It s hard to say, I don t think that their anatomical name is frontal artery, must have been the doctors simplifying things for you to understand. My guess would be both carotid arteries are occluded and blood supply is maintained by the posterior vessels (there are communications between the anterior and posterior systems). If it was the case of an isolated occlusion of the carotids and these posterior arteries have a good caliber, without narrowings then it could be the case that blood supply is enough and not be a big issue. The problem is that usually it s not an isolated issue, while the carotid arteries were the first and most affected, this is a disease of all blood vessels and it can affect arteries everywhere in the body not just the brain, it can cause heart infarct (that chest pain is a worrying sign) or infarct in any other territory, not only the brain. So he is a very high risk patient for this kind of complication and his life expectancy is limited though I can t give exact figures. As about what you can do, well I suppose your doctors have already told you, treat diabetes, treat high blood pressure, statins (cholesterol lowering drugs), no smoking and healthy lifestyle etc as well blood thinning products (aspirin, clopidogrel).