Electromyography (EMG) and Nerve Conduction Studies (NCS) are special electronic tests to evaluate the function of muscles and nerves.

NCS are performed by applying electrodes over a nerve or muscle, usually in the hand or foot, and then stimulating a nerve (delivering tiny shocks) in different locations along its course.

EMGs are performed by inserting small needle electrodes into various muscles to assess their function. By using NCS and EMGs a more specific neuromuscular diagnosis can often be made, which can be helpful in directing therapy and establishing prognosis.

NCS and EMGs are useful in evaluating:
1. Conditions in which a single nerve is injured at a single location (for example carpal tunnel syndrome or a "pinched nerves" in the neck or lower back).

2. Diseases that involve all the nerves in the body (also called peripheral neuropathies)

3. Diseases that involve all the muscles in the body (also called myopathies)

4. Diseases that involve the junction between nerves and muscles (for example myasthenia gravis)