Epileptogenicity post Stereoelectroencephalography and Subdural Grids Invasive Monitoring: A Retrospective Analysis of Adult and Pediatric Patients with Refractory Epilepsy.

Objective: To assess if removal of stereoelectroencephalography (SEEG) or subdural grids (SDG) is associated with an increased seizure frequency in patients with refractory epilepsy during the immediate postoperative period.

Methods: 37 patients with refractory epilepsy that underwent monitoring with SEEG or SDG during November 2012 - March 2022 were identified using electronic medical records from a single institution. Seizure history, duration of intracranial monitoring, and monitored brain regions were recorded.

Results: 5.0% and 5.9% of SEEG and SDG patients had a seizure within 48 hours post-termination of monitoring. 25% and 11.8% of SEEG and SDG patients had a seizure between 48 hours and 1-week after surgery. Between 1 week and 1 month after SEEG or SDG removal, 35% and 41.2% of patients had a seizure. 30% and 50% SEEG or SDG patients had a seizure between 1- and 2-months following removal. Overall change in postoperative seizure frequency was not significant. Seizure frequency increased for 11.8% of SDG patients while frequency remained unchanged for 5.9% and decreased for 82.4%. No patients post-SEEG removal in our cohort experienced an increased seizure frequency. 95% experienced a decrease in seizure frequency and no change was observed in 5%.

Conclusion: SEEG is not associated with increased epileptogenicity after termination of monitoring. Two patients post-SDG removal experienced an increase in seizure frequency. While patients with refractory epilepsy may continue to have seizures during the immediate postoperative period, it is likely that patients will experience a decrease in seizure frequency after removal of SEEG or SDG.