Natural history of contralateral residual hearing in unilateral cochlear implant users – long-term findings

CONCLUSION: The long-term stability of low-frequency residual hearing found in a significant number of bilateral-bimodal users (cochlear implant (CI) in one ear and a hearing aid (HA) on the other ear; CI/HA) with severe-to-profound or profound hearing loss in the non-implanted ear justifies bilateral-bimodal fitting efforts in this group. Since low-frequency residual hearing tends to deteriorate in some of these CI/HA users, periodic evaluation, which includes pure-tone thresholds and speech perception tests, is mandatory for determining the point in time at which CI/HA hearing is no longer effective, and the patient should accordingly be considered as a candidate for contralateral cochlear implantation. OBJECTIVE: To determine, in bilateral-bimodal (CI/HA) users with severe-to-profound or profound hearing loss in the non-implanted ear, the rate of residual hearing deterioration in the non-implanted ear after cochlear implantation. METHODS: Pure-tone aided and unaided thresholds in the non-implanted ears of 39 CI/HA users at 0.25-4.0 kHz were recorded prospectively up to 6 years after implantation. RESULTS: Group mean threshold values in the non-implanted ears remained stable over 3, 4, 5 and 6 years post-implantation, except for significant deterioration at 4.0 kHz of both unaided (4.2, 5.2, 9.0 and 8.2 dB, respectively) and aided thresholds (8.1, 4.6, 6.1 and 8.3 dB, respectively).