Association of Tonotopic Mismatch and Cochlear Implant Use on Outcomes for Adults With Unilateral Hearing Loss

Review whether tonotopic mismatch and device use are associated with speech recognition for adult cochlear implant (CI) users with unilateral hearing loss (UHL).

Performance with the CI alone (CNC word scores) and in the CI plus the normal hearing (NH) ear condition (CI + NH; BKB-SIN scores) at 6 months post-activation was reviewed. For BKB-SIN, the target was presented from the front and the masker was presented toward the NH ear. Mismatch for the most apical electrode contact was determined using imaging and the filter frequencies of each patient's familiar map. Device use was obtained from datalogging reports.

For the 32 CI recipients, mismatch ranged from -27 to 21 semitones (mean: -8; SD: 10). Mismatch was not significantly associated with CNC scores (r ₍₃₂₎ = -0.25, p = 0.083) but was with BKB-SIN scores (r ₍₂₆₎ = 0.38, p = 0.030). Device use ranged from 1 to 14 h (mean: 7; SD: 5). Device use was significantly associated with CNC (r ₍₂₄₎ = 0.56, p = 0.002) and BKB-SIN (r ₍₂₁₎ = -0.49, p = 0.012) scores. The relationship between mismatch and device use was not significant (r ₍₂₄₎ = -0.11, p = 0.308).

CI users with UHL experienced better speech recognition when tonotopic mismatches were minimal or not present, and when they listened to their CI for multiple hours a day. These data suggest that CI users with UHL may experience their best performance with consistent device use and when listening to maps with minimal or no tonotopic mismatch. The lack of a significant association between mismatch and device use suggests other variables may be influencing the consistency of device use.