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February 7, 2012
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Electroencephalography (EEG)

Medical Author:
Diamond Vrocher III, MD
Coauthor:
Mark J Lowell, MD
Medical Editor:
Scott H Plantz, MD, FAAEM
Medical Editor:
Francisco Talavera, PharmD, PhD
Medical Editor:
James S Cohen, MD

Electroencephalography (EEG) Introduction

The electroencephalogram (EEG) is a measure of brain waves. It is a readily available test that provides evidence of how the brain functions over time.

  • The EEG is used in the evaluation of brain disorders. Most commonly it is used to show the type and location of the activity in the brain during a seizure. It also is used to evaluate people who are having problems associated with brain function. These problems might include confusion, coma, tumors, long-term difficulties with thinking or memory, or weakening of specific parts of the body (such as weakness associated with a stroke).


  • An EEG is also used to determine brain death. It may be used to prove that someone on life-support equipment has no chance of recovery.


  • Scientists first captured and recorded brain waves in dogs in 1912. By the 1950s the EEG was used commonly throughout the United States.

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Electroencephalography (EEG)

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Polycythemia can result from internal problems with the production of red blood cells. This is termed primary polycythemia....

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Read What Your Physician is Reading on Medscape

Normal EEG Variants »

The phrases "electroencephalogram (EEG) variant waves" or "normal EEG variants" refer to waves that are rare or unusual but not generally abnormal.

Read More on Medscape Reference »

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