Tau stages versus Ab deposition in aging and Alzheimer's disease

1. Tau pathology can spread from the entorhinal cortex (S2) to the hippocampus (S3), without Abeta deposits
    

Tau pathology spreads from S3 to S10 only in the presence of Ab deposits, suggesting a synergy between both degenerative processes.
 
  Delacourte A et al. Nonoverlapping but synergetic Tau and APP pathologies in sporadic Alzheimer's disease.
Neurology 2002; 59: 398-407.

 

In other words, in sporadic AD, tau pathology is upstream Ab deposition.