The three types of stroke are ischemic stroke, hemorrhagic stroke, and transient ischemic attack (TIA). Each involves a different problem with blood flow to the brain: ischemic strokes happen when blood flow is blocked, hemorrhagic strokes happen when a blood vessel bursts, and TIAs are temporary blockages that resolve on their own but signal serious danger ahead.
Ischemic Stroke
Ischemic stroke is by far the most common type, accounting for 87% of all strokes. It occurs when a blood clot or other obstruction cuts off blood supply to part of the brain. Without oxygen-rich blood, brain cells in the affected area begin dying within minutes.
There are two main ways an ischemic stroke develops. In a thrombotic stroke, a blood clot forms directly inside an artery that supplies the brain. This usually happens in arteries already narrowed by fatty buildup along the vessel walls. The clot grows until it blocks enough of the artery to starve downstream brain tissue. In an embolic stroke, a clot forms somewhere else in the body, typically the heart, and travels through the bloodstream until it lodges in a narrower brain artery. People with irregular heart rhythms like atrial fibrillation are especially vulnerable to this type because blood can pool and clot in the heart’s chambers.
In roughly 17% of ischemic strokes, doctors cannot pinpoint a definitive cause even after thorough testing. These are sometimes called cryptogenic strokes. The clot clearly traveled from somewhere, but standard workups don’t reveal an obvious source. Identifying these cases matters because the treatment strategy for preventing a second stroke depends on knowing what caused the first one.
How Ischemic Stroke Is Treated
Speed is everything. The standard clot-dissolving medication has been used for 30 years, and its effectiveness drops sharply with every passing minute. Originally, it had to be given within 3 hours of symptom onset. That window has since expanded to 4.5 hours as routine practice, and in select patients where brain imaging shows salvageable tissue, treatment may be offered up to 9 hours after symptoms start or even in cases where a person wakes up with symptoms and the exact onset time is unknown.
For strokes caused by a large clot blocking a major brain artery, doctors can also thread a thin catheter through a blood vessel and physically remove the clot. This mechanical approach can be performed in some patients up to 24 hours after onset when imaging confirms there is still brain tissue worth saving. Not every hospital offers this procedure, which is why stroke patients are sometimes transferred to specialized centers.
Hemorrhagic Stroke
Hemorrhagic strokes happen when a weakened blood vessel in or around the brain ruptures and bleeds. They are less common than ischemic strokes but tend to be more deadly. The bleeding puts direct pressure on surrounding brain tissue while also depriving downstream areas of their blood supply. There are two distinct subtypes based on where the bleeding occurs.
Intracerebral Hemorrhage
This is bleeding that happens within the brain tissue itself. The most frequent cause is long-term high blood pressure, which gradually weakens small arteries deep in the brain. Over years, chronic hypertension damages these vessel walls, making them brittle and prone to forming tiny bulges. Eventually one of these weakened vessels gives way. Other causes include blood-thinning medications, cocaine or amphetamine use, abnormal tangles of blood vessels present from birth, and a condition in older adults where a protein called amyloid builds up in brain blood vessel walls and makes them fragile.
Subarachnoid Hemorrhage
This type involves bleeding into the space between the brain and the thin tissue covering it. The most common cause is a ruptured aneurysm, a balloon-like bulge in an artery wall that can be present for years without symptoms until it bursts. A subarachnoid hemorrhage often announces itself with what people describe as the worst headache of their life, sudden and explosive. It is a medical emergency that requires immediate intervention.
How Hemorrhagic Stroke Is Treated
Treatment for hemorrhagic stroke is fundamentally different from ischemic stroke. Instead of dissolving or removing a clot, the goal is to stop the bleeding and reduce pressure on the brain. For ruptured aneurysms, there are two main approaches. In surgical clipping, a surgeon opens the skull and places a small metal clip at the base of the aneurysm to seal it off. In endovascular coiling, a catheter is threaded through blood vessels to the aneurysm, where tiny platinum coils are packed inside to promote clotting and seal the bulge from within.
Both methods are effective, but they have different trade-offs. A major international trial found that coiling resulted in better outcomes at one year, with a 7.4% absolute reduction in death or dependency compared to clipping. However, clipping is more durable over the long term. Patients who undergo coiling have a slightly higher rate of rebleeding in the first year (3% versus 1.3% for clipping) and are more likely to need follow-up procedures. The choice between the two depends on the aneurysm’s size, shape, and location, as well as the patient’s overall health.
Transient Ischemic Attack (TIA)
A TIA is sometimes called a “mini-stroke,” but that term understates how serious it is. A TIA occurs when blood flow to the brain is temporarily blocked, causing stroke-like symptoms that resolve on their own without leaving permanent brain damage visible on imaging. The old definition set the cutoff at symptoms lasting less than 24 hours, but the modern understanding focuses on whether imaging shows actual tissue injury rather than how long symptoms last.
The real danger of a TIA is what comes next. Between 10% and 15% of people who have a TIA go on to have a full stroke within three months, and half of those strokes happen within just 48 hours. A TIA is not a minor event that passed. It is an urgent warning that the conditions for a major stroke are already in place, whether that means a narrowed artery, an undetected heart rhythm problem, or an active clotting issue. Getting evaluated immediately after a TIA gives doctors the chance to identify the cause and intervene before a devastating stroke occurs.
Recognizing Stroke Symptoms
All three types of stroke share core warning signs. The most widely taught recognition tool is the acronym BE FAST: Balance problems, Eye changes (sudden vision loss or double vision), Face drooping, Arm weakness, Speech difficulty, and Time to call emergency services. The original version, FAST, focused only on face, arm, speech, and time. It correctly identified about 66% of strokes. Adding balance and eye symptoms was proposed to catch an additional 14% of cases that FAST alone misses, particularly strokes affecting the back of the brain, which tend to cause dizziness and vision problems rather than the classic one-sided weakness.
The symptoms of a TIA are identical to those of a full stroke while they are happening. There is no way to tell in the moment whether symptoms will resolve or worsen. Any sudden onset of these symptoms demands an immediate call to emergency services, even if the symptoms seem to be fading.
How Stroke Severity Is Measured
When you arrive at a hospital with stroke symptoms, the medical team will quickly assess how severely the brain is being affected using a standardized scoring system. It tests things like your ability to follow commands, move your limbs, speak clearly, and see normally. Scores range from 0 to 42, with higher numbers indicating more serious strokes. A score of 0 to 5 indicates a minor stroke, 6 to 15 is moderate, 16 to 20 is moderate to severe, and 21 to 42 is severe. This score helps guide treatment decisions, including whether clot-removal procedures are appropriate, and provides an early indication of what recovery might look like.