Binaural Benefits for Adults Who Use Hearing Aids and Cochlear Implants in Opposite Ears

In Brief Objective This study aimed to investigate 1) how a hearing aid needs to be adjusted for an adult who uses a cochlear implant in the contralateral ear; 2) whether the use of a hearing aid with a cochlear implant leads to interference; and 3) whether adults derive binaural benefits from using a hearing aid with a cochlear implant for speech perception, localization, and functional performance in everyday life. Design Twenty-one adults (11 female and 10 male) who used either a Nucleus CI-22 (N = 3) or a Nucleus CI-24 (N = 18) cochlear implant system in one ear participated in this study. Twelve of the adults were experienced hearing aid and implant users, whereas nine did not use a hearing aid after implantation. The hearing aids were fitted using the NAL-NL1 prescription, and fine-tuned for each individual by using a paired-comparisons test to identify the frequency response that was best for understanding speech, and a loudness balancing test to find the hearing aid gain that gave the same overall loudness as that perceived in the ear with a cochlear implant. Effects from using a hearing aid with a cochlear implant (bimodal hearing) were assessed by three measures. These included speech perception in noise in diotic and dichotic listening conditions, horizontal localization, and functional performance in everyday life. Performance with cochlear implant and hearing aid (CIHA) was compared with that with cochlear implant alone (CI) and hearing aid alone (HA). Results The NAL-NL1 prescribed appropriate frequency response slope on average, and the mean gain needed for binaural loudness balance was 4 dB lower than the prescribed gain. Individual variations in preferences suggest that it is desirable to fine-tune the hearing aid response slope and gain according to individual needs. The speech test results indicated that the CIHA scores were significantly better than the CI or the HA scores. Localization test results showed that the adults made significantly less error when locating a sound source using CIHA compared with CI or HA. Functional performance questionnaire scores for CIHA were significantly higher than CI scores or HA scores. All adults showed binaural benefits in at least one performance measure. On average, those who derived greater speech benefits also made less localization error and functioned more effectively in real life. Conclusions The results clearly indicate that binaural advantages can be obtained from using a hearing aid with a cochlear implant in opposite ears. It is recommended that bimodal stimulation be standard practice for rehabilitation of adults who wear unilateral cochlear implants. A hearing aid should be fitted to the nonimplanted ear using the NAL-NL1 prescription as a starting point, and the frequency response slope and gain could be fine-tuned to suit individual needs. People who receive unilateral cochlear implants cannot hear with both ears. One option to provide binaural hearing is to fit a hearing aid in the nonimplanted ear. This article determined the hearing aid amplification requirements of adults who used hearing aids and cochlear implants in opposite ears (bimodal hearing) by using a paired-comparisons and a loudness balancing procedure; and examined binaural benefits by measuring speech perception, localization, and functional performance in real life. Benefits were quantified in terms of difference in performance between the implant and hearing aid (CIHA) condition and the implant alone (CI) condition. Results indicated that the NAL-NL1 prescribed appropriate frequency response and gain on average. All adults showed binaural benefits in at least one performance measure. On average, those who derived greater speech benefits also made fewer localization errors and functioned more effectively in real life. It is recommended that bimodal hearing be standard practice for rehabilitation of adults who receive unilateral cochlear implants.