Stroke Ischemic

Ischemic stroke results from restricted blood flow to portions of the brain. The majority of strokes (approximately 80 percent) are ischemic, according to the American Stroke Association. Blood flow to the brain may be restricted by a blood clot (thrombus) or by progressive narrowing of the arteries. People with high cholesterol, diabetes, or heart disease are at increased risk of ischemic stroke.

An ischemic stroke develops quickly. Brain cells begin to die within minutes of the interruption of blood flow to the brain. Prompt medical intervention minimizes cell death and may help restore partial function to damaged areas. Stroke prevention strategies can lower the risk of developing an ischemic stroke.

Atherosclerosis, Cholesterol Plaques, and the Carotid Arteries

Atherosclerosis is the most common cause of ischemic strokes. Atherosclerosis causes cholesterol “plaques” to build up on artery walls, slowing blood flow and depriving organs of oxygen. Cholesterol plaques are often associated with heart disease, but they can develop in any blood vessel.

Cholesterol plaques in the vertebral and carotid arteries, the arteries that feed the brain, may lead to an ischemic stroke. These cholesterol plaques contribute to strokes because the plaques cause narrowing of the arteries and significantly restrict blood flow. The carotid arteries run alongside the jugular veins in the front of the neck, while the vertebral arteries run up the back of the neck. Both of these main arteries branch off into smaller vessels in the brain: a stroke can occur at any point along these arteries.

Thrombus Formation

A thrombus, or blood clot, can also cause an ischemic stroke. Cholesterol plaques in the vertebral or carotid arteries increase the risk of thrombus formation by slowing down the flow of blood.

Blood clots may also form in the heart after a heart attack, or as a result of an irregular heartbeat. A thrombus in the heart does not cause a stroke until it breaks away from its initial location and travels to the brain. The thrombus is then referred to as an embolus, a clot that travels through the blood vessels. The blood clot may then lodge in the arteries of the brain and cause an ischemic stroke.

Deep Vein Thrombosis

While the heart is the most common site for stroke-causing blood clot formation, a thrombus can develop in any blood vessel, even in the absence of cholesterol plaques. A deep vein thrombosis describes clot formation in the large veins of the body. The leg is the most common site for deep vein thrombosis. However, a deep vein thrombosis that breaks off and travels through the circulation is more likely to affect the lungs than the brain. A blood clot that travels into the lungs is referred to as a pulmonary embolism.

In unusual cases, a deep vein thrombosis can generate blood clots that travel to the brain, where they can cause a stroke. This is a rare occurrence, usually only occurring in combination with heart defects.

Hypercoagulability

Some people are more susceptible to blood clot formation than the general population. A heightened risk of thrombus formation is called hypercoagulability, and is caused by genetic defects in the blood’s coagulation factors.

Diabetes

Diabetes increases the risk of experiencing an ischemic stroke. Complications of diabetes include high blood pressure and high cholesterol levels, both of which contribute to stroke. For those with diabetes, controlling cholesterol levels and hypertension is essential for stroke prevention. More information about diabetes and living with the condition is available at Diabetes and Diabetics.

Resources

Goldstein, L., Adams, R., Becker, K., Furberg, C., Gorelick, P., Hademonos, G., Hill, M., et al. (2001, January). Primary prevention of ischemic stroke: A statement for healthcare professionals from the stroke council of the American Heart Association. Circulation, 103; 163-182.

Hesselink, J. (nd). Stroke and cerebral ischemia. Retrieved February 17, 2004, from: fmri.ucsd.edu/neuroweb/Text/br-710.htm.

LifeExtension. (2003). Stroke (ischemic, thrombotic, embolic, and transient ischemic attack). Retrieved February 17, 2004, from www.lef.org/protocols/prtcl-102.shtml.