Stroke

Ischemic stroke occurs when the blood supply to the brain is blocked. The most common cause of blockage is blood clots. Blood clots can form almost anywhere in the body, dislodge, and travel through the arteries eventually lodging and diminishing or cutting off blood flow. They originate most commonly in the heart. Blood clots form in the heart for many reasons, including birth defects, malfunctioning or damaged heart valves, and an irregular heartbeat (atrial fibrillation).

Damaged arteries represent another leading cause of ischemic stroke. There are three main causes of damage to the arteries. Atherosclerosis can occur in any artery in the body but causes stroke most often when it is found in the neck arteries. As people age, small streaks of fat settle in the walls of the arteries. These streaks can grow into plaque that can trap cells in the blood platelets that start clotting. The fatty deposits build up and can eventually fester and crack, forming clots that either close off a neck artery or wash up into the brain, resulting in a stroke.

Accidental damage to the neck arteries can also cause stroke. An artery has three layers, and any sudden twist of the neck or direct trauma to the neck can cause the arterial layers to shear apart (dissection) and either close the vessel or create clots that will cause blockage that results in stroke.

In people who suffer from high blood pressure, their brain blood vessels can become thick, stiff, and brittle. Because there is less room for blood to flow and the vessels are not flexible enough to accommodate increased blood pressure, they can either close off completely or rupture. Diabetes can also weaken the small blood vessels of the brain.

Blood abnormalities can be a potential source of stroke. Abnormalities in the blood can cause clotting, bleeding, or both.

Blood supply is essential to the health and operation of the brain. The areas of the brain that do not receive enough blood or no blood at all will die, resulting in dead tissue (infarct) and loss of brain function.