Stroke. Coloured computed tomography (CT) scan of an axial section through a patient's brain showing internal bleeding (orange) due to a cerebrovascular accident (CVA), or stroke. The front of the brain is at top. A stroke is brain damage caused by an interruption to the brain's blood supply or by the leakage of blood through blood vessel walls. The two main causes are high blood pressure and atherosclerosis (narrowing of the arteries due to fat deposition). Strokes vary in severity depending on the site and extent of damage, but can result in long-term paralysis, coma and even death. CT scans use X-rays to construct images of slices through the body.