Cochlear implant (CI) recipients with unilateral hearing loss reached early asymptote for binaural hearing abilities, and CI recipients with asymmetric hearing loss continued to improve out to 5-years post-activation for spatial release from masking when the masker was presented toward the better hearing ear. There was a significant correlation with improvement and age at implantation and contralateral hearing thresholds which may influence these differences.
Objective
To assess long-term binaural hearing abilities for cochlear implant (CI) users with unilateral hearing loss (UHL) or asymmetric hearing loss (AHL).
Methods
A prospective, longitudinal, repeated measures study was completed at a tertiary referral center evaluating adults with UHL or AHL undergoing cochlear implantation. Binaural hearing abilities were assessed with masked speech recognition tasks using AzBio sentences in a 10-talker masker. Performance was evaluated as the ability to benefit from spatial release from masking (SRM). SRM was calculated as the difference in scores when the masker was presented toward the CI-ear (SRMci) or the contralateral ear (SRMcontra) relative to the co-located condition (0°). Assessments were completed pre-operatively and at annual intervals out to 5 years post-activation.
Results
Twenty UHL and 19 AHL participants were included in the study. Linear Mixed Models showed significant main effects of interval and group for SRMcontra. There was a significant interaction between interval and group, with UHL participants reaching asymptotic performance early and AHL participants demonstrating continued growth in binaural abilities to 5 years post-activation. The improvement in SRM showed a significant positive correlation with contralateral unaided hearing thresholds (p = 0.050) as well as age at implantation (p = 0.031).
Conclusions
CI recipients with UHL and AHL showed improved SRM with long-term device use. The time course of improvement varied by cohort, with the UHL cohort reaching asymptotic performance early and the AHL cohort continuing to improve beyond 1 year. Differences between cohorts could be driven by differences in age at implantation as well as contralateral unaided hearing thresholds.
Level of Evidence
Level III Laryngoscope, 2022
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