Stroke From Carotid Stenosis
A stroke is the death of brain tissue that occurs when the brain does not get enough blood to supply its need for oxygen. A stroke from carotid stenosis occurs when the arteries supplying the brain are narrowed and blood flow to the brain is impaired.
What is going on in the body?
A stroke from carotid stenosis is classified as an ischemic stroke, which means it is caused when the blood supply to the brain is interrupted. Plaque, or firm layers of cholesterol, builds up on the internal surface of the carotid arteries which bring blood and oxygen to the brain.
The plaque buildup causes a narrowing of the blood vessels. The narrowing of these blood vessels, known as carotid stenosis, causes a decreased blood flow to the brain. The brain cells then die from lack of oxygen. The products released when cells die cause swelling in the brain. Since the skull allows essentially no room for expansion, this swelling can damage the brain tissue even further..
Stenosis of the carotid arteries may occur over many years. When the surface of the plaque in an artery cracks or ruptures, clot-forming substances in the blood rapidly gather at the site. A clot, called a thrombus, then forms in the artery. The clot reduces blood flow and deprives the brain of blood, oxygen, and nutrients. This can lead to a stroke, or brain attack. If part of the clot breaks off, it can be carried by the bloodstream to block smaller arteries in the brain. The portion of the clot that breaks off is called an embolus.
What are the causes and risks of the condition?
A stroke from carotid stenosis is caused by narrowing of one or more of the arteries supplying the brain with oxygen-rich blood. The narrowing is caused by the buildup of plaque on the inner walls of arteries supplying the brain. As plaque builds up in a person's arteries, the blood flow is interrupted and the person's risk of stroke increases.
The person's risk of stroke from carotid stenosis is increased if other risk factors for stroke are also present. The American Heart Association has recently issued guidelines for stroke prevention. The guidelines discuss risk factors for stroke in 3 categories: nonmodifiable, well-documented modifiable, and less well-documented or potentially modifiable.
The nonmodifiable factors are ones that cannot be changed by the individual and include:
- increasing age. A person's risk of stroke doubles each year after age 55.
- race. Strokes occur approximately twice as often in blacks and Hispanics as they do in whites.
- gender. Men have a 50% higher chance of stroke than women
- family history of stroke or transient ischemic attack (TIA). A TIA is a short, reversible episode of stroke-like symptoms that may serve as an early warning sign of stroke.
Well-documented modifiable risk factors are those that can be changed by the individual in conjunction with his or her healthcare provider. These factors are linked to stroke by strong research findings, and there is documented proof that changing the risk factor lowers a person's risk of stroke. These factors include:
- high blood pressure
- asymptomatic carotid stenosis, or narrowing of one of the arteries in the neck
- sickle cell anemia, a blood disorder that forms abnormal red blood cells
- high cholesterol levels in the blood, including total cholesterol and LDL, "bad" or "lethal" cholesterol. Low levels of HDL, "good" or "healthy" cholesterol, are also cause for concern.
- atrial fibrillation, an abnormal heart rhythm
Less well-documented or potentially modifiable risk factors for stroke are those that have weaker evidence that the risk factor is linked to stroke or that modifying the risk factor will prevent stroke . These factors include:
- sedentary lifestyle
- alcohol abuse
- high blood levels of homocysteine, a blood component sometimes associated with a higher risk of stroke
- drug abuse
- blood disorders, such as blood that clots easily or deficiencies of various blood components
- hormone replacement therapy (HRT). The AHA currently states that the risk of stroke associated with HRT appears low but needs further study.
- use of birth control pills, or oral contraceptives
- inflammatory processes, such as a chronic infection with chlamydia
Several recent studies have identified factors that seem to increase or decrease the risk of stroke in particular groups of people. These findings warrant further investigation:
- People who were treated for high blood pressure with thiazide diuretics, such as hydrochlorothiazide, had a significantly lower stroke risk than people on ACE inhibitors or calcium channel blockers.
