The Role of Preoperative Scalp Video-Electroencephalography and Intraoperative Electrocorticography in Mapping of Epileptogenic Zone in Temporal Lobe Epilepsy Surgery

Background: Temporal lobe epilepsy (TLE) is the most common type of epilepsy characterized by recurrent seizures. Resection surgery demonstrated efficacy in controlling seizures recently, and the success of epilepsy surgery is correlated with mapping of epileptogenic zone (EZ). This is achieved through pre-operative video-electroencephalography (video EEG) and intraoperative Electrocorticography (ECoG).
Aim of the study: To investigate role of preoperative scalp video EEG and intraoperative pre-resection electrocorticography in identifying the epileptogenic zone in temporal lobe epilepsy surgery.
Subjects and methods: Anterior temporal lobectomy (ATL), assisted by intraoperative ECoG, was performed on thirteen drug-resistant patients with TLE. Preoperative evaluations involved clinical semiology, scalp video EEG, MRI brain epilepsy protocol, and pre-resection and post-resection ECoG spike frequency (/min) was analyzed. After a year of follow-up, patients were divided into two categories: favorable seizure outcome (Engel class I) and non-favorable seizure outcome (Engel class II).
Results: Nine patients (69.2%) had intraoperative ECoG data that agreed with video EEG in mapping EZ. Intraoperative ECoG demonstrated epileptic discharges in all studied patients, which were in agreement with clinical semiology and MRI. There was no statistically significant difference in the pre-resection and post-resection spike frequencies between interictal and ictal video EEG recordings with and without epileptiform discharge. In all patients with a favorable postoperative seizure outcome, there was no post-resection ECoG residual epileptic discharge.
Conclusions: When video EEG is unable to localize the EZ in drug-resistant TLE patients undergoing ATL, mapping EZ using ECoG spike frequency can be utilized as a predictive method for postoperative seizure outcomes.