[Awareness disorders in Alzheimer's disease and in mild cognitive impairment]

Awareness disorders in Alzheimer's disease still remains unclear despite much research regarding this phenomenon. Papers report various and contrasted results with varying frequency from one study to another. Hence, the interest in awareness in Alzheimer's disease remains limited. Nevertheless, this symptom is closely associated with caregivers' burden and increases the patient's dependency, since the patient is unable to avoid dangers, requiring some care services or institutionalization The purpose of this current review is to recall the main neuro-anatomical and theoretical basis of awareness disorders, and to highlight the recent findings in Alzheimer's disease and in its pre-clinical stages.

With this in mind, we have conducted a non-exhaustive search using the pubmed online database to collect the most important reviews and the most recent findings regarding awareness disorders in Mild Cognitive Impairment (MCI) and/or in Alzheimer's disease.

In Alzheimer's disease, the links between awareness disorders and other variables, such as severity of dementia or depression, change from one study to the other and do not permit one to understand whether unawareness is an intrinsic or extrinsic reaction to the pathological process itself. Recent results suggest executive, cognitive and behavioral correlates more than psychopathological correlates, although the latter cannot be excluded. In Mild Cognitive Impairment, studies show varied results. Some studies report that patients suffering from Mild Cognitive Impairment can be compared to healthy control subjects and both groups have better awareness than patients with Alzheimer's disease. However, other studies show contrary results and awareness disorders might be a predictor of conversion from Mild Cognitive Impairment to dementia, as with apathy, in which the ability to cope with difficulties represents one of the main features.

These controversial results are due to the heterogeneity of Alzheimer patients and in particular of MCI patients, but also to various conceptions of awareness disorders in Alzheimer's disease; none of them, however, taking into account all its diversity and complexity. Thus, neurological approaches underline neuropsychological dysfunctions linked to right frontal and/or hemispheric damage but are based on brain injury or strokes, which are events that differ greatly from a neurodegenerative disease involving progressive cognitive, emotional and social disturbances. Psychiatric approaches have taken into account the various aspects of insight, which before were often forbidden and reduced to a categorical point of view, and so could contribute to a better understanding of awareness disorders in Alzheimer's disease. However, these aspects have been conceptualized for psychiatric patients, suffering from positive symptoms, where compliance in treatment is the central key. Insight in neurological diseases is more focused on negative symptoms and generally concerns a basic perception of impairments in mainly cognitive domains. Moreover, modeling has often opposed neurological and psychological mechanisms, so awareness disorders are out of scope of a primary and secondary symptomatology. Although some authors have proposed to take into account these two mechanisms (unawareness and denial), clinical practice has shown that it was impossible to distinguish them both. Finally, some social cognitive approaches are able to demonstrate that there is no correlation between severity of dementia and awareness disorders. Nevertheless, the Self-concept, underlying this point of view, does not permit distinguishing neuropsychological from psycho-social factors. Moreover, only one evaluation tool based on Self-modeling in Alzheimer's disease exists, and to conceptualize Self in a specific pathology does not permit the comparison of this pathology to others or to healthy control subjects. So, the authors present the multidimensional model proposed by Clare et al., and some perspectives to stimulate future research, and perform potential meta-analyses.