There are two major categories of stroke: hemorrhagic and ischemic. 80% of strokes are ischemic, in which there is a blockage of blood flow to the brain.

Ischemic strokes can occur when a blood clot forms in a blood vessel in the brain or neck. Blood clots can also travel from other parts of the body, such as the heart, to the neck or brain and cause a stroke.

Finally, a blood vessel that is extremely narrowed can cause an ischemic stroke.

The second category of stroke, hemorrhagic, accounts for approximately one out of five strokes and is caused by a blood vessel breaking and leaking blood in or around the brain. Hemorrhagic stroke is associated with a higher death rate than ischemic stroke.

Hemorrhage can occur from a weak or thinned out area on the artery wall that balloons out over time, and then ruptures. Arteries that have plaque can become brittle and thin and can also break.