Nerve conduction velocity (NCV) test is an electrical test used to detect true nerve disorders (such as neuropathy) or conditions whereby muscles are affected by nerve injury (such as carpal tunnel syndrome). It is often done at the same time as an electromyogram (EMG) in order to exclude or detect muscle conditions.
During NCV tests, the nerve is electrically stimulated while a second surface patch electrode (like one used for an electrocardiogram) placed on the skin over the nerve at various locations detects the electrical impulse 'downstream' from the first.
One electrode stimulates the nerve with a very mild electrical impulse and 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 speed of impulse transmission (nerve conduction velocity). A decreased speed of transmission indicates nerve disease.
For NCV test, a normal body temperature must be maintained, because low body temperatures slow nerve conduction.