The Prevalence and Incidence of Convulsive Disorders in Children

The 1980 National Institutes of Health Consensus Development Conference on Febrile Seizures identified five circumstances in which it might be appropriate to consider anticonvulsant prophylaxis after a first febrile seizure: (1) a focal or prolonged seizure, (2) neurologic abnormalities, (3) afebrile seizures in a first-degree relative, (4) age less than 1 year, and (5) multiple seizures occurring within 24 hours. We performed a metaanalysis of 14 published reports to evaluate the strength of association between each of these indications and recurrent febrile seizures. Young age at onset (less than or equal to 1 year) and a family history of febrile seizures (not listed in the recommendations) each distinguished between groups with approximately a 30% versus a 50% risk of recurrence. Family history of afebrile seizures was not consistently associated with an increased risk. Focal, prolonged, and multiple seizures were associated with only a small increment in risk of recurrence. The data were not adequate to assess the risk associated with neurologic abnormalities. By considering children with combinations of risk factors, some studies were able to distinguish between groups with very low and very high recurrence risks. Only age at onset was consistently predictive of having more than one recurrence. These results suggest that the great majority of children who have a febrile seizure do not need anticonvulsant treatment even if one of the factors listed in the Consensus Statement is present, and that the rationale and indications for treating febrile seizures need to be reconsidered.

The risk of recurrence after an initial febrile seizure was 25% in a population-based cohort of 639 children followed from their first febrile seizure. Prognostic factors were an increasing risk of recurrence with younger age at first febrile seizure, a first degree relative with febrile seizures and complex features of the first febrile seizure. The effect of complex features was modified by age at first febrile seizure and family history in that complex features alone did not increase risk of recurrence but further increased the risk for children under 18 months at first seizure and/or with a positive family history. The prognostic factors for all febrile convulsions recurrences were also prognostic for having subsequent complex febrile convulsions. Children with none of the prognostic factors had only a 3% risk of a future complex febrile seizure while children under 18 months at first febrile convulsion and a positive family history or complex features had about a 20% risk of a subsequent complex febrile seizure.