Patterns of hypometabolism in frontal lobe epilepsy originating in different frontal regions

Objectives: Analysis of FDG-PET imaging commonly shows that hypometabolism extends into extra-epileptogenic zones (extra-EZ). This study investigates the distribution patterns of hypometabolism in frontal lobe epilepsy (FLE) originating in different frontal regions. Methods: Sixty-four patients with FLE were grouped by EZ localization according to Brodmann areas (BAs): Group 1 (the frontal motor and premotor area), BAs 4, 6, and 8; Group 2 (the inferior frontal gyrus and opercular area), BAs 44, 45, and 47; Group 3 (the dorsal prefrontal area), BAs 9, 10, 11, and 46; and Group 4 (the medial frontal and anterior cingulate gyrus), BAs 32 and 24. Regions of extra-EZ hypometabolism were statistically analyzed between FLE groups and healthy controls. Correlation analysis was performed to identify relationships between the intensity of hypometabolism and clinical characteristics. Results: Significant hypometabolism in the ipsilateral (Groups 1 and 4) or bilateral (Groups 2 and 3) anterior insulae was found. Groups 1 and 4 presented with limited distribution of extra-EZ hypometabolism, whereas Groups 2 and 3 showed widely distributed extra-EZ hypometabolism in the rectus gyrus, cingulate gyrus, and other regions. Additionally, the intensity of hypometabolism was correlated with epilepsy duration in Groups 2 and 3. Conclusions: All FLE groups showed hypometabolism in the anterior insula. In addition, distinct patterns of extra-EZ hypometabolism were identified for each FLE group. This quantitative FDG-PET analysis expanded our understanding of the topography of epileptic networks and can guide EZ localization in the future.