Electromyography (EMG)

What the test involves

The study usually has two parts. In the nerve conduction study, electrodes are placed on the skin over the affected area to measure the speed and strength of electrical signals between different points, showing how well the nerves communicate with the muscles.

In needle electromyography, a fine electrode is inserted into the muscle to record its electrical activity at rest and when contracted. The electrodes are removed at the end.

What it is used for

• Carpal tunnel syndrome and other nerve compressions
• Radiculopathy (involvement of a spinal nerve root)
• Polyneuropathies, such as diabetic polyneuropathy
• Myopathies and other neuromuscular diseases
• As part of the work-up of conditions such as myasthenia gravis or amyotrophic lateral sclerosis