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Children with benign focal sharp waves in the EEG--developmental disorders and epilepsy.

Focal sharp waves (shw) in the childhood EEG with predominantly centrotemporal localization are a diagnostic hallmark of idiopathic partial epilepsy and have been shown to be genetically determined. Absence of neurological and neuropsychological impairment was long considered to be a prerequisite for diagnosis. For years, this diagnostic paradigm obscured the large phenotypic variability of genetically determined focal shw. The purpose of the present review is to survey and critically evaluate the widely dispersed literature on this topic. Two main groups can be distinguished: Idiopathic partial epilepsies and specific developmental disorders such as dysphasia, dyslexia etc. These conditions, however, do not represent clear-cut nosologic entities, but exhibit large symptomatic overlaps. In non-epileptic children, developmental disabilities constitute the main symptoms, in epileptic children-at least in non-selected groups-they are an optional feature. Conversely, epileptic phenomena can dominate the clinical picture or be an optional symptom in developmentally disabled children. The wide spectrum of epileptic and non-epileptic disorders probably represents the multifarious clinical manifestations of a common widespread, genetically determined pathogenetic mechanism. The marked age-dependency of the EEG and clinical symptoms, and the almost regular disappearance of both at puberty appear to justify the hypothesis of a hereditary impairment of brain maturation. The large phenotypic variability can be explained by differences in location and extent of the maturational disturbance as well as by the effect of additional genetic and environmental factors. The nature and cause of the hypothetical maturational disturbance are still unknown.