Abstracts

Absence seizures consist of brief 5-10 s episodes of unresponsiveness, associated with a 3-4 Hz [ldquo]spike-wave[rdquo] discharges on EEG. The fundamental mechanisms of impaired attention in childhood absence epilepsy (CAE) are not known. By understanding the mechanisms and brain regions crucial for impaired attention in this patient population, new treatments may be developed with the goal of blocking seizures and preserving attention. Mechanisms of impaired attention in this form of epilepsy may have implications for treating other types of epilepsy as well., We have used simultaneous EEG and fMRI while testing attentional vigilance with a continuous performance task (CPT) in pediatric patients with typical absence seizures. To increase the chance of recording absence seizures, medications were held for up to 48 hours. Simultaneous EEG-fMRI data were acquired using a 3T MR system with continuous EPI BOLD sequence. EEG artifact was removed by post-processing using temporal PCA-based gradient noise removal. fMRI data was analyzed using SPM2., We found significant ictal BOLD signal increases in bilateral thalamus. Moderate increases were also seen in the cingulate, lateral frontal, and parietal cortex. Decreased BOLD signal was present in the retrosplenial cortex, and to a lesser degree in the bilateral frontoparietal cortex. When testing CAE patients with CPT during the interictal period, significant BOLD signal increases were seen in the bilateral fronto-polar cortex, anterior cingulate, dorsolateral frontal and parieto-occipital cortex, left fusiform gyrus, bilateral medial thalamus, upper brainstem, and cerebellum. Decreases during CPT were seen in bilateral orbital frontal cortex, precuneus, and large areas of the lateral cerebral hemispheres. Our behavioral measurements indicate ictal omission errors in 5 of 7 absence seizures that occurred during the CPT task. Omission error rate (% missed target letter X on CPT) was significantly higher in CAE patients than controls, 3.05 % in CAE patients off meds, and 0.89% in controls (p=0.04, two-tailed t-test). Variability in performance was also higher in the CAE group, where omission error rate varied from 0% to 11% between trials, while in controls it varied from 0% to 5%., These results demonstrate the feasibility of obtaining high quality EEG-fMRI during behavioral testing in pediatric patients with CAE. As in adult patients, increases and decreases were seen in frontoparietal and thalamic networks. Our initial findings also suggest that the attentional networks involved in CPT overlap with thalamocortical networks affected by CAE., (Supported by Betsy and Jonathan Blattmachr fund.)