About Stroke
Types of Stroke
Ischemic Stroke
An ischemic stroke occurs when an artery that supplies blood and oxygen to
the brain becomes blocked. Most strokes are of this type. Blood clots are
the most common cause of artery blockage. Ischemic strokes can also be
caused by a narrowing of the arteries (called stenosis). The most common
condition that causes stenosis is atherosclerosis. In atherosclerosis,
plaque (a mixture of fatty substances including cholesterol and other
lipids) and blood clots build up inside the artery walls, causing
thickening, hardening, and loss of elasticity. These lead to decreased blood
flow.
Hemorrhagic Stroke
A hemorrhagic stroke occurs when an artery in the brain bursts. Hemorrhage
can occur in several ways. One cause is an aneurysm, a weak or thin spot on
an artery wall that can expand like a balloon. The thin walls of the
stretched artery can rupture or break. Hemorrhage also occurs when arterial
walls lose their elasticity and become brittle and thin. They can then crack
and bleed. This can happen with atherosclerosis. High blood pressure
increases the risk of a hemorrhagic stroke.
There are two main types of hemorrhagic stroke. An intracerebral
hemorrhage occurs when a blood vessel in the brain leaks blood into the
brain itself. A subarachnoid hemorrhage is bleeding under the outer
membranes of the brain and into the thin fluid–filled space that surrounds
the brain.
Transient Ischemic Attacks
A transient ischemic attack (TIA) is sometimes called a mini–stroke. It
starts just like a stroke but then clears up within 24 hours, leaving no apparent symptoms
or deficits. A TIA is a warning that the person is at risk for a more
serious stroke. Having other risk factors increases a person's chances of a recurrent stroke
if they have had a TIA. For most TIAs the symptoms go away within an hour.
However, there is no way to tell whether symptoms will be a TIA or a more
serious stroke that can lead to death or disability. The sudden onset of the
symptoms of a stroke should signal an emergency. Patients and witnesses
should not wait to see if the symptoms go away.
Page last reviewed: October 10, 2007
Page last modified: February 9, 2007
Content source: Division for Heart Disease and Stroke Prevention,
National Center for Chronic Disease Prevention and
Health Promotion
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