An electromyogram (EMG) measures the electrical activity in muscles, at rest and during contraction. Some patterns of electrical activity indicate a disease of the nerves or muscles.

Nerve conduction studies are often done along with an EMG. Nerve conduction studies measure how well and how fast the nerves can send electrical signals to the muscles. During this test, low-voltage electrical shocks are used to stimulate the nerves, which in turn stimulate the muscle. The test records the ability of the nerve to send the impulse to the muscle.

Abnormal results suggest a person may be suffering from a disease that damages the muscles or nerves.

EMG and nerve conduction studies can help diagnose diseases that damage muscle tissue, nerves, or the junctions between nerves and muscles, such as:

  • Amyotrophic lateral sclerosis (ALS)
  • Myasthenia Gravis (MG)
  • Peripheral neuropathies
  • Muscular dystrophy
  • Myositis

An EMG takes approximately 30 to 60 minutes, and a nerve conduction study can take anywhere from 15 minutes to one hour, depending on how many areas are being tested.