Electromyography
and Nerve Conduction Studies (EMG)
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What is the
test?
Electromyography (EMG) tests analyze nerve and
muscle electrical activity. Some types of electrical
activity are normal, whereas some patterns of
electrical activity suggest a disease of nerves
or muscles. Nerve conduction studies are tests
that are often used in combination with the EMG
evaluation. For nerve conduction studies, the
muscles and nerves are stimulated with small
bursts of electricity to see whether the nerves
and muscles respond in a normal way.
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How
do I prepare for the test?
No preparation is necessary.
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What
happens when the test is performed?
For the EMG, thin needles are inserted one by
one into the muscles being tested. These needles
are not hollow, and they are thinner than the
type of needle used to draw blood. Each needle
is attached to a wire that gives signals to a
machine. The needle acts like an antenna to detect
electrical patterns inside the muscle and the
nerves that are attached to that muscle. Most
patients find this test mildly uncomfortable.
If you have nerve conduction studies done, small
pads are taped to the skin on your hands or feet.
These pads can both deliver mild electric shocks
and detect electric signals coming through the
skin. The shocks that are used are too small
to be harmful. They feel similar to the kind
of shock you might feel if you rubbed your feet
on the carpet and then touched a doorknob. You
might feel one of your muscles twitch when the
electricity is delivered.
Testing times vary, depending on how many muscles
are being tested. EMG testing takes 20 to 30
minutes. If nerve conduction studies are also
done, testing may require as long as one hour.
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What
risks are there from the test?
There are no risks. The needles used in the
EMG are too small to put you at significant risk
for bleeding or infection. The shocks do not
shock your whole body and are too mild to cause
any damage.
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Must
I do anything special after the test is over?
No.
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How
long is it before the result of the test is
known?
A neurologist interprets the electrical signals
measured in your muscles and sends a report to
your doctor within a few days.
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