Types of Stroke
A stroke is a brain attack that occurs when blood flow to the brain is disrupted. Most strokes fall into two categories:
- Ischemic strokes (caused by blockage of an artery)
- Hemorrhagic strokes (caused by bleeding into the brain)
Ischemic strokes occur when there is an obstruction within a blood vessel that supplies blood to the brain. About 87 percent of all strokes are ischemic strokes. Atherosclerosis (fatty deposits lining the vessel walls) is the underlying condition that causes this type of obstruction.
These fatty deposits can cause two types of obstruction:
- Cerebral thrombosis - a blood clot (thrombus) that develops at the clogged part of a vessel
- Cerebral embolism – a blood clot forms at another location in the circulatory system, a portion of the blood clot breaks loose and enters the bloodstream and then travels through the brain's blood vessels until it reaches vessels too small to let it pass
Weakened blood vessels that rupture and bleed into the surrounding brain can cause hemorrhagic strokes. The blood accumulates and compresses the brain tissue.
The types of hemorrhagic strokes are:
- Intracerebral hemorrhage - occurs when a diseased blood vessel within the brain bursts, allowing blood to leak inside the brain
- Subarachnoid hemorrhage – occurs when there is bleeding in the area between the brain and the thin tissues that cover the brain
Weakened blood vessels can also result in:
- Aneurysm - a ballooning of a weakened region of a blood vessel; left untreated, the aneurysm continues to weaken until it ruptures and bleeds into the brain
- Arteriovenous malformation (AVM) - a cluster of abnormally formed blood vessels; any one of these vessels can rupture, also causing bleeding into the brain