Magnetic brain stimulation or TMS is a non-invasive way to stimulate the brain based on electromagnetic induction by an insulated coil. TMS stands for Transcranial Magnetic Stimulation.
This coil is placed on the scalp and at a point corresponding to the area of the brain that is involved in the development of psychiatric or neurological symptoms. The coil generates short-duration magnetic pulses that are similar in type and strength to an MRI machine. Each magnetic pulse easily and painlessly passes through the scalp and bones and membranes of the brain and reaches the neurons and causes the short-term activity of the corresponding neurons. If the pulses are administered quickly and sequentially, it is called repetitive TMS or rTMS, which is capable of creating more stable changes in brain activity.
What is the mechanism of action of rTMS brain magnetic stimulation?
According to several studies conducted on psychiatric disorders and on the metabolism of relevant brain regions, it has been suggested that the increase or decrease in the metabolism of certain brain regions leads to the development of psychiatric symptoms. For example, increasing the activity of the right dorsolateral prefrontal area or decreasing the activity of the left prefrontal dorsolateral area or the asymmetry of these two areas can cause major depressive disorder.
Based on this, by restraining or stimulating the mentioned areas, it is possible to mitigate or treat the relevant disorder. This procedure is performed in rTMS brain magnetic stimulation by creating a magnetic field and applying it on the scalp. The frequency of the generated pulse (number of pulses per second) determines the inhibitory or excitatory property on brain neurons.
When is rTMS magnetic brain stimulation used?
In depressed patients who have not responded well to a course of medication or psychotherapy, rTMS can be prescribed as an adjunctive or alternative treatment. rTMS magnetic brain stimulation has been approved by the FDA in October 2008 for the treatment of major depression patients who have not responded to or are unable to tolerate at least one course of antidepressant medication in the current episode of the disease.
The efficacy of rTMS brain magnetic stimulation in other psychiatric disorders such as OCD, anxiety disorders and auditory hallucinations and negative symptoms of schizophrenia that are resistant to drug treatment has been confirmed in various articles, but has not yet been approved by the FDA.
The effectiveness of rTMS in other areas of neurology is also under investigation, such as cerebral ischemic events, Parkinson’s disease, etc.
What is the treatment process with rTMS brain magnetic stimulation?
rTMS brain magnetic stimulation can be implemented in outpatients and inpatients and is prescribed as multiple treatment sessions. In each treatment session, the patient sits on a chair designed for this purpose (not dissimilar to a dental unit). Due to the creation of a magnetic field, the patient is asked to remove all objects sensitive to magnetism (such as credit cards and head and neck jewelry) before starting the treatment process. If possible, he will be given hearing protectors (in-ear pads) so that he will not be harmed by the generated pulse sound or magnetic waves.
The operator places the patient’s head in a suitable position and measures certain parameters on the patient’s skull to determine the exact location of the device’s coil on the desired area of the brain. Then he started to determine the motor threshold of the patient, which is the minimum magnetic power required to cause contraction in the patient’s hand, which differs from person to person. This action is done by setting the device to produce a single pulse. Determining the movement threshold enables the psychiatrist to design a specific treatment plan for each person so that the patient receives the right amount of magnetic energy, neither more nor less than needed to create therapeutic effects.
After these measures, the coil is again placed on the patient’s head in the corresponding place based on the patient’s psychiatric disorder. During the treatment process, the patient will only feel the clicking sound and a brief impact caused by the pulse in the area under the coil.
During the entire rTMS brain magnetic stimulation treatment session, the operator is present and monitors the patient and interrupts the treatment session if the patient wishes. Each treatment session lasts 20-40 minutes and is generally repeated 3-5 days a week. The entire treatment period lasts 4-6 weeks, which varies depending on the type of psychiatric disorder, its severity and the patient’s treatment response.
Are there any treatments similar to rTMS brain magnetic stimulation?
The rTMS brain magnetic stimulation method is included in a larger subcategory called brain stimulation treatments. In all these methods, the goal of treatment is to affect the activity of brain neurons through a non-pharmacological method. Other methods include ECT or brain shock, tDCS/tES electrical stimulation of the brain, VNS stimulation of the vagus nerve, DBS deep brain stimulation. ECT has been used in psychiatric treatment for 70 years and its effectiveness has been confirmed.