1. Department of Neurosurgery, University Medical Center, Mainz, Germany
2. Department of Neurosurgery, Helios Kliniken, Krefeld, Germany
3. Department of Neurosurgery, Technische Universität, München, Germany
4. Department of Spinal Surgery, Schön Klinik Hamburg, Eilbeck, Germany
5. Department of Neurosurgery, Helios Kliniken, Erfurt, Germany
6. Neurochirurgische Praxisklinik, Bielefeld, Germany
7. Department of Neurosurgery, Universitätsklinikum, Bonn, Germany
8. Competence Center for Spine and Pituitary Surgery, Nürnberg, Germany
9. Department of Neurosurgery, Universitätsklinikum, Freiburg, Germany