Cognitive and Cholinergic Systems Trajectories in Parkinson Disease

Cognitive decline in Parkinson disease (PD) is a disabling and highly variable non-motor feature. While cholinergic systems degeneration is linked to cognitive impairments in PD, most prior research reported cross-sectional associations. We aimed to fill this gap by investigating whether baseline regional cerebral vesicular acetylcholine transporter ligand [ ¹⁸ F]-fluoroethoxybenzovesamicol ([ ¹⁸ F]-FEOBV) binding predicts longitudinal cognitive changes in mild to moderate, non-demented PD subjects.

Seventy-five non-demented, mild-moderate PD subjects received baseline standardized cognitive evaluations and [ ¹⁸ F]-FEOBV PET imaging with repeat cognitive evaluations 2 years later. Participants were classified into four cognitive classes based on stability or change in cognition: Persistent normal (no MCI at baseline and follow-up), Persistent MCI, MCI conversion, and MCI reversion. Whole-brain voxel comparisons with normal controls, and voxel-based and cluster volume-of-interest correlation analyses with longitudinal cognitive changes were performed.

Whole-brain voxel comparisons of each class with a matched control group revealed unique bi-directional differences in baseline regional [ ¹⁸ F]-FEOBV binding. Increased regional [ ¹⁸ F]-FEOBV binding in predominantly anterior cortical and sub-cortical regions was found in the persistent normal and MCI reversion groups. Whole-brain voxel correlation analysis between baseline [ ¹⁸ F]-FEOBV binding and two-year longitudinal percent changes in cognition identified a specific regional pattern of reduced posterior cortical, limbic and paralimbic [ ¹⁸ F]-FEOBV binding predictive of global cognitive declines and across five cognitive domains at two-year follow-ups.

Cholinergic system changes correlate with varying cognitive trajectories in mild-moderate PD. Upregulation of cholinergic neurotransmission may be an important compensatory process in mild-moderate PD.