B. Langguth, G. Hajak, T. Kleinjung, A. Cacace & A.R. Møller (Eds.) Progress in Brain Research, Vol. 166 ISSN 0079-6123 Copyright r 2007 Elsevier B.V. All rights reserved CHAPTER 34 Transcranial magnetic stimulation (TMS) for treatment of chronic tinnitus: clinical effects T. Kleinjung 1, , T. Steffens 1 , A. Londero 3 and B. Langguth 2 1 Department of Otorhinolaryngology, University of Regensburg, Regensburg, Germany 2 Department of Psychiatry and Psychotherapy, University of Regensburg, Regensburg, Germany 3 Service ORL et chirurgie cervicofaciale, hoˆpital europe´en Georges-Pompidou, Paris, France Abstract: Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive method used to induce electrical current in the brain through impulses of strong magnetic fields applied externally. The technique can relieve tinnitus by modulating the excitability of neurons in the auditory cortex to decrease the hyper- excitability that is associated with generating the neural activity that causes some form of tinnitus. This chapter will review clinical studies using rTMS for the treatment of tinnitus. Keywords: tinnitus; transcranial magnetic stimulation; neuroplasticity; functional imaging; neuronavigation; auditory cortex Transcranial magnetic stimulation In 1985 Barker and colleagues showed that it was possible to depolarize neurons in the brain using external magnetic stimulation (Barker et al., 1985). Transcranial magnetic stimulation (TMS) involves applying strong impulses of magnetic fields with a duration of 100–300 ms and a strength of 1.5–2.0 T. Taking advantage of the fact that magnetic fields pass largely undistorted through the scalp and skull, repetitive TMS (rTMS) induces an electric current in the brain that can cause neuronal depolarization in the cortex of humans (Bohning et al., 2000). TMS is much less painful than the transcranial electrical stimulation (TES). For TMS, a brief (100–300 ms) impulse of a strong electrical current in the wires of a coil generates impulses of magnetic field. The lines of magnetic flux are oriented perpendicularly to the plane of the coil (Fig. 1). The electric current that is induced perpendicularly to the magnetic field can depolarize cells in the underlying brain area. Magnetic coils of different shapes are in use. Round coils are relatively powerful. The eight- shaped coils generate more focal stimulation with a maximal current at the intersection of the two round parts (Hallett, 2000). Due to the rapid de- cline of the magnetic field with increasing distance from the coil, effective stimulation is limited to superficial cortical areas. When used for the sup- pression of tinnitus, a single magnetic impulse does not produce long-lasting effects. Application of multiple impulses, known as rTMS, can have effects that outlast the stimulation. Depending on stimulation parameters, rTMS can cause excita- tion or inhibition. Low frequency (r1 Hz) rTMS has been repeatedly shown to decrease cortical excitability (Chen et al., 1997; Hoffman and Corresponding author. Tel.: +49 9419449505; Fax: +49 941 944 9512; E-mail: tobias.kleinjung@klinik.uni-regensburg.de DOI: 10.1016/S0079-6123(07)66034-8 359