Mild cognitive impairment in Parkinson's disease: How much testing is needed for correct diagnosis?

Screening for Cognitive Impairment in Movement Disorders: Comparison of the Montreal Cognitive Assessment and Quick Mild Cognitive Impairment Screen in Parkinson's Disease and Lewy Body Dementia

Background

The Montreal Cognitive Assessment (MoCA) is recommended by the Movement Disorder Society for cognitive testing in movement disorders including Parkinson's disease (PD) and lewy body dementia. Few studies have compared cognitive screening instruments in these diseases, which overlap clinically.

Objective

To compare the MoCA and Quick Mild Cognitive Impairment (Qmci) screen in this population.

Methods

Patients attending memory and movement disorder clinics associated with a university hospital had the MoCA and Qmci screen performed and diagnostic accuracy compared with the area under the receiver operating characteristic curve (AUC). Duration and severity of movement disorders was assessed using the Unified PD Rating Scale (UPDRS).

Results

In total, 133 assessments were available, median age 74±5. Median education was 11±4 years and 65% were male. Median total UPDRS score was 37±26. Median Qmci screen was 51±27, median MoCA was 19±10. There were statistically significant differences in test scores between those with subjective symptoms but normal cognition, mild cognitive impairment (MCI) and dementia (p < 0.001). The Qmci screen had significantly greater accuracy differentiating normal cognition from MCI versus the MoCA (AUC 0.90 versus 0.72, p = 0.01). Both instruments had similar accuracy in identifying cognitive impairment and separating MCI from dementia. The median administration time for the Qmci screen and MoCA were 5.19 and 9.24 minutes (p < 0.001), respectively.

Conclusions

Both the MoCA and Qmci screen have good to excellent accuracy in a population with movement disorders experiencing cognitive symptoms. The Qmci screen was significantly more accurate for those with early symptoms and had a shorter administration time.

Subjective cognitive complaints in patients with Parkinson's disease

Mild cognitive impairment (MCI) is common in Parkinson's disease (PD), affecting almost all patients with PD at some time. It has been shown that patients with PD, who express subjective cognitive complaints, are at a higher risk of eventually developing PD-MCI. This is corroborated by the Movement Disorders Society's (MDS) diagnostic criteria from 2012 for PD-MCI, from which it follows that a subjective cognitive complaint must be present in addition to objective cognitive impairment for a patient with PD to receive a diagnosis of PD-MCI. Nevertheless, there is currently no standardized measurement available for assessing subjective cognitive complaints. Therefore, this review aims to generate an overview of how subjective cognitive complaints are commonly operationalized in the empirical literature as well as whether they are found to be associated with the level of cognitive impairment. The findings revealed that a broad range of measures has been used to obtain subjective cognitive complaints and that there is little consistency between different studies with regard to how they have obtained these complaints, from whom they had obtained them, how many they have obtained, which types of complaints they have obtained and whether they were associated with cognitive impairment. Given the fact that the presence of subjective cognitive complaints is a requirement for setting a diagnosis, there is a need for more methodological consensus with regard to the measurement hereof.