1. Department of Neurosurgery, Department of Public Health, Erasmus Medical Center Rotterdam, Rotterdam, The Netherlands.
2. Center for Medical Decision Making, Department of Public Health, Erasmus Medical Center Rotterdam, Rotterdam, The Netherlands.
3. Department of Medical Statistics and Bioinformatics, Leiden University Medical Center, Leiden, The Netherlands.
4. Department of Neurosurgery, Antwerp University Hospital and University of Antwerp, Edegem, Belgium.