MAPT and Alzheimer disease: Based on the assumption that CSF analysis may mirror pathological biochemical processes in the brain, and despite the low solubility of NFTs and their constituting aggregated tau fibrils [124,125], an early case series reported the detection and elevation of pathological forms of tau in the CSF of AD patients compared to controls, thus heralding its use as CSF biomarker for the diagnosis of AD [126].