Abstracts

Absence seizures occur most commonly in children. They involve brief episodes of staring and non-responsiveness. Electroencephalogram (EEG) recordings of typical childhood absence epilepsy (CAE) show bilateral 3-4 Hz spike-wave discharges. True CAE rarely persists to adulthood. Prior published reports of functional magnetic resonance imaging (fMRI) in adult patients describe variable bilateral frontoparietal fMRI increases, decreases, and thalamic increases during generalized spike-wave, with most studies performed at 1.5T. The goal of the present study is to extend these investigations to typical absence seizures in the pediatric population, which may differ from adult patients, using combined EEG and fMRI at 3T. Pediatric patients with typical absence seizures, and no other seizure types, were tested. After application of a 19 channel EEG cap connected to an EEG recorder (Neuroscan NuAmps), fMRI was performed using a 3T MR system (Siemens Trio), with continuous EPI BOLD sequence. Multiple 10 minute imaging runs were repeated up to 6 times. To increase the chance of obtaining absence seizures, patients were asked to hold medications for up to 48 hours, and were sleep deprived the night before scanning. EEG artifact was removed by post-processing using temporal PCA-based gradient noise removal. fMRI data during seizure and baseline intervals were analyzed in a general linear model using SPM2. During typical childhood absence seizures, we found significant blood oxygenation level dependent (BOLD) signal increases in bilateral thalamus. Moderate increases were found in the cingulate, lateral frontal, and parietal cortex. Decreased BOLD signal was observed in the retrosplenial cortex, and to a lesser degree in the bilateral frontoparietal cortex. Despite increased challenges of performing fMRI in pediatric patients, high quality data can be obtained in this population. As in adult patients, increases and decreases are seen in frontoparietal and thalamic networks. Further study is needed to determine whether variable involvement of different specific regions of cortex and thalamus during absence seizures is related to variable effects on cognition seen during these seizures. (Supported by Betsy and Jonathan Blattmachr Fund.)