1 MDUK Oxford Neuromuscular Centre, Department of Paediatrics, University of Oxford and NIHR Oxford Biomedical Research Center, Oxford OX3 9DU, United Kingdom.
2 Neuromuscular Center of Liège, Division of Paediatrics, CHU and University of Liège, 1 Bvd du XII de Ligne, Liège 4000, Belgium.