1. Department of Neurology; University of Virginia; Charlottesville VA USA
2. MRC Centre for Neuromuscular Diseases; UCL Institute of Neurology; London UK
3. Department of Neurology, College of Medicine; University of Iowa; Iowa City IA USA
4. Clinic of Central and Peripheral Degenerative Neuropathies Unit, Department of Clinical Neurosciences; IRCCS Foundation, C. Besta Neurological Institute; Milan Italy
5. Department of Neurology; Adelaide & Meath Hospitals incorporating the National Children's Hospital, Trinity College Dublin; Dublin Ireland