Febrile seizures are one of the most common types of seizures in children, typically occurring between the ages of 6 months and 5 years. These seizures are associated with fever (100.4F or higher) anytime within the prior 24 hours and can be a source of significant anxiety for parents. Understanding febrile seizures is crucial for providers to limit unnecessary work up without missing other key diagnoses. This article covers the epidemiology, pathogenesis, pathophysiology, clinical features, diagnosis, treatment, and potential complications of febrile seizures.
Epidemiology
Febrile seizures are prevalent in children, affecting approximately 2% to 5% of children under the age of 5 years. The incidence of febrile seizures increases with the child’s age up to 18 months and then declines. There are multiple risk factors for febrile seizures, including genetic, recent illness, recent vaccination with DTaP and the combined MMR/VZV vaccination when given at the 1yr mark, and prenatal nicotine exposure.
Febrile seizures are more common in certain populations and environments, with variability influenced by geographic and socio-economic factors. For instance, they are more prevalent in developed countries, possibly due to differences in infection rates, vaccination status, and healthcare access, but also likely due to lack of access to healthcare and thus lack of recording of seizure events in developing countries.
Pathogenesis
The exact pathogenesis of febrile seizures remains incompletely understood, but several factors are believed to contribute:
A family history of febrile seizures or epilepsy is a significant risk factor. Genetic studies have identified several loci associated with an increased risk of febrile seizures, though specific genes have yet to be conclusively identified.
The developing brain in young children may have an increased susceptibility to the effects of fever. This is thought to be due to the underdevelopment of inhibitory mechanisms that normally prevent excessive neuronal firing.
The body’s response to infections often includes fever, which can trigger a seizure in predisposed individuals. The exact mechanism by which fever leads to seizures is not fully understood, but it is thought to involve neuronal excitability. HHV6 and Influenza can be linked to febrile seizure in up to a third of cases.
Rapid increases in body temperature are more likely to trigger seizures than a sustained high fever. This is due to the stress and imbalance caused by abrupt changes in body temperature, which can affect the brain’s electrical stability.
Pathophysiology
Febrile seizures occur as a result of an abnormal electrical discharge in the brain triggered by fever. The main pathophysiological features include:
Fever alters neuronal excitability by affecting ion channels and neurotransmitter systems, making the brain more prone to seizures. The immature brain in young children may have less effective inhibitory control, leading to an increased likelihood of seizures.
Seizures are more likely to occur when body temperature rises rapidly, especially when it reaches a threshold that the child’s developing brain is not accustomed to.
Clinical features
Febrile seizures are characterized by the following clinical features:
Typically occur between 6 months and 5 years of age, with the peak incidence between 12 and 18 months.
The seizure occurs within 24 hours of a fever, but often concurrently with the elevated temperature or as it is starting to rise. A true fever is anything greater than or equal to 38°C (100.4°F).
- Simple febrile seizures: Generalized tonic-clonic/tonic/atonic seizures that last less than 15 minutes and do not recur within 24 hours.
- Complex febrile seizures: Focal seizures or any seizure type lasting more than 15 minutes or > 1 seizure within 24 hours.
There may be a post-ictal period in both simple and complex febrile seizures.
Diagnosis
Diagnosing febrile seizures involves differentiating them from other types of seizures and identifying the underlying cause of the fever:
- Febrile seizure is a clinical diagnosis and does not require laboratory or imaging work up in the majority of cases, outside of exploration into the cause of the initial fever.
- Seizure characteristics: Detailed description of the seizure, including its onset, duration, and recovery phase.
- Fever history: Assessment of the fever, including its onset, duration, and associated symptoms.
- Not routinely recommended. Consider if your results are likely to be actionable, and if not then consider why you are ordering testing.
- The most common testing sent is a urinalysis with or without a urine culture in patients without signs of localizing infection, or a respiratory viral panel in those with signs of respiratory infection.
- Consider CBC, CMP, and CRP or procalcitonin (preferred when available) in those that are ill appearing (sepsis physiology) or unvaccinated.
- Lumbar puncture should be considered for those who present with meningeal signs or clinical picture concerning for meningitis, and in infants up to 12 months who are not up to date on their vaccinations for Haemophilus or Strep pneumoniae.
- Not routinely recommended but may be considered in complex cases.
- Computed Tomography (CT) or Magnetic Resonance Imaging (MRI): Indicated if there are atypical features, focal neurological signs, or prolonged seizures.
Indication: Generally reserved for atypical cases or when there is a concern for status epilepticus. May be done outpatient in conjunction with PCP and neurologists for patients with complex febrile seizures or recurrent simple febrile seizures.
Treatment
The goals in managing febrile seizures are to ensure the child’s ABC (airway, breathing, circulation) are intact, treat seizures that are prolonged, and address the cause of the underlying fever.
- Safety measures: Place the child on a soft surface and protect them from injury during the seizure. Do not restrain or put anything in the child’s mouth.
- Temperature control: Use antipyretics such as acetaminophen or ibuprofen to manage fever. There is no data to support use of antipyretics to prevent febrile seizures.
- Initial treatment: For seizures lasting more than 5 minutes, benzodiazepines such as rectal diazepam or intranasal midazolam may be administered.
- Further management: In cases of prolonged or frequent seizures, further evaluation and possible antiepileptic drug therapy may be needed.
Infection: Identification of any source of infection is crucial. Treatment with antibiotics for presumed or confirmed bacterial infections is standard practice.
Prognosis: Most children with febrile seizures do not require long-term medication. Antiepileptic drugs are typically reserved for children with frequent or prolonged seizures, or those with recurrent complex febrile seizures. Antiepileptic medication initiation should be done in conjunction with a pediatric Neurologist.
Potential complications
While febrile seizures are generally benign, there are potential complications that can arise:
- Recurrence: Febrile seizures can recur in approximately one-third of affected children. The risk of recurrence is higher if the first seizure occurs at a younger age (< 1 year old) or if there is a family history (first degree relative) of febrile seizures.
- Risk of developing epilepsy: The general population has a 0.5–1% incidence of epilepsy. That increases to ~1–2% for children with a history of simple febrile seizure, and ~5% for children with complex febrile seizures. The overall risk increase is minimal when translated clinically to number of patients.
- Injury: Although rare, injuries can occur during a seizure if the child falls or hits an object. Ensuring safety during a seizure is critical to prevent injury.
- Parental anxiety: Recurrent febrile seizures can cause significant anxiety for parents. Providing education and reassurance about the overall benign nature of febrile seizures and close follow up with their PCP is essential.
Prognosis
The overall prognosis for children with febrile seizures is excellent. Most children outgrow febrile seizures by the age of 6 years, and the long-term risk of developing epilepsy is only slightly higher than in the general population. Continued monitoring and reassurance are often all that is required.
Conclusion
Febrile seizures are a common and usually benign condition in young children, characterized by seizures associated with fever. Understanding their epidemiology, pathogenesis, and clinical features enables providers to effectively diagnose and manage this condition without over-medicalization of their patients. By focusing on supportive care, addressing underlying infections, and educating families, pediatricians can help mitigate the impact of febrile seizures and ensure optimal outcomes for their young patients. Regular follow-up and careful monitoring are essential to address any potential complications and to provide reassurance to families.
Image credits
Unless otherwise noted, images are from Adobe Stock.