1. Division of Neurodegenerative Disorders, Department of Neurology, Medical Faculty Mannheim, Mannheim Center for Translational Neurosciences, Heidelberg University, Mannheim, Germany
2. Department of Neurology, Centre for ALS and Other Motor Neuron Disorders, Alfried Krupp Krankenhaus Rüttenscheid, Essen, Germany
3. Department of Neurology, University Ulm, Ulm, Germany
4. Department of Clinical Sciences, Neurosciences, Umeå University, Umeå, Sweden, and
5. Department of Neurology, Diakonissen Hospital Mannheim, Mannheim, Germany