Brain Stimulation: New Vistas for the Exploration and Treatment of Tinnitus

Aims: Tinnitus, the perception of sounds or noise in the absence of auditory stimuli, is a frequent and often severely disabling symptom of different disorders of the auditory system. Attempts to develop evidence-based therapies have been thwarted by a poor understanding of the underlying pathophysiology. However, recent work points toward a pivotal role of maladaptive cortical reorganization in the generation and perpetuation of tinnitus. Changes in the representation of sounds, abnormalities of oscillatory activity, and hyperactivity in higher order areas of auditory processing have been linked with the perception of tinnitus. Brain stimulation techniques have entered the field and have opened exciting new perspectives for the modulation of dysfunctional brain activity. In this review, a comprehensive overview on the use of brain-stimulation techniques in the exploration and experimental treatment of tinnitus is provided. Discussions: Noninvasive and invasive brain stimulation techniques, for example, transcranial magnetic stimulation (TMS), direct current stimulation (tDCS), and direct electrical cortical stimulation gave rise to a new line of investigation in tinnitus research. First, it has been shown that focal interference with presumably pathological cortical function can reduce tinnitus at least transiently. Second, the reduction of tinnitus-associated enhancement of cortical activity by neuronavigated TMS has been demonstrated to ameliorate tinnitus. Third, preliminary data suggest that repeated application of TMS or continuous cortical stimulation may lead to a longer lasting suppression of tinnitus. Conclusions: These proof of principle studies point toward a new option for the investigation and neurophysiology based treatment of tinnitus. Based on these findings, larger scale randomized clinical trials are needed to explore the efficacy of different brain stimulation techniques and parameters as well as the optimal target sites and treatment schedules. Particularly, a careful evaluation of clinical relevance under consideration of an adequate sham control and attention to possible unwanted side effects of these new interventions are indispensable.