Risk Factors of Ischemic Brain Injury

Risk Factors

1. Risk Factors That Can Be Treated

•    High blood pressure (hypertension) is the most important risk factor for stroke.
•    Heart disease such as coronary artery disease, damaged heart valves, heart rhythm problems increase the risk of stroke as compare to healthy heart.
•    Atherosclerosis called "hardening of the arteries” because build up of fatty materials, cholesterol, and calcium on the inside walls of the arteries block the vessels and increase the risk of stroke.
•    High red blood cell count thickens the blood, leading to blood clots.
•    Transient ischemic attacks (TIAs) usually happen when a blood clot temporarily blocks an artery in the brain or neck. TIAs are a warning sign of a possible stroke.

2.Risk Factors That Cannot Be Changed

•    Age: The risk of stroke increases with age. From age 55 onward, chances of having a stroke more than double every ten years.
•    Gender: The incidence of stroke is about 19% higher for men than for women..
•    Race: According to the American Heart Association, African Americans have a higher risk of stroke than Caucasians.
•    Diabetes: can be controlled; people with the disease are still more likely to have a stroke. If blood sugar is high, brain damage at the time of a stroke may be more severe and widespread.
•    Heredity: The risk of stroke is greater in people who have a family history of stroke and TIAs.
•    Carotid bruit: A bruit is an abnormal sound heard when a stethoscope is placed over a blocked artery, in this case the carotid artery. A carotid bruit most often means an increased risk for stroke.
•    Carotid artery disease: Fatty deposits found in the carotid artery could block blood supply.

3. Contributing Risk Factors

•    Smoking and Heavy alcohol use: According to the National Stroke Association, smoking and alcohol use doubles the risk for stroke.
•    Physical inactivity: Inactivity is not only a major risk factor for developing coronary artery disease, but it can also lead to high blood pressure, low levels of high-density lipoproteins and diabetes.
•    Obesity. According to the National Institute of Diabetes and Digestive and Kidney Disease, obesity doubles the risk for developing high blood pressure, a major risk factor for stroke.
•    Birth control pills (oral contraceptives) alone are a low-level risk factor. But if birth control pills are combined with certain other risk factors such as smoking, the risk of stroke increases.


4. Ischemic Penumbra

Within the ischemic cerebrovascular bed, there are two major zones of injury: the core ischemic zone and the "ischemic penumbra"

In the core zone, which is an area of severe ischemia (blood flow below 10% to 25%), the loss of inadequate supply of oxygen and glucose results in rapid depletion of energy stores.  Severe ischemia can result in necrosis of neurons and also of supporting cellular elements (glial cells) within the severely ischemic area.
Brain cells within the penumbra, a rim of mild to moderately ischemic tissue lying between tissue that is normally perfused and the area in which infarction is evolving, may remain viable for several hours.  That is because the penumbral zone is supplied with blood by collateral arteries anastomosing with branches of the occluded vascular tree (see inset).  However, even cells in this region will die if reperfusion is not established during the early hours since collateral circulation is inadequate to maintain the neuronal demand for oxygen and glucose indefinitely.