Overview
A febrile seizure is a seizure accompanied by fever (temperature higher than 38°C by any method), without central nervous system infection, which occurs in infants and children aged 6 months to 6 years.
Classification
Simple Febrile Seizures
- Isolated, generalized, tonic-clonic seizures
- Lasting less than 15 minutes
- No recurrence within 24 hours or within the same febrile illness
- Complete recovery within 1 hour
Complex Febrile Seizures
- Partial (focal) onset or focal features during the seizure
- Duration of more than 15 minutes
- Recurrence within 24 hours, or within the same febrile illness
- Incomplete recovery within 1 hour
Febrile Status Epilepticus
- Febrile seizure lasts for 30 minutes or longer
- Series of seizures without full recovery in between lasting 30+ minutes
- Medical emergency requiring immediate treatment
Causes and Risk Factors
The exact cause of febrile seizures is unknown, but is thought to be an age-dependent response of the immature brain to fever, in combination with underlying genetic and environmental factors.
Common Causes of Fever
- Viral infection — cause of fever in 80% of cases
- Human herpesvirus 6 (HHV-6) which causes roseola infantum
- Influenza
- Other infections
- Viral upper respiratory infections
- Otitis media
- Lower respiratory tract infection
- Urinary tract infection
- Gastroenteritis
- Post-immunisation (rare)
- Diphtheria-tetanus-pertussis vaccine
- Measles-mumps-rubella vaccine
Risk Factors for First Febrile Seizure
- Family history of febrile seizure in first-degree relatives
- Peak temperature (rather than rapidity of temperature rise)
- Zinc and iron deficiency
- About 50% of children have no identified risk factors
Clinical Features
Suspect a diagnosis of febrile seizure if a child has a fever or febrile illness and a reported or witnessed seizure.
Typical Features of Simple Febrile Seizure
- Child aged 6 months to 6 years
- Seizure usually lasts 2–3 minutes, rarely more than 10 minutes
- Generalized tonic-clonic type (muscle stiffening followed by rhythmical jerking or shaking of the limbs)
- Twitching of the face; rolling back of the eyes; staring and loss of consciousness
- Foaming at the mouth, difficulty breathing, pallor, or cyanosis
- Brief postictal period of drowsiness, irritability, or confusion
- Complete recovery within 1 hour
- May have had a previous febrile seizure
Red Flags for Serious Conditions
- Irritability, neck stiffness
- Petechial rash, photophobia
- Bulging fontanelle
- Decreased level of consciousness
- Prolonged post-ictal period
- Focal neurological deficit (lasting more than one hour)
Differential Diagnosis
With Fever
- CNS infection - bacterial meningitis, encephalitis
- Rigors or delirium (acute confusional state)
- Shivering (with or without fever)
- Febrile myoclonus
Without Fever
- Syncope
- Breath-holding spells or reflex anoxic seizures
- Head injury
- Hypoglycemia or other metabolic disorders
- Drug use or withdrawal
- Epilepsy
- Other neurological conditions (cerebral palsy, neurocutaneous syndromes)
Parental Advice and Education
Understanding Febrile Seizures
- Febrile seizures are not the same as epilepsy
- Risk of developing subsequent epilepsy is low (1-2%)
- Short-lasting seizures are not harmful to the child
- About 1 in 3 children will have another febrile seizure
- Risk reduces with age as the brain matures (rare beyond 6 years)
Management of Future Febrile Illness
- Intermittent use of antipyretics (paracetamol/ibuprofen) is not recommended for prevention
- Use antipyretics to reduce fever if the child is uncomfortable or distressed
- Ensure adequate hydration
- Complete all childhood immunisations, even if previous seizure followed immunisation
First Aid During a Seizure
Immediate Actions
- Monitor the duration of the seizure
- Protect the child from injury:
- Cushion their head with soft material
- Remove harmful objects from nearby
- Do not restrain the child or put anything in their mouth
- Check airway and place in recovery position after seizure stops
- Observe until full recovery
- Examine for and manage any injuries
When to Seek Emergency Help
- If tonic-clonic movements last more than 5 minutes
- Call an emergency ambulance
- Give emergency benzodiazepine if prescribed for recurrent seizures
Prognosis and Complications
Recurrence Risk
Following a first febrile seizure, approximately 30% of children will have recurrent seizures.
Risk Factors for Recurrence
- Early onset under 18 months of age
- Family history of febrile seizures or epilepsy in first-degree relative
- Low-grade fever associated with seizure onset (less than 39°C)
- Short duration of fever before the seizure (less than 1 hour)
- History of complex febrile seizure
- Multiple seizures in 24 hours or during the same febrile episode
- Prolonged febrile seizure (lasting more than 15 minutes)
- Attendance at day care nursery (increased viral exposure)
Possible Complications
- Parental/carer anxiety
- Febrile status epilepticus
- Epilepsy (slightly increased risk but still low)
- Cognitive impairment (very rare with simple febrile seizures)
Overall Prognosis
Febrile seizures are generally benign with a normal cognitive outcome. The vast majority of children outgrow them without any long-term consequences.