1 Centre for Pain Management and Palliative Care/Regional Centre of Excellence in Palliative Care, Haukeland University Hospital, Bergen 5021, Norway Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University, Baltimore, MD 21205, USA Pain Clinic, Department of Anaesthesia and Intensive Care, Helsinki University Central Hospital and Institute of Clinical Medicine, Faculty of Medicine, University of Helsinki, Helsinki, Finland "Homéostasie-Allostasie-Pathologie-Réhabilitation", CNRS UMR 5287 - INCIA, Institut de Neurosciences cognitives et intégratives d'Aquitaine, Université Victor Segalen, Bordeaux 2, France.