Association between local gray matter volume differences and stereo-electroencephalography-defined epileptogenicity.

Objective: The yield of voxel-based gray matter volume (GMV) quantification to identify the epileptogenic zone (EZ) remained moderate, which may be due to the choice of "ground truth." We explored whether GMV differences are associated with stereo-electroencephalography (SEEG)-defined epileptogenicity as potential EZ imaging biomarkers.

Methods: We included SEEG patients along with age- and sex-matched non-epilepsy controls. We performed a non-parametric voxel-based permutation inference between each SEEG patient's non-contrast 3T T1-weighted magnetic resonance imaging (MRI) scan and controls, resulting in pseudo-t-test maps reflecting GMV differences. We classified SEEG contacts based on their involvement in (i) the EZ, defined as contacts designated for radiofrequency thermocoagulation, and (ii) active irritative zones, defined as contacts generating the top 10% of spikes, fast ripples, and cross-rates of HFO*spikes for each patient. We then performed mixed-effects logistic regressions and performance analysis.

Results: We included 50 patients (median age 33.0 years, female 52.0%, MRI-negative 76.0%) and 51 controls (median age 37.0 years, female 56.9%). EZ: In general, increased GMV was associated with EZ contacts across the whole cohort (odds ratio [OR] 1.21, 95% confidence interval [CI] 1.11-1.31, p < .001) and the MRI-positive group (OR 1.45, 95% CI 1.28-1.64, p < .001), but not in the MRI-negative group (p = .621). Reduced GMV was associated with EZ contacts in mesiotemporal regions (OR .53, 95% CI .33-.84, p = .035) but the opposite in neocortical areas (OR 1.32, 95% CI 1.21-1.44, p < .001). Within MRI-visible lesions, increased GMV was positively associated with EZ contacts (OR 1.50, 95% CI 1.19-1.89, p = .005). Active irritative zone: In the MRI-positive group, increased GMV was linked to neocortical contacts exhibiting the top 10% of spikes (p = .040) and fast ripples (p = .008), but not in MRI-negative cases.

Significance: Local GMV differences were positively associated with EZ contacts in the whole cohort and MRI-positive patients but not in MRI-negative patients, with positive associations in the neocortex and a negative one in the mesiotemporal structures. Within MRI-visible lesions, increased GMV was associated with EZ contacts.