Epilepsy is a neurological condition that makes people susceptible to seizures. It occurs in about one out of every 200 people. A single seizure is not necessarily epilepsy, but a tendency for recurrent seizures is. The term "seizure" is an abnormal spasm, convulsion, or change in sensation, awareness, or behavior brought about by a brief electrical disturbance in the brain.

Seizures vary from a momentary disruption of the senses, to short periods of unconsciousness or staring spells, to convulsions. Some people have just one type of seizure. Others have more than one type (see Types of Seizures for more information). Usually, no specific cause for epilepsy is identified. However in some cases a specific condition that seems to cause the tendency for the abnormal electrical circuits that cause seizures to occur is found. These include:

• Inherited (runs in families)
• Head injury (recent or prior)
• Stroke (recent or prior)
• Brain vascular malformations
• Brain tumor
• Brain infection, such as meningitis or encephalitis.
• Alzheimer's disease.
• Alcohol withdrawal
• Drug abuse (especially amphetamines or cocaine) or withdrawal (especially barbiturates)

Epilepsy is generally not the kind of condition that gets worse with time. Most adults who have it can expect to live a normal life span.