Endovascular Acute Stroke Intervention Trial - the EASI Trial

Stroke constitutes the primary cause of acquired disability in adults and the second cause of dementia following Alzheimer disease. It has been shown that patients with a moderate to severe clinical score have occlusion of brain large vessels, resulting in a worse clinical outcome. Many studies have demonstrated that early recanalization after IV rtPA is more restricted, the larger and more proximal the artery. Several systems for mechanical intracranial arterial thrombectomy of large trunks have recently been proposed and are now available. Potential advantages of these mechanical systems on chemical thrombolysis are speed (a few minutes versus 1 hour) and absence of thrombolytic injection. The objective of the EASI trial is thus to: * To validate intra-arterial thrombectomy use during the acute phase of cerebral stroke in patients treated with IV thrombolysis or in patients for whom thrombolysis is contra-indicated. * To determine whether a combined approach, standard treatment plus thrombectomy, is superior to standard treatment alone within 5 h of the appearance of symptoms, in patients with occlusion of proximal cerebral arteries following moderate to severe stroke (NIHSS larger than or equal to 8), evaluated at 3 months. The design is a randomized, controlled multicentric trial, with a parallel comparison between standard and combined (standard plus thrombectomy) treatment. 480 patients fulfilling eligibility criteria will be sufficient to demonstrate the primary hypothesis of a 15% difference in number of subjects with a favorable mRS (less than or equal to 2) at 3 months, with the assumption of a 25% efficacy for IV thrombolytic treatment at 3 months. IV thrombolysis is carried out according to standard practice. Mechanical thrombectomy is carried out with already approved devices, according to the manufacturer's instructions, following a diagnostic cerebral angiography. The primary efficacy endpoint is clinical: favorable mRS (less than or equal to 2)