Abstracts

Rationale: Prior studies have demonstrated a relationship between intelligence and regional variations in cerebral tissue,particularly in the rapidly developing brains of normal children and adolescents.Yet, there is no information regarding neuroanatomical correlates of general intelligence in children with epilepsy compared to healthy controls.Here we demonstrate discrepancies in the neurodevelopmental relationship between full-scale intelligence quotient(FSIQ) and cortical morphometry in developing brains of children with epilepsy. Methods: To identify possible localized relationships,we examined FSIQ associations with cortical morphometry—gray matter(GM) tissue thickness—at high spatial resolution across the cortex in 77 healthy controls(age 6 to 18) and 65 pediatric epilepsy patients with complex partial seizures(CPS)(age 6 to 16).High-resolution 3D MR images were obtained on 1.5Tesla scanners located in two different sites.After the 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 GM tissue were extracted.Cortical thickness at each point in the cortical GM mantle is defined as the sum of the distances from this point to the GM/WM and GM/CSF tissue boundaries following a flow field which guarantees a one-to-one,symmetric and continuous correspondence between the two tissue boundaries.A surface-based spatial normalization technique was used to match anatomically homologous cortical features across subjects before performing cross-subject comparison.FSIQ was considered the parameter of interest in the analysis addressing the correlation of IQ and GM thickness.Age,gender and scanner/acquisition differences(i.e.,data from multiple sites) were considered as covariates in order to factor out their substantial influence on the brain morphology.To explorer the developmental effects,dataset was divided into early childhood(6—8.5 years), late childhood(8.5—11.5 years), adolescence(11.5—18 years). Results: Statistical maps in the figure show significant correlations between FSIQ and GM thickness for the three age groups after removing the partial effects of sex,age and site.For healthy controls,positive correlation between GM thickness and FSIQ in early childhood is followed by a negative correlation especially in the frontal and temporal regions in late childhood and early adolescence.This is congruent with GM thickening and pruning phases observed in healthy cortical development.In CPS patients,there is a marked developmental shift from a predominantly negative correlation between intelligence and cortical thickness in early childhood to a positive correlation in late childhood and adolescence. Conclusions: Our cross-sectional findings suggest a disruption in the dynamic neuroanatomical expression of intelligence(a delayed maturation of structure-function relationships) in pediatric CPS patients.Our future work will focus on the trajectory of change in the cerebral morphology of these children and how they relate to the level of intelligence.