Abstracts

Rationale: Past examinations of temporal lobectomy specimens from patients with chronic temporal lobe epilepsy (TLE) has revealed the presence of amyloid plaques in a subset of patients. Amyloid deposition might have a role in the pathophysiology of chronic TLE, and newer imaging modalities such as florbetapir PET/CT afford the opportunity to reassess amyloid deposition throughout the brain.Methods: Adult subjects with chronic TLE (n=8) underwent florbetapir PET/CT and MRI brain imaging. Volumetric analysis of individual subject's MRI data was performed using FreeSurfer segmentation software to define anatomical regions of interest and co-registered with the subject's PET data to calculate regional PET signal intensity values (standard uptake value ratios, SUVRs). A control cohort (n=36) from our institution's Alzheimer's disease research center with the same imaging had their data processed in the same manner. Mean SUVRs from the cortex and hippocampus were compared between the groups. Clinical data including EEG and MRI were used to lateralize the epileptogenic temporal lobe. Differences were compared using 2-sided t-tests.Results: Hippocampal SUVRs were statistically higher than cortical SUVRs in the TLE group; however, this was also seen in the control group. Within subject hippocampal-to-cortical signal ratios compared between the TLE and control groups failed to demonstrate a statistical difference. Within the TLE group, there was no significant difference between left and right or ipsilateral (side of greater hippocampal structural abnormality) and contralateral hippocampal SUVRs, despite the fact that most subjects had strongly unilateral epilepsy (4 right temporal, 3 left temporal, and 1 bitemporal).Conclusions: Florbetapir PET/CT imaging revealed that there was stronger amyloid signaling in the hippocampus compared to the cortex for both TLE and control subjects, but we failed to demonstrate that these relative regional differences within individual subjects were statistically different between the groups. Interestingly, despite predominantly unilateral epilepsy, there was no significant difference between hippocampal SUVRs between the sides (left versus right or ipsilateral versus contralateral to side of greater hippocampal structural abnormality). Further work to investigate other potentially significant regional differences within and between groups is ongoing.