Basics
Description
Febrile seizure: seizure in ≤60-month-old child accompanied by a fever ( ≥100.4 � �F or 38 � �C by any method) but without central nervous system infection or prior unprovoked seizure (American Academy of Pediatrics [AAP] guidelines use 6 months as the lower age limit, whereas International League Against Epilepsy uses 1 month) � �
2 types: � �
- Simple: febrile seizures that are generalized, last <15 minutes, AND do not recur in 24 hours
- Complex
- Febrile seizures that are focal (including postictal weakness), last ≥15 minutes, OR occur >1 time in 24 hours
- Febrile status epilepticus: 1 febrile seizure or series of febrile seizures without full recovery in between lasting ≥30 minutes
Epidemiology
- Age
- Most febrile seizures occur between 6 months and 3 years of age.
- Peak age is about 18 months.
- Type
- 65 " �70% are simple febrile seizures.
- 20 " �35% are complex febrile seizures.
- � � �5% are febrile status epilepticus.
- Timing of seizure
- � � �20% before or <1 hour of fever onset
- � � �60% 1 " �24 hours after fever onset
- � � �20% >24 hours after fever onset
Prevalence
- Most common childhood seizure
- Febrile seizures occur in 2 " �5% of children in the United States and Western Europe, 9 " �10% of children in Japan, and 14% of children in Guam.
Risk Factors
Positive family history of febrile seizures � �
Genetics
Usually multifactorial or polygenic inheritance � �
General Prevention
Antipyretics do not reduce the recurrence risk of simple febrile seizures. � �
Pathophysiology
- Elevated temperatures in developing brain may increase neuronal excitability.
- Fever increases cytokines that may enhance neuronal excitability.
- Genetic factors
- Hyperventilation from fever causes a respiratory alkalosis that may promote seizures.
Etiology
- Any viral or bacterial infection
- Human herpesvirus 6 and 7
- Influenza A
- Vaccines
- MMR(V) and DPT
- Both increase the risk of febrile seizures but not epilepsy.
- Benefits greatly outweigh any risk, and families should be encouraged to vaccinate.
- Shigellosis
Commonly Associated Conditions
- Generalized epilepsy with febrile seizures plus (GEFS+)
- Febrile seizures beyond 6 years of age or afebrile seizures of varying types ranging from mild to severe
- Multiple genes identified including SCN1A, SCN2A, SCN1B, GABRG2, GABRD, and PCDH19
- Febrile infection " �related epilepsy syndrome (FIRES)
- Catastrophic epileptic encephalopathy of unknown etiology that begins with a febrile illness and refractory status epilepticus
- Has high morbidity and mortality
Diagnosis
History
- Obtain detailed description of spell to determine if it was a seizure.
- Circumstances in which spell occurred
- Duration
- Focal features suggest seizure
- Postictal weakness suggests seizure
- Ask about prior seizures/spells.
- Prior afebrile seizure suggests epilepsy.
- Prior febrile seizures supports diagnosis.
- Prior nonepileptic spells
- Determine cause of fever/illness
- Duration
- Height of fever
- Symptoms: rhinorrhea, diarrhea
- Ask about new neurologic symptoms such as headache or change in gait that would require further evaluation.
- Ask about toxic ingestions.
- Identify seizure risk factors from past medical history.
- Perinatal complications
- Prior brain insult: trauma, meningitis
- Developmental delay
- Medications including antibiotics
- Identify seizure risk factors from family history.
Physical Exam
- Identify fever source.
- Vital signs, including temperature
- Assess anterior fontanelle, sutures, and head circumference for increased intracranial pressure, which may occur with meningitis or space-occupying lesion.
- Assess for signs of meningitis such as nuchal rigidity.
- Examine ears and throat for infection.
- Examine skin for rashes and other signs of infection.
- Examine heart and lungs for infection.
- Assess for trauma.
- Detailed neurologic exam
- Assess skin for neurocutaneous syndromes.
- Assess mental status.
- Assess for subtle signs of seizure such as myoclonus or nystagmus.
- Examine cranial nerves. Include funduscopic exam for papilledema.
- Examine gait, motor system, sensation, coordination, and deep tendon reflexes for abnormalities and asymmetries.
Diagnostic Tests & Interpretation
Simple Febrile Seizure
Recommendations from the 2011 AAP Guideline for neurologically healthy infants and children � �
Lab
- Serum electrolytes, calcium, phosphorus, magnesium, glucose, and complete blood count are not recommended solely for determining the cause of the seizure.
- Consider studies to determine fever source.
- Lumbar puncture
- Perform when symptoms/signs of meningitis or intracranial infection are present
- Consider lumbar puncture if
- 6 " �12-month-old infant has deficient or unknown immunization status for Haemophilus influenzae type b or Streptococcus pneumoniae
- Pretreated with antibiotics
Imaging
Not indicated � �
Electroencephalogram
- Not indicated
- Not predictive of febrile seizure recurrence or development of epilepsy
Complex Febrile Seizures
There is no AAP Guideline. � �
Lab
- Consider studies to identify fever source and as clinically indicated.
- Indications for lumbar puncture are similar to indications for lumbar puncture for simple febrile seizure but strongly consider for all, especially those with altered mental status.
Imaging
- Acute brain imaging usually unnecessary, especially if the only complex feature is multiple seizures. Recommend acute MRI (CT acceptable) if with persistently altered mental status, persistent focal neurologic findings, or symptoms/signs of increased intracranial pressure.
- Recommend routine brain MRI if not done acutely especially for focal seizure, focal exam findings, or focal EEG abnormality.
Electroencephalogram
- Recommend stat EEG if concerned about nonconvulsive status epilepticus.
- Recommend routine EEG, especially for abnormal neurologic development or exam. Epileptiform abnormalities or focal slowing may increase risk for developing epilepsy.
Febrile Status Epilepticus
No AAP Guideline. See "Status Epilepticus " � chapter. � �
Lab
- Recommend studies to treat correctable causes of seizures (e.g., hypoglycemia, hyponatremia) and to identify fever source.
- Lumbar puncture
- Perform for any suspicion of meningitis or intracranial infection but strongly consider for all especially if first episode or if mental status is altered.
- It is important to note that febrile status epilepticus rarely causes a CSF pleocytosis.
Imaging
- Recommend acute brain imaging (MRI preferred but CT acceptable), especially if first episode with abnormal mental status or focal neurologic findings.
- Recommend routine brain MRI if not done acutely; may show hippocampal injury that may increase risk for developing epilepsy
Electroencephalogram
- Recommend stat EEG if concerned about nonconvulsive status epilepticus.
- Recommend routine EEG; may show temporal slowing or attenuation that correlates with hippocampal abnormality on MRI
Differential Diagnosis
- Acute symptomatic seizure
- Infection
- Meningoencephalitis: primary diagnostic consideration; bacterial or viral; consider HSV.
- Other infection such as gastroenteritis causing hypernatremic dehydration
- Benign convulsions with mild gastroenteritis
- Toxic/metabolic
- Stroke
- Trauma
- Epilepsy
- Nonepileptic spell
- Febrile delirium
- Chills
- Breath-holding spells
Treatment
Medication
- Abortive: consider rectal diazepam (0.5 mg/kg) for febrile seizures ≥5 minutes; may cause drowsiness and ataxia; rarely causes respiratory depression
- Preventive
- In certain clinical circumstances, for parental anxiety, may use oral diazepam (0.33 mg/kg every 8 hours) to the patient during a febrile illness until afebrile for 24 hours; may cause drowsiness and ataxia
- Daily phenobarbital, valproate, or primidone prevents febrile seizures, but risks outweigh benefits.
Additional Treatment
General Measures
- See "Status Epilepticus " � chapter for treating febrile status epilepticus.
- Treat infection
Ongoing Care
Prognosis
- Febrile seizure recurrence
- 50% of children <12 months of age at time of first simple febrile seizure have recurrent febrile seizures.
- 30% of children >12 months of age at time of first febrile seizure have a second.
- Of children with a second febrile seizure, 50% experience a third.
- Risk for developing epilepsy:
- 6 " �7% for all febrile seizures
- 2 " �7.5% for simple febrile seizures
- 10 " �20% for complex febrile seizures
- Mortality
- 0.85% for all febrile seizures
- 0% for simple febrile seizures
- <1.6% for complex febrile seizures with all deaths from febrile status epilepticus
- No evidence that simple febrile seizures increase risk of neurologic or cognitive deficits.
Additional Reading
- Chugath � �M, Shorvon � �S. The mortality and morbidity of febrile seizures. Nat Clin Pract Neurol. 2008;4(11):610 " �621. � �[View Abstract]
- Dube � �CM, Brewster � �AL, Baram � �TZ. Febrile seizures: mechanism and relationship to epilepsy. Brain Dev. 2009;31(5):366 " �371. � �[View Abstract]
- Shinnar � �S, Glauser � �TA. Febrile seizures. J Child Neurol. 2002;17(Suppl 1):S44 " �S52. � �[View Abstract]
- 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. � �[View Abstract]
- 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. � �[View Abstract]
Codes
ICD09
- 780.31 Febrile convulsions (simple), unspecified
- 780.32 Complex febrile convulsions
ICD10
- R56.00 Simple febrile convulsions
- R56.01 Complex febrile convulsions
SNOMED
- 434101000124100 Simple febrile seizure, non-refractory (finding)
- 433681000124102 Complex febrile seizure, non-refractory (finding)
- 434091000124106 Simple febrile seizure, refractory (finding)
- 433671000124100 Complex febrile seizure, refractory (finding)
- 307200007 Recurrent febrile convulsion (finding)
- 41497008 Febrile convulsion (finding)
FAQ
- Q: What should parents be told?
- A: Good neurodevelopmental outcome for simple febrile seizures but relatively high risk for recurrence.
- Q: Can a child die from a febrile seizure?
- A: No reported mortality from simple febrile seizures or short complex febrile seizures. Small mortality with febrile status epilepticus.
- Q: Can a febrile seizure cause brain damage?
- A: Simple febrile seizures do not. Febrile status epilepticus may.
- Q: What should the parents do when the child has a seizure?
- A: Stay calm. Place child in safe place. Turn child on side to keep airway clear. Do not restrain. Do not put anything in mouth. Time seizure. If seizure lasts 5 minutes, call 911 and administer abortive medication such as rectal diazepam if available.
- Q: What precautions should the parents take?
- A: Common sense steps such as no unsupervised baths or swimming and no climbing above head height. Always wear helmet when riding bike or doing other activity with wheels. No driving all-terrain vehicles.