1. Department of Neurosurgery; KRH Klinikum Nordstadt; Hannover Germany
2. Center for Otorhinolaryngology, Head and Neck Surgery, Hirslanden Clinic; Zurich Switzerland
3. Department of Otorhinolaryngology, Head and Neck Surgery; Queen's Medical Centre, University Hospital; Nottingham United Kingdom
4. ENDOMIN-Centre for Endoscopic and Minimally Invasive Neurosurgery, Hirslanden Clinic; Zurich Switzerland