A portable systems release fluid pressure with a cavity within a patient. These systems include a drainage catheter, a pressure-responsive one-way valve, and a fluid reservoir all adapted to be mounted in proximity to the cavity being drained. One system in particular is used in relieving intracranial pressure. This intracranial pressure relief system may include a headband to which are mounted the one-way valve and reservoir. The drainage catheter may have mounted thereon a cranium seal formed of a soft material that contacts the inner wall of a cranium bore hole. The cranium seal may have threads to facilitate advancement into the bore hole.
