What Happens When Someone Gets Shot in the Head?

A gunshot wound to the head sets off a cascade of destruction that begins in milliseconds and can continue for days or weeks afterward. Roughly 55% of civilians with penetrating brain injury arrive at the hospital with severe traumatic brain injury, and overall mortality exceeds 40%.¹ The outcome depends on a web of factors, from the type of weapon and the bullet’s path through the skull to how quickly the person reaches a trauma center, and the biology involved is more complex than most people assume.

How a Bullet Damages the Brain

When a bullet enters the skull, it inflicts damage through two distinct mechanisms. The first is the permanent wound track, a channel of crushed and destroyed tissue carved directly by the projectile’s path. In most parts of the body, this crushing is the main source of injury. But the brain is different, and the second mechanism matters enormously here: temporary cavitation.²

As a bullet travels through tissue, it pushes material radially outward, creating a pulsating cavity that expands and collapses rapidly along the bullet’s path.³ In muscle or fat, which are relatively elastic, the tissue can stretch and spring back with limited extra damage. Brain tissue is not elastic. It tears, shears, and compresses under those same forces, and the resulting destruction extends well beyond the bullet’s actual path.

The skull makes everything worse. In a limb, the temporary cavity can push outward into open space. Inside the skull, the rigid bone walls contain that expanding pressure, amplifying it. The result is massively elevated intracranial pressure, an enlarged zone of destroyed tissue, and secondary missile fragments as the bullet breaks apart or sends bone shards deeper into the brain.² Bullets also tend to deform and tumble after hitting bone, which makes their path through the brain less predictable and the damage less confined than you might expect from a small entry wound.

Why Some People Survive and Others Do Not

The single most important factor in whether someone lives or dies is the bullet’s trajectory through the brain. A wound that crosses the midline and damages both hemispheres carries a far higher mortality rate than one confined to a single hemisphere. Injuries that involve the posterior fossa, the area at the base of the skull housing the brainstem and cerebellum, are especially deadly.⁴ One notable exception: wounds that cross both frontal lobes actually carry a somewhat better prognosis than other bihemispheric trajectories, likely because the brainstem and the brain’s deepest structures remain intact.⁵

At the bedside, two indicators give trauma teams the most information in the first minutes. Pupillary response, whether the pupils react to light, and the Glasgow Coma Scale score, a standardized assessment of consciousness, are consistently the strongest predictors of outcome across multiple studies.⁶ Patients who arrive with reactive pupils and a GCS score above 8, along with damage limited to a single brain lobe, are the group most likely to benefit from aggressive surgical treatment.⁶ When both pupils are fixed and the GCS is 3 or 4, mortality approaches near-certainty regardless of intervention.

Other factors associated with death include cerebral herniation (when swelling forces brain tissue downward through the skull’s openings), bleeding inside the brain’s ventricles, intracranial pressure above 20 mm Hg, and age over 35.⁴⁷

The type of weapon matters, too, though in a less intuitive way. Case reviews of people who survived long enough to act after being shot in the head found that more than 70% had been hit by small, slow-moving bullets, typically from .22 caliber or 6.35 mm handguns. Higher-powered weapons like center-fire rifles or close-range shotguns were never represented in those survival cases.⁸ A low-energy projectile can still kill, but it leaves a wider window in which the brain’s vital structures might be spared.

What Happens in the Hours After

The initial bullet damage is only the first wave. In the hours and days that follow, secondary brain injury mechanisms take over. The brain swells, blood supply to surrounding tissue gets cut off, and intracranial pressure climbs.⁹ This secondary damage can destroy brain tissue that initially survived the bullet itself, which is why rapid treatment focuses heavily on preventing these cascading effects.

Emergency management follows the same general principles used for severe closed-head injuries, with some specific additions. Trauma teams prioritize stabilizing blood pressure, correcting any clotting problems caused by massive tissue injury, and getting a brain CT scan as quickly as possible. If intracranial pressure is dangerously elevated, treatments include medications to draw fluid out of the brain, draining cerebrospinal fluid, and in some cases surgical removal of a section of skull to give the swelling brain room to expand outward rather than downward into the brainstem.¹⁰

Surgery for the wound itself aims at controlling bleeding, removing dead or contaminated tissue, and sealing the protective membranes around the brain to reduce infection risk.¹¹ Bullet fragments, bone shards, hair, and skin can all be driven deep into the brain, creating a contaminated wound in an organ that normally exists in a sterile, sealed environment. Surgeons walk a careful line between removing dangerous debris and avoiding further damage to viable brain tissue during the operation.

