My mother may have developed this condition, in the last few weeks before passing, after being treated for a few months for blood cancer, she had habitually not drunk enough fluid so to ensure less trips where anyone would need to help her get up and go to the toilet. (Chronic dehydration can also cause lesions in the brain.) In the last month unfortunately most of doctors and nurses caring for her did not want to acknowledge or perhaps even aware she was severely dehydrated due to a normal blood pressure (before they were even aware of lesions) - oh I think a slight frame with a small amount of fat, losing 3 to 6 or more cups more than any liquid consumed on a daily basis over three weeks or more - common sense should have pointed out some of her observed conditions were due to something other than PML (lesions confirmed [but not the cause] two and half weeks before her passing) or medications.