[Transcranial magnetic stimulation in depression]

Among the new therapeutic techniques in psychiatry, transcranial magnetic stimulation (TMS) seems to bring a profit in the treatment of depressions. It uses the principle of inductance to generate a magnetic current, which in turn activates cortical neurons. Stimulation is highly focused and interests specific regions of the cerebral cortex. This therapeutic technique is generally well tolerated. Side effects are rare, the most hampering one is epileptic seizures. It is favored by high frequencies (above 5 Hz) and arises mainly with patients having a history of personal or family epileptic seizures. The first open trials, quickly confirmed by controlled studies showed the efficiency of TMS in depression. With depression, double blind randomized trials, using high frequencies, stimulation of the left dorsolateral prefrontal cortex give positive results with significant decrease of scores on depressive scales applied to resistant and non resistant depressions. Some studies have stimulated the right dorsolateral prefrontal cortex using low frequencies. The decrease of scores is also significant on depressive scales. The modulating effect of rTMS on cortical excitability of the brain justifies this distinction between high and low frequencies, high frequencies having a facilitating effect whereas low frequencies have an inhibitory effect.