My dad has this. Basically he has lung cancer and as a rare complication of that, his own immune system has attacked his brain and brain stem. It is very hard to diagnose, often process of elimination and harder to treat. He has not responded to any of the standard treatments and gets worse by the day. He started with memory loss, confusion and balance issues. Now he can hardly talk, does not understand what we say to him, cannot walk well due to balance issues, has behavioural problems similar to a severely autistic child. He has been in hospital for around 4 weeks now on a neurological unit, but we have a meeting with the doctor tomorrow and we basically feel they have now given up, no treatment options really available and they are at the point where the damage is so severe he cannot come back from this so he will be discharged to a nursing home.
Really struggling to accept this and watch my Dad become just someone who sits in a chair dribbling and making no sense and not really aware of anything. 4 months ago he was cycling, windsurfing and was a very fit and well 64 year old.