Trepanning, the act of cutting or drilling a hole through the human skull, never actually disappeared from medicine. While the word itself conjures images of Neolithic shamans and Bronze Age healers, the core procedure lives on in modern neurosurgery under names like burr hole trephination, craniotomy, and decompressive craniectomy. Tens of thousands of these procedures are performed every year in hospitals worldwide, using precision electric drills rather than sharpened stones, but the fundamental idea is the same one humans have practiced for at least 7,000 years.
What Ancient Trepanning Actually Looked Like
Archaeological evidence places trepanning among the oldest surgical procedures ever performed. Skulls with carefully cut openings have been found on every inhabited continent, with some of the richest evidence coming from prehistoric Peru, where researchers have analyzed more than 800 trepanned crania dating from roughly 400 BC through the Inca period around AD 1500.1World Neurosurgery. Trepanation Procedures/Outcomes: Comparison of Prehistoric Peru with Other Ancient, Medieval, and American Civil War Cranial Surgery Similar findings come from China, where trepanned skulls dating back 2,000 to 5,000 years consistently show signs of bone healing, meaning the patients survived long after surgery.2World Neurosurgery. Trepanation in Ancient China
The survival rates are what surprise most people. In the earliest Peruvian examples, from around 400–200 BC, long-term survival was roughly 40%. By the period between AD 1000 and 1400, that figure had climbed as high as 91%, suggesting that practitioners were refining their techniques over centuries.1World Neurosurgery. Trepanation Procedures/Outcomes: Comparison of Prehistoric Peru with Other Ancient, Medieval, and American Civil War Cranial Surgery Late Iron Age Switzerland tells a similar story, with about 78% of trepanned individuals surviving the operation.3International Journal of Paleopathology. Survival after trepanation—Early cranial surgery from Late Iron Age Switzerland These numbers are remarkable given that the surgeons had no antibiotics, no anesthesia, and were working with obsidian blades or hand-chiseled stone tools.
For context, cranial surgery during the American Civil War, performed by trained military physicians with metal instruments, carried a mortality rate of 46% to 56%.1World Neurosurgery. Trepanation Procedures/Outcomes: Comparison of Prehistoric Peru with Other Ancient, Medieval, and American Civil War Cranial Surgery The fact that Inca-era practitioners outperformed Civil War surgeons speaks partly to technique and partly to the fact that Civil War operations often addressed gunshot wounds, a category of injury far more destructive than what ancient trepanners typically faced. Still, the comparison underscores that drilling through the skull was never as uniformly fatal as popular imagination assumes.
How the Procedure Survived into Modern Neurosurgery
The principle behind trepanning is simple: when dangerous pressure builds inside the rigid container of the skull, creating an opening relieves it. That logic did not become obsolete with the arrival of modern medicine. It became better understood. Today, neurosurgeons open the skull for a range of life-threatening conditions, and the basic categories of skull-opening procedures map directly onto what ancient trepanners were doing, just with vastly better tools, imaging, and sterile technique.
The most common modern descendant of trepanning is burr hole trephination, in which one or two small holes are drilled through the skull. This became the preferred treatment for chronic subdural hematomas, a condition where blood slowly collects between the brain and its outer membrane, starting in the 1980s.4PubMed Central. How to Treat Chronic Subdural Hematoma? Past and Now The surgeon drills a small opening, inserts a drain, and allows the collected blood to flow out. Despite a meaningful complication rate, it remains the first-line surgical treatment for this condition.5Clinical Neurology and Neurosurgery. Risk factors for reoperation after initial burr hole trephination in chronic subdural hematomas Multicenter studies continue to track outcomes in hundreds of patients undergoing burr hole trephination, refining how surgeons manage complications like bleeding risk in elderly patients on blood thinners.6PubMed Central. Balancing Bleeding Risk and Thromboembolic Complications in Elderly Chronic Subdural Hematoma Patients Undergoing Burr Hole Trephination
Burr holes also serve as the entry point for external ventricular drains, which relieve pressure by channeling excess cerebrospinal fluid out of the brain’s ventricles. More than 50,000 of these drain procedures are performed annually in the United States alone, for conditions ranging from traumatic brain injuries to tumors and hemorrhagic strokes.7PubMed Central. Power Drill Craniostomy for Bedside Intracranial Access in Traumatic Brain Injury Patients Many of these happen at the bedside in intensive care units, not in full operating rooms, which gives a sense of how routine the procedure has become.
