Molecular neuroimaging of Parkinson's disease: association of motor and non-motor symptoms with synaptic density, dopaminergic and serotonergic systems

C-DASB binding in the insular cortex (p = 0.003), parietal lobe (p = 0.009), caudate (p < 0.001), and putamen (p = 0.002) were observed in PD compared to HC. Some baseline correlations emerged between imaging metrics and symptom scales in PD, though these were limited. Despite progression in motor impairment, autonomic dysfunction, and overall disability in PD, no significant longitudinal changes or group × time interactions were detected for molecular imaging measures. This study confirmed dopaminergic and serotonergic dysfunction in PD. Synaptic density did not differ between groups or change over time, suggesting synaptic loss may be minimal at mild-to-moderate disease stages. These findings highlight how different molecular imaging markers reflect distinct aspects and timescales of PD pathophysiology.