Previous work has shown that analyses of extrastriatal 123I-FP-CIT binding may contribute to the differential diagnosis of parkinsonian syndromes, in that not only striatal DAT binding is lower in PSP and MSA-P than in PD but also extrastriatal binding may be lower in some brain areas such as the diencephalon (21,63). This evidence concerns the gene SLC6A3 and supranuclear palsy, progressive, 1.