Up until now, most clinical drug trials (especially those involving the CRABs) have used MRI results in showing that their drugs have had an effect on the progression of MS. Yet, per Dr. Myles, there is a best at modest correlation between the number of lesions and disability.
So what good is it to learn that "drug X" showed a 35% reduction in the number lesions over placebo when that really doesn't mean much in pinpointing whether a drug has helped. While fewer lesions generally is better, it certainly isn't the best way to know how an MS patient is really doing. Yet this criteria is used in marketing these drugs!