Abstracts

Rationale: Frontal lobe epilepsy (FLE) with frontal focal cortical dysplasia (FCD) is associated with refractory seizures and involvement of somatosensitive cortex. High resolution MRI investigations have disclosed focal cortical abnormalities and SPECT studies have revealed ictal activation in contralateral cerebellum (cerebellar diaschisis) in FLE. We aimed to investigated GM abnormalities in both cortex and cerebellum, with 2 different approaches, Voxel Based Morphometry(VBM) and Cortical analysis. Methods: Statistical analysis was conducted with general linear model (two sample T-test) comparing 11 patients with left FLE and FCD (7women, 34 12years) to 25 controls (15women, 32 13years) . All individuals underwent volumetric (3D) T1 weighted images with 1 mm isotropic voxels in a 3T scanner (PHILIPS) using a spoiled gradient echo sequence. We used SPM8/DARTEL (www.fil.ion.ucl.ac.uk) for VBM analysis, searching for differences in GM concentration; results were displayed with p uncorrected and T-statistics >3 as minimum threshold. We used Freesurfer software (www.surfer.nmr.mgh.harvard.edu)for cortical reconstruction and statistical analysis . Images initially underwent motion correction, removal of non-brain tissue, automated Talairach transformation, intensity normalization, tessellation of the gray matter white matter boundary, automated topology correction, and surface deformation. After that, imaging underwent surface inflation, registration to a spherical atlas, parcellation of the cerebral cortex, and creation of a variety of surface based data with maps of curvature and sulcal depth. This method uses both intensity and continuity information from the entire three dimensional MRI volume in segmentation and deformation procedures to produce representations of cortical thickness, calculated as the closest distance from the gray/white boundary to the gray/CSF boundary at each vertex on the tessellated surface. T-tests with FDR of 5% were performed searching for differences in cortical thickness, hemispheric volume and sulcal depth; results were displayed with significance of p<0.05. Results: Patients and controls were balanced for both gender (p=1) and age (p=0.74). VBM revealed few areas with significantly reduced GM concentration in ipsilateral parietal and frontal lobes, and more extensive areas in cerebellum (bilaterally) (Figure1). Surface-based thickness anaylsis revealed areas of abnormalities in left motor area and some other scattered areas. Sulci analysis revealed few areas with reduction in both hemispheres. Reduction in hemispheric volume of patients was identified in both sides, more extensive in left hemisphere (Figure2). Conclusions: Our preliminary results with few patients with left FCD revealed subtle bilateral GM abnormalities, extending beyond the abnormality seen on visual MRI analysis. VBM showed reduced GM concentration mainly in cerebellum and Freesurfer cortical analysis was superior in detecting cortical abnormalities, mainly in motor areas. These abnormalities may be related to seizure propagation and surgical outcome.