Analysis of Eight Rating Scales Supports the use of Functional Outcome Measures in Prion Disease Clinical Trials: Experience from the PRION-1 trial and the National Prion Monitoring Cohort - Mead, S; Thompson, A; Gopalakrishnan, G; Ranopa, M; Rudge, P; Wroe, S; Hudson, F; MacKay, A; Darbyshire, J; Collinge, J; Walker, S (2010)