EMG and NCS Tests

Electromyography (EMG) and nerve conduction studies (NCS) are tests that measure muscle and nerve function. In most cases, both tests are done. NCS is most often done first. You will be asked to lie on an exam table with a blanket over you. You may have 1 or more of the following.

Nerve conduction study (NCS)

Waveforms produced during NCS

During NCS, mild electrical currents are used to test how fast electrical signals move along your nerves. Small metal disks (electrodes) will be attached to your skin on the part of your body being tested. This will be done using water-based gel or paste. A doctor or technologist will apply mild electrical currents to your skin. Your muscles will twitch, but the test won’t harm you. Currents are usually applied to the same area several times. Usually the intensity of the electrical stimulation is increased on each body part. There may be some increasing mild pain that varies from person to person. But the electrical shock is not dangerous. The test may continue on other parts of your body unless the reason for doing the test is limited to a small part of the body.

Electromyography (EMG)

An EMG waveform

Most of the electrodes will be removed for EMG. The healthcare provider will clean the area being tested with alcohol. A very thin sterile needle will be inserted into the muscles in this area. When the needle is inserted, you may feel as if your skin is being pinched. Try to relax and do as instructed, as you will be asked to relax and contract the muscle being tested. Following instructions will allow your provider to interpret the test results.

During each test, wavy lines (waveforms) appear on a screen or on paper. These lines show how well your nerves and muscles work. These waveforms help to determine your test results.

Before the test

Prepare for your test as instructed. Shower or bathe, but don't use powder, oil, or lotion. Your skin should be clean and free of excess oil. Wear loose clothes. But know that you may be asked to change into a hospital gown. The entire test will take about 60 minutes. Allow extra time to check in.

Let the technologist know

For your safety and for the success of your test, tell the technologist if you:

  • Have any bleeding problems

  • Take blood thinners (anticoagulants) or other medicines, including aspirin

  • Have any immune system problems

  • Have had neck or back surgery

You may also be asked questions about your overall health.

After the test

Before you leave, all electrodes will be removed. You can then get right back to your normal routine. If you feel tired or have some mild pain, take it easy. If you were told to stop taking any medicines for your test, ask when you can start taking them again. Your healthcare provider will let you know when your test results are ready.