Abstracts

Recognized as an abnormal electroencephalographic EEG characteristic, paroxysmal fast activity (PFA) is typically a bilateral non-localizing finding associated with generalized tonic seizures in the Lennox-Gastaut Syndrome. The significance of focal PFA as a marker of epileptogenesis is not known. The purpose of this study was to determine if interictal PFA is a non-invasive surrogate marker of the epileptic cortex in pediatric epilepsy. All video EEG (VEEG) of children were reviewed for the 2001 calendar year at UCLA (n=260), and the location of interictal PFA and seizure onsets determined. In addition, whether PFA was capable of identifying new or previously unknown cortical regions of independent seizure generation was examined by investigating the relationship of contralateral PFA and post-hemispherectomy seizure outcome for all children at our institution from 2000 to 2003. Interictal PFA occurred exclusively in the sleep state. Interictal PFA was bilateral, focal, or multifocal, and co-localized with the seizure onset zone within the same VEEG, with a sensitivity of 90%, a specificity of 67%, and an accuracy of 83%. In post-hemispherectomy children, the presence of preoperative PFA contralateral to the side resected predicted post-surgery epilepsy, with a sensitivity of 83%, specificity of 80%, and accuracy of 81%. We found a strong association between the locations of interictal scalp-recorded PFA and seizure onset zones. Furthermore, PFA in the contralateral hemisphere predicted, preoperatively, who was at risk for post-operative epilepsy in our post-hemispherectomy children. Both of our findings validate the potential of interictal PFA as a non-invasive surrogate marker of the epileptic cortex in pediatric epilepsy and epilepsy surgery patients. (Supported by RO1 NS38992 to GWM.)