An ischemic stroke occurs when an artery supplying the brain with blood becomes blocked, suddenly decreasing or stopping blood flow and ultimately causing a brain infarction. This type of stroke accounts for approximately 80 percent of all strokes.
If caring for a senior or advancing in age yourself it is important to note that problems with clotting become more frequent as people age.
Blood clots are the most common cause of artery blockage and brain infarction. The process of clotting is necessary and beneficial throughout the body because it stops bleeding and allows repair of damaged areas of arteries or veins. However, when blood clots develop in the wrong place within an artery they can cause devastating injury by interfering with the normal flow of blood. When blood flow to the brain is blocked, brain cells begin to die within minutes.
Mini- strokes, known as transient ischemic attacks (TIA), occur when normal flow of blood to the brain is blocked, but only temporarily. When compared with a full-blown stroke, a TIA may happen quickly, seem minor and may receive little attention. However, any interruption of blood flow to the brain should be considered a serious event. TIAs are often an indicator of impending major stroke.
Blood clots can cause ischemia and infarction in two ways. A clot that forms in a part of the body other than the brain can travel through blood vessels and become wedged in a brain artery. This free-roaming clot is called an embolus and often forms in the heart. A stroke caused by an embolus is called an embolic stroke.
The second kind of ischemic stroke, called a thrombotic stroke, is caused by thrombosis, the formation of a blood clot in one of the cerebral arteries that stays attached to the artery wall until it grows large enough to block blood flow.
Ischemic strokes can also be caused by stenosis, or a narrowing of the artery due to the buildup of plaque (a mixture of fatty substances, including cholesterol and other lipids) and blood clots along the artery wall. Stenosis can occur in large arteries and small arteries and is therefore called large vessel disease or small vessel disease, respectively. When a stroke occurs due to small vessel disease, a very small infarction results, sometimes called a lacunar infarction, from the French word "lacune" meaning "gap" or "cavity."
The most common blood vessel disease that causes stenosis is atherosclerosis. In atherosclerosis, deposits of plaque build up along the inner walls of large and medium-sized arteries, causing thickening, hardening, and loss of elasticity of artery walls and decreased blood flow.
A person experiencing stroke symptoms like slurred speech, blurry vision, disorientation, and numbness or weakness in the face or extremities should seek medical treatment as soon as possible.
Source: National Institute of Neurologic Disorders and Stroke (NINDS), https://www.ninds.nih.gov/Disorders/All-Disorders/Transient-Ischemic-Attack-Information-Page