Abstracts

Rationale: Regional homogeneity (ReHo) analysis of blood oxygen level-dependent (BOLD) signals has demonstrated localized signal synchrony and disease-related alterations in a number of instances. Since the BOLD signal of functional MRI reflects neural activity, abnormal ReHo is probably related to changes in the temporal aspects of the spontaneous neural activity in the regional brain. Therefore, it is rational to address the functional connectivity of seizure genesis or propagation. Methods: Eyes closed resting state fMRI (RS-fMRI) data were obtained from 16 epileptic patients (6 males and 10 females, mean age = 32.7 10.5 years) with focal neocortical seizures and 16 age- and gender-matched healthy subjects (6 males, mean age = 33.1 10.1 years). All of the patients had no visible MRI lesion, no epileptiform discharge from T3, T4 and had a history of secondarily generalized convulsions. They remain seizure freedom with monotherapy of antiepileptic drug. Individual ReHo maps were generated by assigning each voxel a value corresponding to the Kendall's coefficient of concordance (KCC) of its time courses with its nearest 26 neighboring voxels.The processed images were smoothed with an isotropic Gaussian kernel (full-width at half-maximum, 4 mm).Two-sample t-test with age and gender as covariates between the patient group and the control group were conducted in a whole-brain voxel-wise way by using REST toolbox. Voxels with p < 0.01 and cluster size > 513mm3 (19 voxels), which resulted in a corrected threshold of p < 0.01 determined by AlphaSim (rmm = 6 mm), were regarded to show a significant difference between the two groups.Brain regions showing significant differences (p < 0.01, corrected) in regional ReHo between groups were first created for regions of interest (ROI) masks.These ROI masks were then back-projected to the smoothed images of each patient,and mean ReHo values of the ROIs in each patient were also extracted using REST. Results: A two-sample t-test was performed to examine differences between patients and healthy controls as can see in Fig 1 and Table 1. Patients showed increase ReHo in comparison to healthy controls in crus I of cerebellar hemisphere (left), superior temporal pole(right), lingual gyrus (right), Lobule IV, V of vermis and putamen (left). Significantly decreased ReHo was seen mainly in inferior temporal gyrus (Right), inferior occipital cortex (left), medial frontal gyrus(left) and precentral gyrus(right) Conclusions: Even our patients could be categorized into "MRI-negative" and "medically effective" focal neocortical epilepsy, the BOLD-ReHo was different from healthy subjects. The most gray-matter areas of significant increased ReHo were consistent with a previous study in which ReHo analysis was employed in patients with mesial temporal lobe epilepsy. Impressively, the increased white-matter ReHo located at the major white-matter fiber bundles: commissure fiber, association fiber and projection fiber. Our findings suggest that the increased ReHo in specific regions that might be responsible for generation and propagation of seizures. Funding: No