Seizures, Febrile – Causes, Symptoms, Diagnosis, Treatment and Ongoing care

Basics

Description

A seizure occurring between the ages of 6 months and 6 years of age associated with a febrile illness that does not involve CNS infection or inflammation in a child that has no prior history of afebrile seizures; febrile seizures are classified as either simple or complex.

  • Simple (70–75%):
    • Duration <15 minutes
    • Generalized seizure with no focal features
    • No recurrence in 24 hours
  • Complex (9–35%):
    • Duration >15 minutes
    • Focal features
    • >1 seizure in 24 hours

Epidemiology

Febrile seizures (FS) are the most common seizures in children under age 5. They typically occur between the ages of 6 months and 36 months (peak at 18 months) (1)[B].

Incidence

  • ∼500,000 febrile seizures occur yearly in the US (1)[B].
  • Incidence is between 2% and 5%.

Prevalence

3–4% of all children in North America will experience a febrile seizure before age 5 years (most of which are simple) (1)[B].

Risk Factors

  • For 1st febrile seizure (1)[B]:
    • Family history of febrile or afebrile seizures
    • Neurodevelopmental abnormality
    • Recent immunizations (increased risk following DTP and MMR)
    • Most children will have no identifiable risk factors.
    • Possible increased risk with certain viral illnesses, including human herpesvirus type 6 (HHV-6) infection
  • For recurrent FS (1)[B]:
    • Onset at age <12 months
    • Family history of FS in 1st-degree relative
    • Temperature <40°C (104°F) with prior FS
    • Complex FS at initial presentation
    • Brief duration between fever onset and seizure
  • For subsequent epilepsy after FS (1–2.4%, slightly increased risk over that of general population) (2)[B]:
    • Family history of epilepsy
    • Complex FS
    • Neurodevelopmental abnormality

Genetics

  • Genetic factors play role, with susceptibility being linked to several genetic loci.
  • A history of FS in immediate family members is present in 10–40% of patients.
  • Monozygotic twins have a much higher concordance rate than dizygotic twins.
  • Sodium channels and γ-aminobutyric acid A (GABAA) receptor genes have been associated with a syndrome of generalized epilepsy and FS (GEFS+) (3).

General Prevention

  • Evidence exists that anticonvulsant therapy can reduce the risk of recurrence of FS, but it is not recommended because the harm significantly outweighs the benefits.
  • Antipyretics help to improve comfort of the child, but neither regular dosing intervals (e.g., acetaminophen every 4 hours) nor sporadic dosing based on temperature has been shown to prevent recurrence (2)[B].

Pathophysiology

The underlying pathophysiology is unknown.

Etiology

  • Any viral or bacterial infections can provoke FS.
  • Increased risk found with HHV-6 infection (also found to have increased risk of complex FS and recurrence).
  • MMR vaccine has been associated with an up to 3-fold increased risk of FS, with peak incidence 1–2 weeks after vaccination, but benefit of vaccination outweighs risk.
  • DTP vaccine also has been associated with a 4-fold increase risk of FS, with peak incidence 1–3 days after vaccination, but vaccine benefit outweighs risk (1)[B].

Diagnosis

History

  • Description of convulsions, including any focal movements (seizures are typically clonic)
  • Duration of seizure
  • Interventions performed to control seizures (most will resolve spontaneously)
  • History of recent illness or fever (though seizure often can be 1st presenting symptom)
  • Signs of CNS infection or inflammation (e.g., lethargy, irritability, decreased feeding, emesis)
  • Recent immunization
  • Patient and family history of seizures
  • Recent treatment with antibiotics (meningitis can be masked if partially treated)
  • Evaluate for other causes of seizures, such as trauma or toxin exposure.

Physical Exam

  • Vital signs:
    • Fever
    • Monitor for respiratory or circulatory compromise (if persistent seizure activity).
  • Full neurological exam:
    • Usually normal
    • May have transient decreased alertness in postictal state; monitor for improvement.
  • Focused exam based on history to determine source of fever

Diagnostic Tests & Interpretation

Lab

  • AAP recommendations for 1st simple FS: Lumbar puncture (LP) should be strongly considered in children <12 months of age; considered in children between 12 and 18 months of age; and recommended in children >18 months of age in the presence of clinical suspicion for meningitis (4)[A]. Recent evidence shows that the risk of bacterial meningitis is very low with 1st simple FS, and AAP recommendations should be reconsidered (5)[A].
  • CSF more likely to show abnormalities when (4)[A]:
    • Abnormal physical exam
    • Complex FS
    • Persistent seizures on arrival to emergency department
    • Prolonged postictal state
  • In practice, the decision to perform LP should be tailored to each individual child’s presentation.

Pediatric Considerations

In infants <18 months of age, clinical signs and symptoms of meningitis may be minimal or absent.

Initial lab tests

  • Measurement of serum electrolytes, calcium, phosphorous, magnesium; complete blood count (CBC); and serum glucose determination are low-yield and should not be performed routinely unless clinically indicated.
  • Obtain serum glucose if there is a prolonged postictal state or recurrent seizures (4)[A].
  • Laboratory testing should be obtained based on history to detect source of fever (4)[A].

Imaging

Initial approach

  • Routine neuroimaging is not indicated in the evaluation of simple FS (4)[A].
  • Neuroimaging should be performed if the physical exam points to a possible structural lesion (e.g., micro/macrocephaly, focal neurologic signs, symptoms of increased intracranial pressure).

Diagnostic Procedures/Surgery

  • EEG is not recommended as part of evaluation of a neurologically healthy child with a 1st simple FS (4)[A]. EEG does not predict the recurrence of FS or the development of epilepsy.
  • EEG is recommended in children with complex FS who have developmental delay or abnormal neurologic signs and symptoms.

