[1] Cardiff Univ, Inst Psychol Med & Clin Neurosci, Heath Pk, Cardiff CF14 4XN, S Glam, Wales
[2] Univ Hosp Wales, Heath Pk, Cardiff CF14 4XN, S Glam, Wales
[3] Univ Hosp Wales, Dept Neurol, Cardiff, S Glam, Wales
[4] Univ Hosp Llandough, Dept Resp Med, Llandough, Wales
[5] Royal Gwent Hosp, Dept Resp Med, Newport, Gwent, Wales
[6] Royal Gwent Hosp, Dept Neurol, Newport, Gwent, Wales
[7] Addenbrookes Hosp, Dept Neurol, Cambridge, England