In 2017, the diagnostic criteria for MS, the so-called McDonald criteria, were revised by an international panel of experts. The revision was published in Lancet Neurology at the beginning of 2018 (Thompson et al. Lancet Neurol 2018; 17: 162–73). Revision of the diagnostic criteria – that initially sounds like a significant topic. However, I believe that the actual significance of the current revision for patients is probably limited.
Most of my readers probably know that the systematics of the McDonald criteria are based on trying to demonstrate the “dissemination in space and time” typical of MS using MRI criteria, in order to be able to diagnose MS as early as possible. Early diagnosis is important because early and efficient treatment of the disease has emerged as the essential therapeutic principle in recent years.
In the current revision of the diagnostic criteria, the criteria for temporal dissemination have been particularly changed. Temporal dissemination (i.e., inflammation activity in the brain occurs at different times) can be detected with MRI by either demonstrating new lesions on a follow-up scan or showing a coexistence of fresh lesions (with contrast enhancement) and older lesions (no more contrast enhancement). According to the McDonald criteria of 2010, symptomatic contrast-enhancing lesions, i.e., lesions responsible for the current clinical symptoms, were not to be counted. I have never understood this rule and therefore completely agree with this pragmatic change.
Furthermore, another criterion was introduced concerning the proof of temporal dissemination: With the 2017 revision, the detection of oligoclonal bands in the cerebrospinal fluid can be used as evidence of a temporal dissemination of the disease. This is an interesting innovation – and a clear international signal for the importance of cerebrospinal fluid analysis.
In Germany, cerebrospinal fluid analysis has always been a standard method, which is fundamentally used for the diagnosis of MS. Therefore, German neurologists were always irritated that this important tool did not appear in the diagnostic criteria in the past (dominated by Anglo-American experts). Especially because one of the most important principles for the diagnosis of MS is that there are no other explanations for the neurological symptoms than MS, i.e., other diseases could be excluded. The cerebrospinal fluid is of great importance for this so-called “differential diagnosis”.
Thus, this innovation also leads to a gain in pragmatism in Germany. Let me give a small example: A young woman comes to the neurology department with a unilateral sensory disturbance. The MRI shows several disseminated lesions in the MRI of the brain, but none of these lesions enhance with contrast. So there is a spatial dissemination (lesions at different locations in the brain) but no temporal dissemination, because only “older lesions (=no contrast enhancement)” can be detected. According to the old McDonald criteria from 2010, no MS can be diagnosed because the temporal dissemination is missing. But the young woman has a typical inflammatory cerebrospinal fluid syndrome with the detection of oligoclonal bands – and therefore it is quite certain to assume MS and further relapses must be expected. Therefore, in the past, the somewhat unfortunate term “CIS=clinically isolated syndrome” was chosen in such a situation, indicating that although MS cannot yet be diagnosed, MS is still present. But this terminology is anything but patient-friendly – because the question “what do I actually have now” always remained.
Luckily, this is now a thing of the past. In the case mentioned above, I can diagnose MS based on the oligoclonal bands and communicate this to the patient and discuss treatment options with him. With the diagnosis, all approved medications for treatment are available (for CIS, only interferons and COP are formally approved – everything else is actually not reimbursable).
The ability to treat MS early is the reason why I find the revision of the criteria pragmatic and useful. Not everyone will share my opinion. Some will suspect that the new diagnostic criteria are solely in the interest of the industry. I do not see it that way and will write about the “Will-Rogers-Phenomenon” in one of the next blogs: A statistical problem that arises with the introduction of new criteria.
