Are MRI-detected brain abnormalities associated with febrile seizure type?

OBJECTIVE: Whether magnetic resonance imaging (MRI) is informative in febrile seizures (FS) is unknown. We undertook a study to determine the frequency of MRI-detected brain abnormalities and to evaluate their association with FS type and with specific features of complex FS.
METHODS: A prospective cohort study, from 1999 to 2004, included children with first FS from one Pediatric Emergency Department. MRI of the brain was performed within 1 week of the seizure. FS type was categorized by experts blind to the prior clinical history and MRI results. MRI examinations were read blind to the child's clinical history and FS type, and interviewers were blind to MRI results.
RESULTS: In 159 children with a first FS, imaging abnormalities occurred in 12.6% (N = 20). Eight of the 54 with complex FS had imaging abnormalities compared to 12 of the 105 with simple FS (n.s.). Compared to children with simple FS, children with both focal and prolonged FS (N = 14) were more likely to have imaging abnormality (OR = 4.3, 95% CI = 1.2-15.0), even after adjustment for abnormal neurological examination. Imaging abnormalities included those known to be associated with seizures (e.g., focal cortical dysplasia) and those not typically associated with seizures (e.g., subcortical focal hyperintensities > or = 5 mm). DISCUSSION: Our data suggest that brain abnormalities may lower seizure threshold in febrile children, predisposing to the development of FS. Clinical management was unaffected and therefore these data do not alter the recommendation that MRI is unnecessary in children with FS, without some other neurological indication.