Remarkably, progressive MS has stood the test of time and is still with us. This is despite longstanding difficulties with the diagnosis of progressive MS, the onset of progressive MS in patients with initial relapse onset disease, the translation of conceptual progressive MS to the individual patient and importantly a secure understanding of the processes underlying progression. Nevertheless, despite these difficulties there is appreciable progress in all these areas which will be highlighted to illustrate the changes that are under way. Firstly, a diagnosis of primary progressive MS depends on the absence of a recognised relapse. Fortunately, we now have one highly effective anti-inflammatory medication approved for primary progressive MS. This, in certain circumstances, negates the requirement to delay using anti-inflammatory medication until a relapse or the MRI equivalent occurs. Secondly, many cases of secondary progressive MS have identifiable inflammation and anti-inflammatory medication can improve disability as well as protect relatively spared areas of the CNS such as pathways to the upper limbs and cognition. As a consequence of these changes there is evolving evidence that the effects of secondary progressive MS can be curtailed, if not prevented, by the early use of effective anti-inflammatory medication. Thirdly, there is increasing evidence that the use of progressive worsening of the EDSS in progressive MS treatment trials was likely responsible for the confounding negative outcomes. There is now increasing realisation that advancing lower limb long tract signs more realistically represents degeneration consequent upon past cumulative inflammatory injury at least in part. Fourthly, researchers are now dissecting identifiable pathways that activate the innate immune system and searching to repurpose drugs to modify such activation. The imminent availability of disease activity sensitive fluid biomarkers combined with advances in MRI use in enriched specific patient populations presents the possibility of both positive proof of concept trials to understand the pathogenesis of progression and of therapies targeted to identified pathogenesis rather than to disease phenotypes.
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