How to Diagnose an Alzheimer Disease?

Abstract

Alzheimer’s disease is a neurodegenerative disorder characterized by an insidious onset, a gradual decline in cognitive functions, a constant but frequent occurrence of non-cognitive disturbances (psychological and behavioral disorders) and inexorably leading to a loss of functional autonomy. Alzheimer’s dementia corresponds to the stage of the illness during which the clinical symptoms (affecting memory and other areas) are sufficient to alter the activities of everyday life. Typical Alzheimer’s disease (common form) is characterized by the installation of an early and significant progressive deficit of the episodic memory that will always remain dominant. Behavioral and psychological symptoms of dementia represent common clinical features of dementias, contributing to the heterogeneous phenotypic expression of Alzheimer’s disease. Recently proposed diagnostic criteria, in addition to the clinical neuropsychological examination aimed at identifying the typical AD symptoms, include staging criteria based on AD biological measures related to its pathology. Despite the obvious benefits of these new criteria, an accurate diagnosis is not always easily reached because, particularly in its earliest stages, the symptoms of the disease are very variable. Biological measures, or biomarkers, of the disease should first facilitate an early and accurate diagnosis, have a prognostic and predictive value, and have the capacity to monitor therapeutic efficacy. Amyloid imaging and CSF tau/A p ratio may be useful in the differential diagnosis with other neurodegenerative dementias, especially, in early onset cases the evolution during which it will associate with other cognitive disorders.