Classifications and epidemiologic considerations of epileptic seizures and epilepsy.

The manifestations of epileptic disorders are widely known to be extremely protean. Classifying the disorders is a way of achieving a common understanding of the terminology used in identifying seizure disorders in the clinical or research settings. Two International Classifications have been developed, namely the International Classification of Epileptic Seizures and the International Classification of Epilepsy and Epileptic Syndromes. The first divides epileptic seizures into two major categories: partial and generalized. Partial epileptic seizures are further classified according to the impairment or the preservation of consciousness into simple partial and complex partial seizures. Either condition may secondarily generalize into tonic-clonic seizures. Under the International Classification, epilepsy and epileptic syndromes are initially classified according to their corresponding types of seizures into localization-related and generalized disorders. Each disorder is further classified according to the relationship to etiologic or predisposing factors into symptomatic, cryptogenic, or idiopathic types. The classifications undoubtedly will be further revised as more is learned about epileptic disorders with advances in electrophysiology, neuroimaging techniques, and molecular genetics. An overview of the epidemiology of epileptic disorders shows that, contrary to the popular belief, they are primarily disorders of childhood; age-specific incidence rates of first unprovoked seizure and of epilepsy are highest in the elderly. An appreciation of the epidemiology of seizure disorders is essential in their clinical and laboratory evaluation.