Electromyography (EMG) and Nerve Conduction Studies
Electromyography (EMG) and nerve conduction studies are tests that check how well your muscles and the nerves that control them are working.
Electromyography (EMG) and nerve conduction studies are tests that check how well your muscles and the nerves that control them are working. These nerves control your muscles by sending out electrical signals to make your muscles move. As your muscles react by tightening (contracting), they give off electrical activity, which can then be measured. An EMG test looks at the electrical signals your muscles make when they are at rest and when used. A healthy muscle should not give off any electrical signals when you aren't moving it. If your muscle is damaged, it may show electrical activity while at rest or activity that is not normal while using it. A nerve conduction study measures how fast and how well your body's electrical signals move along your nerves. A damaged nerve has a slower and weaker signal. This test can help check for nerve damage. EMG tests and nerve conduction studies can help find out if you have a health condition that has damaged your muscles or nerves or how they work together. These tests can be done separately, but they are usually done at the same time. Other names: electrodiagnostic study, EMG test, electromyogram, NCS, nerve conduction velocity, NCV
Why is this test ordered? You may need these tests if you have symptoms of a muscle or nerve disorder. These symptoms include: Muscle weakness Tingling or numbness in arms, legs, hands, feet, and/or face Muscle cramps , spasms, and/or twitching Paralysis of any muscles
Clinical Interpretation
If your results are not normal, it can be a sign of many different conditions. Depending on which muscles or nerves are affected, it could mean one of the following: Carpal tunnel syndrome , a common condition that affects nerves in the hand and arm. It causes numbness, tingling, weakness, or pain in your wrist or hand. Herniated disk , a condition that happens when a part of your spine, called a disk, is damaged. Part of the disk bulges or pushes out, putting pressure on the spine which causes pain and numbness. Guillain-Barré syndrome , a rare disorder that causes your immune system to attack your nerves. It can lead to numbness, tingling, and paralysis. Myasthenia gravis , a rare disease that causes weakness in the muscles you can control. They may include your muscles for eye movement, facial expressions, or other muscles. Muscular dystrophy (MD) , a group of genetic diseases that cause muscle weakness. This weakness can lead to trouble walking and the ability to care for yourself. Charcot-Marie-Tooth disease (CMT) , a group of nerve disorders that are inherited (passed down through families). CMT causes nerve damage and muscle weakness, mostly in the arms and legs. Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease. It is a disorder that attacks nerve cells in your brain and spinal cord. It affects all the muscles you use to move, speak, eat, and breathe. There is no cure for ALS, and it gets worse over time. 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. If you have questions about your results, talk to your provider. Learn more about laboratory tests, reference ranges, and understanding results .
Clinical Protocol & Patient Advice
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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. Wear loose, comfortable clothing for easy access to the test area. It can be easily removed if you need to change into a hospital gown. Make sure your skin is clean. Don't use lotions, creams, or perfumes for a day or two before the test. They can change the results of the test.
Usage Guidance
- Reference ranges vary by laboratory. Always discuss your specific results with a qualified healthcare professional.
Source: MedlinePlus, National Library of Medicine. View the original.