Inadequate outcome measures are the biggest impediment to successful clinical trials in progressive MS - YES.

The closer progressive multiple sclerosis (MS) is approached, the more awkward it is to define and the more slippery it is to measure. Of course on one level it is easy – if 5 years previously a person affected by MS can walk or see or balance normally, but now they walk with a stick or have a visual acuity of 6/60 or are falling over, then it is clear (to anyone) that progression has occurred, whichever yardstick is used. No, the problem is that progression is (generally) slow, it is multidimensional and the time frequency of such very hard clinical end-points is too low to be of value in the 2-3 year life span of trials in progressive MS.