Department of Neurology, University Medical Center Groningen, University of Groningen, PO Box 30.001, 9700 RB, Groningen, the Netherlands; Expertise Center Movement Disorders Groningen, University Medical Center Groningen (UMCG), PO Box 30.001, 9700 RB, Groningen, the Netherlands. Electronic address: anouk.kuiper@radboudumc.nl.