Effective connectivity in temporal lobe epilepsy with hippocampal sclerosis

We hypothesized that temporal lobe epilepsy (TLE) patients with and without hippocampal sclerosis (HS) showed differences in their limbic networks. This study aimed to evaluate the role of the thalamus in TLE patients with HS.

Twenty-nine TLE patients with HS and 30 controls were enrolled in this study. In addition, we included eight TLE patients without HS as a disease control group. Using whole-brain T1-weighted MRIs, we analyzed the volumes of the limbic structures, including the hippocampus, thalamus, and total cortex, with FreeSurfer 5.1. We also investigated the effective connectivity among these structures using SPSS Amos 21 based on these volumetric measures. Moreover, we quantified correlations between epilepsy duration and the volumes of these structures.

There was a statistically significant effective connectivity from the hippocampus to the thalamus in TLE patients with HS. Moreover, the volumes of the left and right thalamus were negatively correlated with epilepsy duration (r=-.42, P=.0315 and r=-.52, P=.0062, respectively). However, neither TLE patients without HS nor normal controls had a significant effective connectivity from the hippocampus to the thalamus.

The limbic networks of TLE patients with and without HS could be different, and the thalamus might play a critical role in TLE patients with HS.