The notion that passing magnets over people’s heads could make them happier has been around for a very, very long time, at least since the 1770s. The Viennese physician Franz Anton Mesmer used the technique in front of large 18th century audiences, and was so successful that Louis XVI funded the establishment of a “Magnetic Institute” in France to work on the technique further.
Of course, Mesmer’s techniques likely had nothing to do with magnetism, but were early forms of hypnosis. TCR brings you this historical snippet not to imply that rTMS (repetitive Transcranial Magnetic Stimulation) is quackery, but to point out that the technique has some historical baggage to struggle against, and that we should be sure that the scientific method is in operation before embracing this technique.
First of all, what is rTMS? Going back to high school physics, recall that if you pulse electricity through a coil, it magically creates a magnetic field. Even more fascinating, when that magnetic field touches a source of electrons (like neurons), it makes them flow. So, in an electromagnetic sense, rTMS is a kindler, gentler version of ECT. Rather than zapping electrons directly into the brain via scalp electrodes (the ECT way), rTMS induces electrical flow indirectly, by massaging the brain with a magnetic field.
The actual machine is a box that plugs into the wall, with a metal magnetic coil (either round or figure-eight) attached to it. Your patient comes into your office, sits down, and you start by figuring out his or her motor threshold–the pulse intensity required to cause the thumb to twitch. Using this as a guide, you adjust the intensity and frequency settings, position the coil over your patient’s left frontal lobe, and flick the switch. Each session lasts about 20-30 minutes, and patients typically receive them daily for 2 to 4 weeks. Some patients complain of scalp pain or headache, but few discontinue treatment because of these side effects. The potentially big issue is whether rTMS may cause seizures. According to an industry website, there have been eight seizures reported with rTMS treatment, but since safety guidelines were published in 1998, there have been no seizures at all. The FDA will likely pore over this issue in great detail once an application for approval is submitted.
One more issue: Does rTMS work? Probably. It has been about a decade since the first case report of rTMS for depression was published (Hum Psychopharmacol 1993; 8:361-365), and since that time the pace of rTMS research has accelerated with each year. A good overview of rTMS, published last year (Am J Psychiatry 2003; 160:835-845), reviewed 14 controlled studies of rTMS for major depression.
Two types of controlled studies have been conducted. In the first type, genuine rTMS is compared with a “sham” condition in which the coil touches the patient’s head but is angled so that the magnetic field causes only minimal electrical discharge. The majority of studies have reported that rTMS works significantly better than sham. Parameters that increase response rates include a longer duration of treatment, a higher intensity of treatment (a stronger magnetic field, usually measured as the percent of the magnetic field that is required to cause a muscle to twitch–“percent of motor threshold”), and more pulses per treatment.
The more clinically relevant comparison is between rTMS and ECT, and thus far four such studies have been published. The upshot is that response rates are comparable, with the exception of a clear advantage in favor of ECT for those with psychotic depression. The crucial addendum here is that rTMS causes no memory loss, whereas ECT does.
Thus, rTMS appears to work for the treatment of depression. It has already been approved by regulatory authorities in Canada, Australia, Israel, and several European countries. Currently, a multisite trial of rTMS is underway in the United States in which 300 patients are being recruited. Depending on the results, the rTMS procedure will probably be submitted to the FDA for approval by Fall 2005. Those familiar with the trial are bullish that the technology will be approved for treating depression, and that psychiatrists will finally have an office-based procedure to call their own.
TCR VERDICT: rTMS: Lose your depression, and keep your mind.