Febrile seizure

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Background

  • Seizure accompanied by fever (≥100.4°F / 38°C) in a child 6 months to 5 years without CNS infection or metabolic cause
  • Occur in 2-5% of children before age 5[1]
  • Most common seizure type in childhood
  • High temperatures alter ion channel function, increasing neuronal excitability[2]
  • A high temperature is NOT necessarily seen in all febrile seizures
  • Febrile seizures do NOT increase risk of serious bacterial illness[3]

Prognosis

  • Simple febrile seizures do NOT cause brain damage, developmental delay, or increase mortality
  • Risk of epilepsy: 2-3% (slightly higher than general population ~1%)
  • Recurrence risk:
    • 50% if first seizure at <12 months
    • 30% if first seizure at >12 months
  • Risk factors for recurrence: younger age, family history, lower peak temperature, shorter duration of fever before seizure

Clinical Features

Simple Febrile Seizure

  • Age 6 months to 5 years (peak 12-18 months)
  • Single seizure within 24 hours
  • Duration <15 minutes
  • Generalized with no focal features
  • Returns to neurologic baseline after brief postictal period
  • Cannot be classified as simple if: known CNS abnormalities, previous neurologic insults, or history of afebrile seizures

Complex Febrile Seizure

  • Any exception to the above criteria:
    • Duration ≥15 minutes
    • Focal features (one-sided jerking, eye deviation)
    • Recurrence within 24 hours
    • Prolonged postictal state or failure to return to baseline
  • May indicate more serious underlying disease process

Differential Diagnosis

  • The key question: Is this a seizure WITH fever, or a CNS INFECTION causing both seizure and fever?
  • Meningitis / encephalitis (must be excluded)
  • Status epilepticus
  • Epileptic seizure with intercurrent febrile illness
  • Pyridoxine-responsive seizures (infants)[4]
  • Shigella and other toxin-producing infections (seizures before fever)

Pediatric seizure

Pediatric fever

Evaluation

Simple Febrile Seizure

  • Neither labs nor neuroimaging are routinely necessary
  • Blood glucose in all patients
  • Normal pediatric fever workup as clinically indicated (source identification)
  • EEG is NOT indicated

Complex Febrile Seizure

  • Consider LP and CSF studies if:
    • Meningeal signs present
    • Child 6-12 months with incomplete immunizations[6]
    • Child had recent antibiotic treatment (may mask meningeal signs)
    • Clinician concern for CNS infection
  • Blood work: CBC, blood culture, UA, urine culture
    • Consider CMP if suspect hyponatremia from ongoing volume loss
    • Studies suggest link between iron deficiency anemia and febrile seizures[7]
  • CT head if:
    • Persistently abnormal neuro exam (especially focal findings)
    • Signs/symptoms of increased ICP
    • VP shunt
    • History of head trauma
    • Suspected neurocutaneous disorder
  • ECG: consider if family history of long QT, Brugada, or sudden death
  • EEG: NOT routinely indicated; consider only if developmental delay or focal symptoms

Causes Amenable to Specific Treatment

Management

Active Seizure

  • ABCs: position of safety, supplemental O2, suction
  • If fever: acetaminophen 15 mg/kg rectally
  • See Status epilepticus for seizure protocol if seizure does not self-terminate:
    • Benzodiazepines first-line:
      • Lorazepam 0.1 mg/kg IV (max 4 mg) if IV access
      • Midazolam 0.2 mg/kg IM/buccal (max 10 mg) if no IV
      • Rectal diazepam 0.5 mg/kg (max 20 mg) if no IV

Seizure Stopped

  • Treat underlying infection if indicated
  • See pediatric fever workup
  • Assess neurologic status — should return to baseline

Disposition

Discharge

  • Simple febrile seizure if patient at baseline
    • Follow-up in 1-2 days
    • Around-the-clock acetaminophen may prevent seizure recurrence during the same febrile episode[8]
    • Anticipatory guidance: emphasize benign nature while educating on return precautions
    • Prophylactic AEDs are NOT indicated for simple febrile seizures (AAP recommendation)
  • Complex febrile seizure if well-appearing, workup normal, follow-up in 24 hours

Admit

  • Ill-appearing
  • Lethargy beyond postictal period
  • Concern for CNS infection
  • Persistent or recurrent seizures

See Also

References

  1. ↑ https://www.ninds.nih.gov/disorders/patient-caregiver-education/fact-sheets/febrile-seizures-fact-sheet
  2. ↑ Mosili P, et al. The pathogenesis of fever-induced febrile seizures and its current state. Neurosci Insights. 2020;15:2633105520956973. PMID 33225279
  3. ↑ Trainor JL, et al. Children with first-time simple febrile seizures are at low risk of serious bacterial illness. Acad Emerg Med. 2001;8(8):781-7. PMID 11483452
  4. ↑ Baxter P et al. Pyridoxine-dependent and pyridoxine-responsive seizures. Dev Med Child Neurol. 2001;43:416-420. PMID 11409833
  5. ↑ Baxter P. et al. Pyridoxine‐dependent and pyridoxine‐responsive seizures. Developmental Medicine & Child Neurology 2001, 43: 416–42
  6. ↑ Subcommittee on Febrile Seizures; AAP. Neurodiagnostic evaluation of the child with a simple febrile seizure. Pediatrics. 2011;127(2):389-94. PMID 21285335
  7. ↑ Sulviani R, et al. Anemia and poor iron indices are associated with susceptibility to febrile seizures in children: systematic review and meta-analysis. J Child Neurol. 2023;38(3-4):186-197.
  8. ↑ Murata et al. Acetaminophen and febrile seizure recurrences during the same fever episode. Pediatrics. 2018;142(5):e20181009. PMID 30297498
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