Stroke occurs when a blood vessel is blocked by a clot (an "ischemic" stroke) or when a blood vessel in the brain ruptures ("hemorrhagic" stroke). Larger strokes can cause swelling and compression in the brain. In both types of stroke, the flow of oxygen-rich blood is cut off to a part of the brain, and brain cells die. As a result, a person suffers neurological deficits related to the part of the brain that is damaged.
Ischemic strokes are often the result of carotid artery disease, a buildup of plaque inside the walls of the arteries in the neck, which can restrict or block the flow of blood to the brain. Most hemorrhagic strokes occur as a consequence of high blood pressure, which can lead to rupture of tiny arteries deep within the brain.
An early warning sign of an impending ischemic stroke is one or more transient ischemic attacks (TIAs) or "mini-strokes." TIAs are critical warning signs that a stroke may be on the way in the coming days or months. During a TIA, blood flow to part of the brain is temporarily restricted, leading to temporary neurological deficits. The symptoms may be the same as those of a stroke, but milder, and may last only a few minutes.