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

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.