Abstracts

Rationale: Medically refractory epilepsy is present in up to 70% of patients with Tuberous Sclerosis Complex (TSC). Surgery is a viable treatment option, which necessitates individualized implantation strategies for intracranial video-EEG monitoring (IC-vEEG) to identify epileptogenic zones (EZ). Stereoelectroencephalography (SEEG) has several advantages in evaluating epileptogenic neuronal networks, including electrographic and electroclinical seizure onset zones, which are often distinct and incompletely assessed in this population. Methods: A retrospective single-center analysis of all TSC patients who had undergone epilepsy surgery between 2013 and 2017 was performed. Demographic features, surgical modality, number and location of implanted electrodes, and number and location of epileptogenic zones were assessed. Subsets of electrographic compared to electroclinical seizures were analyzed to determine incidence of subclinical seizures, specifically those originating from distinct epileptogenic foci. Comparison to Phase I non-invasive vEEG data was performed. Results: Over a 4 year period, twenty patients with TSC underwent Phase II intracranial video-EEG monitoring (M:F, 1:1; age range, 10 months to 17 years; median age at surgery, 3.5years). Seventeen patients underwent SEEG with multiple multicontact depth electrodes (range 4 to 17), and 3 patients underwent craniotomy with combined subdural and depth electrode arrays. Eighteen patients had at least one or more ictal onset zones identified by intracranial vEEG (range 1 to 3), of which 15 underwent stereotactic laser ablation (SLA) and 3 underwent open resection of their epileptogenic foci. Subclinical seizures were identified in 15/20 patients (75%) during Phase II IC-vEEG monitoring, of which 7 SEEG patients (47%) had subclinical seizures originating from distinct foci compared to their clinical seizure onset zones. In comparison, electrographic seizures were identified in 7/20 patients (35%) during non-invasive Phase I vEEG monitoring. Conclusions: There is a high incidence of subclinical seizures in TSC patients undergoing intracranial vEEG monitoring, which notably exceeds that which is identifiable on non-invasive vEEG. Minimally invasive SEEG allows for diverse sampling and identifies distinct epileptogenic networks that differ between electrographic and electroclinical seizures. Further studies are needed to evaluate the clinical impact of electrographic seizures in children with TSC. Funding: None