MAPT and Alzheimer disease: When these imaging biomarkers are not sufficient to establish a clear diagnosis, and certainly in case of differential diagnostic doubt with (atypical presentation of) AD, we suggest a further exploration through the analysis of CSF biomarkers Aβ1–42, Aβ1–42/Aβ1–40 ratio, T-tau and P-tau181 that can indicate the presence of AD with good accuracy.