Abstracts

Rationale: MRI-positive TLE (significant hippocampal volume asymmetry) and MRI-negative TLE (symmetrical hippocampal volumes) differ in underlying pathophysiology of disease. We compared total gray cortical and white matter volumes in patients with MRI-positive and MRI-negative TLE to assess for associated global structural brain changes in each group.Methods: A consecutive series of subjects with confirmed TLE underwent volumetric T1-weighted MPRAGE MRI on the same MRI scanner (3T Trio Siemens TrioTim). Images were processed using high-dimensional mapping with large deformation (HDM-LD) to define hippocampal volumes and 3-dimensional hippocampal surfaces. Free Surfer segmentation was applied to all MRI studies to determine total cortical gray and white matter volumes. The MRI-positive group was defined as having a greater than 15% hippocampal volume asymmetry. Total gray and white matter volumes between the MRI-positive and MRI-negative groups were compared using a 2-tailed t test.Results: 12 subjects were TLE-positive and 14 patients were TLE-negative. Average total gray and white matter volumes was 902.0 (+/- 84.7) cm3 and 920.6 (+/- 83.0) cm3 for TLE-positive group and TLE-negative group respectively, p=0.56. Duration of epilepsy was 28 years and 23 years for the TLE-positive group and TLE-negative group respectively, p=0.38Conclusions: While MRI-positive TLE subjects show more pronounced hippocampal volume changes in comparison to MRI-negative TLE subjects, global white and cortical gray matter volume changes do not differ between the groups. Further planned comparisons with control subjects and regional cortical thickness measurements offers the opportunity to further investigate global structural brain changes in MRI-positive and MRI-negative TLE.