Febrile seizures are diagnosed when seizures occur in children 6 months to 5 years of age who have fever (temperature > 38° C) that is not caused by a central nervous system infection and who have had no previous afebrile seizures. Diagnosis is by exclusion of other causes. Febrile seizures lasting < 5 minutes are managed with supportive care. Seizures lasting ≥ 5 minutes are treated with IV lorazepam, rectal diazepam, or intranasal midazolam and, if persistent, IV fosphenytoin, phenobarbital, valproate, or levetiracetam. Maintenance medications are usually not indicated. Children with febrile seizures have a slightly increased risk of developing epilepsy. 5 minutes are treated with IV lorazepam, rectal diazepam, or intranasal midazolam and, if persistent, IV fosphenytoin, phenobarbital, valproate, or levetiracetam. Maintenance medications are usually not indicated. Children with febrile seizures have a slightly increased risk of developing epilepsy.
(See also Neonatal Seizure Disorders.)
Febrile seizures occur in approximately 2 to 5% (1) of children 6 months to 5 years of age, and most occur between 12 months and 18 months of age.
Febrile seizures may be simple or complex:
Simple febrile seizures last < 15 minutes, have no focal features, and do not recur within a 24-hour period; most febrile seizures are simple.
Complex febrile seizures last ≥ 15 minutes continuously or with pauses; or have focal features; or have focal onset; or recur within 24 hours.
Risk factors for febrile seizures include the following:
Can occur during non–central nervous system viral infections and less commonly during bacterial infections (primarily because certain viral infections such as human herpesvirus 6 [HHV-6] and influenza are associated with a very high degree of pyrexia)
Sometimes occur after certain vaccinations, such as measles/mumps/rubella (2)
Genetic and familial factors appear to increase susceptibility to febrile seizures. Monozygotic twins have a much higher concordance rate than dizygotic twins. Several genes associated with febrile seizures have been identified (3).
A history of developmental delay is associated with an increased risk of epilepsy after febrile seizure (4).
General references
1. Christensen KJ, Dreier JW, Skotte L, et al. Birth characteristics and risk of febrile seizures. Acta Neurol Scand. 2021;144(1):51-57. doi:10.1111/ane.13420
2. Klein NP, Fireman B, Yih WK, et al. Measles-mumps-rubella-varicella combination vaccine and the risk of febrile seizures. Pediatrics. 2010;126(1):e1-e8. doi:10.1542/peds.2010-0665
3. Saghazadeh A, Mastrangelo M, Rezaei N. Genetic background of febrile seizures. Rev Neurosci. 2014;25(1):129-161. doi:10.1515/revneuro-2013-0053
4. Nelson KB, Ellenberg JH. Predictors of epilepsy in children who have experienced febrile seizures. N Engl J Med. 1976;295(19):1029–1033. doi:10.1056/NEJM197611042951901
Symptoms and Signs of Febrile Seizures
Often, febrile seizures occur during the initial rapid rise in body temperature, and most develop within 24 hours of fever onset. In general, higher temperature appears to be more important in influencing the onset of seizures compared to the relative rate of its increase. Typically, seizures are generalized; most are clonic, but some manifest as periods of atonic or tonic posturing.
A postictal period of a few minutes is common but may last as long as a few hours. Drowsiness is common during this period; confusion and agitation are less common but are possible. If the postictal period is longer than an hour or if children have focal findings (eg, diminished movement on one side) during this period, they should be evaluated for an underlying acute central nervous system (CNS) disorder. Recovery to baseline neurologic status is generally rapid.
Febrile status epilepticus is continuous or intermittent seizures that last ≥ 30 minutes. When status epilepticus manifests as intermittent seizures, the seizures occur without neurologic recovery between seizures. Children with febrile status epilepticus are at risk of brain damage, particularly acute hippocampal injury that can progress to sclerosis, potentially resulting in the development of temporal lobe epilepsy (1).
Symptoms and signs reference
1. Hesdorffer DC, Shlomo S, Lax DN, et al: Risk factors for subsequent febrile seizures in the FEBSTAT study. Epilepsia 57(7):1042–1047, 2016. doi: 10.1111/epi.13418
Diagnosis of Febrile Seizures
Evaluation to exclude other etiologies
Febrile seizures is assigned as a diagnosis after exclusion of other causes. A fever may trigger seizures in children with previous afebrile seizures; such events are not termed febrile seizures because these children have an underlying tendency to have seizures.
