1. Department of Gynecology and Obstetrics, University of Duisburg-Essen, Essen
2. Institute for Medical Informatics, Biometry and Epidemiology, University of Duisburg-Essen DE
3. Department of Neurosurgery, University of Duisburg-Essen, Essen, Germany
4. Clinic of the Order of St. John, St. Hedwigs Clinic, University of Regensburg, DE