Burst transcranial magnetic stimulation: which tinnitus characteristics influence the amount of transient tinnitus suppression?

BACKGROUND Transcranial Magnetic Stimulation (TMS) is a method capable of temporarily suppressing tinnitus by delivering tonic or burst stimuli. Burst TMS has a high interindividual variability and low effect size. Tinnitus type and laterality, tinnitus-related distress, and tinnitus duration might contribute to this large individual variation. METHODS The effect of burst TMS on the auditory cortex in 100 male individuals is evaluated with coil placed over the auditory cortex. For unilateral tinnitus, this coil was placed contralaterally to the tinnitus, whilst for bilateral tinnitus the coil was placed over the right auditory cortex. The site of maximal tinnitus suppression is determined using 1-Hz stimulation with five pulses per burst (intensity of the stimulation set at 90% of the motor threshold). When tinnitus suppression is noted, the patients are asked to estimate the decrease in tinnitus in percentage using the numeric rating scale. The procedure is repeated with stimulations at 5, 10 and 20 Hz, each stimulation session consisting of 200 pulses. RESULTS Results demonstrate that burst stimulation can decrease the perceived tinnitus intensity transiently in 57.83% of the patients. Patients with bilateral tinnitus respond better to burst TMS than patients with unilateral tinnitus and highly distressed patients presenting with unilateral pure tone tinnitus fail to bust TMS. CONCLUSIONS Burst TMS modulates both unilateral and bilateral tinnitus, both high and low distress and both pure tones and narrow band tinnitus. However, the suppression effect is moderated by tinnitus type and laterality, tinnitus-related distress, and tinnitus duration.