Ancient cranial surgeons in pre-Columbian Peru had an 80 percent success rate for operations performed during the Inca era, stunningly high compared to a 50 percent rate 400 years later during the American Civil War, a study in Science magazine reported.
David Kushner, a neurologist at the University of Miami, directed the study that examined the skulls of hundreds of people to come up with the analysis of success rate across different cultures and time periods for trepanation – drilling or scraping a hole of the human skull.
Kushner was joined John Verano, a bioarchaeologist at Tulane University, and Anne Titelbaum, a bioarchaeologist at the University of Arizona, in the study.
Researchers looked at 59 skulls from Peru's southern coast dated to between 400 BC to 200 B.C. and from Peru's central highlands dated from 1000 to 1400, and 160 from the highlands around Cusco, capital of the Inca Empire, from the early 1400s to the mid-1500s, Science said.
If the bone around the surgical hole showed no signs of healing, researchers knew the patient died either during or very shortly after the surgery. Smooth bone around the opening showed that the patient had survived for months or years after the procedure.
"There are still many unknowns about the procedure and the individuals on whom trepanation was performed, but the outcomes during the Civil War were dismal compared to Incan times," Kushner said.
"In Incan times, the mortality rate was between 17 and 25 percent, and during the Civil War, it was between 46 and 56 percent. That's a big difference. The question is how did the ancient Peruvian surgeons have outcomes that far surpassed those of surgeons during the American Civil War?"
Different research, published this month in the journal World Neurosurgery, suggested that lack of hygiene during the Civil War era may have led to poor results. Physicians used unsterilized medical tools and their bare fingers to probe open cranial wounds or to break up blood clots.
"We do not know how the ancient Peruvians prevented infection, but it seems that they did a good job of it," Kushner said. "Neither do we know what they used as anesthesia, but since there were so many (cranial surgeries) they must have used something – possibly coca leaves. Maybe there was something else, maybe a fermented beverage. There are no written records, so we just don't know."
Researchers said the ancient Peruvians appeared to have had plenty of practice because there were more than 800 prehistoric skulls with evidence of trepanation, and they appeared to refine their surgeries over time
The survival rates from "shallow surgeries" in Peru during early years, from about 400 to 200 B.C., proved to be worse than those in the Civil War, when about half the patients died.
But from 1000 to 1400 A.D., survival rates improved dramatically, to as high as 91 percent in some samples, to an average of 75 to 83 percent during the Incan period, the study showed.