Vision changes could predict cognitive decline in Parkinson's patients
A pair of newly published studies from scientists at University College London are offering novel insights into how the neurodegeneration associated with Parkinson’s disease (PD) leads to cognitive decline. The research suggests minor vision problems can precede cognitive decline by up to 18 months.
Around 50 percent of Parkinson’s disease patients will develop dementia within 10 years of their initial diagnosis. But doctors currently have no way to predict which Parkinson’s patients will present with cognitive decline and at least a third of sufferers won’t develop dementia at any point in their disease progression.
The first new study from the UCL team investigated a previously observed association between vision problems and subsequent cognitive decline in Parkinson’s patients. The study followed 77 patients for 18 months, confirming visual dysfunction does seem to precede imminent cognitive decline, suggesting vision tests may be an effective way to diagnose Parkinson’s patients most as risk of developing dementia.
“We have found that people with Parkinson’s disease who have visual problems are more likely to get dementia, and that appears to be explained by underlying changes to their brain wiring,” explains lead author Angeliki Zarkali. “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.”
The second study employed resting-state functional MRI (rsfMRI) and diffusion-weighted imaging to closely look at how structural and functional connectivity deteriorates in the brains of Parkinson’s patients, and how that associates with visual dysfunction and dementia.
“Our findings show 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),” the researchers conclude in the second study. “We show that structural–functional connectivity decoupling in PD follows the same macroscopic organizational principles that guide SC–FC [structural–functional] coupling in healthy individuals but with accelerated decoupling.”
All of this essentially presents researchers with novel insights into how Parkinson’s disease progresses, particularly in those patients developing dementia. The affirmed association between vision problems and cognitive decline can initially help focus enrollments in clinical trials, allowing for new and more targeted drugs to be tested.
“The two papers together help us to understand what’s going on in the brains of people with Parkinson’s who experience cognitive decline, as it appears to be driven by a breakdown in the wiring that connects different brain regions,” says Zarkali.