Objective:

To evaluate whether neuropsychological testing in patients with isolated executive dysfunction at the mild cognitive impairment (MCI) stage can help diagnose Alzheimer’s disease (AD), vascular dementia (VasD), dementia with Lewy bodies (DLB), and frontotemporal dementia (FTD) syndromes.

Background:

Neurodegenerative disorders such as AD, VasD, DLB, and FTD often show overlapping isolated executive dysfunction at the MCI stage. Because clinical symptoms often converge and biomarkers are not always accessible, identifying disease-specific patterns through neuropsychological testing may help with early differential diagnosis. 

Design/Methods:

Data were obtained from the National Alzheimer’s Coordinating Center (NACC) database, including 762 participants (mean age = 71.3 years; 412 female) with single domain executive predominant MCI carrying a primary clinical diagnosis of AD (n = 297), DLB (n = 182), VasD (n = 221), or FTD (n = 62). Inclusion criteria were Clinical Dementia Rating (CDR) = 0.5–1 and Mini-Mental State Examination (MMSE) 17–29 or Montreal Cognitive Assessment (MoCA) 17–26. A cognitively healthy control group (HC, n = 595) had CDR = 0 and MMSE = 30 or MoCA > 26. One-way ANOVA with a p value < 0.05 was used.  

Results:

FTD patients performed worst on Digit Span Backwards, phonemic and semantic fluency, and Benson figure copy compared with AD and HC. DLB patients showed significantly poorer performance than AD and HC on the Trail Making Test B. AD patients exhibited the lowest on Logical Memory IIA test compared with DLB and controls, while visual Benson figure recall did not differ. VasD patients showed the greatest impairment on the Boston naming task. 

Conclusions:

FTD patients showed prominent executive dysfunction affecting fluency and visuospatial function. AD patients showed verbal memory impairment, DLB patients demonstrated reduced executive flexibility, and VasD patients exhibited reduced processing speed. Neuropsychological profiling offers valuable diagnostic utility in differentiating dementia subtypes when biomarker data are unavailable.