Inclusion Criteria:  Age ≥ 18 years with pathologic diagnosis of a supratentorial diffuse astrocytic or oligodendroglial tumor Patients must be able to provide informed consent  Exclusion Criteria:  A pre-existing seizure disorder or epilepsy syndrome prior to tumor diagnosis Active maintenance therapy with an antiepileptic seizure drug (AED) prior to diagnosis of tumor Patients who have experienced an epileptic seizure as the presenting symptom of their brain tumor Predicted life expectancy of less than 6 months from the time of screening Pregnancy Patients with clinically significant hepatic disease (elevated aminotransferases [bilirubin, alkaline phosphatase] > 3 times upper limit normal) Patients with stage 4 or greater renal disease (GFR <30 mL/min/1.73 m2) Patients who are unable to swallow a tablet Patients with active suicidal ideation or a history of suicide attempt or other serious psychiatric disorder having required hospitalization within the previous 2 years.