For patients who arrive in cardiac arrest, the numbers are stark. A recent multicenter study found a survival rate of just 2.1% among gunshot-to-the-head patients who required CPR, though roughly three-quarters of that small group of survivors were eventually discharged to rehabilitation or home. The same study found that about 10% of those patients became organ donors.¹

Vascular Damage That Shows Up Later

One of the more dangerous delayed complications is the formation of traumatic intracranial aneurysms, weak spots on damaged blood vessels that can balloon out and rupture. These are rare in the broader population of aneurysm patients, but gunshot wounds are one of the most common causes of the specific type called pseudoaneurysms, which form when the vessel wall is torn and a blood-filled sac develops outside the artery.¹²

When researchers used early CT angiography to screen gunshot wound survivors, they found traumatic aneurysms at rates roughly ten times higher than previously reported in the literature, suggesting many had been going undetected. In one study that systematically screened for these, about 30% of the aneurysms that were found resolved on their own within a week, while others required treatment by threading tiny catheters through blood vessels to seal them off.¹³ The presence of a large blood clot in the brain tissue was the strongest predictor that a hidden aneurysm was lurking nearby, a finding that is changing how aggressively doctors screen for vascular damage in these patients.¹³

Other vascular injuries found in gunshot wound survivors include vessel dissections (where the inner lining of an artery tears and blood flows between the wall layers), complete vessel occlusions, and abnormal connections between arteries and veins. In one series of 45 patients who underwent vascular imaging, 22 injuries of these types were identified.¹⁴

Cerebrospinal Fluid Leaks and Infection

When a bullet breaches the skull and the membranes lining the brain, it can create pathways for cerebrospinal fluid to leak out through the nose, ears, or the wound itself. This is more than an inconvenience. A CSF leak is essentially an open channel between the brain and the outside world, and the primary fear is bacterial meningitis. The generally accepted rate of meningitis with an untreated CSF leak is about 10%, but timing matters enormously: leaks that persist beyond a week carry an 88% risk of meningitis, compared to 11% for those that seal within the first seven days.¹⁵ Roughly 35% of patients who develop recurrent meningitis have underlying CSF leaks from old trauma.¹⁵ These leaks can sometimes be repaired with minimally invasive endoscopic techniques, but they remain a serious concern for years after the original injury.

Personality and Cognitive Changes in Survivors

Survivors of gunshot wounds to the head frequently face dramatic changes in personality, cognition, and emotional regulation that depend on which parts of the brain were damaged. The frontal lobes, which sit just behind the forehead, are involved in impulse control, planning, social behavior, and emotional tone, and they are disproportionately affected in many gunshot injuries due to their forward position in the skull.

Some of the resulting changes are deeply strange and illustrate just how much personality is rooted in brain structure. In one documented case, a man with extensive damage to his right frontal lobe and parts of the left frontal region after a gunshot wound developed a dramatically different personality: he became persistently cheerful, light-hearted, and fond of jokes and puns. Before the injury, he had suffered from chronic depression and suicidal thoughts, both of which resolved completely. Testing showed that his ability to understand humor and recognize facial emotions was excellent, even as memory and other executive functions were impaired.¹⁶ Researchers interpreted this as the loss of frontal tissue “releasing” deeper brain reward circuits from their normal regulation, a mechanism that echoes findings from the era of frontal lobotomies.

That connection is not just metaphorical. In another case report, a patient with self-inflicted gunshot damage to the frontal lobes showed a pattern of deficits that closely resembled those seen in patients who underwent frontal leukotomy, the surgical procedure popularized in the mid-twentieth century. Language assessments revealed a specific type of speech difficulty linked to frontal damage, alongside broader changes in behavior and executive function.¹⁷ These cases are individual stories, not population-level findings, but they reveal how profoundly a bullet’s path through particular brain regions can reshape who a person is.

