Strategies in Treating Relapsing-Remitting Multiple Sclerosis - Episode 3

Differentiating Between the Subtypes of MS

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An overview of the clinical subtypes of multiple sclerosis and factors that help neurologists distinguish between each type for an appropriate diagnosis.

Scott D. Newsome, DO, MSCS, FAAN: We have mentioned the clinical syndrome. Bob, take us through what the typical clinical scenarios or clinical presentations are that we put in this box and consider MS [multiple sclerosis]. What are the definitions, the prevalence, etc?

Robert Fox, MD: With all the changes in the diagnostic criteria up to and including the 2017 diagnostic criteria, we still have the same basic elements: 4 classes and a fifth. There is clinically isolated syndrome, and that is a patient who has a single clinical attack that is a demyelinating syndrome. We have relapsing/remitting MS, which is after that first attack. They might meet diagnostic criteria through a second attack, or it might be through new lesions on MRI. These are the number of ways that we have already talked about with the 2017 McDonald Diagnostic Criteria for Multiple Sclerosis that allow the diagnosis of relapsing MS.

We then have secondary progressive MS, and that is after a period of relapsing MS. Instead of or in addition to having the episodes of neurological dysfunction, patients have a gradual decline. This most commonly manifests as a decline in walking function, climbing stairs, or long-distance walking. Some patients who may be athletes and are runners will notice a foot slap or a fatigue of their legs in the later parts of their long-distance running. Whatever is the more demanding and stressful neurological requirement being for a patient: climbing stairs, carrying items, and things like that. That is the sign of the start of secondary progressive MS. Secondary progressive MS always follows relapsing MS, or the patient needs to have relapsing MS come before it. There are patients who have what looks all in the world like secondary progressive MS, but they do not seem to have any previous clinical episodes or any previous relapses. That is what we call primary progressive MS. The exact difference between secondary and primary progressive MS has been a little elusive, and over the last many years, they seem much more similar than they are different. 

There are 2 other aspects to keep in mind. One is that we have patients, even before clinically isolated syndrome, who have an MRI that looks all in the world like MS. It could have been gotten because they had migraine headaches, or they had a closed-head injury that led to the MRI. It looks all in the world like MS. It might even fulfill McDonald criteria on the MRI component, but they do not have any syndrome suggestive of MS: neither any relapses nor any progression. We say that those patients have radiologically isolated syndrome.

The other aspect that has been highlighted more recently by some of the FDA approval decisions is to differentiate progressive MS and active inflammation. For that, I point to the 2013 clinical course descriptors with the lead author, Fred Lublin, which divided MS into 2 parts or 2 aspects, and they are not mutually exclusive. Do patient have active inflammation as measured by relapses, or new active lesions on MRI? Parallel to that, do patients have progression, the gradual worsening of neurologic function independent or outside of a clinical relapse? Those are 2 characteristics that are helping us understand the different types of MS going on within a patient.

Scott D. Newsome, DO, MSCS, FAAN: Thank you for watching this Neurology Live® Peer Exchange. If you enjoyed the content, and I hope you did, please subscribe to our e-newsletters to receive upcoming Peer Exchanges and other great content right in your in-box.

Transcript Edited for Clarity