Amygdala subregion MRI alterations in Parkinson's disease correlate with olfactory function

Area of Science:

• Neuroimaging
• Neuroanatomy
• Neurology

Background:

• Olfactory dysfunction is a common early symptom in Parkinson's disease (PD), affecting 80-90% of patients.
• The amygdala, crucial for olfactory processing, has distinct subregions whose volumetric changes in PD are not fully understood.

Purpose of the Study:

• To investigate volumetric changes in nine amygdala subregions across different stages of Parkinson's disease.
• To explore the relationship between these amygdala subregion volumes and olfactory function in PD patients.

Main Methods:

• A cross-sectional study involving 65 PD patients (early and late stages) and 45 healthy controls.
• High-resolution 3D-T1WI MRI with automated segmentation to quantify amygdala subregion volumes.
• Olfactory function assessed using Sniffin' Sticks; cognitive function by MMSE; statistical analyses included ANCOVA/GLM and Spearman partial correlation.

Main Results:

• Parkinson's disease patients showed significant bilateral volume reductions in the cortical nucleus (Co), accessory basal nucleus (AB), cortico-amygdaloid transition area (CAT), and right anterior amygdaloid area (AAA) compared to controls.
• Bilateral Co and right AAA volumes were reduced even in early-stage PD.
• While right AAA volume showed a weak correlation with olfactory scores, left medial subdivision (Me) volume positively correlated with MMSE scores.

Conclusions:

• Parkinson's disease is characterized by subregion-selective amygdala atrophy, with early involvement of Co and AAA, and a right-lateralized pattern.
• The right AAA's volume may play a specific role in PD-related olfactory dysfunction.
• Left Me volume correlates with cognitive function, suggesting its potential as a structural biomarker.