1. Department of Neurosurgery, Heinrich Heine University, Düsseldorf, Germany
2. Institute of Medical Biometry, Informatics and Epidemiology, University of Bonn, Bonn, Germany
3. Service de Neurochirurgie Fonctionnelle et Stereotaxique, Hôpital d'adulte de la Timone Marseille, France
4. Department of Stereotactic and Radiation Neurosurgery, Na Homolce Hospital, Prague Czech Republic
5. Dipartimento di Neuroscienze, Neurochirurgia, Università degli Studi di Milano, and Villa Maria Cecilia Hospital, Cotignola (RA) Italy
6. Gamma Knife Centre, Bupa Cromwell Hospital, London, UK
7. National Centre for Stereotactic Radiosurgery, Royal Hallamshire Hospital, Sheffield, UK
8. Department of Neurosurgery, Medical University of Vienna, Vienna, Austria
9. Department of Neurosurgery, Karolinska University Hospital, Stockholm, Sweden
10. Department of Functional Neurosurgery, Hospital Ruber Internacional, Madrid, Spain
11. Department of Neurosurgery, Haukeland University Hospital, Bergen, Norway
12. Department of Neurosurgery, University Hospital, Verona, Italy
13. Department of Neurosurgery, Medical University Graz, Graz, Austria
14. London Gamma Knife Centre, London, UK
15. Gamma Knife Center Zurich, Klinik Im Park, Zurich, Switzerland
16. Gamma Knife Centre, International Neuroscience Institute, Hannover, Germany
17. Gamma Knife Zentrum Krefeld, Krefeld, Germany