Febrile Convulsion
Summary
Febrile convulsions are seizures occurring in children aged 6 months to 5 years, associated with fever, in the absence of intracranial infection or other defined cause of seizure. They are the most common type of childhood seizure, affecting 2-5% of children. Most are "simple" febrile convulsions — generalised tonic-clonic seizures lasting less than 15 minutes without focal features or recurrence within 24 hours. "Complex" febrile convulsions are prolonged, focal, or occur multiple times within 24 hours and require more detailed evaluation. Despite being terrifying for parents to witness, simple febrile convulsions are benign with no long-term neurological sequelae. Antipyretics do NOT prevent recurrence. The main clinical priority is to exclude serious underlying infection, particularly meningitis.
Key Facts
- Definition: Seizure + fever in child 6 months – 5 years without CNS infection
- Prevalence: 2-5% of children (most common seizure type in childhood)
- Peak age: 12-18 months
- Most common cause of fever: Viral upper respiratory tract infection (URTI)
- Notable trigger: HHV-6 (Roseola/Exanthem subitum) — strongly associated
- Simple vs Complex: Simple = generalised, less than 15 min, single in 24h; Complex = any other
- Risk of epilepsy: Slightly increased (1-2% vs 0.5% general population); higher if complex or family history
Clinical Pearls
"The Fever, Not the Height": Febrile seizures occur due to the rapid RISE in temperature, not the absolute height. A child can seize at 38.5°C if the temperature rises quickly.
Antipyretics Don't Prevent Recurrence: Multiple RCTs have shown that regular antipyretics do NOT reduce the risk of further febrile convulsions. Treat fever for comfort, not prevention.
Roseola Alert: HHV-6 (roseola) is the single strongest viral trigger for febrile seizures. The classic roseola pattern is fever for 3 days, then rash appears as fever breaks — often the seizure occurs just before or as the rash appears.
Why This Matters Clinically
Febrile convulsions cause extreme parental anxiety — many parents believe their child is dying during the episode. Reassurance and education are crucial. While most febrile convulsions are benign, the key clinical challenge is excluding meningitis or other serious bacterial infection, particularly in young or unimmunised children. Complex febrile seizures warrant more detailed investigation and follow-up.
Incidence & Prevalence
- Prevalence: 2-5% of children experience at least one febrile convulsion
- Peak incidence: 12-18 months
- Age range: 6 months – 5 years (by definition)
- Recurrence risk: 30% overall; 50% if first seizure less than 12 months; 25% if greater than 12 months
Demographics
| Factor | Details |
|---|---|
| Age | 6 months – 5 years (peak 12-18 months) |
| Sex | Slight male predominance |
| Family history | Strong genetic component; 10-20% have affected first-degree relative |
| Ethnicity | Higher prevalence in Asian populations (up to 8%) |
Risk Factors
Non-Modifiable:
- Age 6 months – 5 years
- Family history of febrile convulsions (strong predictor)
- Family history of epilepsy
- Developmental delay
Modifiable (Risk of Recurrence):
| Risk Factor | Recurrence Risk |
|---|---|
| Age less than 12 months at first seizure | 50% |
| Low peak temperature at first seizure | Higher recurrence |
| Short duration of fever before seizure | Higher recurrence |
| Complex febrile convulsion | Higher epilepsy risk |
Mechanism
Step 1: Fever Onset
- Infection (usually viral) causes release of pyrogens (IL-1, IL-6, TNF-α)
- Hypothalamic set point elevated, leading to fever
- Common triggers: URTI, otitis media, HHV-6 (roseola), HHV-7
Step 2: Immature Thermoregulation
- Developing brain has increased susceptibility to temperature changes
- Rapid rise in temperature (rate of change) is key, not absolute temperature
- Immature GABA inhibitory circuits and increased neuronal excitability
Step 3: Neuronal Hyperexcitability
- Fever increases metabolic demands and neuronal excitability
- Inflammatory cytokines may have direct CNS effects
- Enhanced glutamatergic (excitatory) transmission
Step 4: Seizure Generation
- Synchronised abnormal neuronal discharge
- Generalised tonic-clonic activity (simple FC)
- Focal onset suggests underlying structural/developmental abnormality (complex FC)
Classification
| Type | Criteria |
|---|---|
