Abstracts

Rationale: Identifying markers of temporal lobe epilepsy is important for determining laterality of areas amenable to surgical resection. The white matter of the parahippocampal gyrus is a major input pathway to the hippocampus. Multimodal sensory information is relayed from primary sensory and association cortices to the hippocampus via the direct and indirect pathways that underlie the parahippocampal white matter region. Although hippocampal sclerosis is the most common underlying pathology in drug resistant temporal lobe epilepsy, the surrounding white matter may be additionally affected. This study retrospectively assesses if parahippocampal white matter could be an additional marker of seizure onset laterality in patients with temporal lobe epilepsy. Methods: 13 individuals with unilateral left temporal lobe epilepsy, as determined by long term video-EEG monitoring, and left hippocampal atrophy were included in this study as well as 41 control subjects. T1 weighted 3-D SPGR pulse sequence MRI images were acquired in all participants. Hippocampal and parahippocampal white matter volumes were derived by manually tracing consecutive T1 coronal slices reformatted through the long axis of the hippocampus. Finally, statistical analyses were performed comparing right and left hippocampal and parahippocampal white matter volumes to controls. Results: As expected, the left hippocampus was significantly smaller than controls (p < 0.001). The left parahippocampal white matter volume was also significantly smaller than controls (p=0.005). Conclusions: This study shows that, in addition to hippocampal volume, white matter of the parahippocampal gyrus could be a potential marker to aid in lateralization of epileptogenic onset. Quantifying this area may be important in determining surgically amenable regions to reduce seizure frequency in those with temporal lobe epilepsy. Funding: None