1. Pain Therapy & Palliative Care Department, Medizinisches Zentrum Städteregion Aachen, Mauerfeldchen 25, 52146 Würselen, Germany.
2. Pain Therapy & Palliative Care Department, Medizinisches Zentrum Städteregion Aachen, Mauerfeldchen 25, 52146 Würselen, Germany
3. Department of Pain Medicine, Portsmouth Hospitals NHS Trust, D Level Theatres, Queen Alexandra Hospital, Southwick Hill Road, Portsmouth, Hants, PO6 3LY, UK
4. The Pain Service, Christie NHS Foundation Trust, c/o Critical Care Unit, Wilmslow Rd, Withington, Manchester, M20 4BX, UK
5. Centre for Pain Management & Palliative Care, Langenbeckplatz 2, 65189 Wiesbaden, Germany