Skip to main content

Electrodiagnostics (EMG/NCS)

St. Charles Hospital’s physiatrists are able to perform electrodiagnostic testing on both children and adults. Patients who require these tests are usually referred by a physician who would like assistance in diagnosing a nerve or muscle disorder.

Electrodiagnostics is a type of test that can help find the cause of a variety of conditions that are related to nerves or muscles.  These include weakness, pain, spasms, numbness and tingling. This test can also help identify the location of the problem, whether it is in the muscles themselves or if it originates in the spinal cord or nerves.  Physicians at St. Charles perform the test, interpret the results and send a detailed report to the referring physician

Electrodiagnostic tests are often subdivided into EMG and NCS:


EMG (electromyography) is a test used to measure the electrical activity of the muscles. A tiny needle is inserted into a muscle in order to stimulate and measure electrical activity. The small needle is inserted into several muscles to look at and listen to electrical signals that travel from the needle to the EMG machine. A new sterile needle is used for each patient and is discarded immediately after the test. Physicians test only the muscles necessary to determine where the problem occurs and then uses the information to identify what is causing the problem.


NCS (nerve conduction study), measures the intensity and speed of electrical signals that travel along the nerves, and the amount of time it takes for a response to these signals. This test requires that electrodes be placed on the skin and measurements taken as an electrical current travels between them. The test demonstrates how well the body’s electrical signals travel to a nerve. This is done by applying small electrical shocks to the nerve and recording how the nerve works. The shocks cause a brief, mild, tingling sensation. The physician may test several nerves in order to identify what is the cause of the problem.

EMG and NCS tests generally take 30 to 90 minutes to complete. There is no need for patients to restrict normal activities, such as eating, driving and exercising, before or after the test.

At St. Charles, electrodiadnostic testing is perform by our physiatrists. Learn more about our physiatrist at St. Charles by clicking HERE or call (631) 474-6797 for an appointment.