I have some information I would like to pass on to those here that are contemplating Tysabri therapy from a treating neurologist friend of mine regarding Tysabri and possible rare risk of PML (some of his patients are on Tysabri, and some of them are on the older generation ABCRs). Take good care now...Lauren
Without becoming too long-winded or using too many medical terms, he wanted me to try and explain to other MS patients that are afraid of PML, and informed me of the following:
"What are early symptoms of PML? I've seen PML 10-12 times, the last time in 2005.
Cortical blindness - a homonymous quadrantopsia or hemianopsia (rare but not impossible in MS) not to be confused with monocular blindness (or decreased vision) from optic neuritis (very common in MS);
Apathy/apraxia or other cognitive or personality changes referrable to frontal lobe dysfunction (assuming PML is located in that distribution).... rare to occur in MS in a short period of time.
Progressive weakness or progressive numbness/clumsiness - although numbness is extremely common in MS and weakness is fairly common, in PML these symptoms would be progressing over weeks vs. a rapid onset with stability or improvement in MS. This distinction may not seem clear but is, in reality, very clear in clinical practice.
Can progressive symptoms happen in MS? Certainly, if a person has several small exacerbations, an appearance of steady progression over weeks can be seen. Can PPMS look like PML? Generally no, as PPMS shows steady progression over months to years, not weeks.
Incontinence - seen as PML progresses....if this is occurring, mid to late PML is more likely. In MS, this is more likely to be in an urgency/frequency phase for years before progressing.
So, as can be seen, MS typically does not have symptoms overlapping with PML. However, now and then symptoms in MS could be worrisome for PML. 6% is as good a number as any.
When that occurs in my Tysabri patients I am immediately getting a MRI (I've ordered 3 - last one ordered Thursday and personally reviewed yesterday after a SPMS with relapses patient (with a history of Novantrone use in past) had 2 weeks of extreme fatigue coupled with apathy and very poor concentration). This one was the only one I was worried about, the other two were done more to allay patient fears that their mild sensory changes might represent PML.
All 3 MRIs have shown no new lesions (I've also done a half dozen 'one year' MRIs with no new lesions or 1 or 2 small new recent lesions only).
MRIs of MS and PML is usually very easy to differentiate.... but some radiologists and neurologists have never seen PML.
There is also plasmapheresis (plasma exchange) which, from the PLEX studies, could significantly reduce the concentration of TYSABRI in blood serum and alpha 4-integrin receptor saturation, should the need arise.
My case in 2005 of PML (HIV related) was read as 'subacute strokes or inflammatory lesions' and I had to straighten out the radiologist. I tapped (performed a spinal tap on) the patient the same day and got PCR confirmation 4 business days later (PCR confirmation is a very long and drawn out explanation, which I won't go into now). His symptoms were pure motor and sensory with no frontal lobe or vision loss signs, and it turns out he was having a relapse only, no signs of PML, which were easily treated with a short course of steroids."
Lastly, he said that if any MS patient currently on Tysabri has rapidly worsening symptoms, they should immediately contact their own neurologist, and he hoped that the above information would help other MS patients in overcoming fears of the very rare PML in MS.
The week before I had another relapse and now need my walking stick all the time 
- and the fatigue, sheesh well all I can say is it's exhausting being exhausted !
Its so frustrating this MS, so many things to think about with it.