Comparing Cochlear Implant with Hearing Aid to Bilateral Microphone Inputs for Unilateral Cochlear Implant Users

This study aimed to evaluate (a) whether the use of bilateral microphones with a unilateral cochlear implant system is better than the use of a single microphone input, and (b) whether the use of a single implant system with bilateral microphone inputs is better than the use of a hearing aid with a cochlear implant. Six adults were evaluated under three listening conditions: cochlear implant and hearing aid (CIHA), cochlear implant with unilateral microphone (CI-UM) and cochlear implant with bilateral microphones (CI-BM). Performance measures included dichotic speech perception in noise, horizontal localisation and functional performance in real life. The results of speech testing showed a significant advantage of CIHA and CI-BM over CI-UM. The localisation task showed that CIHA was significantly better than CI-BM or CI-UM. The functional performance questionnaires showed that CIHA was better than CI-UM, and similar to or better than CI-BM in real-life situations. The subjects also commented on the improved quality of sound provided by the use of a hearing aid with a cochlear implant. We conclude that both CIHA and bilateral microphones with a single implant can provide real advantages for dichotic speech perception in noise over an implant system with a single microphone input when speech originated from the non-implanted side. CIHA provided extra benefits in localisation and functional performance in real life, and is the option of choice for users of unilateral cochlear implants who have some residual hearing in the non-implanted ear.