Laura, this is a little outdated now, but is fairly accurate with regards to the potential damage that can occur with PML:

http://www.ninds.nih.gov/disorders/pml/pml.htm

It "looks" a lot like an accelerated and ugly version of MS; in test results, symptoms, and longer-term disability (if the patient survives), so that is one reason it is critical for PwMS to be managed by specialists who recognize the symptoms and perform the necessary testing as soon as possible.

Historically, it most often killed non-AID's patients who got it (i.e. those who who got it due to pharmacological agents, like Tysabri). Biogen has determined a way to cleanse Tysabri out of the body quickly though (Plasma), and they are actively testing alternative treatments to manage the disease when it occurs. Hence, more people are surviving PML (and IRIS which sometimes occurs at the same time) ... but we don't really know too much about the patients quality of life if they do make it through.

The US has the TOUCH program, which monitors patients on Tysabri fairly stringently. That is not true in Canada though ... and as you know, MRI's (and LP's) are not something they will usually do at the drop of a hat here.

I would be truly shocked if anyone would agree to Tysabri after getting PML once. In fact, depending on how much damage occurs the first time, some people might immediately opt to not try to recover from PML, i.e. refuse Plasma, and choose probable death over THAT quality of life. I doubt that it would be permitted anyway, as I believe that a pre-requisite for Tysabri is that a person does not have PML already.

Cherie