1. Faculty of Medicine, University of Oslo, and Department of Neurosurgery, Oslo University Hospital, Ullevål, Oslo, Norway
2. Department of Neurosurgery, Oslo University Hospital, Rikshospitalet, Oslo, Norway
3. Department of Radiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
4. The Norwegian Cancer Registry, Oslo, Norway
5. Department of Pathology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
6. Faculty of Medicine, University of Oslo, Department of Neurosurgery, Oslo University Hospital, Ullevål; and Department of Neurosurgery, Oslo University Hospital, Rikshospitalet, Oslo, Norway
7. Department of Neurosurgery, Oslo University Hospital, Ullevål, Oslo, Norway
8. Department of Pathology, Oslo University Hospital, Ullevål, Oslo, Norway