Might be a case of both, but immune-suppressent drugs are now available.................
“but immune-suppressent drugs are now available.....”
Those drugs invite a whole new set of problems - a supressed immune system allows all sorts of diseases to enter the body unopposed. Using a broad spectrum of antibiotics to fight those invite yet more problems. The likeliest causes of death may be MRSA infections, organs shutting down and pneumonia. For a number of reasons, I think the odds against surviving more than a few weeks are stupendous.
So far, men of science are incapable of creating even a living amoeba from scratch. Successful head transplants might be a great deal more complicated than that.