Seizures, Febrile

Descriptive text is not available for this imageBASICS

DESCRIPTION

  • Febrile seizure: seizure in ≤60-month-old child accompanied by a fever (≥100.4°F or 38°C by any method) but without central nervous system infection or prior unprovoked seizure
    • American Academy of Pediatrics (AAP) guidelines use 6 months as the lower age limit and specify that they occur in a child without history of a neurologic disorder or disorder with increased risk for seizures.
    • International League Against Epilepsy uses 1 month as the lower age limit but does not explicitly exclude children with underlying neurologic disorders.
  • Two types
    • Simple
      • Febrile seizures that are generalized from the start
      • Duration: <15 minutes
      • Does not recur in 24 hours
    • Complex
      • Febrile seizures that are focal (including postictal weakness), last >15 minutes, or occur >1 time in 24 hours (simple febrile seizures plus—a new proposed category for those seizures whose only complex feature is >1 seizure in 24 hours)
      • Febrile status epilepticus: one febrile seizure or series of febrile seizures without a full recovery in between, lasting >30 minutes

EPIDEMIOLOGY

  • Age
    • Most febrile seizures occur between 6 months and 3 years of age.
    • Peak age is about 18 months.
  • Type
    • 65–70% are simple febrile seizures.
    • 20–35% are complex febrile seizures.
    • ~5% are febrile status epilepticus.
  • Timing of seizure
    • ~20% before of <1 hour of fever onset
    • ~60% 1 to 24 hours after fever onset
    • ~20% >24 hours after fever onset
  • Most common childhood seizure
    • Febrile seizures occur in 2–5% of children in the United States and Eastern Europe.
    • 7–10% of children in Japan
    • 14% of children in Guam

ETIOLOGY

  • Likely multifactorial, including an underlying susceptibility of the brain’s response to fever that is triggered by genetic and environmental factors
  • Risk is related to the height of temperature elevation, not the rate of temperature rise.

RISK FACTORS

  • Positive family history of febrile seizures
  • Prior febrile seizure
  • Any viral or bacterial infection
  • Vaccines
    • Vaccine-induced fever in a susceptible child
    • These may increase the risk of febrile seizures but not epilepsy.
  • Developmental delay
  • 1st-degree relative with history of febrile seizures
  • Child care attendance

Genetics

Usually multifactorial or polygenic inheritance

GENERAL PREVENTION

  • Antipyretics do not reduce the recurrence risk of simple febrile seizures.
  • Very low risk of febrile seizure after vaccinations
    • Routine childhood immunizations are recommended as the morbidity of vaccine-preventable illnesses outweighs the risk of febrile seizures.
    • Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) does not list febrile seizures as contraindication to any commonly used vaccine.
    • Seizures ≤3 days after a previous dose of DTP/DTaP are listed as a precaution for future doses.

PATHOPHYSIOLOGY

  • Elevated temperatures in developing brain may increase neuronal excitability.
  • Fever increases cytokines that may enhance neuronal excitability.
  • Hyperventilation from fever causes a respiratory alkalosis that may promote seizures.

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