Paediatrics chapters
Febrile seizures
Fits with fever in young children who have no brain infection: who gets them, simple versus complex types, when to do a lumbar puncture, how to treat the fit, and the real risks of recurrence and epilepsy.
- A febrile seizure is a fit with fever in a child aged about 6 months to 5 years (peak second year) without CNS infection or metabolic cause; it affects about 3-4% of children and runs in families.
- Simple: generalised, under 15 minutes, once in 24 hours, in a normal child; complex: focal, prolonged or repeated within 24 hours, or an abnormal child; meningitis must be excluded, with a low threshold for lumbar puncture in infants.
- Stop a long fit with diazepam (rectal or IV), treat the fever and its cause; daily anticonvulsants are not advised; recurrence occurs in about a third, and later epilepsy is only about 2-4%.
On this page
Overview
Febrile seizures (febrile convulsions) are fits that occur with fever in an otherwise normal young child without an infection of the brain or an acute metabolic cause. They are the commonest seizure disorder of childhood. Most are short and harmless, and the main jobs of the doctor are to exclude meningitis, stop a prolonged fit, and reassure the parents.
Definition and criteria
A febrile seizure requires all of the following:
- Age roughly 6 months to 5 years (Akbar gives 3 months to 5 years; most occur between 6 and 18 months, peak in the second year).
- Fever (Akbar quotes about 38.8°C or more).
- No CNS infection or inflammation.
- No acute metabolic cause (for example low sodium, glucose or calcium).
- No previous afebrile seizures.
A fit with fever in a child who has already had afebrile seizures is not a febrile seizure; it is epilepsy triggered by fever.
Epidemiology and cause
- Affect about 3-4% of children (Nelson about 4%); boys about twice as often as girls.
- Genetic tendency: a strong family history is common; many first-degree relatives have had them, and inheritance may look autosomal dominant.
- Triggers are mostly viral illnesses: upper respiratory infection, otitis media, pharyngitis, and also urinary infection. The exact mechanism is unknown; a rapid rise in temperature has been suggested.
- The fit usually happens early in the illness, often on the first day.
Types
| Feature | Simple (typical) | Complex (atypical) |
|---|---|---|
| Type of fit | Generalised tonic-clonic or clonic | Focal features |
| Duration | Under 15 minutes (most under 5) | Over 15 minutes |
| Number | Once in 24 hours | Repeated within 24 hours |
| Child | Neurologically and developmentally normal | May have a known neurological problem |
| Outlook | Excellent | Higher risk of later epilepsy |
- More than 90% of febrile seizures are generalised, last under 5 minutes and occur early in the illness.
- 60-70% of children have just one seizure.
- A prolonged febrile fit may later cause mesial temporal sclerosis and temporal lobe epilepsy.
Simple = Generalised, Short (under 15 minutes), Single in 24 hours, normal child. Any break in this pattern makes it complex.
Evaluation
History and examination
Look for the source of fever (ear, throat, chest, urine), signs of meningitis, and the child's development. Ask about family history of febrile seizures and epilepsy.
Lumbar puncture
Meningitis must be ruled out, even in a child with previous febrile fits, because in young infants meningeal signs are unreliable. Akbar suggests CSF examination when:
- The child is under about 18 months (the younger the child, the stronger the case).
- Recovery is slow or consciousness stays impaired.
- No other cause of the fever is found.
- Close follow-up is not possible.
- Nelson adds: any clinical signs of meningitis or intracranial infection.
Other tests
- Simple febrile seizure with full recovery: little or no testing beyond what is needed to find the cause of the fever (Nelson).
- Blood count, glucose, calcium, electrolytes and urea if the picture is atypical or the child is unwell.
- EEG is not needed in simple febrile seizures; if done for complex seizures, wait at least a week so fever and the fit itself do not distort it.
- Neuroimaging only for focal signs or suspicion of a structural cause.
An EEG or CT scan is not part of routine assessment of a simple febrile seizure.
Management
During the fit
- Place the child on the side, clear the airway, give oxygen, and do not put anything in the mouth.
