Extracranial-Intracranial Bypass Surgery for Stroke Prevention in Hemodynamic Cerebral Ischemia

ATHEROSCLEROTIC INTERNAL carotid artery occlusion (AICAO) causes approximately 10% of transient ischemic attacks (TIAs) and 15% to 25% of ischemic strokes in the carotid territory. The 2-year risk of subsequent ipsilateral ischemic stroke while a patient receives medical therapy is 10% to 15%. Extracranial-intracranial (EC-IC) arterial bypass surgery was developed to prevent subsequent stroke by improving hemodynamics distal to the occluded artery. In 1985, a randomized trial demonstrated no benefit of this surgery in 808 patients with symptomatic carotid artery occlusion. This trial was criticized for failing to identify the subgroup of patients with hemodynamic cerebral ischemia due to poor collateral circulation for whom surgical revascularization might be of greatest benefit. Subsequent advances in neuroimaging have made it possible to identify those with hemodynamic cerebral ischemia who are at high risk for subsequent stroke when treated medically. We conducted the Carotid Occlusion Surgery Study (COSS) to determine whether EC-IC bypass surgery, added to best medical therapy, reduces subsequent ipsilateral ischemic stroke at 2 years in patients with recently symptomatic AICAO and hemoFor editorial comment see p 2026. Author Affiliations and a list of the Carotid Occlusion Surgery Study (COSS) investigators appear at the end of this article. CorrespondingAuthor:WilliamJ.Powers,MD,Department of Neurology, Box 7025, Room 2131, 170 ManningDr,UniversityofNorthCarolinaatChapelHill,Chapel Hill, NC 27599 ([email protected]). Context Patients with symptomatic atherosclerotic internal carotid artery occlusion (AICAO) and hemodynamic cerebral ischemia are at high risk for subsequent stroke when treated medically.