Diffusion-weighted magnetic resonance imaging differentiates Parkinsonian variant of multiple-system atrophy from progressive supranuclear palsy.

Progressive supranuclear palsy (PSP) and the parkinsonian variant of multiple-system atrophy (MSA-P) may present with a similar phenotype. Magnetic resonance diffusion-weighted imaging (DWI) has been shown to be a sensitive discriminator of MSA-P from Parkinson's disease (PD). We studied 20 PSP, 11 MSA-P, 12 PD patients and 7 healthy controls in order to investigate whether regional apparent diffusion coefficients (rADCs) help distinguish PSP and MSA-P; whether rADCs are correlated with clinical disease severity scores; and the relationship between brainstem and cerebellar volumes and rADCs in PSP and MSA-P. The Unified Parkinson's Disease Rating Scale, Hoehn and Yahr score, Mini Mental State Examination, and frontal assessment battery were recorded in all patients. Regional ADCs were measured in the middle cerebellar peduncle (MCP), caudal and rostral pons, midbrain, decussating fibers of the superior cerebellar peduncle, thalamus, putamen, globus pallidus, caudate nucleus, corpus callosum, frontal and parietal white matter, as well as the centrum semiovale. In MSA-P, rADCs in the MCP and rostral pons were significantly greater than in PSP (P < 0.001 and 0.009) and PD (P < 0.001 and = 0.002). Stepwise logistic regression revealed that the MCP rADC distinguishes MSA-P from PSP with a sensitivity of 91% and a specificity of 84%. Increased brainstem rADCs were associated with motor deficit in MSA-P and PSP. Increased rADCs in the pons and MCP were associated with smaller pontine and cerebellar volumes in MSA-P. rADCs distinguish MSA-P from PSP. These have a clinical correlate and are associated with reduced brainstem and cerebellar volumes.