Stroke from Carotid Stenosis
Alternate Names : Brain Attack
A stroke is the death of brain tissue that occurs when the brain does not get
enough blood and 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 happens 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 blood then damages the brain cells. The products released when
cells die cause swelling in the brain. Since the skull doesn't allow much 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 do.
family history of stroke or
transient
ischemic attack (TIA). A TIA is a short, reversible form of stroke
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
smoking
diabetes
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 or "bad
cholesterol." Low levels
of HDL or "good
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 less proof of either a link to stroke or the impact of
modifying the risk factor. These factors include:
obesity
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 studies,
which warrant further investigation, include these findings:
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.
|
