Investigation of distributive, morphological and audiological factors influencing the long-term aggravation of tinnitus following cochlear implant provision

Friederike EveradAntje AschendorffAnn-Kathrin RauchLeonie FriesSusan ArndtManuel Christoph Ketterer^*

• University of Freiburg, Freiburg, Germany

Objectives: This prospective study aims to identify factors that may influence the long-term aggravation of tinnitus following cochlear implant (CI) surgery. The variables examined include age, gender, pre- and postoperative residual hearing, duration of deafness, etiology of hearing impairment, cochlear anatomy, as well as the insertion depth and angle of the CI electrode array. Methods: A total of 65 patients were assessed preoperatively and at 2 days, 4 weeks, 12 months, and 24 months after CI surgery. Age, gender, duration of deafness, and etiology were recorded through anamnesis. Residual hearing before and after implantation was evaluated using the air conduction (AC) thresholds in four frequencies (500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz) in pure-tone audiometry (PTA-4). Cochlear dimensions (distances and height), insertion depth, and insertion angle were measured using postoperative digital volume tomography (DVT). Tinnitus burden and intensity were assessed with the Visual Analog Scale (VAS) and the Tinnitus Questionnaire. Results: Overall, tinnitus burden significantly decreased during the course of CI treatment. However, 38% of patients reported increased tinnitus intensity on the second postoperative day, with this proportion remaining relatively stable (36%) after two years. Meanwhile, 33% of patients experienced an increase of tinnitus burden shortly after implantation, decreasing to 21% one year postoperatively. None of the examined factors—including age, gender, residual hearing, duration of deafness, etiology, cochlear anatomy, insertion depth, or insertion angle—were associated with an increased risk of preoperative tinnitus burden or postoperative tinnitus exacerbation. Conclusion: Distributive and morphological factors did not significantly influence tinnitus exacerbation before or after CI. Nevertheless, tinnitus symptoms improved significantly over time. Future studies should investigate additional potential contributing factors, such as psychological comorbidities, in the development or persistence of tinnitus following CI.