1. Swiss Paraplegic Research, CH-6207 Nottwil, Switzerland
2. Centre for Pain Medicine, Swiss Paraplegic Centre, CH-6207 Nottwil, Switzerland
3. Faculty of Health Sciences and Medicine, University of Lucerne, CH-6002 Lucerne, Switzerland
4. Institute of Social and Preventive Medicine, University of Bern, CH-3012 Bern, Switzerland