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A cerebrovascular disease is one caused by arteries blocked by a blood clot, bleeding in or around the brain caused by a ruptured blood vessel, and any change in the brain’s blood vessels that alters the normal flow of blood. “Cerebro” refers to the brain and “vascular” pertains to blood vessels. Loss of blood flow to the brain for even a short time can damage or kill brain cells. The more brain cells that are affected, the greater the likelihood a stroke will cause permanent disability or death.
Your circulatory system delivers blood to all organs and tissues of your body. Your heart is the pump, and your blood vessels are the plumbing. It’s a closed system: Blood pumped from the heart eventually returns to the heart, where it is sent to the lungs for oxygen and back to the heart to be pumped through the system again. The blood vessels that deliver oxygenated blood from the heart to your tissues and organs are called arteries; those that return oxygen-depleted blood to your heart are called veins. Veins are not usually involved in a common cerebrovascular disease.
Cerebrovascular Disease Caused by a Blood Clot
About 87 percent of all strokes are ischemic. These strokes most often occur when an artery bringing blood to the brain becomes blocked, stopping blood flow. Less frequently, a severe drop in blood pressure causes an ischemic stroke.
Brain cells (neurons) rely on a constant stream of blood supplying oxygen and nutrients to operate normally. When blood flow is interrupted for more than a few seconds, the neurons begin to malfunction. If blood flow is not restored quickly, the neurons begin to die. This is why immediate medical evaluation and treatment is absolutely essential for people who are experiencing symptoms of a stroke.
There are two types of ischemic strokes:
Many people wonder, “What is an embolism?” Sometimes a clot that develops elsewhere in the body—typically the heart, aorta, or carotid arteries in the neck—breaks off and travels in the bloodstream to the brain. This type of clot is called an embolus. When an embolus lodges in a brain artery, stopping blood flow, it produces an embolism that causes an embolic stroke. In addition to a blood clot, an embolus can be an air bubble or piece of debris.
When a clot (thrombus) develops in a narrowed part of an artery—typically from fatty buildup in the arteries (atherosclerosis) of the brain or neck—the result is a thrombotic stroke. This type of stroke comprises about 50 percent of all strokes. A thrombotic stroke is further differentiated as a large-vessel or small-vessel thrombosis, depending on the size of the artery in which the thrombus occurs. A small-vessel thrombotic stroke deep within the brain is also called a lacunar stroke.
Cerebrovascular Disease Caused by Bleeding in the Brain
When a weakened artery in the brain ruptures, the result is a hemorrhagic stroke. Blood flowing into the brain compresses the tissue and kills brain cells.
About 75 percent of hemorrhagic strokes (13 percent of all strokes) occur within the brain itself. These are called intracerebral hemorrhages.
In the other 25 percent, the bleeding occurs in the space between the brain and the skull. These are known as subarachnoid hemorrhages.
The most common cause of a spontaneous subarachnoid hemorrhage is a ruptured aneurysm. An aneurysm is a balloon-like outpouching from a weakened area in the wall of an artery, typically at the base of the brain. Aneurysms are present at birth. Cerebral aneurysms are more likely to rupture in patients with a family history of ruptured aneurysms, and in those who currently smoke, have a large aneurysm, or suffer from high blood pressure.
The Heart-Brain Connection
People with cerebrovascular disease caused by atherosclerosis are at risk of having atherosclerosis elsewhere in the body. When atherosclerosis affects arteries supplying blood to the brain or inside the brain, the result is a stroke. When atherosclerosis affects the arteries supplying blood to the heart muscle (coronary artery disease, or CAD), the result is a heart attack. The same disease process can affect the arms and legs (peripheral arterial disease, or PAD) or the kidneys (renovascular disease).
If you have had an ischemic stroke, or have experienced symptoms of a transient ischemic attack (TIA) that indicate increased risk for stroke, you have a 20 to 40 percent chance of having CAD. In fact, two to five percent of ischemic stroke survivors have a fatal heart attack less than 90 days after their stroke. If you are under the age of 60 and have a TIA, your risk of having a heart attack is 15 times that of a healthy person your age.
Similarly, CAD is a risk factor for stroke, since patients with CAD may also have cerebrovascular disease. In addition, they are at increased risk for strokes caused by blood clots forming in the heart and traveling to the brain. While about 47 percent of all deaths from cardiovascular disease are due to CAD, about 16 percent are due to stroke.