Overview of Febrile Seizures
Febrile seizures, also called fever-induced seizures or febrile convulsions, are seizures caused by fever. Although febrile seizures often are frightening for parents and caregivers, they usually are harmless.
In most cases, the seizure lasts fewer than 5 minutes and the child recovers completely with no lasting effects. However, if the seizure lasts longer than 15 minutes, the child is seriously injured during the seizure (e.g., from a fall), or complications (e.g., difficulty breathing, choking) develop, the parent or caregiver should dial 911 or contact the child's pediatrician immediately.
During a febrile seizure, involuntary muscle contractions and relaxations cause the child to shake, twitch, become rigid or stiff, move the limbs on one (less common) or both sides of the body, and lose consciousness. Febrile seizures usually last fewer than 5 minutes, but they may last from a few seconds to 15 minutes or longer. Children rarely have more than three febrile seizures during their lifetime.
Febrile seizures usually occur in young children between the ages of 3 months and 5 years. They are not related to epilepsy, which is a neurological condition caused by abnormal nerve cell activity in the brain.
In most cases, febrile seizures are associated with an illness, such as an upper respiratory infection (e.g. common cold, ear infection, roseola). They often occur during the first day of the fever or illness. Febrile seizures usually are related to fever higher than 102°F (38.8°C).
Normal body temperature in children often varies slightly throughout the day. This temperature usually is about 98.6°F (37°C) taken orally and 100.4°F (38°C) taken rectally. Parents should contact their child's pediatrician immediately if they have concerns about their child's body temperature or if any of the following occurs:
- Fever in a newborn (younger than 3 months of age)
- Fever exceeds 104°F (40°C)
- Fever lasts longer than 24 hours
- Fever subsides and then recurs
- Fever is accompanied by other symptoms, such as:
- Convulsion (febrile seizure)
- Difficulty breathing
- Inability to swallow or excessive drooling
- Inconsolable crying or crying when moved or touched
- Lethargy, drowsiness, or confusion
- Painful urination
- Stiff neck
Types of Febrile Seizures
There are two types of febrile seizures. Simple febrile seizures last fewer than 15 minutes, do not recur within 24 hours, and are generalized (i.e., affect a widespread area of the body). Following a simple febrile seizure, the child may be drowsy or confused for a short period of time.
Complex febrile seizures last longer than 15 minutes, recur within 24 hours, or are focalized (i.e., affect a specific area of the body). Complex febrile seizures can occur as a result of a serious illness, such as meningitis (inflammation of the membranes that surround the brain and spinal cord) or encephalitis (brain inflammation). Children who experience complex febrile seizures have a slightly higher than normal risk for developing epilepsy.
Incidence and Prevalence of Febrile Seizures
Febrile seizures, which affect approximately 3 percent of children, are most common between the ages of 6 and 18 months. A child's first febrile seizure rarely occurs before the age of 3 months or after the age of 3 years.
Boys have a slightly higher risk for febrile seizures than girls. About 30–50 percent of children who have a febrile seizure experience an additional seizure. Most children outgrow febrile seizures by the age of ten.