The examination can be helpful in evaluating the causes of numbness, tingling, pain, weakness, fatigue, and muscle cramping.
EMG (electromyography) and NCS (nerve conduction studies) test the electrical activity of your muscles and nerves. This allows the physicians to determine exactly where your injury is located. The tests may be done separately or together depending on your symptoms.
What is an
Electromyogram (EMG)?
An electromyogram (EMG) is a diagnostic study that has been used by health care providers for over 50 years. An EMG provides information about the integrity of the muscles and the nerves in your body. An EMG examination is typically ordered by a physician to evaluate for muscle or nerve damage as part of a medical workup.
Using a computer, monitor amplifier, loudspeaker, stimulator and high tech filters the examiner actually sees and hears how your muscles and nerves are working. As part of the EMG a very small needle is inserted into various muscles in the arm, leg, neck or back where you are having symptoms. In many cases the examination will include areas far from where you are having symptoms because nerves can be very long.
A clean new needle is used on each examination, and the needle is thrown out after the examination is complete. There is virtually no chance to catch any diseases from having an EMG. Also, because the needle used is sterilized, the chance of infection is minimal. An EMG is only one part of nerve testing; another part is called the nerve conduction study.
What is a
Nerve Conduction Study (NCS)?
A nerve conduction study (NCS) is one part of a comprehensive nerve and muscle diagnostic test. Like an EMG, a NCS is typically ordered by a physician to evaluate for muscle or nerve damage as part of a medical workup. Once again, the examiner uses a computer, monitor, amplifier, loudspeaker, stimulator and high tech filters to monitor the functioning nerves and muscles your body.
The examiner places small electrodes on your skin over muscles being tested in your arms or legs. The examiner then uses a stimulator to deliver a very small electrical current to your skin near nerves being tested, causing your nerves to fire. The electrical signals produced by nerves and muscles are picked up by the computer, and the information is interpreted by a physician specially trained in electrodiagnostic medicine. The stimulator only produces a very small shock that does not cause damage to your body. Many different motor and sensory nerves are typically evaluated.
Do I Need an
EMG/NCS?
When you have symptoms including radicular pain (pain radiating from the neck or back), numbness, weakness or tingling in an arm or leg, it is important to find out what is causing your symptoms. There are many possible causes for the above symptoms, and many cases resolve spontaneously on their own. However, if symptoms persist, an EMG/NCS is one way to assess muscle and nerve function and is often used with other tests such as MRI or CT scan that create images of the body.
COMMON PROBLEMS EDX STUDIES CAN DIAGNOSE:
- Pinched nerves at the:
- Wrist (Carpal Tunnel Syndrome)
- Elbow (ulnar palsy)
- Knee (foot drop)
- Neck (cervical radiculopathy)
- Back (lumbar radiculopathy)
- Polyneuropathy – diseases of the nerve fibers
- Myopathies – Muscle diseases
How Should I Prepare for an
EMG/NCS?
After showering on the day of your examination, do not use any creams, moisturizers or powders on your skin. If you have any bleeding disorders, let the examining physician know prior to testing. If you take blood thinners, even any aspirin or aspirin like medications let the examining physician know. If you have a pacemaker or other devices that are implanted in your body to deliver medications, let the examining physician know. Also, any recent fevers or chills may indicate current bodily infection and should be mentioned to the examining physician.
What Can I Expect on the
Day of the Test?
As mentioned earlier, the electrodiagnostic testing usually includes both electromyogram (EMG) and nerve conduction studies (NCS).
The EMG section includes a small sterilized needle being inserted in the muscles to be tested. There is some discomfort with needle insertion, but most tolerate the testing without difficulty. You may notice some bruising after the needle portion of the examination, ice to sore areas can help with discomfort and limit the bruising. Any time the skin is penetrated with a needle, there is a theoretical risk of infection developing.
The NCS portion of the examination includes a small stimulus applied near nerves to make them fire. In most cases a series of shocks are necessary to get the optimal response. Any discomfort is transient, and the stimulus is not strong enough to cause damage to the body.