I am on Tysabri. They checked for the JC virus but never told me if I was positive or negative. The Doc. did tell me he would only keep me on Tysabri for one year. I made to decision to go on Tysabri based on the fact that I have a leison on my cord at the C2 that grew twice the size in 6 months time. And I developed another one on my cord at the C3. So if they keep growing at that rate I will have a disconnect and that will shut me off like a switch. So I'm damned if I do or damned if I don't. I know they will be drawing blood every two months. So there you have it. Sometimes there are no other options.

Symptoms of PML can develop over several weeks to months. Symptoms depend on location of damage in the brain and the degree of damage. The most prominent symptoms are "clumsiness, progressive weakness and visual, speech, and sometimes personality changes"[3] The lesions affecting the parietal and occipital lobes can lead to a phenomenon known as alien hand syndrome

Don’t be afraid. Obviously the decision is yours but it has honestly been a life changer for me and a friend.
Been on it since 2011, no relapses or side effects.

They want to start me on this but afraid

I have been on tysabri for 6 years
I call it a miracle drug
I forget I have ms
Tested every 3 months for jcv, negative so far
Can’t recommend it highly enough :)