Stroke caused by blocked blood flow
About 85% of all strokes happen because not enough blood gets to the brain. Blood flow stops when an artery carrying blood to the brain becomes blocked. The technical name for this type of brain attack is cerebral infarction. It is also called an ischemic stroke. “Ischemic” refers to a condition caused by a decreased supply of oxygenated blood to a body part.
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 atherosclerosis (blockage), also called “hardening of the arteries”, due to the build-up of cholesterol and other thick, rough, fatty deposits in the arteries.
The blockage can also be caused by a small piece of tissue, usually a blood clot, that has travelled through the bloodstream from elsewhere in the body.
In ischemic stroke, one of two major arteries is usually involved:
• The carotid artery (most commonly involved site)
• The basilar artery
The carotid artery starts 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.
Stroke caused by Bleeding in the brain
The other 15% of strokes happen when an artery carrying blood to the brain burst suddenly. The bursting can happen because of a weak spot in the wall of an artery called an aneurysm. This type of brain attack is called hemorrhage stroke.
Two kinds of stroke are caused by bleeding in the brain:
• A subarachnoid hemorrhage occurs 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
• An intracerebral hemorrhage occurs 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.
What are “Mini-Stroke”?
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 the cells. But the difference between a TIA and a stroke is that, with TIA, the blood clot dissolves on its own and blood flow is restored before permanent damage to the brain can occur.
TIA is an extremely important warning sign for stroke and should never be ignored.