Restoring Sound Localization in Single-Sided Deafness Through Cochlear Implantation: A Meta-Analysis

Single-sided deafness impairs sound localization, reducing quality of life and spatial awareness. Cochlear implantation has emerged as a promising intervention, yet the magnitude of benefit and influence of rehabilitation factors remain unclear. This systematic review and meta-analysis examined localization outcomes after cochlear implantation in single-sided deafness.

Multiple databases were searched from their earliest available records to February 2025 for studies reporting quantitative localization outcomes in cochlear implant recipients with single-sided deafness. The primary outcome was a reduction in root mean square (RMS) localization error. A random-effects meta-analysis was performed, with subgroup analyses by age, etiology, and rehabilitation factors.

Forty studies (667 participants) met the inclusion criteria. Cochlear implantation significantly improved localization, with a pooled RMS error reduction of 20.8 degrees (95% CI: 17.9-23.7 degrees, P <0.001; I2 =94.2%). Younger patients achieved greater gains (42.4 degrees for ≤50 y vs. 15.8 degrees for >55 y, P =0.032), as did those with sudden sensorineural hearing loss compared with Ménière's disease (23.5 vs. 11.3 degrees, P =0.018). Structured rehabilitation was associated with larger improvements than standard care (26.1±8.2 degrees vs. 18.4±7.6 degrees, Cohen's d =0.977; P <0.01). Earlier activation (≤21 d) and high daily use (≥10 h) were associated with the most favorable outcomes.

Cochlear implantation provides clinically meaningful localization improvements in single-sided deafness, though performance remains below normal hearing levels. Outcomes are optimized by structured rehabilitation, earlier activation, and consistent device use. These findings support cochlear implantation as an effective intervention and inform evidence-based rehabilitation strategies.