| Simple Febrile Convulsion | Generalised tonic-clonic; duration less than 15 min; single episode in 24h; full recovery within 1 hour |
| Complex Febrile Convulsion | Focal features OR duration greater than 15 min OR multiple in 24h OR incomplete recovery |
| Febrile Status Epilepticus | Febrile seizure lasting ≥30 minutes (medical emergency) |
Genetic Considerations
- Strong familial tendency (polygenic inheritance)
- SCN1A mutations: Associated with severe forms (Dravet syndrome — presents as prolonged febrile seizures)
- GABRG2 mutations: Associated with generalised epilepsy with febrile seizures plus (GEFS+)
Symptoms
Typical Presentation:
Associated Symptoms (from underlying infection):
Atypical Presentations:
Signs
During Seizure:
Post-Ictal:
Signs of Underlying Infection:
Red Flags
[!CAUTION] Red Flags — Exclude serious bacterial infection/meningitis if:
- Age less than 6 months or greater than 5 years (not typical FC age range)
- Bulging fontanelle (in infants)
- Neck stiffness
- Non-blanching petechial or purpuric rash
- Prolonged post-ictal drowsiness (greater than 1 hour)
- Focal seizure or focal neurological signs
- Complex seizure features
- Incomplete immunisation (consider meningitis/encephalitis)
Structured Approach
General:
- ABCDE if actively seizing or immediate post-ictal
- Temperature (confirm fever)
- Level of consciousness (should improve rapidly)
- Hydration status
Neurological Examination (Post-Ictal):
- Pupils: Should be equal and reactive
- Tone: Normal (hypotonia may persist briefly post-ictal)
- Fontanelle (if open): Should be soft and flat (bulging = raised ICP concern)
- Neck stiffness: Assess carefully (may be difficult in young/crying child)
- Focal signs: Should be absent in simple FC
Full Infection Screen:
- Ears: Otoscopy for otitis media
- Throat: Pharyngitis, tonsillitis
- Chest: Respiratory signs
- Skin: Rash (blanching vs non-blanching)
- Abdomen: UTI sources (especially in young infants)
Special Tests
| Test | Technique | Positive Finding | Clinical Significance |
|---|---|---|---|
| Fontanelle palpation | Gentle palpation | Bulging, tense | Raised ICP — meningitis concern |
| Kernig's sign | Flex hip to 90°, extend knee | Pain on knee extension | Meningeal irritation |
| Brudzinski's sign | Flex neck | Involuntary hip flexion | Meningeal irritation |
| Glass test | Roll glass over rash | Does not blanch | Meningococcal septicaemia |
First-Line (Bedside)
- Temperature — Confirm fever
- Glucose (point-of-care) — Exclude hypoglycaemia
- Observations — HR, RR, SpO2, BP, cap refill
Laboratory Tests
| Test | Indication | Expected Finding |
|---|---|---|
| FBC | Complex FC, unwell child | May show leukocytosis if bacterial infection |
| CRP | Complex FC, unwell child | Elevated in bacterial infection |
| Blood glucose | All (POC or lab) | Normal (exclude hypoglycaemia) |
| U&Es | Prolonged seizure, dehydration | Electrolyte disturbance (rare) |
| Blood culture | Suspected bacteraemia | Positive in sepsis |
| Urine MC&S | Young child (less than 3 years), no clear focus | UTI may be occult fever source |
Lumbar Puncture
Indications:
- Age less than 12 months with first febrile seizure (lower threshold — signs of meningitis subtle)
- Clinical signs of meningitis
- Complex febrile seizure with incomplete recovery
- Incomplete immunisation (Hib, pneumococcal)
- Pre-treated with antibiotics
NOT routinely indicated:
- Simple febrile convulsion in well, fully immunised child greater than 12 months with clear fever source
Imaging
| Modality | Indication |
|---|---|
| CT head | NOT routine; consider if focal seizure, focal neurology, prolonged altered consciousness |
| MRI brain | Outpatient follow-up if complex FC or recurrent |
EEG
- NOT indicated in simple febrile convulsion
- Consider in complex FC or recurrent seizures — usually as outpatient follow-up
Management Algorithm
Acute Seizure Management (ABCDE)
If Actively Seizing:
- Airway: Position child safely; recovery position; do NOT put anything in mouth
- Breathing: High-flow oxygen if available; suction if secretions
- Circulation: Check pulse; prepare IV access if prolonged
- Time the seizure: Critical for guiding intervention
- Disability: Monitor consciousness; check glucose
If Seizure Greater than 5 Minutes:
| Drug | Dose | Route |
|---|---|---|
| Midazolam | 0.5 mg/kg (max 10mg) | Buccal |
| Diazepam | 0.5 mg/kg (max 10mg) | Rectal |
If still seizing after 10 minutes (total seizure time): Repeat dose and/or IV lorazepam 0.1 mg/kg
