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The arteries bring oxygen and other nutrients to the cells of the body. The veins take away the blood after the cells have taken in the oxygen and nutrients and given up their waste products, such as carbon dioxide. If blood flow is decreased to any part of the body, that area does not get enough oxygen and nutrients and is unable to get rid of its waste products adequately.
Decreased blood flow can occur in the arteries and veins anywhere in the body, such as the neck and brain. When the neck arteries (carotid arteries) become occluded, symptoms such as dizziness, confusion, drowsiness, headache, and/or a brief loss of ability to speak or move, may be the early warning signs of a possible stroke (brain attack).
More severe symptoms, such as sudden sharp headache, loss of vision in one eye, sudden loss of ability to move arms, legs, or one side of the body, sudden forceful vomiting, or sudden decreased level of consciousness may mean that a stroke is imminent.
Some conditions which may affect blood flow include, but are not limited to, the following:
Aneurysm- A dilation of a part of the heart muscle or the aorta (the large artery that carries oxygenated blood out of the heart to the rest of the body), which may cause weakness of the tissue at the site of the aneurysm
Embolus or thrombus- Clots in blood vessels may be either an embolus (a small mass of material such as fat globules, air, clusters of bacteria, or even foreign matter such as a piece of metal from a bullet) or a thrombus (a blood clot)
Inflammatory conditions - An inflammation within a blood vessel may occur as a result of trauma (physical trauma, such as from a fall, or chemical trauma, such as from an irritating medication being introduced into the vessel), infection, or an autoimmune disorder (e.g., polyarteritis, Raynaud's disease, and aortic arch syndrome)