A nerve conduction velocity (NCV) involves activating nerves electrically with small safe pulses over several points on the skin, usually on the limbs, and measuring the responses obtained. Usually, the response or signal is measured from the nerve itself or from a muscle supplied by the nerve being activated. This gives information about the state of health of the nerve, muscle and neuromuscular junction (the portion responsible for communication between the nerve and muscle).
Electromyography (also known as needle EMG) involves the measuring of electrical activity within muscles by way of a needle electrode. Muscles are electrically active organs, and the signals and patterns of signals can lend additional information regarding the state of the muscle as well as the nerve supplying it.
Before the test, the person doing the test may take a short history and make a physical/neurological examination.
The NCV procedure is usually very safe and is non-invasive. Firstly, you will be told how to position yourself and the skin area will be prepared. Then some electrodes will be attached to your skin and you will be forewarned when to expect the stimulation. Many people are understandably anxious about the intensities of the small safe electrical pulses that are passed via the skin, but usually relax quickly when they know what to expect. It is fairly important that you remain relaxed for the recordings to minimise the 'noise' (interference) in the recordings from excessive muscular activity.
Here, a small needle is inserted through the skin into a muscle belly. Sterilisation of the skin and a local anaesthetic is not generally required. Usually the consultation and procedure takes about 30-45 minutes in all. More complicated assessments may demand more time.
There's a small risk of bleeding, infection and nerve injury where a needle electrode is inserted.