EAN 2026 | What are the key changes introduced in the 2024 revision of the McDonald diagnostic criteria for MS?

I think one of the first important changes that these criteria are bringing is that up to now, we were always saying that MS was a clinical diagnosis, but this is not the case anymore, and we are moving to a more biological diagnosis. And this is because we have understood that this disease doesn’t start when the patient presents the first clinical attack. But there are many things that happen before that already tell us that this disease is present. And we have now the tools, principally with MRI, to detect this disease in the prodrome or in the presymptomatic phase. So nowadays, we have tools that can be combined to detect this disease even in the preclinical phase of the disease. And this gives us this opportunity to move to a more biological diagnosis. So I think this is one of the most important changes of the diagnostic criteria. The second thing that I would like to highlight is that these criteria give us like a box of tools that we can use to be more sensitive, but also to be more specific. And these tools are, for example, tools that help us to examine the optic nerve. And the optic nerve can be examined either with MRI or with the OCT or with VEP. And this is a set of tools that we have to see if the optic nerve is affected. And we have also another sort of tools who come from the MRI, the central vein or the paramagnetic rim, which are tools that are very helpful, for example, in certain circumstances to increase the specificity of the diagnosis. And then we have other tools, new tools that come from the CSF study, which are the kappa-free light chains. And we have also another different serum biomarkers, such as the anti-MOG antibodies. So with all these tools, applying them in the different scenarios, we are able to, in certain cases, improve sensitivity, for example, looking at the optic nerve, but also in certain circumstances, increasing specificity using, for example, the central vein sign or the paramagnetic rim. So this box of tools is also very much a new concept that we have in this criteria.

Other changes that are important is, for example, that we are having only one set of criteria, since from the patients that are presymptomatic to the patients with primary progressive MS. We are not using any more different sets of criteria in patients with progressive MS. And this is very much in line with the concept that the MS is one disease. So we are using the same set of criteria for all. Another important change is that dissemination in time is not always required because we have these other tools to confirm the diagnosis. And finally, that when we are in scenarios that are more complex, such as aging population, such as people with cardiovascular diseases or with migraine, in these settings, we are going to be more strict to confirm the diagnosis. Okay. So big changes, a lot of changes, but I think with this double aim of increasing sensitivity, but also specificity.

I think it is important that we understand that these criteria have to be adapted to the place where we work. And for example, we can be in a hospital in which OCT is not available, but VEP is, or in a hospital in which, for example, we have difficulties in having our neuroradiologists tell us whether there is or there is not a central vein or a paramagnetic rim. And this is absolutely fine because you don’t have to do all these things. Only this is like options that we have and that we may adapt them to our clinical scenarios. And I always say that you can still be a perfect neurologist without having some of these tools and do your job absolutely well without applying all the tools. But these tools are important because they give a direction. If we don’t have these tools in our place, maybe this is helping us to incorporate them in the future. So it tells us where we have to aim to. But we can do perfectly our job in a fantastic way, adapting them to the resources that we have in our place. And this is absolutely fine.

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