Febrile seizure

I. DEFINITION

• Febrile Seizure (FS): A seizure occurring in children aged 6 months to 5 years (some guidelines extend to 3 months or 6 years), associated with a temperature ≥38°C (100.4°F), not resulting from CNS infection, metabolic/electrolyte imbalance, or a history of prior afebrile seizures.
• Peak Incidence: 12–18 months of age.

II. CLASSIFICATION

1. Simple Febrile Seizure (80%): - Primary generalized tonic-clonic seizure.
   • Duration <15 minutes.
   • No recurrence within 24 hours.
   • Short post-ictal phase with rapid return to baseline.
2. Complex Febrile Seizure (20%):
   • Focal onset or lateralizing features.
   • Prolonged duration ≥15 minutes.
   • Recurrence within 24 hours.
3. Febrile Status Epilepticus (FSE):
   • Continuous or cluster of seizures lasting ≥30 minutes without recovery of consciousness.
4. FIRES (Febrile Infection-Related Epilepsy Syndrome):
   • Explosive onset of refractory status epilepticus in older children (>5 years) following a febrile illness, often with poor neurologic outcomes.

III. ETIOPATHOGENESIS

• Genetics: Often polygenic; 25–40% have a positive family history. Known single gene associations include SCN1A, SCN1B, and GABRG2.
• Cytokines: Dysregulation between pro-inflammatory (IL-1β, IL-6) and anti-inflammatory (IL-1Ra) cytokines. IL-1β acts as both a pyrogen and an NMDA agonist.
• Environmental: Associated with viral infections (HHV-6B, HHV-7, influenza, roseola), immunizations (DTP, MMR), and iron deficiency.

IV. CLINICAL EVALUATION

1. History: Focus on seizure semiology (focal vs. generalized), duration, fever onset, and post-ictal state. Assess family history and developmental status.
2. Examination: - Search for extracranial focus (Otitis media, pharyngitis, UTI).
   • Neurologic: Check for meningeal signs (Kernig’s/Brudzinski’s - unreliable <12 months), fontanelle tension, and focal deficits.
3. Red Flags: Persistent altered sensorium (>1 hour post-seizure), petechial rash, bulging fontanelle, or focal neurological signs.

V. INVESTIGATIONS

1. Lumbar Puncture (LP):
   • Mandatory: Clinical signs of meningitis (nuchal rigidity, etc.).
   • Consider: Infants 6–12 months if immunization status (Hib/Pneumococcal) is incomplete/unknown or if the child is on antibiotics (may mask signs).
2. Blood Studies: Not routine for simple FS. Check glucose if prolonged post-ictal state. Electrolytes indicated only if history of dehydration/vomiting.
3. Neuroimaging (CT/MRI): Not recommended for simple FS. Consider for complex FS with focal features or persistent neurologic abnormality.
4. EEG: Not predictive of recurrence or future epilepsy in simple FS. May be indicated in complex FS or if epilepsy is strongly suspected.

VI. MANAGEMENT

1. Acute Seizure Management (domicillary):
   • Position in lateral decubitus, secure airway, monitor vitals.
   • If seizure >5 minutes:
     • IV Lorazepam (0.1 mg/kg) or IV Midazolam (0.1–0.2 mg/kg).
     • Alternatives: IM Midazolam (0.2 mg/kg) or Rectal Diazepam (0.3–0.5 mg/kg).
2. Fever Management: Antipyretics (Paracetamol 15 mg/kg or Ibuprofen 10 mg/kg) improve comfort but do not prevent FS recurrence.
3. Prophylaxis:
   • Continuous: Phenobarbital or Valproate generally not recommended due to side effects and lack of benefit in preventing future epilepsy.
   • Intermittent: For frequent recurrences or parental anxiety, oral Diazepam (0.3 mg/kg 8-hourly) or Clobazam may be given at the onset of fever for 48 hours.
4. Parental Counseling: Explain the benign nature, low mortality risk, and high recurrence rate. Provide a rescue medication plan.

VII. PROGNOSIS

Recurrence Percentages

• Overall Recurrence: Approximately 30% (one-third) of patients experience recurrent febrile seizures.
• Multiple Recurrences: 1/6th of patients experience multiple febrile seizures.
• Age-Specific Risk: 50% recurrence risk if onset occurs before 1 year of age.
• Post-Recurrence Risk: 50% recurrence risk after experiencing two or more episodes.

Risk-Stratified Recurrence Rates

Risk Factors for Recurrence

Risk of Subsequent Epilepsy

Overall risk of developing epilepsy by adolescence is 3–12%.