Left temporal low-frequency rTMS for the treatment of tinnitus: clinical predictors of treatment outcome - a retrospective study

Background: There is increasing evidence that repetitive transcranial magnetic stimulation (rTMS) can reduce chronic tinnitus. However, treatment results are characterized by high interindividual variability. Therefore, the identification of predictors for treatment response is of high clinical relevance. Methods: Clinical data of 194 patients with tinnitus were evaluated. All patients were treated with a standardized rTMS procedure (1 Hz, 10 days, 2000 stimuli/day, over the left temporal cortex). A potential influence on the outcome was analysed for the following parameters: age, gender, depression scores in Beck Depression Inventory (BDI) and tinnitus severity (TQ) before rTMS, lateralization, frequency and duration of tinnitus and extent of hearing loss. Results: An effect of tinnitus laterality was observed. In patients with left-sided or bilateral tinnitus, rTMS resulted in a statistically significant reduction of TQ scores, whereas patients with right-sided tinnitus did not show a significant improvement after rTMS treatment. However, in correlation analyses, we found a trend which did not reach statistical significance that in the subgroup of treatment responders tinnitus duration influenced rTMS outcome. In addition, a multiple regression analysis identified the TQ score at baseline as a significant predictor for treatment outcome. For all other investigated parameters, no statistically significant effects were found. Conclusions: This study suggests that left temporal low-frequency rTMS has beneficial effects in left-sided and bilateral tinnitus, but not in right-sided tinnitus. In line with the results from earlier studies involving smaller samples, tinnitus duration was found to influence rTMS outcome.