Prehistoric Inca neurosurgery


The procedure known as trepanation, in which a hole is scraped or drilled in the skull, is an ancient form of neurosurgery that has been performed since the late Stone Age. Exactly why ancient peoples performed trepanation has remained a matter of debate: some researchers argue that it was performed for medical reasons, as it is today, while others believe it was done for magical or religious reasons.

A new study by two American anthropologists now provides evidence that the Incas performed trepanation to treat head injuries; that the procedure was far more common than was previously thought; and that the Incan practitioners of trepanation were highly skilled surgeons with a detailed knowledge of the anatomy of the skull.

Valerie Andrushko, of Southern Connecticut State University in New Haven, and John Verano, of Tulane University in New Orleans, examined a total of 411 skulls excavated from 11 burial sites in the prehispanic Inca capital of Cuzco in the southern highlands of Peru, where the first trepanned skull specimen was found by E. George Squier in 1865.

Of these 411 skulls, 66 exhibited perforations of varying shape and size. More than half were circular, but some were oval or irregularly circular, and one (above) was rectangular. The diameters of the circular holes ranged from approximately 0.3 - 7.3 cm. In all, 109 holes were observed in the 66 skulls, and there was one individual with 7 trepanations.

Andrushko and Verano argue that the Incas performed trepanation primarily to treat head injuries incurred during battle, because the holes are most often found at the front of the skull to the left, consistent with injuries caused by a right-handed opponent during face-to-face combat, and because adult males are overrepresented in the sample. The procedure was evidently used to treat mastoiditis (an infection of the region of the temporal bone behind the ear) as well.

The authors also show that the success rate of the procedure improved with time, as the Inca empire progressed and made advances in medicine. The earliest specimens, dated to around 1,000 A.D., showed no signs of bone growth around the perforations, suggesting that the procedure was often fatal. But specimens dating to around 400 years later suggest a survival rate of around 90%.

By that time, the procedure appears to have been stabdardized, as its practitioners operated only on certain parts of the skull, and avoided other areas, which were likely to result in damage to the meninges (the thick membranes which envelop the brain and spinal cord) or the blood vessels found within the layers of the outer membrane. 

The later specimens suggest that there was a very low frequency of infection, and lead author Andrushko says that balsam, and plants containing compounds called saponins, which have soap-like properties and are antiseptic, may have been used to reduce the risk of infection, and that coca, wild tobacco and maize beer may have been used to alleviate the pain.

Thus, this new study provides strong evidence that the Incas performed trepanation for specific medical conditions, and may finally settle the debate about why people in ancient civilizations performed trepanation. It also suggests that the Incas were highly skilled surgeons with a detailed knowledge of cranial anatomy and an awareness of the medicinal properties of various species of wild plants.


Andrushko, V. A. & Verano, J. W. Prehistoric trepanation in the Cuzco region of Peru: A view into an ancient Andean practice. Am. J. Phys. Anthropol. doi: 10.1002/ajpa.20836 [Abstract]

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Thanks for the continuing coverage of material on the history of neurosurgery and neuroanatomy, Mo. I've been fascinated by this stuff for years -- I wrote a lengthy paper on "The Evolution and Development of Neurological Surgery" for honors work in my senior year in high school, back in 1958. Inca trepanations were a part of that paper, and I seem to remember illustrations of multiple skulls with rectangular trepanations from studies I read for that paper.

Another note on possible Inca herbal medicine is that, besides its local anesthetic properties, coca is also a peripheral vasoconstrictor, and thus could have also helped reduce mortality from blood loss from the highly vascular scalp.

BTW, a quote from Shakespeare's MacBeth that I used in that paper might also be appropriate here at Neurophilosophy.
"There was a time that when the brains were out, the man would die, but now they rise again."

Fascinating. Is there any information on the types of tools they may have used to perform the surgery? I didn't think the Inca had any iron tools or weapons in that period, and yet they had something strong and sharp enough to create a clean line through the skull.

Thanks for these posts! I love reading this kind of information!

Aztecs used obsidian as the weapon/utensil of choice for anything that needed to be cut. Maybe Incas used it too. Archeologists have found obsidian weaponry that's as sharp as a Katana sword.

By Alejandro Lobo… (not verified) on 14 May 2008 #permalink

"It also suggests that the Incas were highly skilled surgeons with a detailed knowledge of cranial anatomy"

... right, after 400 years of killing their patients, I would hope so!

I'm always fascinated by reports on this topic because trepanation is such a potentially dangerous task. It would be so easy to do permanent damage to the brain, or even kill the patient. Yet it is something that has such antiquity.

I own a website on the 1954 Charlton Heston movie SECRET OF THE INCAS. Recently we were discussing a scene in the film in which the curator of the Archeaological Museum was showing the tourists Inca exhibits. Pointing to some bronze knives he tells the group that two Peruvian surgeons recently performed a skull surgery operation using the same ancient Inca knives. What I would like to know, did this really happen in Peru in the early 1950's?

In Hungary are lot of trepanations, the last was 1230 (about), but the churchprohibition it.