[1] Univ Edinburgh, Div Clin Neurosci, Western Gen Hosp, Edinburgh EH4 2XU, Midlothian, Scotland
[2] Osped BG Villa, Serv Aziendale Malattie Cerebrovasc, Citta Della Pieve, Italy
[3] Western Gen Hosp, Dept Radiol, Edinburgh EH4 2XU, Midlothian, Scotland
[4] Univ Birmingham, Dept Publ Hlth & Epidemiol, Birmingham B15 2TT, W Midlands, England