What is it and why do I need one?
When muscles are sore or weak and you don’t know why, there are a couple of tests that can help give you answers.
One is electromyography (EMG). The other is a nerve conduction study (NCS). They are often done at the same time.
Your doctor can use the results of these tests to figure out whether you have a muscular problem or a nerve problem
EMG is a diagnostic procedure to assess the health of muscles and the nerve cells that control them (motor neurons). EMG results can reveal nerve dysfunction, muscle dysfunction or problems with nerve-to-muscle signal transmission. Motor neurons transmit electrical signals that cause muscles to contract. An EMG uses tiny devices called electrodes to translate these signals into graphs, sounds or numerical values that are then interpreted by a specialist. During a needle EMG, a needle electrode inserted directly into a muscle records the electrical activity in that muscle. The NCS, another part of an EMG, uses electrode stickers applied to the skin(surface electrodes) to measure the speed and strength of signals traveling between two or more points.
Your doctor may order an EMG if you have signs or symptoms that may indicate a nerve or muscle disorder. Such symptoms may include:
- Muscle weakness
- Muscle pain or cramping
- Certain types of limb pain
EMG results are often necessary to help diagnose or rule out a number of conditions such as:
- Muscle disorders, such as muscular dystrophy or polymyositis
- Diseases affecting the connection between the nerve and the muscle, such as myasthenia gravis
- Disorders of nerves outside the spinal cord (peripheral nerves), such as carpal tunnel syndrome or peripheral neuropathies
- Disorders that affect the motor neurons in the brain or spinal cord, such as amyotrophic lateral sclerosis or polio
- Disorders that affect the nerve root, such as a herniated disk in the spine
Although electromyography is usually painless, the insertion of electrodes into muscles during the procedure sometimes causes slight pain or discomfort to patients. It is also normal for patients to feel sore and tender at the site of the tested muscle for a few days after the test.
The health professional who conducts an electromyography test is known as a neurologist, a nervous system specialist. A technologist may also perform some parts of the test. The test is performed to measure the electrical activity in response to a nerve’s stimulation of the muscle.
A neurologist explains the procedure to the patient and allows the patient to ask any questions regarding the test.