MAPT and Alzheimer disease: Differentiating CBS-AD from CBS-FTLD would reduce clinical and neuropathological heterogeneity in tau-directed therapeutic trials, as initially proposed in the CBD criteria.10 Prior clinical trials enrolling individuals with CBS have used Aβ PET or cerebrospinal fluid for this purpose, but this approach has significant study costs and has prevented participation of centers who lacked access to PET as well as enrollment of participants unwilling to undergo lumbar puncture.7,49