It may now be possible to identify the first-stage Parkinson’s patients who will go on to develop dementia, according to a study conducted at the Institut universitaire de geriatrie de Montreal by Dr. Oury Monchi, PhD, and his postdoctoral student, Dr. Alexandru Hanganu, MD, PhD, both of whom are affiliated with Universite de Montreal. These findings were published in the journal Brain.
Although Parkinson’s disease is generally associated with motor problems such as trembling or rigidity, people with this disease actually have a six times greater risk of developing dementia compared to the rest of the population. In this first longitudinal study in this field, 32 patients in the first stages of Parkinson’s disease were followed for 20 months. Some of the patients had mild cognitive impairments while others did not. A control group of 18 healthy people were also followed.
“Using magnetic resonance imaging, we found thinning in certain cortical areas as well as subcortical atrophy in the grey matter of subjects with mild cognitive impairments. Thanks to our longitudinal approach, we were able to observe that this thinning speeds up in conjunction with the increase in cognitive problems,” explained Dr. Monchi. This specific brain deterioration combined with the early presence of mild cognitive impairments could serve as markers for the development of dementia.
Dr. Monchi stressed the importance of these findings: “This study opens the door to further research, for example, on medication or on non-pharmacological approaches such as transcranial magnetic stimulation. It’s important for these patients to be identified very quickly before they develop dementia so that a therapeutic approach can be adapted to their specific needs.”
An estimated 100,000 Canadians have Parkinson’s. It is the second most common neurodegenerative disease after Alzheimer’s.
Previous studies have shown greater atrophy in grey and white matter of various brain regions in Parkinson’s disease patients with mild cognitive impairment than in those without. These anatomical differences likely account for the distinct clinical profiles observed between those groups, but do not account for the evolution of regional brain degradation observed as the disease evolves. While we have shown recently that cortical thinning correlates significantly more with disease duration in Parkinson’s patients with mild cognitive impairment than those without, to the best of our knowledge no study to date has explored this longitudinally. The present study investigated the longitudinal changes of the cortical and subcortical grey matter in patients with Parkinson’s disease with and without mild cognitive impairment. Additionally, these two groups were compared with healthy controls. We found a higher rate of cortical thinning in the temporal, occipital, parietal and supplementary motor area, in Parkinson’s patients with mild cognitive impairment compared with both cognitively stable patients and healthy controls. On the other hand Parkinson’s patients without mild cognitive impairment had only one lateral occipital and one fusiform cluster with increased rate of thinning compared to healthy individuals. Correlating the rate of change of cortical thickness with the results of Montreal Cognitive Assessment scores, revealed significant thinning associated with cognitive decline in all patients, in similar regions including temporal and medial occipital lobe. Finally, a significant decrease in the volume of the amygdala and nucleus accumbens was observed specifically in Parkinson’s patients with mild cognitive impairment. These results indicate that the early presence of mild cognitive impairment in patients with Parkinson’s disease is associated with a faster rate of cortical grey matter thinning in various regions as well as a significant diminishment of limbic subcortical structures. This specific pattern of brain degradation associated with the early presence of mild cognitive impairment might serve as a marker of development toward dementia.
Mild cognitive impairment is linked with faster rate of cortical thinning in patients with Parkinson’s disease longitudinally, Brain (2014) doi: 10.1093/brain/awu036