Authors :
Presenting Author: Maria Claudia Burbano, MD – Schulich School of Medicine and Dentistry, Western University
Aayesha J. Soni, MD – Schulich School of Medicine and Dentistry, Western University
John ALS Perez, MD – Schulich School of Medicine and Dentistry, Western University
Amit Persad, MD – Schulich School of Medicine and Dentistry, Western University
Khalid Alorabi, MD – Schulich School of Medicine and Dentistry, Western University
Poul H. Espino, MD – Schulich School of Medicine and Dentistry, Western University
Poornima N Nambiar, MD – Schulich School of Medicine and Dentistry, Western University
David Diosy, MD – Western University
Michelle-Lee Jones, MD, MDCM, FRCPC, CSCN – Western University
Ana Suller-Marti, PhD – Western University
Keith W MacDougall, MD – Western University
Jonathan C Lau, MD, PhD – Western University
David A Steven, MD, MPH, FRCSC, FACS – Western University
Jorge Burneo, MD, MSPH, FAAN, FAES, FRCPC – Western University
Giovanni Pellegrino, MD, PhD – Western University
Rationale:
Scalp electroencephalography (EEG) may reveal bilateral independent or unclear (BI/U) ictal onset patterns in patients with focal drug-resistant epilepsy, presenting a significant challenge to surgical decision-making. The utility of stereo-electroencephalography (SEEG) in this subgroup, particularly the probability of delineating a single seizure onset zone (SOZ) that would permit curative resection, remains poorly understood. This study investigated whether BI/U scalp EEG findings may be used as a predictor for the diagnostic and therapeutic yield of SEEG, and inform the selection of appropriate SEEG candidates in this subgroup.
Methods:
We conducted a retrospective cohort study of consecutive patients with focal drug-resistant epilepsy and BI/U ictal onset on scalp EEG who underwent SEEG evaluation at the London Health Sciences Centre (Ontario, Canada) between January 2012 and December 2024. All patients had undergone comprehensive non-invasive and invasive presurgical assessment. Surgical outcomes were determined using the Engel classification following at least one year of postoperative follow-up. A blinded decision validation sub-study with a simulated epilepsy surgery conference was also performed. Blinded to actual outcomes, the team made decisions regarding SEEG and surgical interventions when patients found to have a single SEEG SOZ were presented. Responses were stratified to inform the added diagnostic value of SEEG.
Results:
A total of 255 SEEG cases were screened and 84 patients (33% of all cases performed over 13 years) met inclusion criteria. Females made up 56% with a mean age at seizure onset of 14.2 ± 10.4 years, of whom 65.5% were classified as having temporal lobe epilepsy (TLE). A single SOZ was identified on SEEG in 14.3% of patients (TLE 14.6%, extratemporal 13.8%; p > 0.200). Curative focal resective surgery was performed in 12% (n=10), with long-term Engel I outcomes achieved in only one patient (1.2%). Palliative resections were performed in 26% (n=22), with Engel I outcomes observed in 7% (n=6). In 50% of the blinded cases, the epilepsy surgery team reported that they would not have recommended SEEG based on phase I data alone.
Conclusions:
These findings suggest that patients with BI/U scalp EEG SOZs may be associated with a low likelihood of identifying a single SEEG SOZ and curative outcome. Using BI/U scalp EEG ictal onset as a single predictor in preoperative decision-making will refine SEEG candidate selection in this complex surgical subgroup. Funding:
No funding was received towards this work.