If you have a ventriculoperitoneal (VP) or ventriculoatrial (VA) shunt in place, you will have a shunt closure test in which your shunt system will be closed and you will be monitored for 4 hours for the development of clinical signs of increased intracranial pressure. The shunt closure test is performed to allow for a long enough time for the shunt to be closed after liposomal cytarabine is injected. Researchers want to make sure that the drug will stay in the CSF system long enough to perform its function, without being siphoned off through the shunt.