I looked at this when my father went in.
It's called continuing healthcare
http://www.nhs.uk/chq...=68&SubCategoryID=681
He also has dementia but that's very unlikely to qualify on its own.
There is a checklist that is done first and if the score is high enough it goes for a detailed evaluation. There is an appeal process I guess that money is what it would cost to have a lawyer argue the case.
As I say though if the only medical condition is just dementia it would not really have any chance of sucess.