A new valve for the treatment of hydrocephalus

Presently available hydrocephalus valves still are not perfect. There are two major drawbacks: They have a tendency to clog and do not take into account the posture of the patient. The latter results in an intracranial pressure which is either too high or too low. To avoid these problems a new valve was designed which is described in this article. It introduces a pressure control: The force on the actual valve seat is augmented and balanced by a powerful spring. The large forces generated this way are able to overcome sticking forces due to fibrin or cellular debris. The valve functions well even with viscous and sticky cerebrospinal fluid (CSF). This mechanism maintains the pressure almost independent of the composition of the CSF. A valve insensitive to the posture of the patient can create an overdrainage, causing related problems such as subdural hygromas, slit ventricle syndrome, and consecutive proximal catheter obstruction. This is avoided by the valve presented here. It has two different pressure controllers: one designed for the supine position and another designed for the upright position of the patient. When the patient stands up or sits up, the pressure controller for the horizontal position is shut off by a gravity-activated sphere, and the drainage of CSF is directed into the appropriate controller for the upright position. In this way, the change of the hydrostatic differential pressure between the ventricles and the peritoneal cavity is taken into account and the intracranial pressure remains within physiological values. Laboratory investigations have shown that the new valve performs as designed.