A hematoma on the brain is a collection of blood that forms inside the skull, putting pressure on brain tissue. It typically results from a head injury that ruptures blood vessels, though it can also develop without trauma. Depending on where the blood pools, the condition ranges from a slow-building problem that develops over weeks to a life-threatening emergency that requires surgery within hours.
Three Types Based on Location
The brain sits inside a layered system of protective membranes, and the specific layer where blood collects determines the type of hematoma and how it behaves.
- Epidural hematoma: Blood collects between the skull and the outermost protective membrane (the dura mater). This usually involves an artery, so blood accumulates fast and pressure builds rapidly. It’s the least common of the three types but often the most urgent.
- Subdural hematoma: Blood pools between the dura mater and the brain surface. These involve veins, which bleed more slowly than arteries, so symptoms can develop gradually. Subdural hematomas are the most common type after a head injury.
- Intracerebral hematoma: Blood collects within the brain tissue itself. This can result from trauma or from conditions like uncontrolled high blood pressure that cause a blood vessel inside the brain to burst.
How Subdural Hematomas Progress
Subdural hematomas are classified by how quickly they develop, which matters because the timeline shapes both symptoms and treatment urgency. An acute subdural hematoma forms within 72 hours of injury and is a medical emergency. The subacute phase begins around three to seven days after the initial injury. Chronic subdural hematomas develop over the course of weeks, sometimes so slowly that the original head injury was minor enough to be forgotten entirely.
Chronic subdural hematomas are particularly common in older adults. The brain shrinks slightly with age, which stretches the small veins bridging the brain surface to the outer membrane. Even a mild bump can tear one of those veins, and because the bleeding is slow, weeks may pass before enough blood accumulates to cause noticeable symptoms. To complicate things further, fresh bleeding can occur into an existing chronic hematoma, creating a mixed-type injury that may suddenly worsen.
Common Causes and Risk Factors
Head trauma is the leading cause. Falls, car accidents, sports injuries, and any blow to the head can rupture blood vessels inside the skull. Epidural hematomas often follow a fracture of the temporal bone on the side of the skull, which damages the artery running along that area. Subdural hematomas more commonly result from sudden acceleration or deceleration forces, the kind that happen in car crashes or falls, where the brain shifts inside the skull and tears bridging veins.
Not all brain hematomas start with an injury. Intracerebral hematomas frequently develop in people with long-standing high blood pressure, which weakens small blood vessels deep in the brain until one eventually ruptures. Blood-thinning medications, including warfarin and newer anticoagulants, significantly raise the risk of all types of brain hematomas and make any bleeding harder to stop. Heavy alcohol use is another major factor because it both increases the likelihood of falls and impairs the blood’s ability to clot. Age alone is an independent risk factor: the brain’s protective veins become more fragile over time.
Symptoms and Warning Signs
Symptoms depend on how quickly blood is accumulating and where in the skull the pressure is building. A rapidly expanding epidural hematoma can cause a distinctive pattern: someone is knocked unconscious by a head injury, wakes up and seems fine for a period of minutes to hours, then suddenly deteriorates. This “lucid interval” is one of the most dangerous patterns in head trauma because it creates a false sense that the person is okay.
More broadly, brain hematomas produce symptoms by compressing brain tissue. These include a worsening headache that doesn’t respond to typical pain relief, nausea and vomiting, increasing drowsiness or difficulty staying awake, confusion or slurred speech, weakness on one side of the body, and unequal pupil sizes. Seizures can occur with any type. In chronic subdural hematomas, symptoms may be subtle for weeks: mild confusion, memory problems, unsteadiness, or personality changes that family members might initially attribute to aging or dementia.
How It’s Diagnosed
A CT scan is the standard first-line imaging test for a suspected brain hematoma. It’s fast, widely available, and reliably identifies acute bleeding inside the skull. Fresh blood appears bright white on a CT scan, making it easy to spot. As a hematoma ages over days and weeks, its appearance changes, which helps doctors estimate when the bleeding started.
MRI provides more detailed images and is better at detecting very small bleeds or older hematomas that have become harder to distinguish on CT. However, MRI takes longer and isn’t always practical in an emergency. In most cases, a CT scan within minutes of arrival at the emergency department is what drives the initial treatment decision.
Surgical Treatment Options
Many brain hematomas require surgery to remove the collected blood and relieve pressure. The type of surgery depends on the size and consistency of the hematoma.
A burr hole procedure is the least invasive option. A neurosurgeon drills one or two small holes through the skull, allowing liquid blood to drain out. This works well for chronic subdural hematomas, where the blood has liquefied over time, and for some acute hematomas caught early. Recovery from a burr hole procedure tends to be faster and carries fewer complications than more extensive surgeries.
A craniotomy involves removing a larger section of skull bone to access and remove the hematoma directly. This is necessary when the blood has formed a solid clot that won’t drain through a small hole, or when the hematoma is especially large. The bone is replaced after the clot is removed. In the most severe cases, particularly when the brain is dangerously swollen, a decompressive craniectomy may be performed, where the bone is intentionally left off to give the swollen brain room to expand. The bone is stored and replaced in a later surgery once swelling resolves. Both craniotomy and craniectomy carry a higher rate of complications than a burr hole procedure.
Not every hematoma needs surgery. Small hematomas that aren’t causing significant pressure may be monitored with repeat CT scans while the body gradually reabsorbs the blood.
Managing Blood Thinners During a Brain Bleed
For people who are on blood-thinning medication when a brain hematoma develops, reversing the anticoagulant effect becomes an urgent priority. The faster clotting ability is restored, the less the hematoma expands. Research published by the American Heart Association found that reversing warfarin’s effects within four hours, combined with blood pressure control, significantly reduced hematoma growth and lowered in-hospital mortality.
Different blood thinners require different reversal strategies. Warfarin is reversed most effectively with a concentrated clotting factor product rather than plasma transfusion. One clinical trial showed that 67% of patients treated with this concentrated product achieved adequate clotting within three hours, compared to only 9% of those who received plasma. Newer blood thinners each have their own specific reversal agents. Doctors prioritize starting reversal treatment immediately rather than waiting for lab results to confirm the drug’s effect.
Survival Rates Vary Widely
Outcomes depend heavily on the type of hematoma, how quickly it’s treated, and the person’s overall condition at the time. Epidural hematomas generally have the best prognosis. Large studies put the mortality rate around 3.6%, and favorable outcomes (where patients return to a good level of function) occur in roughly 84% of cases. However, outcomes worsen dramatically when the hematoma has caused both pupils to become fixed and dilated, a sign of severe brain compression, pushing mortality to nearly 30%.
Subdural hematomas carry a more sobering outlook. Surgical mortality ranges from about 12% to as high as 67% depending on the study and patient population, with an average around 38%. Only about a third of surgical patients achieve a favorable functional outcome. Older adults fare worse, with surgical mortality averaging 36%. The key difference is timing: epidural hematomas are often caught early because symptoms escalate quickly, while subdural hematomas, especially chronic ones, may not be diagnosed until significant brain damage has already occurred.
What Recovery Looks Like
Recovery from a brain hematoma depends on how much damage the brain sustained before pressure was relieved. For small hematomas treated quickly, some people recover fully within weeks. For larger hematomas that caused significant compression, recovery follows a longer and less predictable path.
The fastest improvement typically happens in the first six months. During this period, both thinking and physical abilities tend to show the most gains. After that, progress slows but can continue for years. Early recovery often involves a confusional state where the person has difficulty paying attention, forming new memories, and controlling emotions. Agitation, restlessness, and frustration are common during this phase and gradually improve as the brain heals.
The progression generally moves through recognizable stages: from unconsciousness to a minimally conscious state where the person can intermittently follow commands or respond to family members, to a point where they can reliably answer simple questions and use everyday objects correctly. Rehabilitation during this period focuses on rebuilding cognitive skills, physical strength, and daily functioning. Seizures are a known long-term complication, and some people require anti-seizure medication for months or longer after the initial injury.