A stroke, also often called a "brain attack," occurs when blood flow to the brain is cut off by a blood clot or a ruptured blood vessel. Starving brain cells begin to die within minutes, so seeking immediate treatment is critical.
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, which typically accounts for more than 80 percent of all strokes, occurs 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:
Transient ischemic attacks, also called TIAs, are minor or warning strokes. In a TIA, conditions indicative of an ischemic stroke are present and the typical stroke warning signs develop. However, the obstruction (blood clot) occurs for a short time and tends to resolve itself through normal mechanisms. Even though the symptoms disappear after a short time, TIAs are strong indicators of a possible major stroke. Steps should be taken immediately to prevent a stroke.
Hemorrhagic stroke accounts for fewer than 20 percent of stroke cases and 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.
Two types of weakened blood vessels usually cause hemorrhagic stroke: aneurysms and arteriovenous malformations (AVMs).