Trepanation

Trepanation is the fine art of boring a hole in the skull in order to release the pressure of imbalanced bodily humours, or to allow brain tissues to "pulsate" freely, or to increase the flow of blood to the brain by creating an outtake valve, or possibly just to let the demons out ...

http://www.rotten.com/library/medicine/quackery/trepanation/