Electrodiagnostic testing is used to determine whether a patient has an injury or disorder of a nerve or muscle. The testing is usually conducted on a patient who has experienced muscle pain or cramping, or sensations of weakness, numbness or tingling. Conditions that can be diagnosed with the aid of electrodiagnostic testing include:
Electrodiagnostic testing actually involves two different tests:
For the NCS, the doctor stimulates a nerve with small electric shock by placing an electrode on the skin above the nerve. This test is done in two or more places along the nerve’s path. Data is recorded that shows the conduction velocity (the speed at which the electrical impulse travels through the nerve). If that speed is slower than typical readings, it suggests possible nerve damage.
For the EMG needle exam, the doctor lightly inserts very fine needles into a patient’s muscle (or several muscles). Connected to a computer, these needles record the electric impulses created by the body when the muscle is at rest and when the patient flexes the muscle. The physician then analyzes the recorded signals to determine whether there may be muscle or nerve damage. The EMG needles are so fine that there is rarely any bleeding during the test.