What is transcranial magnetic stimulation?

Transcranial magnetic stimulation - also known as TMS -  is a neuromodulation technique that is used for the purpose of modulating brain activity. TMS induces changes in activity of nerve cells by applying rapidly changing or repetitive magnetic fields. Thus, TMS is also called repetitive TMS (rTMS).

Transcranial magnetic stimulation is a clinically meaningful and effective treatment of depression (major depressive disorder) (Lefaucheur et al., 2014; McClintock et al., 2017). The treatment is non-invasive, and does not require anesthesia. TMS is a drug-free alternative to antidepressant medication, and is offered to patients either not responding to their medication or who cannot tolerate the side effects. 

The largest clinical trial using rTMS for treatment of depression shows that 49% patients, who have failed to receive improvement from prior antidepressant medication responded to treatment, and 32 % received remission, meaning they were no longer clinically depressed [Blumberger et al., 2018). TMS has been marketed and approved for this purpose for almost a decade in both Europe and the USA (McClintock et al., 2017).

Why is TMS effective in treatment of MDD?

The most common symptoms of depression is the presence of empty, sad or irritable mood in combination with both cognitive and somatic changes that can significantly affect the individual’s capacity to function (Downar, Blumberger, Daskalakis, 2016). These behavioral and functional consequences of depression are due to alterations in brain activity. In depression, a whole distributed network of brain areas is affected. The cardinal idea of applying TMS for treatment of depression is to precisely target the areas of the brain involved in MDD. The part of the brain that is being stimulated is located to the left side of the brain, specifically the dorso-lateral prefrontal cortex, or in short Left-DLPFC. This cortical area is the prime target for CE and FDA approved TMS treatment, as it is a focal point connecting all the different brain areas that are involved in the pathology of depression (Anderson, Hoy, Daskalakis, & Fitzgerald, 2016; Tik et al., 2017).

Depression treatment without systemic side effects 

Thus, stimulating at the focal point and modulating its activity will consequently modulate the activity in other areas of the brain, and thereby transcranial magnetic stimulation  is focally and selectively modulating the brain activity in an entire network (Chen et al., 2013; Liston et al., 2014). Or in other words, by performing focal point TMS we can modulate entire brain networks, and thereby TMS can result in alleviation of the depression as well as the behavioral and cognitive symptoms of the disorder, without any systemic side effects such as those often associated with pharmacological treatment.

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