Neuropsychological Impairments and Their Cognitive Architecture in Mild Cognitive Impairment (MCI) with Lewy Bodies and MCI-Alzheimer's Disease.

Objective: The present study aimed to clarify the neuropsychological profile of the emergent diagnostic category of Mild Cognitive Impairment with Lewy bodies (MCI-LB) and determine whether domain-specific impairments such as in memory were related to deficits in domain-general cognitive processes (executive function or processing speed).

Method: Patients ( = 83) and healthy age- and sex-matched controls ( = 34) underwent clinical and imaging assessments. Probable MCI-LB ( = 44) and MCI-Alzheimer's disease (AD) ( = 39) were diagnosed following National Institute on Aging-Alzheimer's Association (NIA-AA) and dementia with Lewy bodies (DLB) consortium criteria. Neuropsychological measures included cognitive and psychomotor speed, executive function, working memory, and verbal and visuospatial recall.

Results: MCI-LB scored significantly lower than MCI-AD on processing speed [Trail Making Test B: = .03, = .45; Digit Symbol Substitution Test (DSST): = .04, = .47; DSST Error Check: < .001, = .68] and executive function [Trail Making Test Ratio (A/B): = .04, = .52] tasks. MCI-AD performed worse than MCI-LB on memory tasks, specifically visuospatial (Modified Taylor Complex Figure: = .01, = .46) and verbal (Rey Auditory Verbal Learning Test: = .04, = .42) delayed recall measures. Stepwise discriminant analysis correctly classified the subtype in 65.1% of MCI patients (72.7% specificity, 56.4% sensitivity). Processing speed accounted for more group-associated variance in visuospatial and verbal memory in both MCI subtypes than executive function, while no significant relationships between measures were observed in controls (all s > .05).

Conclusions: MCI-LB was characterized by executive dysfunction and slowed processing speed but did not show the visuospatial dysfunction expected, while MCI-AD displayed an amnestic profile. However, there was considerable neuropsychological profile overlap and processing speed mediated performance in both MCI subtypes.