Duration of recognized fever in febrile seizure predicts later development of epilepsy

The current report examines the risk of and predictors for developing epilepsy in children with febrile seizure (FS). The present study addresses two factors that were previously identified as predictors of recurrent FS in previous reports: maximum temperature and duration of fever prior to the initial FS.

Children aged 6 months-6 years with an initial simple FS were eligible for the study. The interview included questions about the child's illness, family history of seizures, and other exposure information. In particular, they were asked about the duration of recognized fever prior to the seizure. After the initial interview, parents were called every 3-4 months to ascertain whether any further seizures had occurred and the circumstances under which such seizures occurred. Follow up ≥ 3 years was attempted for all children. Statistical analysis was done with χ(2) test, Fisher's exact test, Mann-Whitney U-tests and logistic regression analysis.

Five of 92 children (5.4%) experienced unprovoked seizures and were considered part of an epilepsy group. In four of these five patients, the duration of recognized fever prior to FS fell more than ± 2.5 SD outside the distribution for the non-epilepsy group. Either an unusually short or long recognized fever prior to the initial FS was associated with an increased risk of unprovoked seizures.

The duration of recognized fever appears to provide useful information about the risk for the later development of epilepsy.