Local brain volume reductions in patients with non-lesional epilepsy on 7T MRI

In patients with non-lesional epilepsy, MR imaging detects no structural or functional abnormalities. The aim of this study was to determine whether subtle local reductions or increases in brain volume, undetectable to the human eye, can indicate an epileptic focus directly or indirectly. To address this, we performed brain volumetry using 7T MRI.

We evaluated 7T MRI in patients with non-lesional epilepsy as part of a retrospective study and a healthy control cohort from another prospective study. FastSurfer segmentations were performed using T1 MPRAGE. Additionally, we also performed volumetry of the hippocampal subfields, the thalamic nuclei and the brainstem. We created a control group matched for age and gender distribution.

7T segmentation as described above was possible in 14 patients with epilepsy and 27 participants of a control cohort. We detected a significant volume loss in the ipsilateral central lateral nucleus of thalamus, as well as a significant increase in the presubiculum body and the ipsilateral and contralateral entorhinal and medial orbitofrontal cortices.

High-resolution 7T MRI-based volumetric analysis in patients with non-lesional epilepsy revealed significant atrophy in brain regions commonly implicated in epileptogenesis. These structures exhibited strong sensitivity and specificity, highlighting the potential of volumetry as a diagnostic tool in the absence of visible lesions. Validation in larger, independent cohorts is required to confirm these findings and assess clinical applicability.