Stroke

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Stroke

A stroke, also called a cerebral vascular accident or CVA, is a sudden, often crippling disturbance in blood circulation in the brain. Interruption in blood circulation may be the result of a burst artery or of an artery that has become closed off because a blood clot has lodged in it. Blood circulation to the area of the brain served by that artery stops at the point of disturbance, and the brain tissue beyond that is damaged or dies. This is one reason why prompt treatment can have such a dramatic effect on final recovery from a stroke

Statistics

As of January 2006, some important stroke statistics are:

About 700,000 people in the United States experience a new (500,000 people) or recurrent (200,000 people) stroke each year;
According to the American Heart Association (AHA), stroke is the third leading cause of death in the United States (behind heart disease and cancer) and the leading cause of long-term disability;
Stroke kills between 150,000 and 175,000 U.S. citizens each year (according to the AHA), or almost one out of four stroke victims;
Currently, about three million Americans are permanently disabled from stroke;
In the United States, according to the AHA, stroke costs about $40 billion per year in direct costs and loss of productivity;
Two-thirds of strokes occur in people over age 65 years of age;
Strokes affect men more often than women, although women are more likely to die from a stroke (in 2004, about 60% of women who suffered a stroke, died from it);
From 1994 to 2004, the death rate from stroke decreased by about 18%, and the actual number of stroke deaths decreased by about 0.7%; and
Strokes affect blacks more often than whites, and are more likely to be fatal among blacks.

The death rate from stroke has been steadily declining since the early 1970s. A great part of this success has been the efforts of various agencies to make physicians and the general population aware of the danger of high blood pressure. The importance of regular blood pressure checks has begun to infiltrate the public’s knowledge. High blood pressure, or hypertension, is the most important risk factor for stroke.

The brain and blood vessels

The brain requires a constant and steady infusion of blood to carry out its functions. Blood delivers the

oxygen and nutrients needed by the brain cells, so the circulation to the brain is copious. The carotid arteries on each side of the throat and the vertebral arteries in the back of the neck carry blood to the brain. As the arteries enter the brain they begin to divide into smaller and smaller vessels until they reach the microscopic size of capillaries. The venous system to drain blood from the brain is equally large.

A burst blood vessel, which may occur in a weak area in the artery, or a blood vessel that becomes plugged by a floating blood clot no longer supplies blood to the brain tissue beyond the point of the occurrence. The effect of the interruption in circulation to the brain depends upon the area of the brain that is involved. Interruption of a small blood vessel may result in a speech impediment or difficulty in hearing or an unsteady gait. If a larger blood vessel is involved the result may be the total paralysis of one side of the body. Damage to the right hemisphere of the brain will result in injury to the left side of the body, and vice versa. The onset of the stroke may be so sudden and severe that the patient is literally struck down in his tracks. Some patients have early warnings that a stroke may be developing, however.

These people have what is called transient ischemic attacks, or TIAs. These usually result when a cerebral artery is closing because of the build-up of fatty deposits inside the vessel, a condition called atherosclerosis. Slight disturbances in circulation occur at intervals in such a case and the patient will experience momentary symptoms such as unexplained dizziness, blurring of vision, loss of hearing, or other event. It is important in this case to consult a physician so that proper testing can be carried out to determine the cause of the TIAs and steps taken to prevent development of a full stroke.

A stroke that results from a burst blood vessel is called a hemorrhagic stroke. In addition to the damage to brain tissue caused by lack of blood, damage may be brought about by the blood clot formed from the bleeding. The doctor may need to surgically remove the clot to relieve pressure on the brain.

A stroke caused by a clot sealing a blood vessel is called a thrombotic stroke, a derivation of the technical name for a clot, a thrombus. The clot can be formed elsewhere in the body and be carried in the circulating blood until it reaches a vessel too small for it to pass through. At that point it will lodge and dam up the flow of blood, inflicting damage on the tissue beyond the blockage. A thrombotic stroke, if attended quickly, sometimes can be minimized in terms of damage.

People who are known to form blood clots in their circulatory system can be given medications to prevent it. In addition, current therapy includes medications that can be given to dissolve clots (a process called thrombolysis) and remove the barrier to blood flow. Some brain function may be preserved in this way that would otherwise be lost if the clot is allowed to remain in place.

