The man was 66 when he came to the hospital with a serious skin infection. He had a fever and low blood pressure, as well as a headache. His doctors gave him a brain scan just to be safe. They found a very small bulge in one of his cranial arteries, which probably had nothing to do with his headache or the infection. Nevertheless, doctors ordered an angiogram to get images of brain blood vessels. This test, in which doctors insert a plastic tube into a patient’s arteries and inject dye, found no evidence of any blood vessel problems. But the dye injection caused multiple strokes, leading to permanent issues with the man’s speech and memory.