¹⁸F-Florzolotau Tau Positron Emission Tomography Imaging in Patients with Multiple System Atrophy–Parkinsonian Subtype

Background: Anecdotal evidence suggests that patients diagnosed with the parkinsonian subtype of multiple system atrophy (MSA-P) may show uptake of the second-generation tau positron emission tomography (PET) tracer ¹⁸F-Florzolotau (previously known as ¹⁸F-APN-1607) in the putamen. Objectives: This study systematically investigated the localization and magnitude of ¹⁸F-Florzolotau uptake in a relatively large cohort of patients with MSA-P. Methods: ¹⁸F-Florzolotau PET imaging was performed in 31 patients with MSA-P, 24 patients with Parkinson's disease (PD), and 20 age-matched healthy controls. ¹⁸F-Florzolotau signal in the striatum was analyzed by visual inspection and classified as either positive or negative. Regional ¹⁸F-Florzolotau binding was also expressed as standardized uptake value ratio (SUVR) to assess whether it was associated with core symptoms of MSA-P after adjustment for potential confounders. Results: By visual inspection and semiquantitative SUVR comparisons, patients with MSA-P showed elevated ¹⁸F-Florzolotau uptake in the putamen, globus pallidus, and dentate—a finding that was not observed in PD. This increased signal was significantly associated with the core symptoms of MSA-P. In addition, patients with MSA-P with cerebellar ataxia showed an elevated ¹⁸F-Florzolotau uptake in the cerebellar dentate. Conclusions: ¹⁸F-Florzolotau tau PET imaging findings may reflect the clinical severity of MSA-P and can potentially discriminate between this condition and PD.