Abstracts

A previous study demonstrated significant clinicopathological, structural and functional imaging differences between TLE associated with hippocampal sclerosis (HS+ve) and MRI-negative PET-positive temporal lobe epilepsy (HS-ve). The purpose of this study is to compare hippocampal surface structure, using large deformation high dimensional mapping (HDM-LD), of the HS-ve and HS+ve groups., This study included 30 HS-ve subjects matched with 30 HS+ve subjects from the previously reported epilepsy patient cohort. To control for normal right-left asymmetries of hippocampal surface structure, subjects were regrouped based on laterality of onset of epileptic seizures and presence of HS. The gender ratio, age, duration of epilepsy, and pre-operative seizure frequency scores classified according to a 12[ndash]point seizure frequency score were calculated for each of the four groups. Each group underwent evaluation with HDM-LD to measure hippocampal surface differences relative to a control group. Final HDM-LD surface maps of the right and left TLE groups were compared to define differences in subregional hippocampal involvement within the groups., There were no significant differences in comparisons of the left TLE (left HS-ve compared to HS+ve) or right TLE (right HS-ve compared to HS+ve) groups with respect to age, duration of epilepsy, or seizure severity scores. HDM-LD maps showed accentuated surface changes over the lateral hippocampal surface, in the region of Sommer sector, in the HS+ve hippocampi. However, HS-ve hippocampi showed maximal surface changes in a different pattern, and did not involve the region of Sommer sector., We conclude that differences in segmental volume loss between the HS-ve and HS+ve groups are suggestive that the underlying pathophysiology of hippocampal changes in the two groups is different, and not related to chronic seizure duration or severity.,