1. German Paediatric Pain Centre, Children's and Adolescents' Hospital, Datteln, Germany
2. Department of Children's Pain Therapy and Paediatric Palliative Care, Faculty of Health, School of Medicine, Witten/Herdecke University, Witten, Germany
3. Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
4. Department of Anesthesiology & Pain Medicine, University of Washington School of Medicine, Seattle, WA, United States
5. Seattle Children's Research Institute, Seattle, WA, United States