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Febrile Seizures (Seizures and Fever)

What Is the Relationship Between Seizures and Fever?

Febrile seizures, also known as convulsions, body spasms, or shaking, occur mainly in children and are caused by fever. (Febrile is derived from the Latin febris, meaning fever.) As with most types of seizures, the onset is dramatic, with little or no warning. In most instances, the seizure lasts only a few minutes and stops on its own.

Febrile seizures may occur because a child's developing brain is sensitive to the effects of fever. These seizures are most likely to occur with high body temperatures (higher than 102°F) but may also occur with milder fevers. The sudden rise in temperature seems to be more important than the degree of temperature. The seizure may occur with the initial onset of fever before a child’s caregiver is even aware the child is ill.

  • Seizures generally occur in those aged 3 months to 5 years; peak incidence is in infants aged 8-20 months.
  • About 2-5% of all children will experience a febrile seizure.
  • Of those who have had a febrile seizure, 30-40% will experience more seizures.
  • About 25% have a first-degree relative with a history of febrile seizure.
  • The seizure itself is almost always harmless. It does not cause brain damage or lead to epilepsy.

What Causes Febrile Seizures?

Febrile seizures are classified into 2 types:

  • Simple febrile seizures are more common and are characterized by generalized seizures that last less than 5 minutes.
  • Complex febrile seizures are those that are either prolonged (longer than 15 minutes), focal (meaning they involve only a part of the body, such as the face), or recurring within a 24-hour period.

Children who have experienced a complex febrile seizure may be at risk for these outcomes:

  • A somewhat higher risk of having a serious infection
  • More likely to have preexisting neurologic abnormalities
  • A higher risk for developing epilepsy later

Most fevers associated with febrile seizures are due to the usual causes of fever in young children—namely, common viral and mild bacterial infections such as ear infections. Although perhaps only 1% of children with febrile seizures have a serious infection of the central nervous system such as meningitis, this possibility should always be carefully considered in a child who has had a febrile seizure.

Medically Reviewed by a Doctor on 11/21/2017
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