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Magnetic Stimulation Studied as Alternative to ECT for Depression
Magnetic stimulation of the brain's left prefrontal
cortex may help some depressed patients in much the same way as
electroconvulsive therapy (ECT), but without its side effects,
suggests a preliminary study by Mark George, M.D., of the
National Institute of Mental Health (NIMH), Eric Wassermann,
M.D., National Institute on Neurological Disorders and Stroke
(NINDS), and NIH colleagues.
They found that two of six medication-resistant patients
showed marked mood improvement after treatment with repetitive
Transcranial Magnetic Stimulation (rTMS) over several days. One
of the two responders, a middle-aged woman, reported feeling well
for the first time in three years. Two other patients
experienced slight mood improvement and two no improvement
following the experimental procedure, which employs an
electromagnetic coil that induces a current in the brain's
The treatment is administered daily for at least a week,
much like ECT, except that subjects remain awake. Although
proven effective for depression, ECT entails risks associated
with a seizure, occasional memory loss, and general anesthesia,
which is required. In the pilot rTMS study, two patients
developed mild headaches, treatable with aspirin -- the only
reported side effects. However, rTMS does entail some risk,
especially for seizure-prone individuals, and would not
neccessarily help all patients who respond to ECT.
Unlike electricity, which gets diffused by the skull,
high intensity magnetic pulses pass readily through bone, making
possible more focused targeting of particular brain structures.
The NIMH investigators aimed the magnet at the brain's left
prefrontal cortex, since it has been implicated as a site of
abnormally low metabolism in studies of depression. PET (positron
emission tomography) scans performed in one patient during and
after treatment showed widespread increases in metabolism,
hinting that the magnet's effects may be broadly telegraphed via
interconnected brain circuitry, suggests Dr. George. A
controlled trial of rTMS for depression is currently underway at
NIMH -- the first of a series required before its safety and
efficacy can be established.
Researchers hope this and other work with magnetic
stimulation will shed light on the mechanism of action of ECT,
which remains a mystery. If magnetic pulses can produce an
antidepressant effect, then the seizure that occurs in ECT may
not be necessary.
Evidence is emerging from animal studies about how
electrical currents, such as those induced in rTMS, might alter
brain mechanisms. For example, NIMH's Susan Weiss, Ph.D., finds
that low frequency electrical stimulation triggers lasting
anticonvulsant effects in rats. Other investigators have found
that magnetic stimulation produces an antidepressant effect in
some animal models of depression.
In addition to its possible therapeutic potential, rTMS
is also being used as a selective probe in studies of human brain
function. For example, depending on where the coil is placed, it
can disrupt speech or interfere with different types of memory.
Investigators are also following up clues that it may trigger
different emotional states in normal subjects, depending upon
Findings of the pilot study were published in the Oct 2
issue of Neuroreport. In addition to George and Wassermann,
co-authors of the article, "Daily repetitive transcranial
magnetic stimulation (rTMS) improves mood in depression," are:
Drs. Ann Callahan, Terrence Ketter, Robert Post (NIMH), Mark
Hallett (NINDS), Wendol Williams (National Institute on Alcohol
Abuse and Alcoholism), and Peter Basser (National Center for
NIMH and NINDS are components of the National Institutes
of Health, an agency of the U.S. Public Health Service, part of
the U.S. Department of Health and Human Services.
Information provided by the NIMH.