Neuropsychological Characteristics of Dementia with Lewy Bodies and Parkinson’s Disease with Dementia: Differentiation, Early Detection, and Implications for “Mild Cognitive Impairment” and Biomarkers

Abstract

Parkinson's disease with dementia (PDD) and dementia with Lewy bodies (DLB) are neurodegenerative conditions sharing a disorder of alpha-synuclein metabolism. Temporal differences in the emergence of symptoms and clinical features warrant the continued clinical distinction between DLB and PDD. While DLB and PDD groups' neuropsychological profiles often differ from those in Alzheimer's disease (AD), the diagnostic sensitivity, specificity, and predictive values of these profiles remain largely unknown. PDD and DLB neuropsychological profiles share sufficient similarity to resist accurate and reliable differentiation. Although heterogeneous cognitive changes (predominantly in memory and executive function) may manifest earlier and more frequently than previously appreciated in Parkinson's disease (PD), and executive deficits may be harbingers of dementia, the enthusiasm to uncritically extend the concept of mild cognitive impairment (MCI) to PD should be tempered. Instead, future research might strive to identify the precise neuropsychological characteristics of the prodromal stages of PD, PDD, and DLB which, in conjunction with other potential biomarkers, facilitate early and accurate diagnosis, and the definition of neuroprotective, neurorestorative, and symptomatic treatment endpoints.

Validity of the Mattis Dementia Rating Scale to Detect Mild Cognitive Impairment in Parkinson’s Disease and REM Sleep Behavior Disorder

“…In line with these results, the predominant MCI subtype in our cohort of PD was nonamnestic MCI single domain with impaired attention and executive functions. This is consistent with the dysexecutive syndrome characterizing PD patients with cognitive impairment [11]. …”

“…However, the MMSE is not sensitive to dysexecutive syndrome [10], the main cognitive impairment in PD [11]. Accordingly, its validity to detect cognitive impairment in PD has been questioned [7,12,13,14,15,16].…”

Mild cognitive impairment in Parkinson disease

“…As has previously been pointed out, 20,21 part of the memory impairment in PD may be secondary to impaired attention and executive dysfunction, although recent studies suggest that memory encoding may also be impaired in PD. 22,23 Our analyses also confirmed memory was still impaired in PD even after adjusting for the effect of impaired attention/executive functioning.…”

Nonmotor Symptoms in Parkinson's Disease

“…The Movement Disorder Society has recently reviewed the criteria for cognitive assessment in PD [10]. [11]. Lewy [12].…”