1. Division of Neurological Pain Research and Therapy, Department of Neurology, Universitätsklinikum Schleswig-Holstein, Kiel, Germany
2. Clínica del Dolor, Hospital Universitari de Bellvitge, L’Hospitalet de Llobregat, Barcelona, Spain
3. Department of Clinical and Experimental Medicine, Division of Neurology, University Hospital, Linköping, Sweden
4. Grünenthal GmbH, Aachen, Germany
5. Pain Clinic, Gartnavel General Hospital, University of Glasgow, Glasgow, UK