Evaluating the Impact of Non-implanted Ear Hearing in Single-sided Cochlear Implant Patients

Introduction: Outcomes of unilateral cochlear implantation (CI) vary widely, yet the influence of hearing in the non-implanted ear remains unclear. This study investigated the impact of preoperative hearing thresholds in the non-implanted ear on speech perception improvement in the implanted ear.

Methods: A retrospective review was conducted of 219 adult and pediatric CI recipients at a single tertiary academic center from 2012 - 2025. Preoperative hearing in the non-implanted ear was quantified using pure-tone average (PTA), analyzed continuously, and categorized as mild (≤40 dB), moderate (41–70 dB), or severe (≥71 dB). Speech perception improvement in the implanted ear was assessed using the AzBio sentence test, defined as the difference between the last preoperative and most recent postoperative score. Associations were evaluated using correlation and Kruskal–Wallis testing.

Results: 87 patients met inclusion criteria. No significant correlation was observed between continuous preoperative PTA in the non-implanted ear and postoperative AzBio improvement (Pearson r = 0.20, p = 0.065; Spearman (ρ = 0.20, p = 0.058). In contrast, AzBio improvement differed significantly across non-implanted ear hearing categories on Kruskal–Wallis testing (p = 0.046), as patients with moderate hearing loss in the non-implanted ear demonstrated less improvement than those with severe hearing loss.

Conclusions: Moderate hearing loss in the non-implanted ear was associated with less postoperative speech perception improvement compared with severe loss, though continuous hearing thresholds showed no association. While these findings suggest that non-implanted ear hearing status may influence CI benefit, large multicenter studies are needed to clarify the role of non-implanted ear hearing in post-implant speech perception outcomes.