A brain hematoma is a collection of blood that pools inside the skull, either between the brain and its protective layers or within the brain tissue itself. The bleeding creates pressure that can damage brain cells and, depending on the size and location, become life-threatening. Brain hematomas fall into three main types based on where the blood collects, and each behaves differently in terms of symptoms, urgency, and treatment.
Three Types of Brain Hematoma
The brain sits inside multiple protective layers within the skull. Blood can collect in different spaces between those layers, or inside the brain itself, and the location determines what kind of hematoma it is.
Epidural hematoma forms between the skull and the outermost protective layer (the dura). The most commonly damaged vessel is an artery running along the side of the skull in the temple region. Because arterial blood is under high pressure, these hematomas can expand quickly and become emergencies within hours.
Subdural hematoma forms just beneath the dura, in the space between the brain’s outer covering and the brain surface. Head trauma causes the brain to shift inside the skull, stretching and tearing small veins that bridge the gap between the brain and skull. Because veins bleed more slowly than arteries, subdural hematomas can develop over days or even weeks. Chronic subdural hematomas are particularly common in older adults, who have more space around a naturally shrinking brain for blood to accumulate.
Intracerebral hematoma is bleeding directly into the brain tissue. The most common location is a deep structure called the putamen, and the most common cause is long-standing high blood pressure that weakens small blood vessels until they rupture.
Common Causes and Risk Factors
Head trauma is the leading cause of epidural and subdural hematomas. Falls, car accidents, sports injuries, and any blow to the head can trigger bleeding. Intracerebral hematomas, by contrast, often happen without any trauma at all. Chronic high blood pressure is the dominant risk factor, gradually damaging the walls of small arteries deep in the brain until one gives way.
Blood-thinning medications raise the risk for all three types. Even a minor bump to the head can cause significant bleeding when the blood’s ability to clot is reduced. Older age is another major factor: brain shrinkage creates more room for blood to collect before symptoms appear, and the bridging veins between the brain and skull become more fragile over time. Heavy alcohol use, which both thins the blood and increases the chance of falls, compounds the risk further.
Symptoms and Warning Signs
Symptoms depend on how fast blood accumulates and where it collects, but the general pattern is increasing pressure inside the skull. The key signs include:
- Headache that steadily worsens
- Vomiting
- Drowsiness and progressive loss of consciousness
- Dizziness
- Confusion
- Pupils that become different sizes
One of the more dangerous features of brain hematomas is something called the lucid interval. After a head injury, you can feel completely fine for a period of time, with no symptoms at all. Then, as the pooling blood expands and pressure builds, symptoms appear and can worsen rapidly. This is why any significant head injury warrants close monitoring even when you initially feel normal.
Epidural hematomas tend to produce symptoms within hours. Acute subdural hematomas also progress quickly, but chronic subdural hematomas may take weeks to cause noticeable problems, sometimes presenting as gradual confusion or personality changes that mimic dementia.
How Brain Hematomas Are Treated
Treatment depends on the hematoma’s size, how fast it’s growing, and whether it’s causing neurological decline. Small hematomas that aren’t pressing on the brain or worsening over time can sometimes be managed without surgery, with close monitoring through repeated imaging scans. Research published in JAMA Network Open found that for subdural hematomas where neurosurgeons genuinely felt surgery could go either way, conservative (nonsurgical) treatment produced comparable outcomes, particularly when factors like frailty and other injuries were considered.
When a hematoma is large, expanding, or causing rapid deterioration, surgery is necessary. The two main approaches are drilling small holes through the skull to drain the collected blood, or performing a larger opening in the skull (craniotomy) to remove the hematoma directly and repair damaged blood vessels. In severe cases, part of the skull may be temporarily removed to give the swollen brain room to expand without further damage. Among patients who undergo emergency surgery for acute subdural hematomas, the large majority receive this type of decompressive procedure.
Why Pressure Matters: Brain Herniation
The skull is a rigid container. When blood pools and takes up space, the brain has nowhere to go. As pressure builds, brain tissue can be pushed out of its normal position, a process called herniation. This is the most dangerous complication of any brain hematoma and can be fatal.
Doctors measure how far the brain has shifted from its center line (midline shift) on imaging scans to gauge severity. Interestingly, the same volume of blood causes much more shift in younger patients than in older ones. In patients under 60, every additional 10 milliliters of blood causes roughly 1.1 millimeters of shift, compared to only about 0.5 millimeters in patients over 75. This is because older brains have naturally more space from age-related shrinkage, which acts as a buffer. The tradeoff is that older patients can harbor larger hematomas before symptoms become obvious, sometimes delaying diagnosis.
Survival and Long-Term Outlook
Outcomes vary widely depending on the type of hematoma, its size, and how quickly it’s treated. Chronic subdural hematomas, despite being slower to develop, carry a 30-day mortality rate of about 9.4% and a one-year mortality rate near 33%, according to a population-based study in the journal Stroke. These numbers are higher than older estimates, partly because many patients with chronic subdural hematomas are elderly and already have significant health conditions. Only about 36% of patients in that study were functionally unimpaired before their hematoma even developed.
Doctors use the Glasgow Coma Scale (GCS) to assess severity after a traumatic brain injury. The scale runs from 3 to 15, with scores of 13 to 15 classified as mild, 9 to 12 as moderate, and 3 to 8 as severe. A lower GCS score at the time of diagnosis generally predicts a harder recovery and higher risk of lasting disability.
What Recovery Looks Like
Recovery from a brain hematoma can be a long process, and not everyone returns to their previous level of function. The most significant improvement happens during the first six months after the injury. After that, smaller and more gradual gains continue for up to two years, but the pace slows considerably.
Many people need physical therapy to regain strength, balance, and coordination, along with occupational therapy to relearn daily tasks that the brain injury may have disrupted. Cognitive effects like difficulty concentrating, memory problems, and mood changes are common and can persist even after the hematoma itself has been successfully treated. The recovery timeline is highly individual, shaped by the hematoma’s location and size, the patient’s age and overall health, and how quickly treatment was received.