Cognitive neurodegenerative diseases are a major public health issue. At present, the diagnosis of certainty is still based on anatomopathological analyses. Even if the diagnostic tools available to clinicians have made it possible to improve probabilistic diagnosis during the patient's lifetime, there are still too many diagnostic errors and sub-diagnostic in this field. The arrival of biomarkers has made it possible to reduce these diagnostic errors, which were of the order of 25 to 30%. This high error rate is due to different parameters. These diseases are numerous and often present common symptoms due to the fact that common brain structures are affected. These diseases evolve progressively over several years and their early diagnosis, when the symptoms are discrete, makes them even more difficult to diagnose at this stage. In addition, co-morbidities are common in the elderly, further complicating the diagnosis of these diseases. At present, the only cerebrospinal fluid (CSF) biomarkers that are routinely used for the biological diagnosis of neurodegenerative cognitive pathologies are those specific to Alzheimer's disease: Aβ42, Aβ40, Tau-total and Phospho-Tau. These biomarkers represent an almost indispensable tool in the diagnosis of dementia. It is therefore important to determine whether Alzheimer's biomarkers can be disrupted in other neurodegenerative cognitive pathologies, but also to find biomarkers specific to these different pathologies by facilitating the implementation of clinical studies which will thus make it possible to improve their diagnosis.