Incomplete binaural restoration in single-sided deafness treated with cochlear implants: insights from compensatory head-orienting behaviors

Abstract

Introduction Single-sided deafness (SSD) disrupts binaural spatial hearing and may require active compensatory strategies, even for those with cochlear implants (CIs). This study examined spatial hearing adaptations in individuals with single-sided deafness (SSD), including those using cochlear implants (CIs) and unaided SSD, compared to normal-hearing (NH) controls. Methods Using a dual-task paradigm, participants performed both simple localization and complex multi-talker speech identification tasks, with continuous tracking of head-orientation dynamics to quantify re-orientations, response promptness, and cumulative movement. Results The use of CIs yielded measurable improvements in basic localization tasks; however, these benefits diminished in ecologically valid, dynamic environments. Speech intelligibility remained asymmetric, favoring the better-hearing ear, and performance for CI-side targets collapsed despite favorable signal-to-noise ratios. Listeners with SSD-CI demonstrated rapid, iterative scanning, prolonged orientation sequences, and increased cumulative head movement, suggesting reliance on active compensatory strategies rather than complete restoration of spatial hearing. Discussion Current CI technology improves access to sound and spatial hearing for SSD listeners, but it does not fully restore functional binaural hearing in dynamic listening environments. Persistent compensatory head-orienting behaviors indicate reliance on better-ear listening and increased physical effort to position the head in ways that exploit acoustic head-shadow effects, allowing speech access by the better-hearing ear. These findings support the use of ecologically valid assessment models and head-orientation metrics to guide auditory rehabilitation and future innovations for asymmetric hearing loss.