Electromyography (EMG) and nerve conduction studies (NCS) are diagnostic testing procedures used to determine the location and severity of peripheral nerve or muscle problems. Examples include problems that might be caused by a “pinched” nerve, such as carpal tunnel syndrome; problems that affect generalized nerve function, such as diabetes; problems that affect the junction between the nerves and muscles, such as myasthenia gravis; or problems that affect the muscles, such as myositis. The results are used to help determine a diagnosis and to help create an appropriate plan of care.
Before the testing begins, the patient is asked about the problem, how it feels, how it affects function and when it started. This initial conversation is followed by a brief physical examination of strength, reflexes and sensation, which helps to determine how to proceed with testing.
During an EMG test, a small needle electrode is inserted into a muscle at the endpoint of the nerve in order to monitor the muscle activity. This is done to determine if there is loss or irritation of nerve or muscle fibers. The needles are very thin (about the size of acupuncture needles) and are less painful than a typical injection.
During an NCS test, surface electrodes, similar to those used with heart monitors, are taped onto the skin over the endpoints of the nerves. The nerves are stimulated with a mild electric shock that is similar to the static discharge from touching a doorknob on a cold day. This is done in order to determine blockage or distortion in the nerves’ ability to transmit electrical signals from one place to another along the course of the nerve.
Who is a good candidate for EMG/NCS?
Physicians typically refer patients who are experiencing any of the following:
- Sensory loss
- Odd sensations
- Limited mobility
- Loss of strength
- Loss of balance
- Loss of dexterity
Is there anything I need to do to prepare for an EMG/NCS session?
Wear loose-fitting clothing over the body part to be tested, wash all body parts and avoid the use of lotions and oils before the session. It is also important to report any medications you are currently taking.
How long does a session last?
A typical EMG/NCS session lasts about two hours.