Transcranial Magnetic Stimulation (TMS)

What is rTMS?

Transcranial magnetic stimulation (TMS) is a technique for gently stimulating the brain. It utilizes a specialized electromagnet placed on the patient’s scalp that generates short magnetic pulses, roughly the strength of an MRI scanner’s magnetic field but much more focused. The magnetic pulses pass easily through the skull just like the MRI scanner fields do, but because they are short pulses and not a static field, they can stimulate the underlying cerebral cortex (brain). Low frequency (once per second) TMS has been shown to induce reductions in brain activation while stimulation at higher frequencies (> 5 pulses per second) has been shown to increase brain activation. It has also been shown that these changes can last for periods of time after stimulation is stopped. TMS was first developed in 1985, and has been studied significantly since 1995.

What disorders has TMS been shown to be useful for?

TMS is currently being investigated as a potential treatment for patients with major depression, patients who experience hallucinated "voices" and a variety of other psychiatric and neurological disorders. Over 1500 patients have been studied with TMS. For patients with major depression, many, but by no means all studies have shown clinical improvement following TMS. Recent studies that have used newer technology and stronger stimulation have shown much improved results. These pilot studies have taught researchers about how to better use TMS for depression. This information is now being used in a large pivotal clinical trial which, if successful, will be used to support Food and Drug Administration (FDA) clearance of TMS thus making it available to the general public.

For patients reporting auditory hallucinations (voices), 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 may reduce these voices.

The Food and Drug Administration has not approved TMS for any psychiatric treatment at this time. Therefore TMS is only available as a research procedure. TMS has been approved in Canada and Israel as a treatment of depression for patients who have not responded to medications and who might ordinarily be considered for a trial of electroconvulsive therapy (ECT).

What does it feel like to receive TMS?

Generally TMS produces a slight knocking or tapping sensation on the head. This is also associated with a tapping sound produced by the TMS device. 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 may sometimes result from TMS. These symptoms usually resolve by themselves shortly after the treatment is over.

Do you need to get anesthetized for TMS?

No. TMS is an outpatient procedure and does not require anesthesia or an IV. It can be administered in a physician’s office or clinic.

Does it hurt?

Approximately 5-10% of patients experience discomfort 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 treatment session last?

It depends on the research protocol, but generally each session takes about a half an hour.

How many times do you need to receive TMS?

Research protocols vary in the treatment duration, but most require at least two weeks of daily stimulation given five times per week, some require up to 6 weeks.

Are there any side-effects or risks associated with rTMS?

Yes. The main risk of TMS is inducing a seizure, though with close monitoring this complication has been very rare. No seizures have been reported in the scientific literature since safety guidelines have been implemented. 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 disturbing the brain’s normal functions. However, in depression studies reported so far, no cognitive side-effects like loss of memory, negative changes in concentration and other cognitive capacities have been reported. This is in stark contract to the well known cognitive side effects associated with electroconvulsive therapy (ECT).

Is TMS widely available to patients in the U.S.?

No, not at this time. Because TMS is not yet FDA cleared, it is only available at a limited number of research centers in the US.

Why are researchers evaluating TMS?

TMS has some very unique properties. It is non-invasive, (does not break the skin and can be delivered in a physician’s office) can easily be focused on small areas of the brain, and can change brain activity. This makes it particularly well suited for treating the brain, while minimizing side effects typical with other psychiatric treatments which affect areas of the brain and body not involved in the disorder.

Specifically for major depression, researchers understand there are a significant number of patients suffering from this disorder that are not helped by the available medications and other therapies, only receive partial benefit, or are not able to take medications at all. TMS offers hope that, if proven effective, many of these patients may be able to experience symptom relief.

Reviewed by Stanford Miller July 2004

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