Regional hippocampal diffusion abnormalities associated with subfield-specific pathology in temporal lobe epilepsy

Area of Science:

• Neuroimaging
• Epilepsy Research
• Medical Diagnostics

Background:

• Hippocampal sclerosis (HS) is key in medically refractory temporal lobe epilepsy (TLE).
• Current MRI struggles to characterize subfield pathology for precise surgical outcome prediction.
• Diffusion tensor imaging (DTI) offers microstructural insights but is limited by low resolution.

Purpose of the Study:

• To evaluate high-resolution DTI for characterizing hippocampal pathology in TLE.
• To correlate DTI findings with histological changes and clinical outcomes.
• To assess DTI's potential for improving surgical planning and seizure-free outcome prediction in TLE patients.

Main Methods:

• Acquired high-resolution DTI, T1, and quantitative T2 of the hippocampus in 18 TLE patients and 19 controls.
• Qualitatively assessed diffusion images for internal architecture; compared whole-hippocampus diffusion, volume, and T2 across groups.
• Examined regional diffusion abnormalities and compared them to postsurgical histology in four patients.

Main Results:

• High-resolution DTI visualized internal hippocampal architecture, identifying HS with 86% specificity and 93% sensitivity.
• Mean diffusivity (MD) elevations were regionally heterogeneous in TLE patients, correlating with histological findings.
• TLE patients showed higher whole-hippocampus MD and T2, and lower fractional anisotropy (FA) and volumes versus controls; left hippocampus MD correlated with verbal memory.

Conclusions:

• High-resolution DTI reveals internal architecture and focal diffusion abnormalities in TLE.
• This technique shows promise for clinical utility in TLE diagnosis and surgical planning.
• Advanced diffusion imaging may significantly improve prediction of seizure-free outcomes for individual TLE patients.