[1] Ist Nazl Neurol Carlo Besta, Dept Neuromuscular Dis, I-20133 Milan, Italy
[2] Ist Ortoped Rizzoli, Neuromuscular Unit, Bologna, Italy
[3] Ist Nazl Neurol Carlo Besta, Epidemiol Unit, I-20133 Milan, Italy
[4] Univ Messina, Dipartimento Neurosci Sci Psichiatr & Anestesiol, I-98100 Messina, Italy
[5] Bambino Gesu Pediat Hosp, Dept Neurosci, IRCCS, Rome, Italy
[6] Univ Genoa, Ist Gaslini, Genoa, Italy
[7] Univ Turin, Ctr Malattie Neuromuscolari, Turin, Italy
[8] Univ Padua, Dipartimento Sci Neurol & Psichiatr, Padua, Italy