Subcortical white matter hyperintensities within the cholinergic pathways of Parkinson's disease patients according to cognitive status

Background: White matter hyperintensities (WMH) in the cholinergic pathways show a stronger correlation with cognitive performance than general WMH in Alzheimer's disease. However, the role of WMH within the cholinergic pathways in cognitive dysfunction has not been investigated in Parkinson's disease (PD). Method: The severity of WMH within the cholinergic pathways of PD subgroups with intact cognition (PD-IC, n=44), mild cognitive impairment (PD-MCI, n=87) and dementia (PDD, n=40) were compared using the Cholinergic Pathways Hyperintensities Scale (CHIPS), and the correlation between the CHIPS score and performance on individual tests of cognitive subdomains were analysed. Results The mean CHIPS score was significantly higher in patients with PDD compared with those with PD-IC (p=0.03) or PD-MCI (p=0.015). The CHIPS score in patients with PD was negatively correlated with general cognition assessed using the Mini-Mental State Examination (r=-0.28, p<0.001) and positively with the Unified Parkinson's Disease Rating Scale motor score (r=0.24, p=0.002). The CHIPS score showed a significant correlation with cognitive performance on individual cognitive subdomains and had the highest independent correlations with contrasting programme (β=-0.33, p<0.001) and forward digit span (β=-0.17, p=0.04). Conclusions: This study demonstrated that the burden of WMH within cholinergic pathways was significantly higher in patients with PDD relative to other groups, and that cholinergic WMH was significantly correlated with a decline in frontal executive function and attention.