Mild cognitive impairment in patients with Parkinson's disease: An updated mini-review and future outlook

Abstract

Mild cognitive impairment (MCI) is one of the common non-motor symptoms in patients with Parkinson's disease (PD). MCI is the transition stage between normal aging and full-blown dementia and is also a powerful predictor of dementia. Although the concept of MCI has been used to describe some of the PD symptoms for many years, there is a lack of consistent diagnostic criteria. Moreover, because of the diverse patterns of the cognitive functions, each cognitive impairment will have a different progression. In this review, we overviewed the diagnostic criteria for PD-MCI, primarily focused on the heterogeneity of PD-MCI patients' cognitive function, including various types of cognitive functions and their progression rates. A review of this topic is expected to be beneficial for clinical diagnosis, early intervention, and treatment. In addition, we also discussed the unmet needs and future vision in this field.

Keywords: Parkinson’s disease; cognitive function; dementia; heterogeneity; mild cognitive impairment.

FIGURE 1

Yearly articles related to cognitive training for Parkinson’s disease on PubMed.

FIGURE 2

The possible patterns and evolution of cognitive function in patients with Parkinson’s disease. Before full-blown dementia, the PD patients’ cognitive patterns may be in the “PDNC,” “pre PD-MCI,” or “PD-MCI.” The pathway from PD-MCI to PDD is relatively stable; however, the three cognitive states may transition before entering into PDD. PDNC, PD patients with normal cognition; pre PD-MCI, PD patients do not achieve PD-MCI diagnosis but have cognitive impairment; PD-MCI, PD patients achieve PD-MCI diagnosis; PDD, PD patients with dementia.