Characteristics of the epilepsies.

Epilepsy is not a specific disease but rather a heterogeneous group of disorders that have in common the characteristic of recurrent, usually unprovoked seizures. Epileptic seizures represent the intermittent and self-limited clinical manifestations (signs and symptoms) that result from abnormally excessive and synchronous activity of neurons. Seizures are categorized as partial (with the initial activation of a limited number of neurons in a part of 1 hemisphere) or generalized (with the initial activation of neurons throughout both hemispheres). Epilepsy, however, is more than just recurrent seizures. It includes a specific etiology, associated neurologic abnormalities, a genetic background, environmental factors, responses to various therapies, and other factors. The disability and the effect on quality of life may be different for each individual. A variety of epileptic conditions have associated clinical and electroencephalographic (EEG) features that can be categorized as syndromes. Many of the syndromes have different etiologies in different patients yet share common characteristics such as the age at seizure onset; seizure type(s); intellectual development; and findings on neurologic examinations, EEGs, and neuroimaging. The epilepsies are categorized into 3 groups (idiopathic, cryptogenic, and symptomatic) on the basis of the presumed etiologies. Understanding the characteristics of the epilepsy syndromes provides a powerful tool for the prognosis and treatment of individuals experiencing seizures. In this article, we discuss characteristic features of the epilepsies.