Cerebrospinal fluid shunts are one of the greatest advances of modern neurosurgery and represent a shift in the treatment of hydrocephalus. The underlying physical principle is quite simple and consists of diverting the flow of cerebrospinal fluid to either intracranial structures, jugular system, right heart atrium, pleura, peritoneum or to other natural cavities, such as the omental bursa and even the bladder. All systems operate by means of a differential pressure between the proximal catheter and distal catheter and are composed of ventricular and distal catheters, and a valve, which is the device that allows unidirectional cerebrospinal fluid flow. Current valve technology allows control of the shunt through regulation of drainage pressure, flow regulation or anti-siphon devices. There are valves with low, medium and high pressure designed to open and allow the flow out of CSF when the intraventricular pressure rises above the opening pressure. In contrast to fixed pressure and programmable pressure, valves with flow regulation attempt to maintain constant flow despite changes in the fluid pressure and patient position. Anti-siphon devices are used to avoid the siphon effect and prevent under- or over-drainage of fluid. We discuss briefly the current aspects of hydrodynamics and update valve technology.
KEYWORDS:
hydrocephalus; cerebrospinal fluid shunt; technology