- Women ages 39 to 50 who ate more fish and omega-3 polyunsaturated fatty acids had a reduced risk of stroke. This was particularly true in women who did not take aspirin regularly.
- Women ages 15 to 44 who had 2 drinks of wine a day had a 40% to 60% lower risk of stroke than women who did not drink alcohol.
- Phenylpropanolamine, a compound contained in appetite suppressants and cold remedies, significantly increased the risk of hemorrhagic stroke in women 18 to 49 years of age. The Food and Drug Administration (FDA) has since asked manufacturers to remove phenylpropanolamine from their products.
- In one study, people who were treated in emergency departments for transient ischemic attacks (TIA) had a 25% chance of having a stroke or other serious health event within the next 90 days.
What can be done to prevent the condition?
A person may be able to reduce his or her risk for developing atherosclerosis of the carotid arteries, leading to stenosis, by:
- maintaining a healthy body weight
- getting 30 or more minutes of moderate exercise a day for most individuals. People with heart disease or disabilities should be in a medically supervised exercise program.
- eating a healthy diet for preventing heart disease, containing at least 5 fruits and vegetables a day
- controlling diabetes
- preventing or controlling high blood pressure
- preventing or controlling high cholesterol
People can also lower their risk of stroke from carotid stenosis by addressing other risk factors for stroke. The American Heart Association guidelines for stroke prevention address both modifiable and less well-documented or potentially modifiable risk factors.
Measures to reduce the modifiable risk of high blood pressure
- measurement of blood pressure in adults at least every 2 years to screen for high blood pressure
- weight control
- physical activity
- moderation in alcohol intake
- moderate sodium intake
- for those who smoke, quitting smoking
- medications to treat high blood pressure if the person's blood pressure is over 140/90 after 3 months of these lifestyle modifications, or if the initial blood pressure is over 180/100
Other measures to reduce an individual's modifiable risk factors for stroke may include:
- smoking cessation using nicotine patches, counseling, and formal smoking programs
- control of blood sugar levels in a person with diabetes through medication, diet, and exercise
- the use of ramipril (i.e., Altace) in people with diabetes. A recent study showed that people with diabetes have a 33% lower risk of ischemic stroke if they take ramipril.
- careful evaluation of asymptomatic carotid stenosis to determine the need for surgery. Coronary artery surgery, such as an endarterectomy, may be indicated. An endarterectomy opens the narrow portion of the artery and increases the blood flow to the brain. People with carotid stenosis should also work closely with their healthcare providers to control other risk factors for stroke.
- semiannual screening of children with sickle cell anemia, using ultrasound to determine the child's risk of stroke
- treatment of atrial fibrillation with blood thinners such as aspirin or warfarin, depending on the person's age and other risk factors
- monitoring of high levels of total cholesterol or LDL, as well as low levels of HDL. Depending on the blood levels and the person's other risk factors, medications to lower cholesterol may be given.
Measures to reduce less well-documented or potentially modifiable risks for stroke may include:
- weight reduction in overweight persons
- 30 or more minutes of moderate exercise a day for most individuals. People with heart disease or disabilities should be in a medically supervised exercise program.
- a healthy diet for preventing heart disease, containing at least 5 fruits and vegetables a day
- for those who drink alcohol, drinking in moderation. The AHA defines moderate drinking as no more than 2 drinks a day for men and 1 drink a day for women.
- seeking treatment for drug abuse
- monitoring of blood levels of homocysteine. For most individuals, a well-balanced diet following the food guide pyramid will provide enough folic acid and B vitamins to maintain a healthy homocysteine level. For people with elevated homocysteine levels, supplements containing folic acid and B vitamins may be recommended.
- avoiding the use of oral contraceptives in women with other stroke risk factors
Some people have early warning signs that they are at risk for strokes. The most common warning sign is what is known as a transient ischemic attack, or TIA. These episodes of stroke-like symptoms often goes away after a few minutes (but always within 24 hours). They are thought to be caused by clots that lodge in a small artery for a few minutes and then pass through or dissolve.
