Structural Volumetric Alterations in Parkinson's Disease With Mild Cognitive Impairment

Area of Science:

• Neuroimaging
• Neurology
• Cognitive Science

Background:

• Parkinson's disease with mild cognitive impairment (PD-MCI) is a precursor to dementia, but its underlying structural brain changes are not fully understood.
• While hippocampal atrophy is known, volumetric alterations in other subcortical areas require further investigation.

Purpose of the Study:

• To conduct the first comprehensive meta-analysis of gray matter volume changes in six subcortical regions in individuals with PD-MCI.
• To identify specific subcortical structural alterations associated with PD-MCI.

Main Methods:

• A systematic literature search was performed across major databases (PubMed, Web of Science, Embase, Cochrane) for MRI volumetric studies comparing PD-MCI and cognitively normal PD (PD-NC).
• Random-effects models were used to pool data, calculating weighted mean differences (WMDs) and confidence intervals.
• Statistical analyses included heterogeneity assessment (I²), publication bias evaluation, sensitivity analyses, and meta-regression.

Main Results:

• PD-MCI demonstrated significant bilateral atrophy in the hippocampus, thalamus, putamen, and amygdala compared to PD-NC.
• A novel finding of right-lateralized globus pallidus atrophy was observed in PD-MCI.
• Bilateral caudate nuclei volumes remained unchanged, and sensitivity analyses confirmed the robustness of the findings.

Conclusions:

• PD-MCI is characterized by a unique subcortical atrophy pattern affecting limbic-striato-thalamic networks.
• Right globus pallidus atrophy emerges as a potential lateralized biomarker for PD-MCI.
• The study advocates for network-based imaging approaches with standardized protocols and longitudinal validation for PD-MCI research.