Electrodiagnosic Studies: Non-surgical Procedure
Evaluating Muscles and Nerve Root Disease
Electromyography(EMG) and Nerve Conduction Velocity (NCV) studies are structured to evaluate for injury or disease of muscle, nerve roots, and peripheral nerves. They assess the condition of the nerves from the face, spine, and extremities, including the hand and foot. These studies are usually completed jointly and are typically carried out as a workup for complaints of tingling, numbness, weakness, or pain.
Video: Nerve Conduction Velocity (NCV) Procedure
Different radiographic or imaging tests that assess structure, such as an X-ray or MRI, electrodiagnostic studies evaluate physiology or biochemical function.Thoughout the nerve conduction segment of the study, mild electrical impulses are sent along the course of a nerve in a limb. The electrical impulse which feels much like that of a static electric shock will make the muscles in your arm and leg contract.
Electrodes much like EKG patches are positioned along the known course of the nerve. The nerve must transmit the signal along its course when stimulated. An electrode set further along the limb captures the signal as it passes by. The signal will transmit faster and stronger in a healthy nerve.
The needle EMG portion of the analysis includes the insertion of very thin pin electrodes into the skin. The electrode is moved around somewhat after its insertion. Concentric and Monopolar are two types of electrodes used for EMG studies. Monopolar electrodes are designed for minimal discomfort and pain.
Muscles typically receive steady electrical signals from healthy nerves, which then "broadcast" their own healthy electrical signals. When inserted into a muscle, the EMG electrodes log the electrical signal created by the muscle. The muscle signals that are broadcast back through the EMG electrode will show the irregularity if the muscle is diseased or injured, or if it does not receive adequate signals from its nerve supply. Because the EMG and NCV study can be unpleasant, many patients come to the test apprehensively. Nearly all leave feeling they worried for nothing. Equally significant, many are grateful that the CAUSE of their numbness, weakness, or pain has been found and can now be more efficiently treated.
Electrodiagnosic Studies Procedure
Your physician may order electrodiagnostic studies to further evaluate your muscles and nerves if you are experiencing persistent numbness and tingling or progressive weakness in your extremities. Dissimilar to an x-ray or blood test, electrodiagnostic studies are conducted by a physician with specialized training, usually a physiatrist or neurologist and can take around 60-90 minutes depending on the scrupulousness of the exam. Nerve conduction studies (NCS) and needle electromyography (EMG) are the two electrodiagnostic procedures most commonly performed.
Nerve conduction studies are used to evaluate the health of a nerve. In this study, small metal or disposable electrodes are taped to the skin and a short electric stimulus is applied to a portion of a nerve. Patients describe this as a slight shock feeling. The physician is able to analyze how fast an electric impulse is traveling along the nerve with the aid of modern electrodiagnostic equipment. An absent or delayed reaction points to nerve damage.
Video: Electrodiagnosic Test (EMG)
Evaluating Muscles and Nerve Root Disease
Needle EMG exam is used to assess the health of a muscle after nerve conduction studies is performed. When doing this test, the physician inserts a disposable fine needle electrode through the skin into selected muscles. Some temporary discomfort during needle insertion may be felt by the patient. The needle has a microscopic electrode that can observe both normal and abnormal muscle discharges. By looking at a screen and listening for specific sounds on a speaker, the physician analyzes these discharges.
Electrodiagnostic testing is exceptionally safe. A patient may undergo some brief discomfort during or after the exam but there are no permanent after-effects. Patients can eat before the exam and should take their normal medication. There are no activity restrictions before or after the test. It is best to not apply any lotions or creams to the skin on the day of the exam as this can prevent the electrode from sticking to the skin.