I know when my ex-charge got the BLOODY OBVIOUS signs of dementia and I was running her around to psychogeriatricians trying to figure out if it WAS a form of dementia they asked me if she had been in any major car accidents or had any significant blows to the head during her life because that can have something to do with some kind of 'induced' dementia .........
She had been in a few accidents, but only broken ribs .. and of course, by the time they were asking, she had lost cognition of words and didn't understand what people wanted to know ...
There is a lady I know who used to be an absolute HORROR in her pre-dementia days .. but had to have brain surgery (you should feel her skull, ewwww ... lumpy bumpy) and she's got a significant case of dementia and schitzaphrenia created by the surgery .... saved her life in one end, but gave her a warped quality of life in another??

Makes ya wonder.
Get the scan done, at least you will have some ANSWERS HOPEFULLY.
Cheers