Epidemiology of Intracranial and Extracranial Large Artery Stenosis in a Population-Based Study of Stroke in the Middle East

Background: Intracranial large-artery disease (LAD) is a predominant vascular lesion found in patients with stroke of Asian, African, and Hispanic origin, whereas extracranial LAD is more prevalent among Caucasians. These patterns are not well-established in the Middle East. We aimed to characterize the incidence, risk factors, and long-term outcome of LAD strokes in a Middle-Eastern population. Methods: The Mashhad Stroke Incidence Study is a community-based study that prospectively ascertained all cases of stroke among the 450,229 inhabitants of Mashhad, Iran between 2006 and 2007. Ischemic strokes were classified according to the TOAST criteria. Duplex-ultrasonography (98.6%), MR-angiography (8.3%), CT-angiography (11%), and digital-subtraction angiography (9.7%) were performed to identify involvements. Vessels were considered stenotic when the lumen was occluded by >50%. Results: We identified 72 cases (15.99 per 100,000) of incident LAD strokes (mean age 67.6 ± 11.7). Overall, 77% had extracranial LAD (58% male, mean age 69.8 ± 10.3; 50 [89%] carotid vs. 6 [11%] vertebral artery), and the remaining 23% (56% male, mean age 60.2 ± 13.4; 69% anterior-circulation stenosis) had intracranial LAD strokes. We were unable to detect differences in case-fatality between extracranial (1-year: 28.6%; 5-year: 59.8%) and intracranial diseases (1-year: 18.8%; 5-year: 36.8%; log-rank; p = 0.1). Conclusion: Extracranial carotid stenosis represents the majority of LAD strokes in this population. Thus, public health strategies may best be developed in such a way that they are targeted toward the risk factors that contribute to extracranial stenosis.