- A blood vessel carrying blood to the brain is blocked by a blood clot. This is called an ischemic stroke.
- A blood vessel breaks open, causing blood to leak into the brain. This is a hemorrhagic stroke.
If blood flow is stopped for longer than a few seconds, the brain cannot get blood and oxygen. Brain cells can die, causing permanent damage.
The most common type of stroke is called a Ischemic Stroke. Usually this type of stroke results from clogged arteries, a condition called atherosclerosis. Fatty deposits collect on the wall of the arteries, forming a sticky substance called plaque. Over time, the plaque builds up. Often, the plaque causes the blood to flow abnormally, which can cause the blood to clot. There are two types of clots:
- A clot that stays in place in the brain is called a cerebral thrombus.
- A clot that breaks loose and moves through the bloodstream to the brain is called a cerebral embolism.
Another important cause of cerebral embolisms is a type of arrhythmia called atrial fibrillation. Other causes of ischemic stroke include endocarditis, an abnormal heart valve, and having a mechanical heart valve. A clot can form on a heart valve, break off, and travel to the brain. For this reason, those with mechanical or abnormal heart valves often must take blood thinners.
STROKE RISKS
High blood pressure is the number one reason that you might have a stroke. The risk of stroke is also increased by age, family history of stroke, smoking, diabetes, high cholesterol, and heart disease.
Certain medications increase the chances of clot formation, and therefore your chances for a stroke. Birth control pills can cause blood clots, especially in woman who smoke and who are older than 35.
Men have more strokes than women. But, women have a risk of stroke during pregnancy and the weeks immediately after pregnancy.
Health and Medical 
