Ommaya Reservoir Placement for Brain Tumor Biomarker Access

Inclusion Criteria: * Age \> 18 years. * Clinical and radiographic evidence suggesting a diagnosis of a brain tumor. * Planned neurosurgical procedure resection of suspected or previously diagnosed brain tumor as part of routine clinical care. * Willing to undergo neurosurgical resection at Mayo Clinic (Rochester, MN). * Willingness of the patient or an authorized representative to provide informed consent * Patient is willing to have their Ommaya sampled on at least 2 future occasions. * Patients is willing to have CSF banked through the neuro-oncology biorepository (requires a separate signature) Exclusion Criteria: * Vulnerable populations including pregnant women, prisoners and individuals \<18 years old. * Patients who are not appropriate candidates for surgery due to current or past medical history or uncontrolled concurrent illness. * Prior history of any wound infection * Any patient who the surgeon feels is not an optimal candidate for Ommaya reservoir placement. Such reasons could (but need not necessarily) include factors related to surgical anatomy, clinical evidence of significant immunosuppression, and/or elevated risk of wound infection due to diabetes, smoking history, morbid obesity, or any other concerns. * Any patient for whom a clinical contraindication exists to a lumbar puncture (LP) will be excluded from the LP portion of this protocol, but would still be eligible for an Ommaya reservoir if they meet the inclusion criteria of the study. For example, a patient with a large posterior fossa mass lesion at risk of herniation, or a patient with coagulopathy, or other contraindication to lumbar puncture would not be eligible to participate via use of lumbar puncture for CSF access