Bleeding on the brain happens when a blood vessel in or around the brain ruptures, allowing blood to leak into surrounding tissue. The most common cause is chronic high blood pressure, but head injuries, structural abnormalities in blood vessels, certain medications, and drug use can all trigger it. The type of bleed depends on where exactly the vessel breaks.
Where Brain Bleeds Happen
Not all brain bleeds are the same. The brain is wrapped in several protective layers between the skull and the brain tissue itself, and bleeding can occur at any of these levels. The location determines both the name and the severity.
An epidural bleed occurs between the skull bone and the outermost membrane layer. A subdural bleed sits one layer deeper, between the outer membrane and the middle one. A subarachnoid bleed happens in the space just above the brain’s surface. And an intracerebral hemorrhage is bleeding directly within the brain tissue itself, in areas like the deep brain structures, brainstem, or the outer lobes. Each type has different causes, and some are far more dangerous than others.
High Blood Pressure
Chronic high blood pressure is the single biggest risk factor for spontaneous brain bleeds. Over years, elevated pressure forces the walls of small arteries in the brain to remodel and weaken. The vessel walls thicken in unhealthy ways, develop tiny balloon-like bulges, and eventually crack open under sustained pressure. When they rupture, high-pressure blood pushes directly into deep brain tissue.
This process tends to affect the smallest arteries deep inside the brain, which is why hypertension-related bleeds typically occur in areas like the basal ganglia, thalamus, and brainstem rather than near the brain’s surface. The damage is largely invisible until a vessel gives way. Inflammation plays a role too: elevated blood pressure triggers immune cells to infiltrate the walls of these small arteries, further weakening the structural proteins that hold the vessels together.
Head Injuries
Traumatic brain injury is a leading cause of brain bleeds, especially epidural and subdural types. When the head is struck, strikes an object, or is shaken violently, the rapid acceleration and deceleration of the brain inside the skull tears blood vessels.
Epidural bleeds, the type that forms between the skull and the outer membrane, typically result from a skull fracture that damages an artery running along the inside of the skull. A classic example is a fracture of the temporal bone (the thin bone on the side of the head) severing the middle meningeal artery. Because arterial blood is under high pressure, these bleeds expand quickly and can become life-threatening within hours.
Subdural bleeds involve veins rather than arteries. The impact tears small “bridging veins” that connect the brain’s surface to the membrane above it. Because venous blood flows at lower pressure, subdural bleeds can develop slowly, sometimes over days or weeks. This is why older adults who fall and hit their heads may not show symptoms right away. The same injury can also cause bleeding directly within brain tissue or in the subarachnoid space.
Aneurysms
A brain aneurysm is a weak, balloon-like bulge in an artery wall. Most people who have one never know it. But if the bulge ruptures, blood spills into the subarachnoid space surrounding the brain, causing a subarachnoid hemorrhage.
The hallmark symptom is the thunderclap headache: an extremely painful headache that reaches peak intensity within 60 seconds. People consistently describe it as the worst headache of their life, completely unlike any headache they have experienced before. It lasts at least five minutes and can be accompanied by nausea, vomiting, vision changes, confusion, numbness, weakness, or seizures. A thunderclap headache is always a medical emergency.
Risk factors for aneurysm rupture include high blood pressure, smoking, heavy alcohol use, and family history. Some aneurysms are present from birth; others develop over a lifetime of wear on the vessel walls.
Arteriovenous Malformations
An arteriovenous malformation (AVM) is an abnormal tangle of blood vessels where arteries connect directly to veins, bypassing the tiny capillaries that normally sit between them. This usually forms before birth. Without capillaries to slow and buffer blood flow, the veins in an AVM are exposed to much higher pressure than they were built to handle. Over time, that pressure damages the vessel walls and can cause them to rupture, leaking blood into the brain or surrounding tissue.
AVMs can bleed at any age, but ruptures happen most often in people between the ages of 15 and 20. Some people with an AVM also have brain aneurysms, compounding the risk. Factors that influence rupture risk include the size and location of the AVM, the person’s age, symptoms, and whether pregnancy is current or planned.
