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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 performed. NCS is most often done first.

What Happens During These Tests?

Line showing normal EMG waveform. Line is pattern of peaks and valleys.

Two parallel lines showing normal NCS waveform. Lines show one peak and valley.

  • EMG assesses muscle function. To do this, a fine needle is placed under your skin into the muscle being tested. This is repeated on other muscles. The needle allows the electrical activity in your muscles to be measured. No electrical currents are applied with the needle.

  • NCS checks how quickly impulses travel along the nerves. To do this, mild electrical currents are applied to the skin on some parts of your body.

  • 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 to 90 minutes. Be sure to 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 medications, including aspirin.

  • Have a pacemaker or cardiac defibrillator

  • Have any immune system problems.

  • Have had neck or back surgery.

You may also be asked questions about your overall health.

Author: StayWell Custom Communications
Last Annual Review Date: 5/15/2011

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