Febrile seizures

Introduction

Febrile seizures are generalized convulsions that occur in association with fever in infants and young children, typically between 6 months and 5 years of age, without evidence of intracranial infection, metabolic disturbance, or a history of afebrile seizures. They are the most common type of seizures in this age group and are generally benign, although their occurrence is alarming to caregivers.

While most febrile seizures are self-limiting and do not cause long-term neurological damage, they can be classified into simple and complex forms, with different implications for recurrence and future epilepsy risk.

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Epidemiology

• Prevalence: Affect approximately 2–5% of children in developed countries; higher in some Asian populations.

• Age distribution: Most occur between 18 months and 2 years.

• Sex: Slightly more common in males.

• Recurrence: About 30–35% will have at least one recurrence.

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Etiology and Pathophysiology

Primary Triggers

• Rapid rise in body temperature (often at the onset of febrile illness).

• Common infections: upper respiratory tract infections, otitis media, roseola infantum, influenza, gastroenteritis.

• Post-vaccination fevers (e.g., after measles–mumps–rubella vaccination).

Pathophysiological Mechanisms

• Immature brain neuronal excitability: Young children have a lower seizure threshold.

• Genetic predisposition: Family history in 25–40% of cases; mutations in sodium channel genes (SCN1A, SCN1B) associated with febrile seizure susceptibility.

• Cytokine-mediated fever: Pro-inflammatory cytokines during infection increase neuronal excitability.

• Hyperthermia effects: Rapid temperature elevation can destabilize neuronal membranes.

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Risk Factors

• First-degree family history of febrile seizures.

• First febrile seizure before 18 months of age.

• Low degree of fever at the time of seizure.

• Short interval between fever onset and seizure.

• Daycare attendance (increased infection exposure).

• Certain vaccinations in susceptible children.

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Classification

1. Simple Febrile Seizures

• Generalized tonic-clonic seizures.

• Duration < 15 minutes.

• Occur once in 24 hours.

• No focal features or postictal neurological deficit.

2. Complex Febrile Seizures

• Duration > 15 minutes.

• Focal onset or features.

• Occur more than once within 24 hours.

• May have transient postictal weakness (Todd’s paresis).

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Clinical Features

• Onset: Often during the initial rise of fever (>38°C).

• Seizure activity: Generalized tonic–clonic movements, eye rolling, loss of consciousness.

• Postictal state: Sleepiness, confusion; usually resolves within 30–60 minutes.

• Fever source: Often due to viral or bacterial infection, which should be investigated.

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Differential Diagnosis

• Meningitis or encephalitis.

• Epilepsy.

• Hypoglycemia.

• Electrolyte imbalance.

• Intracranial hemorrhage.

• Febrile status epilepticus.

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Evaluation

History and Examination

• Detailed seizure description, duration, and focality.

• Fever onset and progression.

• Past medical and family history.

• Recent vaccinations.

• Symptoms suggesting CNS infection (neck stiffness, altered consciousness).

Investigations

• Simple febrile seizures in well-appearing children usually do not require extensive testing.

• Lumbar puncture:

  • Indicated if meningitis is suspected.

  • Consider in children <12 months old if immunization status incomplete.

• Blood tests (CBC, electrolytes, glucose): If clinically indicated.

• Neuroimaging: Reserved for atypical presentations or focal neurological signs.

• EEG: Not routinely recommended; may be considered in recurrent complex febrile seizures with atypical features.

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Management

Acute Seizure Care

• Protect airway, breathing, and circulation.

• Place child in recovery position to prevent aspiration.

• Loosen clothing; ensure safety from injury.

• Monitor oxygen saturation and provide supplemental oxygen if needed.

If seizure > 5 minutes:

• Benzodiazepines are first-line:

  • Diazepam (rectal) – 0.5 mg/kg (max 10 mg).

  • Lorazepam (IV) – 0.1 mg/kg (max 4 mg).

  • Midazolam (buccal/intranasal) – 0.3 mg/kg.

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Post-Seizure Management

• Identify and treat the underlying cause of fever (antibiotics for bacterial infection, antipyretics for comfort).

• Antipyretics (paracetamol, ibuprofen) do not prevent recurrence but improve comfort.

  • Paracetamol: 15 mg/kg every 4–6 hours.

  • Ibuprofen: 10 mg/kg every 6–8 hours (avoid in dehydration).

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Prevention of Recurrence

• Intermittent prophylaxis (for recurrent prolonged febrile seizures):

  • Diazepam oral or rectal during febrile illness: 0.3 mg/kg every 8 hours for 48–72 hours.

• Continuous prophylaxis (rarely used, only for high-risk recurrent complex febrile seizures):

  • Phenobarbital: 3–5 mg/kg/day in divided doses.

  • Valproic acid: 20–30 mg/kg/day in divided doses.

  • Continuous prophylaxis is generally avoided due to side effects and minimal long-term benefit.

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Prognosis

• Most children recover completely without neurological sequelae.

• Recurrence risk: 30–35% overall; higher if first seizure occurs before 18 months.

• Epilepsy risk: Slightly increased (2–7%) compared to general population (<1%).

  • Higher risk with complex febrile seizures, family history of epilepsy, or abnormal neurodevelopment.

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Parental Education

• Febrile seizures are common and usually harmless.

• Prompt but calm response during seizure.

• Avoid restraining the child or putting objects in the mouth.

• Seek medical attention after the first episode or if features are atypical.

• Call emergency services if seizure lasts more than 5 minutes.