1. Department of Neurosurgery, Medical Center Haaglanden, The Hague, the Netherlands
2. Department of Neurosurgery, Leiden University Medical Center, Leiden, the Netherlands
3. Department of Medical Statistics and BioInformatics, Leiden University Medical Center, Leiden, the Netherlands
4. Department of Medical Decision Making, Leiden University Medical Center, Leiden, the Netherlands
5. Department of General Practice, Erasmus Medical Center, Rotterdam, the Netherlands
6. Department of Neurosurgery, Radboud University Medical Center, Nijmegen, the Netherlands
7. Department of Neurosurgery, Medical Center Alkmaar, Alkmaar, the Netherlands