Parkinson's disease (PD) is a complex neurodegenerative disorder characterized by both motor and non-motor symptoms, primarily attributed to dopaminergic dysfunction in the substantia nigra pars compacta. However, growing evidence indicates that serotonergic and noradrenergic alterations also contribute significantly to PD pathophysiology and progression. This growing understanding has driven the development of advanced neuroimaging techniques aimed at visualizing not only dopaminergic deficits but also serotonergic and noradrenergic alterations, providing deeper insights into PD pathophysiology and progression. Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) have been instrumental in visualizing dopaminergic deficits, particularly dopamine transporter loss, aiding in diagnosis and disease progression tracking. While PET and SPECT remain crucial in assessing dopaminergic dysfunction, novel MRI techniques, including neuromelanin-sensitive MRI, iron-sensitive MRI, diffusion-weighted imaging, and pharmacological MRI, have emerged as promising non-invasive alternatives for evaluating monoaminergic dysfunction in PD. In this narrative review, we have discussed the recent neuroimaging advancements in assessing monoaminergic dysfunction in PD, highlighting how these advances not only improve our understanding of the distinct contributions of dopaminergic, noradrenergic, and serotonergic systems to motor and non-motor symptoms, but also offer promising biomarkers for disease progression and treatment response. • MRI enables in vivo assessment of dopaminergic, noradrenergic, and serotonergic nuclei. • Neuromelanin-MRI and QSM provide complementary markers of nigral degeneration in PD. • LC and raphe MRI reveal early non-dopaminergic involvement linked to non-motor symptoms. • Diffusion and free-water imaging track microstructural progression across PD stages. • Multimodal MRI refines PD diagnosis, subtype stratification, and treatment monitoring.
Samanci et al. (Thu,) studied this question.