Blood flows to the brain through tubes called arteries.
These can harden in older patients with high blood pressure or high cholesterol. Hardened arteries will close down and develop blood clots that fly into the blood stream where they clog small blood vessels deep in the brain. Surgery may help some patients, but most will continue to have parts of the brain die when there is no blood supply to feed the nerve cells. A stroke is caused by part of the brain dying from a clogged blood vessel. Most dementia is caused by Alzheimer's disease, not strokes.