What Causes Strokes
Today I found out what causes a stroke.
A stroke, known in the medical field as a cerebral vascular accident (CVA) or brain attack, is more or less a “heart attack” for the brain. Like any organ in the body, the brain needs blood to supply it with oxygen and nutrients. Should this blood flow become blocked by a clot or emboli, or the rupture of a blood vessel, the cells that occupy that area of the brain begin to die. Although every person has a different presentation, some of the most common symptoms of a stroke include trouble speaking, slurred speech, weakness or paralysis of one or both sides of the body, altered mental status, vision problems, or headache.
There are two types of strokes: Ischemic and Hemorrhagic. Ischemic strokes are the most common type, accounting for nearly 80% of all strokes. This type of stroke is caused by a blockage of an artery that leads to the brain, or smaller specific area of the brain. “Ischemia” simply means a deficiency of blood supply produced by vaso-constriction or local obstacles to the arterial flow, thus, the term “Ischemic stroke”. Blood-clots are the leading cause of these blockages; however, anything that can block the blood vessel like an air bubble, a tumor, constriction of the blood vessel, or (rarely) a foreign object, can result in an Ischemic stroke.
Treatment for ischemic strokes involves removing or reducing the blockage. If this is not done quick enough and the cells in that area of the brain die, the only option left is physical therapy to try and increase the function of the body area affected. If doctors have the opportunity to treat the stroke in a timely manner, there are two therapies they can try. The first is to use thrombolitics (clot dissolving drugs) like Activase (Alteplase). Using a protein called “tissue plasminogen activator” (tPA) this type of drug breaks down clots allowing blood to begin flowing again.
Using this drug has its own problems. The first is that they require administration within 3 hours of the onset of symptoms. Although some studies have suggested that doctors can give the drug, under certain circumstances, within 6 hours. The second complication is that this drug will break down all the clots in your body, not just the ones in your brain. So as you would expect, the chance of unwanted bleeding is very good.
The second treatment attempts to get around the unwanted bleeding problem. It uses a type of interventional radiology (basically an image guided surgery) called Local Intra-Arterial Thrombolysis. This is basically taking a tPA and, using a wire guided delivery system, putting the drug directly on the unwanted clot. This treatment also comes with a short window of effectiveness and is best used within 4 hours of the onset of symptoms.
Hemmorhagic strokes account for the other 20% of strokes. This type also results in blood flow to an area of the brain to be interrupted. Instead of the artery being blocked, though, it bursts open and the blood leaks out and does not get transported to the cells of the brain.
Hemorhagic strokes come in two varieties: intracerebral and subarachnoid. Intracerebral simply means that an artery within the brain itself ruptures. Not only do the cells downstream of the break begin to die, but blood gets introduced into the brain and causes the area around the bleed to compress the brain tissue resulting in further damage. Subarachnoid hemorhage is also a rupture of an artery within the skull. The difference is where the bleed occurs. Instead of happening within the brain itself, it happens in the area surrounding it. The skull does not allow for the blood to escape so it puts pressure on the brain causing damage.
Doctors have two choices when it comes to treating a hemorrhagic stroke: fix it with surgery, or let it resolve on its own. In an effort to keep this article less than the short lifetime a neurosurgeon goes to school, I will not go in to all the factors that lead a doctor to decide between surgery or the “wait and see” approach. I will simply say that if surgery can be avoided, it will be. If it can’t, then hope your surgeon has steady hands or is using remote hands via a robotic aid device. No one wants shaky shakerson going at their brain with a scalpel!
- Medical documentation of strokes can be traced all the way back to Hippocrates. He referred to the problem as “apoplexy”, meaning “struck down by violence”. It was thought he chose this term because the victims would often suddenly become paralyzed on one side of the body or have a sudden change in their mental status. For centuries it wasn’t known what the cause of apoplexy was. Not until the 17th century was it known that an apoplexy could be caused by either a brain bleed or a blockage of the arteries supplying the brain. The classification of the two different types wasn’t categorized until 1928.
- In the United States, strokes are the third leading cause of death at approximately 140,000 per year. 795,000 people will have a stroke each year, approximately one every 40 seconds. World-wide approximately 15 million people have a stroke annually. Five million of them die and another five million are permanently disabled.
- After the age of 55, the risk of having a stroke doubles every 10 years.
- Smoking doubles your chance of having a stroke. A heart condition known as atrial fibrillation increases your chance 500%.
- High blood pressure is the most important risk factor. It is thought that it contributes to 12.7 million strokes per year world wide.
- A “transient ischemic attack” (TIA), also known as a mini-stroke, is when blood flow to the brain is interrupted for only a brief time period. The victim will have stroke-like symptoms that usually resolve within 24 hours. This affliction is usually a warning sign that a stroke will happen in the near future.
- A study done by the American Heart Association showed that if you are a woman and had heart disease, you were more likely to have a mother who had a stroke, then a father who did. The point being that there could be a gender link between the heritability of vascular disease.
- The Strokes are a band from New York, led by singer Julian Casablancas and guitarist Albert Hammond. They seem to be more popular in Britain then the United States. After hearing one of their songs, I believe it is similar to the way David Hasselhoff was big in Europe.
If you liked this article, you might also like: How a Heart Attack Works
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