University of Duisburg-Essen, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, University of Duisburg-Essen - Department of Neurosurgery, University of Duisburg-Essen, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, University of Duisburg-Essen - University Hospital Essen, affiliation not provided to SSRN, University of Duisburg-Essen - Department of Neurosurgery and University of Duisburg-Essen - University Hospital Essen