Amnestic mild cognitive impairment in Parkinson's disease: White matter structural changes and mechanisms

Area of Science:

• Neuroscience
• Neurology
• Radiology

Background:

• Mild cognitive impairment (MCI) is common in Parkinson's disease (PD), with the amnestic subtype (PD-aMCI) posing a higher dementia risk.
• White matter (WM) structural changes in PD-aMCI are understudied.
• Understanding WM alterations is crucial for differentiating PD subtypes and predicting dementia progression.

Purpose of the Study:

• To investigate and characterize white matter (WM) structural differences in patients with amnestic mild cognitive impairment due to Parkinson's disease (PD-aMCI).
• To differentiate WM changes related to cognitive impairment from those associated with motor deficits in PD.
• To explore the relationship between WM integrity and memory function in PD patients.

Main Methods:

• Utilized voxel-based and tract-based spatial statistics (TBSS) on diffusion tensor imaging (DTI) metrics (FA, AD, RD).
• Compared PD-aMCI (n=17) with cognitively normal PD (PD-CN, n=19) and healthy controls (n=20).
• Analyzed WM changes with and without motor performance as a covariate, and correlated WM measures with memory performance.

Main Results:

• PD-aMCI patients exhibited reduced fractional anisotropy (FA) in diffuse WM areas compared to PD-CN.
• PD-CN showed increased axial diffusivity (AD) and radial diffusivity (RD) in the right caudate compared to controls.
• Motor adjustment attenuated most FA differences between PD-aMCI and PD-CN, which largely overlapped with memory-correlated FA values.

Conclusions:

• White matter structural differences in PD-aMCI are primarily linked to memory impairment.
• The influence of motor adjustment suggests a shared neuropathological mechanism, potentially dopaminergic, underlying both motor and cognitive deficits in PD-aMCI.
• Findings highlight the importance of considering cognitive-specific WM changes in PD progression and management.