Abstracts

Seizures associated with tuberous sclerosis complex (TSC) often become medically refractory and may interfere with development. Patients with TSC seizures, even with multifocal sources, can benefit from epilepsy surgery if the sources can be reliably localized. Identification of the ictogenic tuber for surgical planning is complicated in many cases by the presence of multiple potentially epileptogenic tubers and often an early generalized appearance by semiology or EEG. An ability to map seizure proclivity across cortical regions would therefore be of value., A retrospective review identified TSC patients who underwent resections following intracranial EEG (ICEEG) monitoring at New York University[apos]s Comprehensive Epilepsy Center for treatment of refractory seizures. Tubers from which data were recorded during monitoring were classed as epileptogenic depending on resection and surgical outcome. Analysis of wideband synchrony was performed in signals recorded from orthogonally adjacent pairs of electrodes in subdural grids and strips in selected interictal samples. Local hypersynchrony (LH) was identified by applying a linear discriminator to the data set to identify electrode pairs with significantly elevated interictal synchrony. The location of the electrode pairs with the LH property was correlated with the locations of tubers using perioperative neuroimaging and intraoperative photographs., We evaluated the role of local network interactions in the genesis of TSC seizures and assessed their potential utility as markers of this tendency. Measurement of local synchrony on intracranial EEG recordings from the included subjects revealed that seizure-generating tubers are bordered by regions of synchrony significantly higher than those that surround non-epileptogenic tubers., Hypersynchrony appears to reflect the underlying connectivity pattern rather than transient activation, as it was present even in interictal or quiescent periods. Our results imply that there is increased local neuronal connectivity at the intersection of normal and dysplastic tissue, and that this feature is related to the generation or spread of seizures. This provides a marker that can be used to identify tubers as resection candidates for optimal surgical outcome. This technique may be a useful adjunct to conventional EEG interpretation in these patients, and may obviate the need for prolonged monitoring or multiple surgeries in some cases., (Supported by 1 K08 NS48871 R1A1 (C. Schevon).)