1 Epilepsy Society, Chalfont Centre, Chalfont St Peter, Bucks SL9 0RJ, UK.
2 Epilepsy Society, Chalfont Centre, Chalfont St Peter, Bucks SL9 0RJ, UK; UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK; National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK. Electronic address: l.sander@ucl.ac.uk.