Repetitive transcranial magnetic stimulation (rTMS) uses a magnet to activate the brain. First developed in 1985, rTMS has been studied as a treatment for depression, psychosis, anxiety, and other disorders.
Unlike ECT, in which electrical stimulation is more generalized, rTMS can be targeted to a specific site in the brain. Scientists believe that focusing on a specific site in the brain reduces the chance for the types of side effects associated with ECT. But opinions vary as to what site is best.
rTMS: Why it’s done
In 2008, rTMS was approved for use by the FDA as a treatment for major depression for patients who do not respond to at least one antidepressant medication in the current episode. It is also used in other countries as a treatment for depression in patients who have not responded to medications and who might otherwise be considered for ECT.
The evidence supporting rTMS for depression was mixed until the first large clinical trial , funded by NIMH, was published in 2010. The trial found that 14% achieved remission with rTMS compared to 5% with an inactive (sham) treatment. After the trial ended, patients could enter a second phase in which everyone, including those who previously received the sham treatment, was given rTMS. Remission rates during the second phase climbed to nearly 30%. A sham treatment is like a placebo, but instead of being an inactive pill, it’s an inactive procedure that mimics real rTMS.
rTMS: How it works
A typical rTMS session lasts 30 to 60 minutes and does not require anesthesia.
During the procedure:
- An electromagnetic coil is held against the forehead near an area of the brain that is thought to be involved in mood regulation.
- Then, short electromagnetic pulses are administered through the coil. The magnetic pulses easily pass through the skull, and causes small electrical currents that stimulate nerve cells in the targeted brain region.
Because this type of pulse generally does not reach further than two inches into the brain, scientists can select which parts of the brain will be affected and which will not be. The magnetic field is about the same strength as that of a magnetic resonance imaging (MRI) scan. Generally, the person feels a slight knocking or tapping on the head as the pulses are administered.
Not all scientists agree on the best way to position the magnet on the patient's head or give the electromagnetic pulses. They also do not yet know if rTMS works best when given as a single treatment or combined with medication and/or psychotherapy. More research is underway to determine the safest and most effective uses of rTMS.
rTMS: Side Effects
Sometimes a person may have discomfort at the site on the head where the magnet is placed. The muscles of the scalp, jaw or face may contract or tingle during the procedure. Mild headaches or brief lightheadedness may result. It is also possible that the procedure could cause a seizure, although documented incidences of this are uncommon. Two large-scale studies on the safety of rTMS found that most side effects, such as headaches or scalp discomfort, were mild or moderate, and no seizures occurred. Because the treatment is relatively new, however, long-term side effects are unknown.