[Transcranial magnetic stimulation (TMS)--from diagnostic procedure to therapy]

Transcranial magnetic stimulation (TMS) has been a well-established diagnostic tool in neurological practice for many years. It has been shown to be a safe and well tolerated method. Lately this technique has also found its way to psychiatry for the treatment of mood disorders. Several studies which investigated TMS of deeper brain regions found antidepressive effects in analogy to electro convulsive therapy (ECT). This could present a significant advantage, because TMS provides non-invasive and painless stimulation of the cerebral cortex. The method is based on the principle that a time-varying magnetic field induces an electric field which leads to activation of inhibitory and excitatory neurons in neural tissue. The magnetic field pervades the intact scalp and skull without loss of energy. Both case reports as well as clinical studies have shown that TMS could present a promising option in the treatment of depression. A review of the literature demonstrates that further studies are needed to clarify many questions regarding technical and clinical aspects, such as dosage, duration of application, localization of the coils, as well as the impact of rapid-rate TMS and stronger magnetic field generators, before TMS will become an established tool in the treatment of psychiatric disorders.