Feasibility of Intraoperative Microdialysis During Neurosurgery for Central Nervous System Malignancies

Inclusion Criteria: * Age \>= 18 years * Diagnosis of the following, based on clinical and radiographic evidence: * Any glioma * Metastatic brain tumor of any primary origin * Epileptic focus requiring surgical resection * Planned neurosurgical procedure for purposes of biopsy or resection of suspected or previously diagnosed brain tumor (primary or metastatic) or epileptic focus as part of routine clinical care * Willing to undergo neurosurgical resection or biopsy at Mayo Clinic (Rochester, Minnesota \[MN\]) * Ability to understand and the willingness to sign a written informed consent document Exclusion Criteria: * Vulnerable populations: pregnant women, prisoners or the mentally handicapped * Patients who are not appropriate candidates for surgery due to current or past medical history or uncontrolled concurrent illness