A subdural hematoma is not a stroke. Although both involve bleeding or disrupted blood flow in or around the brain, the American Heart Association explicitly excludes subdural hematomas from its official definition of stroke. The two conditions differ in where the bleeding occurs, what causes it, and how it’s treated.
Why a Subdural Hematoma Isn’t a Stroke
A stroke is defined as brain damage caused by either a blocked blood vessel (ischemic stroke) or bleeding inside the brain tissue itself (hemorrhagic stroke). The key word is “inside.” A hemorrhagic stroke involves blood collecting within the brain’s own tissue, damaging neurons directly. A subdural hematoma, by contrast, is a collection of blood that forms between the brain’s surface and the protective membrane (the dura) that lines the inside of the skull. The blood sits outside the brain, pressing on it from above rather than tearing through it.
The AHA’s updated stroke definition states this directly: “Given the differences in pathology and most likely causes, subdural and epidural hematomas are not considered ‘strokes.'” The distinction matters because the causes, treatments, and expected outcomes are fundamentally different.
Different Causes, Different Blood Vessels
Strokes are vascular events. Ischemic strokes happen when a clot blocks an artery feeding the brain. Hemorrhagic strokes happen when a weakened artery inside the brain bursts, often due to chronic high blood pressure or an aneurysm. Neither type requires an injury to trigger it.
Subdural hematomas are almost always caused by trauma, even if it’s minor. A blow to the head causes the brain to shift inside the skull, tearing small veins (called bridging veins) that connect the brain’s surface to the drainage channels in the dura. These are low-pressure veins, so the bleeding is often slow, allowing blood to gradually spread in a crescent shape over the brain’s surface. In older adults, the brain naturally shrinks with age, which stretches these bridging veins tighter and makes them more vulnerable. Even a minor fall or bump can tear one.
Why Symptoms Can Look Similar
Despite being different conditions, subdural hematomas and strokes can produce strikingly similar symptoms: confusion, weakness on one side of the body, difficulty speaking, and headache. This is because both ultimately affect brain function, just through different mechanisms. A stroke destroys brain tissue directly. A subdural hematoma compresses it from the outside, and if the blood collection is large enough, that pressure disrupts normal brain activity in much the same way.
Chronic subdural hematomas are particularly easy to confuse with other conditions. Because the bleeding is slow, symptoms may not appear for weeks or even months after the initial injury. The gradual onset of confusion, memory problems, and unsteadiness can look like dementia, a brain tumor, or a stroke. Cleveland Clinic notes that chronic subdural hematomas are more common in people over 65, the same population at highest risk for stroke and dementia, which adds to the diagnostic confusion.
Acute subdural hematomas, on the other hand, cause severe symptoms within minutes to hours of a head injury. The rapid onset can mimic a stroke, but the history of recent head trauma is usually the clearest clue pointing toward a subdural hematoma instead.
How Doctors Tell Them Apart
A CT scan of the head is the fastest way to distinguish between the two. The imaging patterns are distinct. A subdural hematoma appears as a crescent-shaped collection of blood draped over the brain’s surface, compressing the tissue beneath it. A hemorrhagic stroke shows up as a dense spot of blood embedded within the brain tissue itself. An ischemic stroke may not show up immediately on CT but will appear as a dark area where brain tissue has lost blood flow.
Clinicians evaluating someone with stroke-like symptoms are trained to consider non-vascular causes that can mimic a stroke, including subdural hematomas, brain tumors, infections, and metabolic problems. This is why imaging is done urgently: the correct diagnosis changes everything about treatment.
Treatment Is Completely Different
This is where the distinction between these two conditions has the most practical consequences. Ischemic strokes are treated by restoring blood flow, often with clot-dissolving medications given through an IV. Hemorrhagic strokes may require surgery to relieve pressure and stop bleeding inside the brain.
Subdural hematomas are treated surgically when they’re large enough to cause symptoms. The most common procedure involves drilling small holes (burr holes) through the skull to drain the collected blood and relieve pressure on the brain. For larger or solid clots, a surgeon may need to temporarily remove a section of skull bone (a craniotomy) to access and clear the blood. Smaller subdural hematomas that aren’t causing significant symptoms may be monitored with repeat imaging and allowed to reabsorb on their own.
Giving clot-dissolving medication to someone with a subdural hematoma would be dangerous, potentially worsening the bleeding. This is one of the most critical reasons why accurate diagnosis matters so urgently.
Risk Factors for Each Condition
Stroke risk factors center on cardiovascular health: high blood pressure, diabetes, smoking, high cholesterol, and irregular heart rhythms like atrial fibrillation. These are conditions that damage blood vessels or promote clot formation over time.
Subdural hematoma risk factors are different. Age is the biggest one, because brain shrinkage stretches those bridging veins and makes them fragile. Falls are the most common trigger. Blood-thinning medications significantly raise the risk as well. Research published in Neurology found that anticoagulant use in older adults was associated with increased risk of rebleeding after a chronic subdural hematoma, while antiplatelet medications alone did not carry the same added risk. People who take both anticoagulants and antiplatelets may face an even higher chance of recurrence.
Alcohol use disorder is another risk factor for subdural hematomas, both because it increases fall risk and because chronic heavy drinking can cause brain atrophy, putting more tension on those vulnerable bridging veins.
Recovery and Outlook
Recovery patterns differ between the two conditions. For hemorrhagic strokes, the early outlook is grim: roughly half of all patients with bleeding inside the brain die within the first month. However, those who survive tend to recover functional abilities more effectively during rehabilitation than ischemic stroke patients. One study found that hemorrhagic stroke survivors were about 2.5 times more likely to achieve a strong recovery in daily functioning compared to ischemic stroke patients.
Subdural hematoma outcomes depend heavily on the type. Chronic subdural hematomas caught and drained in time often have good outcomes, since the brain tissue underneath was compressed but not destroyed. Acute subdural hematomas from severe trauma carry much higher mortality and disability rates, particularly when the bleeding is large or treatment is delayed. The underlying brain injury from the trauma itself, not just the blood collection, often determines long-term recovery.