One of the major changes in our thinking about multiple sclerosis is that the disease is really quite more active than what we see clinically. I think our best insight to that has been a series of new studies where people have MRI scans of their head done at very frequent intervals, and we find new areas of inflammation coming and going in people without clinical attacks, sometimes as many as 10 new spots on the MRI for every one major clinical attack. So the disease is more active than just exacerbations.
DAVID R. MARKS, MD: Jeff, why the disparity between the MRI findings and the symptomatology?
JEFFREY GREENSTEIN, MD: We think that part of the explanation for this is that eloquent areas in the brain are not always affected by what's going on. For example, an area that might cause a clinical problem might cause weakness and be very apparent, but an area that may be involved with cognitive function may not be as readily apparent. Also, there may be some effect of summations, so that you have to have a repeat episode or repetitive episodes occur before the symptom actually becomes manifest. These things might explain why there can be disease activity going on in the brain without it being apparent to the person who actually has the disease.
DAVID R. MARKS, MD: But it's still going on.
JEFFREY GREENSTEIN, MD: It's still going on.
DAVID R. MARKS, MD: What role does atrophy in the brain play in this disease?