1. Medical Faculty, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
2. Department of Neurosurgery, Alfried Krupp Hospital, Essen, Germany
3. Medical Faculty, Department of Diagnostic and Interventional Radiology, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
4. Department of Neurosurgery, Christliches Krankenhaus Quakenbrück gemeinnützige GmbH, Quakenbrück, Germany
5. Medical Faculty, Department of Neurosurgery, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
6. Department of Neurosurgery, St. Marien Hospital, Luenen, Germany
7. Department of Diagnostic and Interventional Radiology and Neuroradiology, St. Marien Hospital, Luenen, Germany