Skip to Main Content

Chapter 4. Febrile Seizures

Zhou Liu; James D. Geyer; Paul R. Carney

Febrile seizures are convulsions induced by a fever in infants or young children. They are the most common type of seizure during childhood. While febrile seizures are usually benign, they are often very upsetting to parents. There are several operational definitions of febrile seizures

  1. American Academy of Pediatrics Practice Parameter: "A simple febrile seizure is a generalized seizure occurring in an infant or child between the ages of six months and five years, lasting less than 15 minutes and occurring only once in 24 hours. The child should not have an intracranial infection or a severe metabolic disturbance."1

  2. The International League Against Epilepsy (ILAE): "A seizure occurring in childhood after one month of age, associated with a febrile illness not caused by an infection of the central nervous system, without previous neonatal seizures or a previous unprovoked seizure, and not meeting criteria for other acute symptomatic seizures."2

Both definitions exclude seizures with fever in children who have previously had seizures unrelated to fever and do not exclude children with prior neurological impairment. Although these two definitions are similar, there is a discrepancy regarding the lower age limit of first seizure onset (3 months versus 1 month). The three critical elements of febrile seizures are shown in Table 4-1.

Table 4–1. Three Critical Elements of Febrile Seizures
View Table||Download (.pdf)
Table 4–1. Three Critical Elements of Febrile Seizures
Age of first seizure onset
  • Typically between 6 months and 5 years with the peak incidence at 18 months1
  • Febrile seizures occuring after 4 years account for 6-15%20
  • Febrile seizure occurring before 3 months or after 6 years are atypical and the outcome of these febrile seizures may not be as benign as typical febrile seizures
Temperature of a fever
  • Both AAP and ILAE definitions do not provide a specific temperature criterion for its diagnosis
  • An axillary temperature of either >38.5°C or >37.8°C as a simple cutoff level has been proposed to diagnose febrile seizures, but consensus is lacking
  • The majority of children with febrile seizures have rectal temperatures greater than 102°F or 38.5°C and most febrile seizures occur during the first day of fever
  • There are no data to support the rate of temperature rise as being more important than the peak temperature achieved8
Seizures
  • Seizures are caused by paroxysmal synchronous firing of large neuronal networks in the brain, resulting in an alteration in mental status, tonic or clonic convulsions, and various other associated symptoms
  • Most common type of febrile seizures are generalized seizures involving both sides of the body
  • Simple partial seizures or complex partial seizures may occur, and these seizures might become generalized after a partial onset
  • Febrile seizures with partial onset are usually less benign than generalized febrile seizures

Epidemiologic studies show that approximately 3% to 4% of children have at least one febrile seizure by 7 years of age.3 There ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.

This site uses cookies to provide, maintain and improve your experience. MH Privacy Center Close