Inclusion Criteria:  Patient presenting between September 1, 2021 and Feb 28, 2022 for elective procedure Males or females of >18 years Patient will be undergoing primary craniotomy (with general anesthesia) for suspected high-grade primary glial brain tumor (WHO grade III and IV)  Exclusion Criteria:  Patients of pediatric age group and pregnant patients Patients previously diagnosed with severe adrenal dysfunction (over activity or insufficiency) Suspected low grade (grade I, II), glioma, tumors involving brainstem and optic tract, and as well as non-glial tumors (i.e. suspected brain metastasis) Awake craniotomies Any conditions that preclude postoperative MRI Motor evoked potential monitoring or any other intraoperative condition that renders choice of anesthetics affected. Recurrent GBM