Anosognosia and Alzheimer's Disease

Abstract

Neurological patients can be entirely unaware of their disease; this phenomenon is called anosognosia and it has been shown in different sensory-motor and cognitive domains. Lack of awareness has been investigated in Alzheimer's disease (AD) and within different domains of it. In the present article we review the literature on anosognosia for AD that had been indexed on the Medline database until the end of 2004. Historical introduction to the subject is followed by a brief description of the anatomy and clinical characteristics of AD. An analysis of a number of studies that focus on the relationship between anosognosia and AD then follows. This review shows that anosognosia is typical in AD, compared with other types of dementia, and it is a distinctive feature in the most severe cases and particularly in the beginning phases of illness. From an anatomical point of view, anosognosia seems to be strictly connected to frontal lobe areas; in fact, patients with anosognosia and AD show a reduction of cerebral haematic flow in the frontal regions, as well as deficits of executive functions and extrapyramidal signs. Interestingly, co-occurring depression could be interpreted as an adaptive behavior to counter the effects of perceived loss of cognitive abilities. Finally, self-awareness in AD could have some common mechanisms with auto-monitoring in schizophrenia.