A stroke occurs when the blood flow to a part of the brain is disrupted. Not enough blood reaches the affected part of the brain. The cells in the part of the brain affected do not get enough oxygen and begin to die.
Damage to the brain can cause loss of speech, vision, or movement in an arm or a leg, depending on the part of the brain that is affected.
There are two main types of stroke:
- Stroke caused by a blockage in the artery supplying blood to a particular region of the brain (called cerebral infarction). This is the most common type of stroke.
- Stroke caused by bleeding within the brain (called intracerebral hemorrhage).
In addition, some people experience brief warning signals that a major stroke is going to happen in the future. The medical term to describe these symptoms is transient ischemic attack or TIA. Sometimes called "mini-strokes", TIAs are exactly like a stroke, but they last only a few minutes (or sometimes as long as an hour) and leave no disability.
In many cases, a stroke will affect only one side of the body:
- A stroke that damages the right side of the brain will affect the left side of the body.
- A stroke that damages the left side of the brain will affect the right side of the body.
About 85 percent of all strokes happen because not enough blood gets to the brain. Blood flow stops when an
The blockage can be caused either by a blood clot that forms in an artery in the brain, or by a blood clot formed elsewhere in the body that travels through the bloodstream to the brain. If this clot becomes stuck in an artery in the brain, a stroke can result.
Clots are more likely to form in arteries that are damaged by
The blockage also can be caused by a small piece of tissue, usually a blood clot, that has traveled through the bloodstream from elsewhere in the body.
In ischemic stroke, one of two major arteries is usually involved:
carotid artery(most commonly involved site)
- The basilar artery
The carotid arteries start at the aorta (just above the heart) and lead up through the neck, around the windpipe, and into the brain. The basilar artery is formed at the base of the skull from the arteries that run up along the spine, and branches off in the brain.
The other 15 percent of strokes happen when an artery carrying blood to the brain bursts suddenly. The bursting can happen because of a weak spot in the wall of an artery called an
Two kinds of stroke are caused by bleeding in the brain:
subarachnoid hemorrhageoccurs when a blood vessel on the brain bursts and bleeds into the fluid-filled space between the brain and the skull. This type of stroke can happen at any age.
intracerebral hemorrhageoccurs when an artery bursts inside the brain, flooding the surrounding brain tissue with blood. This type of stroke is often associated with high blood pressure.
A "mini-stroke" is exactly like a stroke, but it lasts only a short time and leaves no disability. The term for this event is transient ischemic attack or TIA.
A TIA happens when a blood clot clogs an artery temporarily, cutting off blood flow and, consequently, the supply of oxygen to cells. But the difference between a TIA and a
TIAs are an extremely important warning sign for stroke and should never be ignored.
Nice To Know:
About 10 percent to 15 percent of strokes are preceded by TIAs ('mini-strokes'), which can happen days, weeks, or even months before a major stroke. However, not everyone who experiences a TIA will have a stroke in the future.
Nice To Know:
General recovery guidelines for stroke show:
Facts About Stroke: