High Coverage CARotid Stenting vs. Medical Management Alone to Prevent EmboliSm From symptomaTic Non-stenotic cARotid Disease (SyNC)

Inclusion Criteria: * Patients diagnosed with acute ischemic stroke or acute retinal artery ischemia within the last two weeks related to symptomatic non-stenotic carotid disease (SyNC) and high-risk carotid plaque features * Ipsilateral acute ischemic stroke must be determined by acute ischemic infarct on DWI or CT OR * by neurological symptoms indicating ipsilateral cortical deficits consistent with ischemia in the territory of the internal carotid artery and after exclusion of a significant microangiopathy * Acute retinal artery ischemia must be determined by ophthalmologic examination * Patients with no other identifiable cause of stroke, evaluated using standard echocardiographic examinations to exclude cardiogenic or aortogenic sources of embolism * Symptomatic non-stenotic carotid disease defined as one or more plaques in the ipsilateral internal carotid artery causing 10-49% luminal narrowing AND * Presence of high-risk plaque features which must be determined through visual inspection on CTA or MRI (Ultrasound findings alone are insufficient; features must be confirmed by CTA or MRI to meet the criteria): * Identification of at least two of the following characteristics Plaque thickness ≥ 3mm Irregular plaque surface Ulceration \<50% plaque calcification Lipid-rich necrotic core * and/or identification of at least one of the following characteristics Intraplaque haemorrhage * Presence of carotid web characterized as shelf-like/linear, smooth filling defects * Plaque assessment including evaluation of the presence of high-risk features by routine imaging (CTA, MRI) confirmed by an independent CoreLab * Signed Informed Consent Form * Patient ≥ 18 years * mRS ≤ 3 at time of randomisation * Dual antiplatelet therapy (DAPT) according to standard of care before endovascular treatment Exclusion Criteria: * Patients with acute complete occlusion of the carotid artery in an emergency setting * Incidence of acute infarcts in other vascular (i.e., not ipsilateral carotid) territories * Patients in whom the stroke was likely caused by one of the following diseases: * Small vessel disease * Large vessel atherosclerotic disease ≥ 50% * Cardioembolism * Other known disease e.g. vasculitis * Predominantly calcified Plaques (≥50% calcified plaque components on CT-Angio) * Patients presenting with intraluminal carotid thrombus (e.g. characterized by 'donut sign' on CTA) * Patients with highly tortuous vessels (\>90°) which may prevent access or safe insertion of the stent * Patients with post-CEA re-stenosis or post-CAS re-stenosis * Patients with blood coagulation disorders * Patients in whom access to the carotid lesion is impossible or associated with an increased risk of procedural complications * Patients with lesions in the ostium of the common carotid artery * Patients with known hypersensitivity to nickel-titanium * Patients who are allergic to heparin * Any known conditions that affect life expectancy to less than 12 months * Any known conditions associated with an increased risk of endovascular treatment * Patients not able to visit the outpatient clinic for annual follow-up