Widespread, depth-dependent cortical microstructure alterations in pediatric focal epilepsy

Area of Science:

• Neuroimaging
• Epilepsy Research
• Pediatric Neurology

Background:

• Focal epilepsy may involve tissue abnormalities extending beyond the primary seizure focus.
• The origins of these broader changes (disease process vs. treatment effects) and their emergence timing, particularly in childhood, remain unclear.
• Quantitative magnetic resonance imaging (MRI) offers a sensitive method to detect subtle microstructural tissue changes.

Purpose of the Study:

• To identify common spatial patterns of cortical microstructural changes in children with drug-resistant focal epilepsy.
• To investigate if these observed changes correlate with disease severity.
• To explore the potential of quantitative MRI measures to detect an epilepsy endophenotype.

Main Methods:

• Quantitative T1 and T2 relaxometry (qT1, qT2) was used to assess cortical microstructure in 43 children with focal epilepsy and 46 controls.
• Depth-dependent qT1 and qT2 values and their gradients across cortical depths were analyzed.
• A machine learning classifier was trained to differentiate between MRI-positive epilepsy patients, controls, and MRI-negative epilepsy patients using qT1/qT2 gradient maps.

Main Results:

• Increased depth-dependent qT1 and qT2 values were observed in widespread cortical areas in epilepsy patients, indicative of microstructural alterations (e.g., myelin changes, gliosis).
• These widespread changes did not correlate with disease severity, suggesting they might represent early neurobiological alterations.
• A classifier achieved 71.4% sensitivity and 89.4% specificity in identifying MRI-negative epilepsy patients based on MRI-positive patient and control data.

Conclusions:

• The findings suggest a potential imaging endophenotype for focal epilepsy.
• This endophenotype is detectable using quantitative MRI, even in the absence of radiologically apparent abnormalities.
• Quantitative MRI may offer a valuable tool for understanding the broader pathophysiology of focal epilepsy in children.