The association between the degree of intraoperative bisynchronization blockade and drop attack freedom after corpus
Jeffrey P Turnbull1, Daniel W Griepp1, Ethan Wood1,2
11Department of Neurosurgery, Michigan State University College of Human Medicine, Henry Ford Providence Hospital, Southfield, Michigan.
Objective:
The aim of this study was to evaluate the prognostic value of intraoperative EEG during corpus callosotomy (CC) in pediatric patients with drug-resistant epilepsy (DRE), with a particular focus on bisynchronization blockade and its correlation with long-term seizure outcomes.
Methods:
A retrospective review was performed of pediatric patients with DRE and injurious drop attacks who underwent CC between 2005 and 2024. Patients were stratified into three groups based on intraoperative scalp EEG findings: 1) > 50% bisynchronization blockade, 2) < 50% blockade, and 3) absent bisynchronization. Baseline clinical characteristics, surgical approach, and extent of CC were recorded. Seizure outcomes were assessed using Engel and International League Against Epilepsy (ILAE) classifications with a minimum follow-up of 1 year. Whether atonic seizures resolved postoperatively was also evaluated. Group comparisons were performed using Fisher's exact test and Kruskal-Wallis rank-sum testing.
Results:
Forty-six patients met the inclusion criteria. The majority underwent complete CC (65%), most via an open approach (67%). At 1 year, freedom from atonic seizures (ILAE class 1Engel class I) was highest in the > 50% blockade group (70.0%) compared with the < 50% blockade (40.0%) and absent bisynchronization (25%) groups (p = 0.042). At last follow-up (mean 5.3 years), the > 50% blockade group similarly achieved significantly higher rates of atonic seizure freedom (ILAE class 1/Engel class I, 76%) compared with 0% in the < 50% blockade and 25% in the absent bisynchronization groups (p < 0.001). Outcomes for total seizure freedom varied and did not reach statistical significance between groups.
Conclusions:
Achieving > 50% intraoperative bisynchronization blockade during CC was strongly associated with improved long-term atonic seizure freedom. These findings support the role of intraoperative EEG as a prognostic marker of effective seizure control.
