Imaging insights into temporal lobe epilepsy: an AES-SDM meta-analysis and retrospective cohort study

To investigate convergent patterns of gray matter volume (GMV) alterations in temporal lobe epilepsy (TLE) and to characterize distinct gray matter atrophy patterns across subtypes of TLE.

A coordinate-based meta-analysis was performed using anisotropic effect size-based signed differential mapping (AES-SDM). In addition, a complementary single-center observational cross-sectional VBM cohort including patients with hippocampal sclerosis (HS) and MRI-negative TLE (TLE-no) was analyzed to explore subgroup-related GMV alterations compared with healthy controls(HCs).

The meta-analysis revealed the most consistent GMV reductions in the ipsilateral hippocampus and parahippocampal, ipsilateral inferior temporal gyrus, ipsilateral fusiform gyrus, ipsilateral insula, ipsilateral lenticular nucleus, ipsilateral cerebellum, and bilateral thalamus in TLE, compared with HCs. GMV increases of the unilateral amygdala and parahippocampal gyrus were observed in TLE without HS. In the observational cross-sectional analysis, patients with unilateral HS showed reduced GMV in the ipsilateral hippocampus, parahippocampal gyrus, fusiform gyrus, temporal gyrus, temporal pole, and thalamus, compared with HCs. Compared with the left HS, the right-sided HS group exhibited GMV atrophy in the right amygdala and cerebellum, alongside longer disease duration. In the Left-sided TLE-no patients, GMV increase was observed in the ipsilateral amygdala and parahippocampal gyrus in TLE-no.

The meta-analysis identified multiple morphometric alterations in extrahippocampal regions in TLE and described GMV alteration patterns across different TLE subgroups. Complementary observational cross-sectional VBM cohort showed partially overlapping spatial patterns. GMV increases in the unilateral amygdala and parahippocampal gyrus were observed in MRI-negative TLE and should be interpreted cautiously, given the heterogeneity of this subgroup.