1 ALS Centre, Neurology Unit, Maggiore della Carità Hospital, Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy.
2 Neurology Unit, S. Andrea Hospital, Department of Translational Medicine, University of Piemonte Orientale, 13100 Vercelli, Italy.
3 Division of Neuroscience, IRCCS San Raffaele Scientific Institute, 20132 Milan, Italy.