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What
is TMS?
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 TMS?
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 TMS?
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.
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