My neuro's thought on follow-up MRIs is: would we make a change in my therapy based on new MRI results? I had a follow-up MRI after 6 months on Rebif. Externally, I was doing just fine, but we all know that disease activity doesn't correlate well with symptoms. We decided if my brain had been flowering with lots of new lesions (it wasn't), we would consider a different therapy. I've had 2 (or is it 3 now?) other MRIs in the 2.5 years since. Each was after appearance of new symptoms. I should explain that all my symptoms have been very mild (and each has been more mild than the last) and they have all been temporary. I am, however, being extremely aggressive with my monitoring of this disease and my neuro is fine with that. We get along well and seem to be on the same page.
All my MRIs have been virtually identical to one another (any differences could easily be attributed to the slightly different angle of the imagery). On a side note, it's kind of cool to see the images side-by-side, and step through the series of pictures. I think some of my symptoms have probably been caused by inflammation in my spine, but I've never had an MRI beyond the brain and brainstem. My neuro's thought on this is that the vast majority of myelin and axon material is in the brain and brainstem and so if there's any disease associated inflammation, you should pick it up with the brain MRI. For this reason, he thinks the spinal MRI is an unnecessary expense. I haven't pushed this point, but may some day.
As for neutralizing antibodies, I had a blood test for this when I had one of these new mild symptoms. I can't remember if this was around 6 or 12 months after starting Rebif. The levels were indeed a little elevated, but not alarmingly so. So I stayed the course and was re-tested 6 months later, when the levels had dropped back down. I've heard/read that this pattern of temporary elevation of NAbs is fairly common.