Febrile seizure symptoms can range from mild — staring — to more severe shaking or tightening of the muscles.
A child having a febrile seizure may:
- Have a fever higher than 100.4 F (38.0 C)
- Lose consciousness
- Shake or jerk arms and legs
Febrile seizures are classified as simple or complex:
- Simple febrile seizures. This more common type lasts from a few seconds to 15 minutes. Simple febrile seizures do not recur within a 24-hour period and are generalized, not specific to one part of the body.
- Complex febrile seizures. This type lasts longer than 15 minutes, occurs more than once within 24 hours or is confined to one side of your child's body.
Febrile seizures most often occur within 24 hours of the onset of a fever and can be the first sign that a child is ill.
When to see a doctor
See your child's doctor as soon as possible after your child's first febrile seizure, even if it lasts only a few seconds. Call an ambulance to take your child to the emergency room if the seizure lasts longer than 10 minutes or is accompanied by:
- A stiff neck
- Breathing problems
- Extreme sleepiness
A high body temperature causes most febrile seizures.
Usually the fevers that trigger febrile seizures are caused by a viral infection, less commonly by a bacterial infection. Viral infections such as the flu and roseola, which often are accompanied by high fever, appear to be most associated with febrile seizure.
The risk of febrile seizures may increase after some childhood immunizations, such as the diphtheria, tetanus and pertussis or measles-mumps-rubella vaccinations. A child can develop a low-grade fever after a vaccination. The fever, not the vaccination, causes the seizure.
Factors that increase the risk of having a febrile seizure include:
- Young age. Most febrile seizures occur in children between 6 months and 5 years of age. It's unusual for children younger than 6 months to have a febrile seizure, and it's rare for these seizures to occur after 3 years of age.
- Family history. Some children inherit a family's tendency to have seizures with a fever. Additionally, researchers have linked several genes to a susceptibility to febrile seizures.
Most febrile seizures produce no lasting effects. Simple febrile seizures don't cause brain damage, mental retardation or learning disabilities, and they don't mean your child has a more serious underlying disorder.
Febrile seizures don't indicate epilepsy, a tendency to have recurrent seizures caused by abnormal electrical signals in the brain.
Recurrent febrile seizures
The most common complication is the possibility of more febrile seizures. The risk of recurrence is higher if:
- Your child's first seizure resulted from a low fever.
- The period between the start of the fever and the seizure was short.
- An immediate family member has a history of febrile seizures.
- Your child was younger than 15 months at the time of the first febrile seizure.
Most febrile seizures occur in the first few hours of a fever, during the initial rise in body temperature.
Giving your child medications
Giving your child infants' or children's acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin, others) at the beginning of fever may make your child more comfortable, but it won't prevent a seizure.
Use caution when giving aspirin to children or teenagers. Though aspirin is approved for use in children older than age 3, children and teenagers recovering from chickenpox or flu-like symptoms should never take aspirin. This is because aspirin has been linked to Reye's syndrome, a rare but potentially life-threatening condition, in such children.
Prescription prevention medications
Rarely, prescription anticonvulsant medications are used to try to prevent febrile seizures. However, these medications can have serious side effects that may outweigh any possible benefit.
Oral diazepam (Valium), lorazepam intensol, clonazepam (Klonopin) or rectal diazepam (Diastat) may be prescribed for children who are prone to febrile seizures. These medications are typically used to treat seizures that last longer than 10 minutes or if the child has more than one seizure within 24 hours. They are not typically used to prevent febrile seizures.