In Detail: A ventriculostomy drainage system allows removal of cerebrospinal fluid from the brain in order to maintain a critical balance of fluid and pressure within the skull. The neurosurgeon places a small, soft silicone tube (ventriculostomy catheter) into the brain, creating a pathway for CSF to leave it in carefully controlled amounts. This prevents dangerous shifts in brain position and maintains optimal blood flow within the arteries and veins. It is also possible to use the ventriculostomy system to measure pressure within the skull.