rTMS
An introduction to electroconvulsive therapy (ECT)
What is TMS?
This term is the abbreviation of “Transcranial Magnetic Stimulation”. It is a non-invasive method to stimulate the brain based on electromagnetic induction by an insulated coil. This coil is placed on the scalp, at a point corresponding to the area of the brain that is involved in the development of psychiatric or neurological symptoms. It generates short-term magnetic pulses which are similar to those of MRI device in terms of type and strength. Each magnetic pulse passes through scalp and bone and brain membranes easily and without pain, reaches neurons, and leads to short-term activity in the target neurons. If the pulses are administered frequently and quickly, it is called repetitive TMS or rTMS which can make more stable change in brain activities.
What is rMTS mechanism like?
According to various studies that have focused on psychiatric disorders and metabolism of different brain regions, it can be concluded that an increase or decrease in the metabolism of certain regions of the brain leads to emergence of psychiatric symptoms. For example, an increase in the activity of right dorsolateral prefrontal area or a decrease in the activity of left dorsolateral prefrontal area or asymmetry of these two areas can cause major depressive disorder. As a result, by controlling or stimulating the mentioned areas, the disorder can be alleviated or treated. This is carried out in rTMS by generating and applying a magnetic field on the scalp. The frequency of the generated pulse (the number of pulses per second) determines the stimulating or inhibitory effects on neurons.
When is rTMS used?
In depressed patients who have not responded appropriately to a trial of pharmacotherapy or psychotherapy, rTMS can be administered as an adjuvant or alternative therapy. This method was approved by the US Food and Drug Administration (FDA) in October 2008 in order to treat patients who suffer from major depression, and have not responded to at least one adequate trial of antidepressant in the current episode or cannot tolerate medications.
Efficacy of this method in other psychiatric disorders such as OCD, anxiety disorders, and paracusia (i.e. auditory hallucination), and negative symptoms of schizophrenia in patients who have been resistant to pharmacotherapy has been verified in different studies, but it has not yet been approved by FDA.
The efficacy of rTMS in neurological disorders such as ischemic cerebrovascular accidents, Parkinson’s disease, and so on is also under investigation.
What is the process of rTMS treatment like?
This treatment method can be conducted in outpatient and hospitalized settings. It is administered in several therapy sessions. In each therapy session, the patient sits on a chair designed for this purpose (similar to dental chairs). Due to the magnetic field, the patient is asked to put aside all his/her magnet-sensitive objects (such as credit cards or jewelry worn on head or neck). If possible, he/she is given hearing protectors (ear muffs) in order to prevent probable injury due to the sound of the generated pulses or magnetic signals.
The operator puts the patient’s head in a suitable position, and tries to measure certain parameters on the patient’s skull in order to find the exact location to place the coil on. Afterwards, the operator determines the patient’s motor threshold which is the minimum magnetic power needed to contract the patient’s hand, which is different for different individuals. This is done by generating a single pulse. Determining motor threshold enables the psychiatrist to design a unique treatment plan for each patient, so that the patient can receive an appropriate amount of magnetic energy, not more and not less than the amount needed for therapeutic impact.
After this, based on the patient’s psychiatric disorder(s), the coil is placed on the respective location on his/her head again. During the therapy process, the patient only feels the sound of clicking and slight claps caused by generating pulses under the coil.
All over the therapy session, the operator is present and monitors the patient, and if the patient wishes, the session will be terminated. Each session lasts 20-40 minutes and is generally repeated 3 to 5 days per week. The whole therapy period lasts 4 to 6 weeks, which varies depending on the type of psychiatric disorder, its severity, and the patient’s level of response.
Are there similar treatment methods to rTMS?
The method of rTMS belongs to a larger set called “Brain Stimulation Methods”. All of these methods are aimed at influencing the activity of neurons through a non-pharmacological method. Other methods include Electro-Convulsive Therapy (ECT), Vagus Nerve Stimulation (VNS), Deep Brain Stimulation (DBS), etc. Among these methods, ECT is more common. ECT has been utilized in psychiatry since 70 years ago, and its efficacy has been approved. This method is more readily accessible than other brain stimulation methods.