Purpose : The development and validation of molecular imaging markers for the neuropathological hallmarks of neurodegenerative diseases associated with cognitive impairment is a reality since two decades. Amyloid PET tracers have been validated analytically and are currently tested for their clinical utility. More recently tracers targeting specifically tau deposits have been developed and are currently tested in large clinical studies. The availability of these markers opens the possibility for precision medicine in a field that was limited by a gold standard diagnosis occurring only postmortem. Aim of this review is to summarize the main findings obtained using tau-specific PET tracers in clinical cohorts of patients with cognitive impairment.

Methods and Results : We report the results of a systematic literature review. Various approaches for automated image assessment have been tested, while visual rating strategies have not been validated yet. In the AD spectrum an increase in cortical binding has been consistently observed, with a topography correlated with the profile of cognitive impairment and in agreement with the knowledge on tau pathology from neuropathological series. The evidence in non-AD diseases is more limited, with discordant findings in different cohorts and with different tracers.

Conclusion : Post-mortem validations of in vivo data in large cohorts and studies investigating the clinical added value of this biomarker in comparison with others will be required before routine clinical use of this new modality.