An EMG measures the electrical activity in a muscle in response to stimulation. It is used in conjunction with a neurological exam to help physicians diagnose a wide range of problems, including:
- Nerve damage from disk compression in the neck or back
- Nerve compression from carpal tunnel syndrome
- Neuromuscular diseases such as amyotrophic lateral sclerosis (ALS), poliomyelitis, myasthenia gravis, and muscular dystrophy
- Peripheral neuropathy caused by conditions such as diabetes, pernicious anemia, and heavy metal toxicity
The test consists of two parts:
- In the nerve conduction study, electrodes are placed on the skin and a safe level of electrical stimulation is sent through the nerve, causing the muscles in your arm or leg to contract. The sensation you will feel is similar to a static electric shock. Patients wearing pacemakers are not at risk, since this current is not strong enough or close enough to the pacemaker to interfere with its operation.
- In the second part, the EMG, a tiny pin electrode is inserted under the surface of the skin into the muscle. Electrical stimulation will indicate if there is damage to a specific nerve, or if the problem involves the muscle itself.
This test is mildly uncomfortable, but is specially designed to not be painful. It will take between 30 to 60 minutes.
Preparing for your EMG
- Your arms and legs should be clean and free of lotions or creams.
- Meals and medication may be taken unless your physician advises otherwise.