Study: MRI Alzheimers test provides insight into Parkinsons decline
Researchers from the Perelman School of Medicine at the University of Pennsylvania in Philadelphia also found that higher baseline Alzheimer's patterns of atrophy predicted long-term cognitive decline in cognitively normal Parkinson's patients.
"On the basis of a simple neuroimaging study, we can now predict which patients with Parkinson's disease will experience long-term cognitive decline or develop dementia in the future," said the study's lead author, Daniel Weintraub, MD, associate professor of geriatric psychiatry with Penn's Perelman School of Medicine and the Philadelphia Veterans Affairs Medical Center. "Diagnostic tests like this can help us determine which patients would benefit from future clinical trials of medications aiming to stave off or prevent dementia progression in Parkinson's disease."
This research raises the possibility that both Alzheimer's disease and Parkinson's disease pathology contribute to cognitive decline in Parkinson's disease. Researchers are still uncertain whether the neurodegeneration seen in these patients is caused by primary Parkinson's disease pathology, Alzheimer's pathology, a combination of the two, or is a form of compensation.
As biomarkers for Alzheimer's and Parkinson's disease continue to emerge, the researchers suggested at least an overlap in regions undergoing neurodegeneration with cognitive decline, and point to the Spatial Pattern of Abnormalities for Recognition of Alzheimer's disease (SPARE-AD) classification system to detect brain atrophy in Parkinson's disease and identify patients at imminent risk of cognitive decline before clinically identifiable symptoms emerge.
Around 80 percent of Parkinson's patients become demented over the course of the illness. Some patients experience cognitive impairment relatively soon after the disease strikes, while others won't experience dementia until the very end of their disease and nearly 20 percent of patients never have dementia. Over half of Parkinson's patients with dementia have significant signs of Alzheimer's disease-related plaques and neurofribrillary tangles on autopsy, and similar brain regions, such as the hippocampus and medial temporal lobe, have been reported to be affected in both diseases.
The Penn research team applied a pattern classification individual-based score, the SPARE-AD score, to a cross-sectional cohort of 84 Parkinson's patients including patients with dementia, mild cognitive impairment and no dementia. MRI scans were quantified using both a region of interest and voxel-based morphometry analysis, and a method for quantifying the presence of an Alzheimer's disease spatial pattern of brain atrophy was applied to each scan, according to the study abstract.
In the cross-sectional analyses, the SPARE-AD score correlated to cognitive impairment across all groups. From this group, 59 Parkinson's patients without dementia were followed for an additional two years.
“In linear mixed model analyses, higher baseline Alzheimer's disease pattern of atrophy score predicted long-term global cognitive decline in non-demented patients, remarkably even in those with normal cognition at baseline,” wrote the authors in the study abstract.
“These findings support involvement of the hippocampus and parietal–temporal cortex with cognitive impairment and long-term decline in Parkinson's disease,” concluded the authors. “In addition, an Alzheimer's disease pattern of brain atrophy may be a preclinical biomarker of cognitive decline in Parkinson's disease.”