Defining and Assessing Cognitive Function in Multiple Sclerosis

Stephen Krieger, MD: Hi, I'm Dr. Steven Krieger, a professor of neurology at the Corrine Goldsmith Dickinson Center for Multiple Sclerosis at Mount Sinai, in New York.

I think the field of multiple sclerosis has turned its attention to cognition a lot in the last few years, and so, any conference, including the American Academy of Neurology, features a lot of new work looking at cognitive function and MS. It's worth just taking a step back and saying that for so long MS was thought of as a disease that spared cognition. And I think that really has to do with the fact that we weren't looking carefully enough for it. So one of my themes has become how can we look more carefully for the findings, the symptoms, and the signs that reflect the burden of disease? I think cognition is a perfect example of that.

Once people recognized that cognitive dysfunction was common in MS, the supposition was that it was a late phenomenon—a manifestation of late progressive MS. But that has been really changed over these last few years, as we realize there's evidence of cognitive dysfunction earlier and earlier in the disease course. The second thing that's changed is, we used to think of cognitive dysfunction in MS as purely a slowness of processing. And now, there's a really increased recognition that there are problems with language, with executive function, with multitasking, with speed—but that speed itself is really kind of a combined measure of a lot of different facets of cognitive dysfunction.

At Mount Sinai's MS center, we've had kind of a an evolving way of looking at cognitive dysfunction in MS. Some years ago, we were using one of the computerized batteries, short ways of assessing cognitive function. But since Dr. Jim Sumowski, MS, joined our program a number of years ago, he's really built out the cognitive assessment aspect of the Mount Sinai MS Center. He had done a lot of work on cognitive reserve work that he has expanded at Mount Sinai. And so what we're trying to do now is, in addition to brief screening assessments for cognitive dysfunction—which really has to do with listening carefully to what our patients are telling us—we also work to have, once a year, a more comprehensive annual assessment, which includes a more thorough battery of neuropsych evaluations.

The simplest way we assess it is through the SDMT [Symbol Digit Modalities Test]. This is really kind of a short screening tool for cognitive dysfunction. It's used in clinical trials, it can be used in practice, and it doesn't take a very long time. It used to be thought of as a measure of processing speed, but really, it's a more thoroughgoing measure of cognitive function. So, problems on the SDMT reveal that there is a cognitive complaint or a cognitive portion of someone's MS disease burden. It doesn't tell us it's specifically processing speed, but it tells us there's a problem there. That's sort of the screening test, and then one can do these annual more thorough neuropsych testing to really better characterize things like language function and memory and multitasking, which really affect people in their daily lives.

I think talking about cognition with our patients is always a little bit sensitive because people, understandably, really connect their cognitive function with their sense of identity and their abilities in the world—who they are. And so it's always sensitive. I think, more so than talking to someone about sensory symptoms, or coordination symptoms, or vision symptoms. Once we start talking about cognitive symptoms, it's a heavier topic, and I think that we as clinicians, taking care of people with MS should lean into those conversations. We should view them as an opportunity to assess things and try to make them better.

I would say that the lack of awareness of cognitive dysfunction in MS, in a sense has 2 forms. Sometimes the person with MS may not be aware of the cognitive deficit, and that can be very challenging if someone doesn't realize what the challenges are, that they're facing. But more commonly, I think our patients are aware that they struggle with cognitive function. Word finding being a typical one that we think of as potentially normal, but it can be worse than multiple sclerosis. So I think more often, the problem with awareness is that the person with MS knows that they have a cognitive problem. But the clinicians haven't assessed it, and aren't looking carefully enough at it or for it. The mandate is really on us to listen carefully to our patients concerns, try to pursue them get some baseline testing.

One of the other challenges is that, of course, people's baseline cognitive function varies enormously. And so I think it's important to begin to screen for cognitive dysfunction by assessing someone's cognitive function—their baseline, where they're coming from—because only then can you get a sense of what's changed over time. That's, really, work that Jim Sumowski, MD, has done that, I think, really changed the way our field—and certainly our center—approaches this symptom.

I think when we're looking at cognitive function and MS, one of the big questions that comes up is: What do we do about it? There, we need to look at our recent clinical trial data to get a sense as to what our modern therapeutic armamentarium can do for cognitive function and cognitive dysfunction. There are other metrics that have been used in clinical trials to assess MS cognitive function. SDMT remains, I think, the good starting point. BICAMS is another. There are other, longer assessment tools that have been used. But I think, even if someone's not using a particular test, like BICAMS, in their practice, just being able to interpret those data, to look at what constitutes stability or improvement in the clinical trials, gives us a way of looking at cognitive function on a way of explaining to our patients what we're trying to do.