Assessing binaural/bimodal advantages using auditory event-related potentials in subjects with cochlear implants.

OBJECTIVE: To assess the advantage of binaural and bimodal hearing for subjects with cochlear implant (CI) using auditory event-related potentials as well as speech perception tests.

SUBJECTS AND METHODS: The subjects comprised four binaural CI users (CI/CI group) and eleven bimodal CI users, who wore a hearing aid (HA) contralaterally (CI/HA group). All subjects had used binaural or bimodal fitting for over 6 months. Their speech perception was examined in a quiet environment using monosyllabic words. Late cortical waves were measured while subjects were engaged in an oddball task of 1kHz frequent and 2kHz rare tone stimuli. The latencies of event-related potential (N1, N2, P3) were compared for monaural, binaural, and bimodal hearing conditions.

RESULTS: Significantly (p<0.01, paired t-test) better speech perception for monosyllabic words was found for both binaural and bimodal hearing than monaural hearing. The latency of N1 did not significantly change for either binaural or bimodal hearing. On the other hand, the latency of N2 was significantly (p<0.01, paired t-test) shorter for binaural and bimodal hearing than for monaural hearing. The latency of P3 was shorter for binaural and bimodal hearing than monaural hearing in all subjects, and the difference was statistically significant in both CI/CI and CI/HA groups (p<0.01, paired t-test).

CONCLUSIONS: Better speech perception was obtained for binaural and bimodal hearing than for monaural hearing in CI subjects. The results obtained in the comparison of P3 latency agreed with that of speech perception. Thus, using bilateral hearing devices is recommended for CI subjects. We also found that event-related potentials were useful as an objective tool to assess the advantage of binaural and bimodal hearing for CI subjects.