EMG (electromyography) and NCS (nerve conduction study) are two tests that can be used to diagnose muscle soreness and weakness. They help determine whether the underlying cause of the problem is muscle related or nerve related.

What is an EMG/NCS and how does it work?

The test involves two parts, the NCS and EMG. NCS stands for Nerve Conduction Studies. In this portion of the test, a number of sticky electrodes are placed on the hands or feet. To test the nerve, a small electrical pulse is given to the skin.

EMG stands for Electromyography. In this portion of the test, a fine needle is inserted into a muscle. Recordings are taken with the muscle relaxed and when the muscle is tensed.

What does this study look for?

The NCS portion of the test is used to find out how the nerves in your arms and/or legs are working. The EMG portion of the test records the electrical activity that is naturally produced in your muscles.

What are the indications for this study? (Why do we order it?)

This test is used to evaluate tingling, numbness, muscle weakness, pain or cramping. It is used to identify conditions such as:

  • Muscle disorders, such as muscular dystrophy or polymyositis
  • Diseases affecting the connection between the nerve and the muscle
  • 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 a herniated disc

What are the benefits?

EMG/NCS is one of the only tests which directly assesses the proper functioning of the body’s nervous system.

What are the complications or side effects of this study?

During the EMG portion of the exam, the needle may cause a small amount of bleeding, and there is a small chance of localized bruising.