Significant influence of prelingual deafness but less impact of elderly age at implantation on long-term psychoacoustic CI programming parameters

Objective

This study aimed to elucidate the long-term impact of prelingual deafness and elderly age at cochlear implantation on cochlear implant (CI) programming parameters and CI thresholds

Methods

We retrospectively reviewed patients who underwent cochlear implantation less than 5 years (Prelingual group) and equal and more than 18 years in our institute. The latter group was further divided into Adult and Elderly groups according to whether the patient was younger or older than 65 at implantation. From 152, 69, and 55 patients in the Prelingual, Adult, and Elderly groups, 242, 92, and 58 ears were included. We compared CI thresholds and CI programming parameters, including impedances, T/C levels, and dynamic ranges for 8 years after implantation between the Prelingual, Adult, and Elderly groups.

Results

The Prelingual group showed consistently lower CI thresholds than the Adult and Elderly groups during the postoperative 2-8 years, but no difference was detected between the Elderly and Adult groups, except at the postoperative 4 years. The elderly group's CI thresholds did not deteriorate until postoperative 8 years. The Prelingual group showed consistently larger T/C levels (minimum/maximum current strength from CI), especially C levels, than the other two groups. At the same time, there was no significant difference between the Elderly and Adult groups except for smaller dynamic ranges in the Elderly group until postoperative 2 years. These results in the CI programming parameters might explain the lower CI thresholds in the Prelingual group than in the other groups. Focusing on CI maps 1 and 3 years after implantation, the strength of the T/C levels was similar for all channels in the Prelingual group, but the Adult and Elderly groups showed larger electrical stimuli in channels responsible for the middle frequencies than those for the lower or higher frequencies.

Conclusions

Our results suggest a significant influence of prelingual deafness but less impact of elderly age at implantation on long-term CI programming parameters and CI thresholds. The larger C levels and lower CI thresholds in the Prelingual group than in the Adult and Elderly groups implied that CI children with prelingual deafness tolerate and prefer larger CI stimuli, which may reflect the CI-dependent development of their auditory system before the critical period. No age-related reduction in hearing thresholds was observed in the Elderly group, probably because the CI compensates for age-related dysfunction of the peripheral auditory system.