Ischemic stroke happens when a blood vessel in the brain gets blocked, cutting off blood flow. Hemorrhagic stroke happens when a blood vessel in the brain ruptures and bleeds. Ischemic strokes account for about 65% of all strokes worldwide, while hemorrhagic strokes (including both bleeding within brain tissue and bleeding around the brain) make up roughly 35%. Despite being less common, hemorrhagic strokes are significantly more deadly in the first weeks after they occur.
How Each Type Damages the Brain
In an ischemic stroke, something physically blocks a blood vessel that supplies the brain. Without incoming blood, brain cells in the affected area are starved of oxygen and nutrients. Within minutes, those cells begin to die. The blockage is usually a blood clot, though it can also be a buildup of fatty plaque that has narrowed the artery over time. About 45% of ischemic strokes are caused by a clot forming directly inside a brain artery, while 14 to 30% are caused by a clot that forms elsewhere in the body (often the heart) and travels to the brain through the bloodstream.
In a hemorrhagic stroke, a weakened blood vessel bursts open. Blood spills into or around the brain, where it pools and creates pressure on surrounding tissue. That pressure damages brain cells directly, and the ruptured vessel can no longer deliver blood to the area it normally supplies, so those downstream cells also lose their oxygen. The pooling blood can continue to expand, which is why hemorrhagic strokes often worsen rapidly in the first hours.
Subtypes of Ischemic Stroke
Not all ischemic strokes form the same way. In a thrombotic stroke, a blood clot develops inside a brain artery itself. This type is more common in older adults with high cholesterol, diabetes, or significant buildup of fatty deposits in their blood vessels. Thrombotic strokes sometimes begin during sleep or in the early morning hours.
In an embolic stroke, the clot forms somewhere else, usually the heart, and travels through the bloodstream until it lodges in a narrower brain artery. Embolic strokes tend to strike suddenly with no warning. About 15% of them occur in people with atrial fibrillation, a condition where the heart’s upper chambers beat irregularly, allowing blood to pool and clot.
A third subtype, called a lacunar stroke, accounts for 15 to 25% of ischemic strokes. These involve very small arteries deep in the brain and are strongly tied to chronic high blood pressure.
Subtypes of Hemorrhagic Stroke
Hemorrhagic strokes are classified by where the bleeding occurs. An intracerebral hemorrhage means blood is leaking directly into the brain tissue. The most common cause is long-standing high blood pressure, which weakens the walls of small arteries over years until one finally gives way. Other causes include abnormal tangles of blood vessels, blood-thinning medications, tumors, and infections.
A subarachnoid hemorrhage means blood is filling the space between the brain and the tissue that covers it. The most common non-traumatic cause is a ruptured aneurysm, a balloon-like weak spot in a blood vessel wall. Trauma to the head is actually the overall leading cause of bleeding in this area, but when doctors talk about subarachnoid hemorrhage as a stroke, they typically mean the spontaneous kind caused by an aneurysm. Globally, intracerebral hemorrhages make up about 29% of all strokes, while subarachnoid hemorrhages account for roughly 6%.
Symptoms That Overlap and Differ
Both types of stroke share core warning signs: sudden numbness or weakness on one side of the body, difficulty speaking, confusion, trouble seeing, and loss of coordination. These shared symptoms exist because both types damage brain tissue, just through different mechanisms. You cannot reliably tell which type is occurring based on symptoms alone.
That said, hemorrhagic strokes are more likely to produce certain intense symptoms. A sudden, explosive headache is a hallmark, especially in subarachnoid hemorrhage, where patients often describe the worst headache of their life, sometimes called a “thunderclap” headache. Vomiting, neck stiffness, sensitivity to light, and rapid loss of consciousness are all more common with hemorrhagic strokes. These symptoms reflect the rising pressure inside the skull as blood accumulates. Seizures can also occur, particularly when bleeding affects the outer layers of the brain.
Ischemic strokes, by contrast, more often develop with neurological deficits (weakness, speech problems, vision loss) but without the severe headache or vomiting. Some ischemic strokes even develop gradually over hours, while hemorrhagic strokes almost always present acutely and progress quickly.
