What is Electromyography?

Electromyography, or EMG, is a diagnostic procedure to assess the health of muscles and nerve cells that control the muscle (motor neurons).

Since motor neurons transmit electrical signals that cause the muscles to contract, the EMG utilizes electrodes to translate these signals into graphs, sounds, and numerical values to be interpreted by skilled specialists.

Another aspect of EMG involves needle electrodes, where a needle is inserted into a given muscle to record activity. From there, we record the spikes in electrical currents that occur during voluntary contractions and nerve stimulation, subsequently interpreting and reporting our findings to the patient. Normal, healthy muscle function should not produce activity when the muscle is at rest.

There is also an aspect of EMG, called “Nerve Conduction Study”, which uses electrodes taped to the skin (surface electrodes) to measure the speed and strength of the electrical signals.

What Will I Learn from an EMG?

EMG testing can reveal muscle dysfunction, nerve dysfunction or a breakdown in communication between the nerves and muscles. Your doctor may order an EMG if you are experiencing any of the following symptoms, which may indicate a nerve or muscle disorder:

  • Tingling
  • Numbness
  • Muscle Weakness
  • Muscle Pain or Cramping
  • Certain types of Limb Pain
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EMG Can Help Diagnose or Rule Out

  • Muscle Disorders, such as Muscular Dystrophy or Polymyositis.
  • Diseases affecting the connection between nerve and muscle, such as Myasthenia Gravis.
  • Peripheral Nerve Disorders: Carpal Tunnel Syndrome and Peripheral Neuropathies.
  • Disorders that affect the motor neurons in the brain or spinal cord: Amyotrophic Lateral Sclerosis and Polio.
  • Disorders that affect the nerve root, such as a Herniated Disk in the Spine
  • Ataxias
  • Chronic Pain
  • Congenital Myopathies
  • Fibromyalgia
  • Guillain-Barré Syndrome
  • Metabolic Myopathies
  • Mitochondrial Myopathies
  • Myotonias
  • Nerve Lesions
  • Radiculopathies
  • Spinal Muscular Atrophy

What Can You Expect

The EMG test can take up to 2 hours. Both the technician and neurologist are present in the room. The technician adheres surface electrodes to various places on your skin, while the neurologist inserts needle electrodes at different locations.

The electrodes emit a small electrical current that feels much like a twinge or spasm. Some discomfort may occur until the needle is removed. During the needle EMG, the neurologist will ascertain the amount of activity occurring at different stages, such as resting, contracting the muscle, or changing positions.

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Take a bath or shower before your EMG appointment to remove oils from the skin, but avoid fragrances or lotions.


The risks of EMG testing is minimal. You may experience temporary minor bruising or tenderness. There is a slight chance of bleeding, infection, or nerve injury at the insertion site of the needle, but complications are rare. Be sure to contact your primary care doctor if side effects persist.


Be sure to alert your Neurologist and the EMG technician if:

  • You have a pacemaker or other electrical medical device.
  • You have hemophilia.
  • You take blood thinners.

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