Intraoperative seizure in the setting of tumor resection: illustrative cases.

backgroundIntraoperative seizures pose a serious threat to patients undergoing neurosurgical procedures, potentially disrupting cases and increasing postoperative complications. While established risk factors, such as history of seizures and tumor location, are well documented, emerging evidence indicates hypocapnia, induced by controlled hyperventilation, may further reduce seizure threshold. Nevertheless, clinical data directly linking hyperventilation to intraoperative seizure incidence remain sparse in the current literature. OBSERVATIONS: The authors present the cases of 3 patients with skull base tumors who experienced intraoperative seizures during elective craniotomy. In all cases, end-tidal CO2 (EtCO2) levels fell below 27 mm Hg for extended periods. Seizure activity only resolved following EtCO2 normalization and anticonvulsant administration. Notably, the patients had surgeries where physiological levels of EtCO2 were maintained, resulting in successful surgeries with no seizure activity. All tumors were located at the skull base and involved main CNS arteries, raising the possibility that altered cerebral perfusion may have contributed to increased seizure susceptibility under hypocapnic conditions. LESSONS: These cases highlight hypocapnia as a potentially modifiable risk factor for intraoperative seizures and underscore the need for judicious management. Given the risk of seizure induction under reduced cerebral blood flow, strict hyperventilation guidelines should be followed when tumors are in critical vascular territories. https://thejns.org/doi/10.3171/CASE25585.