Vector plots of change scores. Data are changed from initial values (A) and normalised for different lengths of follow-up time and shown as the average change per year (B). The black arrow is the mean vector in both graphs and the length of the arrows in (B) are directly comparable. It can be seen that some patients progress much faster than others. The top left quadrant represents disease progression on both the tapping and UHDRS scores, with 15 of the 17 patients progressing on both of these measures. Patients that do not follow the general trend stand out: one patient had a slight improvement on the tapping score with a slight deterioration on the UHDRS score (top right quadrant), while another had a slightly improved UHDRS score with an annual decrease on the number of taps that was about average (bottom left quadrant). "+" = Improvement, "-" = Deterioration.