Hippocampal Deformation‐based Shape Analysis in Epilepsy and Unilateral Mesial Temporal Sclerosis

Purpose: To assess shape changes in patients with mesial temporal sclerosis (MTS) and temporal lobe epilepsy (TLE), by using deformation‐based hippocampal shape analysis. Methods: We retrospectively reviewed magnetic resonance imaging (MRI) studies in 30 subjects with unilateral MTS (15 right‐sided MTS, 15 left‐sided MTS) and TLE. We defined the “average” hippocampus in the right‐ and left‐MTS groups by generating a mean transformation for the 15 deformation images in each group. Further to quantify the difference between the hippocampi, we coregistered the mean transformation of the involved hippocampus (with MTS) to the contralateral hippocampus, considering the left‐ and right‐MTS groups independently. We generated a color “flame” scale showing degrees of outward and inward deviation of the coregistered hippocampi. Results: Both the right‐ and left‐MTS groups showed similar shape changes, with maximal inward deformation in the medial and lateral hippocampal head and the hippocampal tail. However, more extensive involvement was seen in the lateral hippocampal body in the right‐MTS group as compared with the left. Conclusions: Deformation‐based hippocampal shape analysis shows specific regions of hippocampal surface anatomy that are most affected in MTS. This technique may aid in detection of clinically significant anatomic abnormalities of the hippocampus in patients with epilepsy.