1. Department of Neurosurgery, The National Hospital, Rikshospitalet-Radiumhospitalet, Oslo, Norway
2. Department of Radiology, Neuroradiological Section, The National Hospital, Rikshospitalet-Radiumhospitalet, Oslo, Norway
3. Department of Otolaryngology, Head and Neck Surgery, The National Hospital, Rikshospitalet-Radiumhospitalet, Oslo, Norway