The causes of a stroke include either a blood clot in a blood vessel, most likely an artery, that blocks blood flow in the brain, or a blood vessel rupturing in the brain and causing a hemorrhage, according to WebMD. The most common type of stroke is the one from a clot. Though only about 20 percent of all strokes are hemorrhagic, they are the most dangerous kind.
In the case of stroke caused by clots, blocked blood flow causes the brain to be starved of nutrients and oxygen. With a hemorrhagic stroke, the very act of rupturing can flood the brain tissue with blood and damage it, states WebMD.
Several factors can put a person at risk for a stroke, according to WebMD. The biggest risk for a stroke is hypertension, which exerts pressure against the walls of a blood vessel and eventually weakens it. Other risk factors are atherosclerosis, which lays plaque along the walls of arteries and can cause them to dangerously narrow.
Other risk factors for stroke include cardiovascular disease and high cholesterol levels, says WebMD. Smoking also puts a person at risk for stroke because it starves the blood of oxygen. This makes the heart work harder and can worsen conditions such as atherosclerosis. Diabetes, obesity, heavy alcohol use and certain drugs can also put a person at higher risk for stroke.