Decompressive Craniectomy, the Larger Cousin
When a small burr hole is not enough, surgeons sometimes remove a substantial portion of the skull entirely. Decompressive craniectomy involves taking out a wide section of bone so that swollen brain tissue can expand outward rather than being crushed against the inside of the skull. It has been used for years in patients with severe brain swelling from trauma, stroke, or infection, though its exact role in treatment remains debated among specialists.8Nature Reviews Neurology. Decompressive craniectomy: past, present and future
The clearest evidence for benefit comes from massive strokes. When a major artery supplying the brain becomes blocked, the resulting tissue death can cause such severe swelling that it threatens the entire brain. By removing part of the skull, surgeons allow the swollen tissue to shift outward instead of compressing healthy regions, and multiple studies have confirmed that the procedure reduces mortality in these patients.9Frontiers in Neurology. Role of Decompressive Craniectomy in Ischemic Stroke The tradeoff is that survivors may face significant disability, and the decision about whether and when to operate involves difficult conversations between surgeons and families. Still, for patients who would otherwise die from brain herniation, removing a piece of skull can be the only option.
There is an important distinction here between the ancient and the modern version. Ancient trepanners typically made small openings, probably for localized injuries or ritual purposes. Decompressive craniectomy removes a section of skull sometimes spanning a large part of one side of the head, creating a defect that later needs to be repaired with a separate surgery. The scale is different. The underlying logic of relieving intracranial pressure, however, is identical.
The Drills Have Changed Dramatically
One of the biggest differences between ancient and modern trepanning is the tooling. Ancient practitioners scraped, chiseled, or bored through bone using stone, obsidian, or later, metal implements. The margin for error was enormous, and punching through the skull into the delicate membrane covering the brain was a constant danger.
Modern neurosurgical drills have addressed this with autostop technology. A newer generation of electric cranial drills uses sensors to detect the moment the bit passes through bone and reaches the softer tissue beneath, automatically halting rotation before damaging the dura, the tough membrane that protects the brain. In one study, an electric drill with smart autostop engaged its safety mechanism in 100% of 174 craniotomies and prevented dural violation in all but one case.10PubMed Central. Safety Analysis of a New Portable Electrical Drill With a Smart Autostop Mechanism for Bedside Cranial Procedures By comparison, traditional hand-crank drills in a separate study resulted in significantly more dural violations, with 13 incidents versus just 2 for the electric autostop drill.11PubMed Central. Comparison of an Electrical Cranial Access Drill With Autostop Technology to a Traditional Hand Crank Cranial Access Drill
These advances matter especially for bedside procedures in emergency or military settings, where a non-neurosurgeon may need to drill a burr hole to save a life. The combination of CT-guided imaging and fail-safe drills has made the procedure far safer than it was even a generation ago, let alone in the Stone Age.
Emergency Trepanning in the Field
While hospitals with neurosurgeons and CT scanners handle the vast majority of skull-opening procedures, there are still situations where burr holes need to be drilled by general surgeons or even non-surgeons. In rural areas and combat zones, a patient with a rapidly expanding blood clot inside the skull may die before they can be transported to a neurosurgical facility. Military medical reviews have revisited the technique of emergency burr hole craniotomy for exactly this reason, noting that experiences in recent conflicts highlighted the continued need for non-neurosurgeons to be trained in the procedure.12Oxford Academic. Cranial Burr Holes and Emergency Craniotomy: Review of Indications and Technique
This scenario represents perhaps the closest modern parallel to ancient trepanning: a practitioner with limited resources and training, a patient with an acute head injury, and a drill as the only thing standing between life and death. The context is vanishingly rare in civilian peacetime medicine, but it has never gone away entirely.
Traditional Trepanning Outside Western Medicine
Modern hospital neurosurgery is not the only way trepanning persisted. In parts of the world, traditional forms of the procedure continued into the twentieth century and possibly beyond. Among the Kisii people of western Kenya, practitioners known as ababari emetwe (craniotomists) have performed traditional skull surgery using locally made instruments. Researchers documented the practice over a period of years through interviews with practitioners and their patients and through direct observation of operations.13PubMed. Traditional craniotomies of the Kisii tribe of Kenya
These traditional craniotomies were performed for headaches, head injuries, and other complaints. The existence of a recognized specialist role and an ongoing patient base suggests the practice was not purely historical or ceremonial but was seen as a working medical intervention within its cultural context. How widely it continues today is uncertain, but it demonstrates that trepanning’s survival into the modern era has not been limited to Western operating rooms.
