A condition in which there is a disturbance of the normal electrical activity of the brain. Epilepsy affects about 1 in 200 people, and in about half those cases the malfunction is the result of a head injury, a birth injury or an infection. Sometimes a stroke or a tumor is responsible. In the other cases, the cause is unknown. Epilepsy is characterized by seizures. In grand mal seizures there is a fit of abnormal jerky movements followed by unconsciousness. The seizure usually lasts a couple of minutes. Petit mal seizures are less severe and are most often seen in children. During petit mal, the person seems to go into another, private world with only a little twitching or blinking, the state lasting only a few seconds. Epilepsy is diagnosed by the symptoms as well as ELECTROENCEPHALOGRAMS, X-rays and other tests. It may be successfully controlled with anticonvulsant drugs.