Depression - rTMS
rTMS (repetitive Transcranial Magnetic Stimulation) uses magnetic field changes to generate an electric current near the DLPFC (dorsolateral prefrontal cortex) in the brain, thereby stimulating the DLPFC and increasing the activity level of neurons in that area. They hypothesize that the DLPFC activity level in depressed patients is lower than in others, and with appropriate stimulation, the activity level in this region can be restored to normal. As a result, the patient’s depression symptoms may be alleviated.
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Treating Depression Doesn’t Always Require Medication? The Mechanism of rTMS for Depression
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No need for medication—that sounds great? Actually, rTMS has its downsides and limitations too.
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How Does rTMS (Repetitive Transcranial Magnetic Stimulation) Actually Work? A Simulated Experience Before Treatment
Treating Depression Doesn’t Always Require Medication? The Mechanism of rTMS for Depression
The formation and treatment of depression have often been based on the Monoamine Hypothesis: the brain lacks sufficient serotonin and other neurotransmitters, and taking oral antidepressants to replenish these substances can cure depression symptoms.
However, years of research have revealed that the development of depression may depend on other factors. Scientists have found that in the brains of people with depression, the activity levels in certain areas differ from those of healthy individuals.
Take one example: in patients with depression, the ventromedial prefrontal cortex (VMPFC), located in the medial part of the frontal lobe, generally shows higher activity levels. In contrast, the dorsolateral prefrontal cortex (DLPFC)—roughly the area near the "M-shaped" forehead where hair might be receding—tends to have lower activity levels.
But when their depression symptoms improve, the activity level in the VMPFC decreases, while the DLPFC’s activity level increases. Researchers have also observed that in some stroke patients, damage to the VMPFC can lead to milder depression symptoms. Conversely, if the DLPFC is damaged, these patients tend to become more depressed.
This is the principle behind how rTMS (repetitive Transcranial Magnetic Stimulation) works. rTMS uses magnetic field changes to generate an electric current near the DLPFC in the brain, stimulating this area and increasing the activity level of its neurons. The hypothesis is that the DLPFC activity level in depressed patients is lower than in others, and with appropriate stimulation, this region’s activity can be restored to normal, thereby alleviating the patient’s depression symptoms.
References:
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FDA permits marketing of transcranial magnetic stimulation for depression treatment
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Daily left prefrontal transcranial magnetic stimulation therapy for major depressive disorder
No Need for Medication That Great? Actually, rTMS Has Downsides and Limitations Too
As one of the treatment options for depression, including treatment-resistant depression, rTMS (repetitive Transcranial Magnetic Stimulation) is certainly good news for patients. At the very least, it provides an additional choice for treatment.
Some patients are reluctant to take medication and previously only had psychotherapy as an option. Now, they have another choice: a neuromodulation approach to treat depression. While undergoing rTMS, patients can also decide whether to take medication or not. Compared to other therapies for treatment-resistant depression, such as ECT (Electroconvulsive Therapy), rTMS doesn’t require general anesthesia, and the risks and side effects for patients are relatively lower.
Side Effects and Limitations of rTMS
However, rTMS does come with its downsides and side effects. rTMS induces an electric current in the brain through magnetic field changes, but some of this current can "leak," occasionally stimulating the trigeminal nerve near the scalp, which may cause headaches in patients.
The frequent magnetic field changes from the rTMS device produce a repetitive clicking sound, which can sometimes be uncomfortable. Some patients may experience tinnitus after rTMS sessions, so healthcare professionals typically provide earplugs for patients before treatment.
Stimulating the brain with electric currents also carries a risk of seizures. However, the likelihood of rTMS causing a seizure is quite low—about 1 in 1,000. In fact, studies show that the risk of seizures from rTMS is comparable to that of standard antidepressants.
Reference:
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FDA permits marketing of transcranial magnetic stimulation for depression treatment
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Daily left prefrontal transcranial magnetic stimulation therapy for major depressive disorder
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Safety and tolerability of transcranial magnetic stimulation in patients with major depression
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Safety of rTMS to non-motor cortical areas in healthy participants and patients with depression
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The role of transcranial magnetic stimulation in the treatment of depression
How Does rTMS Actually Work? A Simulated Experience Before Treatment
rTMS (repetitive Transcranial Magnetic Stimulation) isn’t a medication; instead, it induces an electric current through magnetic field changes to stimulate the brain’s DLPFC (dorsolateral prefrontal cortex), thereby alleviating depression symptoms.
