1. Department of Medicine, Faculty of Health, Witten/Herdecke University, Witten, Nordrhein-Westfalen, Germany
2. Department of Neurosurgery, Saint Barbara-Hospital Hamm-Heessen, Academic Hospital of Westfälische Wilhelms-University Münster, Hamm, Nordrhein-Westfalen, Germany
3. Department of Neurosurgery, Academic Hospital Köln-Merheim, Witten/Herdecke University, Köln, Nordrhein-Westfalen, Germany
4. Department of Spine Surgery, Asklepios Orthopedic Hospital Lindenlohe, Schwandorf, Bayern, Germany
5. Department of Neurosurgery, University Hospital Münster, Münster, Nordrhein-Westfalen, Germany
6. Department of Neurosurgery, Eberhard Karls University, Tübingen, Baden-Württemberg, Germany