A hemorrhagic stroke happens when a blood vessel in the brain ruptures and bleeds into or around brain tissue. It accounts for roughly 13% of all strokes, with ischemic strokes (caused by a clot blocking blood flow) making up the other 87%. Despite being less common, hemorrhagic strokes carry the highest mortality rate of any stroke type.
Two Types of Hemorrhagic Stroke
The two main forms are distinguished by where the bleeding occurs. An intracerebral hemorrhage means a blood vessel bursts inside the brain tissue itself. This is the more common type, and it damages brain cells both by depriving them of their blood supply and by creating a mass of blood that puts pressure on surrounding tissue. That pressure can cascade quickly, which is why intracerebral hemorrhages often cause rapid deterioration.
A subarachnoid hemorrhage involves bleeding into the fluid-filled space that surrounds the brain. This type is most often caused by a ruptured aneurysm, a weak, balloon-like bulge in an artery wall. Blood pools around the brain rather than inside it, irritating the brain’s outer covering and raising pressure within the skull. Subarachnoid hemorrhages can also result from head trauma, where impact forces tear small blood vessels near the brain’s surface.
What Causes a Blood Vessel to Rupture
Chronic high blood pressure is the single biggest driver of hemorrhagic stroke. Years of elevated pressure weaken the walls of small arteries deep inside the brain until one eventually gives way. This is the mechanism behind most intracerebral hemorrhages.
Aneurysms are the leading cause of spontaneous subarachnoid hemorrhages. These weak spots in artery walls can exist for years without symptoms. When one ruptures, bleeding is sudden and severe.
In older adults, a condition called cerebral amyloid angiopathy plays a significant role. A sticky protein called beta-amyloid gradually deposits in the walls of small arteries near the brain’s surface. Over time, this causes the vessel walls to thicken, lose their smooth muscle cells, and develop tiny microaneurysms. The vessels become fragile enough to rupture under normal blood pressure, producing bleeds in the outer portions of the brain (called lobar hemorrhages). This process is distinct from the deep-brain bleeds caused by hypertension and is a major cause of hemorrhagic stroke and cognitive decline in the elderly.
Other causes include arteriovenous malformations (tangles of abnormal blood vessels present from birth), blood-thinning medications, blood clotting disorders, and drug use, particularly stimulants that spike blood pressure.
Symptoms and Warning Signs
Hemorrhagic strokes tend to announce themselves more dramatically than clot-based strokes. The hallmark symptom of a subarachnoid hemorrhage is a thunderclap headache, often described as “the worst headache of my life.” What sets this headache apart is not just its severity but how fast it peaks: maximum intensity within seconds to a minute, not a gradual buildup. Accompanying symptoms can include neck stiffness, vomiting, sensitivity to light, confusion, and loss of consciousness.
Some people experience a milder “sentinel headache” days or weeks before a major rupture. This likely represents a small warning leak from the aneurysm and is easy to dismiss as a bad headache or migraine.
Intracerebral hemorrhages produce symptoms that depend on where in the brain the bleeding occurs. Sudden one-sided weakness or numbness, difficulty speaking, loss of vision on one side, severe balance problems, and seizures are all common. A rapidly declining level of consciousness, where the person becomes increasingly difficult to rouse, signals growing pressure inside the skull and is an emergency.
How It Is Diagnosed
A non-contrast CT scan is the first and most important test. When performed within six hours of symptom onset and read by a qualified radiologist, CT detects subarachnoid hemorrhage with 100% sensitivity. That number drops to about 86% after six hours, because blood in the fluid around the brain begins to break down and becomes harder to distinguish on imaging. Intracerebral hemorrhages show up clearly on CT as a bright white mass within brain tissue, and timing is less of a factor for detection.
If a subarachnoid hemorrhage is suspected but the CT is negative (particularly when the scan was delayed), a lumbar puncture can check for blood products in the spinal fluid. Additional imaging, such as CT angiography, is used to locate an aneurysm or other source of bleeding.
Emergency Treatment
The first priority is stopping or slowing the bleed and preventing it from expanding. For people who arrive with very high blood pressure, medical teams carefully lower systolic blood pressure to a target range of 130 to 140 mmHg. Dropping it too aggressively, below 130, can actually cause harm, so the goal is a controlled, steady reduction rather than a sharp drop.
For patients who were taking blood thinners when the hemorrhage occurred, the situation is especially dangerous. These medications prevent normal clotting, so the bleed can expand rapidly. Reversing the blood thinner as quickly as possible is critical. The specific reversal strategy depends on which medication the person was taking. For warfarin, a concentrated clotting factor product is given along with intravenous vitamin K. For newer blood thinners like rivaroxaban and apixaban, a targeted reversal agent called andexanet alfa was approved in 2018 and is now recommended by multiple professional guidelines for life-threatening bleeds. When that agent is unavailable, a general clotting factor concentrate is used as a backup.
Surgical Options
When a ruptured aneurysm is the source of bleeding, the goal of surgery is to seal off the aneurysm so it cannot bleed again. Two approaches exist.
Surgical clipping is an open procedure. A surgeon opens a section of the skull, carefully exposes the aneurysm, and places a small metal clip across its neck to cut off blood flow into the bulge. It is more invasive but achieves more complete closure: incomplete sealing occurs in only about 8% of clipping cases.
Endovascular coiling is minimally invasive. A thin catheter is threaded from an artery in the leg up into the brain’s blood vessels. Once positioned inside the aneurysm, tiny platinum coils are released that pack the aneurysm and trigger clotting, effectively blocking it off from the inside. Coiling involves no opening of the skull, and patients generally have better short-term neurological outcomes. It is also the only practical option for aneurysms located at the back of the brain, which are difficult to reach surgically. The tradeoff is a higher rate of incomplete closure (about 22%), which can require follow-up procedures.
The landmark International Subarachnoid Aneurysm Trial compared the two approaches for ruptured aneurysms and found that coiling reduced the risk of death or dependency by about 7 percentage points. Fourteen-day fatality rates were 6.4% for coiling versus 8.2% for clipping. Coiling has since become the preferred approach at most centers, though clipping remains essential for very large aneurysms or cases where coiling is not technically possible.
For large intracerebral hemorrhages, surgery may be performed to evacuate the blood clot and relieve pressure, though the decision depends heavily on the bleed’s size, location, and the patient’s overall condition.
Recovery and Outlook
Hemorrhagic strokes are more immediately life-threatening than ischemic strokes, and the first 24 to 72 hours are the most critical period. Expansion of the initial bleed, swelling of surrounding brain tissue, and secondary complications like seizures or fluid buildup in the brain all pose ongoing risks during early hospitalization. Most patients are managed in a neurological intensive care unit during this window.
For those who survive the acute phase, recovery follows a trajectory similar to other strokes but often starts from a more severe deficit. Rehabilitation typically involves physical therapy, occupational therapy, and speech therapy depending on which brain areas were affected. Recovery can continue for months to over a year as the brain adapts and heals, though some degree of lasting impairment is common with larger hemorrhages.
Long-term prevention focuses heavily on blood pressure control, which remains the single most effective way to reduce the risk of a first or recurrent hemorrhagic stroke. For patients with cerebral amyloid angiopathy, decisions about resuming blood thinners are particularly complex, since these medications can increase the risk of another bleed in already-fragile vessels.