However, this process isn’t immediate. Patients need to visit the clinic for approximately 20-minute sessions, Monday through Friday, for six consecutive weeks. Typically, it takes one to two weeks before results start to become noticeable.
Patients arrive at the clinic at their scheduled time and fill out a mood-related questionnaire. Under the guidance of a clinic assistant, they enter the rTMS treatment room. The patient is first seated in a specialized chair, with their head secured, and encouraged to relax.
The doctor will place a distinctive cap on the patient’s head and measure various dimensions of the head to calculate the precise location of the DLPFC. This cap is kept for the patient and used in all subsequent treatment sessions.
During the 1st, 10th, and 20th sessions, the doctor will first measure the patient’s motor evoked potential (MEP) to determine the electrical dosage needed for treatment. The doctor will use the device to stimulate the patient’s motor cortex while observing whether the patient’s thumb moves in response to the stimulation.
For the actual treatment, the doctor positions the device over the pre-calculated DLPFC location. The patient will feel a series of pulses, with brief 10-second rests between each series. The entire process lasts 19 minutes. The doctor typically provides earplugs to minimize discomfort from the noise of the device. After the session, the patient can leave the clinic and rest at home.
Reference
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Carpenter, L.L. and Price, L.H., 2011. The role of transcranial magnetic stimulation in the treatment of depression. Psychiatric Clinics of North America, 34(1), pp.143–156. [online] Available at: https://www.sciencedirect.com/science/article/pii/S0193953X10001023 [Accessed 6 March 2025].
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George, M.S., Lisanby, S.H., Avery, D., McDonald, W.M., Durkalski, V., Pavlicova, M., Anderson, B., Nahas, Z., Bulow, P., Zarkowski, P., Holtzheimer III, P.E., Schwartz, T. and Sackeim, H.A., 2010. Daily left prefrontal transcranial magnetic stimulation therapy for major depressive disorder: A sham-controlled randomized trial. Archives of General Psychiatry, 67(5), pp.507–516. [online] Available at: https://jamanetwork.com/journals/jamapsychiatry/article-abstract/210714 [Accessed 6 March 2025].
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Herwig, U., Satrapi, P. and Schönfeldt-Lecuona, C., 2003. Using the international 10-20 EEG system for positioning of transcranial magnetic stimulation. Brain Topography, 16(2), pp.95–99. [online] Available at: https://doi.org/10.1023/B:BRAT.0000006333.93597.9d [Accessed 6 March 2025].
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Machii, K., Cohen, D., Ramos-Estebanez, C. and Pascual-Leone, A., 2006. Safety of rTMS to non-motor cortical areas in healthy participants and patients with depression. Clinical Neurophysiology, 117(2), pp.455–471. [online] Available at: https://www.sciencedirect.com/science/article/pii/S1935861X08000069 [Accessed 6 March 2025].
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Mutz, J., Vipulananthan, V., Carter, B., Hurlemann, R., Fu, C.H.Y. and Young, A.H., 2019. Comparative efficacy and acceptability of non-surgical brain stimulation for the acute treatment of major depressive episodes: An umbrella review of systematic reviews and meta-analyses. The British Journal of Psychiatry, 214(6), pp.1–10. [online] Available at: https://www.cambridge.org/core/journals/the-british-journal-of-psychiatry/article/comparative-efficacy-and-acceptability-of-nonsurgical-brain-stimulation-for-the-acute-treatment-of-major-depressive-episodes-an-umbrella-review-of-systematic-reviews-and-metaanalyses/9D99C2A86D3339D5F2F5D1E7D45F558D [Accessed 6 March 2025].
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US Food and Drug Administration, 2008. FDA permits marketing of transcranial magnetic stimulation for depression treatment. [online] Available at: https://www.fda.gov/news-events/press-announcements/fda-permits-marketing-transcranial-magnetic-stimulation-depression-treatment [Accessed 6 March 2025].
