¹⁸F-FP-DTBZ PET/CT detectable associations between monoaminergic depletion in the putamen with rigidity and the pallidus with tremor in Parkinson's disease

Introduction: The motor subtypes of Parkinson's disease (PD) are widely accepted and implemented. However, the motor subtypes have been thought to represent different stages of PD recently because some patients experience tremor-dominant (TD) conversion to the non-tremor-dominant subtype, such as postural instability-gait difficulty (PIGD). In this study, we explore the monoaminergic denervation features of the striatal and extra-striatal areas in patients with different subtypes of PD with ¹⁸F-9-fluoropropyl-(+)-dihydrotetrabenazine (¹⁸F-FP-DTBZ) PET/CT.

Methods: Sixty-five patients diagnosed with PD were included and classified as TD (n = 25) and PIGD (n = 40). We evaluated the difference of monoaminergic features of each subregion of brain between motor subtypes of PD, as well as associations between these features and Parkinsonian motor symptoms.

Results: The striatal standardized uptake value ratios (SUVR) showed that dopaminergic disruption of patients with PIGD was more symmetrical in the posterior ventral putamen (p < 0.001) and more severe in the ipsilateral posterior dorsal putamen (p < 0.001 corrected) compared with that of patients with TD. The severity of PIGD scores was associated with striatal dopaminergic depletion, while tremor was associated with monoaminergic changes in extra-striatal areas, including pallidus, thalamus, and raphe nuclie.

Conclusion: These results indicate that patients with different motor subtypes may have different underlying mechanisms of PD pathogenesis. Therefore, accurate diagnosis of PD subtypes can aid prognosis evaluation and treatment decision-making.