Febrile Seizures

Febrile seizures are common in children between the ages of three months and five years. They happen when a child has a fever. They are frightening, but usually do not cause harm. Febrile seizures are rare under the age of six months and do not occur when the child is older.

What are other terms for febrile seizures?

Other terms for febrile seizures that you may come across include:

• febrile convulsions

• febrile fits

• fever convulsions

• fever seizures

• pyrexial seizures

What causes febrile seizures?

Three things interact to put young children at risk for febrile seizures:

• a child’s developing brain

• a genetic predisposition to seizures

• fever

Because febrile seizures occur during a specific age range, we know that the stage of a child’s brain development is an important factor.

There is a strong genetic component to febrile seizures. The parents of children with febrile seizures often had febrile seizures as well, and the risk that a child’s brother or sister will also have febrile seizures is about 25%.

Fever may be caused by almost any common childhood illness or infection, including:

• upper respiratory infection

• ear infection

• pneumonia

• gastroenteritis, or the “stomach flu”

• roseola infantum

Note that if a seizure is provoked by a central nervous system infection such as meningitis, it is not considered a febrile seizure.

What are the features of febrile seizures?

Most febrile seizures happen between the ages of six months and three years. The majority of febrile seizures last for less than 15 minutes, and the child generally does not have another seizure. However, some febrile seizures last for more than 15 minutes, and they can recur.

Febrile seizures usually happen quite early in the course of the illness. Sometimes the seizure happens even before a parent knows that the child is ill or has a fever.

How do you know that a child has febrile seizures?

To diagnose a febrile seizure, the doctor will ask the child’s parent or whoever observed the seizure to describe it carefully. He will conduct a physical and neurological examination. If the cause of the fever is known, and the child is not unconscious, he will not usually ask for any laboratory tests. However, if he suspects something else is wrong, he may order some blood tests.

It is important to rule out other possible causes of seizures, such as a central nervous system infection. In children who are less than a year old, or older children who have been treated with antibiotics, the symptoms of meningitis may not be obvious and the doctor may order a lumbar puncture to rule out meningitis.

Unless the doctor suspects that the seizures have some other cause besides the fever, he will probably not order an EEG or imaging tests such as a computed tomography (CT) scan or magnetic resonance imaging (MRI).

How are febrile seizures treated?

A child having a febrile seizure should be given normal first aid. If the seizure lasts longer than five minutes, she should be taken to an emergency department. It is rarely necessary to admit a child with a first, simple febrile seizure to hospital.

If the child has a fever, it may be helpful to give her an anti-fever medication such as acetaminophen to keep the fever down and make her more comfortable, although one study has found that this does not prevent seizures.

Diazepam may be prescribed to prevent or shorten seizures in a child with fever. However, this is rarely prescribed because the medication can cause drowsiness and may mask the signs of serious infection. Diazepam may also depress breathing.

It is usually not necessary to give anti-epileptic drugs to a child who has febrile seizures, since the potential side effects probably outweigh the possible benefits. There is no evidence that giving anti-epileptic drugs will prevent the child from developing epilepsy later on.

What is the outlook for a child with febrile seizures?

The outlook for a child with febrile seizures is good. Most children with one febrile seizure never have another, and very few children with febrile seizures go on to develop epilepsy.

Between 30% and 40% of children who have had one febrile seizure will have at least one more, usually within a year of the first one. A child is more likely to have another febrile seizure if:

• she is less than a year old

• she has a family history of febrile seizures

• she had a seizure soon after her fever began

• her temperature was not very high when she had the seizure

There is no evidence that a short febrile seizure damages the brain. Studies of children with febrile seizures and their siblings without febrile seizures showed no difference in intelligence, school achievement, behaviour, height, or head circumference.