C Champeaux1, C Shieff2. 1. Department of Neurosurgery, Institute of Neurological Sciences, Southern General Hospital, 1345 Govan Road, G51 4TF, Glasgow, UK. Charles.Champeaux@gmail.com. 2. Victor Horsley Department of Neurosurgery, National Hospital for Neurology and Neurosurgery, Queen Square, WC1N 3BG, London, UK.