According to the American Stroke Association, stroke is the third leading cause of death in the United
States. Two primary causes of stroke are ischemia and hemorrhage. Ischemia, the most common, causes reduced blood flow to the brain, depriving brain cells of oxygen. Hemorrhage accounts for approximately 20 percent of all strokes and occurs when a blood vessel in the brain leaks or bursts, causing bleeding in the brain.
Blocked Blood Vessels
When the blood flow to the brain is blocked, it results in oxygen deprivation to brain cells. The American Heart Association says brain cells begin to die within three to four minutes without oxygen. Blockage in blood flow in the carotid artery, the main blood supply to the brain, is a common area that becomes blocked, leading to a thrombotic stroke. Blood clots can also occur in other blood vessels in the neck or brain. Atherosclerosis is a buildup of fatty tissues, or plaque, and is a frequent reason for reduced or blocked blood flow in the carotids. Sometimes blood clots can occur in other areas of the body away from the brain, especially in the heart. These clots, or emboli, dislodge and travel to the smaller, narrower blood vessels in the brain, resulting in blockage and an embolic stroke. Some of the other factors that increase one's propensity for ischemia include a poor diet high in fats or cholesterol, smoking, physical inactivity, obesity and heart disease.
Transient Ischemia
A temporary blockage of blood flow to the brain results in a transient ischemic attack, often called TIA, or a "mini stroke." Typically, this temporary loss of oxygen to the brain does not result in permanent damage to the brain, even though symptoms of TIA are similar to an ischemic stroke. A TIA lasts only a few minutes, and any loss of function is usually restored. The cause of the temporary loss of blood flow results from reasons similar to an ischemic stroke, the narrowing or clotting of an artery or blood vessel. A person who has a TIA is considered at high risk for experiencing an ischemic stroke.
Leaking or Burst Blood Vessels
When a blood vessel in or near the brain leaks or bursts, it results in a hemorrhagic stroke. Hemorrhages that occur within the brain are called intracerebral hemorrhages. High blood pressure (hypertension) is the leading cause of intracerebral hemorrhages. It damages and overstretches blood vessels, weakening them and making them more prone to rupture.
Aneurysms
Aneurysms, or hemorrhages in blood vessels on or near the brain, are called subarachnoid hemorrhages. Aneurysms that cause subarachnoid hemorrhages can develop as a result of hardening of the arteries, a genetic predisposition or with age.
Prevention Tips
The American Heart Association provides these suggestions for reducing high blood pressure: a healthy, low-salt diet; regular physical activity; maintaining a healthy weight; managing stress; limiting alcohol intake; and not smoking. The Mayo Clinic advises refraining from the use of illicit drugs and taking prescribed preventive medications, such as anti-platelet or anticoagulants drugs, as sound stroke prevention measures.
