1 Pediatric Neurology and Muscular Diseases Unit, IRCCS "G. Gaslini" Institute, Genova, Italy; Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, Genova, Italy; Department of Neuromuscular Diseases, Queen Square Institute of Neurology, University College of London, London, UK.
2 Department of Neuromuscular Diseases, Queen Square Institute of Neurology, University College of London, London, UK. Electronic address: h.houlden@ucl.ac.uk.