- If the fit has not stopped, give diazepam: rectally (useful at home or without IV access) or IV 0.2 mg/kg slowly. Rectal paraldehyde or IV phenobarbitone are alternatives (Akbar).
- A fit lasting 30 minutes or more is febrile status epilepticus and is managed as status.
After the fit
- Treat the fever: paracetamol and tepid sponging, for comfort.
- Treat the cause: antibiotics only if a bacterial infection is suspected or found.
- Reassure the parents: explain that simple febrile seizures do not cause brain damage or lower intelligence. Teach first aid and when to use rectal diazepam.
Prophylaxis
| Option | Key points |
|---|---|
| None (usual) | Not indicated for simple febrile seizures |
| Intermittent diazepam | Given at the start of a febrile illness and continued during it; an option for frequent or prolonged fits or very anxious parents |
| Continuous phenobarbitone (Akbar) | For selected complex cases; cuts recurrence by about two-thirds but causes behaviour and learning problems |
| Sodium valproate | Also effective, but has serious side effects in young children |
| Phenytoin, carbamazepine | Not effective for preventing febrile seizures |
- Nelson: daily anticonvulsants are not recommended because the side effects outweigh the benefit; rectal diazepam to abort a prolonged event is reasonable.
- Antipyretics do not prevent febrile seizures.
"Reassure, Rectal diazepam, no Routine drugs."
Phenytoin and carbamazepine do not prevent febrile seizures.
Prognosis
Recurrence
- Febrile seizures recur in about 30-50% of children (Nelson); Akbar quotes 20-40%.
- Most recurrences occur within 1 year, and nearly all within 2-3 years.
| Risk factors for recurrence (Akbar) |
|---|
| Age under 1 year at first seizure (the strongest) |
| Short duration of fever (under 24 hours) before the fit |
| Seizure at a relatively low temperature (38-39°C) |
| Family history of febrile seizures or epilepsy |
| Complex first seizure |
With no risk factors the recurrence risk is about 12%; it rises steeply as factors add up.
Later epilepsy
- After simple febrile seizures, the risk of epilepsy is about 2%, hardly above the general population (Nelson); Akbar gives 2-4% overall.
- The risk rises with complex febrile seizures, abnormal development or neurological examination before the fit, onset under 1 year, and a family history of epilepsy.
- Intelligence is normal after simple febrile seizures.
A recurrence of febrile seizures is common; epilepsy is uncommon. Do not confuse the two figures.
Expect: age range and peak; definition requiring no CNS infection; simple versus complex features (15 minutes, focal, repeated in 24 hours); lumbar puncture in young infants and when meningitis cannot be excluded; EEG not routine; rectal or IV diazepam for a prolonged fit; no daily prophylaxis for simple seizures; antipyretics do not prevent fits; recurrence about a third and epilepsy about 2%; risk factors for recurrence and for epilepsy; a typical scenario of a toddler with a brief generalised fit on the first day of a cold.
Quick revision
- Fit with fever, no CNS infection, age about 6 months to 5 years, peak second year.
- 3-4% of children; boys; strong family tendency; viral triggers.
- Simple: generalised, under 15 minutes, once in 24 hours, normal child.
- Complex: focal, prolonged or repeated.
- Exclude meningitis; LP especially in infants and when unsure.
- Diazepam for a prolonged fit; paracetamol for comfort; treat the source.
- No daily prophylaxis for simple seizures; phenytoin and carbamazepine do not work.
- Recurrence about 30-50%; epilepsy about 2% (higher with complex fits).
Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics).
FAQ
Does a febrile seizure damage the brain?
A simple febrile seizure does not cause brain damage or reduce intelligence. Very prolonged fits are different and can rarely lead to temporal lobe scarring.
Should every child with a febrile seizure have a lumbar puncture?
No, but meningitis must be excluded. A lumbar puncture is advised in young infants, when recovery is slow, when no source of fever is found, or when there are signs of meningitis.
Will paracetamol prevent another febrile seizure?
No. Antipyretics make the child more comfortable but do not prevent febrile seizures.
What are the chances of another febrile seizure or of epilepsy?
About a third of children have another febrile seizure, mostly within a year. Only around 2% of children with simple febrile seizures develop epilepsy.