The present invention relates to a drainage valve (1) intended to be implanted under the skin of a patient and to drain cerebrospinal fluid, comprising: - a body (2) defining a chamber (3) into which an orifice opens inlet (5) and an outlet (6) of the cerebrospinal fluid, a shutter (11) adapted to seal at least partially or completely the inlet orifice (5), - a return member elastic member (13) arranged to constrain the shutter (11) so as to urge it resiliently towards the inlet orifice so that the passage of cerebrospinal fluid through the orifice entry is only possible if its pressure is greater than or equal to an opening pressure, - a rotor (8) housed in the chamber, able to rotate about an X-axis pivot and having a cam path (19 ) on which rests the elastic return member (13) so that the stress exerted by the body d the elastic return (13) on the shutter (11) is modified by the rotation of the rotor (8), the cam path being defined by an internal profile of the rotor, oriented towards the axis X, so that the member resilient return means (13) exerts on the cam path (19) of the rotor (8) a force, called "traction force", comprising a centrifugal component, with respect to the axis X. La présente invention concerne une valve de drainage (1) destinée à être implantée sous la peau d'un patient et à drainer du liquide céphalo-rachidien, comportant : - un corps (2) définissant une chambre (3) dans laquelle débouchent un orifice d'entrée (5) et un orifice de sortie (6) du liquide céphalo-rachidien, un obturateur (11) apte à obturer au moins partiellement, voire totalement, l'orifice d'entrée (5), - un organe de rappel élastique (13) agencé pour exercer une contrainte sur l'obturateur (11), de manière à le pousser, de manière élastique, vers l'orifice d'entrée de manière que le passage de liquide céphalo-rachidien par l'orifice d'entrée ne soit possible que si sa pression est supérieure ou égale à une pression d'ouverture, - un rotor (
