ABSTRACT
Trephining, or trepanning, is a surgical operation of quite considerable antiquity. It entails cutting a piece of bone out of the skull to expose the brain. Surgeons carry out the operation for a variety of reasons, mostly in order to effect delicate brain surgery, such as the removal of a tumour. But it is a constant source of mystery why such a hazardous operation should have been carried out in ancient times and, considering the medical resources then available, how it was done. In many societies headaches and other disorders were thought to be induced by evil spirits entering the brain, and therefore a hole had to be made to let them out. In some cases it was thought necessary to reduce pressure on the inside of the skull, while in other instances more magical reasons may have prevailed, since the removed roundels were used as charms.
