rTMS (repetitive transcranial magnetic stimulation) has been shown to produce changes in neuronal activity in regions of the brain implicated in mood regulation, such as the prefrontal cortex. As each magnetic pulse passes through the skull and into the brain, this induces brief activity of brain cells underlying the treatment coil.

The frequency of pulse delivery also influences whether brain activity is increased or decreased by a session of rTMS. Recent studies also suggest that stimulation over the left and right sides of the brain can have opposite effects on mood regulation.

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Antidepressant medications and psychotherapy are the first line treatments for major depression. These treatments, however, do not work for all patients. In these instances, rTMS might be used as an alternative treatment, or to augment antidepressant medications or psychotherapy. Patients who have failed to achieve an adequate response from antidepressants, or who are unable to tolerate medications, might consider rTMS therapy.

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Because rTMS uses magnetic pulses, before beginning a treatment, patients are asked to remove any magnetic-sensitive objects (such as jewelry, credit cards). Patients are required to wear earplugs during treatment for their comfort and hearing protection, as rTMS produces a loud clicking sound with each pulse, much like an MRI machine. Patients are seated during each session of rTMS.

During the first rTMS session, several measurements are made to ensure that the TMS coil will be properly positioned over the patient’s head. Once this is done, the TMS coil is suspended over the patient’s scalp. The TMS physician then measures the patient’s motor threshold, by administering several brief pulses. The motor threshold is the minimum amount of power necessary to make the patient’s thumb twitch, and varies from individual to individual. Measuring the motor threshold helps the physician personalize the treatment settings and determine the amount of energy required to stimulate brain cells.

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