Seizures - febrile
Red flags
- Age <6 months or >6 years at first febrile seizure - atypical, work up further
- Meningism, bulging fontanelle, reduced consciousness beyond expected post-ictal period -> CNS infection until excluded
- Focal seizure features, prolonged (>15 min), or >1 seizure in 24h -> complex febrile seizure
- Incomplete recovery to neurological baseline
- Immunosuppression or recent antibiotic use masking meningitis signs
Differential by mechanism
Simple febrile seizure (majority, ~2-5% of children)
- Generalised, <15 minutes, single episode in 24h, full recovery, normal neurology between episodes
- Triggered by rate of temperature rise, not absolute height; commonly viral illness
Complex febrile seizure
- Focal features, duration >15 min, or recurrence within 24h - higher risk of underlying pathology and future epilepsy
Must-exclude mimics/causes of fever + seizure
- Meningitis/encephalitis - the critical differential, especially if any complex feature or delayed recovery
- Febrile delirium/rigors without true seizure
- Breath-holding spells (afebrile, different mechanism, consider if history atypical)
Focused history
- Age, prior febrile seizures, family history of febrile seizures/epilepsy
- Fever source/illness, height and rate of temperature rise
- Seizure semiology - generalised vs focal, duration, number of episodes, recovery time
- Immunisation status (timing relative to recent vaccination is occasionally relevant but not typically causative)
- Development and neurological history at baseline
Focused examination
- Careful search for a source of fever and for meningism (neck stiffness, Kernig/Brudzinski - less reliable in infants; assess fontanelle, irritability, feeding)
- Full neurological exam - must be normal between episodes in simple febrile seizure
- Growth and developmental assessment
- Skin for rash (meningococcal, viral exanthem)
Investigation strategy
Simple febrile seizure with clear source, well child post-ictally
- No routine EEG, neuroimaging, or blood tests required - investigate the fever source as clinically indicated, not the seizure itself
Complex febrile seizure or any red flag
- Lumbar puncture if meningitis/encephalitis cannot be clinically excluded, especially age <12 months, incomplete recovery, or clinical signs of meningism
- Bloods (glucose, electrolytes) if prolonged seizure, dehydration, or diagnostic uncertainty
- EEG and neuroimaging reserved for atypical presentations, focal deficits, or recurrent complex seizures - not for a straightforward simple febrile seizure
Management
A. Acute
- Benzodiazepine if seizure ongoing >5 minutes (as for any status pathway)
- Antipyretics for comfort - do not reduce recurrence risk, given for symptomatic relief only
- Treat the underlying febrile illness
B. Simple febrile seizure
- Reassurance is the primary management - benign, self-limited, does not cause brain damage
- No long-term anticonvulsant or continuous antipyretic prophylaxis indicated - neither reduces recurrence meaningfully and both carry unnecessary side-effect burden
- Parent education - what to do during a seizure, when to call an ambulance (>5 min, difficulty breathing, not returning to baseline)
C. Complex febrile seizure
- Lower threshold for admission/observation and LP as above
- Consider rescue benzodiazepine (buccal midazolam/rectal diazepam) supply for families if recurrent prolonged seizures
D. Counselling on recurrence and epilepsy risk
- ~30-40% recurrence risk of further febrile seizures, higher with younger age at first seizure and family history
- Epilepsy risk after simple febrile seizure ~1-2% (close to background population risk); higher (~5-10%) after complex febrile seizure, especially with focal features or family history
Traps
- Ordering EEG or neuroimaging for a straightforward simple febrile seizure - not indicated and does not change management
- Missing meningitis in an infant because fever and drowsiness are attributed to "just the seizure"
- Starting long-term anticonvulsants after a simple febrile seizure - not indicated regardless of parental anxiety
- Using antipyretics with the expectation of preventing further febrile seizures
- Failing to give clear safety-netting advice and rescue benzodiazepine plans for complex/recurrent cases
Talk track
Simple febrile seizure (generalised, brief, single, full recovery) needs no investigation beyond finding the fever source and no long-term treatment beyond reassurance - epilepsy risk is barely above background. Complex features (focal, prolonged, recurrent within 24h, incomplete recovery) lower the threshold for LP and closer follow-up, since meningitis/encephalitis is the differential that must not be missed, and epilepsy risk is meaningfully higher.
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