Using repetitive transcranial magnetic stimulation for the treatment of tinnitus

Abstract

Transcranial magnetic stimulation (TMS) has recently emerged as a potential treatment option for tinnitus.1–6 TMS induces electrical stimulation of cortical neurons by creating a brief, focused magnetic field over the surface of the brain.7 When magnetic pulses are delivered repetitively and rhythmically, the process is called repetitive TMS (rTMS). The magnetic field induced by rTMS is brief (microseconds), relatively weak (except directly under the coil, where 1–3 cm of tissue is stimulated, depending on coil configuration),8 and declines rapidly with distance from the coil (falling off sharply after 2 cm).7,9 Pulse trains can be delivered at low (≤1 Hz) or high (>1 Hz) frequencies, which tend to decrease or increase neural activity beneath the coil, respectively. Standard TMS coils are only able to directly stimulate the superficial cortex, but deeper brain structures and structures in the opposite cerebral hemisphere may be affected by TMS via connecting neural pathways.10,11 Most studies using rTMS for the treatment of tinnitus have used low-frequency magnetic pulses applied to one temporal lobe for 30 minutes, once daily, for 3–10 consecutive days. Some have used functional imaging with neuronavigation to select the treatment site based on asymmetrical cortical activation, while others have targeted the left superior temporal lobe in all cases or the side opposite the loudest tinnitus. Regardless of targeting technique, beneficial results are obtained in about 50% of patients who receive active treatment. While treatment effects have been reported to persist for 6 months in some cases,2 most treatment studies have demonstrated tinnitus suppression effects lasting only a few days to a few weeks.3,5,6 This article will briefly review rTMS, the rationale for its use to treat tinnitus, and data relevant to its efficacy in treating tinnitus.