[What use of biological markers for the diagnosis of Alzheimer's disease and associated disorders?].

Etiological diagnosis of mild cognitive impairment (MCI) or dementia requires combined clinical, neuropsychological, biological and neuro-imaging clues. The diagnostic value of biological and neuro-imaging biomarkers has recently increased according to neuropathological studies. Biomarkers help for making the in vivo diagnosis of underlying histological lesions, sometimes of combined lesions. Sensitivity and specificity of CSF biomarkers, i.e. tau, phospho-tau and amyloid, is now over 85% for Alzheimer's disease (AD) diagnosis at the dementia and MCI stages. Brain MRI can suggest mild AD when depicting medial temporal lobe atrophy. DAT-SCAN(R) is indicated in cases suspected to have Lewy body dementia when parkinsonism is lacking. Metabolism and blood flow impairments observed by PET and SPECT in posterior cortical areas, in particular in posterior cingulate and parieto-temporo-occipital junction, are highly suggestive of AD in atypical cases. International research is currently focalised on research of possible serum biomarkers and neuro-imaging techniques using tracers targeting the specific AD lesions.