Circulatory system

What is stroke?

A cardiovascular disease that affects blood vessels both leading to and within the brain, a stroke occurs when a blood vessel that carries oxygen and nutrients to the brain is either blocked by a clot or bursts. As a result, part of the brain is deprived of the blood and oxygen it needs and consequently, it starts to die.

When part of the brain dies from lack of blood flow, the part of the body it controls is affected. Strokes can cause paralysis, affect language and vision, and cause other problems.

What are the types of stroke?

Ischemic strokes

Accounting for between 83 and 88 percent of all strokes, ischemic strokes are caused by clots that block an artery. Clots known as cerebral thrombi create an obstruction and restrict blood supply to the brain.

Artherosclerosis is the underlying condition in which fatty deposits develop on surfaces lining vessel walls. It is these deposits that can lead to a thrombus, or blood clot. Cerebral thrombosis refers to a thrombus that develops at the clogged part of the vessel.

In addition to artherosclerosis, clots can form as a result of atrial fibrillation, a condition in which an irregular heartbeat can allow clots to form in the heart, dislodge and travel to the brain, resulting in what's known as cerebral embolism. Cerebral embolism refers generally to a blood clot that forms at another location in the circulatory system such as the heart and large arteries of the upper chest and neck. A cerebral embolism occurs when a portion of this clot dislodges and enters the bloodstream, traveling through the vessels in the brain until it reaches vessels too small to allow it to pass.¹

Hemorrhagic strokes

Bleeding or hemorrhagic strokes are caused by ruptured blood vessels. Hemorrhagic strokes are usually caused by two types of weakened blood vessels: aneurysms and arteriovenous malformations (AVMs).

An aneurysm refers to a ballooning of a weakened region of a blood vessel. If untreated, an aneurysm can continue to weaken until it ruptures and bleeds into the brain.

A cluster of abnormally formed blood vessels, an arteriovenous malformation (AVM) can also cause bleeding in the brain when one or more of the vessels ruptures.

Transient ischemic attacks

A third type of stroke, transient ischemic attacks (or TIAs) are minor or warning strokes. In a transient ischemic attack, typical stroke signs develop and conditions indicative of an ischemic stroke are present. In a transient ischemic attack, however, the obstruction occurs for a short time and tends to resolve itself. Although symptoms (see below) disappear after a short time, transient ischemic attacks are strong indicators of a possible major stroke and immediate steps should be taken to prevent a stroke.²

What are the risk factors for stroke?

Clinical research and study have identified several factors that increase the risk of stroke. While most of these factors refer to lifestyle habits that can be modified, treated or controlled, some factors cannot be changed. The best way to prevent a stroke is to reduce the number of factors that place you at risk.

Table 1. Risk Factors for Stroke

Treatable risk factors

Risk factors that cannot be treated

High blood pressure Blood pressure higher than 140/90 mm Hg is the most important risk factor for stroke. High blood pressure has no specific warning signs or symptoms; therefore, it's recommended that you have your blood pressure checked regularly. Smoking Smoking is a major and preventable risk factor for stroke. Nicotine and carbon monoxide in tobacco products reduce oxygen in the blood and damage the walls of blood vessels, thereby increasing the likelihood of clot formation. Certain types of birth control pills combined with smoking greatly increases women's risk of stroke. Diabetes While it is possible to treat diabetes, those with the disease are nevertheless at greater risk of stroke. Many people with diabetes are overweight and suffer from high blood pressure and high blood cholesterol. This increases the risk of stroke even more. Carotid or other artery disease The carotid arteries in the neck supply blood to the brain. Atherosclerosis may cause buildup of fatty deposits in the carotid arteries, causing them to narrow and a blood clot to form. Peripheral artery disease When vessels carrying blood to the arms and legs narrow as the result of a buildup of fatty deposits, a person's risk of carotid artery disease—and by extension, of stroke—increases. Atrial fibrillation An irregular heart rhythm causes the chambers of the heart to quiver rather than beat effectively. This can allow blood to pool and clot. If a clot dislodges and enters the bloodstream, it can lodge in an artery leading to the brain. When this occurs, a stroke results. Heart disease Those with coronary heart disease or heart failure are at high risk of stroke. An enlarged heart (dilated cardiomyopathy), heart valve disease and some types of congenital heart defects also increase the risk of stroke. Transient ischemic attacks These produce stroke-like symptoms but no lasting damage. Recognizing and treating transient ischemic attacks can reduce one's risk of a major stroke. Seek immediate emergency medical help if they occur. High blood cholesterol Blood cholesterol in excess of 240 mg/dL is a major risk factor for heart disease, which in turn raises the risk of stroke. Sedentary lifestyle and obesity Being obese or inactive—or both—increases the risk of high blood pressure, high blood cholesterol, diabetes, heart disease and stroke. It's important to exercise regularly: at least 30 minutes of activity on most or all days. Alcohol consumption Drinking an average of more than one alcoholic drink a day for women or more than two drinks a day for men can raise blood pressure and may increase risk for stroke. One drink is defined as 1½ fluid ounces (45 mL) of 80-proof spirits (i.e. bourbon, Scotch, vodka, gin, etc.) 1 fluid ounce (30 mL) 100-proof spirits, 4 fluid ounces (125 mL) wine, or 12 fluid ounces (355 mL) beer. Drug use Cocaine use has been tied to stroke and heart attack, some of which have been fatal, even for first-time users. Intravenous drug use also carries a high risk of stroke.

