Resources - Transcranial Magnetic Stimulation (TMS)
What is rTMS?
Transcranial magnetic stimulation (TMS) utilizes an electromagnet placed on the scalp that generates magnetic field pulses roughly the strength of an MRI scan. The magnetic pulses pass readily through the skull and stimulate the underlying cerebral cortex. Low frequency (once per second) TMS has been shown to induce sustained reductions in brain activation while stimulation at higher frequencies (> 5 pulses per second) has been shown to increase brain activation.
What conditions has it been shown to be useful in?
TMS is currently being investigated as potential treatment for patients with depression and for patients who experience hallucinated "voices." For patients with depression, many, but by no means all studies have shown clinical improvement following both low and high frequency TMS. For patients reporting hallucinations research has not been as extensive but initial results have been promising and suggest that low frequency TMS administered to parts of the brain underlying speech perception reduces voices. The Food and Drug Administration has not approved TMS as a psychiatric treatment. Therefore TMS is only available as a research procedure. TMS has been approved in Canada as a treatment of depression for patients who have not responded to medication and who would ordinarily receive a trial of electroconvulsive therapy (ECT).
What does it feel like to receive rTMS?
Generally TMS produces a knocking sensation on the head. When administered at some stimulation sites it can cause contraction of the muscles of the scalp and occasionally the jaw. Mild headache and transient lightheadedness can sometimes result from TMS.
Do you get anesthetized?
No.
Does it hurt?
Approximately 5-10% of patients experience pain at the site of stimulation. In general this has not been a problem when administering TMS to patients volunteering for research studies.
How long does a session last?
It depends on the protocol, but generally each session takes about a half an hour.
How many times do you need to receive it?
Most protocols require at least two weeks of daily stimulation given five times per week.
Are there any side-effects or risks associated with rTMS?
Yes. The main risk is inducing a seizure, though with close monitoring this complication has been very rare. For stimulation at low frequency (once per second) there have been no reports of seizures. Insofar as the brain is directly stimulated by TMS, there is a potential risk of a disturbance of memory, concentration and other cognitive capacities. A very small number of patients with schizophrenia (i.e., less than 5%) have reported such difficulties following TMS, but these problems have appeared to go away within 24 to 48 hours after the TMS has been stopped. In addition, evidence that these difficulties were actually caused by TMS, as opposed to the patient's other symptoms, has been unclear. These problems, when they occur, are much milder than the sorts of problems commonly experienced following electroconvulsive therapy.
Is it widely available to patients in the U.S.?
No. TMS is available only at a limited number of research centers in the US.
Reviewed by Ralph Hoffman, MD May 2003
