Electromyography (EMG)

What is an EMG?

Electromyography (EMG) utilizes electrodes, devices that transmit or detect electrical signals, to evaluate muscle health and nerve cells known as motor neurons. EMG translates the electrical signals transmitted by motor neurons into graphs or numerical values, which can help diagnose muscle or nerve dysfunction or evaluate the degree of muscle injury.

What to Expect During an EMG

EMGs are relatively painless and pose few risks. You can expect this procedure to last between 30 and 60 minutes. During one form of EMG, a needle electrode is inserted into a muscle in order to control its electrical activity. An EMG may also be performed by using surface electrodes taped to your skin to stimulate your nerves in order to gauge the speed and strength of electronic signals. Both forms of EMG are routinely performed during the same test, but in some cases, only muscle testing or nerve conduction is performed.

Uses of EMG Imaging

Your doctor may order an EMG if you have signs or symptoms that may indicate a nerve or muscle disorder. Such symptoms may include:

• Tingling
• Numbness
• Muscle weakness
• Muscle pain or cramping
• Certain types of limb pain

Your doctor may order an EMG if you have signs or symptoms that may indicate a nerve or muscle disorder. Such symptoms may include:

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 do I prepare for an EMG?

The neurologist conducting the EMG will need to know if you have certain medical conditions. Tell the neurologist and other

EMG lab personnel if you:

• Have a pacemaker or any other electrical medical device
• Take blood-thinning medications
• Have hemophilia, a blood-clotting disorder that causes prolonged bleeding

Take a shower or bath shortly before your exam to remove oils from your skin. Don’t apply lotions or creams before the exam.

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