Amyloid Protein Buildup in Older Adults
Cerebral amyloid angiopathy (CAA) is one of the most common causes of brain bleeds in people over 60. In this condition, clumps of abnormal proteins called amyloid gradually accumulate on the inner walls of blood vessels in the brain. Over many years, these deposits weaken the vessel walls, creating microscopic cracks that let blood seep into brain tissue.
The bleeding can range from tiny microbleeds, which may go unnoticed, to larger hemorrhages that cause sudden neurological symptoms. CAA tends to cause bleeds near the brain’s surface (lobar hemorrhages), in contrast to the deep brain bleeds caused by high blood pressure. It is remarkably common: an estimated 23% to 29% of people over age 50 have moderate to severe CAA, though many never experience a noticeable bleed. The condition is also the most common cause of cognitive decline in people aged 60 and older, even without a major hemorrhage.
Blood-Thinning Medications
Anticoagulants and antiplatelet drugs, the medications prescribed to prevent blood clots in conditions like atrial fibrillation or after heart valve replacement, increase the risk of brain bleeds. These drugs work by reducing the blood’s ability to clot, which is helpful for preventing strokes caused by blockages but creates a vulnerability if a vessel in the brain starts to leak.
Among anticoagulants, the risk varies by drug. Older drugs like warfarin carry a well-established risk. Newer direct oral anticoagulants have been designed with lower bleeding profiles, though the risk is not zero. One class of these newer drugs, for example, has been shown to have higher brain bleed rates compared to aspirin, while another appears to carry a similar or slightly lower risk. The clinical guidelines note that use of blood-thinning agents is one of the key factors doctors assess when predicting whether a small bleed will expand into a larger, more dangerous one.
Cocaine and Stimulant Drugs
Cocaine and methamphetamines are potent triggers for brain bleeds. These drugs act as powerful stimulants that flood the body with stress hormones, causing a sudden spike in heart rate and blood pressure. That acute surge in pressure can rupture a vulnerable blood vessel in the brain, even in younger people who would not otherwise be at risk.
The damage goes beyond just the pressure spike. Cocaine also damages the inner lining of blood vessels, impairs the blood’s ability to form protective clots, and triggers inflammation. A large meta-analysis found that recent cocaine use before a stroke was associated with a fivefold increase in the odds of brain bleeding. The drug is a particularly strong risk factor for a condition called reversible cerebral vasoconstriction syndrome, where arteries in the brain spasm and narrow, dramatically raising the risk of multiple types of hemorrhage.
Warning Signs of a Brain Bleed
Symptoms depend on the location and size of the bleed, but they typically come on suddenly. A severe, explosive headache is the most recognizable sign, especially when it reaches maximum intensity in under a minute. Other symptoms include numbness or weakness on one side of the body, difficulty speaking, vision changes, confusion, nausea and vomiting, seizures, and loss of consciousness.
Smaller bleeds, particularly microbleeds from CAA, may produce subtler effects or no symptoms at all. But any sudden, severe headache or sudden onset of neurological symptoms like one-sided weakness or slurred speech warrants emergency evaluation. CT scans can detect bleeding in the brain within minutes and are the primary tool used to confirm a diagnosis and determine whether the bleed is expanding.
What Happens After a Brain Bleed
The immediate priority is stopping the bleed from growing. One of the strongest predictors of a bad outcome is hematoma expansion, where the initial pocket of blood continues to enlarge in the hours after the bleed begins. Controlling blood pressure quickly and smoothly, without large swings, has been shown to reduce expansion and improve recovery.
Some brain bleeds require surgery to remove the pooled blood and relieve pressure on the brain. For bleeds in the cerebellum (the area at the back of the brain that controls balance and coordination), surgery is recommended when the blood volume exceeds about 15 milliliters or when there are signs of pressure on the brainstem. Minimally invasive surgical techniques can reduce the risk of death from larger bleeds, though their ability to improve long-term function is still being studied.
Recovery varies enormously. Small bleeds may resolve with relatively minor lasting effects, while large hemorrhages can cause permanent disability. Rehabilitation typically involves physical therapy, speech therapy, and occupational therapy depending on which brain functions were affected. Caregiver support and education are recognized as important parts of the recovery process, with structured training for family members shown to improve the patient’s balance, activity level, and overall quality of life.