Benefits of Transcranial Magnetic Stimulation on Treatment Resistant Depression
by Dr Ascione
Transcranial Magnetic Stimulation is a very successful non invasive treatment for depression and many other mental health issues. It was first introduced as a neuro-diagnostic tool. It was a tool for evoking potential in muscle tissue by activating neurons in the motor cortex. It is based on two principles within physics: Ampere’s Law and Faraday’s principle of electromagnetic induction – simply put: electricity and magnetism are interdependent.
The rTMS is an instrument that consists of multiple wire coils. These wires are encased in insulation and connected to powerful capacitors. These capacitors can pass a significant electrical current through the coil. This coil, when placed above a patient’s head, can produce rapid magnetic pulses that penetrate the skull and reach the brain. There is minimal attenuation. When the pulse is rapid enough a secondary electronic current is induced and alters the electric field local in the nerve tissue. (Basil, et al 2005).
This current is rapidly turned on and off in the coil and therefore creates a powerful magnetic field that impacts on the electric currents in the brain. The “r” stands for repetitive – but should also suggest a rhythmic pattern to the pulses – usually at a frequency higher than 1Hz.
Essentially rTMS uses alternating magnetic fields to stimulate neurons in the brain. It causes a change of excitability in the cortico-motor pathways. However, some believe that this misrepresents what happens in the brain. Instead, there is a hybrid of changes. There is the change to the excitability of neurons but also a change to the strength of connection between neurons. (Matheson et al, 2016).
NICE recommend the use of rTMS with service users who have severe depression or treatment resistant depression. NICE claim that there are “difficulties in conducting research on rTMS for depression” and that it faces “challenges of providing sham treatment, and a variable and often small response.” However, NICE also notes that “commentary from patients as positive and described significant benefits to the quality of life.” (NICE, 2018) The benefits the patients noted included, but was not limited to, the ability to stop using oral antidepressant medications.
It is interesting that both the FDA and NICE acknowledge there are no side effects for the service user when using rTMS. In contrast, the common side effects of anti-depressant tablets include: nausea, weight gain, loss of sexual desire, fatigue, insomnia, blurred vision, constipation, and many more (WebMD, 2018).
For the FDA (2018) it is the ability of rTMS to stimulate changes to neurons in the brain without the need induce seizure in patients, as is the case with ECT. The technique delivers repetitive pulsed magnetic fields of sufficient magnitude that they induce neural action in the prefrontal cortex. It is this that has been seen to treat the symptoms of major depressive disorder, without the potential harming effects of the seizure on the body. It is still possible for the patient to go into seizure with rTMS, but this risk is minimal. There is also some risk of scalp pain or discomfort, but this is described as “mild to moderate” (FDA, 2018)
Therefore, the obvious benefit of rTMS are reported positive results from patients, who no longer need to take tablets. These tablets come with significant side effects, so it is a significant bonus that the need for such medication is removed when rTMS has been used. The use of rTMS does not stimulate seizure, with all associated risk, and therefore reduces the level of discomfort to the patient. The patient is awake and the sessions last for a period of six weeks. 50% of patients experienced a reduction in symptoms of 50% – whilst only a third experience remission. The effect of the treatment is reported to be approximately 6 months from the beginning of the treatment phase. (Garcia, 2018).
Basil, B., Mahmud, J., Mathews, M., Rodriguez, C., & Adetunji, B. (2005). Is There Evidence for Effectiveness of Transcranial Magnetic Stimulation in the Treatment of Psychiatric Disorders? Psychiatry (Edgmont), 2(11), 64–69.
Chervyakov, A. (2018). Frontiers. Retrieved 15 June, 2018, from https://www.frontiersin.org/articles/10.3389/fnhum.2015.00303/full
Garcia, N. (2018). Neuromodulation. Retrieved 15 June, 2018, from http://www.neuromodulation.com/TMS
Matheson, N. A., Shemmell, J. B. H., De Ridder, D., & Reynolds, J. N. J. (2016). Understanding the Effects of Repetitive Transcranial Magnetic Stimulation on Neuronal Circuits. Frontiers in Neural Circuits, 10, 67. http://doi.org/10.3389/fncir.2016.00067
NICE. (2018). Niceorguk. Retrieved 15 June, 2018, from https://www.nice.org.uk/guidance/ipg542/chapter/6-Committee-comments
WebMD. (2018). WebMD. Retrieved 15 June, 2018, from https://www.webmd.com/depression/features/coping-with-side-effects-of-depression-treatment