Stroke
Alternate Names : Brain Attack, Cerebrovascular Accident, CVA
A stroke is the death of brain tissue that occurs when the brain does not get
enough blood and oxygen.
What is going on in the body?
Strokes are classified as ischemic strokes or hemorrhagic strokes.
Ischemic strokes happen when the blood supply to the brain is
interrupted. The brain cells then die from lack of oxygen.
Hemorrhagic strokes occur when blood vessels in the brain burst and
release blood into the area around the brain cells. 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.
Examples of ischemic strokes are:
stroke from atherosclerosis,
which
occurs when the arteries supplying the brain are narrowed by plaque formation
on the vessel walls
stroke from carotid stenosis,
which is a blockage in one of the carotid arteries in the neck
arteritis, or artery inflammation, in an artery that supplies the brain.
This may be due to a condition called temporal arteritis, for example.
stroke from carotid dissection. A carotid dissection occurs when
one of the carotid arteries in the neck is torn by an injury and blood flow to
the brain is blocked.
polycythemia vera, a blood
cancer
that causes blood cells to multiply and the blood to thicken. The thickened
blood prevents normal oxygenation of brain cells.
stroke from cardiogenic
embolism,
a condition in which blood clots travel from the heart. Blood clots from the
heart may be caused by an irregular heartbeat called atrial
fibrillation, severe congestive heart failure,
and heart attack.
stroke caused by cholesterol or plaque from an artery in the neck. When the
cholesterol or plaque travels and blocks an artery supplying the brain, a
stroke occurs.
severe migraine headaches, which cause constriction of the
blood vessels within the brain and deprive brain cells of oxygen
Hemorrhagic strokes occur when there is bleeding into the brain
caused by damage to the blood vessels. A hemorrhagic stroke may be caused by:
high blood pressure
abnormal bleeding from blood-thinning medications, such as warfarin or
heparin
hemophilia A or hemophilia B, which are blood disorders
that
prevent normal blood clotting
low numbers of platelets, a type of blood cell involved in blood
clotting. Low platelet counts are seen in a number of diseases and conditions,
including acute infections and a severe allergic reaction known as anaphylactic shock.
rupture of a cerebral aneurysm, or
weakened blood vessel wall within the brain
sickle cell disease, an inherited condition that results in
abnormal red blood cells
a group of abnormal blood vessels within the brain known as an
arteriovenous malformation, or AVM
head injuries
eclampsia, a complication of
pregnancy that causes high blood pressure in the mother
Stroke is the third leading cause of death in the US and many other
countries, right after heart
disease
and cancer.
What are the causes and risks of the condition?
Strokes are caused by an interruption of the blood flow to brain cells or by
damage to brain cells.
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 ischemic 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.
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