Segmental Alterations of the Corpus Callosum in Progressive Supranuclear Palsy: A Multiparametric Magnetic Resonance Imaging Study.

Lavinia A Bârlescu,Hans-Jürgen Huppertz,Jan Kassubek,Albert C Ludolph,Hans-Peter Müller,Ingo Uttner,Elmar H Pinkhardt

doi:10.3389/fnagi.2021.720634

Abstract

Background: The regional distribution of the widespread cerebral morphological alterations in progressive supranuclear palsy (PSP) is considered to include segmental parts of the corpus callosum (CC).Objective: The study was designed to investigate the regional white matter (WM) of the CC by T1 weighted magnetic resonance imaging (T1w MRI) data combined with diffusion tensor imaging (DTI) data in PSP patients, differentiated in the variants Richardson syndrome and PSP-parkinsonism, and to compare them with Parkinson’s Disease (PD) patients and healthy controls, in order to identify macro- and micro-structural alterations in vivo.Methods: MRI-based WM mapping was used to perform an operator-independent segmentation for the different CC segments in 66 PSP patients vs. 66 PD patients vs. 44 matched healthy controls. The segmentation was followed by both planimetric and texture analysis of the separated CC areas for the comparison of the three groups. Results were complemented by a DTI-based tract-of-interest analysis of the associated callosal tracts.Results: Significant alterations of the parameters entropy and homogeneity compared to controls were observed for PSP as well as for PD for the CC areas I, II, and III. The inhomogeneity in area II in the PSP cohort was the highest and differed significantly from PD. A combined score was defined as a potential marker for the different types of neurodegenerative parkinsonism; receiver operating characteristics (ROC) curves were calculated with areas under the curve values of 0.86 for PSP vs. controls, 0.72 for PD vs. controls, and 0.69 for PSP vs. PD, respectively.Conclusion: The multiparametric MRI texture and DTI analysis demonstrated extensive alterations of the frontal CC in neurodegenerative parkinsonism, whereas regional CC atrophy cannot be regarded as a constant neuroimaging feature of PSP. Specifically, the comparison PSP vs. PD revealed significant alterations in callosal area II. The combination of the texture and the DTI parameters might contribute as a neuroimaging marker for the assessment of the CC in PSP, including the differentiation vs. PD.

Highlights

Progressive supranuclear palsy (PSP) as one cause of atypical neurodegenerative parkinsonism is recognized as a range of movement, behavioral, and language syndromes associated with a characteristic 4-repeat tau neuropathology (Boxer et al, 2017), pathologically characterized by tau protein deposition, neuronal loss, and gliosis affecting the brainstem, subcortical, and cortical structures (Litvan et al, 1996; Kovacs et al, 2020)
The O1 and O2 levels had to be associated with postural instability (P1, repeated unprovoked falls within 3 years; or P2, tendency to fall on the pull test within 3 years) for a diagnosis of PSP-RS, while these ocular signs had to be associated with A2 or A3 for a diagnosis of PSP-P
To detect whether this is a common feature in PSP and/or Parkinson’s disease (PD), this imaging sign was investigated by planimetry of the midsagittal corpus callosum (CC) areas, using Atlas-Based Volumetry (ABV) and Tensor Imaging and Fiber Tracking (TIFT) for mutual comparison and validation

Summary

Introduction

Progressive supranuclear palsy (PSP) as one cause of atypical neurodegenerative parkinsonism is recognized as a range of movement, behavioral, and language syndromes associated with a characteristic 4-repeat tau neuropathology (Boxer et al, 2017), pathologically characterized by tau protein deposition, neuronal loss, and gliosis affecting the brainstem, subcortical, and cortical structures (Litvan et al, 1996; Kovacs et al, 2020). Recent MRI approaches to PSP by diffusion weighted imaging focused on the differentiation of the findings between the different phenotypic variants of PSP (Potrusil et al, 2020; Whitwell et al, 2021). The corpus callosum (CC) has not been an anatomical area of specific interest in this context yet and has been addressed only in limited numbers of patients by computerized MRI sensitive to microstructural changes (Rosskopf et al, 2014) and by surface-based analysis (Lenka et al, 2017), routine structural MRI in PSP might demonstrate callosal atrophy at individual level, especially in its frontal areas. A recent innovative whole brain-based study applying fixel-based analysis to diffusion weighted imaging in patients with neurodegenerative parkinsonism (including PSP and PD) demonstrated specific patterns of white matter degeneration which included, in PSP, the body of the CC together with the superior corona radiata, internal capsules, and the midbrain (Nguyen et al, 2021). The regional distribution of the widespread cerebral morphological alterations in progressive supranuclear palsy (PSP) is considered to include segmental parts of the corpus callosum (CC)

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