Abstracts

Rationale: White matter differences have been found in adults, typically reduced fractional anisotropy (FA); however, results in children have been mixed. Previous studies, however, often include a patient population that has abnormal MRI or impaired neuropsychological functioning compared to the control population. We examine white matter difference in a subset of children with epilepsy who are well matched to controls across several variables. Methods: Forty participants (ages 7-17) included 22 children with localization related epilepsy (LRE) and 18 healthy volunteers (CON) who completed neuroimaging and neuropsychological procedures. Children with LRE had a left-hemisphere seizure focus, normal MRI, mean age of onset of 8.02 years (+ 3.3), mean duration of 3.5 years (range 3 months-13 years), and 50% were on one AED and other 50% were on 2-4 AEDS. Seizure frequency varied from daily to none in the past 12 months. Diffusion Tensor Imaging (DTI) data were acquired on a Siemens 3T Trio with 30 directions at b=1000s/mm2 and 5 b=0s/mm2, repeated twice for 70 brain volumes, 2.5 mm isotropic voxels, 55 slices at 2.5mm thickness, GRAPPA=2, and TE/TR = 86/6300ms. Diffusion weighted images went through a correction pipeline using TORTOISE, which registers the volumes of a DTI dataset to reduce the effects of motion, eddy current distortions and EPI distortions. Voxel-wise analysis was performed using Tract Based Spatial Statistics (TBSS) in FSL, with statistics computed only in the voxels of the white matter skeleton (FA > 0.2). Permutation based nonparametric statistics were used with 10,000 permutations, with threshold free cluster enhancement (TFCE) and corrected for multiple comparisons with family wise error correction (FWE-corrected, p< 0.05). Results: Children with epilepsy had comparable neuropsychological functioning with no significant differences in IQ (LRE mean IQ = 109; CON mean IQ = 106), working memory, or verbal fluency skills. TBSS analysis found greater FA in children with epilepsy in the right genu of the corpus collosum, extending into the body and anterior corona radiata. Conclusions: Different from most previous studies with adults or children, increases in FA were found. However, unlike most study groups of children with localization-related epilepsy, these children were comparable in neuropsychological functioning and had normal MRIs. Perhaps, the increased FA is a marker of compensation or adaptation that facilitates their good neuropsychological outcomes. These results prompt inquiry into larger studies that examine the subsets of patients that have better outcomes.