[1] Hop La Pitie Salpetriere, INSERM, U289, F-75651 Paris 13, France
[2] Univ La Sapienza, Dipartimento Sci Neurol, Rome, Italy
[3] Hop Casanova, Serv Neurol, St Denis, France
[4] Univ Naples Federico II, Dipartimento Sci Neurol, Naples, Italy
[5] Inst Neurol, London WC1N 3BG, England