Transcranial magnetic stimulation (TMS) is a noninvasive method of brain stimulation in which magnetic fields are used to induce electric currents in the cerebral cortex, thereby depolarizing neurons. TMS based on focal electromagnetic induction, was introduced in 1985 by Anthony Barker (1). Both repetitive TMS (rTMS) and electroconvulsive therapy (ECT) use electrical energy to induce neuropsychiatric change; however, the magnetic fields in TMS are unaffected by the high impedance of the skull and thus, TMS can be applied relatively with no pain to conscious patients without the need for sedation.
TMS/rTMS is found to be a promising noninvasive treatment for various neuropsychiatric conditions. Therapeutic utility of TMS has been reported in the literature for psychiatric disorders, such as depression, acute mania, bipolar disorders, panic, hallucinations, obsessions/compulsions, schizophrenia, catatonia, post-traumatic stress disorder, or drug craving. Single-pulse TMS was first used as a possible therapeutic tool for depression in 1993. Since then, depression continues to be the most commonly studied psychiatric condition in the application of rTMS (2).
Most studies have suggested that the active rTMS treatment has greater antidepressant efficacy than sham stimulation (3). A number of clinics have been set up offering TMS for treatment of various diseases worldwide and rTMS is already approved by some countries for treatment of depression (i.e., Canada and Israel). In 2008, rTMS was approved by the Food and Drug Administration in the United States for the treatment of patients with medication-refractory unipolar depression who have failed one good (but not more than one) pharmacological trial.
References:
1. Barker AT, Jalinous R, Freeston IL. Non-invasive magnetic stimulation of human motor cortex. Lancet1985;1(8437):1106-7.
2. Nivoli AM, Colom F, Murru A, Pacchiarotti I, Castro-Loli P, González-Pinto A, et al. New treatment guidelines for acute bipolar depression: A systematic review. J Affect Disord 2011; 129(1-3):14-26.
3. Fitzgerald PB, Hoy K, McQueen S, Maller JJ, Herring S, Segrave R, et al. A Randomized Trial of rTMS Targeted with MRI Based Neuro-Navigation in Treatment-Resistant Depression. Neuropsychopharmacology 2009; 34(5):1255-62.