This is a case of don't be fooled by the initial non-contrast CT. There is an old stroke but nothing to explain the patient's new sudden onset symptoms. Perfusion clearly shows a large area of perfusion abnormality in the posterior circulation with CTA and DSA both showing a filling defect. 

Clot retrieval (mechanical thrombectomy) has become standard of care for patients with some acute stroke patients. Important factors in patient selection includes relatively proximal thrombus, severity of symptoms, and lack of large established infarct.