Exploring white matter microstructure and olfaction dysfunction in early parkinson disease: diffusion MRI reveals new...

Area of Science:

• Neuroimaging
• Neuroscience
• Neurology

Background:

• Olfaction dysfunction is a recognized marker of prodromal Parkinson disease (PD).
• Current olfactory screening tests for PD lack specificity and have long lead times.
• Advanced imaging markers are needed for accurate PD prediction and early detection.

Purpose of the Study:

• To investigate white matter microstructural differences in de novo Parkinson disease (PD) patients with varying degrees of olfaction dysfunction using diffusion MRI connectometry.
• To identify correlations between olfactory function (University of Pennsylvania Smell Identification Test - UPSIT score) and specific white matter tract connectivity.
• To explore the potential of diffusion MRI parameters as early diagnostic markers for PD.

Main Methods:

• Diffusion MRI connectometry was performed on 85 de novo PD patients and 36 healthy controls.
• Analysis focused on identifying white matter tracts with significant differences in quantitative anisotropy between PD subgroups and correlating connectivity with UPSIT scores.
• Multiple regression analysis was employed, controlling for age, sex, Geriatric Depression Scale (GDS), and Montreal Cognitive Assessment (MoCA) scores.

Main Results:

• PD patients with anosmia showed decreased connectivity in key white matter tracts including the inferior longitudinal fasciculus, fornix, middle cerebellar peduncle (MCP), cingulum, corticospinal tract (CST), and corpus callosum (CC).
• UPSIT scores significantly correlated negatively with connectivity in the CC and fornix, and positively with connectivity in the cingulum and MCP.
• Olfactory function (UPSIT score) did not predict white matter connectivity in healthy controls.

Conclusions:

• Microstructural changes in specific white matter tracts are associated with the clinical phenotype of olfaction dysfunction in prodromal PD.
• Diffusion MRI parameters in these identified tracts may serve as sensitive and specific signature markers for the early detection of PD.
• This study is the first to demonstrate the discriminative role of the UPSIT score in identifying PD-specific white matter microstructural alterations.