PML has a pretty rapid course. It starts affecting the brain before anyone usually notices what's happening. That's why you have to be vigilant to any changes. Confirming it on MRI means the damage has already started.

The doc asks the old man at every visit if I have had any changes in my thinking or odd behaviors and reminds him to watch for them too and not to wait, just call him, and not to argue with me over it......like I wouldn't believe I'm sick or something!

He's said it enough that I listen to my body closely. He also stresses that anything that looks or feels even mildly like a relapse is a reason to call. Those will be the first symptoms.

He's not big on MRIs unless they are necessary, and I've only had two since I started. Those were at yearly intervals to see what's happening in my flip top head. They were excellent.