Trepanation is a surgical procedure in which a hole is deliberately cut or drilled through the skull, exposing the membrane that covers the brain. It is the oldest known surgical practice in human history, with archaeological evidence stretching back at least 7,000 years. More than 1,500 trepanned skulls have been uncovered on every inhabited continent, from Europe and Scandinavia to China, Russia, and especially Peru.
How the Procedure Works
The basic mechanics of trepanation are straightforward: a surgeon removes a disc or section of bone from the skull without penetrating the brain tissue underneath. Ancient practitioners used several distinct techniques to accomplish this. Scraping involved slowly abrading the bone with a rough stone until it wore thin enough to break through. Grooving meant carving a circular channel deeper and deeper until a plug of bone could be lifted out. Cutting used sharp flint or obsidian blades to score intersecting lines, creating a rectangular or polygonal opening. Drilling, which became more common over time, used a pointed instrument rotated by hand or with a bow mechanism.
The 10th-century Arab surgeon al-Zahrawi refined the drilling approach, designing an instrument specifically calibrated not to penetrate the brain itself. That principle, protecting the delicate tissue beneath the bone, has remained the central challenge of the procedure across millennia.
Why Ancient Surgeons Did It
The reasons for trepanation appear to have been both medical and spiritual, and separating the two in prehistoric cultures is often impossible. Physical evidence on many skulls shows fracture lines radiating from the trepanation site, suggesting the operation was performed to treat traumatic head injuries, likely removing bone fragments pressing into the brain after a blow to the head. Other documented reasons include brain tumors, infections, and seizures.
A significant number of trepanned skulls show no signs of prior injury at all. Researchers believe these operations were ritual or spiritual in nature, intended to release evil spirits thought to be lodged in the brain, or to treat conditions like severe headaches and mental illness that ancient people attributed to supernatural causes. Between 5% and 10% of all Neolithic-era skulls found at certain sites have trepanation holes, some with multiple openings of various sizes, which suggests it was not a rare or desperate last resort but a relatively routine part of ancient medical practice.
Survival Rates Were Surprisingly High
Many trepanned skulls show clear evidence of bone healing around the edges of the hole, meaning the patient survived the operation and lived for weeks, months, or even years afterward. The most impressive survival data comes from the Inca Empire (roughly 1400 to 1500 AD), where studies of trepanned skulls found survival rates of 75% to 83%.
To put that in perspective, during the American Civil War roughly 400 years later, cranial surgery carried a mortality rate of 46% to 56%. Surgeons in 1860s field hospitals, working with metal instruments and some understanding of anatomy, lost patients at more than double the rate of Incan practitioners who used stone and bronze tools. The likely explanation is that Civil War surgeons operated on fresh battlefield wounds with contaminated instruments, while Incan surgeons had centuries of refined technique and may have selected patients more carefully. Still, the comparison illustrates that ancient trepanation was far from the crude butchery people often imagine.
What Happens Inside the Skull
Opening a hole in the skull has real physiological effects, some therapeutic and some harmful. The rigid bone encasing the brain normally maintains stable pressure inside the skull. When that enclosure is breached, the dynamics change. Brain structures can shift, fluid circulation is altered, and blood flow patterns through the brain are disrupted. The normal pulse-driven movement of cerebrospinal fluid, the liquid cushioning the brain, is dampened because the system loses its sealed pressure environment.
For someone with dangerous swelling or bleeding inside the skull, this pressure release can be lifesaving. That is exactly why modern neurosurgeons still drill into skulls today. But for a healthy person, losing that sealed environment impairs the brain’s normal fluid dynamics and can cause neurological problems over time.
The Modern Medical Version
Today’s direct descendant of trepanation is the burr hole procedure, performed by neurosurgeons for specific, well-defined medical emergencies. According to Johns Hopkins Medicine, the most common reasons include subdural hematomas (blood pooling between the brain and skull after a head injury), epidural hematomas, certain brain cancers, buildup of pus around the brain’s protective membranes, and hydrocephalus, a condition where cerebrospinal fluid accumulates and compresses brain tissue.
A modern craniotomy, the broader category of surgery that involves temporarily removing a section of skull, uses pneumatic or electric drills and saws. These are far more precise than ancient tools, but the fundamental concept is identical to what Neolithic surgeons were doing thousands of years ago: creating a controlled opening in the skull to access or relieve pressure on the brain beneath. The bone flap is typically replaced and secured with small plates and screws after the underlying problem is addressed.
The Self-Trepanation Movement
In the 1960s, a Dutch doctor named Bart Huges revived trepanation as a form of consciousness expansion. His theory held that when humans began walking upright, gravity drained blood away from the brain, reducing mental function. By opening a permanent hole in the skull, he argued, the heart could pump more blood through the head, restoring the heightened perception that infants supposedly enjoy before their skull bones fully fuse. Huges trepanned himself and brought his ideas to London in 1966, where he attracted a small but devoted following.
His most prominent converts were Joseph Mellen, a former athlete who used a hand-cranked trepanning instrument on himself after several failed and bloody attempts, and Amanda Feilding, who drilled through her own skull with a power drill. Feilding became the movement’s chief spokesperson and later ran for British Parliament on a platform that included making trepanation available through the national health service. Jenny Gathorne-Hardy, another member of this small circle, had her skull pierced with the help of Mellen and a friend, and reported feeling less anxious and more conscious afterward.
No scientific evidence supports the “brain blood volume” theory. The skull’s rigidity is essential to maintaining healthy intracranial pressure and fluid dynamics, and deliberately breaching it in a non-sterile environment outside a hospital risks infection and direct damage to the brain’s surface. Medical professionals consider voluntary trepanation dangerous and unsupported by evidence, regardless of the subjective well-being its practitioners report.