Febrile seizures

Children aged six months to five years may have tonic-clonic (convulsive) seizures when they have a high fever. These are called febrile seizures and occur in approximately 2 - 5% of children.

Febrile seizures can occur in otherwise healthy children with normal development. They usually occur when a child has a viral illness with a high fever. As the child’s temperature rises rapidly, they experience a tonic-clonic seizure which usually involves muscles on both sides of the body. Unlike tonic-clonic seizures in later childhood or adulthood, febrile seizures commonly last longer than five minutes. There is a slight hereditary tendency with these types of seizures.

In most instances, hospitalisation may not be necessary although a prompt medical consultation is essential, particularly for the first event or in the very young. Other more serious conditions that cause seizures with fever (e.g. meningitis/encephalitis) may need to be excluded.

Prognosis

The prognosis for febrile seizures is usually excellent. Recurrence rates vary from 50% if the seizure occurred before one year of age, to 25% if the seizure occurred after one year. The vast majority of children with febrile seizures do not have seizures without fever after the age of five years.

Risk factors for later epilepsy include:

abnormal development before the febrile seizure
complex febrile seizures (seizures lasting longer than 15 minutes, more than one seizure in 24 hours, or seizure movements restricted to one side of the body)
a history of seizures without fever in a parent or sibling

If no risk factors are present, the chances of later epilepsy are the same or nearly the same as in the general population (approximately 1%).