Electromyography (EMG) and Nerve Conduction Studies
Reviewed
Also called: EMG and Nerve Conduction Studies, Electrodiagnostic Study, EMG Test, Electromyogram, NCS, Nerve Conduction Velocity (NCV)
Electromyography (EMG) and nerve conduction studies are tests that check how well your muscles and the nerves that control them are working.
Specimen: Not applicable (this is a procedure, not a laboratory test).
Why this test may be ordered
- Muscle weakness
- Tingling or numbness in arms, legs, hands, feet, and/or face
- Muscle cramps, spasms, and/or twitching
- Paralysis of any muscles
Preparation and collection
Tell your provider if you have a pacemaker or cardiac defibrillator. Special steps will need to be taken before the test if you have one of these devices. Tell your provider if you take blood thinner medicines. If you're taking blood thinners, you may need to watch for more bleeding from the needle. Don't use lotions, creams, or perfumes for a day or two before the test.
Your provider will place a small needle with an electrode into the muscle. You may have slight pain or discomfort when the electrode is inserted. An EMG test may take from 30 to 60 minutes. Your provider will stick electrodes to your skin above a nerve they're checking. A nerve conduction test may take from 15 minutes to over an hour.
You may feel mild pain during an EMG test. Let your provider know if your pain becomes very uncomfortable because this may change your test results. The muscles that were tested may be sore for a few days after the test. You may also have some bruises on your skin where the needles were placed.
Understanding results
To understand the results of an EMG test or nerve conduction study, your provider will consider your symptoms, medical history, and the results of other tests.
- Normal muscle activity: A healthy muscle should not give off any electrical signals when you aren't moving it. Limitation: Let your provider know if your pain becomes very uncomfortable because this may change your test results. Next step: If you have questions about your results, talk to your provider.
- Not normal: If your results are not normal, it can be a sign of many different conditions. Limitation: Depending on which muscles or nerves are affected, it could mean one of the following. Next step: To understand the results of an EMG test or nerve conduction study, your provider will consider your symptoms, medical history, and the results of other tests.
- EMG may cause mild pain or discomfort when the needle electrode is inserted; if pain becomes very uncomfortable it may change test results.
- NCS may cause a mild tingling feeling (like mild static electricity) during the electrical pulse.
- The muscles tested may be sore for a few days after the test, and there may be some bruising where needles were placed.
- Results are not diagnostic on their own; your provider will consider your symptoms, medical history, and other test results.
What to do next
If you have questions about your results, talk to your provider.
- What symptoms led to this test being recommended?
- What do my results mean in combination with my medical history and other tests?
- Do I need any follow-up tests or appointments?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.
U.S. National Library of Medicine: Electromyography (EMG) and Nerve Conduction Studies