A drainage valve intended to be implanted and to drain the cerebrospinal fluid, including: a body defining a chamber into which there open an inlet port and an outlet port, a stopper capable of at least partially, or indeed completely, closing off the inlet port, a resilient return member exerting a resilient push force on the stopper towards the inlet port in order to open or close the port, a rotor housed in the chamber, able to rotate about an X-axis pivot and including a cam track on which the resilient return member rests such that the force exerted by the resilient return member on the stopper is modified by the rotation of the rotor.
