[1] Univ London Kings Coll Hosp, Univ Hosp Lewisham, Guys Kings & St Thomas Sch Med, Movement Disorders Unit, London SE5 9RS, England
[2] Carlos III Inst Hlth, Natl Ctr Epidemiol, Unit Neuroepidemiol, Madrid, Spain
[3] Royal Free Hosp, Sch Med, Dept Neurol, London, England
[4] Natl Hosp Neurol, London, England
[5] IRCCS NEUROMED, Inst Neurol, Pozzilli, Italy
[6] Med Coll Georgia, Dept Neurol, Augusta, GA 30912 USA
[7] Klinikum Bremerhaven Reinkenheide, Dept Neurol, Bremerhaven, Germany
[8] Kings Coll London, Inst Psychiat, Dept Psychol, London WC2R 2LS, England
[9] Univ N Carolina, Dept Neurol, Chapel Hill, NC USA
[10] Univ Naples, Dept Neurol, Naples, Italy
[11] So Gen Hosp, Dept Care Elderly, Glasgow G51 4TF, Lanark, Scotland
[12] UK Parkinsons Dis Soc, London, England
[13] Tel Aviv Univ, Sch Med, Assaf Harofeh Med Ctr, Zerifin, Israel
[14] Camborne Redruth Hosp, Dept Care Elderly, Redruth, Cornwall, England
[15] Royal Coll Nursing UK, Div Nursing, London, England
[16] Baylor Coll Med, Dept Neurol, Houston, TX 77030 USA
[17] Emory Univ, Dept Neurol, Atlanta, GA 30322 USA
[18] Univ Hosp Lewisham, Dept Neurol, London, England
[19] Univ London Kings Coll Hosp, Dept Neurol, Movement Disorders Sect, London, England
[20] N Tyneside Gen Hosp, Dept Med, N Shields, England
[21] St Thomas Hosp, Lane Fox Sleep Ctr, London, England
[22] CUNY Mt Sinai Sch Med, Dept Neurol, New York, NY 10029 USA