Risk of epilepsy after febrile convulsions: a national cohort study.

OBJECTIVE

To identify children with febrile convulsions, classify their febrile convulsions into simple and complex, and determine the number and type of subsequent afebrile seizures in those children.

DESIGN

National population based study.

SETTING

United Kingdom.

SUBJECTS

16,004 neonatal survivors born during one week in April 1970.

MAIN OUTCOME MEASURES

Information about febrile and afebrile seizures obtained from questionnaires at 5 and 10 years of age and from hospital records.

RESULTS

Information was available for 14,676 of the cohort children. 398 (2.7%) of them had had at least one febrile convulsion. 16 children were known to be neurologically or developmentally abnormal before the first attack. Of the remaining 382 children, 305 had had a simple first febrile convulsion and 77 a complex first febrile convulsion. Thirteen of the 382 had had one or more afebrile seizures, nine of whom had developed epilepsy (recurrent afebrile seizures). A higher proportion of children with complex febrile convulsions (6/95) rather than simple febrile convulsions (3/287) developed epilepsy, the risk being highest for those who had had focal febrile convulsions (5/17; chi 2 = 39.9, p less than 0.001). Three of the 32 children who had prolonged febrile convulsions developed afebrile complex partial seizures.

CONCLUSIONS

The risk of epilepsy after febrile convulsions is much less than reported in many hospital studies, and if febrile convulsions cause brain damage that leads to later epilepsy this is a rare occurrence.