Differential Diagnosis

  • Rigors
  • Syncope
  • Febrile delirium (acute and transient confusional state associated with high fever)
  • Breath-holding spell
  • Meningitis

Treatment

Medication

First Line

  • Acute treatment:
    • Anticonvulsants: Febrile seizures lasting >5 minutes should be treated with anticonvulsants (2)[B].
      • Lorazepam: 0.05–0.1 mg/kg IV
      • Diazepam: 0.3 mg/kg IV
    • Rectal gel (Diastat): 0.5 mg/kg; fosphenytoin: Use for persistent seizures, rare.
    • IV: 15–20 mg/kg
    • Antipyretics: Use acutely to reduce fever.
      • Acetaminophen: 15 mg/kg p.o. PR
      • Ibuprofen: 10 mg/kg p.o.
  • Long-term treatment (2)[B]:
    • Anticonvulsants may be effective in reducing FS, but the potential side effects outweigh the benefits; therefore, anticonvulsant therapy is not recommended routinely for children with FS.
    • Antipyretics may be given for comfort but have not been shown to reduce the risk of FS.

Second Line

Cooling blankets to reduce fever as needed

Additional Treatment

General Measures

  • Treat source of fever based on results of focused evaluation.
  • Supportive care as needed

Issues for Referral

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Refer to pediatric neurologist if suspicious for underlying seizure disorder or complex FS.

In-Patient Considerations

Initial Stabilization

  • Assessment of airway, breathing, and circulatory status (ABCs)
  • Febrile seizures of >5 minutes duration should be treated as outlined under “Acute Treatment.”

Admission Criteria

Admission should be strongly considered if

  • Age <1 year
  • Glasgow coma scale <15 (1 hour following seizure)
  • Shows signs of increased intracranial pressure
  • Demonstrates clinical suspicion for meningitis
  • Has experienced a complex partial seizure
  • Demonstrates any instability in vital signs

IV Fluids

If child appears dehydrated, administer IV fluid as appropriate.

Nursing

  • Nursing should be carried out according to the patient’s underlying illness or infection.
  • Precautionary measures to prevent secondary injuries from seizure activity

Discharge Criteria

Children with simple FS, no focal signs of infection, and appearing well can be discharged home after a minimum of 2 hours of observation.

Ongoing Care

Follow-Up Recommendations

For any patient with simple FS, a follow-up appointment with the primary-care physician should be scheduled within 1 week of discharge. Follow-up for complex FS should be made pending results of further evaluation.

Patient Monitoring

Monitor as appropriate depending on clinical presentation of patient (including classification of FS).

Diet

No dietary restrictions necessary

Patient Education

Parental education is important owing to the significant anxiety surrounding the diagnosis (1)[B].

  • FS are common and occur in 3–5% of otherwise healthy children.
  • FS can recur in approximately 1/3 of children with subsequent fevers.
  • No evidence suggests that FS cause neurologic sequelae or death.
  • Evaluation depends on the clinical presentation, and there is no role for routine lab testing or imaging.
  • Treatment of FS is not generally recommended and has not been shown to prevent the development of epilepsy.
  • Referral to a pediatric neurologist is not typically required for a simple FS.

Prognosis

  • Overall excellent prognosis
  • No evidence of neurodevelopmental problems, learning disabilities, or increased mortality with simple FS
  • Children with FS are at risk for developing recurrent FS.
    • Children >12 months of age have a 30% rate of recurrence. Those who have 2nd FS have a 50% risk of having additional episodes.
    • Children <12 months of age have increased recurrence rate of 50%.
  • Risk of epilepsy after a simple FS is slightly greater than that of general population, which is approximately 1%.
    • Risk of epilepsy after multiple simple FS with 1st seizure at <1 year of age is 2.4%.
    • Factors that increase risk of epilepsy include neurodevelopmental abnormality, complex FS, and family history of epilepsy (2)[B].

Complications

  • Secondary complications include injuries resulting from seizure activity, aspiration, and complications from prolonged seizures with complex FS (1)[B].
  • There is controversial evidence that FS may contribute to temporal lobe epilepsy.

References

1. Jones T, Jacobsen SJ. Childhood febrile seizures: overview and implications. Int J Med Sci. 2007;4:110–4.

2. Steering Committee on Quality Improvement and Management, Subcommittee on Febrile Seizures American Academy of Pediatrics. Febrile seizures: clinical practice guideline for the long-term management of the child with simple febrile seizures. Pediatrics. 2008;121:1281–6.

3. Scheffer IE, Harkin LA, Dibbens LM, et al. Neonatal epilepsy syndromes and generalized epilepsy with febrile seizures plus (GEFS+). Epilepsia. 2005;46(Suppl 10):41–7.

4. Practice parameter: the neurodiagnostic evaluation of the child with a first simple febrile seizure. American Academy of Pediatrics. Provisional Committee on Quality Improvement, Subcommittee on Febrile Seizures. Pediatrics. 1996;97:769–72; discussion 773–5.

5. Kimia AA, Capraro AJ, Hummel D, et al. Utility of lumbar puncture for first simple febrile seizure among children 6 to 18 months of age. Pediatrics.2009;123:6–12.

Codes

ICD9

780.31 Febrile convulsions (simple), unspecified

Snomed

41497008 febrile convulsion (finding)

Clinical Pearls

  • FS is common and accounts for 1% of all pediatric emergency department visits.
  • Keystone of evaluation and treatment of FS involves identifying and treating underlying illness.
  • Thorough neurodiagnostic workup (including EEG, imaging, and LP) typically is not necessary.
  • FS are associated with only slightly increased risk of epilepsy compared with general population.
  • There is no need for preventive or long-term treatment of FS.

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