Children with Focal Sharp Waves: Clinical and Genetic Aspects

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Abstract
To investigate the spectrum of clinical manifestations in children with benign focal sharp waves in the EEG to gain further insight into the genetic background of clinical and EEG symptomatology in a family study. All 147 children (134 with seizures, 13 without) met the following inclusion criteria: (a) at least one EEG with focal sharp waves characteristic of benign partial epilepsies, and (b) at least 1 sibling investigated by EEG. The families were questioned orally or in writing regarding the occurrence of seizures. Patients' records were evaluated by a standardized scheme. The following types of seizures occurred: febrile convulsions (FC), afebrile generalized tonic-clonic seizures (GTCS), simple and (rarely) complex partial seizures; and rolandic seizures in the strict sense. Neonatal seizures were overrepresented (6%); there were no indications of lesional causes. FC occurred in 38 children (26%). As compared with unselected cases of FC, complex symptoms were overrepresented. Family data suggested a maternal preponderance in the transmission of FC liability. Affected relatives of FC probands manifested FC more often than did relatives of probands without FC. Families of 32 patients with typical rolandic seizures (24% of the 134 probands with seizures) showed no aggregation of rolandic epilepsy, but did show variable seizure types. In the entire sample, EEG investigations showed focal sharp waves in 11% of siblings aged 2-10 years. No relation existed between clinical symptomatology and sharp wave findings in siblings. In 66% of probands, the EEG disclosed generalized genetic patterns. Siblings with generalized spike-waves (sw) and/or theta rhythm had focal sharp waves more often than those without sw and/or theta rhythm. The phenotypic expression of the genetic anomaly underlying focal sharp waves shows considerable variability. The clinical and EEG findings are in agreement with a multifactorial pathogenesis of epilepsies with "benign" focal epileptiform sharp waves.