Recovery from a stroke. Coloured axial magnetic resonance imaging (MRI) scan (left) showing improved blood supply (bright areas) in the left hemisphere of a 28-year-old woman's brain 24 hours after 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 branches of the middle cerebral artery that were blocked by the clot. A stroke is where the brain is damaged due to hypoxia (lack of oxygen). For this patient's brain less than four hours after the stroke, see image C047/4850.