Increasing age Although strokes affect people of all ages, the risk increases with age. Gender Stroke is more common in men than in women. However, women account for more than half of all stroke deaths. Pregnant women are also at greater risk of stroke, as are women smokers who also take birth control pills or have high blood pressure. Heredity Stroke is common in families. Your risk increases if a parent, grandparent, or sibling has had a stroke. Ethnicity/Race Because Black people are more prone to high blood pressure, diabetes, and obesity, they are also at much higher risk for stroke. Prior stroke or heart attack People who have already suffered a stroke are at higher risk of having another. Those who have suffered a heart attack in the past are also at higher risk of having a stroke.

What are the signs of stroke?

By knowing the warning signs and risk factors for stroke, you can help yourself or a loved one reduce the risk of stroke. Acting quickly when symptoms occur can mean the difference between surviving a stroke and minimizing long-term disability and being devastated—mentally or physically. It can even help save a life. Seek immediate emergency medical help if any of these symptoms occur:

• sudden numbness or weakness of the face, arm or leg, especially on one side of the body
• sudden confusion
• difficulty understanding
• sudden trouble seeing in one or both eyes
• sudden trouble walking, dizziness, loss of balance or coordination
• sudden, severe headache with no known cause
• difficulty speaking or completing sentences
• difficulty raising arms over one's head

Ask the person to smile, utter a complete sentence, and to raise his/her arms above his/her head. If he/she is unable to complete these three tasks, there is reason to believe he/she may be having a stroke. Seek medical attention immediately.

How is stroke diagnosed?

When someone exhibits the symptoms of stroke as outlined above or the symptoms of an ischemic transient attack, a doctor will consult with the patient, and will make a diagnosis based on information gathered and on the events that have occurred. The doctor will typically:

• get a patient's medical history
• conduct a physical and neurological examination
• request blood tests
• request and study the results of other diagnostic tests to determine how the brain looks, how well it is working, and how it is getting its blood supply. These tests outline the area of the brain that has been injured.
• request computed tomography (CT scan)

Imaging tests

Computed tomography (also known as a CT or CAT scan) uses radiation—much in the same way an x-ray machine works—to create a picture of the brain. The patient lies down on a table and is slid into a hollow x-ray tube. The tube rotates around the patient's body and projects a fine beam of x-rays onto the patient's head. Radiation which is not absorbed is recorded and subsequently digitized by the computer to generate hundreds of cross-sectional images—called "slices"—of the brain. The slices are then processed by a computer, allowing the doctor to see the soft tissues of the brain in great detail and in three dimensions. The results of the CT scan provide key information about the location and the cause of the stroke, as well as the extent of the brain injury. While a CT scan may seem frightening — particularly to claustrophic patients—it is a safe and painless test.

Similar to a CT scan, magnetic resonance imaging (or MRI) uses a large magnetic field to produce an image of the brain to reveal the location of the brain injury. The patient again lies inside a hollow tube—itself a large magnet—while a radio wave antenna (called a coil) is used to send pulses of radio waves to the body. The coil is also designed to receive radio signals back from the body. The returning radio signals are then digitized by a computer. When a patient is first slid inside the MRI tube, he or she may hear sounds similar to hammering while the scanner prepares to scan and take pictures. During the hammering, it's especially important not to move, as this may blur the pictures. It isn't uncommon to feel vibrations and a slight movement of the table during an MRI examination. In some cases, patients may be given an injection of what's known as a contrast agent, a substance intended to improve certain types of images. MRI examinations and contrast agents are entirely safe.

Electrical activity tests

During an electroencephalogram (EEG), small electrodes are placed on a patient's scalp to detect and record electrical impulses. A plotter then prints out these impulses as brain waves.

An evoked response test is used to measure how the brain responds to different sensory information. Electrodes are used to record electrical impulses related to hearing, vision, and body sensation.

Blood flow tests

Blood flow tests are used to determine how the brain is getting its blood supply. Most blood flow tests use sonography, also known as ultrasound technology.

During a blood flow test, the sonographer places a probe over the artery suspected of having caused the stroke. Such arteries are usually in the neck or at the base of the skull. The sonographer is then able to determine the blood flow through the artery.

Tests such as B-mode imaging, Doppler testing, and duplex scanning give more detailed information about arteries' condition.

