Psychiatric Applications of Repetitive Transcranial Magnetic Stimulation

Abstract

Transcranial magnetic stimulation (TMS) is an increasingly popular noninvasive brain stimulation modality. In TMS, a pulsed magnetic field is used to noninvasively stimulate a targeted brain region. Repeated stimulation produces lasting changes in brain activity via mechanisms of synaptic plasticity similar to long-term potentiation. Local application of TMS alters activity in distant, functionally connected brain regions, indicating that TMS modulates activity of cortical networks. TMS has been approved by the U.S. Food and Drug Administration for the treatment of major depressive disorder, obsessive-compulsive disorder, and smoking cessation, and a growing evidence base supports its efficacy in the treatment of other neuropsychiatric conditions. TMS is rapidly becoming part of the standard of care for treatment-resistant depression, where it yields response rates of 40%-60%. TMS is generally safe and well tolerated; its most serious risk is seizure, which occurs very rarely. This review aims to familiarize practicing psychiatrists with basic principles of TMS, including target localization, commonly used treatment protocols and their outcomes, and safety and tolerability. Practical considerations, including evaluation and monitoring of patients undergoing TMS, device selection, treatment setting, and insurance reimbursement, are also reviewed.

Keywords: Repetitive transcranial magnetic stimulation; Transcranial magnetic stimulation; major depressive disorder; obsessive-compulsive disorder; smoking cessation.

FIGURE 1.

Common stimulation patterns of transcranial magnetic stimulation^{a a} Each vertical line represents one magnetic pulse. A: 10-Hz stimulation, which is excitatory, typically provides stimulation in 4-second trains (a frequency of 10 Hz indicates that 10 pulses are administered per second, meaning a 4-second train delivers a total of 40 pulses). This is followed by a 26-second intertrain interval (or wait time). This pattern repeats 75 times (75 trains), delivering a total of 3,000 pulses in a session lasting 37.5 minutes. B: 1-Hz stimulation, which is inhibitory, involves administering one pulse per second in a continuous train, often for a total of 500 to 1,200 pulses (requiring a session of only 8 to 20 minutes, respectively). C: Theta burst stimulation applies transcranial magnetic stimulation (TMS) pulses in a pattern mimicking the endogenous firing activity of hippocampal neurons. “Bursts” consist of three TMS pulses applied in extremely short succession (at a frequency of 50 Hz). These “bursts” are then administered at a frequency of 5 Hz (five bursts per second). Intermittent theta burst stimulation (iTBS) is excitatory and is generally administered as 10 bursts (30 pulses) during a 2-second train, followed by an 8-second waiting period. This pattern is often repeated 20 times (20 trains), delivering a total of 600 pulses in a session lasting just 3 minutes. D: Continuous theta burst stimulation (cTBS) is inhibitory and is generally administered in a single, uninterrupted train of bursts administered at a frequency of 5 Hz, often for a total of 600 to 1,800 pulses (requiring a session of only 40 seconds to 2 minutes, respectively). ITI, intertrain interval.