How Likely Are Febrile Seizures?

How worried should I be about febrile seizures happening?
—Anonymous

“Febrile seizures” are seizures that happen in infants and young children as a result of a high fever.

There are two ways I can read your question. The first is how likely they are. To which the answer is: moderately. Between 2% and 4% of children will have one; they typically occur between the ages of 6 months and 5 years, with a peak between 12 and 18 months.

You could also be asking how worried, if they happen, you should be about long-term consequences. The vast majority of febrile seizures are “simple,” defined as lasting less than 10 or 15 minutes (there is variation in the proposed cutoff) and not occurring repeatedly within 24 hours. These seizures are extremely likely to be benign; they do re-occur for a proportion of kids but are not associated with significant elevation in risks for long-term seizure disorders like epilepsy.

A “complex” febrile seizure episode involves recurrence within 24 hours, a long duration, and often some asymmetry in the focus of the seizure. These will need more significant follow-up and could be a sign of something else going on. Again, this is a very small share of seizures, which, again, happen in only 2% to 4% of children. So it’s overall quite a small risk.

It goes without saying that if your child does have a febrile seizure, even one that seems simple, you should involve your pediatrician.

“How worried” is always a complicated question. Having the facts may put you more in control.