Stroke occurs when a clogged or burst artery interrupts blood flow to the brain. This interruption of blood flow deprives the brain of needed oxygen and causes the affected brain cells to die. When brain cells die, function of the body parts they control is impaired or lost.
Stroke can be caused either by a clot obstructing the flow of blood to the brain (ischemic stroke) or by a blood vessel rupturing and preventing blood flow to the brain (hemorrhagic stroke).
Ischemic stroke accounts for about 87 percent of all cases. Ischemic strokes occur as a result of an obstruction within a blood vessel supplying blood to the brain. The underlying condition for this type of obstruction is the development of fatty deposits lining the vessel walls. This condition is called atherosclerosis.
These fatty deposits can cause two types of obstruction:
Hemorrhagic stroke accounts for about 13 percent of stroke cases. It results from a weakened vessel that ruptures and bleeds into the surrounding brain. The blood accumulates and compresses the surrounding brain tissue. The two types of hemorrhagic strokes are intracerebral hemorrhage or subarachnoid hemorrhage.
The two types of weakened blood vessels that may cause hemorrhagic stroke are aneurysms and arteriovenous malformations (AVMs).