What causes large-artery atherothrombotic stroke?

Large-artery atherothrombotic stroke occurs when atherosclerotic plaque builds up and narrows an artery in any of four strategic locations -- the origin of the internal carotid artery, the siphon portion of the internal carotid artery, the middle cerebral artery stem, or the junction of the distal vertebral arteries and the basilar artery. If the plaque ruptures, a clot may grow to obstruct an artery in the brain or break off and travel to another artery, causing an artery-to-artery stroke. Damage from artery-to-artery strokes can grow worse when atherosclerosis triggers a second stroke; when brain swelling increases pressure inside the skull; or when bleeding occurs, causing a hemorrhagic stroke known as a conversion. This type of stroke accounts for about 15% of all ischemic strokes.