Postoperative Seizure in Patients with Malignant Glioma Undergoing Tumor Resection with Intraoperative Mapping: Risk Factors, Management Strategies, and the Utility of Bayesian Analysis in a Case-Control Cohort

BACKGROUND Postoperative seizures can occur secondary to cortical irritation from malignant glioma resection or from direct electrical stimulation of the cortical surface during intraoperative brain mapping. A paucity of literature exists with regards to the use of appropriate seizure risk-reduction strategies for this patient population. The objective of the study was to identify primary risk factors for early and late postoperative seizures following intraoperative brain mapping. METHODS The authors performed a case-control study with 30 patients who had postoperative clinical seizures within 6 months following craniotomies with intraoperative mapping for glioma resection from 2013 to 2021 at a single academic institution. An unmatched control population of all patients (n=52) who had undergone craniotomies with ICM during the same period and had no clinical seizures within 6 months following their operation were used for comparative analysis. Primary endpoint was any postoperative seizure within 6 months of surgery. Outcomes were analyzed both via frequentist and Bayesian statistical approaches. RESULTS Bayesian analysis using non-informative priors demonstrated that the probability of an odds ratio (OR) > 1 for prior history of seizures being a risk factor for postoperative seizures is 73%. The probability that OR < 1 for a patient with post op seizures who underwent motor mapping was 91%. If patients experienced an intraoperative seizure during mapping, the probability of having a postoperative seizure was 84%. Probability that awake mapping is protective of post op seizure when compared to asleep mapping is 88%. Complex anti-epileptic drug (AED) regimen (increasing dose + adding additional AEDs or 2 dose adjustments) had 64% probability of protection from late postoperative seizures. CONCLUSION Patients with a preoperative history of seizures may be at higher risk for postoperative seizures. More aggressive perioperative seizure prophylaxis may provide a protective benefit from postoperative seizures in patients who undergo intraoperative mapping.