Transcranial magnetic stimulation for the treatment of tinnitus: 4-year follow-up in treatment responders--a retrospective analysis

Abstract

Background
Repetitive transcranial magnetic stimulation (rTMS) over the temporal cortex has been proposed as a new approach for the treatment of tinnitus. Even if most studies have shown beneficial effects, there is only limited knowledge about clinical predictors for treatment response and about the duration of treatment effects.
Objective
In this study, we compared clinical characteristics of rTMS responders and nonresponders and assessed long-term outcome in the responder group.
Method
Results from 235 patients, who were treated with rTMS because of chronic tinnitus were analysed. Patients received either a standard protocol of low-frequency rTMS (n 5 188; 110% motor threshold, 1 Hz, 2000 stimuli/day) over the left temporal cortex or combined frontal and temporal rTMS (n 5 47; 110% motor threshold, 1000 stimuli at 20 Hz, left dorsolateral prefrontal cortex plus 1000 stimuli at 1 Hz left temporal cortex). Response criterion was defined as an improvement of at least 10 points in the
tinnitus questionnaire (TQ) score between baseline and the follow-up assessment 90 days after treatment.
Results
For the entire study group there was a highly significant effect of treatment on the TQ score. Fifty patients (21.3%) were responders according to the above mentioned definition. The response criterion was fulfilled by 19.7% of the patients receiving left temporal rTMS and by 26% of the patients receiving combined rTMS. The only significant difference between responders and nonresponders was a higher baseline score of the TQ in the responder group. There were no significant differences in all other assessed patient parameters (gender, age, tinnitus duration, tinnitus laterality, motor threshold, handedness). Ninety days after treatment the average TQ reduction in the responder group was 18.2 points as compared with baseline. At the two long-term follow-up assessments (2.12 6 1.17 years and 3.9 6 1.17 years after treatment) the improvement in the responder group was still 14.2, respective 14.4
points.
Conclusions
These data underscore the clinical relevance of rTMS in the treatment of tinnitus. A potential explanation for the observed long-lasting clinical effects is that rTMS interferes with tinnitus related neuronal activity and thus facilitates the intrinsic ability of the brain to restore normal function.