rTMS for the treatment of auditory phantom perceptions

The pathophysiological mechanisms of idiopathic tinnitus remain unclear. Recent studies demonstrated focal brain activation in the auditory cortex of patients suffering from chronic tinnitus. Low frequency repetitive transcranial magnetic stimulation (rTMS) is able to reduce cortical hyperexcitability. Patients suffering from severe chronic tinnitus underwent a [¹⁸F]deoxyglucose- PET (positron emission tomography) and MRI (magnetic resonance imaging) measurement. Fusioning of the individual PET scan with the structural MRI-scan (T1, MPRAGE) allowed to exactly identify the area of increased metabolic activity in the auditory cortex, which was selected as the target point for rTMS. In this context, a neuronavigational system adapted for TMS positioning enabled to monitore the exact position of the figure 8-shaped magnetic coil in relation to the target area. rTMS (110% motor threshold; 1 Hz; 2000 stimuli/ day over 10 days) was performed using a placebo controlled design. Patients were blind regarding the stimulus condition. For the sham stimulation a specific sham-coil system was used. Treatment outcome was assessed with a specific tinnitus questionnaire (Goebel and Hiller). Up to date, 30 patients were included. In most of the patients we could localize an increased metabolic activation within the primary auditory cortex. After 10 days of verum rTMS a remarkable improvement of the tinnitus score was found. This effect could not be seen after sham stimulation.