1 Department of Neurology, Adelaide and Meath Hospitals incorporating the National Children's Hospital, Dublin.
2 Department of Clinical Neurophysiology, Adelaide and Meath Hospitals incorporating the National Children's Hospital, Dublin.
3 Academic Unit of Neurology, Trinity College Dublin, Dublin, Ireland.
4 Neuromuscular and Neurogenetic Disorders of Childhood Section, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.