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A nerve conduction test is performed to detect injury in the nerve. This is done by measuring the velocity of electrical impulses passing through the nerves of an individual. The test involves the stimulation of nerves through electrode patches fixed to the individual’s skin.

A nerve conduction study involves the combination of two electrodes placed on the skin of individual above the nerves. The function of one electrode is to stimulate the nerve with minor electrical impulse and the other electrode is to record the electrical activity. The process is repeated for every nerve being tested. Velocity is calculated by calibrating the distance between two electrodes and the time duration taken by the impulse to travel amongst electrodes.

What is the difference between NCS and EMG?

Nerve conduction study (NCS) and Electromyography (EMG) are both conducted together to differentiate between nerve and muscle disorder. The problem related to the nerve can be detected by NCS. While the EMG nerve conduction study detects the response of muscle concerning the nerve’s stimulus.

What are they used for?

Electromyography (EMG) and nerve conduction, both are useful in the detection of muscle and nerve disorders. EMG checks the correctness of the nerve signal. When both are done simultaneously, they help to check whether the symptoms are due to nerve problem or muscle disorder.

What conditions do they diagnose or what can they detect?

These tests can diagnose the following disorders: 

Compressions neuropathies: Carpal tunnel syndrome, Ulnar nerve compression, Common peroneal nerve compression. 

Guillain-Barré syndrome: In this disorder, peripheral nervous system is impacted and attacked by the body’s immune system.

Charcot-Marie-Tooth disease: A hereditary condition where both motor and sensory nerves are affected. 

Herniated disk disease: In this disease, the fibrous cartilage around the disks of vertebrae collapses. This causes the gelatinous substance to breakout from the disk, which further pressurises the spinal cord. 

Chronic inflammatory polyneuropathy and neuropathy: This disorder can result from alcohol consumption or diabetes. 

Sciatic nerve problems: This can be due to the rupturing of the spinal disk, thereby adding pressure on nerve roots. 

How to prepare for the procedure

  • Inform the doctor if you are on medication and herbal supplements for any persisting disease.
  • Avoid the application of lotions and oils before the procedure.
  • Inform the doctor about any pacemaker if implanted. The NCV test can disturb the electronic impulse of the pacemaker.

How is the procedure performed?

This is an outpatient procedure conducted by a neurologist. When you arrive, you will have to get rid of jewellery, eyeglasses, hearing aids and clothes that can obstruct the procedure. After which, you will put on a surgical gown. 

The neurologist will locate the nerve. He or she will attach a recording electrode with the use of a special adhesive on the skin over the nerve. A stimulating record will be placed at a distance from the recording electrode. To stimulate the nerve, the stimulating electrode will send light and short electrical shocks. 

The patient may experience slight discomfort for a few seconds. The neurologist will observe the nerve stimulation and its response on the monitor. The neurologist will remove the adhesive after the procedure.

What are some of the risks and side effects?

Some of the risks associated with the procedure include:

  • Risks related to voltage, although the voltage is very low and does not cause any harmful effect
  • If you have a pacemaker or a defibrillator implanted, you will need to be careful and a maintain special precaution

What can impact the results?

Results are evaluated against standard velocities. Things that can impact the results include age, gender, pain, body temperature, part of the body tested or the place where the patient lives. If the velocity range falls outside the standard range, it means that the nerve is damaged or diseased. The nerve damage can be due to carpal tunnel syndrome, traumatic median nerve damage or acute inflammatory polyneuropathy.

Frequently asked questions

Is a nerve conduction study test painful?

The patient may feel minor uneasiness for few seconds when an impulse is passed. After the test, the patient will feel no pain.

What do nerve conduction study diagnose?

It detects how rapidly transmission of an electrical impulse moves down a nerve, thereby diagnosing injury in the nerve.

How long does a nerve conduction study test take?

The procedure takes 15 minutes to an hour. Time varies depending on the amount of nerves and muscles being tested.

Who performs nerve conduction studies?

Neurologists typically performs the nerve conduction study.