I Have been looking at the subject since I recently entered a very active stage of my MS. I am JC virus positive and am planning to start the medication, then discontinue after one year, in order to try to cool off the disease. Hoping to start BG-12 if/when it becomes approved.
I am aware of 2 studies that try to address the rebound effect. There are likely more out there.
1) http://archneur.ama-assn.org/cgi/conten ... t/68/2/186
The first finds a very significant rebound effect in a small number of patients. The second (which I believe was funded by the drug company) found a return to baseline disease activity without a rebound in a very large group of patients.
I spoke to my MS specialist about this very topic. He thinks there very likely is a rebound effect in some patients. This should typically be seen around the 3-4 month mark after discontinuation of natalizumab. However, as those of us with MS know, everyone is different. And certainly, not everyone will experience this rebound effect. Furthermore, it is his opinion that this effect can be minimized with disease modifying agents. (So it's good you're taking Gilenya if you're worried about rebounding.) Also, steroids might be of use, especially if you feel another relapse coming on.
I certainly second Lynda's suggestion that you speak with your physician ASAP if you're not feeling good. As for the linked article ... not to minimize the risks associated with taking any of these powerful medications, but if you've been taking Gilenya for some time I wouldn't worry about the questions surrounding these deaths. The cardiac effects, which have been well documented, seem limited to the time of the first dose. This shouldn't have much to do with "not feeling good", in my humble opinion.
Would you mind giving an update when possible? God bless.