Today, the Alzheimer's disease (AD) diagnosis is founded not only on clinical criteria but also on complementary examinations to confirm a physiopathological process of AD. In complex cases, lumbar punction could be necessary in order to measure Aβ peptides and Total and phosphorylated Tau but new biomarkers could be useful. The main objective of this project is to conserve these cerebrospinal fluids, collected in usual practice in order to validate new biomarkers for diagnosis, prognosis or therapeutic following of Alzheimer's disease and other dementia.