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Understanding the etiology of a patient’s epilepsy may allow the physician to provide prognostic information and, most appropriately, manage the seizures. The classification system most widely used for the epilepsies is the International Classification of Epilepsies and Epileptic Syndromes set forth by the International League Against Epilepsy (ILAE) (see Chapter 557). Reflecting the importance of the cause underlying the epilepsy, this system delineates 3 primary categories of etiological classification: symptomatic, cryptogenic, and idiopathic.1 Symptomatic epilepsy refers to epilepsy that is a symptom of a known underlying cause, such as a structural brain lesion. Cryptogenic epilepsy, sometimes called “presumed symptomatic” epilepsy, occurs in children with other neurological abnormalities, suggesting that the symptoms are referable to an underlying etiology, albeit occult. Idiopathic epilepsy traditionally referred to epilepsy without discernable predisposing cause in otherwise normal children, but it has been increasingly evident that this category encompasses epilepsies with genetic underpinnings.

It is estimated that 20% to 40% of children presenting with epilepsy have an identifiable etiology that would place them in the symptomatic category.2 Nonetheless, the consideration of a possible underlying etiology dominates the initial evaluation of a child presenting with epilepsy. Many of the causes listed below are identifiable using magnetic resonance imaging (MRI). When MRI does not reveal an etiology for the epilepsy, further evaluation of potential genetic and metabolic causes should be undertaken. Table 558-1 lists some of the major diagnostic considerations that will motivate a thorough evaluation. Many of the individual conditions are discussed in other chapters.

Table 558-1. Etiologies of Symptomatic Epilepsy

Symptomatic epilepsy should be suspected in a child with epilepsy in the following conditions: (1) any child with new onset of localization-related (focal) epilepsy; (2) any child presenting with epilepsy with other neurological symptoms, such as developmental delay, or signs, such as hemiparesis; and (3) any child with a history or examination that leads to the suspicion of a specific etiology. Uncovering a specific etiology does not necessarily lead to a specific treatment based on the ...

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