SLC6A3 and supranuclear palsy, progressive, 1: Although SPECT has revealed some perfusion changes supratentorially in PSP, there have been no studies showing significant perfusion abnormality in the brainstem.174 Few studies comparing PSP with healthy controls have demonstrated reduced dopamine transporter binding with 123Ibeta-CIT in the midbrain177 and pons.176 Utilizing brainstem and striatal dopamine transporter binding together may improve differentiation of PSP from Parkinson’s.176