Differentiation of Parkinsonism-Predominant Multiple System Atrophy from Idiopathic Parkinson Disease Using 3T Susceptibility-Weighted MR Imaging, Focusing on Putaminal Change and Lesion Asymmetry

Abstract

Background and purpose: Asymmetric presentation of clinical feature in parkinsonism is common, but correlatable radiologic feature is not clearly defined. Our aim was to evaluate 3T susceptibility-weighted imaging findings for differentiating parkinsonism-predominant multiple system atrophy from idiopathic Parkinson disease, focusing on putaminal changes and lesion asymmetry.

Materials and methods: This retrospective cohort study included 27 patients with parkinsonism-predominant multiple system atrophy and 50 patients with idiopathic Parkinson disease diagnosed clinically. Twenty-seven age-matched subjects without evidence of movement disorders who underwent SWI were included as the control group. A consensus was reached by 2 radiologists who visually assessed SWI for the presence of putaminal atrophy and marked signal hypointensity on each side of the posterolateral putamen. We also quantitatively measured putaminal width and phase-shift values.

Results: The mean disease duration was 4.7 years for the patients with parkinsonism-predominant multiple system atrophy and 7.8 years for the patients with idiopathic Parkinson disease. In the patients with parkinsonism-predominant multiple system atrophy, putaminal atrophy was frequently observed (14/27, 51.9%) and was most commonly found in the unilateral putamen (13/14). Marked signal hypointensity was observed in 12 patients with parkinsonism-predominant multiple system atrophy (44.4%). No patients with idiopathic Parkinson disease or healthy controls showed putaminal atrophy or marked signal hypointensity. Quantitatively measured putaminal width, phase-shift values, and the ratio of mean phase-shift values for the dominant and nondominant sides were significantly different between the parkinsonism-predominant multiple system atrophy group and the idiopathic Parkinson disease and healthy control groups (P < .001).

Conclusions: 3T SWI can visualize putaminal atrophy and marked signal hypointensity in patients with parkinsonism-predominant multiple system atrophy with high specificity. Furthermore, it clearly demonstrates the dominant side of putaminal changes, which correlate with the contralateral symptomatic side of patients.

Fig 1.

Measurement of putaminal width and mean phase-shift values from corrected phase images by using ImageJ software. A, Three lines crossing the mid-, posterior half, and far posterior putamen are drawn to allow measurements. B, The corresponding plot profile of the line crossing the far posterior portion of the putamen demonstrates increased phase-shift values in both putamina (arrows).

Fig 2.

Distribution of putaminal atrophy (A) and posterolateral putaminal signal intensity (B) in each group. Putaminal atrophy: 0 = negative, 1 = suspicious, 2 = definite; posterolateral putaminal signal intensity: 0 = hyperintense, 1 = isointense, 2 = hypointense, 3 = markedly hypointense.

Fig 3.

A 71-year-old woman who initially presented with right-leg dragging 3 years ago was clinically diagnosed as having probable MSA-p. A, On the T2-weighed axial image, the bilateral posterolateral putamen shows subtle hypointensity. The phase image (B) and final SWI (C) show a marked phase shift in the left posterolateral putamen with loss of lateral convexity of the posterolateral aspect of the putamen, suggesting atrophic change. D, Phase values along the far posterior of both putamina show asymmetric phase-shift values, and mean phase-shift values of the left putamina are measured as 2686.5 Siemens Phase Units.

Fig 4.

A 69-year-old woman who initially presented with gait disturbance and bradykinesia 8 years ago was clinically diagnosed with IPD. The T2-weighed axial image (A), phase image (B), and final SWI (C) show no substantial signal alteration or atrophy in the bilateral putamina, while excessive iron deposition in the bilateral globus pallidus is observed. D, Phase values along the far posterior portion of both putamina show symmetric phase-shift values, and mean phase-shift values of the right and left putamina are measured as 2114.5 and 2111.7 Siemens Phase Units, respectively.

Fig 5.

Receiver operating characteristic curves of values measured at the far posterior putamen to distinguish MSA-p from IPD.