Abstracts

Rationale: There is continued debate on whether status epilepticus can cause hippocampal damage leading to temporal lobe epilepsy. We previously showed that in about half of children with prolonged febrile seizures (PFS) lasting for 60 min. or longer, and hippocampal and thalamic hyperintensity on diffusion-weighted imaging (DWI), volumetric MRI reveals significant hippocampal atrophy within the first year. The purpose of this study was to assess metabolic abnormalities of the limbic circuitry using FDG-PET in children after PFS.Methods: We performed FDG-PET in three patients with hippocampal DWI abnormalities two years after PFS. FDG-PET was evaluated visually. We also performed a region of interest (ROI) analysis in lateral temporal lobe, hippocampus, amygdala, frontal lobe, parietal lobe, occipital lobe, thalamus, lenticular nucleus, and cerebellar hemisphere. Radioactivity in each ROI was measured and an asymmetry index was calculated with respect to the side of the hippocampal DWI abnormality. Asymmetries above 10 % were considered significant in this study.Results: Two patients had visually detectable hypometabolism in the temporal lobe ipsilateral to the side of DWI abnormality. ROI analysis revealed reduced activity in the ipsilateral hippocampus of all patients ranging from 11 to 22 %. In addition, abnormal AI was seen in the ipsilateral lateral temporal lobe and the thalamus in one patient, and in the amygdala in the other. Two of the three patients had developed epileptic seizures before the PET study.Conclusions: FDG-PET shows hypometabolism in the temporal lobes of children two years after an episode of PFS on the side of DWI abnormalities. The early presence of both structural and functional damage within the temporal lobe suggest their role as promoters of epileptogenesis.