Dr. Boster: The way that I would consider a surveillance MRI scan is to look for asymptomatic disease activity. Imagine a patient who is clinically doing well; they're not having any MS attacks. When you examine them, their exam is stable in that it hasn't changed from the last time you saw them. Then you get an MRI scan and you find that they have four new T2 hyperintense lesions that they didn't have just a year ago. So you have this clinical/radiographic paradox where the patient's clinical presentation and their MRI don't match.
Dr. Rick Rudick demonstrated that, on interferon therapy, if you develop three or more new spots in the first two years, you prognostically are not going to do well on an interferon.1 That is terribly useful information for managing patients on interferon. Unfortunately, we don't have that same kind of data for all the different drugs.
The way that I have come to think of it is as follows: If you're on a given therapy, I will give you two strikes before I'm going to want to switch your therapy. Those two strikes can come one of three ways: Either you have clear, clinical disease activity, like an MS relapse—and you have to ask yourself, what is the annualized relapse rate of that drug? If we take an interferon or glatiramer for example, statistically we can expect to see an attack once every three years. If you have one attack, I can't tell you ”you've failed a therapy,” because maybe you won't have another attack for three years. If, however, a year later or two years later you have a second attack, your attack frequency is now inappropriate and I would consider switching their therapy.
An alternate way of hitting a strike is to have sustained disability on your examination. If you developed a limp and three months later when I see you in followup your limp is still there, you've accrued disability and that's a strike against you. A third way is to show progression on the MRI. The easiest thing to look for, in my opinion, is the development of new T2 hyperintense lesions or bright spots.
If you have MRI activity, with let's say four new T2 hyperintense lesions, I'm putting your
I will add a few things which have less data to support their use. T1 hypointensities, or black holes, correlate with disability as well.3 I like to look at the T1 to T2 ratio. I would like the ratio of bright spots to dark spots to be
Similarly, we know that atrophy is accelerated in the MS patient and we know that the drugs that have been FDA approved largely show slowing down of atrophy. Ideally, I would like to be able to easily measure atrophy in my clinic and I would like to change a drug when I see it, although I don't have those tools at my disposal at present.
One other thing: Maybe the