Routine testing is not required for simple febrile seizures other than to determine the source of the fever, but if children have complex febrile seizures, neurologic deficits, or signs of a serious underlying disorder (eg, meningitis, metabolic disorders), further evaluation should be performed (1, 2).
Evaluation to exclude other disorders is based on clinical context:
Cerebrospinal fluid (CSF) analysis: To rule out meningitis and encephalitis in younger infants only when clinical features strongly suggest their presence (eg, in those with meningeal signs or signs of CNS depression) or in those who have seizures after several days of febrile illness; must also be considered if children are not fully immunized or are taking antibiotics
Serum glucose, sodium, calcium, magnesium, and phosphorus and liver and kidney function tests: To rule out metabolic disorders especially if the history includes recent vomiting, diarrhea, or impaired fluid intake; if there are signs of dehydration or edema; or if a complex febrile seizure occurs
Blood and urine cultures: To determine a possible cause of fever (3)
Brain MRI: If neurologic examination detects focal abnormalities, if focal features occur during the seizure or postictal period, or if the postictal depression of sensorium is prolonged; not recommended in children with simple febrile seizures
Electroencephalography (EEG): If febrile seizures have focal features or are recurrent (EEG typically does not identify specific abnormalities or help predict recurrent seizures and is not recommended after an initial simple febrile seizure in children with a normal neurologic examination.)
A diagnostic evaluation based on the underlying disorder is done if children have an already identified developmental or neurologic disorder (usually, a diagnosis of febrile seizure is not correct in such cases).
Diagnosis references
1. Smith DK, Sadler KP, Benedum M. Febrile Seizures: Risks, Evaluation, and Prognosis. Am Fam Physician. 2019;99(7):445-450.
2. Subcommittee on Febrile Seizures; American Academy of Pediatrics. Neurodiagnostic evaluation of the child with a simple febrile seizure. Pediatrics. 2011;127(2):389-394. doi:10.1542/peds.2010-3318
3. Pantell RH, Roberts KB, Adams WG, et al. Evaluation and Management of Well-Appearing Febrile Infants 8 to 60 Days Old [published correction appears in Pediatrics. 2021 Nov;148(5):e2021054063. doi: 10.1542/peds.2021-054063.]. Pediatrics. 2021;148(2):e2021052228. doi:10.1542/peds.2021-052228
Treatment of Febrile Seizures
Antipyretic therapy
Supportive therapy for seizure duration < 5 minutes
Antiseizure medications and sometimes intubation for seizure duration ≥ 5 minutes
All children should be receive antipyretic therapy until the fever subsides because lowering the temperature can help prevent another febrile seizure during the immediate illness for acute resolution of febrile status epilepticus. However, giving an antipyretic at the beginning of a febrile illness has not been shown to prevent a febrile seizure (1).
Management of febrile seizures is supportive if seizures last < 5 minutes.
Seizures lasting ≥ 5 minutes may require medications to terminate them, with careful monitoring of circulatory and respiratory status. Intubation may be necessary if the seizure persists despite therapy or if antiseizure therapy leads to apnea.
Medication is usually administered by IV, with a short-acting benzodiazepine (eg, lorazepam repeated every 5 to 10 minutes for up to 3 doses). Fosphenytoin may be given over 15 to 30 minutes if the seizure persists. Medication is usually administered by IV, with a short-acting benzodiazepine (eg, lorazepam repeated every 5 to 10 minutes for up to 3 doses). Fosphenytoin may be given over 15 to 30 minutes if the seizure persists.
If IV access is not available or the child is in a prehospital setting and older than 2 years, diazepam rectal gel or intranasal midazolam may be given. If IV access is not available or the child is in a prehospital setting and older than 2 years, diazepam rectal gel or intranasal midazolam may be given.
Phenobarbital, valproate, or levetiracetam can also be used to treat a persistent seizure.Phenobarbital, valproate, or levetiracetam can also be used to treat a persistent seizure.
Some clinicians prescribe diazepam rectal gel for children with recurrent febrile seizures (see Prevention of Febrile Seizures) to be given by the parents at home for a prolonged febrile seizure.
