Classification and Early Diagnosis of Cognitive Impairments

The recent developments in drug treatments for Alzheimer's disease (AD) and other dementias, have highlighted the importance of early diagnosis and the need to characterize the cognitive profile of the earliest stages of the disease. The final result in dementia is well known to the physicians and it is not difficult to make the diagnosis especially in its late phases. However, several problems remain in terms of diagnosis, particularly in its early stages. To provide a few examples that will be developed in this chapter, the clinical diagnosis of very early dementia and its differentiation from normal aging remains problematic. Recent research has identified a transitional state between the cognitive changes of normal aging and AD, known as Mild Cognitive Impairment (MCI). Another problem is the differential diagnosis between different forms of dementia which is complicated by the fact there is a genuine overlap between the pathology of AD and the pathology observed in many other disorders.
This presentation will discuss briefly the neuropsychology of normal aging and of the entity known as benign senescent forgetfulness or age-associated memory impairment. It will then review the rationale of the criteria that have been proposed to diagnose patients with MCI. An important issue in the early diagnosis of AD is also the differential diagnosis with VaD. Especially the new concept of Subcortical Vascular Cognitive Impairment (VCI) will be discussed. In this context, a better understanding of neuropsychological differences between MCI and VCI may have important implications for the differential diagnosis of these disorders.