Inclusion Criteria:

• At least 18 years old.
• Prior histological diagnosis of high grade glioma (HGG) with prior initial treatment and radiation therapy for HGG; recurrence of HGG suspected, and care plan includes surgical procedure.
• Undergoing surgical procedure for clinical reasons, and gross surgical resection not expected.
• Neurosurgeon is planning stereotactic biopsy or tumor debulking for clinical reasons; frozen tissue confirmation of malignancy during this operative procedure is necessary.
• Neurosurgeon evaluates that placement of oxygen monitoring probe after biopsy or debulking can be done safely without complications.
• Contrast enhancing disease on MRI within 21 days prior to enrollment.
• Karnofsky Performance Score ≥ 60 at Screening.
• Recovered from toxicity of prior antineoplastic therapy, and off cytotoxic chemotherapy for 7 days prior to Screening.
• Recovered from prior radiotherapy and had at least 21 days elapse since completion of radiotherapy prior to Screening.
• Recovered from prior surgery for their brain tumor in investigator's clinical judgment.
• If female, negative serum or urine pregnancy test at Screening.
• Within 2 weeks of starting study, hematologic and renal functions as specified: Absolute neutrophil count ≥ 1500/mm3, platelets ≥ 100,000/mm3, hemoglobin ≥ 9.0g/dL, creatinine ≤ 1.7mg/dl, serum bilirubin ≤ 1.5mg/dL, blood urea nitrogen within 2 times the upper limit of normal, transaminases ≤ 4 times above the upper limits of the institutional norm, and prothrombin time and partial thromboplastin time within institutional norm or below.
• Patient or patient's medical power of attorney provided written consent to participate in the study.
• Mini Mental Status Exam score ≥ 15.

Exclusion Criteria:

• Pregnant or lactating.
• Receiving concurrent cytotoxic chemotherapy for their tumor within 7 days prior to Screening, or decision is made at the time of surgery to treat with other modality of treatment (e.g., gliadel wafers).
• Serious concurrent infection or medical illness which would jeopardize the ability of the patient to safely participate.
• Behavioral, cognitive, or psychiatric disease or personal situation that might interfere with optimal participation.
• Cannot undergo an MRI.
• Received an investigational drug not approved for human use by the FDA within 30 days of enrollment.
• Previously received TSC.