Who in ACDC has dementia?

Excuse me, could you please clarify the context of your question? Are you referring to the rock band AC/DC and suggesting that one of its members might have dementia? If so, I must say that I'm not aware of any public announcements or reports indicating that any member of AC/DC currently suffers from dementia. However, if this is a hypothetical scenario or if you're asking in the context of a fictional story or documentary, I would still need more information to provide a meaningful response. Could you please elaborate on your question or provide some additional context?