Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School


What Is It?

Epilepsy is a nervous system condition. It causes repeated, sudden, brief changes in the brain's electrical activity. These changes cause various types of symptoms.

Epileptic episodes are called seizures or convulsions. During a seizure, brain cells fire uncontrollably at up to four times their normal rate. Seizures temporarily affect the way a person behaves, moves, thinks or feels.

There are two main types of seizures:

  • A primary generalized seizure involves the entire brain.

  • A partial seizure begins in one brain area. It affects only part of the brain. However, a partial seizure can turn into a generalized seizure.

Many conditions can affect the brain and trigger epilepsy. These include:

  • Brain injury, either before or after birth

  • Brain tumors

  • Infections, especially meningitis and encephalitis

  • Genetic conditions

  • Abnormal blood vessels in the brain

  • Lead poisoning

In most people with epilepsy, the specific cause is unknown.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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