Insanity or Paralysis or Both?

Go over to medlineplus.org and do a search on gliosis. That may help you a bit.

Dementias such as Alzheimers Disease produce a measureable change in brain function - but can only be seen post mortem - do you want to kill off your character?

Advanced oor terminal syphilis - old terminology was - Generalised Paralysis of the Insane - GPI.

AIDS can certainly have an effect on the brain - but that's more end-stage - so the patient would probably not be in a mental health facility, but rather a terminal care facility.

Yep


Well you are quite right. This persona is based a lot on myself. So I know how I would want this person to act and react, what they would be sick of. And mostly, I'm curently revising so I need a disease to fit certain criteria so that I don't need to revise too much.