Abstracts

Rationale: Thalamo-cortical network is a key structure in the mechanism of seizures generation in idiopathic generalized epilepsies (IGE). Neuroimaging investigations disclosed subtle abnormalities located mainly in the frontal lobe. Patients with IGE also have cognitive abnormalities specially related with the functions of the frontal lobe. The objective of this study was to investigate the correlations between functional and structural findings in patients with IGE using neuropsychological evaluation and high resolution MRI. Methods: Ten patients (5 women, mean age 31 12 years) with IGE diagnosis were submitted to 3 Tesla MRI (Siemens, Verio). Volumetric (3D) T1 sequence was used for structural evaluation of the cortical surface. Cortical reconstruction and statistical analysis was performed with Freesurfer image analysis suite (http://surfer.nmr.mgh.harvard.edu/). For the analysis, images were previously processed which included quality improvement, automated transformation into Talairach space, tessellation of the gray matter / white matter boundary, automated topology correction, and surface deformation. After that, data processing included surface inflation, registration to a spherical atlas which utilized individual cortical folding patterns to match cortical geometry across subjects, parcellation of the cerebral cortex into units based on gyral and sulcal structure, and creation of a variety of surface based data including maps of cortical thickness. The software uses both intensity and continuity information from the entire three dimensional MR volumes 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. Memory and attention assessment were performed by a trained neuropsychologist using standardized sequence and tests (Word Recognition List, Color Trails Test and Rey Auditory Verbal Learning Test - RAVLT). By using GLM, correlation between cortical thickness and neuropsychological profile was investigated. Age and scholarity entered as nuisance factors. Surfaces were smoothed with a 10mm FWHM filter. Level of significance selected was p < 0.05.Results: Attention had a positive correlation with the cortical thickness with main clusters located specially in the frontal lobes. The most significant areas where located in the rostral middle frontal area (value 3.70, size 425 mm2, Tal: x = -23 y = 57 z= -10, p < 0.001) of the left hemisphere and superior frontal area in the right hemisphere (value 4.35, size 336 mm2, Tal: x = 9, y = 44, z = 30, p < 0.0001). Figure 1 depicts these findings. Verbal and visuo-spatial memories did not correlate with cortical thickness.Conclusions: This preliminary investigation showed that patients with IGE have a positive correlation between the cortical thickness of the frontal lobe and attention performance. These findings stress the participation of the frontal cortex in IGE pathogenesis.