A seizure is a sudden surge of electrical activity in the brain that usually affects how a person feels or acts for a short time. Seizures are not a disease in themselves. Instead, they are a symptom of many different disorders that can affect the brain. Some seizures can hardly be noticed, while others are totally disabling.

The seizures in epilepsy may be related to a brain injury or a family tendency, but often the cause is completely unknown. The word "epilepsy" does not indicate anything about the cause or severity of the person's seizures.

If I have one seizure, does that mean I will get epilepsy?

About half of the people who have one seizure without a clear cause will have another one, usually within 6 months. You are twice as likely to have another seizure if you have a known brain injury or other type of brain abnormality. If you do have two seizures, there's about an 80% chance that you'll have more.

If your first seizure occurred at the time of an injury or infection in the brain, you are more likely to develop epilepsy than if you had not had a seizure in that situation.

More seizures are also likely if your doctor finds abnormalities on a neurological examination; a set of tests of the functioning of your nervous system that is performed in the doctor's office.

Another thing that can help your doctor predict whether you will have more seizures is an EEG, electroencephalogram (e-LEK-tro-en-SEF-uh-LOG-ram), a test in which wires attached to your scalp record your brain waves. Certain patterns on the EEG are typical of epilepsy. If your brain waves show patterns of that type, you are about twice as likely to develop epilepsy as someone who does not have those patterns.

Topic Editor: Steven C. Schachter, M.D.
Last Reviewed:11/20/06

Example of an Electroencephalogram

Normal Adult Background

Primary Generalized Epilepsy

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