In angiography (also known as arteriography or an arteriogram), dyes are injected into blood vessels and various x-ray pictures are taken. By giving a picture of blood flow through vessels, angiography allows a doctor to evaluate the size and location of blockages. Angiography is particularly useful prior to surgery because it allows doctors and surgeons to diagnose aneurysms and malformed blood vessels.³

Acute and preventive treatments

Because the mechanisms and causes of strokes are different, it only follows that treatments differ depending on the type of stroke. Ischemic strokes are treated by removing the obstruction (blood clot) and restoring blood flow to the brain. By contrast, in hemorrhagic strokes, doctors introduce an obstruction to prevent aneurysms and/or arteriovenous malformations from rupturing and bleeding.⁴

Table 2. Actue and Preventive Treatments for Stroke

Type of stroke	Acute treatment	Preventive treatment
Ischemic	Clot-busters, e.g., tPA Although only 3 to 5 percent of people who suffer a stroke reach the hospital in time to be considered for such treatment, clot busters such as tPA nevertheless remain the most promising treatment for ischemic stroke. Clot busters must be administered within a three-hour window from the onset of symptoms to work best.	Anticoagulants/antiplatelets Antiplatelet agents such as aspirin, and anticoagulants such as warfarin interfere with the blood's ability to clot and can play an important role in preventing stroke. Carotid endarterectomy Carotid endarterectomy is a procedure in which blood vessel blockage is surgically removed from the carotid artery. Angioplasty/stents Doctors sometimes use balloon angioplasty and implantable steel screens called stents to treat cardiovascular disease in which mechanical devices are used to remedy fatty buildup clogging the vessel.
Hemorrhagic	Surgical Intervention Surgical treatment is often recommended for hemorrhagic strokes and involves either placing a metal clip at the base of the aneurysm or removing the abnormal vessels which make up an arteriovenous malformation. Endovascular Procedures Less invasive than surgical intervention, endovascular procedures involve the use of a catheter introduced through a major artery in the leg or arm. The catheter is then guided to the aneurysm or arteriovenous malformation where it deposits a mechanical agent, such as a coil, to prevent rupture.

Source: Acute and Preventive Treatments. American Heart Association. (2004)

Effects of stroke

When the brain is deprived of blood and oxygen, it eventually dies and the part of the body controlled by that part of the brain is affected and may no longer function as expected. For instance, if a stroke occurs in the occipital (back) region of the brain, it's likely a patient will suffer some disability involving vision. The effects of stroke largely depend on the location of the blood clot as well as on the extent of the injury to brain tissue.⁵

While the effects of stroke depend on a number of factors, including the location of the obstruction and the extent of the injury to brain tissue, it's important to remember that each respective hemisphere of the brain controls the opposite side of the body. What does this mean? Essentially, a stroke that occurs on one side of the brain will have an effect on the side of the body it controls.

Table 3. Effects of Stroke

Right brain	Left brain
A stroke affecting the right side of the brain, for instance, will impact the right side of the face and the left side of the body, producing any or all of the following: paralysis on the left side of the body impaired vision changes in behavior characterized by a quick and inquisitive behavioral style memory loss	A stroke affecting the left side of the brain will impact the left side of the face and the right side of the body, producing any or all of the following: paralysis on the right side of the body speech impediment/language problems (aphasia) changes in behavior characterized by a slow, cautious behavioral style memory loss

Source: Acute and Preventive Treatments. American Heart Association. (2004)

Recovering from stroke

Taking place in acute care facilities, outpatient facilities, long-term care facilities, rehabilitation hospitals or in a patient's home, rehabilitation is critical in the recovery of many patients. This is because certain conditions and the other effects of stroke mean patients must change, relearn, or redefine the ways in which they perform certain tasks.

Rehabilitation begins when a doctor determines a patient is mentally stable and able to reap the benefits of a carefully designed rehabilitation program. Rehabilitation programs bring together specialists from many disciplines, including:

Rehabilitation nursing Physical and/or occupational therapy Speech-language pathology and/or audiology Recreational therapy Nutritional care

Rehabilitation counseling Social work Psychiatry/psychology Patient/family education Support groups

Rehabilitation works to restore patients' independence by teaching:

• self-care skills such as feeding, bathing, grooming, and dressing
• mobility skills such as walking, self-propelling a wheelchair, and transferring
• communication skills (particularly for aphasic patients)
• cognitive skills to improve memory and problem-solving ability
• social skills to better integrate and interact with others

Although rehabilitation does not reverse the effects of stroke, its aim is to allow recovering stroke patients to continue their daily activities by building strength and capability; it shows patients how to manage around the effects of stroke.

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1. What are the types of stroke? American Heart Association. 2004.
2. What are the types of stroke? American Heart Association. 2004.
3. Diagnosis. American Heart Association. 2004.
4. Acute and Preventive Treatments. American Heart Association. 2004.