Febrile seizures in children
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Febrile Seizures in Children
Definition & Epidemiology
Febrile seizures (FS) are seizures associated with fever (≥38°C / 100.4°F) without evidence of CNS infection, toxic encephalopathy, or a history of prior afebrile seizures. They represent the most common convulsive disorder of young children, affecting 2-5% of U.S. children.
- Age range: typically 6 months to 5-6 years; peak onset in the second year of life
- Boys are affected slightly more often than girls
- The at-risk period is thought to be rapid temperature rise or defervescence, though absolute fever severity is also important (contrary to the popular belief that rate of rise is the dominant factor - data do not clearly support rate over severity)
- Tintinalli's Emergency Medicine, p. 936; Textbook of Family Medicine 9e, p. 2615; Rosen's Emergency Medicine, p. 3158
Classification
Simple Febrile Seizure
- Generalized (non-focal), typically tonic-clonic
- Duration < 15 minutes
- Occurs only once within a 24-hour period
- Child is neurologically normal
- Age 6 months to 5-6 years
Complex Febrile Seizure
Any one or more of the following:
- Focal features (unilateral, asymmetric, partial onset)
- Duration > 15 minutes
- Recurs within 24 hours (more than one seizure in the same febrile illness)
- Occurs outside the typical age range (< 6 months or > 6 years)
- Persistent altered mental status > 1 hour after the seizure
Note: Febrile status epilepticus is a prolonged febrile seizure lasting > 30 minutes and carries a higher risk of associated bacterial meningitis (15-18%) compared to simple FS (0.4-1.2%).
- Rosen's Emergency Medicine, p. 3158; Tintinalli's EM, p. 935-936; Royal Children's Hospital Melbourne Guidelines
Risk Factors for a First Febrile Seizure
- Family history of febrile seizures
- Developmental delay
- Very high fever
- Child care attendance (increased infectious exposure)
- Textbook of Family Medicine 9e, p. 2616
Risk Factors for Recurrence
About 1/3 of children who have a first FS will have at least one more. Specific data:
- Children < 12 months at first FS: ~50% recurrence risk
- Children > 12 months at first FS: ~30% recurrence risk
- Most recurrences occur within 1 year
Additional factors increasing recurrence risk:
- Family history of febrile seizures
- Younger age at first FS
- Developmental delay
- Focal seizures, Todd's paralysis
- Abnormal findings on EEG, CT, or MRI
- Tintinalli's EM, p. 936; Textbook of Family Medicine 9e, p. 2617
Risk of Epilepsy
- General population risk: 0.5-1%
- After a simple FS: risk is approximately 1-2% (only slightly above baseline; some sources say essentially the same ~1% by age 7)
- After complex/multiple FS with risk factors: risk rises to up to 7-10%
Risk factors that increase epilepsy risk:
- Pre-existing neurological disorder or developmental delay
- Family history of epilepsy (not just febrile seizures)
- Complex febrile seizure (focal, prolonged > 15 min, or recurrent within 24 hours)
If all three risk factors are present, the risk of epilepsy reaches approximately 10%.
- Rosen's EM, p. 3158; Goodman & Gilman's Pharmacological Basis of Therapeutics, p. 1266; Tintinalli's EM, p. 936
Evaluation
What is NOT routinely needed
- Routine blood work
- Neuroimaging (CT or MRI)
- Electroencephalogram (EEG) - the AAP specifically states EEG should not be performed in a neurologically healthy child after a simple FS, as abnormalities do not predict recurrence or onset of epilepsy
- Hospitalization
The evaluation should focus on identifying the source of fever (e.g., urinalysis and urine culture, throat swab, etc.).
Lumbar Puncture (LP)
LP is not routinely indicated but should be:
| Situation | LP Recommendation |
|---|---|
| Signs/symptoms of meningitis (meningismus, bulging fontanelle, Kernig/Brudzinski signs) | Strongly indicated |
| Child < 12 months with unimmunized status (H. influenzae b or S. pneumoniae) | Should be considered |
| Child on antibiotics prior to seizure (partially treated meningitis) | Should be considered |
| Age < 6 months with febrile seizure | Should be considered |
| Febrile status epilepticus (seizure > 30 min) | Should be performed |
| Well-appearing, fully immunized child > 18 months | Not indicated |
The key principle: bacterial meningitis is exceedingly rare in the absence of clinical signs of meningitis, and children with meningitis almost always show signs of sepsis or meningeal irritation in the post-ictal period.
