1 Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, PA; Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Electronic address: vandervera@email.chop.edu.
2 Department of Neuropediatrics, Jena University Hospital, Jena, Germany; Center for Rare Diseases, Jena University Hospital, Jena, Germany. Electronic address: Ralf.Husain@med.uni-jena.de.