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A correlation between the neuroanatomical–neuropsychological profiles and the progressive mild cognitive impairment (MCI) in Parkinson’s disease (PD)
For a long time, PD has been primarily considered as a motor disorder, but in the last decades, several studies have highlighted the importance of cognitive symptoms and their impact on the quality of life of the patients and their caregivers.1 ,2 That is why the identification of predictors of evolution to dementia in PD (PDD) must be a key research priority.
Although PD-MCI does not substantially affect daily functioning, its detection is important because it may herald the subsequent development of dementia.3 PD-MCI may offer an approach to the pathophysiology of the earliest stage of cognitive decline in PD. This may result in the development of drugs focused on preventing or postponing the onset of PDD.
Lee et al4 explored the different cognitive and anatomical profile of the patients with PD-MCI that progress to PDD in comparison with those that do not. For this reason, they studied 51 patients with PD-MCI for at least 2 years. The patients were divided into MCI converters and MCI non-converters based on whether they were subsequently diagnosed with PDD or not.
One of their most important findings was that the patients with PD-MCI had a smaller mean normalised substantia innominata (SI) volume in the voxel-based morphometry analysis compared with those in controls. Furthermore, the patients with PD-MCI who developed dementia presented a smaller volume of SI in comparison to those who did not. There might be a relationship between this finding and the use of acetylcholine inhibitors, which is the treatment proposed nowadays for PD-MCI and PDD.5 It is important to remember that the primary concentration of cholinergic neurons that project to the neocortex is situated in the basal nucleus of Meynert, which is located in the SI of the anterior perforated substance.
Regarding the cognitive profile of the PD-MCI converters, it is important to note that the findings are a bit dissimilar with some previous reports. The only exception in the predictors of conversion to PDD is the disturbance of the semantic fluency, which is a fact repeated in most of the literature. It is possible that the cognitive profile of these patients is not a homogeneous entity, and that different pathophysiology mechanisms are responsible for each profile.
In spite of the dissimilar findings throughout the literature, the author's results are valuable when we are trying to construct a profile of the PD-MCI. These efforts are essential in developing new treatment strategies.
Competing interests None.
Provenance and peer review Commissioned; internally peer reviewed.
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