[1] Univ Roma La Sapienza, Fac Med 1, Dept Cardiovasc & Resp Sci, Policlin Umberto I, I-00161 Rome, Italy
[2] Univ Roma La Sapienza, St Andrea Hosp, Azienda Osped S Andrea, Dept Neurol Sci, I-00161 Rome, Italy
[3] Univ Roma La Sapienza, Fac Med 1, Dept Internal Med, Policlin Umberto I, I-00161 Rome, Italy
[4] Tufts Univ New England Med Ctr, Boston, MA 02111 USA