First febrile seizures. Characteristics of the child, the seizure, and the illness.

Through interviews with parents, data were gathered about 910 first febrile seizures in children aged 8 to 34 months. A male preponderance of 57% was found (P < .001). In 29% of cases, there was a family history of febrile seizures. Eighteen percent of seizures were focal, and 7% lasted 15 minutes or more. Focal seizures were much more likely to be of long duration (P < .001). Otitis media was diagnosed in 32% of cases, and tonsillitis or upper respiratory infection in 12%. When compared to febrile seizures after the first birthday, febrile seizures in children aged 8 to 11 months were more than twice as likely to be longer than 15 minutes (P = .015). They were also much more likely to be followed by further seizures in the same illness (P < .001). Thus, febrile seizures in children younger than 1 year are more likely to have the characteristics known to increase the risk of later nonfebrile seizures.