Outcomes of Subdural Grid Electrode Monitoring in the Stereoelectroencephalography Era

Abstract

Background: Subdural grid (SDG) electrodes have been the gold standard of invasive monitoring in medically refractory epilepsy; however, in some centers, application of SDGs has been reduced by the progressive application of stereoelectroencephalography (SEEG). This study reviews the efficacy of SDG electrode monitoring after the incorporation of the SEEG methodology at our institution.

Methods: We retrospectively reviewed 102 patients undergoing intracranial monitoring via SDG electrodes during the years 2010-2013 at our institution. The series includes all patients who underwent SDG placement after the incorporation of SEEG in our extraoperative invasive monitoring armamentarium.

Results: Average patient age was 29.9 years old; the series included 31 pediatric patients. There were 49 male patients and 53 female patients. The mean length of follow-up was 21.5 months. The epileptogenic zone was localized in 99 (97%) patients. Surgical resection was performed in 84 patients, and 70% experienced Engel class I freedom from seizures.

Conclusions: Invasive monitoring via SDG electrodes continues to be an efficacious option for select patients with medically refractory epilepsy, mainly when the hypothetical epileptogenic zone is anatomically restricted to superficial cortical areas and in close relation with eloquent cortex. This is the first report of epilepsy outcomes after SDG monitoring at a center that also performs SEEG monitoring. Our results suggest a complementary benefit of performing both techniques at 1 institution.

Keywords: Epilepsy surgery; Stereotactic electroencephalography; Subdural grids.