Abstract
Auditory localization and the cocktail party effect are examples of the advantages of dichotic hearing. Bilateral cochlear implants have already begun to be used in many countries, and been reported to enable good performances of the patients in speech recognition tasks. In Japan, cochlear implant users generally use a hearing aid for the opposite ear, because the benefits of use of a hearing aid for contralateral ears have been reported by many studies from other countries. We examined the benefits of use of a hearing aid for the contralateral ear in Japanese patients under silent and noisy conditions. Under the silent condition, there was no significant difference in the hearing ability between subjects with unilateral cochlear implants and those with unilateral cochlear implants with a hearing aid for the contralateral ear. According to further analyses taking into consideration other components, such as the period of wearing, hearing ability of the contralateral ear and that of the cochlear implant, no benefits were observed. Under the noisy condition also, no significant difference in the hearing ability was observed between the two groups. Some causes are suggested for the absence of the benefits of contralateral hearing aids in the present study: stringent criteria for the fitting of cochlear implants; the small number of cases in the study; the phonemic features of Japanese. To improve the hearing ability in cochlear implant users, we suggest aggressive use of the contralateral ears, using bilateral cochlear implants if necessary.
