A stroke occurs when there's a problem with the amount of blood in your brain. The cause of the main type of stroke — ischemic stroke — is too little blood in the brain. The cause of the other type of stroke — hemorrhagic stroke — is too much blood within the skull.
1) Ischemic stroke:
About 80 percent of strokes are ischemic strokes. They occur when the arteries to your brain are narrowed or blocked, causing severely reduced blood flow (ischemia).a) Thrombotic stroke. This type of stroke occurs when a blood clot (thrombus) forms in one of the arteries that supply blood to your brain. A clot usually forms in areas damaged by atherosclerosis.
b) Embolic stroke.
An embolic stroke occurs when a blood clot or other particle forms in a blood vessel away from your brain — commonly in your heart — and is swept through your bloodstream to lodge in narrower brain arteries. This type of blood clot is called an embolus. It's often caused by irregular beating in the heart's two upper chambers (atrial fibrillation). This abnormal heart rhythm can lead to poor blood flow and the formation of a blood clot.
2) Hemorrhagic stroke
"Hemorrhage" is the medical word for bleeding. Hemorrhagic stroke occurs when a blood vessel in your brain leaks or ruptures.a) Intracerebral hemorrhage: In this type of stroke, a blood vessel in the brain bursts and spills into the surrounding brain tissue, damaging cells.
b) Subarachnoid hemorrhage. In this type of stroke, bleeding starts in a large artery on or near the surface of the brain and spills into the space between the surfaces of your brain and your skull.
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