P 58. Anatomically-based hippocampal subfield segmentation in epilepsy patients – validation with histopathological results

Abstract

Introduction. Hippocampal sclerosis (HS) is the most frequent MRI finding in patients with temporal lobe epilepsy (TLE). Hippocampal sclerosis and differential involvement of hippocampal subfields in different subtypes of HS are related to pharmacoresistance and the outcome of epilepsy surgery. The presurgical evaluation of hippocampal subfields is therefore of great clinical importance. The present study validates the results of an MRI based automated hippocampal subfield segmentation using histopathology. Material and Methods. We performed an automated hippocampal subfield segmentation on presurgical 3D T1-weighted MPRAGE MRI data of 25 patients with unilateral TLE using the version 6.0 segmentation algorithm of Freesurfer. The resulting volumes of subfields CA1, CA2/3, CA4 and the dentate gyrus were correlated with histopathological cell counts in these subregions. The MRI-based subfield analysis was also used to differentiate between no, mild or severe atrophy in each subfield to classify HS subtypes according to the classification of HS subtypes in the histopathological evaluation (Bluemcke et al., 2013). Results. We found a significant correlation between histopathological results in subregion CA2 and automated segmentation of subregion CA2/3 (p=0.004), between histopathological results in CA3 and automated segmentation of CA2/3 (p = 0.0004) as well as between histopathological results and automated segmentation of the dentate gyrus (p=0.0001). The histopathological finding of HS type 1 could correctly be classified in all cases on MRI and differentiated from other types of HS. Discussion. The present study shows significant correlations between the results of the automated segmentation of the hippocampus on presurgical MRI data and histopathological evaluation. As the differential involvement of different hippocampal subfields and the histopathological subtype of HS may be associated with clinical parameters and the outcome after epilepsy surgery, the automated segmentation is promising for prognostic purposes before epilepsy surgery. Blumcke I, Thom M, Aronica E, et al. International consensus classification of hippocampal sclerosis in temporal lobe epilepsy: A Task Force report from the ILAE Commission on Diagnostic Methods. Epilepsia. 2013;54(7):1315-1329.