epilepsy

The Columbia Encyclopedia, 6th ed.

epilepsy

epilepsy, a chronic disorder of cerebral function characterized by periodic convulsive seizures. There are many conditions that have epileptic seizures. Sudden discharge of excess electrical activity, which can be either generalized (involving many areas of cells in the brain) or focal, also known as partial (involving one area of cells in the brain), initiates the epileptic seizure. Generalized seizures are classified as tonic-clonic (grand mal), in which there is loss of consciousness and involuntary contraction of all the muscles of the body, lasting a few minutes; or absence (petit mal), in which there is clouding of the consciousness for about 1 to 30 sec and no falling, with as many as 100 attacks occurring daily. Partial seizures include Jacksonian epilepsy, characterized by jerking in the hand and face on the side opposite the brain activity; and psychomotor seizures, in which there may be localized convulsion with no loss of consciousness, as well as incoherent speech and various involuntary movements of the body. Often these are accompanied by a warning cluster of signs and symptoms called an aura. First aid, such as cushioning the head, is used to prevent the person from self-inflicted injuries during seizures.

The cause is unknown in over half the cases of epilepsy, especially in those with onset under age 20. Predisposing factors in other cases include familial history, head injury, alcohol withdrawal, infections (such as meningitis or by pork tapeworm larvae), and abnormalities (such as tumors) of the brain.

The recording of brain waves by electroencephalography is an important diagnostic test for epilepsy. Other diagnostic technologies include CAT scan and magnetic resonance imaging (MRI). Standard treatment of epilepsy is with antiseizure drugs (also known as anti-epileptic and anticonvulsive drugs), including carbamazepine, phenytoin, valproic acid, and others; proper treatment requires a careful analysis of seizure motor activity, anatomical cause, precipitating factors, age of onset of the disorder, severity, daily rhythms, and prognosis. Roughly 70% of persons with epilepsy are successfully treated with drugs, and many people with the disease lead normal lives. Repeated seizures that lead to unconsciousness, however, appear to be associated with damage to the hippocampus in the brain and sudden unexpected death.

Some cases of childhood epilepsy (which is often eventually outgrown) have been successfully treated with surgery or a very high-fat "ketogenic" diet. The diet results in a natural buildup of ketones in the body, which appear to inhibit the seizures. A number of different surgical procedures may be used if medication does not control the seizures; the procedures vary according to the focus of the seizure in the brain, and surgery is not always appropriate. If a patient with uncontrolled seizures is not a good surgical candidate, a vagus nerve stimulator or a responsive neurostimulator may be implanted in some cases. The former is implanted in the chest and connected by a wire to the vagus nerve (a cranial nerve) in the neck; like a pacemaker, the device regularly stimulates the nerve to counteract seizures. It also may be activated by the patient in response to a seizure. The responsive neurostimulator is implanted in the skull, and wires connect it to brain regions that are the focus of seizures. In reaction to developing seizure, it electrically stimulates those regions in an effort to stop the seizure. Patients with such devices take antiseizure medications as well, and these devices typically reduce but do not eliminate seizures.

See H. Reisner, ed. Children with Epilepsy (1988); R. J. Gunnit, Living Well with Epilepsy (1990); O. Devinsky, A Guide to Understanding and Living with Epilepsy (1994); publications of the Epilepsy Foundation of America.

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