Trephination

Trephination, also called trepanation, is the surgical removal of a piece of bone from the skull of a living person. The two words are used interchangeably. Strictly, a trephine is a circular, crown-shaped saw, and trepan is an older word for a similar boring tool. Many trephinations used neither. Holes were also made by scraping the bone thin, cutting grooves, or drilling a ring of small holes and joining them.

Trephined skulls have been found on several continents, some of them Neolithic. The practice was not confined to one culture or period. Its largest known archaeological record comes from the Andes, where hundreds of trephined skulls have been studied.

Why it was done cannot always be read from bone alone. Where the same skull shows a fracture, treatment of a head injury is the likely reason. Greek and Roman medical writing, including the Hippocratic treatise On Wounds in the Head and Celsus's De Medicina, describes trephining in some skull injuries and describes the instruments.

1. The scalp was cut and drawn back to expose the bone.
2. Bone was removed by scraping, grooving, drilling or sawing.
3. In a fractured skull, the aim was to lift or remove broken bone and to let out blood or fluid pressing on the brain. Ancient writers warned against damaging the membrane that covers the brain.

Survival can be read from the bone. When a person lived for weeks or months after the operation, the cut edges show new bone growth and become smooth and rounded. Sharp, unhealed edges point to death during or soon after the operation. In the Peruvian material, studied by John Verano and others, a large share of skulls show healing, and the share appears higher in later periods.

• Andean Peru. Many trephined skulls belong to adult men and show signs of earlier skull injury, which researchers link to violence with weapons such as clubs and slingstones.
• Neolithic Europe. Healed trephinations show the operation was performed, and survived, thousands of years before any written medicine.