There are three main types of stroke: ischemic stroke, hemorrhagic stroke, and transient ischemic attack (TIA). Ischemic strokes, caused by blocked blood vessels in the brain, account for roughly 74% of all strokes. Hemorrhagic strokes, caused by bleeding in the brain, make up about 14%. TIAs are temporary blockages that resolve on their own but signal serious future risk. Within each category, several subtypes exist based on what caused the blockage or bleeding.
Ischemic Stroke
An ischemic stroke happens when a blood clot or other obstruction cuts off blood flow to part of the brain. Without oxygen, brain cells start dying within minutes. This is by far the most common type, responsible for nearly three out of every four strokes.
Ischemic strokes break down further based on where the clot forms and how it gets to the brain:
- Thrombotic stroke: A clot forms directly inside an artery that supplies the brain. This typically happens in people with atherosclerosis, where fatty deposits narrow the vessel walls over time. It’s more common in older adults and those with high cholesterol or diabetes.
- Embolic stroke: A clot forms somewhere else in the body, usually the heart, and travels through the bloodstream until it lodges in a brain artery. About 15% of embolic strokes occur in people with atrial fibrillation, a condition where the heart’s upper chambers quiver instead of beating effectively, allowing blood to pool and clot. Embolic strokes tend to strike suddenly with no warning.
- Small vessel stroke (lacunar stroke): Tiny arteries deep in the brain become blocked, producing small areas of damage. High blood pressure, diabetes, and smoking are the main risk factors.
- Cryptogenic stroke: This is an ischemic stroke where doctors can confirm a blockage occurred but cannot identify the specific cause. About one in four people who have a cryptogenic stroke will have another one, which makes follow-up monitoring especially important.
A 2025 classification system proposed in the journal Stroke groups ischemic strokes into four categories by cause: those originating from the heart (cardioembolic), those caused by fatty buildup in large arteries, those affecting small deep vessels, and those caused by other defined mechanisms like artery tears, blood vessel inflammation, or genetic conditions such as sickle cell disease.
Hemorrhagic Stroke
A hemorrhagic stroke occurs when a blood vessel in or around the brain ruptures, spilling blood into surrounding tissue. The bleeding itself damages brain cells, and the pooling blood creates pressure that damages even more. These strokes are less common than ischemic strokes but tend to be more deadly.
There are two main subtypes:
- Intracerebral hemorrhage: A vessel inside the brain bursts. This is the more common of the two hemorrhagic types, accounting for about 14% of all strokes. Long-standing high blood pressure is the leading cause, as it weakens artery walls over years until one gives way.
- Subarachnoid hemorrhage: Bleeding occurs in the space between the brain and the thin tissues covering it. This is often caused by a ruptured aneurysm, a balloon-like weak spot in a blood vessel wall. It frequently announces itself with a sudden, extremely severe headache often described as the worst headache of a person’s life.
Transient Ischemic Attack (TIA)
A TIA produces stroke-like symptoms that last only a few minutes and don’t cause permanent brain damage. It happens when blood flow to the brain is briefly interrupted, then restored on its own. Some people call it a “mini-stroke,” but that label understates the danger.
A TIA is a warning. About one in three people who have a TIA will eventually have a full stroke, and roughly half of those strokes happen within a year. The symptoms are identical to a real stroke while they’re happening, so there’s no way to tell in the moment whether it will pass or cause lasting damage. Every TIA needs emergency evaluation.
How Treatment Differs by Type
The type of stroke determines the treatment, and the two main types require opposite approaches. For an ischemic stroke, the goal is to dissolve or remove the clot. A clot-dissolving medication can be given intravenously within 4.5 hours of when symptoms started. For strokes caused by a large clot in a major brain artery, a procedure to physically retrieve the clot can be performed up to 24 hours after onset in certain patients.
For a hemorrhagic stroke, clot-dissolving drugs would make things worse by increasing bleeding. Treatment focuses on controlling the bleeding, reducing pressure inside the skull, and stabilizing blood pressure. This is why brain imaging is done immediately when someone arrives at the hospital with stroke symptoms. You cannot tell ischemic from hemorrhagic stroke by symptoms alone, and the wrong treatment can be fatal.
Recognizing Symptoms Quickly
Regardless of type, all strokes share a core set of warning signs. The BE FAST acronym covers the most important ones:
- Balance: Sudden difficulty walking or loss of coordination
- Eyes: Sudden vision loss or double vision
- Face: One side of the face droops, especially when trying to smile
- Arm: Weakness or numbness in one arm
- Speech: Slurred or confused speech
- Time: Call emergency services immediately
The older FAST acronym (face, arm, speech, time) misses strokes that primarily affect balance or vision. Adding those two checks catches a larger proportion of strokes, particularly those affecting the back of the brain. Every minute without treatment costs brain cells, so speed matters more than certainty. If something looks like a stroke, treat it like one.