Relationship between PET metabolism and SEEG epileptogenicity in focal lesional epilepsy

Purpose: This study aims to evaluate the performance of 18 F-FDG PET for distinguishing the epileptogenic zone (EZ) from propagation and non-involved zones at brain area level, as defined using stereo-EEG, in patients with pharmacoresistant epilepsy due to malformations of cortical development (MCD). Additionally, we seek to determine the relationship between 18 F-FDG-PET data and post-surgical seizure outcome. Methods: Thirty-eight patients with MCD were explored with 18 F-FDG PET and stereo-EEG. We compared PET metabolism of each patient to a control-population of healthy subjects. Based on MRI and SEEG, we separated 4 distinct zones at individual level: lesional, epileptogenic non-lesional, propagation, and non-involved. Then, we analysed: 1) difference of PET metabolism within these four distinct zones; 2) performance of PET in defining the EZ within the SEEG-sampled areas; 3) relation between extension of PET hypometabolism and post-surgical seizure outcome. Results: We found: 1) a gradient of PET hypometabolism from non-involved to propagation, then to epileptogenic and lesional zones (p<0.001); 2) good performance of PET in defining the EZ (AUC of ROC curve = 0.82); 3) poorer post-surgical prognosis associated with PET hypometabolism extension beyond SEEG sampling (p=0.024). Conclusion: 18 F-FDG-PET has good accuracy in determining EZ in patients with MCD even if the hypometabolism is not limited to the EZ. Furthermore, hypometabolic extension is unfavourably associated with post-surgical prognosis.