Aging
ALS
Tau pathology can be observed without Ab deposits (Bl.93, Hn.95). Ab deposits are always observed with tau, at least in the entorhinal cortex
Delacourte A et al. Nonoverlapping but synergetic Tau and APP pathologies in sporadic Alzheimer's disease. Neurology 2002; 59: 398-407.
In fact, as observed in several hundreds of non-demented and demented cases, the extent of tau and Abeta pathologies are linked.