A patient’s guide to the Clinical Neurophysiology service: Nerve conduction and electromyography (muscle) studies

Nerve conduction studies (NCS) and electromyography (EMG) studies are carried out by a Consultant Clinical Neurophysiologist with a computer based NCS/EMG machine to help diagnose conditions or diseases that affect the function of nerves or muscles. The examination usually takes 30 minutes, with the patient sitting or lying on an examination couch.

Common types of neurophysiology studies:

• Nerve Conduction Studies (NCS): nerve responses to small and brief electrical pulses are measured with electrodes placed on the skin. The test feels slightly uncomfortable (like the feeling of static electricity). Common medical conditions where this test is used is in the diagnosis of entrapment neuropathies (e.g. carpal tunnel syndrome or ulnar neuropathy) or generalised neuropathies.
• Electromyography (EMG): in some patients it is important to measure muscle activity with a thin needle placed in the muscle through the skin. The EMG test is uncomfortable, but usually well tolerated (similar to a blood test). EMG is used to test if there is damage of the nerve supply to a muscle, such as from a lower back problem or a neuropathy or to test for muscle inflammation or degeneration (myopathy).
• Single Fibre EMG: a variation of the EMG test, but is used to help with the diagnosis of myasthenia gravis.

Why would I need NCS or EMG studies?

These tests are used in the diagnosis of a wide variety of problems that affect nerves or muscles. You would be advised to have these tests by your referring consultant if they suspect such a problem, particularly if there are symptoms of numbness, tingling, pain or unsteadiness or if there are muscle symptoms of weakness or fatigue.

There are no side effects from these investigations. You will be able to carry on as you would normally after these tests.