'MRI-negative PET-positive' temporal lobe epilepsy (TLE) and mesial TLE differ with quantitative MRI and PET: a case...

Area of Science:

• Neurology
• Radiology
• Epilepsy Research

Background:

• A significant subset of temporal lobe epilepsy (TLE) is characterized as 'MRI negative PET positive'.
• These patients exhibit clinicopathological and qualitative imaging distinctions from mesial temporal lobe epilepsy.
• This study investigates quantitative imaging differences between TLE with hippocampal sclerosis (HS+ve) and non-lesional TLE without hippocampal sclerosis (HS-ve).

Purpose of the Study:

• To quantitatively compare MRI and FDG-PET measures in HS+ve TLE versus HS-ve TLE.
• To identify structural and functional imaging biomarkers differentiating these TLE subtypes.

Main Methods:

• Comparison of 30 HS-ve patients with 30 age- and sex-matched HS+ve patients, all with well-lateralized EEG.
• Performance of cerebral, cortical lobar, and hippocampal volumetric analyses.
• Execution of co-registered FDG-PET metabolic analyses.

Main Results:

• No significant differences in whole brain, cerebral, or cerebral cortical volumes were observed between groups.
• Both groups exhibited marginally smaller ipsilateral cerebral volumes relative to the epileptogenic side.
• HS+ve patients displayed greater relative volume deficits in the insular and temporal lobes, and more marked hippocampal hypometabolism.
• Both groups showed significant ipsilateral cerebral cortical hypometabolism, which was more pronounced in HS-ve patients across most lobes.

Conclusions:

• HS+ve patients demonstrated more pronounced hippocampal atrophy and greater ipsilateral hippocampal hypometabolism.
• Marginal ipsilateral cerebral and cerebrocortical atrophy was noted in HS+ve patients.
• Similar patterns of ipsilateral cerebral cortical hypometabolism were observed in both groups, confirming distinct structural and functional characteristics between HS+ve and HS-ve TLE.