Your muscles move when nerve signals from the brain tell them to get to work. Electromyography (EMG) measures how well your muscles respond to those signals.
If the test picks up a problem, you may be diagnosed with what is called a neuromuscular disorder. (WebMD)
An EMG assesses the electrical activity of a nerve root and is sometimes recommended for patients with back pain. After three weeks of pressure on a nerve root, the muscle the nerve goes to will begin to spontaneously contract. The compression of a nerve will also slow electrical conduction along that nerve. EMG’s are also sometimes useful to distinguish nerve degeneration (neuropathy) from nerve root compression. (SPINE-HEALTH)
Why would you get an EMG?
It’s natural to have soreness or numbness in a muscle once in a while. You might strain a wrist muscle lifting something heavy, for example.
For many people, though, a sore wrist is caused by an injured nerve, not an injured muscle. When it’s not clear why you’re having problems with your wrist, back, legs, or other body parts, this test may be helpful.
The tests may be given to people who have the following symptoms that don’t go away:
Pain or cramping
Tingling or numbness
The test can help doctors diagnose what’s wrong with you. They can also help rule out conditions that you don’t have. EMG and NCS are helpful in diagnosing:
Neuromuscular diseases, such as muscular dystrophy
Nerve problems in the spine, such as a herniated disk
Nerve problems elsewhere in the body, such as carpal tunnel syndrome
Peripheral nerve problems in your arms or legs
Guillain-Barré syndrome, a disease in which your immune system attacks the nerves in your legs and arms (WebMD)
How Do I Prepare for an EMG?
You don’t need to do anything special before the test. Doctors do recommend that on the morning of a test, you:
Bathe or shower, but don’t put on any lotions or moisturizers
Avoid caffeine and sugary beverages for at least 2 or 3 hours before a test
Don’t smoke before a test
You should also talk with your doctor about taking medications before a test. There may be certain medicines you should avoid taking until after the test.
If you have a pacemaker, you should tell your doctor before she/he schedules EMG.(WebMD)