It’s easy to think that brain surgery is a relatively modern phenomenon. But the archaeological record shows that humans have been cracking open one another’s heads for thousands of years through the practice of trepanation. Signs of the procedure, which usually involves chiseling an opening in a living someone’s head, have been found across North and South America, Polynesia, Ancient Greece, the Far East, Russia and Africa, with varying results. Now, a new study compares the highly developed Inca tradition of trepanation with cranial surgery performed during the American Civil War: it finds that survival rates among later Inca cultures was significantly higher than those for 19th-century soldiers, reports Lizzie Wade at Science.
For the study, Tulane University bioarchaeologist John Verano, who literally wrote the book on Inca cranial surgery, and bioarchaeologist Anne Titelbaum of the University of Arizona teamed up with University of Miami neurologist David Kushner to look at surgery success rates over time. With its high elevation and dry climate, Peru is full of well-preserved ancient skulls. In fact, according to a press release, about 800 trepanned prehistoric skulls have been found in Peru, more than the rest of the world combined. The researchers examined the skulls, looking at the edges of the hole. If the edge had been “remodeled,” or healed significantly, the team considered the surgery a success. If the edge of the hole was ragged without signs of healing, they assumed the patient didn’t survive the surgery or died soon after.
Using that metric, they examined various periods of Peruvian trepanation. Wade reports that over the course of 2,000 years, the Inca and their ancestors got progressively better at skull surgery. Of the 59 skulls dated between 400 B.C.E. to 200 B.C.E. only about 40 percent of the patients’ skulls showed signs of survival. That rate of survival increased to 53 percent in the analysis of 421 skulls found dating between 1000 C.E. to 1400 C.E. During the Inca period, from 1400 C.E. to 1500 C.E. 75 percent to 83 percent of the 160 skulls examined showed signs of survival.
During the Civil War, by comparison, the mortality rate from skull surgery was between 46 and 56 percent. The study appears in the journal World Neurosurgery.
“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 says in the release. “The question is how did the ancient Peruvian surgeons have outcomes that far surpassed those of surgeons during the American Civil War?”
Kushner says there are signs that the technique evolved over the centuries. The succession of skulls shows that over time the Peruvian surgeons learned to avoid areas of the skull that would produce excessive bleeding. The also figured out that smaller holes were more survivable than larger holes. And most importantly, it appears their surgeries became shallower, avoiding perforating the dura, or the thick membrane that covers the brain. In fact, some patients appear to have survived multiple surgeries, with one skull showing five trepanation holes.
So what explains the Inca’s success compared to the “modern” medicine practiced during the Civil War? Most surgeries during the Civil War were plagued by infection. Doctors would not sterilize tools and often poked their dirty fingers into bullet wound and skull fractures to dig out lead and bone fragments. The Inca, on the other hand seemed to understand infection or used methods that controlled it. “We do not know how the ancient Peruvians prevented infection, but it seems that they did a good job of it. 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,” Kushner says in the release. “Maybe there was something else, maybe a fermented beverage. There are no written records, so we just don't know.”
In some ways, comparing battlefield surgery to what the Inca were doing is unfair. Researchers still aren’t sure why ancient peoples practiced trepanation. It could have been to relieve swelling on the brain, to cure ailments like epilepsy, a way to heal battle wounds or could have been part of a ritual to let evil spirits out. What we do know is that it wasn’t practiced to remove bullets, pieces of cannon shot or other trauma caused by industrial-age war.
“The trauma that occurs during a modern civil war is very different from the kind of trauma that would have been happening at the time of the Incas,” Boston University neurosurgeon and trepanation researcher Emanuela Binello tells Wade. Civil War surgeons were facing traumatic wounds and operating on dozens of patients in filthy battlefield hospitals during chaotic conditions. That however, doesn’t take away from the amazing surgical achievements of the Inca.