Temperature, age, and recurrence of febrile seizure

OBJECTIVE: Prediction of a recurrent febrile seizure during subsequent episodes of fever. DESIGN: Study of the data of the temperatures, seizure recurrences, and baseline patient characteristics that were collected at a randomized placebo controlled trial of ibuprofen syrup to prevent febrile seizure recurrences. SETTING: Two pediatric hospitals in the Netherlands. PATIENTS: A total of 230 children with an increased risk of febrile seizure recurrence. MAIN OUTCOME MEASURE: Seizure recurrence during a subsequent fever episode. RESULTS: A total of 509 episodes of fever were registered with 67 recurrences; 35 (52%) recurrences within the first 2 hours after fever of onset had a lower median temperature (39.3 degrees C) than 32 (48%) after more than 2 hours of fever (40.0 degrees C, P<.001). Poisson regression analysis resulted in 3 univariably significant (P<.05) predictors of a recurrence of seizure during a subsequent episode of fever. In a multivariable model, they were corrected for their correlation: interval between the last previous seizure and fever of onset less than 6 months (relative risk= 1.3 [95% confidence interval: 0.8-2.4]), age at fever of onset (relative risk=0.7 [95% confidence interval: 0.5-1.0] per year increase) and temperature at fever of onset (relative risk = 1.7 [95% confidence interval: 1.1-2.8] per degree Celsius increase). CONCLUSIONS: Half of the recurrent seizures occur in the first 2 hours after fever of onset of a subsequent fever episode. If seizure recurs at a later time, the temperature at seizure is higher compared with recurrences occurring in the first 2 hours of fever. Young age at fever of onset, high temperature at fever of onset, and high temperature during the episode of fever are associated with an increased risk of a recurrent febrile seizure at the moment that a child with a history of febrile seizures has fever again.