Post-Ictal Management
Simple Febrile Convulsion:
- Find fever source: Full examination (ENT, chest, urine)
- Antipyretics for comfort: Paracetamol or ibuprofen (does NOT prevent recurrence)
- Reassure parents: Extensive education and written information
- Discharge if well: Clear fever source, child recovered, safety-netting given
Complex Febrile Convulsion:
- Lower threshold for investigations: Consider LP, bloods
- Consider admission: Especially if prolonged or focal
- Outpatient follow-up: Paediatric neurology referral
Parent Education (Critical)
Key Messages:
- Febrile convulsions are common (2-5% of children) and benign
- Child is NOT at risk of brain damage or death from simple FC
- Recurrence is possible (30%) but does NOT mean epilepsy
- Antipyretics treat discomfort but do NOT prevent seizures
- What to do if it happens again: Stay calm, recovery position, time it, call ambulance if greater than 5 min
Disposition
- Discharge: Simple FC, child well, clear fever source, parents educated
- Admit: Complex FC, diagnostic uncertainty, first FC in child less than 12 months, parental concern, dehydration
- Follow-up: GP review in 24-48h; paediatrics if complex or recurrent
Immediate (Minutes-Hours)
| Complication | Incidence | Presentation | Management |
|---|---|---|---|
| Febrile status epilepticus | 5% of FC presentations | Seizure ≥30 min | Emergency seizure protocol; IV benzodiazepines |
| Aspiration | Rare | Cough, desaturation | Suction, positioning, O₂ |
Early (Days)
- Recurrent febrile convulsion: 30% recurrence during same febrile illness or subsequent
- Parental anxiety: Very common; requires extensive reassurance
- Todd's paresis: Transient focal weakness post-seizure (rare; consider complex FC)
Late (Years)
- Recurrence with future fevers: 30% overall
- Development of epilepsy: Risk is small but increased:
- Simple FC: 1-2% (vs 0.5% general population)
- Complex FC: 4-6%
- Family history of epilepsy: Further increases risk
Natural History
- Febrile convulsions occur only within the 6 month – 5 year age window
- Children "grow out of" febrile convulsions as the brain matures
- Simple febrile convulsions have NO long-term neurological sequelae
Outcomes
| Variable | Outcome |
|---|---|
| Recurrence after 1st FC | 30% overall |
| Recurrence if first FC less than 12 months | 50% |
| Risk of epilepsy (simple FC) | 1-2% |
| Risk of epilepsy (complex FC) | 4-6% |
| Cognitive/developmental outcome | Normal |
| Mortality | Near zero for uncomplicated FC |
Prognostic Factors
Good Prognosis (Majority):
- Simple febrile convulsion
- Age greater than 12 months at first episode
- No family history of epilepsy
- Normal neurodevelopment
Increased Epilepsy Risk:
- Complex febrile convulsion
- Family history of epilepsy
- Pre-existing developmental delay
- Multiple recurrences
- Prolonged seizures (particularly febrile status)
Key Guidelines
- NICE CG160 (2021) — Feverish illness in children: assessment and initial management. NICE CG160
- NICE Clinical Knowledge Summaries — Febrile seizure. NICE CKS
- AAP (American Academy of Pediatrics) Guidelines — Febrile seizures clinical practice guideline. AAP
- APLS (Advanced Paediatric Life Support) — Seizure management algorithms. APLS
Landmark Trials
Rosman et al. (1993) — Phenobarbital vs placebo for FC prevention
- 217 children randomised
- Key finding: Phenobarbital reduced recurrence but caused significant behavioural side effects
- Clinical Impact: Established that routine anticonvulsant prophylaxis is NOT indicated
Steering Committee on Quality Improvement (AAP 2008) — LP in febrile seizures
- Systematic review
- Key finding: LP not routinely required in well-appearing child greater than 12 months with simple FC
- Clinical Impact: Reduced unnecessary lumbar punctures
Berg et al. (1997) — Risk of epilepsy after febrile seizures
- Large cohort study
- Key finding: Overall epilepsy risk 2-10% depending on features; higher with complex FC
- Clinical Impact: Informed counselling about long-term prognosis
Evidence Strength
| Intervention | Level | Key Evidence |
|---|---|---|
| Benzodiazepines for acute seizure | 1a | Multiple RCTs |
| LP NOT routine in simple FC greater than 12mo | 1a | AAP systematic review |
| Antipyretics do NOT prevent recurrence | 1a | Cochrane review |
| No routine anticonvulsant prophylaxis | 1a | RCTs |
What is a Febrile Convulsion?
