Inclusion Criteria- Age greater than or equal to 18
- NIHSS greater than or equal to 8
- onset of symptoms is less than 5 hours OR symptom/imaging mismatch
- suspected occlusion of the M1 or M2 segment of the MCA, supraclinoid ICA, or basilar trunk.
Exclusion Criteria- established infarction of the target symptomatic territory
- co-morbid diseases which suggest a poor 90 day outcome irrespective of management
- radiologic evidence of hemorrhagic transformation of the infarcted territory