SLC6A3 and Parkinson disease: There were no correlations between mean height of letters or area of the handwriting sample and striatal DAT binding in any of the studied brain regions in PD patients with consistent micrographia (n = 13, Spearman − 0.253 < r < 0.152, p > 0.404) or between b-value of the regression line and striatal DAT binding in any of the studied brain regions in PD patients with progressive micrographia (n = 13, Spearman − 0.296 < r < 0.011, p > 0.326) (Supplementary Fig. 1).