How Does a Stroke Occur?

Who has Strokes

Strokes most often occur in the elderly, people with high blood pressure, obesity and diabetes. Smoking and alcohol use also increase the risk for strokes. Diets high in cholesterol can contribute to the build of blockages in the arteries. Lack of exercise can lead to hypertension and poor circulation, both of which can contribute to strokes. Patients suffering from atrial fibrillation (irregular pulse) are the most at risk to suffer from a stroke.

Bleeding Into the Brain

There are two types of strokes. The first is a hemorrhagic stroke. This occurs when a blood vessel inside the brain ruptures and causes bleeding. This type of stroke is usually the result of a head injury. Another reason a hemorrhagic stroke can occur is if the blood vessels grow too thin--this may cause a bulge, called an aneurysm. Aneurysms can develop slowly over several years and will eventually grow so weak that they break, causing bleeding. If the bleeding is near the surface of the brain it is called a subarachnoid or a subdural hemorrhage. If the bleeding is deeper inside the brain it is called a intracerebral hemorrhage. Hemorrhagic strokes are less common than ischemic strokes, but they are more likely to result in death.

Blocked Artery

The second type of stroke is an ischemic stroke. This results when an artery in the brain becomes blocked. One possible cause of the blockage is thickening of the blood resulting in a blood clot. The clot can travel through the circulatory system until it becomes lodged in a narrow artery in the brain. The other cause is if the arteries become weakened, narrowed or hardened. Cholesterol can form plaque that sticks to the walls of the artery, gradually making the artery narrower over time. Plaque usually builds up in the arteries of the neck, so when they become fully blocked one entire hemisphere of the brain is affected by the stroke.

Brain Damage

Without blood oxygenating the brain, the cells suffer damage. In an attempt to compensate, the body will enlarge other nearby blood vessels to try and restore blood flow to the affected areas. If blood flow is blocked for more than four minutes brain cells begin to die. The brain can not regenerate dead brain cells. Because different areas of the brain control different functions, symptoms of a stroke may vary. Paralysis may occur on one side of the body, there may be blurred or lost vision, trouble communicating or drooping on one side of face. Even if treated quickly the patient may still suffer long term disability.