Biomedical Frontiers: Winter/Spring 1996, Vol.3, No.2
Clinical Research
TMS vs. Depression

The use of magnetic pulses to stimulate the brain holds promise as a replacement for electroconvulsive therapy (ECT), considered the most effective depression treatment. In the lab of Dr. Harold A. Sackeim, professor of psychiatry at Columbia and chief of biological psychiatry at NYSPI, researchers are at the forefront of the investigation into this therapy, known as transcranial magnetic stimulation (TMS).

ECT is more effective than antidepressant medications but, because of its many drawbacks, is used mainly for severe cases of depression that do not respond to other treatment. TMS, however, may overcome some of the drawbacks of ECT while still retaining its effectiveness. For instance, one of the drawbacks of ECT is getting the electric current past the skull, which is an excellent insulator. The skull "smears" the electricity, so that it is impossible to control exactly where the current goes in the brain or the exact amount. This also makes it impossible to stop a seizure from spreading through the brain.

"Columbia, which is generally considered the leading center for ECT research in the world, is uniquely positioned to replace ECT."

With TMS, these problems may be eliminated because the magnetic field does not have to overcome resistance and cannot be distorted by the scalp and skull, making it possible to determine exactly which area of the brain will be stimulated, says Dr. Sackeim.

Furthermore, TMS can deliver a controlled, precise dose, unlike ECT, which, research at Columbia has shown, can often result in an overdose. "We found that there's a 40-fold range among people in the amount of electricity needed to produce a seizure," says Dr. Sackeim. "So for many people, the standard dose of ECT is actually an overdose."

Researchers are currently working on a variety of projects involving TMS. For instance, one of the challenges in developing TMS is engineering a device powerful enough to deliver a train of stimuli that will initiate a self-sustaining seizure in a patient who is under anesthesia. "This will have to be a far more powerful device than has ever been built before," says Dr. Sackeim. Once built, such a device would have research and clinical applications. TMS is currently being used to "map" the brain by producing "reversible lesions" in normal subjects: The technology allows researchers to safely and temporarily inhibit or stimulate a brain function. In addition, a future double-blind study will investigate the use of non-convulsive TMS to treat depression. "Columbia, which is generally considered the leading center for ECT research in the world, is uniquely positioned to replace ECT," says Dr. Sackeim. "We're at the very beginning of a new field."

Research on the use of transcranial magnetic stimulation to treat depression is just beginning. Magstim Rapid device courtesy Magstim Company Limited