There has been spin that BG-12 was going to be neuroprotective, but the drug was not universally effective in atrophy measures and the question of CNS penetration has not been clarified.
It shows us that drugs come with risk profiles and this problem may have been avoided by a risk-averse neuro,who would not prescribed off-label.
However, there may have been gadolinium lesions in the PPMS case.