According to a study published in the December issue of Archives of Neurology, one of the JAMA/Archives journals, individuals who suffer with Parkinson disease-related dementia seem to have increased brain atrophy in the parietal, hippocampal, temporal lobes, as well as decreased prefrontal cortex volume than individuals with Parkinson disease without dementia.
The researchers explain:
"Patients with Parkinson disease (PD) are at an increased risk of developing dementia (PDD), with cumulative prevalence rates of up to 80 percent.
Approximately 25 percent of non-demented PD patients meet neuropsychological criteria for mild cognitive impairment (PD-MCI), which converts to PDD in many cases, and even mild cognitive deficits in PD are associated with functional impairments and worse quality of life."
Daniel Weintraub, M.D., of the Perelman School of Medicine, University of Pennsylvania, Philadelphia, and colleagues, set out to evaluate the areas and patterns of brain atrophy in individuals with Parkinson disease with normal cognition (PD-NC), individuals with Parkinson disease with dementia-level cognitive deficits (PDD), as well as individuals with PD with mild cognitive impairment (PD-MCI).
The researchers enrolled 84 individual with Parkinson disease (61 PD-NC, 11 PDD, and 12 PD-MCI) and 23 healthy control individuals to participate in the study. All participants in the study underwent magnetic resonance imaging (MRI) of the brain. The team gathered data as part of the University of Pennsylvania Center of Excellence for Research on Neurodegenerative Diseases.
After the researchers adjusted for other factors, such as education level, sex, and age of the participant, they discovered no between-group differences in regional brain volumes for PD-NC participants compared with control group patients. The team found that among participants with Parkinson disease, there were cognitive group-level differences in medial temporal lobe and hippocampal volumes.
The hippocampal volumes among PD-MCI and PDD participants were smaller than PD-NC participants, although the team found no differences between participants in the PDD and PD-MCI groups. In addition, participants in the PDD group had medial temporal lobe atrophy compared with participants in the PD-NC group, but not those in the PD-MCI group. The researchers observed no between-group differences for other regions in the brain.
Patients in the PD-MCI group had a different pattern of brain atrophy than participants in the PD-NC group, although similar to that of PDD participants. The researchers characterized this pattern by atrophy in prefrontal cortex gray and white matter, hippocampal volume, parietal lobe white matter, and occipital lobe gray and white matter.
In Parkinson's disease patients without dementia, the team discovered an association between memory-encoding performance and hippocampal volume, "suggesting heterogeneity in the neural substrate of memory impairment."
The researchers conclude:
"With growing recognition of Parkinson disease with mild cognitive impairment as common and clinically significant, it will be important to develop consensus diagnostic criteria, validate assessment instruments for use in clinical care and research, and test treatments for their symptomatic and disease-modifying effects. Use of a pattern classification approach may allow identification of diffuse regions of cortical gray and white matter atrophy early in the course of cognitive decline."
Written by Grace Rattue