Nerve and muscle tests

What is this test?

The test has two parts, usually done one after the other.

• Nerve conduction study (NCV): small pads are placed on the skin, and mild electrical pulses measure how fast a signal travels along the nerve.
• Electromyography (EMG): a very thin solid needle, thinner than a blood-test needle, goes into the muscle and acts like an antenna to pick up its electrical activity. Nothing is injected through it.

What is it for?

It helps show whether a problem lies in a nerve or a muscle. A familiar example is carpal tunnel syndrome, pressure on a nerve at the wrist, which causes numb fingers and is usually worse at night. Doctors usually diagnose it from your story and an examination, and turn to a nerve test when they are unsure.

A normal result does not always mean there is no damage, because the test reflects the best-surviving nerve fibres. That is why the doctor reads the result alongside your examination.

How do I get ready?

• Do not use cream, lotion or perfume on your arms and legs on the day.
• Keep your hands and feet warm, because cold changes the result.
• Wear loose clothing.
• Tell us beforehand if you have a pacemaker, defibrillator or other implant.
• Tell us if you take a blood thinner, and do not stop it yourself.

Details are in the guide to nerve tests.

How does it feel and how long does it take?

Most patients find the test mildly uncomfortable. The pulses feel like the static shock you get from a metal handle after walking on carpet, and a muscle may twitch for a moment. The needle may be uncomfortable, especially when you tighten the muscle.

The muscle part usually takes 20 to 30 minutes, and with the nerve part the visit can take up to an hour.

After the test

Nothing special is needed and you can go back to your normal day. The needle site may be a little sore or bruised.