Beyond COSS: The Evolution of Hemodynamic Imaging and Revascularization Strategies in Chronic Cerebrovascular Occlusion.

Chronic carotid occlusion (CCO) carries a significant risk of ischemic stroke, particularly in patients with impaired cerebrovascular reserve. Extracranial-intracranial (EC-IC) bypass emerged as a popular treatment strategy with high technical success rates. However, multiple large randomized trials, including the Carotid Occlusion Surgery Study (COSS), failed to demonstrate a statistically significant benefit, mainly due to perioperative stroke risk and limitations in patient selection. Surgical revascularization declined as a result. We aim through this review to re-examine the role of flow augmentation in CCO in light of modern advances in cerebral perfusion imaging. Contemporary modalities-including computed tomography perfusion and emerging magnetic resonance techniques-allow better identification of patients with hemodynamic compromise who may be at highest risk despite medical therapy. Future studies incorporating refined imaging criteria may better define the subset of patients most likely to benefit from selective revascularization.