Fat deposits containing cholesterol build up, producing a plaque, which is yellow and often ugly in appearance. It roughens the usually very smooth inner surface of the blood vessel. A stroke is the end result of this process. Another variant of the atherosclerotic ischemic stroke is called thromboembolism. Occasionally a clot can form elsewhere, usually the heart, travel to an artery leading to the brain, and then block the brain's critical flow of blood.
Thrombotic strokes are the most common cause of ischemic strokes.
When a blood vessel ruptures and leaks, blood spills into the surrounding brain tissue, causing oxygen deprivation to the critical nerve cells. This is usually secondary to a ruptured blood vessel blister, called an aneurysm. Each year more than 30,000 Americans have a subarachnoid hemorrhage and 30 percent die before reaching a medical facility. Another hemorrhagic form, the intracerebral hemorrhage, is seen in people with hypertension and other systemic disorders, or congenital malformations of blood vessels. These initially bleed, damaging brain tissue and cause secondary ischemia due to the irregular blood supply.