1 Interdisciplinary Pain Center, Medical Center, Faculty of Medicine, University of Freiburg, University of Freiburg, Breisacherstr. 64, 79106, Freiburg, Germany.
2 Department of Anesthesiology, Pain Clinic, Khatam Ol Anbia Hospital, Tehran, Islamic Republic of Iran.
3 Interdisciplinary Pain Center, Medical Center, Faculty of Medicine, University of Freiburg, University of Freiburg, Breisacherstr. 64, 79106, Freiburg, Germany. tilman.wolter@uniklinik-freiburg.de.