Stroke caused by a thrombosis. Axial magnetic resonance imaging (MRI) scan (left) showing damage (bright area) in the left hemisphere of a 28-year-old woman's brain, caused by a thrombotic stroke (cerebrovascular accident, CVA). The stroke was caused by an abnormal blood clot (thrombosis). At right, the magnetic resonance angiography (MRA) scan shows where a branch of the middle cerebral artery has been blocked by the clot. A stroke is where the brain is damaged due to hypoxia (lack of oxygen). This image was obtained less than four hours after the stroke. For this patient 24 hours later, with improved blood supply, see image C047/4851.