In normal patients, blood and cerebrospinal fluid (CSF) contain circulating cells and other molecules such as proteins and nucleic acids. In patients with central nervous system (CNS) and other conditions, the levels of these molecules may be altered. In several other studies at our institution, the investigators are investigating such molecules in tumor specimens as well as the blood and cerebrospinal fluid of pediatric patients with CNS tumors. However, these levels are difficult to interpret without comparing them to levels in patients without CNS tumors. The investigators propose a study to collect small amounts of blood and cerebrospinal fluid from pediatric patients without CNS tumors who are undergoing a diagnostic or therapeutic neurosurgical procedure aimed at addressing altered CSF dynamics.

Inclusion Criteria:

• Children without central nervous system tumors who are undergoing a neurosurgical procedure to address hydrocephalus during which CSF will be obtained
• Between the ages of 1 year and 21 years
• Patients must be having blood draws, lumbar punctures or CSF sampling from Ommaya reservoirs or VPS as part of routine clinical care.

Exclusion Criteria:

• Patients who do not require routine blood draws and/or CSF collection as part of their routine clinical care
• Patients who are considered too ill to participate as determined by their treating physician
• Patients with documented bacterial of viral infections of the CSF, brain parenchyma and/or neurosurgical devices and/or
• Patients with suspected de-myelinating conditions
• Patients who are pregnant or lactating.

All children without central nervous system tumors between the ages of 1 year and 21 years who are undergoing a neurosurgical procedure to address hydrocephalus during which CSF will be obtained will be considered