1. Department of Neurology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
2. Department of Neurology, Georgetown University Hospital, Washington, District of Columbia, USA.
3. Parkinson's Disease and Movement Disorder Center of Boca Raton, Boca Raton, Florida, USA.
4. Department of Neurology, Parkinson's Disease and Movement Disorder Center, University of Kansas Medical Center, Kansas City, Kansas, USA.