The MS diagnostic criteria are primarily important for us doctors, as they provide a kind of guide on how to assemble clinical, imaging and laboratory findings for the diagnosis of MS. However, changes to the diagnostic criteria are also of high interest to patients. Therefore, I would like to briefly summarize the most important changes here, which have not yet been published, but were presented in their basic features at this year’s ECTRIMS Congress in Copenhagen.
The new diagnostic criteria – also referred to as McDonald criteria 2024 – emphasize even more than their predecessor versions the importance of MRI imaging for diagnosis. While the clinical presentation and the differential diagnostic distinction from other diseases (“no better explanation than MS”) still play a fundamental role, a development towards a biological diagnosis of MS can be observed.
Changed criterion for RIS
In this context, one major change to the criteria should be mentioned: The so-called radiologically isolated syndrome (RIS – see also DocBlog from May 16, 2024), i.e., a typical MRI finding as in MS but without clinical symptoms, can lead to a diagnosis of MS under certain conditions and thus already be treated. This raises questions about the type and duration of possible therapy and has also already led to criticism. However, we know that a significant proportion of RIS patients are diagnosed with MS over time. The current adjustment of the diagnostic criteria therefore helps to eliminate the “limbo” associated with the diagnosis of RIS.
Expanded criteria for local dissemination
Another major change is the expansion of the criteria for so-called local dissemination to include the topography of the optic nerve (Nervus opticus). Until now, it was considered that local dissemination was proven if MRI showed involvement of two or more of the four (typical) topographic regions (periventricular, juxtacortical, infratentorial, spinal). The optic nerve is now added as the 5th (typical) topography, and its involvement can be demonstrated not only by MRI but also by visually evoked potentials (VEP) or optical coherence tomography (OCT). This adjustment will simplify the diagnosis of MS after optic neuritis, which is a common first symptom.
Changes in temporal dissemination
Changes have also been made with regard to the criterion of temporal dissemination. Already in the 2017 criteria (see DocBlog from May 18, 2018), the temporal dissemination no longer had to be demonstrated by a new MRI lesion in the follow-up imaging or the coexistence of older and newer (i.e., contrast-enhancing) lesions. The evidence of positive oligoclonal bands was sufficient to prove temporal dissemination. According to the new criteria, if there is evidence of locally distributed lesions in at least four of the five typical topographies, no further evidence of temporal dissemination is needed.
Inclusion of specific MRI findings in diagnostic criteria
Another innovation is that MS-specific MRI findings such as the so-called “central vein sign” (CSV) and the “paramagnetic rim lesion” (PRL) are integrated into the diagnostic criteria. In the event of their detection, a diagnosis of MS can then be made without higher requirements for proof of local and temporal dissemination. This development also underlines the importance of MRI imaging in the diagnosis of MS.
However, it is still unclear to what extent it will be possible to integrate the new MRI parameters into the comprehensive routine imaging of MS. Therefore, the diagnosis of MS will probably continue to be made primarily on the basis of the 2017 revision of the McDonald criteria.
In addition to the changes mentioned above, there are smaller adjustments such as equating oligoclonal bands and free kappa light chains to demonstrate chronic immune activation in the CNS, or merging the diagnostic algorithms for relapsing and primary progressive MS.
This should suffice as a brief overview of the new criteria to give an outlook on what is coming – a more detailed discussion will probably only be possible when the new diagnostic criteria are published, which is expected in spring 2025.
This post was translated from German to English with the help of AI.