Background and objective: The parkinson variant of multiple system atrophy (MSA-P) and progressive supranuclear palsy (PSP) present with atypical parkinsonism, which may be misdiagnosed as PD, particularly in early disease stages. It was previously shown that diffusion-weighted MRI (DWI) is a sensitive tool to discriminate MSA-P from PD based on increased apparent diffusion coefficients (ADCs) in the putamen. In this study DWI was evaluated in 10 patients with PSP compared with 13 patients with PD and 12 with MSA-P.
Methods: Disease was diagnosed according to established diagnostic criteria and groups were matched for age, disease duration, and Hoehn and Yahr "off" stage. Regional ADCs (rADCs) were determined in different brain regions including basal ganglia, gray matter, white matter, substantia nigra, and pons.
Results: In patients with PSP compared with those with PD, rADCs were significantly increased in putamen, globus pallidus, and caudate nucleus. Stepwise logistic regression analysis followed by receiver operating characteristics analysis identified an optimal cut-off value for putaminal rADC, discriminating PSP and PD with a sensitivity of 90% and a positive predictive value of 100%. DWI failed to discriminate PSP and MSA-P.
Conclusions: These results show that DWI detects basal ganglia abnormalities in PSP patients within few years of disease onset, discriminating patients with PSP from those with PD, but not from those with MSA-P.