Febrile seizure: Difference between revisions

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== Background ==
==Background==
*2-3% chance of developing epilepsy (1% for general population)
*Seizure accompanied by fever (≥100.4°F / 38°C) in a child 6 months to 5 years without CNS infection or metabolic cause
*50% of pts never have temp >39
*Occur in 2-5% of children before age 5<ref>https://www.ninds.nih.gov/disorders/patient-caregiver-education/fact-sheets/febrile-seizures-fact-sheet</ref>
*50% of pts &lt;12 mo will have another simple febrile seizure
*Most common seizure type in childhood
*30% of pts &gt;12 mo will have another simple febrile seizure
*High temperatures alter ion channel function, increasing neuronal excitability<ref>Mosili P, et al. The pathogenesis of fever-induced febrile seizures and its current state. ''Neurosci Insights''. 2020;15:2633105520956973. PMID 33225279</ref>
*A high temperature is NOT necessarily seen in all febrile seizures
*'''Febrile seizures do NOT increase risk of serious bacterial illness'''<ref>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</ref>


==Clinical Presentation==
===Prognosis===
*[[Seizure]] + [[fever]]
*'''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


==Differential Diagnosis ==
==Clinical Features==
*[[Meningitis ]]
===Simple Febrile Seizure===
**More likely if [[status epilepticus]]
*Age 6 months to 5 years (peak 12-18 months)
*[[Seizure]] due to identifiable cause (e.g. intracranial mass, trauma, ingestion)
*Single seizure within 24 hours
*Epidural/subdural infection or hematoma
*Duration <15 minutes
*Toxic Ingestion
*Generalized with no focal features
*Pyridoxine Responsive Seizure<ref>Baxter P. et al. Pyridoxine‐dependent and pyridoxine‐responsive seizures. Developmental Medicine & Child Neurology 2001, 43: 416–42</ref>
*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


==Diagnosis==
===Complex Febrile Seizure===
=== Simple versus Complex ===
*Any exception to the above criteria:
*Simple
**Duration ≥15 minutes
**Generalized tonic-clonic seizure
**Focal features (one-sided jerking, eye deviation)
**&lt;15 min in duration
**Recurrence within 24 hours
**Age 6mo - 6yr
**'''Prolonged postictal state''' or failure to return to baseline
**Occurs only once in 24hr period
*May indicate more serious underlying disease process
**No focal features
*Complex
**Any exception to above


===Work-Up===
==Differential Diagnosis==
*Glucose in all pts
*The key question: Is this a seizure WITH fever, or a CNS INFECTION causing both seizure and fever?
*Simple febrile seizure  
*[[Meningitis]] / [[encephalitis]] (must be excluded)
**Neither labs nor neuroimaging are absolutely necessary
*[[Status epilepticus]]
**Normal [[Fever (Peds)|pediatric fever workup]]
*Epileptic seizure with intercurrent febrile illness
*Complex febrile seizure
*Pyridoxine-responsive seizures (infants)<ref>Baxter P et al. Pyridoxine-dependent and pyridoxine-responsive seizures. ''Dev Med Child Neurol''. 2001;43:416-420. PMID 11409833</ref>
**Consider CBC, blood cx, UA, Ucx, CSF studies
*[[Shigella]] and other toxin-producing infections (seizures before fever)
*Consider CT if:  
**Persistently abnormal neuro exam (esp w/ focality)  
**Signs/symptoms of increased ICP
**pt has VP shunt
*Routine EEG not indicated
**Consider only if developmental delay or for focal symptoms


== Treatment  ==
{{Pediatric seizure DDX}}
*Treat if initial seizure persists &gt;5 min or for subsequent seizures
{{Pediatric fever DDX}}
**[[Benzodiazepines]]
***[[Lorazepam]] 0.1mg/kg IV
***[[Diazepam]] 0.2 mg/kg IV or 0.5 mg/kg PR (choice if difficult or no access)
***[[Midazolam]] 0.1 mg/kg IV or IM or IN
****If persists try one additional dose (risk of resp. depression incr if &gt;2 doses)
**[[Fosphenytoin]] (15-20 mg PE/kg IV) or [[Phenytoin]] (10-20 mg/kg IV up to 1g @ 1mg/kg/min)
***Treat if seizure persists despite benzo treatment
***Onset of action may take as long as 30 minutes
***Can cause [[hypotension]] and [[dysrhythmias]]
**[[Barbituates]]
***[[Phenobarbital]] 15-20 mg/kg IV
***Consider only if benzos and phenytoin have failed
***May lead to respiratory depression, especially when preceded by a benzo
**[[Valproic acid]] 10-15 mg/kg IV (20 mg/min)
***Has been shown to be effective when benzos, phenytoin, and barbituates have failed
***Can be used as 2nd or 3rd-line treatment
**[[Keppra]] 20 mg/kg IVP
**[[Propofol]] 2-3 mg/kg IVP; maintenance 0.125-0.3 mg/kg/min IV
**Consider [[Pyridoxine]] (vitamin B6) 1g per g of INH ingested  (in D5W IV over 30 min)
**Consider Pyridoxine Responsive Seizure Disorder - 100mg/pyridoxine is generally effective<ref>Pyridoxine dependent seizures a wider clinical spectrum. Archives of Disease in
Childhood.1983 (58) 415-418. http://adc.bmj.com/content/58/6/415.full.pdf</ref>
*Treat underlying infection


== Disposition  ==
==Evaluation==
*Discharge
===Simple Febrile Seizure===
**Simple febrile seizure if pt at baseline
*Neither labs nor neuroimaging are routinely necessary
***Follow-up in 1-2d
*Blood glucose in all patients
**Complex febrile seizure if pt well-appearing, work-up normal
*Normal pediatric [[fever]] workup as clinically indicated (source identification)
***Follow-up in 24hr
*EEG is NOT indicated
*Admit:
**Ill-appearing
**Lethargy beyond postictal period


== See Also  ==
===Complex Febrile Seizure===
*[[Seizure]]
*Consider LP and CSF studies if:
*[[Fever (Peds)]]
**Meningeal signs present
**Child 6-12 months with incomplete immunizations<ref>Subcommittee on Febrile Seizures; AAP. Neurodiagnostic evaluation of the child with a simple febrile seizure. ''Pediatrics''. 2011;127(2):389-94. PMID 21285335</ref>
**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<ref>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.</ref>
*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


== Source  ==
===Causes Amenable to Specific Treatment===
*[[Hypoglycemia]], [[hyponatremia]] (water intoxication, formula dilution), [[hypocalcemia]], [[hypomagnesemia]], [[isoniazid]] ingestion
 
==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 [[Fever (peds)|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<ref>Murata et al. Acetaminophen and febrile seizure recurrences during the same fever episode. ''Pediatrics''. 2018;142(5):e20181009. PMID 30297498</ref>
**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==
*[[Seizure (peds)]]
*[[Fever (peds)]]
*[[Status epilepticus]]
*[[Meningitis]]
 
==References==
<references/>
<references/>


[[Category:Peds]]
[[Category:Pediatrics]]
[[Category:Neuro]]
[[Category:Neurology]]

Latest revision as of 09:26, 22 March 2026

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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