Abstract: The cephalorachidian liquid drain pressure control device comprising a body that can be cylindrical or any other geometrical shape, made from a rigid, biocompatible and stable plastic or other material with similar characteristics. The lower part of the body has one or several perforations and the upper part is internally threaded. It further comprises a threaded cap made from a rigid, biocompatible and stable plastic or other material with similar characteristics and having at the center thereof a perforation in which is mounted the bellows shaped elastic element controlling the drain pressure. This bellows shaped elastic element has one or more ripples or any other form allowing it to act as a spring and being provided in one of its ends with a disk shape forming part of the flow block mechanism (check). However, this flat and circular shape is not necessarily integrated with the elastic element acting as a spring.