Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, California, USA. Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. Department of Neurology, UKD and Center for Neurology and Neuropsychiatry, LVR Klinikum, Heinrich Heine University, Dusseldorf, Germany. Department of Neurology, Nagoya University Graduate School of Medicine, Nagoya, Japan. CSL Behring, Marburg, Pennsylvania, USA. Ellen and Martin Prosserman Centre for Neuromuscular Diseases, Division of Neurology, Department of Medicine, University Health Network, University of Toronto, Toronto, Canada. Department of Neurology, Maastricht University Medical Center, Maastricht, the Netherlands and Curacao Medical Center, Curacao. Meridian HealthComms Ltd, Manchester, UK. Department of Neurology, Amsterdam University Medical Centres, University of Amsterdam, Amsterdam, the Netherlands and Spaarne Gasthuis, Haarlem, The Netherlands.