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 unable 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 complicated when you consider the various types of strokes.

Ischemic 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 common 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 deposits (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.

Hemorrhagic Strokes

These occur when a blood vessel in your brain leaks or 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 debris 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.

Stroke Risk Factors & Prevention

In addition to age and family history, certain other risk factors increase your chances of having a stroke.

Lifestyle Risk Factors

The most common of these include being overweight, lack of physical activity, heavy drinking, and smoking or exposure to secondhand smoke.

Medical Risk Factors

The main culprits include high blood pressure, high cholesterol, diabetes, and atrial fibrillation (Afib), a form of irregular heartbeat that can lead to blood clots that may travel to the brain and cause a stroke. Researchers in Denmark have also found that children two to three inches shorter than their peers are more likely to have strokes as adults.

Preventive Steps

Cerebrovascular specialists at Harvard Medical School suggest taking seven steps to reduce the chances of a stroke.

• Lower your blood pressure – Aside from medications your doctor may prescribe, consume no more than about a half of a teaspoon of salt per day, eat more fresh fruits and vegetables along with fish two to three times per week, get more exercise, and quit smoking.

• Lose weight – Losing as little as ten pounds can reduce your stroke risk. Try to consume no more than 1,500 to 2,000 calories per day and exercise more, making activity part of your daily routine.

• Exercise – Aim for 150 minutes of moderate-intensity activity (brisk walking, water aerobics, bicycling) per week, or 75 minutes of vigorous-intensity exercise (jogging or running, swimming laps, brisk cycling). And add muscle-strengthening activities two to three times per week.

• Drink in moderation – Consume no more than one drink per day.

• Quit smoking – This is one of the most powerful lifestyle changes you can make to reduce the chances of a stroke.

• Treat diabetes – Use diet, exercise, and prescribed medications to keep blood sugar within the recommended range.

• Treat Afib – Your doctor may prescribe an anticoagulant to reduce your stroke risk from Afib.

Finally, if you suffer any signs of a stroke—weakness on one side of the body, numbness of the face, unusual or severe headaches, vision loss, unsteady walk—call 911 immediately.

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