When the Skull Stays Open Too Long
Removing a piece of skull saves lives, but leaving it off creates its own set of problems. After a decompressive craniectomy, patients live for weeks or months with a section of their skull missing, protected only by soft tissue. Over time, the scalp over the defect can sink inward, and a syndrome called “syndrome of the trephined” (also known as sinking skin flap syndrome) can develop. Symptoms range from cognitive decline and psychiatric changes to motor problems and altered consciousness.14Brain and Spine. Syndrome of the trephined: from pathophysiology to cranioplasty – an updated narrative review
The mechanism involves several factors working together: reduced blood flow to the brain in the area under the defect, disrupted flow of cerebrospinal fluid, and direct pressure from the atmosphere pushing on the unprotected brain surface. The condition is uncommon but serious enough that it has prompted extensive study into its management.15PubMed Central. Sinking Skin Flap Syndrome: Phenomenon of Neurological Deterioration after Decompressive Craniectomy The good news is that it is usually reversible. Once the skull is reconstructed, many patients improve substantially.
Putting the Skull Back Together
If trepanning has a complementary procedure in modern medicine, it is cranioplasty, the surgical reconstruction of skull defects. Skull defects arise from trauma, tumor removal, birth defects, and decompressive craniectomies, and the materials used to repair them have evolved considerably.16PubMed. Materials and techniques for osseous skull reconstruction
The simplest approach uses the patient’s own bone. When a section of skull is removed during a decompressive craniectomy, it is often stored frozen or implanted temporarily in the patient’s abdominal fat until swelling subsides and the bone can be replaced. But autologous bone does not always survive the reimplantation; it can be resorbed by the body over time. Alternatives include synthetic materials: acrylic (methyl methacrylate) remains the most widely used, while newer options like hydroxyapatite, which mimics a natural bone component, and polyetheretherketone (PEEK), a lightweight polymer that does not interfere with brain imaging, have expanded the toolkit.17World Neurosurgery. Cranioplasty: A Comprehensive Review of the History, Materials, Surgical Aspects, and Complications Three-dimensional printing now allows custom implants to be manufactured from a patient’s CT scan, producing a precise fit that older hand-shaped materials could not match.
The fact that cranioplasty has become its own subspecialty within neurosurgery tells you something about how often the skull is opened in modern practice. You do not develop an entire field around rebuilding skulls unless skull openings are happening at a meaningful scale.
The Self-Trepanation Fringe
No discussion of trepanning’s modern existence would be complete without mentioning the small but real phenomenon of people drilling holes in their own skulls. Starting in the 1960s, a handful of advocates promoted voluntary trepanation as a way to achieve a permanent “high” by increasing blood flow to the brain. The most famous proponent, a Dutch librarian named Bart Huges, drilled his own skull with a dentist’s hand drill in 1965, claiming it expanded his consciousness. A few followers did the same over subsequent decades, and the idea has never fully died out on the fringes of alternative health culture.
There is no credible evidence that self-trepanation produces the claimed cognitive or psychological benefits. What it does produce, reliably, is risk. Clinical case reports describe patients with repetitive self-induced destruction of the scalp and skull who penetrate into the intracranial compartment, frequently developing infections or direct brain injury that leads to serious neurological harm or death. Psychiatric conditions are common in these cases, and treatment failures are frequent because of poor adherence to follow-up care.18PubMed Central. Self-Trephination in Cranial Excoriation Disorder
The gulf between controlled neurosurgical trephination and self-trepanation could not be wider. One is performed in sterile conditions by trained professionals using precision instruments, guided by imaging, with the specific goal of addressing a diagnosed condition. The other involves a person with no medical training breaching the most critical protective structure in their body. The same word covers both, but they share about as much in common as a kitchen knife and a scalpel.
Forensic Traces of Old Burr Holes
An unexpected consequence of modern trepanning’s prevalence is that old surgical burr holes sometimes complicate forensic investigations. Burr holes remain visible in the skull for life, and when a person who previously underwent neurosurgery dies from head trauma, the old holes can interact with fracture patterns in ways that confuse analysis. In two documented cases, fracture lines from blunt force trauma and gunshot wounds encountered burr holes left by surgeries performed 15 and 20 years before death. Rather than stopping at the edge of the hole as classical fracture rules would predict, the fracture lines appeared to “skip” the hole and continue on the opposite side in the same direction.19PubMed Central / Springer Nature. Two peculiar cases of cranial fractures running through craniotomy burr holes: may this be a kind of “exception” to the Puppe rule
This finding matters for forensic pathologists trying to determine what happened in a death involving head injury. Long-established rules about how fracture lines behave when they meet existing breaks in the skull may not apply when the existing break is a smooth, healed surgical burr hole. As neurosurgical procedures become more common and patients live longer afterward, forensic specialists will increasingly encounter skulls bearing evidence of prior trepanning, and they will need to account for these anomalies when reconstructing the events of a death.