Platform Session – Evoked potentials & NIOM: Factors that modify the risk of intraoperative seizures triggered by electrical stimulation during supratentorial functional mapping

Abstract

Introduction Neurophysiologic mapping via electrical stimulation is the gold standard for intraoperative functional mapping during surgeries in close proximity to eloquent cortical and subcortical regions. While it’s temporal and spatial resolution are far superior to other intraoperative and extraoperative techniques, the method carries a relatively high risk for triggering after discharges and seizures. These can not only lead to inaccurate mapping results but also pose an immediate safety risk to the patient. In the current study we aim to identify factors that impact this risk. Particularly, we are aim to study whether administration of antiepileptic (AED) drugs prior to and/or at surgery decrease the probability of triggering seizures. Methods We studied 544 consecutive mapping cases performed at an institution with tertiary care centers for epilepsy and brain tumor surgery. Applying a multivariate logistic regression model, we analyzed whether certain stimulation paradigms, patient’s state (awake versus general anesthesia), history of epilepsy, maintenance AED administration prior to surgery, and loading with AED at the beginning of the surgery do impact the risk of triggering seizures, after adjusting for potential confounders. Results Seizures were triggered in 135 patients. Penfield method of stimulation independently increased the odds of triggering seizures 5.5 times, when compared to high frequency anodal stimulation (OR = 5.6, p = 0.03) while diffuse pathology increased this risk 2.7 times (OR = 2.7. p Conclusion Intravenous administration of a loading dose of AED at the beginning of the surgery does reduce the risk of stimulation triggering intraoperative seizures, regardless of whether patient has had preoperative seizures or not. Penfield method is more epileptogenic than multipulse train technique and thus the latter should be used preferentially. Prior history of epilepsy does not increase the risk of triggering seizures, while preoperative administration of maintenance AEDs does not decrease it. Mapping in proximity to poorly defined lesions carries a significantly higher risk for triggering seizures.