What a really useful thread 
My dad developed MS at age 58 and within 8 months that had progressed to a neurological dementia as a result. He was already physically disabled anyway so my mum had to have him cared for in a hospital (special dementia wing) because she couldn't physically manage him. Of course everyone else in the hospital was 80+ and no one really knew what to do with him. He was very quiet and withdrawn and just also a lot. Thankfully died from a stroke about a year after diagnosis. I was 21 so it was a steep learning curve for me seeing that.
My FIL was diagnosed in about 2013 after we were concerned about his behaviour (odd, not violent). I knew how it would progress and tried hard to prepare DH for it but he and his mum (his parents were divorced for 35 yrs) refused to accept the inevitable. MIL would say "oh he's picked up today, I think he's on the mend"  Luckily we lived close by and I took on the primary cater role which wasn't too onerous to start with, and we made a huge effort to make his days fun while he could enjoy them. Also organised his POA and financial affairs while he could authorise that.
After 6 months of double incontinence, 3am phone calls and burning things in the oven, his twice-daily professional care staff said they could no longer look after him effectively and he needed 24hr care. GP thought he'd live another year. Lovely private dementia care home with amazing staff and facilities. And he survived another 3.5yrs! But for the last year was bed-ridden, almost non-verbal, unable to do anything at all. Endless aspiration infections. Heartbreaking to watch. Thankfully died this July, peacefully, with staff talking to him.
@TheMustressMhor you asked about meds. FIL started on Donepezil on diagnosis and it made a big difference. After about 3yrs it stopped working and he was changed to memamtine, which seemed to work although the care staff had to alter the times at which he took it depending on how it made him react. I think at one point he had a slow-release patch but that didn't seem effective. He was given sedatives once or twice a week to calm him; I know that this is sometimes frowned on by GPs and others but it was always documented and his behaviour witnessed and recorded impeccably so there was no doubt in our minds that they were doing the right thing by him.
I have made it clear that should I get a dementia diagnosis, I would want to be PTS fairly soon. Dignitas need the patient to be Able to consent to it and I've found that people I talk to don't seem to realise that you just don't "get better". I would rather lose a year of almost-normal life than to put my children through 5-10 years of my decline because I didn't take action soon enough.
I am pretty vocal about stuff like this and some find it a bit callous I suppose. But being honest about illness and death is for me the only way to cope, We are all going to die after all
I have been asked a few times for advice on dealing with early dementia and I always say Get their affairs in order, have a last holiday (or similar) together, talk to them about funeral plans, take lots of pictures so you have tangible proof of happier times, and try to prepare all the family for what is going to happen. My kids knew every step of what was happening to grandad - I needed to share it for my own mental health - and so the end didn't come as a shock. Maybe we're an odd family but this worked for us.
Sorry for the long ramble, thanks for letting me get it off my chest.
for you all who are living through the twilight half-life of dementia 