Objective: Our aim is to describe the findings of 18F-PI-2620 tau-PET imaging, together with tau protein burden and 18F-PI-2620 tau autoradiography in brain tissue from the same PSP patient.

Background: The next generation tau-positron-emission-tomography (PET) tracer 18F-PI-2620 has shown to be useful for the in vivo detection of tau pathology. However, final pathological prove has not been obtained.

Method: Both 18F-FDG-PET and 18F-PI-2620-PET imaging were performed on a 70 years old woman with a clinical diagnosis of probable PSP Richardson syndrome subtype. We applied a multivariate Scaled Subprofile Model/Principal Component Analysis (SSM/PCA) to the FDG-PET scan to obtain the individual score of previously identified PSP-related pattern (PSPRP)(1). Moreover, an ROI analysis was performed on the 18F-PI-2610 PET scan to obtain the SUVR from preselected brain regions. The patient died five years after disease onset, and one month after the PET imaging procedures. A postmortem brain study confirmed the diagnosis of PSP. The distribution of tau protein by AT8 immunohistochemistry was assessed semiquantitatively in 12 brain regions. Furthermore, the same brain samples were examined by autoradiography using 18F-PI-2620.

Results:

By in vivo PET imaging, the FDG-PET PSPRP Z-score was 6.85 (cut-off for distinguishing PSP from PD or HC = 1.59) and the 18F-PI-2620 SUVR was high at globus pallidus (1.33), subthalamic nucleus (1.22), substantia nigra (1.2) and dentate nucleus (1.1). Tau AT8 immunohistochemistry showed a high burden in the pallidum and subthalamic nucleus, moderate deposits in the substantia nigra, putamen, pons and cerebellum and prefrontal cortex. The highest 18F-PI-2620 autoradiography signal in human tissue was found in the pallidum, putamen, subthalamic nucleus and frontal cortex as well. Correlation between neuronal AT8 burden and autoradiographic binding was found, almost reaching statistical significance (p=0.055).

Conclusion: This clinical report describes for the first time, in the same PSP patient 18F-PI-2620 PET imaging findings, density and distribution of brain tau protein identified by immunohistochemical techniques, and the binding of 18F-PI-2620 in human tissue by autoradiography, adding evidence to the value of 18F-PI-2620-PET to facilitate a more reliable diagnosis of PSP. More detailed analyses are ongoing, and the final analysis will be presented.

References: 1. Martí‐Andrés G, Bommel L, Meles SK, Riverol M, Valentí R, Kogan R V., et al. Multicenter Validation of Metabolic Abnormalities Related to PSP According to the MDS‐PSP Criteria. Mov Disord [Internet]. 2020 Nov 21;35(11):2009–18. Available from: https://onlinelibrary.wiley.com/doi/abs/10.1002/mds.28217

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MDS Abstracts - https://www.mdsabstracts.org/abstract/18f-pi-2620-tau-pet-neuroimaging-tau-protein-burden-and-18f-pi-2620-tau-autoradiography-on-human-postmortem-brain-tissue-in-a-psp-patient/