Diffusion-weighted imaging in multiple system atrophy: a comparison between clinical subtypes.

Multiple system atrophy can be classified into two main types, a Parkinsonian (MSA-P) and a cerebellar (MSA-C) variant based on clinical presentation. We obtained diffusion-weighted magnetic resonance imaging (DWI) in 9 MSA-P and 12 MSA-C patients and 11 controls, and correlated DWI changes with disease duration and severity. We found that Trace (D) values in the entire and anterior putamen were significantly higher in MSA-P than in MSA-C patients and controls, whereas Trace (D) values in the cerebellum and middle cerebellar peduncle (MCP) were significantly higher in MSA-C than in MSA-P patients and controls. Increased disease duration was significantly correlated with increased Trace (D) values in pons of MSA-P patients, and in cerebellum and MCP of MSA-C patients. Both UMSARS and UPDRS motor scores positively correlated with entire and posterior putaminal Trace (D) values in MSA-P patients. The diffusivity changes parallel phenotypical and pathologic differences between MSA-P and MSA-C patients, suggesting that DWI is a feasible tool for in vivo evaluation of neurodegeneration in MSA. Based on our findings, Trace (D) measurements in the putamen and pons in MSA-P patients and in the cerebellum and MCP in MSA-C patients could serve as quantitative markers for microstructural damage in the course of disease.