Supplementary Material for: Carotid Artery Stenosis as a Cause of Stroke

Background: Population-based studies have estimated that about 15% of ischemic strokes are caused by large-vessel cerebrovascular disease. We determined the types of large-vessel atherosclerosis responsible for ischemic strokes in a population-based stroke study. Methods: Patients with first-ever or recurrent ischemic stroke in the Greater Cincinnati area were identified during 2005 at all local hospitals. Study physicians assigned ischemic stroke subtypes. Overall event rates and incidence rates for first-ever events were calculated, and age-, race- and sex-adjusted to the 2000 US population. Results: There were 2,204 ischemic strokes, including 365 strokes of large-vessel subtype (16.6% of all ischemic strokes). Extracranial internal carotid artery (ICA) stenosis was associated with 8.0% of all ischemic strokes, while extracranial ICA occlusion and intracranial atherosclerosis were each associated with 3.5% of strokes. The annual rate of first-ever and recurrent stroke attributed to extracranial ICA was 13.4 (11.4–15.4) per 100,000 persons. We conservatively estimate that about 41,000 strokes may be attributed to extracranial ICA stenosis annually in the United States. Conclusions: Large-vessel atherosclerosis is an important cause of stroke, with extracranial ICA stenosis being significantly more common than extracranial ICA occlusion or intracranial atherosclerotic disease.