Ellen & Martin Prosserman Centre for Neuromuscular Diseases, Toronto General Hospital, University Health Network, University of Toronto, Toronto, Canada. Department of Neurology, UKD and Center for Neurology and Neuropsychiatry, LVR Klinikum, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany; Brain and Mind Centre, University of Sydney, Australia; Medical University of Vienna, Austria. CSL Behring, Marburg, Germany. CSL Behring, King of Prussia, PA, USA. Ellen & Martin Prosserman Centre for Neuromuscular Diseases, Toronto General Hospital, University Health Network, University of Toronto, Toronto, Canada. Electronic address: vera.bril@utoronto.ca.