Stroke Health Center

Strokes happen when the blood supply to the brain is blocked or reduced, which can keep the brain from getting the oxygen it needs.

There are two main types of major strokes — with slightly different causes.

The first type, ischemic stroke, is a result of arteries leading to the brain being blocked. This is the most common type of stroke. Around 85 percent of all strokes are ischemic, according to the Mayo Clinic.

The underlying cause of an ischemic stroke is often the buildup of fatty deposits on blood vessel walls. Over time, this buildup can block blood flow to the brain and cause the blood to clot.

The second type of stroke is the hemorrhagic stroke. In this type of stroke, a blood vessel in the brain breaks or leaks. This stroke type accounts for around 13 percent of all stroke cases, according to the American Stroke Association.

Once a blood vessel in the brain has broken or has begun leaking, blood can accumulate in the brain and put pressure on surrounding brain tissue.