Incan skull surgery

When Incan healers scraped or cut a hunk of bone out of a person’s head, they meant business. Practitioners of this technique, known as trepanation, demonstrated great skill more than 500 years ago in treating warriors’ head wounds and possibly other medical problems, rarely causing infections or killing their patients, two anthropologists find.

Trepanation emerged as a promising but dangerous medical procedure by about 1,000 years ago in small communities near the eventual Inca heartland in Peru’s Andes mountains, say Valerie Andrushko of Southern Connecticut State University in New Haven and John Verano of TulaneUniversity in New Orleans. Incan healers later mastered certain trepanation methods, performing them safely and frequently.

“Far from the idea of ‘savages’ drilling crude holes in skulls to release evil spirits, these ancient people were highly skilled as surgeons,” Andrushko says.

The researchers’ new investigation, published online April 3, will appear in the American Journal of Physical Anthropology.

Prehistoric trepanation in this part of South America consisted of four techniques, the scientists say. Practitioners cut out squares of bone, bored holes in the skull, scraped away bone to create an opening or made circular incisions to remove a plug of bone. Inca surgeons specialized in the latter two methods. Excavations, however, have not yielded trepanation instruments.

In pre-Inca times, only one-third of skull surgery patients survived the procedure, as indicated by short- or long-term healing around cranial openings. Survival rates rose to between 80 and 90 percent during the Inca era, from A.D. 1400 to 1532. Few skulls showed signs of infection near surgical holes.

Most recipients of skull surgery displayed one trepanation hole. A substantial minority exhibited from two to seven such openings.

Incan surgeons avoided cutting cranial muscles and vulnerable parts of the skull, the scientists say. These practitioners also managed not to sever internal blood vessels or the membrane encasing the brain.

Particularly among the Inca, trepanation was often used to alleviate fluid buildup and inflammation caused by head wounds incurred during fighting or warfare, the authors suggest. These cases typically involved young men with fractures abutting surgical cavities on the skull’s front left side, where a right-handed opponent would have inflicted maximum damage.

Trepanation may have served other medical purposes, such as treating painful inner-ear infections, the researchers add. Women sometimes received skull surgery, but it’s not clear why.

For more than a century, researchers have analyzed trepanned skulls with uncertain or approximate ages in museum and university collections. Various medical and ritual explanations for the procedure have been proposed.

Unlike those efforts, the new study “really gives us a sense of what life was like for ancient Andean populations,” remarks bioarchaeologist Tiffiny Tung of Vanderbilt University in Nashville. This study focused on radiocarbon-dated skulls from recently excavated sites, allowing estimates of how common and successful trepanation was for each ancient community over thousands of years, Tung says.

From 411 skulls unearthed by different teams at six Peruvian sites dating from A.D. 1000 to the end of the Incas’ reign, the researchers identified 66 cases of trepanation. At pre-Inca sites, 5 to 8 percent of skulls displayed surgical openings. At Inca sites, 16 to 36 percent of skulls contained one or more trepanation holes.