An implantable device intended to divert excessive cerebrospinal fluid (CSF) from the brain ventricles to either the peritoneal cavity or the heart right atrium (i.e., dual-capability), where it can be absorbed into the body, as a treatment for increased intracranial pressure (e.g., caused by hydrocephalus). It consists of: 1) an intracerebral ventricular catheter through which CSF flows; 2) a mechanical shunt valve that typically opens at a pre-set pressure; and 3) a peritoneal/atrial catheter that channels the CSF to the peritoneal cavity or right atrium; some types have a port/reservoir for hypodermic sampling/infusion. Disposable devices associated with implantation may be included.