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).
Thus, depression appears to be associated with pathophysiological and structural brain abnormalities such as dysregulation of hypothalamo-pituitary-adrenal and hypothalamo-pituitary-thyroid axes, reduced hippocampal volumes and prefrontal cortex activity (Palazidou E. The neurobiology of depression. Br. Med. Bull 101(1), 127-145 (2012). There is also evidence that the hypothalamicpituitary-adrenal axis is modified by application of HF-rTMS (10 Hz) to the left DLPFC. From another point of view, a great deal of scientific evidence supports the role of alterations in brain-derived neurotrophic factor (BDNF)-mediated neuroplasticity, as well as the participation of proinflammatory cytokines as adjuvants in the pathogenesis of this complex disorder . The application of HF-rTMS (20 Hz) produces changes in the expression of BDNF and cholecystokinin in rat brain, data that are consistent with those found after administration of antidepressant drugs (mianserin, desimipramin or sertraline) and ECT, pointing to this route as being one of the bases for the therapeutic effect of TMS in mood disorders such as depression.
Depression treatment without systemic side effects of medications:
Thus, stimulating at the focal point and modulating its activity will consequently modulate the activity in other areas of the brain, and thereby TMS is focally and selectively modulating the brain activity in an entire network (Chen et al., 2013; Liston et al., 2014). 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.
What does TMS feel like?
The magnetic coil which delivers the TMS is positioned on the left front side of the head, over the part of the brain called the Left Dorso-Lateral Prefrontal Cortex. You will hear a clicking sound and feel a tapping sensation on your head when the magnetic pulses are delivered. Many patients are able to watch television or read during treatment. TMS therapy is administered at our center by highly trained staff and each rTMS session lasts 19 minutes, and are typically given five days a week for six to eight weeks. Side effects are minimal and usually only involve discomfort at the site of treatment. Patients are able to work, go to school, or continue any of their daily activities.
(Please see more detailed information about TMS for depression in TMS education to review the TMS brochures, Video and journal publications etc.)
