Unilateral Hearing Loss: Understanding Speech Recognition and Localization Variability-Implications for Cochlear Implant Candidacy.
Jill B Firszt, Ruth M Reeder, Laura K Holden
PMID 28067750WHAT IT FOUND
Adults with one deaf ear struggled with speech in noise and localization compared to two-eared listeners.
However, those deaf since birth localized better than those who lost hearing recently. Better-ear hearing levels predicted speech difficulties, suggesting candidacy for cochlear implants depends on specific functional deficits rather than just the presence of unilateral loss.
Key findings
01Unilateral listeners (both deaf and simulated deaf) understood speech in noise significantly worse than bilateral listeners, with mean differences equating to 22-31 percentage points less intelligibility.
02Participants with onset of severe hearing loss before age three localized sounds more accurately than those with recent onset, despite similar speech-in-noise performance.
03Hearing thresholds in the better ear correlated with speech recognition abilities in the unilateral group, indicating that small differences in better-ear hearing impact function more in this population than in normal-hearing individuals.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study included a relatively small sample of 26 UHL participants, limiting the generalizability of subgroup findings such as the effect of age at onset. The NH-unilateral group simulated deafness with earplugs and muffs, which provided approximately 48 dB of attenuation; this may not perfectly replicate the neural experience of true unilateral deafness. The study did not include participants with mild-to-moderate unilateral hearing loss, so findings apply specifically to severe-to-profound cases. Variability in performance was high among UHL participants, indicating that group averages may not predict individual patient outcomes accurately.
Declared interests
The research was supported by N.I.H. Extramural funding. The authors declared no conflicts of interest.
The easy way to misread this
Do not assume that all individuals with unilateral hearing loss will benefit equally from cochlear implantation for localization. Those with early-onset deafness may have already developed compensatory localization skills, meaning the implant might offer less benefit for localization than expected, though speech-in-noise deficits remain significant.