Simple vision tests can predict which people with Parkinson’s disease will develop cognitive impairment and possible dementia 18 months later
Brain areas with reductions in white matter over 18 months in people with Parkinson's disease (from Movement Disorders paper)
Simple vision tests can predict which people with Parkinson’s disease will develop cognitive impairment and possible dementia 18 months later, according to a new study by UCL researchers. The study, published in Movement Disorders, adds to evidence that vision changes precede the cognitive decline that occurs in many, but not all, people with Parkinson’s. In another new study published in Communications Biology, the same research team found that structural and functional connections of brain regions become decoupled throughout the entire brain in people with Parkinson’s disease, particularly among people with vision problems. The two studies together show how losses and changes to the brain’s wiring underlie the cognitive impairment experienced by many people with Parkinson’s disease.
Lead author Dr Angeliki Zarkali (Dementia Research Centre, UCL Queen Square Institute of Neurology) said: “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. Dementia is a common, debilitating aspect of Parkinson’s disease, estimated to affect roughly 50% of people within 10 years of a Parkinson’s diagnosis.
The researchers identified white matter damage to some of the long-distance wiring connecting the front and back of the brain, which helps the brain to function as a cohesive whole network.
The Communications Biology study involved 88 people with Parkinson’s disease (33 of whom had visual dysfunction and were thus judged to have a high risk of dementia) and 30 healthy adults as a control group, whose brains were imaged using MRI scans.
The researchers found that people with Parkinson’s disease exhibited a higher degree of decoupling across the whole brain. Areas at the back of the brain, and less specialised areas, had the most decoupling in Parkinson’s patients. Parkinson’s patients with visual dysfunction had more decoupling in some, but not all brain regions, particularly in memory-related regions in the temporal lobe.
The research team also found changes to the levels of some neurotransmitters (chemical messengers) in people at risk of cognitive decline, suggesting that receptors for those transmitters may be potential targets for new drug treatments for Parkinson’s dementia. Notably, while dopamine is known to be implicated in Parkinson’s, the researchers found that other neurotransmitters – acetylcholine, serotonin and noradrenaline – were particularly affected in people at risk of cognitive decline.
(Source: UCL news release)