What is Repetitive Transcranial Magnetic Stimulation
Author: Thomas C. Weiss : Contact: Disabled World
Overview of Repetitive transcranial magnetic stimulation (rTMS), the process of using a magnet near the brain for treatments such as major depression.
Repetitive transcranial magnetic stimulation (rTMS) uses a magnet instead of an electrical current to activate a person's brain. The treatment was first developed in the year 1985 and has been studied as a potential treatment for depression, psychosis and other disorders since the mid-1990's. Clinical trials studying the effectiveness of rTMS presented mixed results.
rTMS is defined as a procedure in which cerebral electrical activity is influenced by a pulsed magnetic field. During a rTMS procedure, a magnetic field generator, or "coil", is placed near the head of the person receiving the treatment. rTMS has been shown to produce changes in neuronal activity in regions of the brain implicated in mood regulation, such as the prefrontal cortex. Recent studies have shown that stimulation over the left and right sides of the brain can have opposite effects on mood regulation.
When compared to a placebo or inactive treatment, some studies have discovered that rTMS is more effective in treatment of people with major depression. Yet other studies have found no difference in response when compared to inactive treatment. In October of 2008, rTMS was approved for use by the FDA as a form of treatment for major depression in people who have not responded to at least one antidepressant medication. It is also used in countries such as Israel and Canada as a treatment for depression in people who have not responded to medications and who may otherwise be considered for electroconvulsive therapy (ECT).
How rTMS Works
Unlike ECT, in which electrical stimulation is more generalized, rTMS can be targeted to a particular site in a person's brain. Scientists believe that focusing on a specific spot in the brain reduces the chance for the type of side-effects that are associated with ECT. Opinions; however, vary as to which spot is best.
Schematic Diagram of Transcranial Magnetic Stimulation
A typical rTMS session lasts from between thirty and sixty minutes and does not require the person to undergo anesthesia. An electromagnetic coil is held against the person's forehead near an area of the brain that is believed to be involved in the regulation of moods. Short, electromagnetic pulses are administered through the coil. The magnetic pulses pass through the person's skull and cause small electrical currents that stimulate nerve cells in the targeted region of the person's brain.
The type of pulse used does not reach further than two inches into the brain and scientists can select which parts of the person's brain will be affected and which ones will not. The magnetic field is around the same strength as that of a magnetic resonance imaging (MRI) scan. In general, the person will feel a slight tapping or knocking on their head as the pulses are administered.
A level of disagreement exists among scientists on the best way to position the magnet on the person's head, or give the electromagnetic pulses. Scientists also do not know at this time if rTMS works best when provided as a single treatment or in combination with medication. Additional research is underway to determine the safest, most effective way to use rTMS.
At times, a person might experience discomfort at the site on their head where the magnet is placed. The muscles of the person's jaw, scalp, or face might contract or tingle during the procedure. Brief lightheadedness or a mild headache may result. It is also possible that the procedure could cause a seizure, although documented incidences of this are not common. A recent large-scale study on the safety of rTMS discovered that most side-effects, such as scalp discomfort or headaches, were mild to moderate and no seizures occurred. The fact that the treatment is new; however, means long-term effects remain an unknown.
rTMS is always prescribed by a TMS doctor. All TMS doctors are specifically TMS credentialed. Motor threshold is determined by a TMS doctor. The treatment itself is administered by an experienced TMS technician under the supervision of a TMS doctor or by the TMS doctor. The TMS technician or doctor will always be present to monitor the person during their treatment. The person may stop treatment at any point by asking a staff member who is present.
Therapy using rTMS involves a series of treatment sessions. Treatment sessions are around forty minutes each and are administered five days a week. A common course of rTMS is four to six weeks. The period of time involved; however, may vary depending on the person's response to treatment. Unlike ECT, rTMS does not require any general anesthesia or sedation, so the person is fully awake and aware during the treatment. There is no recovery time involved and the person can drive home afterwards and return to their usual activities.
People Who Are Not Eligible for rTMS
People with any kind of non-removable metal in their heads, with the exception of dental fillings or braces, or within twelve inches of the coil should not receive rTMS. Failure to follow this rule could cause the object to heat up, malfunction, or move and result in serious injury or even death. The list that follows presents metal implants that may prevent a person from receiving rTMS.
- Implanted stimulators
- Aneurysm clips or coils
- Stents in the neck or brain
- Electrodes to monitor brain activity
- Metallic implants in your ears and eyes
- Shrapnel or bullet fragments in or near the head
- Facial tattoos with metallic or magnetic-sensitive ink
- Other metal devices or object implanted in or near the head
- Cardiac pacemakers or implantable cardioverter defibrillator (ICD)
Existing evidence to date suggests that people who are less treatment-resistant respond better to rTMS than people who are highly treatment-resistant. There is much yet to be learned about particular variables that might impact response to rTMS. Researchers are currently conducting clinical studies to evaluate who will benefit most from rTMS therapy. There is a great amount of interest in evaluating whether rTMS with antidepressant medications is more effective than treatment with rTMS alone.
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