A healthy carotid artery is smooth on the inside, like a tube. But health problems, such as high blood pressure, diabetes, and smoking, vaping, or using other tobacco or nicotine products, can damage the inside of the artery wall and make it rough. This lets fatty deposits, called plaque, build up on the artery wall. Blood clots called emboli may also form on the plaque. If pieces of plaque or emboli break off, they can flow in the blood and get stuck in a small blood vessel in the brain. This blocks the blood flow to a part of the brain, and causes a stroke.