The Facts
Stroke is a sudden loss of brain function caused by the interruption of
blood flow to the brain, as a result of either:
- an ischemic stroke (a blood clot), or
- a hemorrhagic stroke (the rupture of a blood vessel and bleeding into or
around the brain).
The interruption of blood flow to the brain causes brain cells (neurons) in
the affected area to die. The effects of a stroke depend upon which part of
the brain was injured and how much damage has occurred. About 80% of strokes
are ischemic and 20% are hemorrhagic.
Stroke is a leading cause of disability worldwide, and approximately 4 million Americans are living with the effects of stroke. It is also the third leading cause of death in the United States. About 60% of
people who have had a stroke are left with some form of disability such as paralysis,
sensory loss, memory loss, language problems, and vision problems. Some people
may also suffer from depression or other emotional conditions after a stroke.
Risk factor modification, medications and, in some cases, surgery can
help to minimize the risk of a having a stroke.
Causes
An ischemic stroke is the result of blockage in blood flow to the brain
caused by a blood clot. The buildup of plaque in the artery wall (atherosclerosis
or "hardening of the arteries") is an underlying cause for many ischemic
strokes. Atherosclerosis is a process in which fatty deposits (cholesterol)
build up inside the blood vessels of the body, particularly in the carotid arteries
of the neck, the coronary arteries of the heart, and the arteries of the legs.
Atherosclerotic plaques can lead to blockage of blood flow, or plaque material
(emboli) can dislodge and travel to the brain, where it causes a stroke.
A hemorrhagic stroke is caused by bleeding into the brain (intracerebral
hemorrhage) or bleeding around the brain (subarachnoid hemorrhage), which results
from the breakage of a blood vessel. Brain hemorrhages may result from uncontrolled
high blood pressure, and, in some cases, can be caused by structural problems
within the blood vessels (e.g., aneurysms or vascular malformations).
There are numerous risk factors that can cause a stroke.
Factors you can't control are:
- age - The risk of stroke increases with advancing age.
- ethnicity - People of North American aboriginal, African, Hispanic,
South Asian, and Black descent have greater rates of high blood pressure and
diabetes. These conditions increase the risk of stroke.
- family history - The risk of stroke may be higher if a parent or
sibling has had a stroke before the age of 65.
- prior stroke or transient ischemic attack (TIA) - Up to a third of
people who survive a first stroke or TIA will have another stroke within 5
years.
Factors you can control are:
- high blood pressure
- heart disease/atrial fibrillation (irregular heartbeat)
- cigarette smoking
- diabetes
- high cholesterol
- physical inactivity
- high alcohol intake (more than two drinks per day)
Other factors that can lead to a stroke are:
- other medical conditions such as amyloid angiopathy and antiphospholipid
antibody syndrome
- use of illicit drugs such as cocaine or LSD
- some medications, such as tamoxifen, phenylpropanolamine, and thrombolytics*
Oral contraceptive use, hormone replacement therapy, and pregnancy and childbirth
in women with pre-existing medical conditions may increase the risk of stroke
in specific cases, but there is no conclusive evidence to date. Talk to your
doctor about risk factors that may be relevant to you and your risk of stroke.
