S K Chhetri1, R J Mills2, S Shaunak2, H C A Emsley3. 1. Department of Neurology, Royal Preston Hospital, Preston PR2 9HT, UK University of Manchester, Manchester M13 9PL, UK. 2. Department of Neurology, Royal Preston Hospital, Preston PR2 9HT, UK. 3. Department of Neurology, Royal Preston Hospital, Preston PR2 9HT, UK University of Manchester, Manchester M13 9PL, UK hedley.emsley@manchester.ac.uk.