• Ashley Grigsby, DO

It's Getting Hot in Here

A Review of Febrile Seizures


Author: David Rayburn, MD, MPH


WE'RE BACK! Sorry for the short hiatus, but David is coming out strong with a new post about febrile seizures!


What are febrile seizures and who gets them?

Febrile seizures are the most common neurological disorder in infants and young children, occurring in approximately 2-4% of children before age 5. Febrile seizures tend to occur in children between the ages of 6 months and 5 years, with peak incidence between 12-24 months (6).


Criteria for the diagnosis of febrile seizure include (adapted from the AAP Subcommittee on febrile seizures):

1. Convulsions with a temperature >38C

2. A child older than 6 months and less than 5 years of age

3. Absence of central nervous system (CNS) infection or inflammation

4. Absence of acute systemic metabolic abnormality than may produce convulsions and

5. No history of previous afebrile seizure


The majority of febrile seizures involve convulsions with loss of consciousness and generalized tonic-clonic jerking of upper and lower extremities(1). The first day of illness tends to be the timing for febrile seizure and can sometimes be the first sign a child is sick (4).


Once a child has been diagnosed with a simple febrile seizure there is an ~30% chance of recurrence during childhood. The risk of epilepsy, however, is only slightly higher than the general population. In contrast, a diagnosis of complex febrile seizure is associated with a higher risk of recurrence and an increased risk of future afebrile seizures (6). Complex febrile seizures often occur in younger children and are associated with abnormal development as the child gets older.


There are several risk factors for a child to have a febrile seizure and they include:

1. High fever

- This is debated, but likely peak of fever is the risk factor compared to the rate of

rise of the fever. It used to be hypothesized that children who had a rapid rise of

fever were at increased risk.

2. Viral infections

- HHV-6 tends to be associated with high fevers (103 or greater) and children with

a diagnosis of HHV-6 have an increased incidence of febrile seizures

- Influenza has also been associated with increased risk of febrile seizures during

the acute illness

3. Family history of febrile seizures

- Having a first degree relative with a hx of febrile seizures increases a child’s risk

of febrile seizure

4. Recent immunizations

- Per the CDC, there is a small increased risk of febrile seizure after receiving the

MMR and MMRV vaccines. This can occur between 5-12 days after

immunization. DTAP has also been associated with an increased risk of febrile

seizure.


Simple or not?

The typical presentations of simple vs. complex febrile seizures are listed below. The

determination of the type of febrile seizure can usually be determined from History and

Physical alone. This determination will help guide any necessary work up or consultation.


SIMPLE

- Duration less than 15 minutes*

- Single episode in 24 hours

- Generalized tonic clonic activity

- 6 months to 5 years old

- Usually shorter post-ictal state


COMPLEX

- Duration longer than 15 minutes

- More than one seizure episode in 24 hours

- Focal seizure at any point in seizure (take a good history!)

- May have prolonged post ictal state


*Simple febrile seizures by definition last < 15 minutes, but typically are much shorter lasting 3-4minutes (3).


The Workup & Treatment

For the vast majority of children meeting criteria for simple febrile seizure who have a reassuring neurological exam, the workup should be only for the fever as indicated by history and physical exam and not for the seizure itself. The parents do require extra counseling especially regarding the likelihood that this could happen again since that risk is around 30%. It is also prudent to know that the use of antipyretics does not prevent the occurrence of febrile seizures, but their use after a febrile seizure occurs decreases the likelihood of a recurrent febrile seizure in the short term (6).


Children with complex febrile seizures typically require additional work up, but like first time pediatric seizures (discussed further here) head imaging (MRI) and EEG can usually be done in the outpatient setting. There is no standard approach to patients with complex febrile seizures and diagnostic workup is usually developed between the treating clinician in consultation with a pediatric neurologist. Obtaining serum electrolytes is a high yield test in complex febrile seizure patients. There is a higher incidence of hyponatremia in the setting of acute illness and is associated with recurrent seizure during illness. Also making sure the glucose is normal is best practice for any seizure patient.


The use of antiepileptic medications is not recommended after first time febrile seizures as the risks outweigh the benefits in this patient population (5,6).


Get the Point

- Simple febrile seizures are a clinical diagnosis and do not require head imaging or labs

- COUNSEL THE PARENTS! Simple febrile seizures usually get to go home, but this could

happen again and it is scary, but it doesn’t mean their child will have epilepsy (% around

general population)

- There is no standard approach for complex febrile seizures, consult your friendly

neighborhood pediatric neurologist to help guide necessary workup

- Antipyretics reduce the recurrence of febrile seizures in the short term after first febrile

seizure


References

1. National Institute of Neurological Disorders and Stroke. Febrile Seizures Fact Sheet.

https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Febrile-

Seizures-Fact-Sheet Accessed on September 24, 2020.

2. Centers for Disease Control and Prevention. Vaccines Safety. Febrile seizures and childhood vaccines. CDC. https://www.cdc.gov/vaccinesafety/concerns/febrile-seizures.html Accessed on September 24, 2020

3. Hesdorffer DC, Benn EK, Bagiella E, Nordli D, Pellock J, Hinton V, Shinnar S . Distribution of febrile seizure duration and associations with development, FEBSTAT Study Team. Ann Neurol. 2011;70(1):93.

4. Millichap J., Nordli D., Dashe J., Clinical features and evaluation of febrile seizures.

UpToDate. https://www.uptodate.com/contents/clinical-features-and-evaluation-of-febrile-seizures?search=febrile%20seizure&source=search_result&selectedTitle=1~133&usage_type=default&display_rank=1 Accessed on September 24, 2020.

5. Neurodiagnostic evaluation of the child with a simple febrile seizure. Subcommittee on Febrile Seizures, American Academy of Pediatrics. Pediatrics. 2011;127(2):389.

6. Smith D., Sadler K., Benedum M. Febrile Seizures: Risks, Evaluation, and Prognosis.

American Family Physician. 2019.;99 (7): 446-450.

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