Long-Term Improvement in Localization for Cochlear Implant Users with Single-Sided Deafness

Objectives/hypothesis: To assess whether early, significant improvements in sound source localization observed in cochlear implant (CI) recipients with normal hearing (NH) in the contralateral ear are maintained after 5 years of CI use.

Study design: Prospective, repeated measures study.

Methods: Participants were recruited from a sample of CI + NH listeners (n = 20) who received their device as part of a prospective clinical trial investigating outcomes of CI use for adult cases of single-sided deafness. Sound source localization was assessed annually after the clinical trial endpoint (1-year post-activation). Listeners were asked to indicate the perceived sound source for a broadband noise burst presented randomly at varied intensity levels from one of 11 speakers along a 180° arc. Performance was quantified as root-mean-squared (RMS) error.

Results: Linear mixed models showed superior post-activation performance was maintained with long-term CI use as compared to preoperative abilities (P < .001). Unexpectedly, a significant improvement (P = .009) in sound source localization was observed over the long-term post-activation period (1-5 years). To better understand these long-term findings, the response patterns for the 11 participants who were evaluated at the 1- and 5-year visits were reviewed. This subgroup demonstrated a significant improvement in RMS error (P = .020) and variable error (P = .031), indicating more consistent responses at the 5-year visit.

Conclusion: Adult CI + NH listeners experience significant improvements in sound source localization within the initial weeks of listening experience, with additional improvements observed after long-term device use. The present sample demonstrated significant improvements between the 1-year and 5-year visits, with greater accuracy and consistency noted in their response patterns.

Level of evidence: 3 Laryngoscope, 132:2453-2458, 2022.