Transcranial magnetic stimulation (TMS)

Transcranial magnetic stimulation (TMS) is a medical therapy used to treat clinical depression. Though TMS is noninvasive by nature, it is typically reserved for cases of depression that have not responded to other interventions. Psychiatrists note that about two-thirds of people who take antidepressants for depression continue to suffer from one or more symptoms two months after starting treatment. Clinical evidence also shows that the likelihood of an antidepressant failing to provide adequate relief increases every time a patient changes to a different medication. TMS offers an alternative to depression sufferers whose condition has proven difficult to treat with antidepressants. The procedure was approved for use in the United States by the Food and Drug Administration (FDA) in 2008.

While TMS has proven effective, the treatment’s exact mode of action remains unclear. It targets a region of the brain involved in mood regulation, and experts believe the magnetic stimulation triggers changes in brain chemistry that lead to sustained improvements in mood that can result in complete remission of clinical depression.

Background

Clinicians generally consider a treatment known as electroconvulsive therapy (ECT) or “shock therapy” to be the most effective way to relieve persistent symptoms of clinical depression that have not responded to other interventions. Initially developed in Italy during the 1930s, ECT has been used to improve depression symptoms for decades. Modern methods have strong safety and efficacy profiles, but ECT also poses a risk of producing significant side effects that can interfere with cognitive performance and memory. It also continues to have a negative public image, largely resulting from frightening depictions in popular culture and the physical dangers it posed when researchers were first developing it.

The origins of TMS as a treatment for depression grew out of its initial use as a diagnostic technique for multiple sclerosis patients, which began in the late 1970s. Ongoing refinements to TMS technologies resulted in the introduction of the first stable and consistent TMS device in the mid-1980s. By 1991, researchers had discovered that TMS had possible applications as a treatment for nonresponsive cases of clinical depression. A flurry of research activity followed, and by the mid-1990s, investigators had pooled their knowledge and resources to develop a set of universal ethics and safety protocols to mitigate concerns regarding the treatment’s potential long-term effects. These protocols were in place by 1998, by which time TMS was showing promise as a possible alternative to ECT for depression patients.

By this time, TMS was also being promoted as a novel treatment for a wide range of mental health conditions, prompting increased review from regulatory agencies. Health officials in Australia, Brazil, Canada, and Israel, among other countries, endorsed its use as an alternative intervention for severe cases of clinical depression. As an emerging and relatively unproven option, TMS was initially considered as a last resort for patients who had tried all other available treatments without success. However, it continued to be used and generated positive results with fewer side effects than ECT. Then the technique gained increased traction in the psychiatric community. The FDA approved it for use in the United States after a major 2007 clinical trial produced positive results, and it became available in the United States in October 2008.

Overview

Most TMS treatments involve repetitive bursts of magnetic pulses. As such, clinical literature typically refers to the technique as repetitive TMS or rTMS. During a session, the patient wears an electromagnetic coil device, which is placed against the skin near the point where the scalp and forehead meet. The healthcare practitioner then delivers a concentrated pulse of magnetic energy through the coil, which penetrates the brain. Researchers have yet to identify the exact way in which this magnetic energy interacts with neurochemical processes, but current explanatory models posit that people with clinical depression typically have lower levels of activity in areas of the brain that regulate mood. TMS treatments target these areas, stimulating them to produce lasting changes that elevate mood and relieve depression symptoms. Treatment providers use a range of different magnetic pulse patterns, as some patients respond to certain patterns better than others.

Most therapeutic applications of TMS require patients to undergo treatments five days per week for four to six weeks. Individual sessions usually last for a minimum of twenty minutes and a maximum of fifty minutes, with the duration of each session and the overall treatment program being determined by the patient’s healthcare team after a detailed analysis of his or her symptoms and health history. Doctors determine the optimal strength of the magnetic pulse by gradually increasing its intensity until the patient reaches his or her motor threshold, which is marked by twitching in the fingers or hands. Mood improvements typically take several weeks to manifest and occur in about 50 to 60 percent of patients. About one-third of those who undergo TMS therapy report complete relief from their depression symptoms. Doctors sometimes recommend maintenance sessions as a support strategy for lasting improvement, which can be supplemented with psychotherapy and medications. Patients whose depression relapses can undergo reinduction rTMS treatments, which can restore the original therapeutic benefits.

TMS is generally well-tolerated but can cause some side effects. These include headaches, which can occur during or after the procedure, as well as facial muscle twitches, a feeling of lightheadedness, and mild scalp tenderness. Rarely, TMS can produce mania, which is a state of unusually elevated energy and sensory arousal. The procedure is also associated with an increased risk of seizures in epileptic patients and patients with a personal or family history of seizures. Patients with brain damage resulting from traumatic injuries, strokes, or tumors and patients with electrical, magnetic, or metal medical implants also face heightened safety risks and may not be considered good candidates for TMS therapy.

In the United States, TMS is currently approved only as a treatment for depression. However, research into other potential applications is ongoing. Doctors and scientists are studying its possible benefits as a smoking cessation option and a treatment for other mental health conditions including bipolar disorder, obsessive-compulsive disorder (OCD), and post-traumatic stress disorder (PTSD).

Bibliography

Bermudes, Richard A., et. al. Transcranial Magnetic Stimulation: Clinical Applications for Psychiatric Practice. American Psychiatric Association Publishing, 2017.

Holtzheimer, Paul E. and William McDonald. A Clinical Guide to Transcranial Magnetic Stimulation. Oxford University Press, 2014.

Horvath, Jared C., et. al. “Transcranial Magnetic Stimulation: A Historical Evaluation and Future Prognosis of Therapeutically Relevant Ethical Concerns.” Journal of Medical Ethics, Vol. 37 (2011): pp. 137–143.

Sadowsky, Jonathan. “Electroconvulsive Therapy: A History of Controversy, but Also of Help.” Scientific American, 13 Jan. 2017, www.scientificamerican.com/article/electroconvulsive-therapy-a-history-of-controversy-but-also-of-help/. Accessed 2 Apr. 2019.

Stern, Adam P. “Transcranial Magnetic Stimulation (TMS): Hope for Stubborn Depression.” Harvard Medical School, 23 Feb. 2018, www.health.harvard.edu/blog/transcranial-magnetic-stimulation-for-depression-2018022313335. Accessed 2 Apr. 2019.

“Transcranial Magnetic Stimulation.” Mayo Clinic, 27 Nov. 2018, www.mayoclinic.org/tests-procedures/transcranial-magnetic-stimulation/about/pac-20384625. Accessed 2 Apr. 2019.

“Transcranial Magnetic Stimulation (TMS) Service.” Johns Hopkins Medicine, 2019, www.hopkinsmedicine.org/psychiatry/specialty‗areas/brain‗stimulation/tms/index.html. Accessed 2 Apr. 2019.

“What Is Transcranial Magnetic Stimulation?” Neuromodec, 2019, neuromodec.com/what-is-transcranial-magnetic-stimulation-tms/. Accessed 2 Apr. 2019.