1. Neurorehabilitation and Therapy Services Department, National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3BG, UK,
2. MRC Human Movement Group, Sobell Department for Motor Neuroscience and Movement Disorders, Institute of Neurology, Queen Square, London, WC1N 3BG, UK
3. Headache and Brain Injury and Rehabilitation, Institute of Neurology, Queen Square, London, WC1N 3BG, UK