REVISED ETIOLOGIC CLASSIFICATIONS AND TERMINOLOGY

“primary,” or “idiopathic,” in which no underlying cause can be identified other than a possible hereditary tendency * “secondary,” or “symptomatic,” in which symptoms are presumed to result from a known central nervous system (CNS) disorder * cryptogenic, in which symptoms are presumed to be secondary, although no cause has been determinedThe proposed update to the etiologic classification system uses, instead, the following concepts and terminology to describe epilepsy13: * “genetic,” in which seizures are the “core symptom” of the disease and the epilepsy is believed to result from known or presumed genetic defects * “structural–metabolic,” in which the patient not only has epilepsy but also has a structural or metabolic disorder that is associated with elevated risk of developing epilepsy under certain conditions * “unknown cause,” in which no cause has been identified, although it's understood that the epilepsy may result from an unrecognized genetic defect or other disorderEpilepsy may be caused by a variety of factors, including perinatal anoxia, congenital malformations of the brain, genetic disorders, infectious disease, metabolic disorders, cerebrovascular disease, traumatic brain injury, neoplasms, toxins, and degenerative nerve diseases. Seizures can also be triggered by sleep deprivation, poor nutrition, dehydration, photic and other forms of stimulation, stress, and alcohol or drug use or withdrawal. Although about one-third of all epilepsies have no known cause,13 a number of genetic discoveries and improved techniques in neuroimaging and neurophysiologic testing have greatly increased our understanding of the pathophysiology, diagnosis, and treatment of epilepsy and have contributed to an ongoing discussion within the ILAE regarding development of a new seizure classification system to replace the 1981 classification system and 1989 classification of the electroclinical syndromes of epilepsy. Previously the ILAE used the following categories to classify epilepsy etiology.

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