White matter alterations in MR-negative temporal and frontal lobe epilepsy using fixel-based analysis

Area of Science:

• Neuroimaging
• Neuropathology
• Epilepsy Research

Background:

• Pharmacoresistant epilepsy patients often have no visible lesions on standard MRI (MR-negative).
• Understanding neuropathology in MR-negative epilepsy is crucial for diagnosis and treatment.
• Previous diffusion tensor imaging analysis has limitations with crossing fibers.

Purpose of the Study:

• To investigate white matter alterations in MR-negative frontal lobe epilepsy (FLE) and temporal lobe epilepsy (TLE) patients.
• To extend knowledge of group-specific neuropathology in MR-negative epilepsy using advanced imaging analysis.
• To compare white matter integrity between healthy controls and epilepsy patient groups.

Main Methods:

• Utilized fixel-based analysis (FBA), an advanced diffusion imaging technique overcoming limitations of traditional methods.
• Compared fixel parameters between 100 healthy controls and 9 FLE patients and 13 TLE patients.
• Focused on MR-negative patients where lesions were confirmed by resective surgery.

Main Results:

• FLE patients showed a significant decrease in the cross-section area of fixels within the superior longitudinal fasciculus.
• TLE patients exhibited widespread atrophy in limbic, thalamic, and cortico-striatal connections, as well as temporal lobe-connected tracts.
• Alterations extended to extratemporal connections, including brainstem, commissural fibers, and parts of the superior longitudinal fasciculus.

Conclusions:

• This is the first study to apply FBA to MR-negative FLE and TLE patients.
• FBA revealed novel, common, tract-specific white matter alterations at the group level in these patient populations.
• Findings contribute to a deeper understanding of the neuropathology underlying MR-negative epilepsy.