Transcranial magnetic stimulation: a new diagnostic and therapeutic tool for tinnitus patients

Even if the pathophysiology of tinnitus remains incompletely understood, there is growing agreement that dysfunctional neuroplastic processes in the brain are involved. Repetitive transcranial magnetic stimulation (rTMS) is a potent tool for modifying neural activity at the stimulated area and at a distance along functional anatomical connections. Depending on stimulation parameters, cortical networks can be functionally disturbed or modulated in their activity. The technique can alleviate tinnitus by modulating the excitability of neurons in the auditory cortex. It is assumed that TMS decreases the hyperexcitability that is associated with some forms of tinnitus. A growing number of studies demonstrate reduction of tinnitus after repeated sessions of low-frequency rTMS and indicate that rTMS might represent a new promising approach for the treatment of tinnitus. Single sessions of high-frequency rTMS over the temporal cortex have been successful in reducing the intensity of tinnitus during the time of stimulation and could be predictive for treatment outcome of chronic epidural stimulation using implanted electrodes. Because most available studies have been performed with small sample sizes and show only moderate effect sizes and high interindividual variability of treatment effects, further development of the technique is needed before it can be recommended for use in clinical routine. Both patient-related (e.g., hearing loss, tinnitus duration, age) and stimulation-related (e.g., stimulation site, stimulation protocols) factors seem to influence treatment outcome; however, their exact impact still remains to be clarified.