1. Unit of Neurosurgery, IRCCS Ca’ Granda Foundation Ospedale Maggiore Policlinico, Via Francesco Sforza, 35, 20122 Milan, Italy
2. Department of Medical and Surgical Pathophysiology and Transplantation, University of Milan, 20122 Milan, Italy
3. Department of Neurosurgery, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK