Trepanning, also known as trepanation, trephination, trephining or making a burr hole is a surgical intervention in which a hole is drilled or scraped into the human skull, exposing the dura mater, to treat health problems related to intracranial diseases or release pressured blood buildup from an injury. It may also refer to any “burr” hole created through other body surfaces, including nail beds. It is often used to relieve pressure beneath a surface. A trephine is an instrument used for cutting out a round piece of skull bone.
In ancient times, holes were drilled into a person who was behaving in what was considered an abnormal way to let out what people believed were evil spirits. Evidence of trepanation has been found in prehistoric human remains from Neolithic times onward. The bone that was trepanned was kept by the prehistoric people and may have been worn as a charm to keep evil spirits away. Evidence also suggests that trepanation was primitive emergency surgery after head wounds to remove shattered bits of bone from a fractured skull and clean out the blood that often pools under the skull after a blow to the head. Hunting accidents, falls, wild animals, and weapons such as clubs or spears could have caused such injuries. Trepanations appear to have been most common in areas where weapons that could produce skull fractures were used.