Febrile Seizures

Patient/Family Story

Tommy was just 14 months old. He caught a cold from one of the children in the playgroup. He had a fever and runny nose. He was taking a nap when I heard this strange banging sound. I ran into his room, and his whole body was stiff and shaking. The whole thing probably lasted less than 10 minutes. They were the longest 10 minutes of my life. He has never had another one, and doesn’t need any seizure medication. Now when he has a fever I give him Tylenol.

What are Febrile Seizures?

Children aged 6 months to 5-6 years may have tonic-clonic seizures when they have a high fever. These are called febrile seizures and occur in 2% to 5% of children. There is a slight familial (hereditary) tendency toward febrile seizures. In other words, the chances are slightly increased that a child will have febrile seizures if parents, brothers or sisters, or other close relatives have had them. The peak age of febrile seizures is about 18 months. The usual situation is a healthy child with normal development, who has a viral illness with high fever. As the child's temperature rapidly rises, he or she has a tonic-clonic seizure. The seizure usually involves muscles on both sides of the body. Febrile seizures can be as short as a minute or two, or as long as 30 minutes or more. They also can be repetitive. In most instances, hospitalization is not necessary, although a prompt medical consultation is essential after the first seizure.

How are Febrile Seizures Treated?

Most children with recurrent febrile seizures do not require daily antiepileptic drug therapy. Children who have had more than three febrile seizures or prolonged febrile seizures, or who have seizures when they have no fever, are usually treated with antiepileptic drugs including phenobarbital and/or valproate. Diazepam (Valium), if given by mouth or rectum at the time of fever, has been used effectively to both treat and prevent recurrent febrile seizures. However, the dose that is effective when given by mouth can cause irritability, insomnia, or other troublesome side effects that last for days.

What is the Prognosis?

The prognosis for febrile seizures is excellent. There is no reason for a child who has had a single febrile seizure to receive antiepileptic drugs unless the seizure was unusually long or other medical conditions warrant it. Recurrence rates (the chances of having another seizure) vary from 50% if the seizure occurred before age 1 year to 25% if the seizure occurred after that age. In addition, 25% to 50% of recurrent febrile seizures are not preceded by a fever. In some cases, the seizure is the first sign of an illness (usually viral) and the fever comes later. The vast majority of children with febrile seizures do not have seizures without fever after age 5.

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 body movements during the seizure restricted to one side)
  • A history of seizures without fever in a parent or a brother or sister.

If none of these risk factors is present, the chances of later epilepsy are the same or nearly the same as in the general population; if one risk factor is present, the chances of later epilepsy are 2.5%; if two or more risk factors are present, the chances of later epilepsy range from 5% to over 10%. Rarely, febrile seizures that last more than 30 minutes may cause scar tissue in the temporal lobe and chronic epilepsy that can be effectively treated with medication or a temporal lobectomy.