1. Department of Neurosurgery, Justus-Liebig University Giessen, Klinikstrasse 33, 35392 Giessen, Germany
2. Institute of Quality Assurance Hesse, Frankfurter Strasse 10-14, 65760 Eschborn, Germany
3. Department of Neurology and Neurological Rehabilitation, Bezirkskrankenhaus Günzburg, Ludwig-Heilmeyer-Strasse 2, 89312 Günzburg, Germany