CerebroSpinal Fluid (CSF) is produced constantly in the brain chambers (ventricles). It leaves the ventricles, circulates over the surface of the brain and into the spinal sac, where it is reabsorbed. If there is a blockage in the circulation, or a reduction in absorption, the fluid builds up in the brain cavities. This may result in enlargement of the ventricles and increase in Intracranial Pressure (ICP).

A CSF shunt is a device that bypasses the blockage or absorption defect and drains the CSF from its cavities (brain chambers, CSF cysts) into other cavities (peritoneal cavity, pleural cavity, or blood stream.) The CSF flow is controlled by a valve  that regulates pressure and/or by other flow regulating devices (anti-syphon device). The most modern valves allow their pressure to be changed from the outside without surgery (programmable valves).

The entire system (catheter, tubing, valve assembly) is internal and placed under the skin.