Neurophysiology

EMG (Electromyography) and NCS (Nerve Conduction Study)

Overview

Electromyography (EMG) is a diagnostic procedure to assess the health of muscles and the nerves that control them. EMG results can reveal nerve or muscle dysfunction or problems with nerve-to-muscle signal transmission.

Motor neurons transmit electrical signals that cause muscles to contract. During an EMG tiny needle electrodes are inserted directly into a muscle and record the electrical activity in that muscle. The signals recorded are displayed on a screen with sound and numerical data values that are then interpreted by a consultant.

A nerve conduction study is another part of the test and uses electrode stickers applied to the skin (surface electrodes) to measure the speed and strength of signals traveling between two or more points.

Why these tests are done

Your doctor may order an EMG if you have signs or symptoms that may indicate a nerve or muscle disorder. Such symptoms may include:

• Tingling
• Numbness
• Certain types of muscle or limb pain
• Muscle weakness

EMG results are often necessary to help to diagnose or rule out a number of conditions including:

• Disorders of peripheral nerves such as carpal tunnel syndrome or peripheral neuropathies
• Muscle disorders
• Diseases affecting the connection between the nerve and the muscle
• Disorders that affect the nerve root, such as a herniated disk in the spine

The test usually take between 30 minutes to one hour and is performed by a consultant neurophysiologist. A referral from a GP or consultant is required for these tests to be performed.