MAPT and Alzheimer disease: To this point, we previously reported that higher levels of the 20-22kDa NH2-truncated form of human tau - a neurotoxic fragment of the full length protein (htau40) mapping between 26 and 230 aminoacids of the longest human tau isoform- are largely detectable in presynaptic terminals [24, 25, 26] as well in peripheral CSFs from living patients affected by AD and not-AD human neurodegenerative diseases associated to dementias [27].