Electromyography (EMG) and Nerve Conduction Velocity (NCV) Tests

Electromyography (EMG) and nerve conduction velocity (NCV) are electrodiagnostic tests that measure the electrical activity of muscles and nerves. These tests may be an important part of a spine patient’s work-up by their doctor. Besides back pain or neck pain, some patients with a spine-related problem report unexplained symptoms, numbness and/or tingling sensations, muscle cramping, or weakness in an extremity (eg, one or both arms, legs). EMG and NCV join forces to help get to the bottom of why those symptoms are occurring.

Your doctor may refer you to a neurologist and/or physiatrist for an EMG and NCV. Both tests are often performed during the same appointment. An EMG and NCV may be used to determine:

• If the problem is related to muscles or nerves
• The presence of nerve damage
• The cause of nerve damage
• Whether the damaged nerves are responding to treatment (if the patient is receiving treatment)

Electromyography (EMG): What It Is and What to Expect

EMG measures muscle response to nerve stimulation and evaluates electrical activity within selected muscle fibers. This test may help differentiate between a muscle disorder and a nerve disorder, which can help your doctor make an accurate diagnosis.

During an EMG, a thin needle electrode is inserted through your skin into a specific muscle. As you relax and contract the muscle, the electrical impulses are recorded on an oscilloscope, a device that displays the electrical impulses in a wave-like pattern. Additionally, the doctor may listen to the results through a speaker.

Nerve Conduction Velocity (NCV): What It Is and What to Expect

NCV measures the speed at which an electrical impulse travels along a nerve.

During an NCV, patch-like electrodes are applied to your skin in several places over the nerve to be tested. Low-level electricity is dispensed through the electrodes to stimulate the nerve. The amount of electricity is similar to a shock from static electricity. The velocity at which the electrical signal flows through the nerve is measured and displayed on a screen.