Treatment reference
1. Corsello A, Marangoni MB, Macchi M, et al. Febrile Seizures: A Systematic Review of Different Guidelines. Pediatr Neurol. 2024;155:141-148. doi:10.1016/j.pediatrneurol.2024.03.024
Prognosis for Febrile Seizures
Recurrence and subsequent epilepsy
Overall recurrence rate of febrile seizures is approximately 20 to 35% (1). Risk of recurrence is higher if children are < 1 year of age when the initial seizure occurs, with an increasing number of episodes of febrile seizures, or if children have first-degree relatives who have had febrile seizures.
Risk of developing an afebrile seizure disorder after having ≥ 1 simple febrile seizures is approximately 2 to 6%—slightly higher than the baseline risk of developing epilepsy (approximately 2% in children overall) (2). Most of the increased risk occurs in children who have additional risk factors (eg, complex febrile seizures, family history of seizures, developmental delay); in these children, risk is up to 10% (3). It is unclear whether having a febrile seizure can itself permanently lower the seizure threshold or whether some underlying factors predispose children to both febrile and nonfebrile seizures.
Neurologic sequelae
Simple febrile seizures themselves are not thought to cause neurologic abnormalities. However, in some children, a febrile seizure may be the first manifestation of an underlying seizure disorder or as yet unrecognized neurologic disorder. The signs of the disorder may be identified retrospectively or may not appear until later. In either case, the febrile seizure is not thought to be causal.
Febrile status epilepticus may be associated with damage to vulnerable parts of the brain such as the hippocampus.
Prognosis references
1. Berg AT, Shinnar S, Darefsky AS, et al. Predictors of recurrent febrile seizures. A prospective cohort study. Arch Pediatr Adolesc Med. 1997;151(4):371-378. doi:10.1001/archpedi.1997.02170410045006
2. Kim JS, Woo H, Kim WS, Sung WY. Clinical Profile and Predictors of Recurrent Simple Febrile Seizure. Pediatr Neurol. 2024;156:4-9. doi:10.1016/j.pediatrneurol.2024.04.001
3. Nelson KB, Ellenberg JH. Predictors of epilepsy in children who have experienced febrile seizures. N Engl J Med. 1976;295(19):1029–1033. doi:10.1056/NEJM197611042951901
Prevention of Febrile Seizures
Parents of a child who has had a febrile seizure should be advised to carefully monitor their child's temperature during illnesses. Most clinicians advise giving antipyretics if temperature is elevated (even though controlled studies have not shown that this treatment prevents febrile seizures from recurring).
Maintenance antiseizure medications to prevent recurrent febrile seizures or development of afebrile seizures is usually not indicated (1). However, situations to consider use of antiseizure medications (2) include children who have
Complex febrile seizures and neurologic deficits
Strong family history of epilepsy and recurrent simple or complex febrile seizures
Febrile status epilepticus
Febrile seizures occurring at least once per quarter
Prevention references
1. 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
2. Piña-Garza J, James K: Paroxysmal Disorders: Febrile seizures. In Fenichel's Clinical Pediatric Neurology: A Signs and Symptoms Approach, ed. 8. Philadelphia, Elsevier, 2019, p. 18.
Key Points
Febrile seizures are seizures that occur in neurologically normal children 6 months to 5 years of age with fever (temperature > 38° C) that is not caused by a central nervous system infection and who have no previous afebrile seizures.
Simple febrile seizures last < 15 minutes, have no focal features, and do not recur within a 24-hour period.
Complex febrile seizures last ≥ 15 minutes continuously or with pauses; or have focal features; or focal onset; or recur within 24 hours.
Routine testing is not required for simple febrile seizures, but if children have complex seizures, neurologic deficits, or signs of a serious underlying disorder (eg, meningitis, metabolic disorders), testing should be done.
Seizures lasting ≥ 5 minutes require medication (eg, lorazepam repeated every 5 to 10 minutes for up to 3 doses).5 minutes require medication (eg, lorazepam repeated every 5 to 10 minutes for up to 3 doses).
Risk of developing an afebrile seizure disorder after having ≥ 1 simple febrile seizures is approximately 2 to 6%.
Giving an antipyretic at the beginning of a febrile illness has not been shown to prevent a febrile seizure.
