Objective: To characterize the longitudinal neural correlates of parkinsonian signs among otherwise functionally normal older adults.

Background: Mild parkinsonian signs are often evident during the clinical examination of older adults without known neurological disease or Parkinson’s disease (PD). The prevalence of such signs increases with age, with up to half of community dwelling adults aged 85 years and older demonstrating some parkinsonian symptoms, yet the true meaning of these motor changes in the “healthy” aging populations are not well understood. Disrupted basal ganglia circuits are the hallmark neural correlate of these motor symptoms in PD and correlates with clinical indices of disease severity. However, it is unclear if mild parkinsonian signs are associated with similar hallmarks in a population of typically aging adults.

Method: 627 community-dwelling older adults (baseline ages 55-99 years) who completed the measure of interest (UPDRS), were functionally intact as operationalized by a 0 on the Clinical Dementia Rating (CDR) scale were included in the analysis. T1-weighted MP-RAGE structural scan and task-free functional MRI (tfMRI) scans were acquired. During tf-fMRI acquisition, participants were asked to close their eyes and concentrate on their breath. To determine the relationship between changes in UPDRS and neural changes, we conducted mixed-effects models in which we decomposed UPDRS into within- and between-subject components with age, sex and education as covariates.

Results: Within-person increases in UPDRS scores were significantly associated with reduced synchrony of intra-subcortical network connectivity over time (p=0.029). Between-person effects were not significant (p=0.284). Models examining the relationship between UPDRS and intra-frontoparietal executive network and inter subcortical-executive network connectivity did not show significant within-person or between-person results (p>0.211).

Conclusion: Our findings extend the typical aging literature by indicating that motor symptoms may function along a continuum. Similar to how mild cognitive impairment represents the stage of cognitive decline between normal aging and dementia; mild parkinsonian symptoms could represent the mild end of a disease spectrum that spans from normal aging to a parkinsonian disease.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/motor-symptoms-in-typical-brain-aging/