Febrile seizures are convulsions that occur in young children who have a fever. These seizures are common, affecting approximately 2% to 5% of all children, typically between 6 months and 5 years. While alarming for parents, they are generally harmless and do not indicate a serious long-term health problem. This article discusses factors contributing to these seizures, including genetic links, and offers guidance on how to respond and what to expect.
What Causes Febrile Seizures
Febrile seizures are triggered by a fever, often a rapid rise in body temperature or a high fever. Even a low-grade fever, defined as 100.4°F (38°C) or higher, can initiate a seizure. These seizures most commonly occur in children between 6 months and 5 years old, with the highest incidence in toddlers aged 12 to 18 months.
Fevers that trigger these seizures are caused by common infections, such as viral illnesses like the flu or roseola, and less frequently by bacterial infections. The seizure often happens in the first 24 hours of an illness and can sometimes be the first sign a child is unwell. While the exact mechanism by which fever leads to a seizure is not fully understood, it involves the brain’s response to elevated temperature.
The Role of Genetics
While not solely determined by genetics, a strong predisposition to febrile seizures can be inherited. Children are more likely to experience a febrile seizure if a parent, sibling, or other close relative has a history of them, with familial studies showing occurrence rates from 10% to 46%. Twin studies further support this genetic influence, demonstrating a higher concordance rate in identical twins compared to fraternal twins.
Researchers have identified several gene regions, such as FEB1 to FEB11, that may increase a child’s susceptibility. Genes involved in the body’s fever response, like PTGER3 and IL10, have been linked to an increased risk, suggesting genetic variations might lead to a more pronounced fever response. Other genes, including GABRG2, SCN1A, and SCN2A, which influence neuronal excitability and are also associated with epilepsy, have been implicated. However, possessing these genetic markers does not guarantee a seizure will occur; environmental factors, like a fever, are also necessary for the seizure to manifest.
Recognizing and Responding to Febrile Seizures
When a child experiences a febrile seizure, staying calm is important. Gently place the child on the floor, protecting their head with your hands or a soft object. Position the child on their side to prevent choking and loosen any tight clothing around their head and neck. Do not try to hold or restrain the child, nor should anything be placed in their mouth.
Monitor the time the seizure begins and ends. Most febrile seizures are brief, lasting between a few seconds and 10 minutes, rarely exceeding 15 minutes. Seek immediate medical attention if the seizure lasts longer than 5 minutes, if the child has difficulty breathing, turns blue, or remains unresponsive after the seizure. Medical evaluation is also advised for a first-time seizure, if the seizure affects only one side of the body, or if multiple seizures occur within 24 hours.
Long-Term Outlook and Recurrence
Most children who experience febrile seizures outgrow them by age 5 or 6. These seizures do not cause long-term neurological or developmental problems. The risk of developing epilepsy after a simple febrile seizure is low, estimated at 1% to 2%, comparable to the general population. Children who develop epilepsy after febrile seizures usually have other risk factors, such as a family history of epilepsy or pre-existing neurological conditions.
About one-third of children who have one febrile seizure will experience another with a future febrile illness. The likelihood of recurrence is higher in children who had their first seizure at a younger age, under 18 months, or who have a family history of febrile seizures. While frightening, most children with febrile seizures lead healthy lives without lasting complications.