 The objective of this pilot study is to perform a set of pressure and flow rate measurements in order to quantitatively characterize safe irrigation or flushing of a ventricular shunt catheter, a routine maneuver performed by a neurosurgeon during a shunt revision surgery. This maneuver involves injecting saline with a syringe to clear plugged shunt catheters. Based on data obtained in Stage I of the study, a device has been fabricated which provides the same small-volume pulse of fluid used by surgeons. In Stage II of the study, pressure and flow rate measurements generated by this specialized flusher device will be collected and measured. 