Abstracts

Rationale: Post- and pre-central cortical thickness (CT) peak around age 7 and 10, respectively, followed by thinning that accelerates in adolescence[1]. Earlier, we demonstrated a positive CT and sulcal depth (SD) association in these regions in focal epilepsy (FE) but not in healthy control subjects[2]. Given the cortical volumetric, CT, and SD abnormalities[3-6], and prevalent psychiatric diagnoses (PsyDg) in pediatric epilepsy[7], we examined if the pre- and post-central CT-SD association is different in children with FE who have a PsyDg compared to those with no PsyDg.Methods: High-resolution 3D MR images in a 1.5 Tesla scanner were obtained on 42 FE (6.1- 16.2 years). After removal of non-brain tissue from MR images, image voxels were classified into different tissue types. Cortical surface representations at the geometric center of the 3D gray matter (GM) tissue were extracted. CT at each point in the cortical GM mantle was defined as the sum of the distances from this point to the GM/white matter and GM/CSF tissue boundaries. A surface-based spatial normalization technique was used to match anatomically homologous cortical features across subjects before performing cross-subject comparison. PsyDg were made based on structured psychiatric interviews administered to each subject. Parents provided information on seizure variables. We examined whether presence of PsyDg was related to the CT-SD association using general linear models, with regional SD as the dependent variable, and the same regional CT, presence of PsyDg and the interaction of CT with PsyDg as the independent variables. Another set of similar linear models used seizure variables (age of onset, seizure frequency) and the interaction of CT with seizure variables as the independent variables.Results: 18 of the 42 (43.9%) children in the FE group had a PsyDg. For pre-central SD, there was a significant interaction effect of CTxPsyDg (F(1,36)=4.9, p=.03). Post hoc testing demonstrated a positive pre-central CT-SD slope in FE PsyDg+ (slope=0.5, t=3.6, p=.0009) but not in PsyDg- (slope= 0.004, t=.03, p=.9) (Figure 1). For post-central SD, a significant interaction effect of CTxPsyDg (F(1,36)=7.2, p=.01) demonstrated that the CT-SD significant association was present in FE PsyDg+ (CT-SD slope=.9, t=3.8, p=.0006) but not in the PsyDg- group (slope=.05, t=.3, p=.8) (Figure 2). Pre- and post-central CT-SD associations were unrelated to age of epilepsy onset and seizure frequency.Conclusions: These findings suggest that positive pre- and post-central CT-SD associations might be a biomarker of the psychiatric comorbidity of pediatric FE.