1. Kuopio University Hospital; Department of Neurosurgery; Puijonlaaksontie 2 Kuopio Kuopio Finland 70029
2. University Medical Center Utrecht; Department of Neurology and Neurosurgery; PO Box 85500 Utrecht Netherlands 3508 GA
3. University Medical Center Utrecht; Department of Radiology; Heidelberglaan 100 Utrecht Netherlands 3508 GA
4. University Medical Center Utrecht; Julius Center for Health Sciences and Primary Care/Department of Neurology and Neurosurgery; PO Box 85500 Utrecht Netherlands 3508 GA
5. Leiden University Medical Center; Department of Neurology; Albinusdreef 2 Leiden Netherlands 2333 ZA
6. Queen's University Belfast; Centre for Public Health; Institute of Clinical Sciences, Block B, Royal Victoria Hospital Grosvenor Road Belfast Northern Ireland UK BT12 6BJ