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Febrile seizures

Last updated: August 9, 2021

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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: : 2nd 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:

International League Against Epilepsy (ILAE) classification of febrile seizures

Simple febrile seizure (∼75%) Complex febrile seizure* (∼25%)
Clinical presentation
  • Focal onset
  • Pronounced on one side of the body
  • Transient hemiparesis and speech impairment
Duration and frequency
  • < 15 min
  • Maximum of one seizure within 24 h

Age

  • 6 months to 5 years

  • More commonly outside the typical range of 6 months to 5 years

Postictal phase
  • Typically a quick return to normal
  • Confusion and drowsiness may be present for a short period of time
  • Prolonged drowsiness or deviated eyes may be a sign of other etiology (e.g., meningitis) or of ongoing seizure activity (see status epilepticus)
*Febrile seizures are considered complex if at least one of the criteria are met!

References:[1][2]

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]

References:[2][6]

  1. Millichap JJ. Clinical Features and Evaluation of Febrile Seizures. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/clinical-features-and-evaluation-of-febrile-seizures.Last updated: March 3, 2017. Accessed: March 29, 2017.
  2. Baumann RJ. Pediatric Febrile Seizures. In: Kao A, Pediatric Febrile Seizures. New York, NY: WebMD. http://emedicine.medscape.com/article/1176205. Updated: November 17, 2016. Accessed: May 11, 2017.
  3. Graves RC, Oehler K, Tingle LE. Febrile seizures: risks, evaluation, and prognosis. Am Fam Physician. 2012; 85 (2): p.149-153.
  4. Childhood Vaccines and Febrile Seizures. https://www.cdc.gov/vaccinesafety/concerns/febrile-seizures.html. Updated: June 20, 2016. Accessed: May 11, 2017.
  5. Subcommittee on Febrile Seizures. Febrile Seizures: Guideline for the Neurodiagnostic Evaluation of the Child With a Simple Febrile Seizure. Pediatrics. 2011; 127 (2): p.389-394. doi: 10.1542/peds.2010-3318 . | Open in Read by QxMD
  6. Millichap JJ. Treatment and Prognosis of Febrile Seizures. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. http://www.uptodate.com/contents/treatment-and-prognosis-of-febrile-seizures.Last updated: March 7, 2017. Accessed: May 11, 2017.