Three stage intracranial pressure relief valve having single-piece valve stem

摘要

An implantable valve for allowing the passage of cerebrospinal fluid (CSF) from a ventricle of the brain to a suitable drainage location in the body includes a movable diaphragm (45), one side of which is in pressure communication with the drainage location of the body and the other side of which is in pressure communication with the ventricular spaces of the brain. A valve assembly, actuable by displacement of the diaphragm in response to applied pressure differentials, regulates passage of CSF from the ventricular spaces to the drainage location. When the pressure differential is relatively small, the valve operates in a constant pressure mode to maintain a predetermined pressure differential across the valve. In response to a sudden increase in differential pressure, the valve mechanism operates in a constant flow mode to maintain a desired relatively constant CSF flow rate through the valve. Above a predetermined pressure differential, the valve operates in a constant pressure mode to maintain a predetermined maximum pressure differential across the valve. To simplify construction, the valve includes a single-piece valve stem (68) having a ramp surface (72) at one end and a fluid restrictor surface (73) at the other end which cooperate with the valve diaphragm to provide the three operating modes.