The Cortical Neuroanatomy Related to Specific Neuropsychological Deficits in Alzheimer's Continuum

BACKGROUND AND PURPOSE: In Alzheimer's continuum (a comprehensive of preclinical Alzheimer's disease [AD], mild cognitive impairment [MCI] due to AD, and AD dementia), cognitive dysfunctions are often related to cortical atrophy in specific brain regions. The purpose of this study was to investigate the association between anatomical pattern of cortical atrophy and specific neuropsychological deficits. METHODS: A total of 249 participants with Alzheimer's continuum (125 AD dementia, 103 MCI due to AD, and 21 preclinical AD) who were confirmed to be positive for amyloid deposits were collected from the memory disorder clinic in the department of neurology at Samsung Medical Center in Korea between September 2013 and March 2018. To analyze neuropsychological test-specific neural correlates representing the relationship between cortical atrophy measured by cortical thickness and performance in specific neuropsychological tests, a linear regression analysis was performed. Two neural correlates acquired by 2 different standardized scores in neuropsychological tests were also compared. RESULTS: Cortical atrophy in several specific brain regions was associated with most neuropsychological deficits, including digit span backward, naming, drawing-copying, verbal and visual recall, semantic fluency, phonemic fluency, and response inhibition. There were a few differences between 2 neural correlates obtained by different z-scores. CONCLUSIONS: The poor performance of most neuropsychological tests is closely related to cortical thinning in specific brain areas in Alzheimer's continuum. Therefore, the brain atrophy pattern in patients with Alzheimer's continuum can be predict by an accurate analysis of neuropsychological tests in clinical practice.

Re-standardization of the Korean- Instrumental Activities of Daily Living (K-IADL): Clinical Usefulness for Various Neurodegenerative Diseases

BACKGROUND AND PURPOSE: Evaluating instrumental activities of daily living (IADL) is an important part of procedure to diagnose dementia. The Korean-Instrumental Activities of Daily Living (K-IADL) has been used extensively in Korea. However, its cut-off score has not been reformulated since 2002. The purpose of this study was to yield a new optimal cut-off score for the K-IADL and confirm the validity of this new cut-off score with various dementia groups. METHODS: We retrospectively collected a total of 2,347 patients' K-IADL data from 6 general hospitals in Korea. These patients had mild cognitive impairment (MCI) or dementia with various etiologies for cognitive impairment. We also recruited a normal control group (n=254) from the community. Korean-Mini Mental State Examination, Short version of the Geriatric Depression Scale, Clinical Dementia Rating, and Global Deterioration Scale were administered to all participants. Caregivers completed K-IADL and Barthel Index. RESULTS: K-IADL scores were significantly different among dementia subgroups, but not significantly different among MCI subgroups. Based on internal consistency, correlations with other scales, and factor analysis, K-IADL showed excellent reliability and validity. The new optimal cut-off score to diagnose dementia was 0.40, which gave a sensitivity of 0.901 and a specificity of 0.916. Positive predictive value for dementia using the new cut-off score was 94.2% for Alzheimer's disease, 100% for vascular dementia, and 84% for Parkinson's disease. CONCLUSIONS: Our results illustrate that the new K-IADL cut-off score of 0.40 is reliable and valid for screening impairments of daily functioning resulting from various etiologies.

The Difference of Verbal Fluency Task Performance between Alzheimer's Disease and Subcortical Vascular Dementia: CREDOS (Clinical Research Center for Dementia of South Korea) Study

BACKGROUND: The verbal fluency test consists of two separate tests of semantic fluency and phonemic fluency. The performance patterns of these tests differ with the type of dementia. We studied the patterns of verbal fluency between Alzheimer's disease (AD) and subcortical vascular dementia (SVaD), and assessed the clinical utility of these tests. METHODS: The 1,475 selected participants comprised 73 normal control subjects, 673 patients with amnestic mild cognitive impairment (aMCI), 535 AD patients, 42 patients with subcortical vascular mild cognitive impairment (svMCI), and 152 SVaD patients. We analyzed the z-score for the total number of animal items as a semantic fluency index and the z-score of the phonemic total score as a phonemic fluency index. RESULTS: The performance of semantic fluency was lower than that of phonemic fluency in all groups. The SVaD group showed the worst scores and abnormal performances on both tests, while the AD group presented abnormal performance only for semantic fluency. Dividing the patients with dementia according to severity revealed a different pattern between AD and SVaD for the clinical dementia rating (CDR) stage of 0.5. The performance of the AD group declined gradually with CDR. However, the SVaD group performed very poorly in both tests even for very mild dementia (CDR stage of 0.5). The aMCI and svMCI groups exhibited similar performance patterns. CONCLUSIONS: The pattern of semantic and phonemic fluency was not clinically useful at the MCI stage, but it could be helpful in differentiating AD and SVaD in the early stage of dementia.