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Shrinkage of olfactory amygdala connotes cognitive impairment in patients with Parkinson's disease

Ulaş Ay1,2,3, Zerrin Yıldırım1,2,4, Emel Erdogdu2,5

  • 1Department of Neuroscience, Aziz Sancar Institute of Experimental Medicine, Istanbul University, 34093 Istanbul, Turkey.

Cognitive Neurodynamics
|October 3, 2023
PubMed

Insights

Parkinson's disease (PD) involves the amygdala early. Reduced volumes in specific amygdala subdivisions, like the cortico-amygdaloid transition area (CAT) and superficial cortex-like region (sCLR), are linked to cognitive decline in PD patients.

Area of Science:

  • Neuroimaging
  • Neurology
  • Neuroanatomy

Background:

  • Lewy pathology progression in Parkinson's disease (PD) involves the amygdala early.
  • Volumetric changes in amygdala subdivisions are less understood, though the olfactory amygdala is implicated.
  • Cognitive impairment is a significant continuum in PD.

Purpose of the Study:

  • To investigate volumetric differences in amygdala nuclear and sectoral subdivisions across the PD cognitive impairment spectrum.
  • To compare these volumes between cognitively normal PD patients, those with mild cognitive impairment, dementia, and healthy controls.
  • To explore the relationship between amygdala volumes and olfactory function in PD.

Main Methods:

  • T1-weighted MRI images analyzed using FreeSurfer for amygdala nuclear parcellation (NP).
  • Nine amygdala nuclei volumes were estimated and merged into three sectors for sectoral parcellation (SP).
  • Comparison of volumes among Parkinson's disease (PD-CN, PD-MCI, PD-D) and healthy control (HC) groups, and between hyposmic and normosmic PD patients.

Main Results:

  • Significant differences in total amygdala volume were observed among the four groups.
  • Reduced bilateral cortico-amygdaloid transition area (CAT) and superficial cortex-like region (sCLR) volumes were found in PD with mild cognitive impairment (PD-MCI) and PD with dementia (PD-D) compared to PD with normal cognition (PD-CN) and HC.
  • Left CAT and left sCLR volumes accurately classified cognitively impaired PD (PD-CI) with high accuracy (90.7% NP, 85.2% SP).
  • Left olfactory amygdala volume differentiated cognitive impairment in PD.

Conclusions:

  • Specific amygdala subdivisions, particularly the left CAT and sCLR, show significant volume reductions associated with cognitive impairment in Parkinson's disease.
  • These volumetric changes, especially in the olfactory amygdala, can serve as neuroimaging biomarkers for diagnosing cognitive impairment in PD.
  • Findings highlight the role of amygdala structural changes in the pathophysiology of cognitive decline in PD.
Keywords:
Parkinson’s diseaseamygdalacognitionhyposmiamagnetic resonance imagingolfactory amygdala

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