How Doctors Tell Them Apart
No physical exam can definitively distinguish the two types. The first step in the emergency room is a CT scan of the head without contrast dye. This scan is fast, often completed in minutes, and its primary job is straightforward: look for blood. Fresh bleeding shows up as a bright white area on a CT scan. If no blood is visible, the working diagnosis shifts to ischemic stroke, though early ischemic strokes can be hard to see on CT in the first few hours.
MRI is more sensitive for detecting ischemic damage and can pick up strokes that CT misses, especially small ones. However, MRI takes longer, is not always available around the clock, and historically has been less reliable at detecting very fresh bleeding. Newer MRI techniques have improved this, but CT remains the standard first-line scan because speed matters: treatment decisions hinge on knowing the stroke type as quickly as possible. Imaging of the blood vessels themselves, through CT or MRI angiography, typically follows to locate the exact blockage or source of bleeding.
Treatment Takes Opposite Approaches
This is one of the most important practical differences between the two stroke types. Their treatments are essentially opposites, which is why fast, accurate diagnosis is critical.
For ischemic stroke, the goal is to dissolve or remove the clot and restore blood flow. A clot-dissolving medication given through an IV is effective when administered within about 4 hours of symptom onset, though in carefully selected patients guided by advanced brain imaging, it has been used successfully up to 24 hours later. For large clots blocking major brain arteries, a procedure called mechanical thrombectomy can physically pull the clot out using a catheter threaded through the blood vessels. Clinical trials have shown this procedure benefits patients up to 6 hours after symptoms begin, and in some cases, up to 24 hours when imaging shows brain tissue that can still be saved.
For hemorrhagic stroke, clot-dissolving drugs would be catastrophic, as they would make the bleeding worse. Treatment instead focuses on stopping the bleed, controlling blood pressure to reduce further bleeding, and managing the pressure building inside the skull. If the cause is a ruptured aneurysm, the aneurysm needs to be sealed off to prevent re-bleeding. This can be done surgically by placing a small clip at the base of the aneurysm, or less invasively by threading tiny coils into the aneurysm through a catheter to block blood flow into it. In severe cases, surgery to drain accumulated blood or relieve pressure on the brain may be necessary.
Risk Factors for Each Type
High blood pressure is the single biggest modifiable risk factor for both types, but it is especially dominant in hemorrhagic stroke. In a large study of 1.25 million patients, every 20-point increase in systolic blood pressure was most strongly associated with intracerebral and subarachnoid hemorrhage. Years of elevated blood pressure weaken arterial walls, making them vulnerable to rupture.
Ischemic stroke has a broader set of risk factors tied to clot formation and narrowed arteries. Atrial fibrillation is one of the strongest, since the irregular heartbeat allows blood to pool and form clots that can travel to the brain. High cholesterol, diabetes, smoking, and atherosclerosis (the gradual buildup of fatty deposits in artery walls) all increase the risk of vessel blockages. Obesity and physical inactivity contribute to many of these underlying conditions.
Blood-thinning medications create a paradox worth understanding. They are prescribed to people with atrial fibrillation precisely to prevent ischemic strokes, but they simultaneously increase the risk of hemorrhagic stroke if a vessel ruptures while clotting ability is reduced. This is a trade-off that doctors weigh carefully for each patient.
Survival and Recovery Outlook
Hemorrhagic strokes are far more lethal in the short term. Within 30 days, about 20% of hemorrhagic stroke patients die, compared to roughly 5% of ischemic stroke patients. At 7 days, the gap is even starker: 13% versus less than 2%. By 90 days, the case fatality rate reaches 25% for hemorrhagic strokes and 11% for ischemic strokes.
Interestingly, after the 3-month mark, the type of stroke no longer predicts mortality differences. Survivors of both types face similar long-term risks going forward. This suggests that the acute damage from hemorrhagic strokes is more immediately devastating, but those who survive the critical early period can have comparable long-term outcomes to ischemic stroke survivors.
Recovery from either type depends heavily on how much brain tissue was damaged, where in the brain the stroke occurred, and how quickly treatment was received. Rehabilitation for both types typically involves physical therapy, speech therapy, and occupational therapy, tailored to whichever functions were affected.