• The modified Rankin Scale score [ Time Frame: at 90 days post-stroke ] [ Designated as safety issue: No ]
  

• Median change in NIH Stroke Scale score, Global test statistic at day 90, hemorrhagic transformation at day 7, serious adverse events, day 90 mortality. [ Time Frame: at day 90 ] [ Designated as safety issue: No ]
  

Stroke most commonly occurs when there is a blockage of blood flow to one of the arteries in the brain. The blockage is often caused by a clot. There is currently only one FDA-approved stroke treatment. However, only 2 percent of ischemic stroke patients receive this treatment because it must be given within 3 hours of the stroke onset. There is an overwhelming need for new treatments that extend the time window to treatment since most individuals with stroke arrive at the hospital after the 3-hour time window.

One of the most promising new devices is the Merci Retriever, a tiny corkscrew device designed to remove clots from arteries and thereby restore blood flow to the brain.

The primary purpose of this study is to compare the effectiveness of treatment with the Merci Retriever within 8 hours of symptom onset to standard medical treatment, and to identify people who might benefit from the device by the appearance of the stroke on magnetic resonance imaging (MRI). Previous testing has determined that the use of the Merci Retriever is successful in opening up blocked blood vessels in approximately ½ of the individuals in whom it is used.

A total of 120 participants from approximately 30 different medical centers will be enrolled into this study. Participants will be randomized to receive treatment either with the Merci Retriever and standard medical care or standard medical care alone. Standard care for stroke patients may include intravenous fluid, careful regulation of blood pressure, blood-thinning medicine (such as heparin or warfarin), anti-platelet medicine (such as aspirin or clopidogrel), and rehabilitation therapies.

Participants receiving the Merci Retriever will have 2 cerebral arteriograms——one prior to the procedure to determine the location of the blockage, and another following the procedure to determine if blood supply has been restored. The total Merci Retriever procedure will take approximately 1 to 2 hours. Participants will have brief neurological exams several times during this time to monitor changes in their neurological condition.

Participants will have follow-up visits, including neurological exams, at 30 days and at 90 days.

This study is part of the Specialized Program of Translational Research in Acute Stroke (SPOTRIAS), which allows researchers to enhance and initiate translational research that ultimately will benefit stroke patients by treating more patients in less than 2 hours, and finding ways to treat additional patients later.

Inclusion Criteria:

• New focal disabling neurologic deficit consistent with acute cerebral ischemia (NIHSS >/= 6)
• Age >/= 18 ≤ 85
• Clot retrieval procedure can be initiated within 8 hours from onset
• Large vessel proximal anterior circulation occlusion on MR angiography (internal carotid, M1 or M2 MCA)
• Pretreatment MRI performed according to MR RESCUE protocol
• Signed informed consent obtained from the patient or patient's legally authorized representative
• Premorbid modified Rankin score of 0-1

Exclusion Criteria:

• NIHSS >/= 30
• Contraindication to MRI (pacemaker etc)
• Acute intracranial hemorrhage
• Coma
• Rapidly improving neurological signs prior to randomization
• Patient meets Health Canada and FDA approved criteria for intravenous t-PA (these patients will receive conventional IV t-PA treatment)
• Pre-existing medical, neurological or psychiatric disease that would confound the neurological, functional, or imaging evaluations
• Pregnancy
• Renal Failure (serum Creatinine > 2.0) unless patient is dialysis dependent
• Known allergy to iodine previously refractory to pretreatment medications
• Current participation in another experimental treatment protocol
• Contrast-Enhanced Neck MRA suggests proximal ICA occlusion, proximal carotid stenosis > 67%, or dissection
• INR > 3.0
• PTT > 3 x Normal
• Diffusion-perfusion data cannot be processed by the MR RESCUE computer