1. Department of Neurosurgery, Klinikum rechts der Isar, Technische Universität München, Germany;
2. Department of Neurosurgery, Universitätsklinikum Innsbruck, Austria;
3. Department of Neurosurgery, Charité Universitätsmedizin Berlin, Germany;
4. Institute for Medical Informatics, Statistics and Epidemiology, Technische Universität München, Germany;
5. Department of Geriatric Medicine, Universität Duisburg-Essen, Geriatriezentrum Haus Berge, Essen, Germany; and
6. Department of Neurosurgery, University Medical Center Mainz, Germany