The carotid arteries are the main blood vessels supplying the brain. An atheroma or atherosclerotic plaque (‘ furring up’ ) is an accumulation of fatty material on the inner layer of the wall of the artery. The build up of these plaques makes the artery narrower (known as “stenosis”) and this process can alter blood flow making clots more likely to form.
The result of all of this is to restrict and occasionally prevent the supply of blood to part of the brain thus leading to a stroke. Alternatively, if an atheroma ruptures, it exposes the lining of the artery and a blood clot (thrombosis) forms over the damaged area. Fragments of these clots can then break off and go up to the brain, block a blood vessel and also cause a stroke.