Catharina G Faber1, Ingemar S J Merkies2. 1. Department of Neurology, Maastricht University Medical Center, 6202 AZ, Maastricht, The Netherlands. Electronic address: c.faber@mumc.nl. 2. Department of Neurology, Maastricht University Medical Center, 6202 AZ, Maastricht, The Netherlands; Department of Neurology, Spaarne Hospital, 2130 AT, Hoofddorp, The Netherlands. Electronic address: isjmerkies@planet.nl.