1. VU University Amsterdam, Amsterdam UMC, VU Medical Center, Amsterdam, The Netherlands;
2. Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts;
3. Department of Neurosurgery, George Washington University School of Medicine and Health Sciences, Washington, DC;
4. Department of Neurosurgery, University Hospital of Larissa, Greece;
5. Department of Neurological Surgery, Germans Triasi Pujol University Hospital, Barcelona, Spain;
6. Department of Neurosurgery, University Hospital St. Ivan Rilski, Sofia, Bulgaria;
7. Victor Horsley Department of Neurosurgery, National Hospital for Neurology and Neurosurgery, London, United Kingdom;
8. Department of Neurosurgery, Haaglanden Medical Center, Den Haag, The Netherlands; and
9. Department of Neurosurgery, Leiden University Medical Center, Leiden, The Netherlands