The Clinical TMS Society Consensus Review and Treatment Recommendations for TMS Therapy for Major Depressive Disorder

TMS therapy uses a computerized, electromechanical medical device to produce and deliver non-invasive, magnetic stimulation using brief duration, rapidly alternating, or pulsed, magnetic fields to induce electrical currents directed at spatially discrete regions of the cerebral cortex. This method of cortical stimulation by application of brief magnetic pulses to the head is known as transcranial magnetic stimulation or TMS. When pulses of TMS are delivered repetitively, this is called repetitive TMS, or rTMS. These pulses can be delivered at either high (10–20 Hz) or low frequency (less than or equal to 1 Hz). Most clinical TMS treatments delivered for treating depression are typically given at 10 Hz to 18 Hz. The peak magnetic field strength achieved with each pulse is approximately 1.5 Tesla, right underneath the coil, similar in strength to the magnetic field produced by a typical magnetic resonance imaging (MRI) device. The MRI field is large (filling much of the room) and is constantly on. TMS magnetic fields are focal and brief. In 2008, the United States Food and Drug Administration (FDA) cleared the first TMS device for therapeutic clinical use in Major Depressive Disorder (MDD). This device was a focal iron core coil produced by Neuronetics Inc. (Malvern, PA, USA). In 2013, the FDA cleared a second device (i.e. the H-Coil) produced by Brainsway (Jerusalem, Israel). In 2015, two additional devices were FDA cleared, the Magstim Company’s (Wales, UK) figure eight coil and Tonica’s (Magventure) figure eight coil. Product manufacturer manuals provide technical details about each coil and system, which are beyond the scope of this review.