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The National Institutes of Health (NIH) defines febrile seizure as an event in infancy or childhood usually occurring between 3 months and 5 years of age associated with a fever but without evidence of intracranial infection or defined cause for the seizure. The International League Against Epilepsy (ILAE) further refined the definition to include infants older than 1 month of age without prior neonatal seizures or unprovoked seizures who did not meet criteria for acute symptomatic seizures. Febrile seizures occur in approximately 2% to 5% of infants and young children in the United States and as many as 9% to 14% of children in Japan, India, and Guam, rendering it the most common neurologic disorder in this age group and the most common type of convulsive event in children younger than 5 years of age.
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Febrile seizures are defined by the age of the patient at presentation and the clinical context in which they occur. Febrile seizures can occur in children age 1 month to 6 years, with a peak incidence at 18 months old. Ninety percent of children with febrile seizures will have their first event prior to reaching the age of 3 years. Alternate diagnoses should be considered in individuals who present after this age.
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Febrile seizures occur in association with a temperature of greater than 38°C (100.4°F) prior to or shortly after the event. The seizures often happen very early in the course of illness, and there may not be a history of preceding fever.
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A diagnosis of febrile seizures is excluded if the affected child has a prior history of afebrile seizures, or if the seizure occurs in the context of a central nervous system infection or acute metabolic abnormality that can cause seizures.
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CLASSIFICATION OF FEBRILE SEIZURES
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Febrile seizures are classified as either “simple” or “complex” based on clinical features including semiology, duration, and frequency (Table 551-1). These classifications are important as they guide the diagnostic workup and have prognostic implications. The majority of febrile seizures are simple febrile seizures, which are generalized seizures lasting < 15 minutes in duration that occur only once in a 24-hour period. They usually last < 5 minutes and consist of clonic movements, although atonic or tonic seizures are sometimes seen. Postictal drowsiness usually resolves within 5 to 10 minutes depending on the duration of the seizure.
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Conversely, 20% to 30% of febrile ...