Abstracts

Hippocampal sclerosis (HS) on MR imaging is associated with reduced hippocampal volume and increased T2-relaxation time. Diffusion tensor imaging (DTI) provides additional information on tissue microstructure. We perform a voxel-based (VB) analysis of DTI in temporal lobe epilepsy patients with unilateral HS. The common framework will allow comparison with VB morphometry (VBM) and VB T2-relaxometry (VBR). We assessed 15 healthy controls and 12 left HS patients at a 3T GE scanner. DTI was performed with 28 directions (b=1100 s/mm3). An eight-echo CPMG sequence was used for T2-relaxometry, and a 3D SPGR sequence for morphometry. Data were analysed using FSL and SPM2 (Wellcome Department of Cognitive Neurology, London). For DTI, we assessed fractional anisiotropy and diffusivity. For VBM, we used an optimised protocol (1) and assessed both the gray and white matter segment. VBR was performed as described in our earlier manuscript (2). Threshold for all analyses was p[lt]0.001. Voxels were counted in ipsilateral peri-hippocampal and temporal lobe regions. DTI changes in left HS were more pronounced than VBM or VBR abnormalities. The table shows the number of activated voxels with each technique. Reduced anisotropy was found in the left uncinate fasciculus, anterior temporal lobe (ATL) and corpus callosum. Increased diffusivity was found in the ATL and parahippocampal white matter. Gray matter volume loss was detected in the hippocampus proper, white matter volume loss in the ATL. VBR showed a T2 increase in the lateral and ATL white matter. The most prominent abnormality in the hippocampus proper was a volume deficit. Additionally, there were extensive temporal lobe white matter abnormalities. The DTI changes close to the hippocampus may be secondary, and associated with memory deficits and seizure circuits. The DTI, VBM and VBR abnormalities in ATL may be primary, and associated with temporal lobe development (3).
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Mitchell LA, et al. AJNR Am J Neuroradiol 2003;24:1670-1677.[table1] (Supported by Neurosciences Victoria, the NHMRC Australia and the Brain Imaging Research Foundation. We thank the subjects for their participation in this study.)