Electromyogram (EMG) and Nerve Conduction Studies
(EMG) measures the electrical activity of muscles at rest and during
contraction. Nerve conduction studies measure how well and how fast the nerves
can send electrical signals.
Nerves control the muscles in the body with
electrical signals called impulses. These impulses make the muscles react in
specific ways. Nerve and muscle problems cause the muscles to react in
If you have leg pain or numbness, you may have these tests to find out how much your nerves are being affected. These tests check how well your spinal nerves and the nerves in your arms and legs are working.
Why It Is Done
EMG is done to:
- Find diseases that damage muscle tissue, nerves, or the junctions
between nerve and muscle. These problems may include
herniated disc, amyotrophic lateral sclerosis (ALS),
myasthenia gravis (MG).
- Find the cause of weakness, paralysis, or muscle twitching.
Problems in a muscle, the nerves supplying a muscle, the spinal cord, or the
area of the brain that controls a muscle can cause these symptoms. The EMG does
not show brain or spinal cord diseases.
A nerve conduction studynerve conduction study is done
- Find damage to the peripheral nervous system, which includes all
the nerves that lead away from the brain and spinal cord and the smaller nerves
that branch out from those nerves. This test is often used to
help find nerve problems such as
carpal tunnel syndrome or
How To Prepare
Tell your doctor if you:
- Are taking any medicines. Certain medicines that affect the
nervous system can change electromyogram (EMG)
results. You may need to stop taking these medicines 3 to 6 days before the
- Have had bleeding problems or take blood thinners, such as
warfarin or heparin. If you take blood thinners, your doctor will
tell you when to stop taking them before the test.
- Have a
Do not smoke for 3 hours before the test.
not eat or drink foods that contain caffeine (such as coffee, tea, cola, and
chocolate) for 2 to 3 hours before the test.
clothing so your muscles and nerves can be tested. You may be given a hospital
gown to wear.
You may be asked to sign a consent form that says you understand the risks of the test and agree to have it done.
Talk to your doctor about any concerns you have regarding the need for the
test, its risks, how it will be done, or what the results will mean. To help
you understand the importance of this test, fill out the
medical test information form(What is a PDF document?).
How It Is Done
An EMG is done in a
hospital, clinic, or doctor's office. It may be done in a room that stops any outside
electrical interference. The test may be done by an EMG
technologist or a doctor.