Enhanced cued recall and clock drawing test performances differ in Parkinson's and Alzheimer's disease-related cognitive dysfunction

Cognitive impairment either as dementia (PD–D) or mild cognitive impairment (PD–MCI) is common in Parkinson's disease (PD). The clinical features and cognitive profile differs from Alzheimer's disease (AD) or amnestic MCI (aMCI). In this study we aim to disclose the utility of pre-selected practical neuropsychological tests in differentiation of PD–D and AD, and also PD–MCI and aMCI. Consecutive cases with mild to moderate AD (n = 32) and PD–D (n = 26); aMCI (n = 34) and PD–MCI (n = 19) were evaluated. Although MMSE scores were similar in PD–D and AD or in PD–MCI and aMCI groups, memory impairment assessed by enhanced cued recall (ECR) was more apparent in AD than PD–D; and ECR scores tended to be worse in aMCI group than PD–MCI group. In contrast, clock drawing was more impaired in PD–D than AD. For differentiation of PD–D from AD, ECR, clock drawing and letter fluency were found to be valuable with moderately high sensitivity and specificities. In differentiation of aMCI and PD–MCI, ECR, clock drawing test and copying of intersecting pentagons were helpful. Stepwise linear discrimination function analysis disclosed that combination of ECR and clock drawing tests correctly classified 70.7% of the overall study population (71.4% of AD, 71.9% of aMCI, 69.6% of PD–D and 68.8% of PD–MCI). These findings suggest that ECR and clock drawing tests can be valuable as an additive to clinical diagnostic criteria in differentiation of PD–D and PD–MCI cases from AD and aMCI.