Purpose

This is a prospective, randomized, single blind, concurrent controlled, multi-center study. Patients presenting with symptoms of acute ischemic stroke who have evidence of a large vessel (2.5mm or greater in diameter) occlusion in the cerebral circulation will be assigned to either the Penumbra System with the Separator 3D or the Penumbra System without the Separator 3D. Each treated patient will be followed and assessed for 3 months after randomization. Up to 230 evaluable patients at up to 50 centers presenting with acute ischemic stroke in vessels accessible to the Penumbra Separator 3D System for revascularization within 8 hours of symptom onset. The hypothesis to be tested is that the safety and effectiveness of the Penumbra System with the Separator 3D for the revascularization of large vessel occlusion is not inferior to the Penumbra System alone.