Why are patients with absence seizures absent?: Combined EEG, fMRI, and Behavioral Testing in Childhood Absence Epilepsy

Typical childhood absence epilepsy (CAE) seizures cause transient impairment of consciousness in children and are accompanied by 3-4 Hz spike-wave discharges (SWD) on EEG. However, SWD can also occur in other generalized epilepsy disorders and do not always cause impaired consciousness. Prior EEG-fMRI studies of SWD have shown a specific network of cortical and subcortical changes during these electrical events. However, fMRI during typical absence seizures with confirmed conscious impairment has not been investigated. The principal aim of this thesis involves using simultaneous EEG-fMRI to identify specific cortical and subcortical networks selectively involved in CAE seizures. Behavior is assessed using two tasks: one for attention and one for sustained motor performance.;The introductory chapter starts with a discussion of studies investigating specific cognitive deficits caused by absence seizures. First reviewed are electrophysiological and imaging studies aimed at elucidating the mechanisms underlying different aspects of attention. Next, models of attention are reviewed. Finally, the continuous performance task (CPT) is introduced, followed by its use as a measure of sustained attention and the extent to which it is sensitive to brain dysfunction.;Chapter 2 outlines the results of combined EEG-fMRI and behavioral testing in 32 children with typical CAE. The results indicate that during absence seizures with impaired behavioral performance there are fMRI changes in a network of cortical-subcortical structures important for attention as well as primary sensory-motor information processing. Functional MRI changes did not occur in these structures during seizures when attentional performance was not affected.;The results of this study have important implications for understanding fundamental mechanisms of impaired cognitive function during absence seizures and are discussed with future directions in Chapter 3. An appendix (Chapter 4) contains EEGs of seizures discussed in Chapter 2.