Finally, an ill child with a fever who has a seizure may have had a febrile seizure. During the assessment, always be a detective and look for other causes like hypoxia, hypoglycemia, brain injury or intoxication.As you gather assessment information, you may be able to eliminate some causes from consideration.REQUENCY OF FEBRILE SEIZURES. Febrile seizures are a relatively common occurrence in children ages 5 months to 5 years and are most frequently caused by viral illness. 4 Thirty percent of seizures in this age group are caused by fever; the next highest cause is failure to take prescribed medications.