This observational trial evaluates the use of Ommaya reservoir placed during a biopsy to collect biomarkers longitudinally in patients with brain tumor. A biomarker is a measurable indicator of the severity or presence of the disease state. An Ommaya reservoir is a small device that's implanted under the scalp. It allows the doctor to take samples of cerebrospinal fluid (CSF) in the future without doing a spinal tap. The identification of biomarkers in CSF is rapidly emerging as a promising minimally invasive approach for monitoring tumor growth and response to therapy. In the future, these biomarkers may be used to help determine what treatments could be most effective and how well a tumor has responded to prior therapy. Currently, limited long-term access to CSF has made it difficult for studies to learn if collecting CSF at different points in the treatment process is useful. Having an Ommaya reservoir placed during a biopsy may allow for longitudinal biomarker collection in patients with brain tumor.

Inclusion Criteria:

• Clinical and radiographic evidence suggesting a diagnosis of a brain tumor
• Planned biopsy for suspected or previously diagnosed brain tumor as part of routine clinical care at Mayo Clinic (Rochester, Minnesota [MN])
• Willingness of the patient 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:

• Adults lacking capacity to consent
• Vulnerable populations including pregnant women, prisoners, and individuals < 18 years old
• Patients who are not appropriate candidates for biopsy due to current or past medical history or uncontrolled current illness
• Prior history of any wound infection
• Any patient who the surgeon feels is not an optimal candidate for Ommaya reservoir placement. Such reasons may include, but will not be limited to, surgical anatomy, clinical evidence of immunosuppression, and/or elevated risk of wound infection due to diabetes, smoking history, morbid obesity, or any other concerns