Electromyogram (EMG) and Nerve Conduction Studies

EMG (Electromyography), Nerve Conduction Studies

Results

An electromyogram (EMG) measures the electrical activity of muscles at rest and during contraction. Nerve conduction studies measure how well and how fast the nerves can send electrical signals. Your doctor may be able to tell you about some of the results right after the tests. A full report may take 2 to 3 days.

Electromyogram (EMG) and nerve conduction studies

Normal:	The EMG recording shows no electrical activity when the muscle is at rest. There is a smooth, wavy line on the recording with each muscle contraction.
	The nerve conduction studies show that the nerves transmit electrical impulses to the muscles or along the sensory nerves at normal speeds (conduction velocities). Sensory nerves allow the brain to feel pain, touch, temperature, and vibration. Different nerves have different normal conduction velocities. Nerve conduction velocities generally get slower as a person gets older.
Abnormal:	Electrical activity in a muscle at rest shows that there may be a problem with the nerve supply to the muscle. Abnormal wave lines when a muscle contracts may mean a muscle or nerve disorder, such as amyotrophic lateral sclerosis (ALS), post-polio syndrome, inflammation, or other muscle problems.
	In nerve conduction studies, the speed of nerve impulses (conduction velocity) may be slower than what is normal for that nerve. Slower conduction velocities may be caused by injury to a nerve (such as carpal tunnel syndrome) or group of nerves (such as Guillain-Barré syndrome or post-polio syndrome). Nerve conduction velocities generally get slower as a person gets older.

The results from EMG and nerve conduction studies are used along with your history, symptoms, physical and neurological examinations, and the results of other tests to help your doctor find out what the problem is or to see how a disease is changing.

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Author:	Monica Rhodes	Last Updated: July 29, 2008
Medical Review:	Anne C. Poinier, MD - Internal Medicine Colin Chalk, MD, CM, FRCPC - Neurology
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