Faculty of Medicine, Dentistry and Health, The University of Sheffield, Sheffield S10 2TJ, UK. Sheffield Teaching Hospitals, Broomhall, Sheffield S10 2JF, UK. Maritime Hospital, Gillingham, Kent ME7 5NY, UK. 1st Department of Neurology, Aiginition University Hospital, National and Kapodistrian University of Athens, 115 28 Athina, Greece. Medical School, University of Cyprus, Shacolas Educational Centre for Clinical Medicine, Palaios dromos Lefkosias Lemesou No.215/6 2029 Aglantzia, Nicosia 1678, Cyprus.