The Science Of Strokes
Stated simply, a stroke occurs when the blood supply to your brain is interrupted or reduced. This occurrence deprives your brain of blood and nutrients, leaving it un- able to function correctly. The CDC estimates that about 6.5 million adults in the United States have had a stroke, and it is the fifth leading cause of death in this country.
Things become more compli- cated when you consider the various types of strokes.
This type makes up about 85 percent of strokes, and occurs when arteries to your brain become narrowed or blocked, leading to severely reduced blood flow. The most com- mon ischemic strokes include:
Thrombotic stroke – These occur when a blood clot (thrombus) forms in one of the arteries supplying blood to the brain, which may be caused by fatty depos- its (plaque) in the arteries causing reduced blood flow (atherosclerosis).
Embolic stroke – This type of stroke happens when a blood clot (embolus) or other debris forms away from the brain, often in the heart, and is carried by the bloodstream to the arteries in your brain.
These occur when a blood vessel in your brain leaksor ruptures. These can be caused by high blood pressure (hypertension), overtreatment with anticoagulants, and weak spots in your blood vessel walls (aneurysms).
Basically, there are two types of hemorrhagic strokes.
• Intracerebral hemorrhage – This stroke is caused by a blood vessel in the brain bursting, spilling blood into surrounding brain tissue and damaging brain cells. Brain cells beyond the leak are also damaged when deprived of blood.
• Subarachnoid hemorrhage – This stroke is commonly caused by the bursting of an aneurysm on an artery on or near the surface of the brain, often accompanied by a sudden, severe headache. Blood vessels in the brain may also widen and contract erratically, limiting blood flow and inflicting further brain damage.
TRANSIENT ISCHEMIC ATTACK (TIA)
Often called a mini-stroke, a TIA occurs when a clot or de- bris temporarily blocks blood flow to part of your brain. The symptoms—vision changes, slurred speech, balance issues, tingling, and dizziness, among others—often clear within about five minutes, but you should get immediate medical treatment as a TIA puts you at risk for a full-blown stroke.