The latter correlation suggests a close relationship between not only microglial activation and tau pathology,1 7 but also with neurodegeneration in those subcortical regions commonly associated with pathological hallmarks of PSP.30 Our findings align with studies of AD, another tauopathy, in which baseline in vivo PET markers of tau pathology and microglial activation predicted clinical progression, outperforming structural MRI.31 Here, MAPT is linked to Alzheimer disease.