• Revascularization of the occluded target vessel (revascularization is defined by a Thrombolysis in Myocardial Infarction [TIMI] score of II or III following use of the Penumbra System)
  
• Incidence of device-related and procedure-related serious adverse events
  

• The proportion of patients who have either a 4-point improvement on the National Institutes of Health Stroke Scale (NIHSS) at discharge or a modified Rankin Scale (mRS) score of ≤ 2 at 30 days after treatment
  
• The proportion of patients with a modified Rankin Scale (mRS) score of ≤ 2 at 90 days post treatment
  
• All cause mortality
  
• Incidence of symptomatic hemorrhage
  

Purpose:

The purpose of this clinical evaluation is to assess the safety and effectiveness of the Penumbra System in the revascularization of patients presenting with acute ischemic stroke secondary to intracranial, large vessel, occlusive disease. Up to 125 evaluable patients will be enrolled in the study.

Inclusion Criteria:

• Clinical signs consistent with acute ischemic stroke
• 18 to 79 years of age
• Neurological deficit resulting in an NIH Stroke Scale (NIHSS) score > 8
• TIMI 0 or TIMI I flow in vessels accessible to the Penumbra System
• Signed informed consent
• Present within 8 hours of stroke symptom onset; ineligible or refractory to intravenous tissue plasminogen activator (t-PA) therapy if presenting within 3 hours of symptom onset.

Exclusion Criteria:

• Evidence of rapidly improving neurological signs of stroke at time of enrollment
• NIHSS > 30 or coma
• Females who are pregnant
• Vessel tortuosity too difficult to allow endovascular access
• Known hemorrhagic diathesis, coagulation deficiency, or on oral anticoagulant therapy with an International Normalized Ratio (INR) > 3.0
• Partial thromboplastin time (PTT) greater than 2 times the lab normal
• Admission platelets < 30,000
• Pre-existing neurological or psychiatric disease that could confound the study results
• Known severe allergy to contrast media
• Uncontrolled hypertension
• Computed tomography (CT) evidence of significant mass effect with a midline shift
• CT reveals evidence of large hypodensity region > 1/3 of the middle cerebral artery territory
• CT reveals evidence of intracranial hemorrhage
• CT reveals significant mass effect with midline shift
• Angiographic evidence of an arterial stenosis proximal to the occlusion that could prevent thrombus removal
• Angiographic evidence of preexisting arterial injury
• Life expectancy of less than 90 days
• Participation in another clinical investigation that could confound the evaluation of the study device.