Abstracts

Rationale: Childhood absence epilepsy (CAE) seizures are seen as 3-4 Hz spike-and-wave discharges on electroencephalography (EEG). Behaviorally, seizures are characterized by temporary loss of consciousness. While CAE is considered a generalized type of epilepsy, prior studies show a frontal maximum in seizure activity on EEG and involvement of areas of the brain thought to be important for attention, including the frontoparietal network and thalamus, on fMRI. The relationship between EEG changes during absence seizures and behavioral impairment is not known. Methods: We recorded 256-lead high density EEG in 20 pediatric patients as well as simultaneous 32-lead EEG and fMRI in 34 patients as they performed a continuous performance task (CPT) or an easier repetitive tapping task (RTT) requiring less attentional vigilance. Power across discrete frequency bands were compared for each electrode and determined for poor versus spared performance conditions. Signals during seizures from the high-density EEG were analyzed using source localization. Sources found with high-density EEG were compared to areas of activation in fMRI. Results: Absence seizures were associated with worse performance during the continuous performance task (CPT) compared to the repetitive tapping task (RTT), though variable performance were observed across seizures and across patients. Seizures associated with poor behavioral performance (>75% omissions) showed greater frontal 3-4 Hz power compared to seizures with good behavioral performance (<25% omissions). Source localization for seizure activity using both distributed and single dipole models localized spikes to medial frontal cortex. Sources on high-density EEG showed some concordance with activated regions on fMRI. Conclusions: Childhood absence seizures show variability in ictal task performance and power distribution on EEG. Abnormal activity in frontal cortex during absence seizures may be crucial for producing impaired attention in this disorder. Understanding electrophysiological and fMRI signals related to CAE could ultimately lead to improved treatments to prevent loss of consciousness during absence seizures.