Electrodiagnostic testing, commonly referred to as EMG, involves two major components called needle electromyography (EMG) and nerve conduction studies (NCS}.
These tests record and analyze the electrical signals in muscles and nerves to help diagnose diseases or injuries that may be causing pain, numbness, or weakness.
Depending on the problem being evaluated, either or both types of testing can be performed at the same visit. The test typically lasts between 30 to 60 minutes.
The nerve conduction study measures the electrical conduction of nerves to diagnose peripheral nerve injuries or disorders.
Small electrical impulses are directed to the nerves being tested, and the signals are recorded with electrodes that are taped to the skin or placed on the fingers.
The impulses feel like a twinge or spasm, which some patients experience as a brief discomfort. This gives specific information about whether the nerve is functioning improperly, and can help to determine the anatomic location and severity of the problem.
The electromyography portion of testing measures the electrical activity of muscles directly by recording the electrical signals in the muscle through the tip of a very small needle.
The patient is instructed to relax and gently contract each muscle during the test to record information about muscle activity that can indicate the health of the muscle and the nerves that control the muscle. Some patients feel discomfort or pain from the needle that resolves shortly after the needle is removed.
What can it diagnose?
Electrodiagnostic testing gives information that aids in determining the diagnosis and prognosis of many conditions including entrapment neuropathies (such as carpal tunnel syndrome, or nerve root injuries in the spine (such as radiculopathies).
Less common conditions such as polyneuropathy, myopathies, and motor neuron diseases can also be detected.
What preparation is needed before the test?
Before your appointment, your doctor can tell you more specifically what to expect based on your specific condition.
On the day of testing, do no use oil, lotion or powder on your skin in the area that will be tested. Tell your doctor if you take a blood thinner