Abstracts

Rationale: Hippocampal sclerosis (HS) is the most common pathology finding for drug resistant temporal lobe epilepsy (TLE) and is characterized by neuronal loss and gliotic Cornu Ammonis. The hippocampal dentate gyrus and granule cell layer (GCL) are often overlooked by pathologists. Nearly 20% of the surgical specimens obtained from drug-resistant TLE surgery patients contain “normal” populations of neurons, termed no-HS, yet still benefit from their surgical resection. This observation possibly points to a neuropathological explanation for the epileptogenic focus present in the resected tissue that is not able to be detected through standard diagnostic practices. The overall goals of this project are to add to the neuropathological understanding of drug resistant TLE, and to elucidate the structural changes of HS and no-HS, with a focus on the GCL.

Methods: In this study, 21 TLE surgical resection cases were examined, including 14 HS and 7 no-HS cases, to investigate morphometry of the GCL. Information on histopathological diagnosis and post-operative outcome were included in a clinicopathological correlation database. The digital image analysis software QuPath was used to perform cell detection analysis on the GCL. Measures including Delaunay mean, cell density, nuclear size, and circularity were analyzed.

Results: HS patients show a significant increase in granule cell spacing and decrease in granule cell density within the granule cell layer compared to no-HS patients. Regardless of the histological diagnosis, patients achieved seizure freedom post-operatively demonstrated an increase in granule cell spacing and decrease in granule cell density in comparison to those who did not achieve seizure freedom post-operatively.

Conclusions: HS and no-HS diagnosis groups have disease- and post-operative outcome dependent morphometry differences. The post-operative outcome dependent morphometry observed in HS and no-HS patients presents the potential of an additional method to evaluate post-operative prognosis for TLE surgical-resection patients.

Funding: Please list any funding that was received in support of this abstract.: Epilepsy Research Program of the Ontario Brain Institute (Qi Zhang), Lawson's Internal Research Fund Studentship (Carolyn Twible).