Abstracts

Voxel-based morphometry (VBM) can be used to compare regional differences in gray or white brain matter volume between groups. Applied as an automated method, the technique can elucidate differences that might not otherwise be apparent on normal appearing MR images. Previously, this technique has been used to characterize abnormalities in gray matter (GM) in subjects with temporal lobe epilepsy (TLE). However, few investigations have investigated white matter (WM) in TLE using VBM. This study seeks to use VBM to characterize both GM and WM abnormalities in subjects with lateralized TLE. 25 subjects with unilateral TLE (13 left, 12 right) were selected using the following criteria: 1) age 14 to 60 years; 2) ictal EEG confirmation of unilateral temporal lobe seizure onset; 3) absence of MRI abnormalities other than atrophy; 4) no other neurological disorder. Healthy controls were friends or family members of the TLE subjects. The SPM2 software (Wellcome Department of Cognitive Neurology, University College, London) was used for VBM analysis. VBM was performed with methodology similar to Good et al. (Neuroimage 14, 2001). This includes study-specific-template creation, 12-mm FWHM image smoothing, and the volume-preserving modulation step. Results were corrected for multiple comparisons at FDR [lt] 0.05. [italic]Gray Matter:[/italic] Volume reduction was present in the ipsilateral hippocampus of both left and right TLE groups. Significant volume decreases were also detected in the ipsilateral thalamus of both left and right TLE groups. [italic]White Matter:[/italic] A strong WM volume decrease was present in the temporal pole ipsilateral to seizure onset. Volume loss was detected extratemporally in bilateral prefrontal white matter of the left TLE group. Additionally, voxels located in the corpus collosum of both left and right TLE groups and the fornix of the right TLE group indicated significant volume decrease. Previous region-of-interest based quantitative MRI studies, as well as prior VBM studies using slightly different techniques (concentration changes rather than volume changes as in this study), have reported abnormalities in the hippocampus and thalamus. In the context of these gray matter changes, this investigation detected significant abnormalities in white matter that preferentially affected the ipislateral temporal pole, with secondary effects in the frontal lobes, corpus callosum and fornix. The relationship between these VBM-defined volumetric changes and clinical seizure features such as onset, duration, and seizure frequency/severity will be explored further using VBM. (Supported by NIH NS 2RO1-37738 and MO1 RR03186 (GCRC))