stroke An interruption of BLOODflow and oxy-
gen supply to the BRAIN, sometimes called a brain
attack. Stroke strikes about 700,000 Americans
each year. For two thirds of them the stroke is a
second or subsequent stroke. About 85 percent of
strokes are ischemic; they result from blockage of
an arterial pathway in the brain. The remaining
15 percent are hemorrhagic; they result from
bleeding into the brain, typically from a blood ves-
sel that ruptures. About 90 percent of people sur-
vive a first ischemic stroke, though a third of them
experience permanent disability of varying sever-
ity as a consequence of the damage to the brain.
The risk for death rises with each subsequent
stroke. Hemorrhagic strokes are more likely to be
fatal, claiming the lives of nearly half of those who
have them. In 2000, about 2.4 million Americans
were stroke survivors.
HYPERTENSION(high BLOOD PRESSURE) is the lead-
ing cause of stroke. Unfortunately, hypertension
has no symptoms and many people do not know
they have it until they suffer stroke or HEART
ATTACK. Chronically elevated blood pressure
stresses blood vessels, causing them to stiffen and
thicken to help protect against the constant
pounding of blood. This response (ARTERIOSCLE-
ROSIS) makes the arteries vulnerable to INFLAMMA-
TIONand accumulations of debris (ATHEROSCLEROTIC
PLAQUE), resulting in ATHEROSCLEROSIS. The high
pressure of blood rushing through the arteries
causes tiny fragments of the plaque to break free.
The fragments float through the blood circulation
until they lodge in a blood vessel, blocking the
further flow of blood. When this occlusion hap-
pens in the heart, it causes a MYOCARDIAL INFARC-
TIONor heart attack. In the brain, the occlusion
causes stroke.
Health experts recommend annual
BLOOD PRESSUREchecks for all people age
50 and older, and for younger people
who have risk factors for CARDIOVASCU-
LAR DISEASE(CVD).Brain cells require a constant supply of oxygen
to meet their energy needs. Deprivation of oxygen
for as little as 30 seconds causes them to begin
shutting down. Lack of oxygen for two to three
minutes causes brain cells to begin dying. After
five minutes, enough brain cells can die to cause
permanent loss of function in the affected area.
This loss may involve cognitive function, memory,
speech and language processing, and physical
movement. The brain’s correlation to the body is
ipsilateral. Damage to the right brain may result in
weakness or paralysis on the left side of the body;
damage to the left brain may affect the right side
of the body.Time is crucial. Treatment for ischemic
stroke that begins within four hours
can incorporate drugs to dissolve the
blocking blood clot, minimizing or pre-
venting damage to the brain.Symptoms and Diagnostic Path
Symptoms of stroke may be subtle or pronounced.
The main symptoms of stroke include- numbness or tingling on one side of the face or
body - difficulty speaking (including slurred speech) or
swallowing - drooping of facial features on one side
- weakness or PARALYSISon one side of the body
- loss of vision or change in vision, particularly in
only one EYE
It is important to seek medical attention with-
out delay at the first indication that a stroke may
be occurring. Early treatment with THROMBOLYTIC
THERAPYcan dissolve developing blood clots, miti-
gating or preventing the stroke. The diagnostic
path typically includes COMPUTED TOMOGRAPHY(CT)
SCANor MAGNETIC RESONANCE IMAGING(MRI) to visu-
alize the location and extent of the stroke, and to
determine whether the stroke is ischemic or hem-
orrhagic. ELECTROENCEPHALOGRAM (EEG), which
measures the brain’s electrical activity, and a com-
prehensive NEUROLOGIC EXAMINATIONcan help assess
the extent of damage the stroke has caused.Treatment Options and Outlook
Immediate treatment focuses on minimizing dam-
age to the brain. Optimally, early intervention per-
mits thrombolytic therapy, which must begin
within four hours of the stroke’s onset. Treatmentstroke 107