[Biological markers in the diagnosis of dementia and Alzheimer's disease].

Alzheimer's disease is the leading cause of dementia in advanced age with a prevalence of above 40% among persons 80 years or older. In recent years, new studies have made some important discoveries regarding the pathogenesis of the diseases and potential therapeutic measures. These developments have led to the announcement of new guidelines for the diagnosis of the disease published by the National Institute on Aging and the ALzheimer's Association. These guidelines expand the definition of ALzheimer's disease to include 2 new phases of the disease: pre-symptomatic and mildly symptomatic but pre-dementia. For the first time, the guidelines also incorporated the usage of biological markers to assist in the diagnosis of the disease, although they are still only in the research agenda. These biomarkers include atrophy of the medial temporal lobe by MRI, reduction of glucose metabolism in specific brain areas by PET-FDG and presence of beta-amyloid staining in the brain by PET-amyloid scan. In addition, there are also cerebrospinal fluid ICSF) biomarkers characteristic of Alzheimer's disease, which consist of low levels of Abeta42 and elevated levels of total and phosphorylated TAU. These biomarkers may be used to diagnose the disease in the early pre-symptomatic phase, to differentiate Alzheimer's disease from other causes of dementia and may be helpful in the follow-up of newly developed specific treatments.