EMG and Nerve Conduction
Your nervous system uses electrical energy to carry messages smoothly along motor nerves to muscles and along sensory nerves to the brain. Damage to the nervous system can affect how well nerves send these messages.
About Electromyography (EMG) Testing
The EMG test records the electrical activity of muscles. An electrode, a tiny needle, is inserted into one muscle at a time to record its electrical activity. It records activity during the insertion, while the muscle is at rest and while the muscle contracts. Your examiner will determine how many muscles need to be tested depending upon your symptoms.
Nerve Conduction Testing
Nerve Conduction Testing usually accompanies an EMG. The test measures the velocity (speed) of electrical signals along a nerve, recording how well electrical impulses travel along motor and sensory nerves.
The nerve conduction study is performed by placing surface electrodes on your skin over nerves in the arms and/or legs. The electrodes are used to stimulate the nerves and then record the conduction of the electrical signal as it travels along the nerve to a specific point. When the stimulating electrode sends the small electrical charge along the nerve, you may feel a tingle, but this is not harmful. Your examiner will determine how many nerves need to be tested depending upon your symptoms.
Measuring the electrical activity in muscles and nerves with EMG and nerve conduction testing can aid in the diagnosis of peripheral nerve disease or trauma (peripheral neuropathies), nerve entrapment conditions (such as carpal tunnel syndrome), muscle disorders (myopathies), irritation or injury of the spinal nerve roots (radiculopathies), and several disorders, such as Guillain-Barre syndrome, myasthenia gravis, and post-polio syndrome.