Monaural sound deprivation; opening a window on central processes underlying cochlear implantation outcomes

• When considering unilateral cochlear implantation, clinicians must decide which ear should be implanted. This decision process is made more complex in the case of long-term monaural sound-deprivation where a hearing aid is used in the non-deprived ear. Clinical recommendations are not uniform where some clinicians suggest implanting the sound-deprived ear, regardless of the length of deprivation, to preserve the remaining hearing of the non-deprived ear. Others recommend implanting the non-deprived ear, arguing that implanting a recently stimulated ear provides higher outcomes with the implant. The literature discussing implanting the “better” or “worse” ear is inconclusive and none have specifically compared outcomes of implantation in ears with long-term monaural sound-deprivation.The current study draws its findings from cochlear implant centres located in 3 countries. Comparative analyses of cochlear implantation outcomes obtained in adults with monaural sound-deprivation of durations ranging from 15 to 65 years and implanted in the non-deprived (n≈90) or sound-deprived ear (n≈100) have been conducted. The results show that similar functional outcomes can be achieved by both groups when comparing the everyday listening condition (cochlear implant alone or bimodal hearing [i.e. cochlear implant in one ear and hearing aid in the other]). Moreover, higher outcomes were obtained after cochlear implantation by individuals with a long-term monaural sound-deprivation compared to individuals with a long-term bilateral sound-deprivation (n≈15), irrespective of which ear was implanted. These results pave the way to a discussion about central processes underlying cochlear implantation outcomes.

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