[1] Natl Hosp Neurol & Neurosurg, Auton Unit, London, England
[2] Natl Hosp Neurol & Neurosurg, Charles Dent Metab Unit, London, England
[3] Univ Coll London Hosp, Gastrointestinal Physiol Unit, London, England
[4] Univ Coll London Hosp, Sleep Resp Serv, London, England
[5] Royal Free Hosp, UCL Dept Renal Med, London, England
[6] UCL, UCL Queen Sq Inst Neurol, London, England