Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Epilepsy

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.