Outbreaks, Alerts and Hot Topics

Febrile Seizures

Author: Rohan Akhouri, MD, MPH | Pediatric Emergency Medicine Fellow, PGY-4

Column Editor: Angela Myers, MD, MPH | Director, Division of Infectious Diseases | Professor of Pediatrics, UMKC School of Medicine | Medical Editor, The Link Newsletter

Febrile seizures occur between 6 months and 5 years of age in association with a fever (≥38°C) without another identifiable source for seizures.¹ Febrile seizures affect 2%-5% of children between the ages of 6 months and 5 years,^2,3 making it the most common neurological disorder in this age group. Febrile seizures can be differentiated into two categories – simple and complex – based on their presentation. Across all ages, seizures make up 1%-2% of all emergency department visits per year, a subset of which are febrile seizures.^4,5

Simple febrile seizures present as generalized tonic-clonic seizures lasting <15 minutes without recurrence in a 24-hour period. These account for about 80%-85% of all febrile seizures.^3,6

Complex febrile seizures are focal, prolonged (>15 minutes), with a prolonged postictal state, and/or recurrence within a 24-hour period.^3,6

There is ongoing discussion on the underlying etiology of febrile seizures. Though there is a genetic basis, the mode of inheritance is not yet known. The prevailing thought is that acute infections with high fevers, in the setting of a lower seizure threshold in young children, lead to febrile seizures.⁷ Approximately 80% of febrile seizure cases occur with a viral infection. Additionally, the risk of febrile seizures increases a few days after the administration of DTaP-IPV-Hib, MMRV or PCV, though this risk is transient and small.¹ Diagnosis and evaluation of a febrile seizure requires a thorough history and physical examination to identify and rule out other causes for seizures, including trauma, meningitis and genetic syndromes. A subset of patients with febrile seizures outside of the expected ages are considered part of a rare familial epilepsy syndrome called genetic epilepsy with febrile seizures plus (GEFS+). Affected individuals have a range of phenotypes from simple febrile seizures to severe epileptic encephalopathy,^8,9 and will require assessment and follow-up with a neurologist. Depending on the degree of severity, patients diagnosed with GEFS+ warrant further evaluation with an outpatient EEG and MRI, and occasionally require anti-epileptic medications.

Most patients presenting after a simple febrile seizure has occurred have returned to baseline by the time of arrival. According to the American Academy of Pediatrics (AAP) guidelines, a simple febrile seizure in a well-appearing child does not require additional lab or imaging evaluation.³ For patients who are ill-appearing, lab and imaging evaluation should focus on diagnosis of the underlying cause. Similarly, guidelines for complex febrile seizures should focus on evaluating for an underlying cause. There is limited evidence for performing a lumbar puncture (LP) in both simple and complex febrile seizures. The AAP recommends considering an LP for unimmunized patients 6-12 months of age. For older patients the AAP recommends an LP if meningitis is a concern.^6,10

There is no recommended role for emergent head imaging (CT, MRI) for well-appearing patients with a simple febrile seizure, though a non-urgent outpatient MRI is recommended for complex febrile seizures with postictal neurological deficits and concerns for abnormal neurodevelopment.^6,10 One-third of patients with simple febrile seizures are at risk for recurrence; however, there is no significant increased risk as compared to the general population for development of epilepsy, encephalitis or long-term neurological deficits. Patients with complex febrile seizures are at increased risk for future epilepsy,^1,10 and those with high risk factors – abnormal neurodevelopment, family history of epilepsy – should follow up with a neurologist and complete an outpatient EEG.¹¹

In summary, febrile seizures are the most common neurological disorder in healthy children between 6 months and 5 years of age, with the majority being simple febrile seizures. Simple febrile seizures in well-appearing children do not require additional evaluation, and management is focused on symptomatic care. Children who have a complex febrile seizure should be evaluated for underlying causes with outpatient EEG and MRI if there are associated high risk factors. Management is focused on treatment of the underlying causes, and anti-epileptic medications are not routinely started with normal findings.

References:

1. Leung AKC, Hon KL, Leung TNH. Febrile seizures: an overview. Drugs Context. https://doi.org/10.7573/dic.212536
2. Paul SP, Seymour M, Flower D, Rogers E. Febrile convulsions in children. Nurs Child Young People. 2015;27(5):14-15. https://doi.org/10.7748/ncyp.27.5.14.s16
3. Steering Committee on Quality Improvement and Management, Subcommittee on Febrile Seizures American Academy of Pediatrics. Febrile seizures: clinical practice guideline for the long-term management of the child with simple febrile seizures. Pediatrics. 2008;121(6):1281-1286. doi:10.1542/peds.2008-0939
4. Martindale JL, Goldstein JN, Pallin DJ. Emergency department seizure epidemiology. Emerg Med Clin North Am. 2011;29(1):15-27. https://doi.org/10.1016/j.emc.2010.08.002
5. Pallin DJ, Goldstein JN, Moussally JS, Pelletier AJ, Green AR, Camargo CA. Seizure visits in US emergency departments: epidemiology and potential disparities in care. Int J Emerg Med. 2008;1(2):97-105.
6. Subcommittee on Febrile Seizures; American Academy of Pediatrics. Neurodiagnostic evaluation of the child with a simple febrile seizure. Pediatrics. 2011;127(2):389-394.
7. Hirtz DG. Febrile seizures. Pediatr Rev. 1997;18(1):5-9. https://doi.org/10.1542/pir.18.1.5
8. Laino D, Mencaroni E, Esposito S. Management of pediatric febrile seizures. Int J Environ Res Public Health. 2018;15(10):2232. doi:10.3390/ijerph15102232
9. https://www.epilepsy.com/learn/types-epilepsy-syndromes/genetic-epilepsy-febrile-seizures-plus
10. Whelan H, Harmelink M, Chou E, et al. Complex febrile seizures-a systematic review. Dis Mon. 2017;63(1):5-23.
11. Hofert SM, Burke MG. Nothing is simple about a complex febrile seizure: looking beyond fever as a cause for seizures in children. Hosp Pediatr. 2014;4(3):181-187. https://doi.org/10.1542/hpeds.2013-0098