[1] Georgetown Univ, Dept Neurol, Washington, DC USA
[2] Parkinson Klin Ortenau, Wolfach, Germany
[3] Med Univ Warsaw, Dept Neurol, Fac Hlth Sci, Warsaw, Poland
[4] Vrije Univ Brussel, Dept Otorhinolaryngol, Univ Hosp Brussels, Brussels, Belgium
[5] Neurol Outpatient Clin Parkinson Dis & Deep Brain, Gera, Germany
[6] Med Univ Gdansk, Dept Neurol Psychiat Nursing, Gdansk, Poland
[7] St Adalbert Hosp, Dept Neurol, Gdansk, Poland
[8] Med Univ Lodz, Dept Extrapyramidal Dis, Lodz, Poland
[9] Med Univ Silesia, Dept Neurol, Katowice, Poland
[10] Med Univ Silesia, Stroke Unit, Katowice, Poland
[11] Jagiellonian Univ, Dept Neurol, Coll Med, Krakow, Poland
[12] Merz Pharmaceut GmbH, Frankfurt, Germany
[13] Columbia Univ Coll Phys & Surg, Dept Otolaryngol Head & Neck Surg, 630 W 168th St, New York, NY 10032 USA
[14] Icahn Sch Med Mt Sinai, Dept Neurol, New York, NY 10029 USA
[15] NY Ctr Voice & Swallowing Disorders, New York, NY USA