Abstracts

Rationale: Electrical cortical stimulation (ECS) is the standard method for pre-surgical mapping of cortical function to optimize safety of epilepsy surgery. The procedure is performed during invasive monitoring by stereo-EEG (SEEG) or subdural electrodes (SDE). This study aims to compare thresholds, incidence, and determinants of functional response, after-discharges (AD), and unwanted seizure occurrence during ECS performed in patients undergoing SEEG vs SDE monitoring.

Methods: ECS recordings were reviewed in 124 patients who underwent SDE mapping and 67 patients who underwent SEEG mapping at the Cincinnati Children’s Comprehensive Epilepsy Center from 2007-2020. Data was collected on the age of patients, the incidence and thresholds of functional response, ADs, and unwanted ECS-induced seizures. The comparison between the SDE and SEEG patient groups was analyzed using linear and generalized linear multilevel models.

Results: The mean age of patients between SDE (11.59 years) and SEEG (12.23 years) were not significantly different. Patients undergoing SDE had higher incidence of motor response (9.7% to 5.3%; OR = 0.52, P < 0.001), ADs (29.3% to 12.2%; OR 0.34, P < 0.001), and unwanted ECS-induced seizures (1.7% to 0.4%; OR 0.24, P < 0.001). Compared to the SDE group, the current thresholds for face motor (-3.05; P < 0.001), lower extremities (-3.89; P < 0.001), and upper extremities (-2.83; P < 0.001) were lower in the SEEG group. Similarly, the current thresholds for AD (-2.72; P < 0.001) and unwanted ECS-induced seizures (-2.68; P < 0.001) were lower in the SEEG group