Not all vascular events bring on a stroke. Pathologists often find areas in the brain in which a small blood vessel has ruptured but the patient was not reported to have suffered a stroke. Blood vessels that form what is called collateral circulation often make up for the blood circulation lost by a plugged or ruptured vessel. Collateral circulation is carried by other vessels that help to supply blood to a given area of the brain.

Strokes can be prevented by effective treatment of high blood pressure and by taking a small-sized aspirin tablet every day (under a doctor’s direction), for those who can tolerate such medication. The aspirin helps to prevent clot formation and a number of clinical trials have shown it to be effective in stroke reduction.

Treatment

recovery from a stroke varies from one person to the next. Swift treatment followed by effective physical therapy may restore nearly full function of an affected area of the body. Some individuals have experienced severe enough damage that their recovery is minimal and they may be confined to a wheelchair or bed for the remainder of their lives.

Because stroke is a major cause of disability and death, much research effort is being put into this topic. Research is looking at a variety of materials to improve the odds of stroke patients. Some of these materials are:

Substances able to protect the cells from certain events, called neuroprotective, that occur after stroke, which result in increasing damage to brain tissue.

Medications (vasodilators) that work to increase the diameter of blood vessels, thereby allowing a greater flow of blood to areas served by those vessels, which hold the potential to increase blood flow and therefore oxygen delivery to areas of the brain threatened by or injured by stroke.

Genetic engineering, which holds the future hope of allowing genes to be inserted in the brain, used to provoke brain cells into producing chemicals that could be either neuroprotective or perhaps reparative to areas damaged by stroke.

Studies into animal hibernation that are used to increase understanding of how a hibernating animal can have decreased blood flow to the brain without brain damage.

Specialized magnets used to ascertain whether application of a magnetic field to areas of the brain damaged by stroke could potentially help stroke victims recapture functioning to those areas.

Rehabilitation

after the stroke has occurred and the brain has been damaged, treatment is aimed at rehabilitation. Rehabilitation refers to a comprehensive program designed to regain function as much as possible and compensate for permanent losses. Approximately 10% of stroke survivors are without any significant disability and are able to function independently. Another 10% are so severely affected that they must remain institutionalized for severe disability. The remaining 80% can return home with appropriate therapy, training, support, and care services.

Rehabilitation is coordinated by a team of medical professionals and may include the services of a neurologist, a physician who specializes in rehabilitation medicine (physiatrist), a physical therapist, an occupational therapist, a speech-language pathologist, a nutritionist, a mental health professional, and a social worker. Rehabilitation services may be provided in an acute care hospital, rehabilitation hospital, long-term care facility, outpatient clinic, or at home.

KEY TERMS

Cerebral —Refers to the brain. Cerebral vascular is reference to the blood supply to the brain.

Death rate —The number of deaths from a given cause per specified number of people. The death rate from a disease may be given as 30 per 10,000 population.

Pathologist —A physician who studies the disease process, learning by conducting autopsies on people who have died.

The rehabilitation program is based on the patient’s individual deficits and strengths. Strokes on the left side of the brain primarily affect the right half of the body, and vice versa. In addition, in left-brain dominant people, who constitute a significant majority of the population, left-brain strokes usually lead to speech and language deficits, while right brain strokes may affect spatial perception. Patients with right brain strokes may also deny their illness, neglect the affected side of their body, and behave impulsively.

Rehabilitation may be complicated by cognitive losses, including diminished ability to understand and follow directions. Poor results are more likely in patients with significant or prolonged cognitive changes, sensory losses, language deficits, or incontinence.

Damage from stroke may be significantly reduced through emergency treatment. Knowing the symptoms of stroke is as important as knowing those of a heart attack. Patients with stroke symptoms should seek emergency treatment without delay, which may mean dialing the emergency telephone number 911 rather than their family physician.

Reducing the risks

The risk of stroke can be reduced through the following lifestyle changes:

Stop smoking,
Control blood pressure,
Get regular exercise,
Keep body weight down,
Avoid excessive alcohol consumption, and
Get regular checkups and follow the doctor’s advice regarding diet and medicines.

Treatment of atrial fibrillation may significantly reduce the risk of stroke. Preventive anticoagulant therapy may benefit those with untreated atrial fibrillation. Warfarin (Coumadin^®) has proven to be more effective than aspirin for those with higher risk.

Screening for aneurysms may be an effective preventive measure in those with a family history of aneurysms or autosomal polycystic kidney disease, which tends to be associated with aneurysms.

See also Thrombosis.