TENSION (efficacy and safety of ThrombEctomy iN Stroke with extended leSION and extended time window: a randomized, controlled trial) strives at providing innovative treatment to patients with severe stroke to reduce the individual and societal burden of death and dependency from stroke. To this end, TENSION is a randomized, controlled, prospective, open label, blinded endpoint (PROBE) trial of thrombectomy in stroke patients with extended ischemic stroke lesions and patients presenting in a late time window, who are excluded from available effective treatment approaches based on current knowledge and guidelines. The aim of TENSION is to provide evidence to guide effective treatment in these patients. The trial will enroll up to 665 subjects in eight European countries. Outcome evaluation will involve a comprehensive array of clinical and safety parameters, health and socio-economic outcomes including patient reported outcome measures (PROM) for evaluation according to the principles of value-based healthcare. Health economic evaluation with cost-effectiveness analysis will be performed and gender-effects on treatment and outcome will be studied. Stroke is a major cause of death and disability in Europe with a large social and economic impact on patients, families, and society. The burden of stroke is in large parts determined by severe strokes resulting from the occlusion of large brain-supplying arteries. About 1.5 million people suffer from stroke in the EU each year with 10-20% severe strokes that might be candidates for thrombectomy, but in whom the benefit of treatment is uncertain. Based on current knowledge, no effective treatment is available for these patients, if brain lesions resulting from stroke are already extended and if patients arrive late in hospital, i.e. up to 12 hours of symptom onset. The central objective of TENSION is to assess whether stroke treatment using an existing currently available intervention, i.e. thrombectomy, improves clinical outcome, survival and quality of life in severe stroke patients with extended lesions and in an extended time window, as well. By this, TENSION will increase the population of stroke patients that may effectively be treated with thrombectomy. The larger demand for stroke thrombectomy together with the unequivocal demonstration of clinical benefit in a randomized controlled trial will foster area-wide implementation of thrombectomy and support establishment of interventional stroke in all European countries.