The French part of OPHELIE-COG is run as an ancillary study of OPHELIE, a multicenter French study conducted in the clinical centres of the Strokavenir research network (co-PI Didier Leys, Lille and Denis Vivien, Caen). OPHELIE has been approved by the ethical committee and is an investigator-driven study supported by the INSERM, the University Lille Nord de France and the Lille University hospital. OPHELIE includes prospectively all patients who are treated by i.v. rt-PA for an acute cerebral ischaemia in the participating centres and tests the hypothesis that the single/two chain-tPA ratio in the infusion influences the 3-month outcome, evaluated by a score 0 or 1 at the modified Rankin scale(mRS). OPHELIE-COG is conducted in the same cohort of patients as an ancillary analysis of OPHELIE.