Objective: To improve diagnostic performance in distinguishing multiple system atrophy parkinsonian type (MSA-p), we investigated the iron deposition pattern in the putaminal lateral margin of non-MSA-p subjects and applied the findings in testing diagnostic conditions.

Background: Abundant iron in posterolateral areas of the putamen is a remarkable feature of MSA-p. Iron-sensitive imaging techniques enable early detection of iron deposition in the putamen of MSA-p so that it is included in the recently updated diagnostic criteria. [1] Visual assessment of iron-sensitive imaging faces several limitations. Iron deposition of the putamen progresses with aging, especially in the putaminal posterolateral part. Also, fundamental iron distributions could differ individually.

Method: This study included three groups: MSA-p (n=26), Parkinson’s disease (PD, n=68), and normal control (NC, n=41). Using a semi-automated algorithm, we obtained phase-shift values (PSVs) of 3T susceptibility-weighted images along the lateral margin, which reflect the iron concentration. We used the same study population and algorithm as in a previous study. [2] We divided the entire lateral rim into 10 segments (Segment 1 to 10) and used the mean value of each segment. Age-dependent phase-shift values in non-MSA-p subjects and a correlation analysis between age and all segments were evaluated. We tested combinations with or without normalization to determine the best diagnostic performance.

Results: The initial segment (Segment 1) of the putaminal lateral rim had consistent patterns and similar PSVs (p=0.540) regardless of disease group. The MSA-p group demonstrated higher PSVs than the PD and NC groups in the other segments. In non-MSA-p subjects, age and the PSV of Segment 1 (PSV-Seg1) were correlated with PSVs in most segments. The regression equations with age and the PSV-Seg1 were utilized for estimating the normalized PSVs for the MSA-p subjects. After testing various diagnostic conditions, the highest areas under the receiver operating characteristic curve (AUC) were 0.872 and 0.873 for separating MSA-p from PD and NC. The best performance was achieved by selecting a relatively prominent side and using the estimated PSVs from age and PSV-Seg1.

Conclusion: With a new personalized approach to reflect the age and individual iron background, the diagnostic process performed well in differentiating MSA-p from PD and NC.

References: [1] Wenning GK, Stankovic I, Vignatelli L, et al. The Movement Disorder Society Criteria for the Diagnosis of Multiple System Atrophy. Mov Disord 2022;37(6):1131-1148.
[2] Lee WW, Kim HJ, Lee HJ, et al. Semiautomated Algorithm for the Diagnosis of Multiple System Atrophy With Predominant Parkinsonism. J Mov Disord 2022;15(3):232-240.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/consideration-of-age-and-initial-putaminal-rim-segment-in-distinguishing-multiple-system-atrophy-parkinsonian-type/