We have a 14 year old male Boston Terrier.  He first went blind, then lost his hearing and I'm afraid he now has doggie dementia.  He used to be able to find his way from anywhere in the yard back into the house, but now we find him outside walking in circles and other times just motionless and staring into space.   We are at the point where we need to carry him back into the house every time he goes out.  So sad to watch him slow down like this. 

I had a ktty with dementia. She would cry at night no reason. Would forget where food was.  She would stop while walking and look so lost. She lived to 19.5.