Diagnostic accuracy of MR planimetry in clinically unclassifiable parkinsonism

Abstract

Introduction: Quantitative MR planimetric measurements were reported to discriminate between progressive supranuclear palsy (PSP) and non-PSP parkinsonism, yet few data exist on the usefulness of these markers in early disease stages. Methods: The pons-to-midbrain area ratio (P/M) and the Magnetic Resonance Parkinsonism Index (MRPI) as well as new indices, termed P/M2.0 and MRPI2.0, multiplying the former by a ratio of the third ventricle (3rdV) width/frontal horns (FH) width, were calculated on T1-weighted images in 84 patients with clinically unclassifiable neurodegenerative parkinsonism (CUP) at the time of imaging. Areas under the curve (AUCs) of these markers for predicting future PSP was determined. The final clinical diagnosis was made after at least 24 months of follow-up. Results: Final diagnosis was Parkinson's disease in 55 patients, multiple system atrophy in 12 cases, and PSP in 17. At baseline imaging, patients with a final PSP diagnosis had significantly higher MRPI, P/M, MRPI2.0 and P/ M2.0 values compared to the other groups. AUCs in discriminating between future PSP and non-PSP parkinsonism were 0.91 for both the P/M and the MRPI and 0.98 for the P/M2.0 and the MRPI2.0. Conclusions: Brainstem-derived MR planimetric measures yield high diagnostic accuracy for separating PSP from non-PSP parkinsonism in early disease stages when clinical criteria are not yet fully met. Consistent with the underlying pathology in PSP, our study suggests that inclusion of 3 rd V width makes P/M2.0 and MRPI2.0 more accurate in diagnosing early stage PSP patients than the P/M and MRPI.

Reply to: “Experience with a New Index to Differentiate Parkinson's Disease and Progressive Supranuclear Palsy”

“…In our study, 1 all PD patients in both cohorts were followed up for a period of 4 years, and we found no differences in 3 rd V/ID values between the baseline and follow-up evaluations, suggesting that the initial PD progression is not associated with the enlargement of the third ventricle. This is supported by a further recent study 4 in 84 patients with clinically unclassifiable neurodegenerative parkinsonism at the time of the MRI acquisition, where those 55 patients (disease duration at imaging 0.83 AE 0.41 years) with a final PD diagnosis 4 years after the imaging study had a similar 3rdV width (5.49 AE 1.24 mm) compared to our study. The PD cohort enrolled by Rau et al included patients with disease duration up to 15 years, and a contribution from such long disease duration to ventricular enlargement cannot be excluded.…”

Differentiating PSP from MSA using MR planimetric measurements: a systematic review and meta-analysis

“…Therefore, the MRPI2.0 and P/M2.0 including the measurement of the third ventricle width (MRPI or M / P multiplied by third ventricle width/frontal horns width ratio) were developed to increase diagnostic accuracy for PSP-P (Quattrone et al 2018 ). Indeed, validation studies showed that these two measures were more powerful in discriminating PSP-P from PD than the MRPI and P/M (Heim et al 2018 , 2021 ; Quattrone et al 2019 ), but there is a lack on studies exploring the diagnostic value of these two new measures in discriminating patients with PSP from MSA.…”

“…Atrophy of midbrain and superior cerebellar peduncle (SCP) are associated with PSP, and atrophy of pons and middle cerebellar peduncle (MCP) with the Parkinson variant of multiple system atrophy (MSA-P), respectively (Nicoletti et al 2006;Paviour et al 2005). The midbrain-to-pontine area ratio (M/P) and the MR parkinsonism index (MRPI) were introduced because single measurement of these brain structures failed to differentiate neurodegenerative parkinsonian syndromes on an individual basis (Paviour et al 2005;Seppi and Poewe 2010) and these quantitative MR planimetric measurements have been reported to differentiate PSP from PD and MSA with high diagnostic accuracy (Heim et al 2018(Heim et al , 2021Mangesius et al 2018). With regard to future therapeutic approaches, new studies are planned to influence the course of neurodegenerative diseases and, therefore, early diagnostic accuracy is crucial.…”

Diagnostic Performance of the Magnetic Resonance Parkinsonism Index in Differentiating Progressive Supranuclear Palsy from Parkinson’s Disease: An Updated Systematic Review and Meta-Analysis

“…After the removal of two duplicates, the screening of the titles and abstracts of the 519 remaining articles was performed, and the following 485 articles were excluded: 46 reviews, 37 case reports, 172 conference abstracts, three editorial/chapter/note, 216 articles that were not in the field of interest, one article with a partially overlapping cohort and 10 articles for which the reconstruction of 2 × 2 tables was not possible. A total of 34 full-text articles were further assessed for eligibility, and the following 20 articles were excluded: 12 articles that did not differentiate PSP from PD [ 12 , 13 , 14 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ], six articles that used the MRPI but differentiated between PSP and non-PSP [ 47 , 48 , 49 , 50 , 51 , 52 ], one article for which the reconstruction of a 2 × 2 table was not possible [ 53 ], and one article that was a meta-analysis [ 24 ]. Finally, 14 original articles involving 484 PSP patients and 1243 PD patients were included in our meta-analysis [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 23 , 54 , 55 , 56 , 57 , 58 , 59 ].…”

“…Several studies have evaluated the diagnostic performance of the MRI for the differentiation of atypical parkinsonism from PD using various measurement methods and techniques, i.e., measurement of the midbrain area, pons area to midbrain area ratio, or MRPI and voxel-based morphometry using a supervised machine learning algorithm [ 13 , 43 , 49 ]. Our updated meta-analysis focused on 14 articles that used the MRPI only for the differentiation of PSP from PD.…”