I’ve been teaching myself ASL over the last year or two, a tiny bit at a time, and thought about this exact issue. I don’t think there’s a thing like what you’re asking, which is a huge gap in care. Dementia care in the US is lacking in big ways, so I’d be surprised if we had anything that met the needs of the Deaf: we just aren’t progressive enough as a country with our healthcare.
What I will say is this, though: in later stages of dementia, a lot of people who speak English as a second language go back to speaking their original language, therefore creating a sort of language barrier between them and everyone else. What I’ve learned in these cases is that the person’s expression and body language means a lot more than their actual words.