Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
This work was in part supported by the Italian Ministry of Health (Ministero della Salute, Ricerca Sanitaria Finalizzata), the European Community's Health Seventh Framework Programme, the Joint Programme – Neurodegenerative Disease Research (Sophia Project), granted by Italian Health Ministry, the Fondazione Mario ed Anna Magnetto and the Associazione Piemontese per l’Assistenza alla SLA (APASLA).