An 8 month old baby has been referred to you by the Accident and Emergency Department with the first episode of febrile convulsion. He has been coryzal over the last couple of days with spikes of temperature up to 38oC. The episode lasted for 5 minutes, the baby felt hot at the time and following recovery he has remained well.
- Febrile seizures are benign in nature
- They typically occur in children 6 months-6 years and they can be either simple or complex (duration > 15 minutes, multiple seizures over a 24 hour period, focal neurology).
- The risk of recurrence is 30%
- The risk of developing epilepsy following a simple febrile seizure is low but significantly higher with complex febrile seizures
- There is no evidence for the use of regular antipyretics to prevent recurrence during an acute febrile episode
- Part of the management is parental education on the management of future episodes at home and recognition of signs that the child needs urgent medical attention
What is a febrile seizure ?
A febrile convulsion is a seizure associated with fever (at least 38oC) in the absence of central nervous system infection or any electrolyte imbalance in a young child. By definition, febrile seizures occur in children between 6 months and 6 years of age. The median age of onset is 18 months and half of the children present between 12 and 30 months.
A simple febrile seizure is the most common type of febrile seizure (75%). It is usually a brief, generalised tonic-clonic seizure occurring with the onset of a rising temperature. In 87% of children, the duration of the febrile seizure is less than 10 minutes.
A complex febrile seizure is defined by at least one of the following criteria:
- Duration of the seizure longer than 15 minutes
- Multiple seizures within the last 24 hours
- Presence of focal seizures
Febrile status epilepticus (> 30 minutes duration) occurs in only 5% of the paediatric population.
The hypothalamus in the human brain is responsible for homeostatic core temperature regulation. The hypothalamus is still developing in a young child and therefore it is more susceptible to straight rises in the body temperature. The febrile seizures represent the meeting point of low threshold for seizures and a trigger which is fever.
Mutations in sodium ion channel genes and neurotransmitter genes (e.g. gamma aminobutyric acid) have been identified in children with febrile seizures. These findings suggest the hypothesis of neuronal hyperexcitability to certain triggers.
Fever is the main trigger for febrile seizures. Viral infections are the main cause of fever. HHV-6 in roseola accounts for 20% of the cases presenting with the first episode of simple febrile seizures.
This is a commonly asked question by the parents. 30% of the children with a first episode of febrile convulsion will have a recurrence in the future. The following are risk factors associated with higher risk of recurrence:
- Onset before the 18 months
- Shorter duration of fever (<1 hour) before the onset of the seizure
- Lower temperature close to 38oC
- Family history of febrile seizures
The vast majority of children presenting with febrile convulsion do not develop epilepsy.
The following are risk factors for developing afebrile seizures:
- Complex febrile seizures
- Presence of neurodevelopmental abnormality
- Family history of epilepsy
- Prolonged febrile seizures
Children with no risk factors have a 2.4% risk of developing afebrile seizures by the age of 25 compared with 1.4% percent for the general paediatric population. The risk is increased to 49% when all three component features of complex febrile convulsions are present.
The investigations done on a child with fever should be directed by the severity of the illness and the suspected underlying condition.
For a child presenting with a simple febrile seizure and who is otherwise well, a careful history and a careful system examination should reveal the cause of infection. A urine sample should always be obtained to rule out urinary tract infection. Routine blood tests in children with simple febrile seizures is not recommended.
The following investigations should be considered in cases with diagnostic uncertainty or when the child appears to be unwell:
- Routine blood testing for FBC, urea and electrolytes and CRP
- CXR to look for evidence of chest infection
- Lumbar puncture: if not contraindicated it should be performed as soon as possible when meningitis or encephalitis is suspected
- Neuroimaging when focal neurology is present
When there is evidence of bacterial infection, antibiotic treatment should be given accordingly. When meningitis/encephalitis is suspected admission to the hospital is required for immediate commencement on intravenous antibiotics (ceftriaxone +/- acyclovir).
What advice should be given to parents?
The following advice should be given to parents :
The benign nature of the seizures
The risk of recurrence (30%)
The little evidence behind using antipyretic agents solely to keep temperature down or to prevent future episodes
Management of future episodes (placing the child in the lateral position, avoid forcing anything into the child’s mouth, ringing an emergency ambulance if seizure lasts for >5 minutes)
Explanation of signs and symptoms that would imply that the child is unwell (dehydration, petechial spots)
Explain the use of prophylactic diazepam and that this is very rarely needed
Febrile Seizures, NICE Clinical Knowledge Summaries 2008