Tinnitus outcomes after cochlear implantation in single-sided deafness: an exploratory prospective multicenter study

Tinnitus is thought to be suppressed through partial reversal of auditory deafferentation via cochlear implantation (CI). By stimulating the deafferented auditory pathway, multiple studies have revealed that tinnitus is significantly suppressed in 66-92% of patients undergoing CI. This study aimed to evaluate the efficacy of CI as a treatment for tinnitus and to investigate post-CI audiologic outcomes in patients with single-sided deafness (SSD). From November 2018 to July 2020, 10 patients who were diagnosed with SSD and suffering from tinnitus were prospectively recruited at three tertiary referral hospitals. Participants in this study agreed to undergo CI as a treatment for tinnitus. Postoperative aided pure tone audiometry (PTA) and word recognition score (WRS) were measured. Questionnaires related to tinnitus, such as the tinnitus handicap inventory (THI) and visual analogue scale (VAS) scores including loudness, distress, and perception, were administered. Additionally, a tinnitogram was obtained for loudness and pitch matching. Audiological outcomes of CI were analyzed in conjunction with the results of pitch-matching from the tinnitogram. All 10 patients completed device-on evaluations, and 9 patients completed device-off evaluations. THI scores showed statistically significant improvement 3 months after CI in both the device-on and device-off conditions (preoperative: 78; device on: 38, p = 0.027; device off: 50, p = 0.049). VAS scores also demonstrated significant improvement after CI (preoperative: 8.2; device on: 3.3, p = 0.011; device off: 6.5, p = 0.012). Four patients demonstrated changes in psychoacoustic tinnitus features after CI: 2 changed to lower frequency, 1 changed to higher frequency, and 1 patient's tinnitus changed from white noise to a specific identifiable frequency. There was no significant tendency for threshold (T-level and C-level) changes in pitch-matching frequency. In line with previous literature, this exploratory multicenter study demonstrated improvement in tinnitus loudness and distress after CI in patients with single-sided deafness and tinnitus, with a tendency for greater reduction in tinnitus intensity observed when the device was activated. Additionally, approximately half of the patients showed changes in the psychoacoustic characteristics of tinnitus after CI. Given the small sample size and the absence of a non-implanted control group, these findings should be regarded as exploratory and hypothesis-generating, and warrant confirmation in adequately powered controlled trials.