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. 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.

muscle stimulation, testingAs you relax and contract the muscle, the electrical impulses are recorded on an oscilloscope.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)

Your neurologist and/or physiatrist will analyze the results of the test(s) and send a written report to your referring doctor.

Before EMG or NCV tell your doctor if:

  • You take blood-thinning medication
  • You regularly take aspirin
  • Have a bleeding disorder

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.

Preparing for EMG or NCV

  • Avoid skin lotion or cream on the areas to be tested
  • During the test, you may be instructed to sit and/or lay down

EMG and NCV: Discomfort and Risks

  • EMG: You may feel discomfort when the needle electrodes are inserted.
  • NCV: You may feel startled when the electrical pulses are generated.
  • After EMG: The muscle(s) tested may feel sore, and you may have minor bleeding or bruising where the needle electrodes were inserted.
  • EMG risk: Small risk of infection where the needle electrodes were inserted.

EMG and NCV: Working Together to Reveal the Root Cause of Muscle and Nerve Pain
Electromyography (EMG) and nerve conduction velocity (NCV) may help your doctor successfully identify your muscle- and/or nerve-related spine pain. Once a diagnosis is made, you and your doctor can discuss your treatment options to reduce your pain and restore function.

Updated on: 05/15/18
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Neurological Exams for Neck and Back Pain: Nerve Deficits
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Neurological Exams for Neck and Back Pain: Nerve Deficits

A spine specialist may order specific neurological studies. These tests measure nerve performance.
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