Biomarkers in Differentiating Parkinson Disease (PD) From Atypical Parkinsonisms
+ Indicates the effect was shown by only 1 article or that there are inconsistent results across studies; +++, effect shown consistently in 3 or more articles or in a multisite cohort; −, no effect of biomarker was shown. MRI indicates magnetic resonance imaging; MSA, multiple system atrophy; NA, not applicable; PET, positron emission tomography; PSP, progressive supranuclear palsy; SN, substantia nigra; SPECT, single-photon emission computed tomography.