Simple vision tests can predict which people with Parkinson’s disease (PD) will develop cognitive impairment and possible dementia 18 months later, according to a new longitudinal study by UK researchers.
The findings, published in Movement Disorders, add to evidence that vision changes precede the cognitive decline that occurs in some people with PD.
For this study, researchers used fixel‐based analysis to examine longitudinal white matter change in PD. Baseline and 18-month follow-up diffusion magnetic resonance imaging (MRI) and clinical assessments were performed in 77 PD patients (22 low visual function/55 intact vision and 13 PD‐mild cognitive impairment/51 normal cognition) and 25 control participants.
PD patients with visual dysfunction showed worse cognitive performance at follow‐up and were more likely to develop mild cognitive impairment versus those with normal vision (P=.008).
They also showed diffuse microstructural and macrostructural changes at baseline, whereas those with mild cognitive impairment showed fewer baseline changes.
At follow‐up, PD patients with low visual function showed widespread macrostructural changes, involving the fronto‐occipital fasciculi, external capsules and middle cerebellar peduncles bilaterally. No longitudinal change was seen in those with mild cognitive impairment at baseline or converters, even when the two groups were combined.
Another new study by the same researchers, published in Communications Biology, found that structural-functional connectivity coupling is severely disrupted in PD across the cortex, with even more pronounced decoupling in temporal lobe structures in low visual performers (who are at higher risk of dementia).
This study involved 88 people with PD (33 with visual dysfunction and higher risk of dementia) and 30 healthy adults as a control group, whose brains were imaged using MRI scans.
Lead author of both studies Dr Angeliki Zarkali said: “Vision tests might provide us with a window of opportunity to predict Parkinson’s dementia before it begins, which may help us find ways to stop the cognitive decline before it’s too late.”