People with TIAs are well advised to get treatment that will prevent a stroke in the future, such as taking aspirin, or having carotid artery surgery to correct a blockage if one is found.
How is the condition diagnosed?
Carotid stenosis is diagnosed using a carotid ultrasound, also known as a duplex Doppler scan. An ultrasound uses sound waves to determine whether an artery has a blockage or reduced blood flow. Another way to diagnose carotid stenosis is by magnetic resonance angiography, a special X-ray test in which pictures are taken of the arteries in the neck. Both these tests are painless and noninvasive.
and cranial CT scans
may be ordered to show the type, size, and location of the stroke.
Long Term Effects
What are the long-term effects of the condition?
Strokes can cause death or permanent disability. Though many people recover some function in the first several months after a stroke, others show no improvement. Some people have several small strokes over time and slowly get worse with each one.
What are the risks to others?
Strokes are not contagious and pose no risk to others.
What are the treatments for the condition?
In cases when a stroke is caught in the first few hours, a clot-busting medication may be used to reverse a stroke. This is why early recognition of a stroke can be important. If someone has the early warning signs of stroke, the emergency medical system should be contacted immediately.
From the onset of symptoms, you have only 180 minutes to administer "clot busting" medications that can dissolve any clot and potentially prevent the stroke. This 180 minutes (three hours) includes transport to the hospital, evaluation by a physician, lab tests and a CT scan of the brain). Time is critical!
These signs include a sudden onset of:
weakness or numbness of the face, arm, or leg, especially on one side of the body
trouble walking or loss of balance, known as ataxia
speech impairments, including trouble speaking or understanding speech
- visual impairments
Unfortunately, most people with strokes come to medical attention too late to use the clot-busting medication. They are treated right away with aspirin if they do not have bleeding into the brain. This only serves to help prevent further strokes.
Other medications that may be used for a stroke from carotid stenosis include medications to lower blood pressure and cholesterol. Carotid endarterectomy may be recommended to widen the part of the carotid artery that is narrowed. This surgical procedure removes the cholesterol plaques and may prevent future strokes.
The decision to perform surgery will depend on the person's neurological status, the type of plaque clogging the artery, and whether the plaque has a break in it, known as a rupture. Supportive therapy may also be needed with some strokes. This may include an artificial breathing machine, or ventilator, and an artificial feeding tube if the person cannot swallow.
Rehabilitation services can help to improve a person's function after a stroke. Physical therapy and other therapy, such as speech therapy or occupational therapy, may be used to maximize recovery.
What are the side effects of the treatments?
Side effects depend on the treatments used. For instance, aspirin may cause allergic reactions, stomach upset, or bleeding. Clot-busting medications can cause excessive bleeding. A ventilator may sometimes cause damage to the lungs or an infection. A carotid artery endarterectomy can be complicated by cause bleeding, infections, and allergic reactions to the anesthesia.
On rare occasions, carotid endarterectomy can precipitate a stroke or heart attack by dislodging a clot which then wedges in an artery downstream.
What happens after treatment for the condition?
After the person is stable, treatment of the risk factors for stroke, as well as the cause of the stroke, is important to prevent further strokes. For instance, stopping smoking
and controlling high blood pressure,
diabetes, and high cholesterol
are advised for most people.
Many people need assistance of one form or another after a stroke. This may range from using a walking cane to needing 24-hour-a-day skilled nursing care. Ongoing therapy to improve function is usually advised for at least 6 months if the person is able.
How is the condition monitored?
People having a stroke are often admitted to the hospital for close monitoring. Once the person is stable, he or she can often be sent home or to a skilled nursing facility or rehabilitation center for further therapy.
Monitoring following a stroke from carotid stenosis includes regular blood pressure measurements, blood tests to check cholesterol
levels, and tests to see how the stenosis is progressing. Any new or worsening symptoms should be reported to the healthcare provider.