Clinical progression of multiple sclerosis

- [Voiceover] So multiple sclerosis is a disease of the brain where the immune system kind of comes in and attacks the brain where the myelin is, thereby disrupting all the communication that happens in the brain. Now is the immune system always just gonna be in the brain just chipping away? Well, not always, right? The way that the immune system kind of comes and goes, and the way that the brain accumulates all this damage varies from person to person. So what we're gonna do is we're gonna look at the clinical course of multiple sclerosis, and by clinical course, I mean how does the disease progress? How does it get worse? Does it ever improve or do the symp-- And when did the symptoms show up? How often do the symptoms show up? There are really four different types of MS. And each type is characterized by its own unique clinical course. So here I'm showing a graph, and on the x axis is gonna be time, alright? And this will be over the course of the entire person's lifespan, and on the y axis, we're just going to be looking at the severity of the disease. So what we're gonna do is we're gonna kind of trace the clinical course of each type of multiple sclerosis using this graph. So the first type of multiple sclerosis that I'm going to talk about is called relapsing-remitting multiple sclerosis. So let's say all of a sudden there's a huge flare up of inflammation in the brain. Okay, let's say all of a sudden a lot of immune cells come in, and they all begin to attack the brain, collectively. So when this happens, the brain will start to accumulate damage, and the severity of the disease will increase over time. And so then what happens is the immune system actually kind of stops attacking the brain, and it stops damaging all that myelin so much, and so then this leaves the brain with the ability to kind of just repair all that myelin. Alright, so the brain can actually repair itself to a limited degree. Now it's not really able to repair all the way, so you know the severity of the disease, kind of doesn't. It doesn't go all the way down to zero or down to baseline over here. And then after a certain point, you're just left with this period of stability where nothing's happening, alright? The immune system isn't coming in to attack. The brain isn't healing itself anymore. It's just nothing happening. And then the immune system comes back, and it attacks the brain some more. And then you're left with this increase in severity again. And then the immune system leaves, and then you're left with this decrease in severity, followed by another period of nothing happening. So what you can kind of see is a cycle, okay? You see a cycle, which at first the immune system attacks the brain, the symptoms flare up, and the brain collects more damage. We call this a relapse. And then you see a case where the immune system stops attacking so much, and the brain is allowed to heal itself. This is called a remission, and then you have this period of stability where nothing happens. So this is really why we call it relapsing-remitting multiple sclerosis. Now the length in which these relapses and these remissions occur really vary, so it could be anywhere between a few days to a few years. Now this is by far the most common form of MS. It affects about 80 to 85 percent of all multiple sclerosis cases. It typically affects women more than it affects men, and it usually starts pretty early in life, right? Usually when people are in their 20s. So if we take about 60 to 65 percent of all those who have relapsing-remitting MS, what we'll see is that later on in their life, these relapses and remissions will start to go away, and instead we'll just see kind of a steady progression in the severity of the disease, so we'll just see here, kind of this linear, or this steady progression of the disease. So really it's the immune system's you know, kind of just hanging around over here, so the immune system is around here, and then it starts to really just chip away at the person's brain for really, most likely, the rest of their life. And so then we can mark this over here as a progression, so when this starts to happen, we say that the person has entered secondary-progressive multiple sclerosis, and like I mentioned earlier, this usually happens in about 60 to 65 percent of the people who had relapsing-remitting multiple sclerosis. So why is it called secondary-progressive? Well it's progressive because the disease gets worse and worse steadily over time, and it's called secondary because this progressive phase happens after this relapsing and remitting phase, so we know we have a secondary-progressive MS. Is there a primary-progressive MS? Well yeah, there actually is one, and it's just simply called primary-progressive multiple sclerosis. So primary-progressive multiple sclerosis is actually pretty similar to secondary-progressive multiple sclerosis. Except instead of having these relapses and these remissions that happen early on, instead what's gonna happen is you're gonna start off with just this progressive increase, so we're just gonna see kind of a linear increase in the severity of the disease, so the brain is just steadily taking more and more damage because the immune system is kind of just sticking around and attacking it. So we have this steady increase in damage. So primary-progressive MS is actually pretty uncommon. It affects only about 10% of all the cases of MS, and because it only affects about 10% of all the cases, there aren't really that many treatment options available for it, at least not as many treatment options available for the relapsing-remitting form. And also, unlike the relapsing-remitting form, it affects men and women equally. And usually it starts a little bit later than the relapsing-remitting form. Usually about a decade later or so. In your 30s mostly. And so finally, there's actually one more form of multiple sclerosis, and it's actually the least common form of the disease, and we call it progressive-relapsing multiple sclerosis. So remember you had that relapsing-remitting form, and then you had both of those progressive forms. Progressive-relapsing multiple sclerosis really takes the worst aspects of both of those, so maybe what you'll see is maybe you'll start off having this kind of light inflammation over here, so maybe the disease will kind of start off progressively getting worse and worse. But then all of a sudden, you'll see this kind of flare up where you get a lot more immune cells that really begin to attack the brain. And when this happens, we enter a relapse. This can be followed by a remission, right? When all those immune cells start to go away, but you know, maybe there are some left over that'll continue this attack and kind of chip away at the brain. So unlike with our relapsing-remitting form right over here where it's just kind of plateaued, instead the disease will now progressively just get worse and worse, and then you may see another relapse, right followed by another remission, and then followed by, you know, more progression, so really what we're seeing is kind of a combination of all these forms of multiple sclerosis in the form of progressive-relapsing multiple sclerosis. So as I mentioned earlier, this is probably the least common form. You know it only affects about five percent of all cases. So overall, you know, I've kind of shown you four different types of multiple sclerosis, right? And it's really important to kind of be aware of these four different types because when one is trying to diagnose the disease, they really need to be aware of well which type does this person have.