Volumetric and shape analysis of hippocampal subfields in unilateral mesial temporal lobe epilepsy with hippocampal atrophy

Objective: The hippocampus consists of several functionally and histologically different subfields that are known to be differentially affected in mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE). Using automated MRI analyses, we aimed to investigate atrophy patterns of hippocampal subfields and their relationships with clinical characteristics in a homogenous group of unilateral MTLE. Methods: Twenty-four left MTLE patients, 23 right MTLE patients, and 41 control subjects were scanned on a 3. T MR scanner. Automated volumetry and shape analysis were used to assess volume and shape changes of hippocampal subfields in MTLE patients relative to controls. Within-group correlations were performed between subfield volumes and clinical variables in patients. Results: Compared to controls, left and right MTLE patients exhibited significant volume reductions in ipsilateral whole hippocampus and subfields including CA1, CA2-3, CA4-DG, presubiculum, and subiculum (corrected p<. 0.05). Regional inward shape deformation mainly localized to ipsilateral CA1 and adjacent subiculum was found in left and right MTLE patients relative to controls (corrected p<. 0.05). Longer disease duration was related to smaller volumes of left CA1, presubiculum, and subiculum in left MTLE, and right CA1 in right MTLE. Conclusion: We found overall volume reductions in ipsilateral hippocampal subfields in patients with unilateral MTLE, in accordance with known pathologic findings. Our findings of regional atrophy in ipsilateral CA1 and subiculum on shape analysis and an inverse relationship between disease duration and ipsilateral CA1 volume implicate an important role of CA1 and subiculum in the pathogenesis underlying MTLE.