0832 Mortality after febrile seizures

Some 2-5% of children will experience a febrile seizure before 5 years of age, with ⅓ likely to have more than one episode. Epilepsy is likely in 2-4% of those experiencing a febrile seizure, and because children with epilepsy are known to have a higher mortality risk than the general population, there has been an inevitable link between febrile seizures and increased risk of death. However, since febrile seizures may be simple (brief, generalized, non-recurrent during the same febrile illness) or complex (focal features, long duration, recurrence within 24 hours), the obvious question is whether any increased risk of death would apply equally to both variants. An hypothesis from the early 1980’s suggested that cot death and febrile seizures might be linked aetiologically through a common infectious or environmental agent, anatomical abnormality or genetic susceptibility to fever; however this does probably not apply, if for no other reason than SIDS and febrile seizure rates vary in different populations. On the other hand, there is some evidence that in a sub-group of patients there might be anatomical abnormalities that predispose to both (complex) febrile seizures and death. A recent study in the Lancet adds weight to the evidence that any significant increase in mortality risk is confined to those children with complex febrile seizures (that are effectively symptomatic of an underlying structural or functional disorder). In the study, data from some 1.6 million Danish children of ≥3 months were analysed. Of the cohort 55 215 experienced a febrile seizure and overall some 8000 died (only 232 from the group with febrile seizures). Mortality for those with febrile seizures was ~5-fold higher during the first two years, after which it was close to that of the general population. However, as with the risk of epilepsy, the raised mortality risk was again confined to the group with complex febrile seizures and underlying pathology. Parents may be reassured that despite the frightening presentation of a simple febrile seizure there is little if any evidence for an increased risk of death.

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Lancet 2008; 372: 457-63 and 429-30
Pediatr Dev Pathol 2007; 10: 208-23
Lancet 1981; 2: 176-8