Febrile seizures

Febrile seizures are one of the most common pediatric emergencies and are usually associated with high fever in children between six months and five years of age. The exact pathophysiology is unknown. Simple febrile seizures are the most common type; they are usually generalized, last under 15 minutes, and do not recur within 24 hours. Complex febrile seizures have a focal onset, last longer than 15 minutes, or recur within 24 hours. Diagnostic examination of simple febrile seizures focuses on addressing the cause of fever. Further diagnostics are required for patients with complex febrile seizures, particularly to exclude herpes encephalitis, and include lumbar puncture, CT scan, and/or EEG. Most febrile seizures end spontaneously and do not require any treatment. If seizures persist for longer than five minutes or present as complex febrile seizures, however, IV benzodiazepines are the treatment of choice. Caregivers should be reassured as the prognosis of febrile seizures is good, with the risk of epilepsy being less than 10%.

Febrile seizures are seizures that are associated with fever; (mainly temperatures exceeding 38°C (100.4°F) in the absence of CNS infection, metabolic abnormalities, or a history of afebrile seizures.

References:^[1][2][3]

• Peak incidence: : 2^nd year of life; most commonly occurs between 6 months and 5 years of age
• Prevalence: Febrile seizures occur in ∼ 4% of all children.

References:^[4]

Epidemiological data refers to the US, unless otherwise specified.

The exact pathophysiological mechanisms of febrile seizures are not known. Risk factors:

• Genetic predisposition
• High fever (> 40°C (104°F))
• Viral infection (e.g., HHV-6, influenza)
• Recent immunization (especially MMR and DTaP)

References:^[1][2]

• Approach
  • Simple febrile seizures do not require specific diagnostic workup
  • Diagnostic examination focuses on identifying the cause of fever
  • Complex febrile seizures always require specific investigative tests (e.g., EEG and imaging).
• Determine the cause of fever
  • Physical examination
  • Urinalysis and urine cultures
  • Consider blood tests (CBC with differential blood, CRP, electrolytes, blood glucose)
  • Consider imaging to locate the source of infection (ultrasound, X-ray)
  • In suspected cases of intoxication: toxicology screen
• Additional diagnostic steps: for complex febrile seizures and/or abnormal neurological examination
  • Lumbar puncture
    • To exclude meningitis and/or (herpes) encephalitis ^[5]
  • EEG
  • Imaging (e.g., CT or MRI)

References:^[1][2]

Uncomplicated seizures usually resolve after a few minutes spontaneously. However, abortive therapy should be administered if seizures ≥ 5 min or complex.

• Abortive therapy
  • Treatment of choice: IV lorazepam
  • Alternative: IV diazepam, buccal/intranasal midazolam (when IV access is not possible)
  • If necessary, repeat medication after 5 min
  • Additional measures are needed with status epilepticus
• Reassure caregivers and provide information
• After a febrile seizure, initiate antipyretic therapy (NSAIDs and acetaminophen) at an early stage (temperatures from 38°C (100.4°F)) as they restore the central thermoregulatory setpoint back to normal by reducing the synthesis of prostaglandin E2.

Febrile seizures primarily occur during the rise in temperature; therefore, prophylactic measures are often too late because a seizure cannot be anticipated! Long-term continuous or intermittent prophylaxis with anticonvulsant drugs (e.g., phenobarbital) or diazepam is not recommended.

References:^[3]

• The risk of recurrent, simple febrile seizures is 30%.
• Risk of developing epilepsy:
  • ∼ 1–2% in children who have had a simple febrile seizure
  • 5–10% in children with complex febrile seizures or a family history of epilepsy
• Risk factors for recurrence:
  • Initial complex febrile seizure
  • Family history of febrile seizures
  • Initial febrile seizure with temperature < 40°C
  • Age of onset < 18 months ^[5]
  • Structural brain lesions, cerebral palsy

References:^[2][6]