Electromyography

Overview of Electromyography (EMG)

Electromyography (EMG) is a common diagnostic test used to evaluate how well muscles and nerves are working. EMG, sometimes used in conjunction with nerve conduction studies, involves studying the movement of muscles and nerves using special equipment. It measures the electrical activity of a muscle in response to a nerve's stimulation of it.

Preparation for an EMG

Before every EMG, your doctor will go over the procedure with you. Depending on the type of test, you may have to go through the following steps:

• Remove all metal jewelry, earrings, and piercings.
• Wear a pair of shorts, if you are having a muscle test.
• Make sure to tell your doctor if you are taking any medications, such as blood thinners, or if you have a pacemaker.
• If you are having a nerve conduction study, make sure your doctor knows if you are sensitive to temperature extremes because the electrodes used in the test can become hot.

Types of EMG Tests

EMG tests can measure muscle activity, as well as nerve function. Depending on the issue being evaluated, there are two types of EMG tests that may be ordered:

• Nerve conduction studies are used to measure the speed and strength of the signals sent through a nerve. During a nerve conduction study, electrodes are often placed on the skin over a muscle. The electrodes will send an electric current to the nerve, which will then cause the muscle to contract. The results of the test will tell the doctor how the nerve is functioning.
• Muscle testing is used to measure the electrical activity of a muscle at rest and during contraction. During this test, a doctor or technician will insert a fine needle electrode into the muscle being tested. The results of the test will tell the doctor if the muscle is healthy, if there is any evidence of muscle or nerve damage, and if the muscle is responding appropriately to the nerve's stimulation.

Risks of EMG

EMG tests are generally safe and pose very little risk to the patient. The most common risks associated with the procedure are:

• Discomfort from the needles used to measure the electrical activity of the muscle.
• Infection at the site of the injection.
• Bruising at the site of the injection.
• Allergic reaction to the dye or lubricant used with the needles.

Why is an EMG Performed?

EMG tests are typically ordered by a doctor when a patient has symptoms that may be related to a nerve or muscle disorder. An EMG can help the doctor diagnose a number of conditions, including:

• Nerve or muscle damage due to trauma, disease, or congenital defects.
• Nerve or muscle disorders, such as muscular dystrophy or multiple sclerosis.
• Nerve or muscle pain.
• Carpal tunnel syndrome.
• Diabetic neuropathy.
• Parkinson's disease.
• Spinal cord injuries.
• Myasthenia gravis.
• Amyotrophic lateral sclerosis (ALS or Lou Gehrig's Disease).

When is an EMG Performed?

EMG tests are usually performed when a patient is experiencing symptoms that may be related to a nerve or muscle disorder. The test is often ordered when other tests, such as an MRI or CT scan, have failed to reveal the cause of the symptoms. It can also be used to monitor the progress of a condition over time.