In our continuing review of cardiovascular disease, we move on to the subject of stroke with information to share with you from many sources, but most especially from the American Heart Association. Stroke killed 154,350 people in the US in 1994 and accounted for 1 in every 15 deaths. Based on the Framingham Heart Study, about 500,000 Americans suffer a new or recurrent brain attack each year. Twenty-eight percent of people who have a stroke are under age 65, and for people over the age of 55, the incidence of stroke more than doubles in each successive decade. It is the leading cause of serious, long-term disability in the US. Again, according to the Framingham Heart Study, 31% of stroke patients survivors need help caring for themselves; 20% need help walking; and 71% have an impaired ability to work when examined an average of seven years later. Sixteen percent had to be institutionalized. With these facts in mind and knowing that we with diabetes have an additional risk factor for stroke, we need to arm ourselves with as much information as we can get to keep ourselves healthy. This article will describe what stroke is, the types of stroke, and the effects of having a stroke. Our next article will concentrate on the symptoms of stroke and the risk factors.
Stroke is a form of cardiovascular disease which effects the central nervous system, and occurs when a blood vessel bringing oxygen and nutriments to the brain bursts or is clogged by a clot or some other particle. Because of the rupture or blockage, a part of the brain is deprived of the blood it needs to function. The nerve cells in the affected area then can't function and will die in minutes. The devastating effects of stroke are often permanent because dead brain cells aren't replaced.
There are four main types of stroke: two caused by clots (ischemic strokes), and two caused by hemorrhage. Cerebral thrombosis and cerebral embolism are by far the most common, accounting for 70 to 80% of strokes. They are caused by clots that plug an artery. Cerebral and subarachnoid hemorrhages are caused by ruptured blood vessels, and these have a higher fatality rate than strokes caused by clots.
Cerebral thrombosis is the most common type of stroke. It occurs when a blood clot or thrombus forms and blocks blood flow in an artery bringing blood to the brain. This occurs more often in arteries damaged by atherosclerosis, a major risk factor for persons with diabetes. One identifying feature of cerebral thrombotic strokes is that they occur at night or first thing in the morning, when blood pressure is low. They're often preceded by a transient ischemic attack (TIA), or mini stroke.
Cerebral embolism accounts for 5 to 14% of strokes. This type of stroke occurs when a wandering clot (an embolus) or some other particle occurs in a blood vessel away from the brain, usually in the heart. The clot is carried by the bloodstream until it lodges in an artery leading to or in the brain, blocking the flow of blood. The most common cause of these emboli is blood clots that form during arterial fibrillation. In arterial fibrillation the two small upper chambers of the heart, the atria, quiver instead of beating effectively. Blood isn't pumped completely out of them when the heart beats, allowing the blood to pool and clot. About 15% of strokes occur in people with arterial fibrillation.
A subarchnoid hemorrhage occurs when a blood vessel on the surface of the brain ruptures and bleeds into the space between the brain and the skull (but not into the brain itself). Subarachnoid hemorrhages account for about 7% of all strokes.
Another type of stroke occurs when a defective artery in the brain bursts, flooding the surrounding tissue with blood. This is a cerebral hemorrhage. About 10% of all strokes result from cerebral hemorrhages. Hemorrhage, or bleeding. from an artery in the brain can be caused by a head injury or a burst aneurysm. Aneurysms are blood-filed pouches that balloon out from weak spots in the artery wall. They're often caused or aggravated by high blood pressure, a significant risk factor for those with diabetes. Aneurysms aren't always dangerous, but if one bursts in the brain, a stroke results.
When a cerebral or subarachnoid hemorrhage occurs, the loss of a constant blood supply means some brain cells no longer function. Another problem is that accumulated blood from the burst artery may put pressure on the surrounding brain tissue and interfere with how the brain functions. Severe or mild symptoms can result, depending on the amount of pressure. The amount of bleeding determines the severity of cerebral hemorrhages. In 50% of the cases, people with cerebral hemorrhages die of increased pressure on the brain. Those who live tend to recover more than those who have had strokes caused by clots. The reason for this is that when a blood vessel is blocked, part of the brain dies, and the brain can not regenerate. When a blood vessel in the brain bursts, pressure from the blood compresses part of the brain. If the person survives, gradually over time the pressure ebbs and the brain may return to its former state.
Stroke affects different people in different ways depending on the type of stroke and the area of the brain affected. It can affect the senses, speech, and the ability to understand language, behavioral and thought patterns, and memory. Paralysis on one side of the body is common. Stroke can also cause depression, as survivors have difficulty coping with their disabilities.
Stroke often causes people to lose feeling in an arm or leg, or suffer diminished sight in one eye. These losses result in loss of awareness, so stroke victims may forget or ignore their weaker side. As a result, they may ignore items put on their affected side, have trouble reading, or dress only one side of their bodies and think they are completely dressed. Bumping into furniture or door jambs is also common.
A stroke can affect vision, the sense of touch, the ability to sense movement, and thinking so that the perception of everyday objects may become altered. Survivors may not be able to recognize or understand familiar items the way they did before their stroke. When vision is affected, objects may appear closer or farther away then they really are, causing spills at the table or collisions when walking.
Usually stroke does not affect hearing, although persons who have had a stroke may have trouble understanding speech and/or verbalizing what they are thinking. This is called aphasia and it affects the ability to talk, listen, read ,and write. It usually occurs when a stroke weakens the right side of the body. Stroke can also affect muscles used in talking (those of the tongue, palate, and lips), and speech can therefore become slurred, slowed, and distorted. Dysarthria, or difficulty speaking clearly, may require a speech pathologist. Chewing and swallowing can also become a problem. One or both sides of the mouth can lack feeling, increasing the risk of choking.
Finally, a stroke can effect the ability to think clearly. Planning and carrying out even simple activities may become hard. Stroke survivors may not know how to start a task, confuse the sequence of logical steps to complete it, or forget how to do tasks they've done many times.
Next month we'll look at the signals of stroke and how they are diagnosed. Risk factors for stroke will also be outlined and we will end our review of stroke with rehabilitation strategies. For now, remember that when your doctor warns against hypertension and asks you change your eating patterns to lower cholesterol, he/she is trying to lower that all important risk factor for stroke. The sad, but true, fact is that diabetics share a higher risk factor for stroke than the rest of the population, and that diabetic women have a higher risk factor than men. So keep that blood pressure normal and your vessels clear. It isn't just that we want your blood glucose levels in the normal range to "beat the meter;" it is that we want you to enjoy a long and full life.
