Influence of tonic and burst transcranial magnetic stimulation characteristics on acute inhibition of subjective tinnitus.

Objective: Transcranial magnetic stimulation (TMS) is already broadly used in different areas of neuroscience research. In the last years, special attention was drawn to TMS in tinnitus. The aim of our study is to investigate the stimulation characteristics of TMS in tinnitus patients, in particular the effect of tonic and burst stimulation of the superior temporal lobe.

Study Design: Prospective sham-controlled study.

Setting: Tertiary referral center.

Patients: Fifty tinnitus patients were included in the study. Thirty-one patients had pure-tone tinnitus, and 19 patients had noise-like tinnitus.

Study Design: Transcranial magnetic stimulation was performed in 1 session of 200 pulses at different frequencies. Stimuli were delivered to the auditory cortex region contralateral to the tinnitus side. Tonic and burst stimulations were delivered at different frequencies. Patients were asked to rate the acute tinnitus reduction after TMS on a visual analog scale.

Main Outcome Measure: Acutely perceived tinnitus reduction immediately after TMS, scored by the patient on a visual analogue scale ranging from 0 to 100%.

Results: Tinnitus reduction increased when stimulation intensity was higher relative to the patient's motor threshold. Nevertheless, this stimulation intensity was shown only to account for 10% of this increased tinnitus reduction, meaning that up to 90% of this effect should be ascribed to other factors than stimulation intensity alone. Different reactions on TMS were found in bilateral tinnitus patients compared with unilateral tinnitus patients.

Conclusion: Several parameters determine the amount of tinnitus reduction after TMS. An increased stimulation intensity relative to the patient's motor threshold only accounts for 10% of this effect. Our data also suggest different pathophysiologic mechanisms for unilateral and bilateral tinnitus.