The first was "dementia" (or something related to it, I don't remember the exact medical term). The second was something to do with fluid in some spinal column (I am sorry once again, I do not remember the medical term; they operated on him to drain it, which is why I remember it). I don't remember the third one, unfortunately.
Perhaps a CSF leak due to a dural sack tear in the spine? Was his symptom only having headaches while standing? Happened to my wife. 6 weeks of absolute hell.
On second thought — the opposite. A bulge/blockage of CSF?
Apparently, as I've recently learned due to a debilitating headache, CSF pressure (both high and low) can cause a whole host of symptoms, ranging from mild headache and blurred vision to coma and death.
It's pretty wild that a doctor wouldn't have that as a hypothesis.