Voxel-based morphometric magnetic resonance imaging (MRI) postprocessing in MRI-negative epilepsies

Area of Science:

• Neuroimaging
• Epilepsy Surgery
• Quantitative MRI Analysis

Background:

• Presurgical workup for pharmacoresistant focal epilepsy (PFE) aims to identify lesions for surgical resection.
• Magnetic resonance imaging (MRI)-negative (MRI(-)) epilepsy presents a challenge in localizing the epileptogenic zone.
• Detecting subtle abnormalities can significantly alter patient evaluation and improve surgical outcomes.

Purpose of the Study:

• To evaluate the utility of a voxel-based MRI postprocessing technique, the morphometric analysis program (MAP), in detecting subtle abnormalities in MRI(-) PFE patients.
• To assess the impact of MAP-detected lesions on surgical outcomes.

Main Methods:

• Retrospective analysis of 150 MRI(-) epilepsy surgical candidates.
• MAP applied to T1-weighted MRI, comparing against a scanner-specific normal database.
• MAP results reviewed blinded to clinical data, with validation by surgical outcome and pathology.

Main Results:

• MAP identified abnormalities in 43% of patients with a sensitivity of 0.9 and specificity of 0.67.
• Complete resection of MAP-positive regions correlated with the best seizure outcomes (p < 0.001).
• MAP confirmed visually identified subtle findings and revealed focal cortical dysplasia in resected tissue.

Conclusions:

• MAP is a practical tool for guiding the search for subtle MRI abnormalities in PFE.
• MAP can confirm visually suspected lesions, providing a target for surgical exploration when concordant with clinical presentation.