Objective: In our previous study FP-CIT SPECT (FP-CIT) in progressive supranuclear palsy-Parkinsonism (PSP-P) revealed higher anterior striatal accumulation, and PSP- Richardson’s syndrome (PSP-RS) revealed lower accumulation in all parts of striatum in comparison to PD. The subtypes were determined by neurologist agreement. In this study, we aimed to increase the number of cases and assess striatal FP-CIT findings of subtypes of PSP according to MDS-PSP criteria.

Background: An expected clinical course vary according to PSP subtype. Phosphorylated tau protein distribution defines the pathological heterogeneity of PSP subtypes. We hypothesized that striatal FP-CIT findings would differ according to the PSP subtype based on differing tau protein distributions.

Methods: From our hospital, 26 consecutive patients with PSP who performed FP-CIT were recruited and subdivided into groups according to MDS-PSP criteria. Patients with ataxia were redistributed to a PSP-cerebellar (PSP-C) subtype, which is not mentioned in MDS-PSP criteria. We compared the findings to 15 patients with PD and 15 normal controls.

Results: The classification of patients was as follows: 10 with PSP-P, 7 with PSP-RS (including 4 with PSP-C), 1 with PSP with postural instability (also classified into the PSP-C group), and 4 with another condition; 4 patients were unclassified. In a semi-quantification analysis of FP-CIT accumulation in the caudate nucleus, the PSP-RS group showed the lowest level, while the PSP-P group showed the same level as PD, and PSP-C group shared the intermediate level of PSP-RS and PSP-P. The accumulation in the anterior and posterior putamen was the same in the three representative subtypes as it was in the PD group. Williams et al. reported that tau pathology in patients with PSP-P is less severe and has a more restricted distribution compared with that of PSP-RS patients. The accumulation of tau protein in the putamen is the same in PSP-P as that in PSP-RS. Yet, the accumulation of tau protein in the caudate nucleus is more severe in PSP-RS, which may explain why the PSP-RS group showed the lowest FP-CIT accumulation in the caudate nucleus. The PSP-P group showed the same pattern of striatal FP-CIT accumulation as that of PD. This might explain why the clinical features of PSP-P somewhat resemble those of PD.

Conclusions: The PSP-RS group showed the lowest level of FP-CIT accumulation in the caudate nucleus compared with other subtypes, which may differentiate PSP-RS from other subtypes.

References: Williams D.R. et al. Pathological tau burden and distribution distinguishes progressive supranuclear palsy-parkinsonism from Richardson’s syndrome. Brain 2007;130: 1566-1576.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/striatal-fp-cit-spect-findings-for-progressive-supranuclear-palsy-subtypes/