What are Nerve Conduction Studies (NCS) and Electromyography (EMG)?
Nerve Conduction Studies and Electromyography test the electrical activity and health of nerves and muscles. Nerve Conduction studies test the status of nerves while Electromyography (EMG) provides information about the health of nerves and muscles. Both tests are usually performed together as part of an evaluation requested by your physician.
Normal movement of muscles in the limbs and face depend on normal function of the nerves and muscles supplying these areas. Painful conditions such as Carpal Tunnel syndrome, radiculopathy and Sciatica are caused by abnormal electrical conduction of nerves. Damage to nerves can cause abnormal function of muscles. Patients may experience pain, numbness, tingling or weakness when the electrical activity in nerves and muscles is abnormal. Electrodiagnostic studies (NCS and EMG) can help your orthopaedic surgeon or physiatrist diagnose these painful conditions.
Before the Test
No specific preparation is needed before your test. You may take any prescribed medications prior to the test. You do NOT need to stop your pain medications prior to the test.
During the Procedure
The physician performing your test has had the actual examination performed on his or herself as is familiar with the discomfort that can occur with the test. The Nerve Conduction Studies are usually performed first. This portion of the test requires the application of wires to the skin over the tested nerve and muscle. A small, variable electrical current (up to 100 milliamps) is applied to the nerves over the skin. Most patients describe the sensation of this part of the test as “strange” or “odd” not really painful. The feeling is similar to a TENS unit or the shock experienced using an electric fence for pets. During EMG, small pins similar to acupuncture needles are inserted into muscles to measure electrical activity. This may be mildly painful with most patients rating the discomfort as a 3 to 4 out of a 10 point pain scale (10 being horrible pain). You will be asked to contract your muscles by moving a small amount during the test. The person administering the test will monitor results on a computer screen. He or she will use speakers to listen to electrical signals in the muscles.
After the Test
You will be sent home following the procedure without any restriction of activities. Some people may feel tender or bruised for a few days due to the EMG needles. You may apply ice or take Tylenol, Advil or Aleve for discomfort but this is rarely necessary.
The risks of NCS and EMG are minimal. Pin insertion causes some pain during the test. Infection is not associated with testing because sterile, disposable pins are used. There is a very small risk of bleeding into muscle tissue with patients who are on anticoagulation with Heparin or Warfarin. Please let your examiner know if you use these medications. The test can still be performed safely even with these medications. The test can be performed safely in patients who have metal implants, pacemakers, internal cardiac defibrillators or lymphedema.