A previous study has similarly suggested that neuronal, rather than glial, tau is particularly associated with neurodegeneration.58 The lack of an association in PSP-SL could be explained by PSP-SL having maxed out tau severity scores, which would not give enough range to estimate the putative presence of a correlation, in contrast with PSP-RS, which showed more within-group tau score variability. This evidence concerns the gene MAPT and supranuclear palsy, progressive, 1.