Since 2007, the COMA-TEAM in the Pitié-Salpêtrière Hospital has developed comaWeb a medical device that aimed at predicting neurological recovery of patients in intensive care that remain unresponsive at least 5 days after a major neurological accident (traumatic brain injury, cardiac arrest or subarachnoid haemorrhage). After 5 days, the question of therapeutic withdrawal or continuation arose for this severe brain injured patients. ComaWeb addresses the needs for reliable and quantitative information to help clinicians and patient’s families in this difficult decision making process. Up to now, due to the lack of reliable information and thus the lack of decision protocols, flawed decisions (1. decision to withdraw therapy for patients with a potential for recovery or 2. absence of decision of therapy withdrawal in patients without any potential of recovery leading to permanent vegetative state) may occur. This raises not only complex medical ethics questions but also Health economic issues when the total cost for the management of vegetative patient is from 1 to 2 M€. Thanks to a network of 20 centres in France, Italy and Belgium, we collected more than 1000 MRI exams on comatose patients. From this unique databank, reliable decision making models were derived. ComaWeb, our web platform, embeds secure remote access for the end-users to upload the patient’s data and retrieve, within 24h, comprehensive reports on lesion quantification from Diffusion MRI and prognosis values. Our project, COMAWEB-IMPACT, aims to address these major ethical issues (the end-of-life cares, the access for families to reliable individual information on actual brain lesions, the patient’s family involvement in the decision process based on proofs and data, the disparity of patient’s management in the European union, and within a specific countries, between different centres) as well as Health economics impact through the study of the impact of a wide implementation of comaWeb in 50 centres in Europe on costs. The key question we would like to address is, after reasserting the reliability of our prognosis tool, its utility. The COMAWEB-IMPACT project is a European trial assessing the clinical, neuro-psycho-social, economic, ethical and societal impact of the implementation of comaWeb as a personalised predictive tool in intensive care. More precisely, we proposed a 5-year parallel cluster randomized trial with a baseline period and a transition period. With the strong support of the European Society of Anaesthesiology, at least 50 European Intensive Care Units will be involved for patient’s inclusion, with stratification on groups of countries with similar medical cultures and practices. The coordination of COMAWEB-IMPACT will be ensured by the COMA-TEAM of the Pitié-Salpêtrière Hospital involving the Department of Anaesthesia and Intensive Care, APHP, and the Biomedical Imaging Laboratory, UPMC. This group is currently the world leader on the question of long-term prognosis with MRI in comatose patients that remain unresponsive after 5 days. After our experience as work package leader of the FP7 CENTER-TBI project, we will build this clinical trial network with the strong support of the European Society of Anaesthesiology. Implementation of comaWeb protocol in the clinical centres as well as river-run data quality checks and processing will be achieved by a dedicated spin-off created for developing the medical device. The core group ensuring high quality data collection will be reinforced with leading partners in Health economics (London School of Economics, UK), medical ethics (Radboud University Medical Center, NED) data analysis for decision making (Erasmus UMC, NED), imaging biomarkers development (Institut des Neuroscience de la Timone, FRA) and clinical epidemiology and biostatistics (BIOSPIM, FRA).