Acute ischemic stroke (AIS) is one of the main causes of disability and loss of quality adjusted life years. This study is to analyze whether endovascular therapy (EVT) in addition to best medical treatment (BMT) reduces the degree of disability and dependency in daily activities after a Medium Vessel Occlusion (MeVO) stroke compared to BMT alone.

Acute ischemic stroke (AIS) is one of the main causes of death and disability and thereby the third leading cause of loss of quality adjusted life years. For patients with an AIS due to an occlusion of the large vessels of the anterior circulation, endovascular therapy (EVT) has become a treatment standard. 20-40% of all AIS patients have occlusions of smaller vessels and present with a more distal isolated Medium Vessel Occlusion (MeVO). The primary objective of this randomized trial is to determine whether patients experiencing an AIS due to an isolated medium vessel occlusion have superior functional outcome (measured with the Modified Rankin Scale "mRS" at 90 days) when treated with EVT plus best medical treatment (BMT) compared to patients treated with BMT alone. In this trial, all commercially available, CE-certified revascularisation devices (i.e. stent-retriever, aspiration catheters and balloon guide catheters) can be used for EVT. All established techniques for the endovascular treatment of AIS patients are permitted and all decisions regarding treatment technique and choice of devices and/or medications are made solely by the treating physician.

Inclusion Criteria:

• Acute ischemic stroke
• Treatment (arterial puncture) can be initiated 2.1. Within 6 hours of last seen well (LSW) OR 2.2. Within 6 to 24 hours of LSW AND
• CT Criteria: Evidence of a hypoperfusion-hypodensity mismatch (Absence of hypodensity on the noncontrast CT within ≥ 90% of the area of the hypoperfused lesion on perfusion CT)
• MRI Criteria: Evidence of a diffusion-hyperintensity mismatch (Absence of hyperintensity on fluid-attenuated inversion recovery (FLAIR) imaging within ≥ 90% of the area of the diffusion weighted imaging(DWI) lesion)
• Isolated medium vessel occlusion (i.e. an occlusion of the co-/non-dominant M2, the M3/M4 segment of theMCA, the A1/A2/A3 segment of the ACA or the P1/P2/P3 segment of the PCA) confirmed by CT or MRIAngiography
• National Institute of Health Stroke Scale (NIHSS) Score of ≥ 4 points or symptoms deemed clearly disabling by treating physician (i.e. aphasia, hemianopia, etc.)
• Informed Consent as documented by signature or fulfilling the criteria for emergency consent/ deferral consent
• Agreement of treating physician to perform endovascular procedure

Exclusion Criteria:

• Acute intracranial haemorrhage
• Patient bedridden or presenting from a nursing home
• In-Hospital Stroke
• Known (serious) sensitivity to radiographic contrast agents, nickel, titanium metals or their alloys
• Foreseeable difficulties in follow-up due to geographic reasons (e.g. patients living abroad)
• Pregnancy or lactating women. A negative pregnancy test before randomisation is required for all women with child-bearing potential.
• Known history of arterial tortuosity, pre-existing stent, other arterial disease and/or known disease at the arterial access site that would prevent the device from reaching the target vessel and/or preclude safe recovery after EVT
• Severe comorbidities, which will likely prevent improvement or follow-up
• Radiological confirmed evidence of mass effect or intracranial tumour (except small meningioma)
• Radiological confirmed evidence of cerebral vasculitis
• Evidence of vessel recanalization prior to randomisation
• Participation in another interventional trial

A treatment-blinded person will assess the primary outcome dependency and disability in everyday life (measured with the modified Rankin Scale (mRS)) at 90 days. All interviewers will be certified for the conductance of mRS.

interviews.