Abstracts

The hypothesized consequences of febrile status epilepticus (FSE) include hippocampal injury with subsequent mesial temporal sclerosis (MTS) and temporal lobe epilepsy (TLE). As part of a multicenter prospective study of FSE, we have reviewed brain MRI scans done soon after an initial episode of FSE. The objective was to determine the incidence of visually detectable hippocampal abnormalities in the hippocampi of these infants. Infants presenting to the hospital with FSE were imaged acutely following the episode of FSE. FSE was defined as 30 minutes of continuous or intermittent febrile seizures without recovery of normal mental status. The T2 weighted fast spin echo oblique coronal image series of these acute MRIs were examined visually for definite increases in hippocampal T2 signal intensity and size. MRI scans were available from 64 subjects done within 1 to 34 days following FSE. Forty-six or 72% were done within 72 hours after the FSE. Four subjects had definitely increased T2 throughout one hippocampus with normal or increased volume. One had increased signal with atrophy suggestive of MTS. Ten subjects had subtle increased T2 signal in part of one hippocampus. Eleven subjects had mildly dysmorphic hippocampi with unilateral left hippocampal malrotation seen in 7 of the 10. Malrotation was characterized by globular shape, loss of internal architecture, medial displacement and inferiorly displaced fornix (Barsi et al. Neuroradiology (2000) 42:339-345). Three of the 10 subjects with subtle increased signal also had hippocampal malrotation of the affected hippocampus. These early results suggest hippocampal T2 signal abnormalities are not uncommon (23 %) in children with FSE and can at times be severe. In addition, subtle structural abnormalities of the hippocampi were unusually common in this group and the significance of this finding is still unclear. Long term follow up of these infants with re-imaging is planned to determine the correlation of these abnormalities with the development of MTS or TLE. (Supported by NINDS - R01 NS43209 Consequences of Prolonged Febrile Seizures in Childhood.)