1. Faculty of Health, Department of Medicine, Witten-Herdecke University, 58455 Witten, Germany
2. Medical School Hamburg, 20457 Hamburg, Germany
3. Niels Stensen Neuro Center, Department of Neuro- and Spine Surgery, 49076 Osnabrück, Germany
4. St. Marien Hospital Lünen, Academic Teaching Hospital of University of Münster, 44534 Lünen, Germany
5. Department of Neurosurgery, Academic Hospital Cologne-Merheim, Witten-Herdecke University, 51109 Cologne, Germany
6. Department of Vascular and Endovascular Surgery, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50937 Cologne, Germany