Children Are Not Small Adults

Pediatric gunshot wounds to the head present their own set of challenges. Children’s skulls are thinner, their brains are still developing, and the clinical scoring systems designed for adults do not always perform as expected. The outcomes reported in the pediatric literature vary widely depending on the population studied. One institutional review of surgical pediatric patients found that about 23% died, another 23% had severe disability, and roughly 54% achieved a favorable outcome.¹⁸ A different series from a single urban trauma center reported a 65% overall mortality rate.¹⁹

The wide gap between those numbers likely reflects differences in which children were included. The first study focused on patients who made it to surgery, filtering out those who died before reaching the operating room, while the second captured all intracranial gunshot cases. In both studies, the same prognostic factors that predict death in adults, particularly low consciousness scores at admission and wounds that cross the midline, held true in children as well.¹⁸¹⁹ Survivors in the higher-mortality series had markedly better initial consciousness scores (an average GCS of 11 versus 4 in those who died) and better laboratory markers, underscoring that the initial exam remains the most useful prognostic tool even in younger patients.

Retained Bullet Fragments and the MRI Problem

Many gunshot wound survivors carry metal fragments in their heads permanently. Surgeons often leave deeply embedded fragments in place because the act of removing them would cause more damage than leaving them where they are. This creates a long-term practical problem: MRI machines use powerful magnets, and ferromagnetic metal fragments can potentially heat up, move, or distort the images.

The fear of MRI in patients with retained bullets has historically been so strong that many are simply denied the scan altogether, even when they need it for unrelated medical problems years later. A recent large study from an urban health system examined what actually happened when 220 patients with retained bullet or shrapnel fragments underwent MRI. Four patients, about 1.8%, reported temporary localized burning or discomfort during the scan. In each case, the fragments were in superficial soft tissue rather than deep in the brain. No serious adverse events occurred, and no one required medical treatment.²⁰ Those findings are pushing the field toward a more nuanced approach to MRI screening in this population, rather than a blanket refusal.

How Forensic Examiners Read the Skull

For forensic pathologists and medical examiners, a gunshot wound to the skull tells a detailed story. Entrance wounds typically produce internal beveling, where the bone chips inward like a cone, while exit wounds show external beveling, with the cone flaring outward. This pattern allows examiners to determine bullet direction even when soft tissue evidence is degraded.²¹

But the pattern is not always straightforward. Keyhole-shaped defects form when a bullet strikes the skull at a shallow angle, creating a wound that shows beveling characteristics of both entry and exit in the same hole. Other features forensic examiners document include radiating fractures that extend outward from the wound, concentric fractures that circle around it, bone plugs driven inward, and the distribution of bullet fragments and gunpowder residue.²² Cases exist where an exit wound produces internal beveling that mimics an entrance wound, which can lead to confusion about bullet direction if examiners rely on a single feature rather than the full pattern.²¹

What Helmets Can and Cannot Do

Ballistic helmets are designed to prevent exactly this kind of injury, and modern materials have made them remarkably effective against many threats. But stopping a bullet does not eliminate the danger entirely. When a projectile strikes a helmet and is caught, the kinetic energy still has to go somewhere. It transfers into the helmet material, deforming it inward in what engineers call back face deformation. If the dent is deep enough to strike the wearer’s skull, the result is behind-armor blunt trauma, a closed-head injury caused not by penetration but by the helmet itself being pushed into the head.²³ Modern helmet standards set limits on how much inward deformation is acceptable, but the physics are inescapable: absorbing a high-energy impact in a confined space always involves tradeoffs between weight, coverage area, and how much force reaches the head.

Helmet design also reflects real-world threat profiles. Military research during the wars in Iraq and Afghanistan found that blast injury from improvised explosive devices, not bullets, was the most common cause of brain injury among service members. The resulting mild traumatic brain injuries were often initially unrecognized and eventually became known as the signature wound of those conflicts.²⁴ This shifted helmet development priorities toward blast mitigation alongside traditional ballistic protection, a dual mandate that continues to shape design today.

Animal Models and the Limits of What We Know

Much of what researchers understand about the biological cascade following a penetrating brain injury comes from controlled experiments in animal models. A rat model developed specifically to replicate features of ballistic brain injury has become a standard tool for studying the progression of damage, testing potential treatments, and understanding which secondary injury mechanisms might be modifiable.²⁵ The model can be scaled by injury severity, which allows researchers to study everything from mild to fatal injuries in a reproducible way.

The obvious limitation is that a rat’s brain is orders of magnitude smaller than a human’s, and the skull geometry is completely different. The confined-space amplification effect that makes human cranial gunshot wounds so devastating simply cannot be replicated at that scale. This is one reason the field still relies heavily on clinical case series and trauma registries rather than laboratory findings to guide treatment decisions. For the survivors who make it through the acute phase, rehabilitation is a long, unpredictable process shaped as much by which specific brain regions were damaged as by the severity of the injury on paper.