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Course: Health and medicine > Unit 8
Lesson 11: Multiple sclerosisClinical progression of multiple sclerosis
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Want to join the conversation?
- Why doesn't the body react to the immune cells attacking the myelin? Shouldn't we have evolved to the point that there is some sort of a biological alarm bell that would go off when this happens?(3 votes)
- In autoimmune diseases like multiple sclerosis (MS), the reason the immune system attacks the body is due to a broken "alarm mechanism," to use your term. Every cell in the body is labeled with a protein sequence that tells the immune system that its "you" and not a pathogen. This is called a major histocompatibility complex (MHC). The way I think about MHC proteins is like a hotdog bun that the cell is holding out to the environment on its membrane. In that hotdog bun is a string of proteins that identifies the cell as "self." (The "self" hotdog!)
When a cell is infected with a virus, for example, the cell takes a small piece of that virus, and replaces the "self" protein in the MHC complex with that small piece of virus. When immune cells come in contact with cells that do not display this self protein, they attack and initiate cell death, which is beneficial in the case of a cell infected with viral proteins.
In MS, however, the immune system begins to recognize myelin and myelin producing cells as "not-self" even though they contain the "self" protein. For a reason that is not yet completely understood, be it due to a certain infection that sensitizes the immune system or complex genetic factors, the ability for the immune system to read the MHC complex proteins stops, and the immune system attacks "self" cells.
There is no real "alarm" or anti-inflammatory reaction from the immune system because it believes its doing its job. We have evolved a self-protection system via the MHC complex and the "self" protein, but this is a disease that causes derangement from that safety mechanism. This leads to progressive destruction of spinal and cerebral tracts, manifesting in the stereotypical sensory deficits seen in MS. As we learn more about MS and its pathogenesis, we may be able to elucidate a more targeted cause and approach to treatment.(9 votes)
- Is it possible to predict which type of multiple sclerosis someone has before the severity starts to change over time? Like, if a doctor knows a child has MS, will they know early-on what type they have?(4 votes)
- they cannot predict at that particular time but definitely over a period of time according to how the patient reacts they definitely can(1 vote)
- At what age do SPMS and PRMS start? And do they affect males and females equally? The video told us that about RRMS and PPMS but not the other two.(2 votes)
- I want to know about macdnold's criteria for ms?(1 vote)
Video transcript
- [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.