Objective: To elucidate different patterns of progression in midbrain atrophy between patients with Richardson’s syndrome (PSP-RS), progressive supranuclear palsy-parkinsonism (PSP-P), and Parkinson’s disease (PD) using simple MRI-based visual rating indexes.

Background: PSP-P is difficult to diagnose at its early stage. It is often first diagnosed as PD, and later, as PSP-P, after typical clinical symptoms of PSP manifest with the disease progression. Early diagnosis and detection of PSP-P are critical, as it differs from PD in its response to treatment and prognosis. Many studies have been published on quantitative MRI measurements of the brainstem structure as a useful PSP-P marker. However, previous studies were only cross-sectional studies and did not confirm the features of PSP-P with its progression, as shown in the MRI results. Therefore, a study on the change in the marker on the MRI among PD, PSP-P, and PSP-RS would be beneficial in their accurate diagnosis, differentiation, and mechanism description.

Methods: We recruited 12 patients with PSP-RS, 12 with PSP-P, and 23 with PD whose MRIs have been followed up at least 1 year (mean±SD 4.9±1.6 years) after initial one. MRI-based visual rating indexes were used to estimate midbrain atrophy, including a ratio of the pontine to midbrain tegmental areas (P/M ratio) on mid-saggital image, the length between the interpeduncular fossa and the center of the cerebral aqueduct at the mid-mammillary-body level (MTEGM) on axial image, and the morning glory sign.

Results: Initially, there were no differences in MRI-based visual rating indexes between PSP-P and PD, while PSP-RS showed higher P/M ratio and lower MTEGM compared to those from PSP-P and PD. In PD, P/M ratio and MTEGM remained stable with disease progression. However, the amount of changes between initial and follow-up indexes was similarly greater compared to PD in PSP-RS and PS-P. Finally, PSP-P showed higher P/M ratio and lower MTEGM compared to PD on follow-ups, while PSP-RS still exhibited the most profound values.

Conclusions: Midbrain atrophy differentially progresses between PSP-RS, PSP-P, and PD patients. Longitudinal measurements of midbrain atrophy using MRI-based visual rating indexes can help distinguish patients with PSP-P from those with PSP-RS and PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/midbrain-atrophy-differentially-progresses-between-richardsons-syndrome-progressive-supranuclear-palsy-parkinsonism-and-parkinsons-disease-longitudinal-mri-study/