The gravitational shunt: an alternative approach to cerebrospinal fluid shunting

Current cerebrospinal fluid shunts use complex differential pressure values to regulate drainage. Such systems are prone to overdrainage and obstruction, and thus have an unpredictable effect on intracranial pressure (ICP). The gravitational shunt (GS) introduces an alternative approach. It uses a single, simple valve to balance the pressures generated within a vertical shunt system. The ICP is then regulated by the position of the valve along the cranioabdominal shunt axis and not by the mechanical properties of the valve. Bench testing demonstrated that when using the GS (1) a linear correlation (r = 0.91, p < 0.001) exists between the ICP and the position of the valve along the vertical shunt axis, (2) positive and negative ICPs are maintained, and (3) the ICP can be predicted by an equation derived from theoretical principles. The GS uses a single, simple valve as a pressure regulator and an antisiphon device. It allows the maintenance of a normal negative ICP in the upright position without risk of over-drainage. The other benefits of this system are discussed.