A stroke is the sudden death of brain cells in a localized area due to inadequate blood flow.A stroke occurs when blood flow is interrupted to part of thebrain. Without blood to supply oxygen and nutrients and to remove waste products, brain cells quickly begin to die. Death of brain cells triggers a chainreaction in which toxic chemicals created by cell death affect other nearbycells. This is one reason why prompt treatment can have such a dramatic effect on final recovery.
Depending on the region of the brain affected, a stroke may cause paralysis,speech impairment, loss of memory and reasoning ability, coma, or death. A stroke is also sometimes called a brain attack or a cerebrovascular accident (CVA).
Some important stroke statistics:
- More than half a million people in the United States experience a new or recurrent stroke each year
- Stroke is the third leading cause of death in the United States and the leading cause of disability
- Stroke kills about 150,000 Americans each year, oralmost one out of three stroke victims
- Three million Americans are currently permanently disabled from stroke
- In the United States, strokecosts about $30 billion per year in direct costs and loss of productivity
- Two-thirds of strokes occur in people over age 65
- Strokes affect men more often than women, although women are more likely to die from a stroke
- Strokes affect blacks more often than whites, and are more likelyto be fatal among blacks.
Stroke is fatal for about 27% of white males, 52% of black males, 23% of white females, and 40% of black females. Stroke survivors may be left with significant deficits. Emergency treatment and comprehensive rehabilitation can significantly improve both survival and recovery.
Stroke risk increases with:
- high blood cholesterol level
- high red blood cell count
- cigarette smoking (especially if combined with the use of oral contraceptives)
- low level of physical activity
- alcohol consumption above two drinks per day, or useof cocaine or intravenous drugs.
There are four main types of stroke: cerebral thrombosis, cerebral embolism,subarachnoid hemorrhage, and intracerebral hemorrhage.
Cerebral thrombosis and cerebral embolism are caused by blood clots that block an artery supplying the brain, either in the brain itself or in the neck. These account for 70-80% of all strokes.
Clots most often form due to "hardening" (atherosclerosis) of brain arteries.Cerebral thrombosis is often preceded by a transient ischemic attack, or TIA, sometimes called a "mini-stroke." In a TIA, blood flow is temporarily interrupted, causing short-lived stroke-like symptoms.
Cerebral embolism occurs when a blood clot from elsewhere in the circulatorysystem breaks free. If it becomes lodged in an artery supplying the brain, either in the brain or in the neck, it can cause a stroke. The most common cause of cerebral embolism is atrial fibrillation, a disorder of the heart beat.
Subarachnoid hemorrhage and intracerebral hemorrhage occur when a blood vessel bursts around or in the brain, either from trauma or excess internal pressure. The vessels most likely to break are those with preexisting defects suchas an aneurysm. An aneurysm is a "pouching out" of a blood vessel caused by aweak arterial wall. Brain aneurysms are surprisingly common. According to autopsy studies, about 6% of all Americans have them. Aneurysms rarely cause symptoms until they burst.
Intracerebral hemorrhage affects vessels within the brain itself, while subarachnoid hemorrhage affects arteries at the brain's surface, just below the protective arachnoid membrane.
Symptoms of an embolic stroke usually come on quite suddenly and are at theirmost intense right from the start, while symptoms of a thrombotic stroke come on more gradually. Symptoms may include:
- Blurring or decreased vision in one or both eyes
- Severe headache, often described as "the worstheadache of my life"
- Weakness, numbness, or paralysis of the face,arm, or leg, usually confined to one side of the body
- Dizziness, loss of balance or coordination, especially when combined with other symptoms.
Stroke is a medical emergency requiring immediate treatment. Prompt treatmentimproves the chances of survival and increases the degree of recovery that may be expected. A person who may have suffered a stroke should be seen in a hospital emergency room without delay. Treatment to break up a blood clot, themajor cause of stroke, must begin within three hours of the stroke to be effective. Improved medical treatment of all types of stroke has resulted in a dramatic decline in death rates in recent decades. In 1950, nine in ten died from stroke, compared to slightly less than one in three today.
Emergency treatment of stroke from a blood clot is aimed at dissolving the clot. This "thrombolytic therapy" is currently performed most often with tissueplasminogen activator, or t-PA. t-PA must be administered within three hoursof the stroke event. Emergency treatment of hemorrhagic stroke is aimed at controlling intracranial pressure.
Surgery for hemorrhage due to aneurysm may be performed if the aneurysm is close enough to the cranial surface to allow access. Ruptured vessels are closed off to prevent rebleeding. For aneurysms that are difficult to reach surgically, endovascular treatment may be used. In this procedure, a catheter is guided from a larger artery up into the brain to reach the aneurysm. Small coils of wire are discharged into the aneurysm, which plug it up and block off blood flow from the main artery.
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 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 carehospital, rehabilitation hospital, long-term care facility, outpatient clinic, or at home.
The rehabilitation program is based on the patient's individual deficits andstrengths. 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 911 rather than their family physician.
The risk of stroke can be reduced through lifestyle changes:
- Stop smoking
- Control blood pressure
- Get regular exercise
- Keepbody weight down
- Avoid excessive alcohol consumption.
- 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 witha family history of aneurysms or autosomal polycystic kidney disease, which tends to be associated with aneurysms.