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

## TL;DR

This study examines factors that might affect how tinnitus worsens over time after cochlear implant surgery, finding that most factors do not significantly influence tinnitus aggravation.

## Contribution

The study is novel in prospectively analyzing multiple distributive, morphological, and audiological factors to determine their influence on tinnitus aggravation after cochlear implantation.

## Key findings

- Tinnitus burden significantly decreased over time following cochlear implant surgery.
- No examined factors were associated with increased risk of tinnitus exacerbation after implantation.
- Approximately 38% of patients reported increased tinnitus intensity shortly after surgery, with this proportion remaining stable over two years.

## Abstract

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 post-operative residual hearing, duration of deafness, etiology of hearing impairment, cochlear anatomy, as well as the insertion depth and angle of the CI electrode array.

A total of 65 patients were assessed pre-operatively 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, 1,000, 2,000, and 4,000 Hz) in pure-tone audiometry (PTA-4). Cochlear dimensions (distances and height), insertion depth, and insertion angle were measured using post-operative digital volume tomography. Tinnitus burden and intensity were assessed with the Visual Analog Scale (VAS) and the Tinnitus Questionnaire.

Overall, tinnitus burden significantly decreased during the course of CI treatment. However, 38% of patients reported increased tinnitus intensity on the second post-operative day, with this proportion remaining relatively stable (36%) after 2 years. Meanwhile, 33% of patients experienced an increase of tinnitus burden shortly after implantation, decreasing to 21% 1 year post-operatively. 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 pre-operative tinnitus burden or post-operative tinnitus exacerbation.

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.