A febrile convulsion (or febrile seizure) is a fit or seizure that happens when your child has a fever. It usually happens in children between 6 months and 5 years old. During the seizure, your child may become stiff, jerk their arms and legs, and become unresponsive — this typically lasts 1-5 minutes.
Is it serious?
Although febrile convulsions are terrifying to witness, they are usually harmless and do not cause any lasting damage to your child's brain. Most children who have one febrile seizure grow out of them and never have epilepsy . About 1 in 3 children who have one febrile convulsion will have another with a future fever, but this is still not harmful.
What causes it?
Febrile convulsions are caused by the brain's reaction to a sudden rise in body temperature. Common triggers are viral infections like colds, ear infections, or roseola (a viral illness with high fever then rash). The fever itself is not dangerous — it's the rapid change in temperature that triggers the seizure.
What should I do if it happens?
- Stay calm — The seizure will usually stop on its own
- Lay your child on their side (recovery position) — This keeps the airway clear
- Do NOT put anything in their mouth — They will not swallow their tongue
- Time the seizure — Note how long it lasts
- Call an ambulance (999/112) if the seizure lasts more than 5 minutes, or if it's their first seizure
What to expect
- After the seizure stops, your child will be sleepy for 30-60 minutes — this is normal
- Once fully recovered, they should be back to their normal self
- The fever will still be there and needs treating for comfort (paracetamol or ibuprofen)
- Giving these medicines regularly does NOT prevent future seizures
When to seek help
Go to the hospital if:
- This is your child's first seizure
- The seizure lasted longer than 5 minutes
- Your child does not wake up within an hour
- Your child has a rash that does not fade when pressed with a glass
- Your child seems very unwell or has a stiff neck
- Another seizure happens within 24 hours
Primary Guidelines
- National Institute for Health and Care Excellence. Feverish illness in children (CG160). 2021. NICE CG160
- American Academy of Pediatrics Subcommittee on Febrile Seizures. Clinical Practice Guideline—Febrile Seizures: Guideline for the Neurodiagnostic Evaluation of the Child With a Simple Febrile Seizure. Pediatrics. 2011;127(2):389-394. PMID: 21285335
Key Literature
- Steering Committee on Quality Improvement and Management, Subcommittee on Febrile Seizures. Febrile seizures: clinical practice guideline for the long-term management of the child with simple febrile seizures. Pediatrics. 2008;121(6):1281-1286. PMID: 18519501
- Offringa M, et al. Prophylactic drug management for febrile seizures in children. Cochrane Database Syst Rev. 2017;(2):CD003031. PMID: 28211911
- Berg AT, et al. Predictors of recurrent febrile seizures. A prospective cohort study. Arch Pediatr Adolesc Med. 1997;151(4):371-378. PMID: 9111436
Further Resources
- NHS Febrile Seizures: nhs.uk/conditions/febrile-seizures
- Epilepsy Action: epilepsy.org.uk
- Great Ormond Street Hospital Information: gosh.nhs.uk
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Any child with a seizure should be assessed by a healthcare professional to exclude serious underlying causes.