S198 Different region-specific networks sustain focal seizures with a fast-activity onset: Evidence from patients and animal models

Abstract

Focal seizure patterns generated by different cortical networks are not well characterized. I will provide evidence that different seizure patterns are generated by specific brain regions explored with stereo-EEG in patients with drug-resistant focal epilepsy candidate for surgery. Two main patterns typical of temporo-mesial involvement and neocortical involvement are identified. These two patterns were reproduced in an in vitro isolated brain preparation to characterize the network and cellular determinants. Two distinct seizure types area simultaneously induced in the limbic regions and in the olfactory areas by perfusion of the preparation with 4-aminopyridine. The mechanisms that initiate and sustain these patterns will be described by a combined neurophysiological study that includes the use of multichannel extracellular, potassium-sensitive and intracellular recording electrodes. Seizures in the limbic region start with a prominent activation of inhibitory networks and are characterized by a stereotypical tonic and bursting phase; limbic seizure usually last longer then 30 s and involve the activation of thalamic nuclei. Olfactory seizures are brief events (