Long-Term Auditory, Tinnitus, and Psychological Outcomes After Cochlear Implantation in Single-Sided Deafness: A Two-Year Prospective Study

Background/Objectives: Single-sided deafness (SSD) impairs speech perception, reduces spatial hearing, decreases quality of life, and is frequently accompanied by tinnitus. Cochlear implantation (CI) has become an established treatment option, but long-term prospective evidence across multiple functional and psychological domains remains limited. This study investigated auditory performance, subjective hearing outcomes, tinnitus burden, and psychological well-being over a two-year follow-up in a large SSD cohort. Methods: Seventy adults with SSD underwent unilateral CI. Assessments were conducted preoperatively and at 6 months, 1 year, and 2 years postoperatively. Outcome measures included the Freiburg Monosyllable Test (FS), Oldenburg Inventory (OI), Nijmegen Cochlear Implant Questionnaire (NCIQ), Tinnitus Questionnaire (TQ), Perceived Stress Questionnaire (PSQ), Generalized Anxiety Disorder scale (GAD-7), and General Depression Scale (ADS-L). Longitudinal changes were analyzed using Wilcoxon signed-rank tests with effect sizes; Holm-adjusted p-values were applied for baseline-to-follow-up comparisons. Results: Speech perception improved markedly within the first 6 months and remained stable through 2 years, with large effect sizes. All OI subdomains demonstrated early and sustained improvements in subjective hearing ability. Several hearing-related quality-of-life domains assessed by the NCIQ, particularly social interaction, self-esteem, and activity participation, showed medium-to-large long-term improvements. Tinnitus severity decreased substantially, with marked reductions observed by 6 months and maintained thereafter; the proportion of tinnitus-free patients increased at follow-up, although tinnitus symptoms persisted in a substantial subset of participants. Perceived stress was reduced initially at the early follow-up and remained below baseline thereafter. Anxiety and depressive symptoms mostly stayed within nonclinical ranges, showing no lasting changes after adjusting for multiple comparisons. Conclusions: In this prospective cohort, cochlear implantation was associated with durable improvements in auditory outcomes, tinnitus burden, and selected patient-reported quality-of-life domains over two years. Although significant functional and patient-centered improvements were noted, persistent tinnitus and diverse psychosocial outcomes underscore the need for personalized counseling and comprehensive follow-up that incorporate patient-reported outcomes and psychological assessments.