1. Department of Neurosurgery, Helsinki University Hospital, University of Helsinki, Helsinki, Finland;
2. Current Affiliations:Department of Neurosurgery, University Hospital Salzburg, Paracelsus Medical University, Salzburg, Austria;
3. The National Institute for Stroke and Applied Neurosciences, Auckland University of Technology, Auckland, New Zealand;
4. Department of Neurosurgery, Medical Center, University of Freiburg, Freiburg, Germany;
5. Department of Neurosurgery, Inselspital, Bern University-Hospital, Bern, Switzerland;
6. Department of Neurosurgery, University of Basel, Basel, Switzerland;
7. Department of Neurosurgery, Klinikum Nuremberg, Paracelsus Medical University, Nuremberg, Germany;
8. Department of Neurological Surgery, Northwestern University, Chicago, Illinois, USA;
9. Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA;
10. Department of Neurosurgery, University Hospital Salzburg, Paracelsus Medical University, Salzburg, Austria;
11. Department of Neurosurgery, München Klinik Bogenhausen, Munich, Germany;
12. Division of Neurosurgery, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada;
13. Department of Spine and Scoliosis Surgery, Artemed Klinikum München Süd, Munich, Germany;
14. Department of Neurosurgery, University Hospital St. Pölten, St. Pölten, Austria;
15. Department of Neurosurgery, Medical University of Innsbruck, Innsbruck, Austria