T149. After-discharges and seizures during functional brain mapping with extra-operative electrical cortical stimulation

Introduction Electrical cortical stimulation (ECS) is the clinical standard for brain mapping to define the relationship between seizure-onset zone and functionally eloquent cortex in patients undergoing presurgical evaluation with intracranial electrodes. ECS-induced after-discharges (ADs) and seizures contribute to the morbidity and compromise the validity of ECS results. This study examines the incidence, thresholds, and determinants of ECS-induced ADs and seizures. Methods A retrospective review of clinical information and extra-operative electrocorticography (ECoG) recordings was performed in pediatric patients to determine incidence and thresholds of ECS-induced Ads and seizures. Multivariate models were used to evaluate predictors of AD and seizure occurrence and their thresholds. Results A total of 122 children were included. The incidence of ADs and seizures were 77% (94/122) and 35% (43/122) respectively. Males (OR 2.92, 95% CI 1.21–7.38, p  = 0.02) and patients with MRI-negative epilepsy (OR 3.69, 95% CI 1.24–13.7, p  = 0.03) had increased odds of ECS-induced ADs. A significant trend for decreasing AD thresholds with age was seen (regression co-efficient 0.151, p  = 0.011). ECSinduced seizures were more likely to occur in patients with lateralized positron emission tomography (OR 6.62, 95% CI 1.36–55.56, p  = 0.036) and presence of ADs (OR 3.50, 95% CI 1.12–13.36, p  = 0.043). Conclusion ECS functional brain mapping is associated with a high incidence of ADs and seizures. Increasing age is significantly associated with decreasing current thresholds and increased probability of occurrence of ADs and seizures. These findings underscore the need to develop safer method(s) for mapping brain function, particularly in children.