 Background: Intravenous thrombolysis IVT and intra-arterial thrombolysis IAT have been shown to be effective treatments for acute stroke in controlled randomized trials and meta-analyses. However, prospective studies comparing IVT and IAT have not been performed, and it is not known which patients benefit more from IVT or IAT. Non-invasive neurovascular imaging techniques such as magnetic resonance angiography MRA or computed tomography angiography CTA have the potential to improve patient selection for the optimal mode of thrombolytic therapy and provide data of pre-treatment neurovascular findings of patients treated with IVT. IAT series have identified several prognostic factors for favourable or poor outcome predictors such as vessel recanalization, location of the vascular occlusion or NIHSS at admission. Additional studies have shown that recanalization rates in patients with central ves-sel occlusions such as middle cerebral artery MCA main stem or MCA main branch or basilar artery BA is higher when treated with IAT compared to IVT. Therefore, the investigators hypothesize that IAT might be more efficacious in these patients. 