Background: Febrile seizures affect 2 to 4% of children, and 2 to 10% develop subsequent unprovoked seizures. Secondary analyses of two large cohorts identified neurodevelopmental abnormalities, complex febrile seizures, and a family history of epilepsy as predictors of unprovoked seizures. We present an analysis of children prospectively followed from their first febrile seizure to reassess these three factors, examine factors of equivocal importance, and assess the importance of some new factors that we identified as predictors of recurrent febrile seizures.
Methods: Children (N = 428) were prospectively identified for a first febrile seizure through pediatric emergency departments of four hospitals. Information was collected from medical records and interviews with parents. Children were followed for 2 years or more.
Results: Unprovoked seizures occurred in 26 (6%). Neurodevelopmental abnormalities, complex febrile seizures, and a family history of epilepsy were associated with an increased risk of unprovoked seizures. Recurrent febrile seizures and brief duration of fever before the initial febrile seizure were also risk factors. A family history of febrile seizures, temperature and age at the initial febrile seizure, sex, and race were not associated with unprovoked seizures.
Conclusions: We confirmed the increased risk associated with traditionally accepted predictors of epilepsy following febrile seizures. Also, the risk clearly increased with recurrent febrile seizures. In general, predictors of subsequent unprovoked seizures differ from predictors of recurrent febrile seizures. One notable exception, brief duration of fever before the initial febrile seizure, predicts both types of outcome and may be a marker for an increased susceptibility to seizures.