Febrile seizures are the most common neurologic disorder in childhood, affecting up to 4 percent of children in the United States and Great Britain. A simple febrile seizure is defined as a generalized seizure occurring once in a 24-hour period, lasting less than 15 minutes, and associated with fever in a neurologically healthy child. Offringa and Moyer reviewed the prevalence of meningitis in children with febrile seizures and the risk of recurrence after a first febrile seizure. The evidence is summarized in the accompanying table on page 1448
Estimates of the likelihood of meningitis presenting as a childhood febrile seizure are derived from studies of children treated in emergency departments. Based on a review of seven studies in urban hospital emergency departments (2,100 cases), the prevalence is between 1 and 2 percent in the United States. Information from two Dutch hospitals indicates that the prevalence may be as high as 7 percent in the Netherlands (selective referral; up to 50 percent of febrile seizures in that country are managed by general practitioners).
Clinical features are the most useful factors in discriminating between meningitis and other causes of seizure in children. If one or more of the major clinical signs of meningitis—petechiae, nuchal rigidity, and coma— are not present, meningitis is extremely unlikely. In the studies, no cases of meningitis were diagnosed without the presence of at least one of these features. Age, sex, degree of fever, and data from blood tests did not have diagnostic value in the studies. The authors concluded that lumbar puncture should be performed only in children at high risk for meningitis.
|Question||Type of evidence||Result||Comment|
|What is the probability of bacterial meningitis after a seizure associated with fever?||Summary of surveysof children seen in accident and emergency departments||0.2% to 7.0%, depending on health care system and setting||Dutch (and English) general practitioner referral system will select children with a higher risk to present to accident and emergency departments.|
|Can an unremarkable physical examination and history reliably exclude bacterial meningitis?||Case-control study evaluating risk factors||Meningitis could be ruled out in the absence of focal, prolonged, or multiple seizures, suspicious findings on physical examination (petechiae, signs of circulatory failure, etc.), and abnormal neurologic findings on physical examination (signs of meningeal irritation and various degrees of coma).||It is very unusual for a child with meningitis to present only with a seizure.|
|Can prophylactic treatment with continuous antiepileptic drugs, intermittent oral diazepam, or an antipyretic decrease the likelihood of future febrile seizures?||Two systemic reviews of randomized trials, two randomized Trials||Continuous antiepileptic drugs, intermittent diazepam, or antipyretics did not reduce the recurrence rate.||Two meta-analyses with same results; lack of effectiveness and side effects limit the use of intermittent oral diazepam.|
|What is the likelihood of future febrile seizures?||Synthesis of five cohort studies with risk factor analyses and a cohort study||The most important factor is the child's age; having a first-degree relative with febrile or unprovoked seizures increases the risk of recurrence.||Variance in risk of recurrence is related to the presence of risk factors; complex features to the seizure do not predict recurrence of febrile seizures but are associated with an increased risk of epilepsy.|
Treatment of febrile seizures is focused on preventing recurrence. One trial in children with a mean age of 24 months who had one or more febrile seizures compared diazepam (administered orally every eight hours during febrile illness) with placebo. Over a mean period of two years, the relative annual risk of febrile seizures per child was 0.56. The study found that many parents did not follow treatment instructions. Analysis limited to children who had seizures while receiving the study drug demonstrated an 82 percent risk reduction with diazepam therapy. This benefit must be balanced against the finding that 25 to 30 percent of the children treated with diazepam developed symptoms such as irritability, ataxia, or lethargy.
Older studies of phenobarbital and val-proate showed no statistically significant reductions in the recurrence of febrile seizures. Although one meta-analysis found limited benefit from continuously administered prophylactic phenobarbital, eight children would have to be treated for two years to prevent one febrile seizure, and the burden of adverse effects was high. One randomized, placebo-controlled study of ibuprofen given every six hours during fever (temperature higher than38.4°C [101.1°F]) showed no reduction in seizure recurrence.
One large collaborative study involving 1,410 episodes of recurrent seizure in 2,496 children estimated that 32 percent had one recurrence, 15 percent had two recurrences, and 7 percent had three or more recurrences, with 7 percent of the recurrent seizures being complex. The risk of recurrence was greatest between 12 and 24 months of age.
The authors recommended a conservative approach to febrile seizures in low-risk children. They stressed the importance of explanation and discussions with the parents to address their concerns about recurrence. Parents should also be given directions on the rectal administration of diazepam if a seizure lasts more than 15 minutes.