Nerve Conduction Studies (NCS) or Electroneurography
Nerve conduction studies (NCS) is a test of the speed of conduction of impulses through a nerve and also to look at the size and blockage in the nerve.
How the test is performed?
The nerve is stimulated, usually with surface electrodes, which are patch-like electrodes (similar to those used for ECG) placed on the skin over the nerve at various locations. One electrode stimulates the nerve with a very mild electrical impulse. The resulting electrical activity is recorded by the other electrodes. The distance between electrodes and the time it takes for electrical impulses to travel between electrodes are used to calculate the nerve conduction velocity. The amplitude and the shape of the nerve response is also important measures which helps to identify various type pathologies in the nerves and muscles.
How to prepare for the test:
Normal body temperature must be maintained (low body temperature slows nerve conduction and causes increase in the amplitude of the muscle response). Inform the department if you have any bleeding problems, have a pacemaker, have allergies or if you are taking any medicines like blood thinning agents (Warfarin, aspirin etc.). On the day of the test, take a shower to remove body oils and do not use body lotion
How the test will feel?
The impulse feels like an electric shock which is given in a controlled manner from an equipment which has built in safety devices. Depending on how strong the stimulus is, you will feel it to varying degrees, and it may be uncomfortable you. You should feel no pain once the test is finished. Often the nerve conduction test is followed by electromyography (EMG) which involves needles being placed into the muscle and you contracting that muscle. This can be uncomfortable during the test, and you may feel muscle soreness at the site of the needles afterwards as well.
When can I expect the results of the test?
The verbal results of the test can be provided to the patient at the conclusion of the test and the complete report ill be provided to the referring consultant within a weeks time.
Why the test is performed?
This test is used to diagnose nerve or muscle damage or destruction.
Normal Results or Values:
Nerve conduction velocity is related to the diameter of the nerve and the normal degree of myelination (the presence of a myelin sheath on the axon) of the nerve. Newborn infants have values that are approximately half that of adults, and adult values are normally reached by age 3 - 4.
What abnormal results mean:
Most often, abnormal results are caused by some sort of neuropathy (nerve damage or destruction) including:
- Demyelination (destruction of the myelin sheath)
- Conduction block (the impulse is blocked somewhere along the nerve pathway)
- Axonopathy (damage to the nerve axon)
Some of the associated diseases or conditions include:
- Carpal tunnel syndrome (Median nerve compression at the wrist)
- Ulnar nerve entrapment at the elbow or at the Guyon’s Canal
- Radial nerve dysfunction (Saturday night palsy)
- Tibial nerve dysfunction (LikeTarsal tunnel syndrome)
- Sciatic nerve dysfunction (Pyriformis Syndrome)
- Brachial plexopathy
- Traumatic injury to a nerve
- Common peroneal nerve dysfunction (Compression at the fibular head in knee
- Meralgia Paraesthetica (Entrpament or dysfunction of the lateral femoral cutaneous nerve of the thigh)
- Guillain-Barre syndrome
- Mononeuritis multiplex
- Femoral nerve dysfunction
- Alcoholic neuropathy
- Diabetic Neuropathy
- Nerve effects of uremia (from kidney failure)
- Diptheria
- Charcot-Marie-Tooth disease (hereditary)
- Chronic inflammatory polyneuropathy
- Distal median nerve dysfunction
- Friedrech’s ataxia
- Lambert-Eaton Syndrome
- Primary amyloid
- Secondary systemic amyloid
- Sensorimotor polyneuropathy
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