SLC6A3 and Parkinsonism: Our objectives in the current study were to (1) examine a cohort of United States Veterans with clinically diagnosed DIP using DAT-SPECT to identify those with or without underlying neurodegeneration, (2) characterize the pattern of nigrostriatal degeneration in those with abnormal DAT-SPECT, and (3) determine whether any objective clinical assessments, including quantitative gait analysis, either alone or in combination, can more accurately differentiate between degenerative and pharmacologic parkinsonism.