It would seem that there is an issue with the multiple sclerosis drug
Tysabri, also know as natalizumab, possibly causing PML, progressive
multifocal Leukoencephalopathy. The FDA has even issued a public health
advisory about this to help inform patients of the dangers. If you check out
https://www.lawyersandsettlements.com/case/tysabri there is more information
on this as well as what you can do about it. There is also a free case
evaluation provided for those who might have been affected by this. I hope
this may be of some help.
kr0