Serial MRI's (3-4 over the course of a year) put together with symptoms, history and physical exam are what is often needed to get the diagnosis. I think if you still do not know for sure, it's important to follow through to get the answers you need.

If your insurance does not cover the MRI's, the Multiple Sclerosis Associan of America has a funded program to provide for free MRIs to those for whom the cost is prohibative. Theri web address is www.msaa.com and you can find info there about this program. Hope it helps take the financial load off and get you some answers.