2. What is a nerve conduction velocity test?
A nerve conduction velocity (NCV) test — also called a nerve conduction study
(NCS) — measures how fast an electrical impulse moves through your nerve.
NCV can identify nerve damage.
During the test, your nerve is stimulated, usually with electrode patches
attached to your skin. Two electrodes are placed on the skin over your nerve.
One electrode stimulates your nerve with a very mild electrical impulse. The
other electrode records it. The resulting electrical activity is recorded by another
electrode. This is repeated for each nerve being tested.
The speed is then calculated by measuring the distance between electrodes and
the time it takes for electrical impulses to travel between electrodes.
A related test that may be done is an electromyography (EMG). This measures
the electrical activity in your muscles. It is often done at the same time as an
NCV. Both tests help find the presence, location, and extent of diseases that
damage the nerves and muscles.
3. Why might I need a nerve conduction velocity test?
NCV is often used along with an EMG to tell the difference between a nerve disorder and a
muscle disorder. NCV detects a problem with the nerve, whereas an EMG detects whether
the muscle is working properly in response to the nerve's stimulus.
Diseases or conditions that may be checked with NCV include:
•Guillain-Barré syndrome. A condition in which the body's immune system attacks part
the peripheral nervous system. The first symptoms may include weakness or a tingling
sensation in the legs.
•Carpal tunnel syndrome. A condition in which the median nerve, which runs from the
forearm into the hand, becomes pressed or squeezed at the wrist by enlarged tendons or
ligaments. This causes pain and numbness in the fingers.
4. •Charcot-Marie-Tooth disease. An inherited neurological condition that affects both the motor
and sensory nerves. It causes weakness of the foot and lower leg muscles.
•Herniated disk disease. This condition occurs when the fibrous cartilage that surrounds the
disks of your vertebrae breaks down. The center of each disk, which contains a gelatinous
substance, is forced outward. This places pressure on a spinal nerve and causes pain and
damage to the nerve.
•Chronic inflammatory polyneuropathy and neuropathy. These are conditions resulting from
diabetes or alcoholism. Symptoms may include numbness or tingling in a single nerve or many
nerves at the same time.
•Sciatic nerve problems. There are many causes of sciatic nerve problems. The most common
bulging or ruptured spinal disk that presses against the roots of the nerve leading to the sciatic
nerve. Pain, tingling, or numbness often result.
Nerve conduction studies may also be done to find the cause of symptoms, such as numbness,
tingling, and continuous pain.
5. What are the risks of NCV tests?
The voltage of the electrical pulses used during an NCV is
considered very low.
Risks depend on your specific medical condition. Be sure
to discuss any concerns with your healthcare provider
before the procedure.
Certain factors or conditions may interfere with the results
of NCV tests. This includes damage to the spinal cord,
severe pain before the test, and body temperature.
6. How do I get ready for an NCV test?
•Your healthcare provider will explain the procedure and you can ask questions.
•You will be asked to sign a consent form that gives your permission to do the procedure.
Read the form carefully and ask questions if something is not clear.
•Generally, you will not need to fast or get sedation before the procedure.
•Normal body temperature must be maintained before and during the procedure, as low
body temperature slows nerve conduction.
•Tell your healthcare provider of all medicines (prescription and over-the-counter) and herbal
supplements that you take.
•Dress in clothes that allow access to the area to be tested or that are easily removed.
•Stop using lotions or oils on your skin for a few days before your procedure.
•Based on your medical condition, your healthcare provider may request other preparation.
7. What happens during the NCV test?
An NCV procedure may be done on an outpatient basis, or as part of your stay in a
hospital. Procedures may vary depending on your condition and your doctor's
practices.
The NCV is done by a neurologist. This is a doctor who specializes in brain and nerve
disorders. A technologist may also do some parts of the test.
Generally, an NCV procedure follows this process:
1.You will be asked to remove any clothing, jewelry, hairpins, eyeglasses, hearing aids,
or other metal objects that may interfere with the procedure.
2.If you are asked to remove clothing, you will be given a gown to wear.
3.You will be asked to sit or lie down for the test.
4.A neurologist will locate the nerve(s) to be studied.
5.A healthcare provider will attach a recording electrode to the skin over your nerve,
using a special paste. He or she will then place a stimulating electrode away from the
recording electrode, at a known distance.
6.A mild and brief electrical shock, given through the stimulating electrode, will
stimulate your nerve.
7.You may experience minor discomfort for a few seconds.
8.The stimulation of the nerve and the response will be displayed on a monitor.
8. Scope
This guideline is intended to be used by medical professionals
to assess the appropriateness of nerve conduction studies in
the diagnosis and treatment of various neurological disorders.
It will address treatment modalities, adjudication policy,
documentation required, and provide relevant CPT and ICD-10
codes.
9. Introduction
A nerve conduction study (NCS) is a medical diagnostic test
commonly used to evaluate the function, especially the ability
of electrical conduction, of the motor and sensory nerves of
the human body. These tests may be performed by medical
specialists such as clinical neurophysiologists, physical
therapists,chiropractors, physiatrists (physical medicine and
rehabilitation physicians), and neurologists who subspecialize
in electrodiagnostic medicine.
10. Nerve conduction studies are used mainly for evaluation of
paresthesias (numbness, tingling, burning) and/or weakness of
the arms and legs. The type of study required is dependent in
part by the symptoms presented. A physical exam and
thorough history also help to direct the investigation. Some of
the common disorders that can be diagnosed by nerve
conduction studies are:
• Carpal tunnel syndrome
• Cubital Tunnel Syndrome
• Guillain–Barré syndrome
• Guyon's canal syndrome
• Peripheral neuropathy
• Peroneal neuropathy
• Spinal disc herniation
• Tarsal Tunnel Syndrome
• Ulnar neuropathy
11. Treatment Modalities
1. Conservative: Conservative treatment for conditions
diagnosed via NCS may include physical therapy, pain
management, lifestyle modifications, and medication
management.
2. Surgical: Surgical interventions may be required for
conditions that are severe, progressing rapidly, or not
responsive to conservative management. The nature of the
surgery will depend on the specific condition.
12. Adjudication Policy
1. Eligibility/Coverage Criteria:
They are used clinically in four major ways:
• Diagnose focal and generalized disorders of peripheral nerves
• Aid in the differentiation of primary nerve and muscle
disorders (although NCS itself evaluates nerve and not muscle)
• Classify peripheral nerve conduction abnormalities due to
axonal degeneration, demyelination, and conduction block
• Prognosticate regarding clinical course and efficacy of
treatment
13. • NCS may also be helpful in determining therapies, such as
when to do surgery in the carpal tunnel syndrome or when to
use immunosuppressive therapy in polyneuropathies.
2. Non-Coverage: NCS is not covered when performed for
screening purposes in asymptomatic patients or when the
diagnosis can be made clinically without the need for NCS.
3. Documentation required: Documentation supporting the
medical necessity of the NCS should include:
• detailed medical history,
• physical examination findings,
• a clear explanation of how the NCS results will influence the
treatment plan.
14. Additional Notes
It is important to note that NCS should not be performed in
isolation but should be combined with a complete clinical
evaluation. In addition, the test should be performed and
interpreted by trained and experienced professionals to ensure
accuracy.
Related CPT and ICD 10 codes
• CPT codes: 95860-95864, 95867-95870, 95885-95887.
• ICD-10 codes: G00-G99 (Nervous System), M79.2 (Neuralgia
and neuritis, unspecified), G56 (Mononeuropathies of upper
limb), G57 (Mononeuropathies of lower limb).
