Febrile seizure: Difference between revisions
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==Background==
==Background==
Criteria:  Seizure + temp >38 in pt age 6 mo - 6 yr without previous afebrile seizure  
*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<ref>https://www.ninds.nih.gov/disorders/patient-caregiver-education/fact-sheets/febrile-seizures-fact-sheet</ref>
*Most common seizure type in childhood
*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>


==Diagnosis==
===Prognosis===
===Simple versus complex===
*'''Simple febrile seizures do NOT cause brain damage, developmental delay, or increase mortality'''
# Simple  
*Risk of epilepsy: 2-3% (slightly higher than general population ~1%)
##<15 min in duration
*Recurrence risk:
## No focal features
**50% if first seizure at <12 months
## Only a single episode in 24 hours
**30% if first seizure at >12 months
# Complex
*Risk factors for recurrence: younger age, family history, lower peak temperature, shorter duration of fever before seizure
## Any exception to above


===Risk Factors===
==Clinical Features==
# Family history (2-4x higher)
===Simple Febrile Seizure===
# Infection (viral and bacterial)
*Age 6 months to 5 years (peak 12-18 months)
# Recent vaccinations
*Single seizure within 24 hours
# Recurrence
*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


==Diagnosis/Work-Up==
===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)<ref>Baxter P et al. Pyridoxine-dependent and pyridoxine-responsive seizures. ''Dev Med Child Neurol''. 2001;43:416-420. PMID 11409833</ref>
*[[Shigella]] and other toxin-producing infections (seizures before fever)


* Consider trauma, toxidromes, infection/ petechiae
{{Pediatric seizure DDX}}
* Glucose check
{{Pediatric fever DDX}}
* if sz >5 min tx with IM, IV, IN Versed 
* Consider trauma or toxic cause
* Classifly as simple or comple
* Search for devel delay, fam hx,
* Physical exam should focus on source of fever
* Routine lab tests other than blood glucose not needed unless searching for cause of fever (UA, CBC, CXR, etc)
* Consider LP if:
* Age <12 mo (AAP guidelines)
* However, bacterial meningitis is rarely the diagnosis if it not clinically suspected
* Seizure occurs after the second day of illness
* Concern for CNS infection
* Febrile status epilepticus
* Pmd visit w/ in 48 hrs
* Sz in ED
* Focal sz
* Abnormal neuro/ phys exam
* Irritable, poor feeding
* Complex features
* Slow postictal clearance
* Pretreated with abx (consider partially tx meningitis if already on abx)
* CT if:
* Persistently abnormal neuro exam (especially with focal features)
* Signs/symptoms of increased ICP
* Consider for presence of VP shunt
* Routine EEG not indicated
* Consider only if developmental delay or for focal symptoms


==DDx==
==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<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


* Meningitis
===Causes Amenable to Specific Treatment===
* More likely in patients with status epilepticus
*[[Hypoglycemia]], [[hyponatremia]] (water intoxication, formula dilution), [[hypocalcemia]], [[hypomagnesemia]], [[isoniazid]] ingestion
* Seizure due to identifiable cause (e.g. intracranial mass, trauma)
* Epidural/subdural infection or hematoma


==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 if initial seizure persists >5 min or for subsequent seizures
*Treat underlying infection if indicated
* Benzodiapazines
*See [[Fever (peds)|pediatric fever workup]]
* Lorazepam (0.05 - 0.1mg/kg)
*Assess neurologic status — should return to baseline
* If seizure persists try one additional dose (risk of resp. depression incr if >2 doses)
* Effective duration of action is up to 4-6 hours
* Midazolam (0.1-0.3mg/kg)
* Diazepam
* Compared to lorazepam, less effective and more respiratory depression
* Fosphenytoin (15-20 mg/kg)
* Treat if seizure persists despite benzo tx
* Onset of action may take as long as 30 minutes
* Can cause hypotension and dysrhythmias
* Barbituates
* Consider only if benzos and phenytoin have failed
* May lead to respiratory depression, especially when preceded by a benzo
* Valproic acid
* Has been shown to be effective when benzos, phenytoin, and barbituates have failed
* Can be used as 2nd or 3rd-line treatment
* Propofol
* Treat underlying infection


==Disposition==
==Disposition==
* Home:  Simple febrile seizure and patient back at baseline with follow up in 1-2 days
===Discharge===
* Admit: Complex febrile seizures, lethargy beyond postictal period, uncertain home situation
*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


==Prognosis==
===Admit===
Risk of recurrence:
*Ill-appearing
** If first seizure occurs in age <1yr  = 50%
*Lethargy beyond postictal period
**If first seizure occurs in age 1-3yr = 25%
*Concern for CNS infection
** If first seizure occurs in age >3yr = 12%
*Persistent or recurrent seizures
* Majority of recurrences occur within 1st year; almost all occur within 2 years
 
Risk factors for recurrence include:
# Young age at onset
# Family history of febrile seizures
# Low-degree of fever in the ED
# Brief duration between onset of fever and initial seizure
# Complex febrile seizure does not increase risk of recurrent seizures


==See Also==
==See Also==
Seizure (Peds)
*[[Seizure (peds)]]
 
*[[Fever (peds)]]
Fever (Peds)
*[[Status epilepticus]]
 
*[[Meningitis]]
 
==Source==
 
 
Adapted from Gausche, Mistry, Donaldson, Pani, UpToDate
 
 


==References==
<references/>


[[Category:Peds]]
[[Category:Pediatrics]]
[[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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