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COMMENTARY |
Department of Pediatrics, Connecticut Children's Medical Center, Hartford, Connecticut
Abbreviations: CT, computed tomography
The most common seizures experienced by young children are febrile seizures,1,2 which affect up to 4% to 5% of children 
5 years old in the United States and Europe.1,2 In other portions of the world, the frequency may exceed 10% to 15%.2 Febrile seizures are defined as seizures associated with a febrile illness in the absence of central nervous system infection or acute electrolyte imbalance in children >1 month of age without previous afebrile seizures.3 These seizures have been defined further as simple or complex: simple febrile seizures are generalized seizures that last <15 minutes and do not recur within 24 hours,3,4 and complex febrile seizures are defined as focal and/or prolonged (>15 minutes) and/or occur in a series over 24 hours.3,4 The associated morbidity and mortality from febrile seizures is extremely low, with no associated adverse cognitive outcomes even when the seizures are prolonged.1,5,6 Risk factors predicting first febrile seizure, recurrent febrile seizures, and subsequent epilepsy have been well enumerated1 (see Table 1).
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These findings both complement and amplify available published data on children with complex febrile seizures (see Table 2). Previously published studies were comprised of children presenting to emergency departments with seizures that were later subdivided into first seizure, epilepsy, simple febrile seizures, complex febrile seizures, and seizures that were symptomatic or idiopathic. The current study is only the second large-scale study that focused on the prospective recruitment of subjects with complex febrile seizures.
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Previously published retrospective data have demonstrated variable utilization rates of neuroimaging for subjects who presented with complex febrile seizures (Table 2). Children with complex febrile seizures are not easily extrapolated from some composite and heterogeneous studies. However, there are few subjects identified with abnormalities on neuroimaging (CT scanning used to a greater degree than MRI). These abnormalities have generally been without requirement for additional medical or surgical intervention, similar to that demonstrated in the study by Teng et al.7 There are isolated case reports of brain abscess, nonaccidental trauma, intracranial hemorrhage, encephalitis, etc that present as what was thought to be a complex febrile seizure. Clinical course later identified the child as requiring additional evaluation. Prolonged alteration in mental status, meningismus, persisting postictal focal deficits, and toxic appearance, among others, should raise clinical suspicion. Therefore, from a practical point of view, in an emergency-department setting the question that should be asked is, "what important and clinically relevant data requiring immediate intervention will be learned by obtaining an emergency CT scan for this patient at this time?" The answer would most often seem to be none. There are always individual patients who may have clinically significant neuroimaging findings that would be better evaluated with MRI at presentation or at a later time. These treatment decisions need to be determined individually to avoid the impulse to routinely obtain a CT scan in each child presenting with a complex febrile seizure. As the authors in the current study and previous authors have emphasized, underlying medical conditions such as meningitis, encephalitis, and/or abscess need to be suspected clinically and evaluated for specifically in this context.1,2,6,15 Hospitalization and continued observation may be necessary. Later neuroimaging with MRI may be considered in children who present with complex febrile seizures if risk factors for subsequent epilepsy exist or there is a need to further evaluate underlying neurologic symptoms, neurodevelopmental abnormalities, or symptomatic seizures (brain dysgenesis, neurocutaneous syndrome, etc). It remains controversial whether febrile seizures, particularly prolonged complex febrile seizures, cause the later development of mesial temporal sclerosis.16 Retrospective studies have suggested that complex febrile seizures are a causative factor, whereas prospective studies have not.16 Genetic and environmental factors exert an up to now less-well-studied but significant influence.16
Factors unrelated to the clinical evaluation of the patient are often at work when neuroimaging is obtained in an emergency-department setting. Among these include insistence by parents because of high anxiety, the relative ease of CT scanning availability, and relative lack of accessibility to specialty consultation. Although neuroimaging may help to allay some anxiety regarding serious intracranial pathology, it is unnecessary in most circumstances and may carry with it a longer-term risk of radiation-induced morbidity. Although these radiation risks are small for the individual, they are appreciable when you consider the population-based estimates of lifetime cancer mortality risks.17,18 There is generally an additional need for the administration of conscious sedation. This itself carries additional risks both directly from possible respiratory depression and indirectly by obscuring the clarity of subsequent mental status examination. Furthermore, MRI would be a more sensitive and clinically useful neuroimaging tool for most patients who are undergoing neurologic evaluation in the absence of suspected trauma or an immediate neurosurgical problem.
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FOOTNOTES |
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Address correspondence to Francis J. DiMario, Jr, MD, Department of Pediatrics, Connecticut Children's Medical Center, 282 Washington St, Suite 2A, Hartford, CT 06106. E-mail: fdimari{at}ccmckids.org
The author has indicated he has no financial relationships relevant to this article to disclose.
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REFERENCES |
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  B. Damle, D. Hewlett Jr, P.-H. Hsyu, M. Becker, and A. Petersen Pharmacokinetics of nelfinavir in subjects with hepatic impairment. J. Clin. Pharmacol., November 1, 2006; 46(11): 1241 - 1249. [Abstract] [Full Text] [PDF]
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 J. G. Millichap and B. Pate Neuroimaging After First Complex Febrile Seizure May Be Unnecessary AAP Grand Rounds, May 1, 2006; 15(5): 55 - 56. [Full Text] [PDF]
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 Intracranial Pathology and Complex Febrile Seizures Journal Watch (General), February 21, 2006; 2006(221): 2 - 2. [Full Text]
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