Paeds

Febrile Convulsions

5 min

Library·Paediatrics·Febrile convulsion

Don't miss

  • Meningitis / encephalitis - LP if <12 months, complex features, or incomplete recovery
  • Complex features: focal, >15 min, >1 in 24 hours, incomplete recovery within an hour
  • Status epilepticus - active seizure >5 min - buccal/intranasal midazolam, ambulance
  • First afebrile seizure (not febrile) - different workup

First-line

Simple FC
Generalised, <15 min, single in 24 h, full recovery <1 h - no investigation if clear fever source
Acute
Position on side, time the seizure; buccal/IN midazolam 0.3-0.5 mg/kg if >5 min
Antipyretics
For comfort only - do NOT prevent recurrence
Post-ictal
Drowsy but rousable, gradual recovery is normal

Refer when

  • Any complex feature
  • Age <12 months with febrile seizure
  • Recurrent febrile seizures or family history of epilepsy
  • Seizure >5 minutes despite first dose midazolam - 111

Tell whanau

  • Simple febrile seizures do NOT cause brain damage or epilepsy
  • Around 1 in 3 affected tamariki have another febrile seizure - usually with a different illness
  • Most outgrow it by 5-6 years old
  • Lay on the side, time it, do not put anything in the mouth; ring 111 if >5 minutes

Febrile convulsions are the most common seizure disorder of childhood, affecting approximately 2-5% of children aged 6 months to 5 years.1 The vast majority are simple febrile convulsions - brief, generalised, and without sequelae. Parental anxiety is considerable; calm, evidence-based reassurance is a core part of the consultation.

❍ Classification, investigation, and acute management

A febrile convulsion occurs in a child with fever (typically above 38°C) in the absence of intracranial infection or other identifiable cause. The distinction between simple and complex guides further management.

A simple febrile convulsion is generalised (tonic-clonic), lasts less than 15 minutes, occurs only once in a 24-hour period, and is followed by complete recovery within an hour. Simple febrile convulsions account for approximately 70-75% of all febrile convulsions. A child with a typical simple febrile convulsion who has fully recovered and has a clear fever source (e.g. otitis media, URTI) does not require routine investigation.

A complex febrile convulsion has one or more of: focal onset or focal features during the seizure; duration 15 minutes or more (febrile status epilepticus); more than one seizure within 24 hours; incomplete recovery to baseline within 1 hour. Complex features mandate further investigation.

Lumbar puncture is indicated in children under 12 months with a febrile convulsion (meningitis may not present with classic signs in infancy), in any child with clinical features of meningitis or encephalitis (neck stiffness, photophobia, altered consciousness, bulging fontanelle, petechial rash), and in any child with a complex febrile convulsion who does not return to normal baseline promptly.3 EEG and neuroimaging are not indicated after a simple febrile convulsion - these decisions are made in secondary care after complex events.

In the acute setting: position safely on the side, time the seizure, and do not cause harm by over-intervention. Buccal midazolam (0.3-0.5 mg/kg, max 10 mg) or intranasal midazolam is the agent of choice for a convulsion not terminated after 5 minutes; rectal diazepam is an alternative if midazolam is unavailable. Most simple febrile convulsions have terminated by the time the child is seen.

Refer to secondary care same day (via emergency department) for: complex febrile convulsion; infant under 12 months with first febrile convulsion; child not returned to normal baseline within 1 hour; clinical features of meningitis or encephalitis; febrile status epilepticus.

❍ Prognosis, recurrence, and parental education

Risk factors for recurrence include: first febrile convulsion before 18 months; family history of febrile convulsions; relatively low temperature at the time of seizure; short duration of fever before the seizure. Approximately 30% of children will have at least one recurrence; risk is highest in the 12 months after the first episode.2

Simple febrile convulsions do not cause brain damage, intellectual disability, or epilepsy. The risk of subsequent epilepsy after a simple febrile convulsion is approximately 1-2%, only marginally above the background population risk of 0.5-1%.1 The risk after complex febrile convulsions is higher (approximately 4-6% after prolonged or focal seizures) and depends on specific features. Most children outgrow febrile convulsions by age 5-6.

This prognostic information is the central deliverable of the consultation. Families are frequently terrified and benefit from clear, unequivocal reassurance backed by evidence. A child with a typical simple febrile convulsion who has fully recovered, is over 12 months, and has a clear fever source can be managed in primary care. Provide written information about febrile convulsions; explain what to do if a seizure recurs (position on side, time the seizure, call 111 if it lasts more than 5 minutes); and arrange follow-up. Families with a known history and recurrence risk may be provided with buccal midazolam for home use in conjunction with a supervising paediatrician.

References

  1. Subcommittee on Febrile Seizures. Febrile seizures: guideline for the neurodiagnostic evaluation of the child with a simple febrile seizure. Pediatrics. 2011;127(2):389-394.
  2. Berg AT, Shinnar S. Predictors of recurrence in children with febrile seizures. J Pediatr. 1990;116(3):329-337.
  3. National Institute for Health and Care Excellence (NICE). Epilepsies in children, young people and adults. NICE guideline NG217. London: NICE; 2022.
  4. Strengell T, Uhari M, Tarkka R, et al. Antipyretic agents for preventing recurrences of febrile seizures: randomized controlled trial. Arch Pediatr Adolesc Med. 2009;163(9):799-804.