SLC6A3 and Parkinson disease: However, a 4-year longitudinal [123I]-FP-CIT SPECT study in 88 de novo PD patients revealed that elevated DAT availability within the caudate and putamen was associated with the presence of RLS at baseline and follow-up, compared to those without RLS (123), suggesting that PD patients with RLS may have a comparatively preserved presynaptic dopaminergic pathways.