- Tintinalli's EM, p. 935-936; Harriet Lane Handbook 23e, p. 739; Family Medicine 9e, p. 2621-2622
Management
Acute Seizure Management
- Protect the airway; place child on their side
- Most febrile seizures self-terminate within 1-3 minutes (typically < 6 min)
- If the seizure continues > 5 minutes or the child is in febrile status epilepticus: administer a benzodiazepine
- Diazepam (rectal) or midazolam (intranasal/buccal/IM) are first-line
- Lorazepam IV if access is available
Antipyretics
- Antipyretics (acetaminophen, ibuprofen) are appropriate to treat fever and discomfort
- However, there is no evidence that antipyretics prevent subsequent febrile seizures - they do not reduce recurrence risk
Anticonvulsant Prophylaxis
The AAP and current guidelines do not recommend continuous or intermittent anticonvulsant therapy for simple FS because:
- Side effects outweigh the minor risks of recurrence
- No demonstrated ability to improve long-term neurologic outcomes
- Phenobarbital prophylaxis causes significant cognitive side effects
For high-risk children (multiple complex FS, strong family history), intermittent rectal diazepam at the time of fever onset has been used to prevent recurrent seizures, avoiding the side effects of chronic therapy.
- Goodman & Gilman's, p. 1267; Harriet Lane Handbook, p. 739; Tintinalli's EM, p. 936; AAP guidelines
Disposition
Children with simple FS who recover to baseline can almost always be sent home, provided:
- Satisfactory clinical improvement; child is alert and at neurological baseline
- Source of fever has been identified and addressed
- Close outpatient follow-up is arranged
Children requiring hospitalization or closer observation include those with:
- Features of complex FS
- Febrile status epilepticus
- Concern for CNS infection
- Not returning to neurological baseline
Parental Education (Key Points)
Parents are often terrified by a febrile seizure. Reassurance should cover:
- High recurrence likelihood (> 33%) but most are benign
- Low epilepsy risk (~1-2%, essentially the same as general population for simple FS)
- No long-term neurological damage from a simple FS - cognitive outcomes are normal
- Seizure first aid: place on side, protect from injury, do not restrain or put anything in mouth, call 911 if seizure lasts > 5 minutes
- Antipyretics help with fever/comfort but will not reliably prevent recurrences
Vaccine-Related Febrile Seizures
Febrile seizures can occur after vaccination:
- DTaP: most likely within 48 hours
- MMR: most likely within 10 days (during the viremic period)
These are managed the same as any other febrile seizure and are not a contraindication to future vaccination.
- Textbook of Family Medicine 9e, p. 2628
Summary Table
| Feature | Simple FS | Complex FS |
|---|---|---|
| Seizure type | Generalized tonic-clonic | Focal or generalized |
| Duration | < 15 min | > 15 min |
| Recurrence in 24h | None | ≥ 1 recurrence |
| Age | 6 mo - 5-6 yr | Outside typical range |
| EEG/Imaging | Not indicated | Not routinely needed |
| LP | Only if meningitis signs | Consider more carefully |
| Antiepileptic prophylaxis | Not recommended | Not routinely recommended |
| Epilepsy risk | ~1-2% | Up to 7-10% (with risk factors) |
| Recurrence risk | ~30-50% | Higher |
Sources:
- Tintinalli's Emergency Medicine, pp. 935-936
- Rosen's Emergency Medicine: Concepts and Clinical Practice, pp. 3158-3159, 3287
- Harriet Lane Handbook (Johns Hopkins, 23rd ed.), p. 739
- Textbook of Family Medicine 9e, pp. 2615-2629
- Goodman & Gilman's Pharmacological Basis of Therapeutics, p. 1266-1267
- 2024 Best Practices for Management of Febrile Seizures - Ferretti et al., Italian Journal of Pediatrics (2024) - confirms AAP guidance: no EEG for simple FS, no routine anticonvulsant prophylaxis
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