MAPT and Alzheimer disease: In AD, Tau proteins form neurofibrillary tangles that accumulate, leading to neurodegeneration in the presence of Aβ.88,89 Aβ42 and tau were found to be associated with lesion load and grey matter loss,88 suggesting that inflammation might alter Aβ42 expression and thus cause diffuse cerebral disconnection.90, –92 As such, tau and proteins of amyloid metabolism and precursor-like proteins might be useful in monitoring the longitudinal trajectory of cognition in MS patients.91,93,94 Monitoring of tau proteins may be accomplished using tau PET.