Focal seizures are the most common seizure type presenting in childhood. They may present as the occurrence of a single seizure type, or as part of a wider spectrum of seizure types integral to an epilepsy syndrome. By definition and implication, such seizures arise from one area of the brain. The most recent proposal by the ILAE (The International League Against Epilepsy) defined a focal seizure "as one that originates within networks limited to one hemisphere. They may be discretely localised or more widely distributed and may also arise in subcortical structures. For each seizure type, ictal onset is consistent from one seizure to another, with preferential propagation patterns that can involve the contralateral hemisphere. In some cases however there is more than one network, and more than one seizure type, but each individual seizure type has a consistent site of onset."1
Focal seizures can then be described on the basis of semiology (the clinical presentation of the event), which depends on the area of brain origin and propagation pattern, both of which define the localization of seizure onset. By recognizing the clinical seizure pattern, with or without EEG confirmation, seizure onset may be attributed to one particular lobe (e.g., temporal lobe) or localized brain region (e.g., supplementary motor area). Further, they may be described according to whether consciousness (awareness) is retained (see Table 10–1). The terms "complex" and "simple" may be confusing; therefore, it has been recommended that these terms should no longer be used. The term "dyscognitive" has been proposed for impaired awareness (if this can be determined).1
TABLE 10–1.DESCRIPTORS OF FOCAL SEIZURES ACCORDING TO DEGREE OF IMPAIRMENT DURING SEIZUREa
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