Abstracts

Rationale: In TLE, there is evidence for widespread damage in the limbic network including from pathological or imaging studies. In our previous studies for prolonged febrile seizures (PFSs), we found abnormalities in hippocampus as well as thalamus by diffusion weighted images (DWI) during acute period. We performed voxel-based morphometry (VBM) to assess structural abnormalities in children who had DWI abnormalities after PFS. Methods: We performed DWIs within 5 days of PFS in 24 children with a first episode of PFSs. We scanned MRI 3D T1-weighted images 1 year after the PFS. VBM was carried out using SPM5 software. MRI was segmented to images of gray matter, white matter and CSF. The gray matter images were smoothed with a 6 mm FWHM isotropic Gaussian kernel. We compared smoothed gray matter images of 5 patients and 13 normal controls. The threshold for the t statistic map was set at p=0.001 and extent threshold at 50 voxels. Results: DWI showed unilateral hippocampal abnormalities in 7 of 24 patients. We performed VBM in 5 of these patients. Two patients also had abnormalities in the thalamus ipsilateral to the hippocampal abnormalities on DWI. One patient had abnormalities in the right side, and others had abnormalities in the left on MRI. Therefore, in the VBM, MRI of the patient with right side abnormalities was flipped in the right/left direction in order to pool the abnormalities on the left side. VBM revealed gray matter volume reduction in the left hippocampus, left temporo-frontal cortices, and anterior part of thalamus. Thalamic volume reduction was prominent in the left side, but also seen in the right side. Conclusions: VBM revealed persistent structural changes in limbic networks and neocortices in patients who had had transient DWI abnormalities after PFS. Limbic structural abnormalities after PFS may play a role in the development of MTLE. DWI, Volumetry and VBM could help identifying patients who are at risk of developing epilepsy.