How It Is Done continued...
You will be asked to lie on
a table or bed or sit in a reclining chair so your muscles are relaxed.
The skin over the areas to be
tested is cleaned. A needle electrode that is attached by
wires to a recording machine is inserted into a muscle.
When the electrodes are in place, the electrical activity in that muscle
is recorded while the muscle is at rest. Then the technologist or doctor asks
you to tighten (contract) the muscle slowly and steadily. This electrical
activity is recorded.
The electrode may be moved a number of times
to record the activity in different areas of the muscle or in different
The electrical activity in the muscle is shown as wavy
and spiky lines on a video monitor and may also be heard
on a loudspeaker as machine gun-like popping sounds when you contract the
muscle. The activity may also be recorded on video.
An EMG may
take 30 to 60 minutes. When the test is done, the electrodes are removed and
those areas of the skin where a needle was inserted are cleaned. You may be
given pain medicine if any of the test areas are sore.
Nerve conduction studies
In this test, several
flat metal disc electrodes are attached to your skin with tape or a paste. A shock-emitting electrode is placed directly over the nerve, and a
recording electrode is placed over the muscles controlled by that nerve.
Several quick electrical pulses are given to the nerve, and the time it takes
for the muscle to contract in response to the electrical pulse is recorded. The
speed of the response is called the conduction velocity.
nerves on the other side of the body may be studied for comparison. When the
test is done, the electrodes are removed.
studies are done before an EMG if both tests are being done. Nerve conduction
tests may take from 15 minutes to 1 hour or more, depending on how many nerves
and muscles are studied.
How It Feels
During an EMG test, you
may feel a quick, sharp pain when the needle electrode is put into a muscle.
After the test, you may be sore and have a tingling feeling in your muscles
for 1 to 2 hours. If your pain gets worse or you have swelling, tenderness, or
pus at any of the needle sites, call your doctor.
With the nerve
conduction studies, you may feel a quick, burning pain, a tingling feeling, and
a twitching of the muscle each time the electrical pulse is given. It feels
like the kind of tingling you feel when you rub your feet on the carpet and
then touch a metal object. The tests make some people anxious. Keep in mind
that only a very low-voltage electrical current is used, and each electrical
pulse is very quick (less than a split-second).