Neuropsychological assessment of dementia: state of the art

Alzheimer's Disease: Prototype of Cognitive Deterioration, Valuable Lessons to Understand Human Cognition

It is important for neurologists to become more familiar with neuropsychological evaluation for Alzheimer disease. The growth of this method in research, as an available, inexpensive, and noninvasive diagnostic approach, which can be administered even by non-specialist-trained examiners, makes this knowledge more necessary than ever. Such knowledge has a basic role in planning national programs in primary health care systems for prevention and early detection of Alzheimer disease. This is more crucial in developing countries, which have higher rates of dementia prevalence along with cardiovascular risk factors, lack of public knowledge about dementia, and limited social support. In addition compared to the neurological hard signs which are tangible and measurable, the concept of cognition seems to be more difficult for the neurologists to evaluate and for the students to understand. Dementia in general and Alzheimer's disease as the prototype of cognitive disorders specifically, play an important role to explore all domains of human cognition through its symptomatology and neuropsychological deficits.

Impaired digit span can predict further cognitive decline in older people with subjective memory complaint: a preliminary result

Subjective memory complaint (SMC) is common among elderly people, and is thought to be part of mild cognitive impairment (MCI). We evaluated whether impaired digit span (IDS) in older people with SMC can predict wider impairment in future neuropsychological tests that correspond to MCI. After a mean of 6.6 years from the initial assessment, we reevaluated 16 subjects with SMC and normal digit span (NDS) scores (mean age 57.6 ± 8.1 years) and 28 subjects with SMC and IDS scores (mean age 59.7 ± 9.9 years). The IDS group showed wider cognitive decline in tests of short-term verbal memory and category verbal fluency compared to the NDS group. IDS scores indicate an earlier step for conversion of SMC to MCI.

The accuracy of the MMSE in detecting cognitive impairment when administered by general practitioners: a prospective observational study

Background

The Mini-Mental State Examination (MMSE) has contributed to detecting cognitive impairment, yet few studies have evaluated its accuracy when used by general practitioners (GP) in an actual public-health setting.

Objectives

We evaluated the accuracy of MMSE scores obtained by GPs by comparing them to scores obtained by Alzheimer's Evaluation Units (UVA).

Methods

The study was observational in design and involved 59 voluntary GPs who, after having undergone training, administered the MMSE to patients with symptoms of cognitive disturbances. Individuals who scored ≤ 24 (adjusted by age and educational level) were referred to Alzheimer's Evaluation Units (UVA) for diagnosis (including the MMSE). UVAs were unblinded to the MMSE score of the GP. To measure interrater agreement, the weighted Kappa statistic was calculated. To evaluate factors associated with the magnitude of the difference between paired scores, a linear regression model was applied. To quantify the accuracy in discriminating no cognitive impairment from any cognitive impairment and from Alzheimer's disease (AD), the ROC curves (AUC) were calculated.

Results

For the 317 patients, the mean score obtained by GPs was significantly lower (15.8 vs. 17.4 for the UVAs; p < 0.01). However, overall concordance was good (Kappa = 0.86). Only the diagnosis made by the UVA was associated with the difference between paired scores: the adjusted mean difference was 3.1 for no cognitive impairment and 3.8 for mild cognitive impairment. The AUC of the scores for GPs was 0.80 (95%CI: 0.75–0.86) for discriminating between no impairment and any impairment and 0.89 (95%CI: 0.84–0.94) for distinguishing patients with AD, though the UVA scores discriminated better.

Conclusion

In a public-health setting involving patients with symptoms of cognitive disturbances, the MMSE used by the GPs was sufficiently accurate to detect patients with cognitive impairment, particularly those with dementia.

Working memory impairment in a transgenic amyloid precursor protein TgCRND8 mouse model of Alzheimer's disease

The most profound deficits observed in Alzheimer's disease (AD) are in domains of episodic and working memory systems. Transgenic (Tg) mice expressing mutated human amyloid precursor protein (APP) genes offer a model to study the effect of AD pathology on cognition. We reported previously that APP TgCRND8 mice showed deficits in a reference and working memory evaluated in a Morris water-maze test. In this study, we evaluated the working memory of TgCRND8 mice comparing two training paradigms in a six-arm radial water maze. In the first paradigm, the exploration of the maze was constrained, forcing the mice to use a spatial mapping strategy. In the second paradigm, mice were unconstrained in their exploration of the maze. TgCRND8 mice proved to be significantly impaired in spatial working memory in both paradigms as compared with their non-transgenic littermates. The analysis of data revealed that forcing mice to use a spatial strategy during training caused only a moderate improvement in the performance of all mice. However, unconstrained exploration of the maze not only resulted in a fast learning in control mice, but also facilitated the development of a chaining strategy in spatially impaired TgCRND8 mice. In conclusion, TgCRND8 mice showed impairment in spatial working memory but retained a plasticity to choose alternative search strategies.