Highlights
Cochlear implants have been dubbed ''the most successful of all neural prostheses'' [1], helping to partly restore hearing in more than 300 000 people around the world [2]
For most adults receiving a cochlear implant, only one ear is implanted despite a bilateral hearing loss
This study aimed to examine the effects of unilateral sound deprivation on cochlear implantation outcomes in patients with bilateral hearing loss
Summary
Cochlear implants have been dubbed ''the most successful of all neural prostheses'' [1], helping to partly restore hearing in more than 300 000 people around the world [2]. There is, a relative lack of evidence to guide clinicians in choosing the best ear for implantation. This is the case for adult patients with asymmetric hearing thresholds or different durations of sound deprivation in each ear where they perceive one ear to be “better” and the other “poorer”. In these situations, clinicians and patients face the dilemma of either choosing to implant the poorer ear, where the outcomes are unknown, or risk implanting the better ear where residual hearing may be lost. This study aimed to examine the effects of unilateral sound deprivation on cochlear implantation outcomes in patients with bilateral hearing loss
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