1 Radboud University Medical Centre, Donders Institute for Brain, Cognition and Behaviour, Department of Neurology, Centre of Expertise for Parkinson & Movement Disorders, PO Box 9101 (947) 6500 HB Nijmegen, The Netherlands. Electronic address: bas.bloem@radboudumc.nl.
2 Dutch Parkinson Alliance, Amersfoort, The Netherlands.