Disentangling hippocampal shape anomalies in epilepsy

Area of Science:

• Neuroimaging
• Epilepsy Research
• Human Anatomy

Background:

• Drug-resistant temporal lobe epilepsy (TLE) and malformations of cortical development (MCD) are linked to complex hippocampal morphology.
• The specific contributions of hippocampal volume and position to shape anomalies in TLE and MCD remain uncharacterized.

Purpose of the Study:

• To develop and apply a surface-based framework for analyzing hippocampal shape alterations in TLE and MCD.
• To quantify volume changes using Jacobian determinants and assess positional/curvature changes via a medial axis model.

Main Methods:

• Utilized T1-weighted 3D volumetric MRI data from 88 TLE patients, 78 MCD patients (including focal cortical dysplasia, heterotopia, polymicrogyria), and 46 controls.
• Employed a surface-based analysis framework to measure Jacobian determinants for volume and a medial axis model for curvature and position.

Main Results:

• TLE showed significant ipsilateral hippocampal atrophy, primarily in the CA1 subfield.
• MCD exhibited bilateral CA1 atrophy (heterotopia, focal cortical dysplasia) and left dentate hypertrophy (all MCD subtypes).
• TLE displayed posterior hippocampal medial bending, while MCD showed a supero-medial shift of the hippocampal body.

Conclusions:

• Hippocampal shape anomalies in TLE and MCD arise from combined volume and positional changes.
• The distinct patterns of these changes suggest divergent pathogenic mechanisms underlying TLE and MCD.