What is it?
Electromyography is a test that assesses the health of the muscles and the nerves controlling the muscles.
- Concentric Needle (Mono / Bipolar) EMG
- Single Fiber EMG
- Macro EMG
- Scanning EMG
- Surface EMG
Why it is done :
EMG is used when people have symptoms of weakness and examination shows impaired muscle strength. It can help to differentiate various causes of weakness, pain and numbness primary muscle conditions from neurologic disorders among others.
EMG results are often necessary to help diagnose or rule out a number of conditions such as:
- Muscle disorders, such as muscular dystrophy or polymyositis
- Diseases affecting the connection between the nerve and the muscle, such as myasthenia gravis
- Disorders of nerves outside the spinal cord (peripheral nerves), such as carpal tunnel syndrome or peripheral neuropathies
- Disorders that affect the motor neurons in the brain or spinal cord, such as amyotrophic lateral sclerosis or polio
- Disorders that affect the nerve root, such as a herniated disk in the spine
How to prepare?
No special preparation is usually necessary. To ensure accurate readings, patient should avoid using creams or lotions on the day of the test.
How it is done:
- A needle electrode is inserted through the skin into the muscle. The electrical activity /signal detected by this electrode is displayed on a monitor, and may be heard through a speaker.
- After placement of the electrodes, subject is asked to contract the muscle (for example, bending the arm).
- The Presence, Size, shape of the wave form of the Action Potential observed on the monitor provides information about the ability of the muscle to respond when called for.
How long will it take?
Electromyography tests may take from 15 minutes to 1 hour or more, depending on how many muscles and nerves are studied.