1. School of Medicine, University of Cagliari, 09124 Cagliari, Italy
2. St Thomas Hospital, Guy’s and St Thomas NHS Foundation Trust, London SE1 7EH, UK
3. Department of Neurosurgery, Niguarda Cà Granda Hospital, 20162 Milan, Italy
4. Department of Surgical Science, University of Cagliari, 09124 Cagliari, Italy