Microstructural network alterations of olfactory dysfunction in newly diagnosed Parkinson's disease

Area of Science:

• Neuroscience
• Neurology
• Medical Imaging

Background:

• Olfactory dysfunction is an early indicator of Parkinson's disease (PD), often preceding motor symptoms.
• Previous research suggests links between olfactory dysfunction, dementia, and neural changes in PD.
• The impact of olfactory dysfunction on white matter (WM) microstructure in early, untreated PD is not well understood.

Purpose of the Study:

• To investigate the effects of olfactory dysfunction on white matter microstructure in newly diagnosed, untreated Parkinson's disease patients.
• To compare WM features between PD patients with and without hyposmia, and healthy controls.
• To explore potential network-level biomarkers for olfactory dysfunction in early PD.

Main Methods:

• Diffusion Tensor Imaging (DTI) and Tract-Based Spatial Statistics (TBSS) were used to analyze WM microstructure.
• Graph-theoretic methods and Network-Based Statistics (NBS) were employed for network analysis.
• 88 newly diagnosed PD patients (70 with hyposmia, 18 without) and 33 healthy controls were included.

Main Results:

• TBSS revealed no significant differences in regional WM integrity (fractional anisotropy, mean diffusivity) between groups.
• PD patients without hyposmia showed reduced global network efficiency compared to controls.
• PD patients with hyposmia exhibited reduced global and local network efficiency, disrupted olfactory circuitry connectivity, and poorer frontal cognitive function.

Conclusions:

• White matter changes associated with hyposmia in early Parkinson's disease manifest at the network level, not regionally.
• Disrupted connectivity within the olfactory circuitry may serve as a specific biomarker for olfactory dysfunction in early PD.
• These findings highlight the importance of network analysis in understanding the neurobiological underpinnings of early PD and its associated symptoms.