[1] Univ Ferrara, Neurol Clin, I-44100 Ferrara, Italy
[2] Azienda Osped Univ S Anna, UO Reumatol, Ferrara, Italy
[3] Azienda Osped Univ S Anna, Serv Neurofisiol Clin, Ferrara, Italy
[4] Ist C Besta, UO Malattie Neuromuscolari & Neuroimmunol, Milan, Italy