That Neuroscience Guy - The Neuroscience of the Chiari Malformation

Episode Date: December 19, 2024

In today's episode of That Neuroscience Guy, we discuss the Chiari Malformation - a unique  condition that causes the brain to grow into the spinal cord. 

Hi, my name is Olaf Krogolson and I'm a neuroscientist at the University of Victoria. And in my spare time, I'm that neuroscience guy. Welcome to the podcast. So today I'm going to talk about something that's a rare clinical condition. It's a request from a friend of mine and I did some research on it and I found it pretty fascinating so I thought I'd just dive into it. It's called the Chiari malformation. Now what is the Chiari malformation? Basically it's a condition in which the brain tissues, your brain, extends into the spinal canal.

And specifically, we're talking about the cerebellum at the back of the head. And basically, what's happening is it's because part of the skull is misshapen typically, and that pushes on the brain and that pushes it into other parts of the brain. Now, the Chiari malformation is not very common, but because people are using imaging more, so we're using more fMRI specifically, and in this case it would be actually MRI, magnetic resonance imaging, we're finding more cases of the Chiari Malformation. Now there's a bunch of different types that occur. The Chiari malformation type one is typically seen

in younger people when the skull and the brain are still growing. It just means they're not growing correctly. And the symptoms don't really occur that early on. Kids are pretty robust to this kind of stuff. But then you have later stage Chiari malformation, which are type two and type three. They're present at birth, all right, but the symptoms may arrive later in life. They may be there from day one. Typically, the Chiari malformation is treated

with medicine, but there are surgery options. And sometimes if the symptoms are minor or it's just a deficit, you know, it's just something that's there, but it doesn't do anything, then treatment isn't needed. So I'll take a second here just to pause because I like to say this. People always assume that all our brains are the same. And it's not a great assumption to make. If you look at human beings on the outside, look at the range of heights we have, weights, hair colors, you know, skin colors, everything. We have this massive array on the outside.

Well, the same is true on the inside. I, for instance, have a hole in my brain. We have this massive array on the outside. Well, the same is true on the inside. I, for instance, have a hole in my brain. I have some missing tissue in a part of my brain. I actually don't know why it was discovered when I was an adult. So it could have been something that was there at birth. It could have been something that came about

because of an accident. Now, I've told you about this thing called the KRE malformation. Probably the best way to think about it is to, or at least to visualize what it is better, is to give you some symptoms. The classic symptom of the KRE malformation is headaches, alright? Not surprisingly, you know, if you've got your brain being squished where it's not supposed to be squished, the resulting symptom of this is headaches.

But if you have type one Chiari, you can also get neck pain. People have trouble walking or trouble with balance. Poor hand coordination because it's impacting the cerebellum. The cerebellum plays a massive role in coordination with the human body. Numbness and tingling of the hands or feet. And I will take a moment here. If you have continuous numbness and tingling of the hands or feet,

that's actually a symptom for a lot of things. And it's one that you would want to get checked out. Dizziness is something that happens with the Chiari malformation. Interestingly, just because of the way that it comes about, it can be trouble with swallowing, and then speech changes occur. Now, there are other problems that extend from the Chiari malformation. You can get tinnitus. Tinnitus is basically just a ringing or buzzing in the ears. You can get overall weakness because, again, the is basically just a ringing or buzzing in the ears. You can get overall weakness because again the cerebellum plays a massive role in motor control or motor

output. So you can actually get physical weakness. So the body is actually strong but you're not able to use that strength. It can impact your heart rhythm. Why is that? Because again you're in a midbrain region. At least there's pressure on a midbrain region. Sometimes it can actually impact the spine. That's your body trying to adapt to this additional growth. And again, it can lead to sleep apnea. I've mentioned that briefly before, but people trouble with breathing. That's type 1 Chiari malformation, which typically occurs during the growth stage. What makes type 2 Chiari type 2 is just there's even more brain tissue pushing into the spinal region.

Now with Chiari malformation type 2, it gets more serious pretty quickly. Your breathing patterns are definitely impacted at this stage. The trouble with swallowing can lead to gagging or vomiting. Eye movements are impacted because your eyes are actually not controlled directly, but part of the ocular control system is near the spinal cord. So you have downward eye movements are typical. People just look down reflexively.

And that weakness is more prominent now. And it's usually noted during pregnancy for type two. So this is something you're born with as opposed to type one, which occurs after birth. Now type three Chiari is very, very serious. This is when the cerebellum basically The type 3 Chiari is very, very serious. This is when the cerebellum basically pushes through an opening through the skull into the brain stem. So types 1 and 2 are more pressure than the cerebellum actually growing out.

In type 3 Chiari, the cerebellum is actually out of the pocket that it's supposed to be in. And this impacts the nervous system to a big deal. All right. So you're going to have all sorts of movement problems and disorders. And typically this is one where surgery would be imminent. All right. So they would operate on you. Now this is detected typically at birth or during

pregnancy via ultrasound. They can't operate before the child is born, but basically if you were diagnosed with type 3, they would see it and they would be operating right away. And sadly with type 3 Chiari, like type 1 you can generally live with and manage. Type 2, they will try to treat. Type 3 generally results in death, or at least the rate of death is quite high, unless surgery is successful. So the Chiari malformation, again, it's one of these rare things that's out there,

but there's a lot of these things. And the basic summary of this is your brain tissue is extending into the spinal canal. All right. So your brain is going where it's not supposed to be. And the skull is just, what's happening is the skull is pressing on the brain and forcing it out of location. So it's actually a bone issue it starts with because the bone is pressing in the wrong way and that impacts the brain which then impacts behavior. And again the typical part of the brain that's impacted is the cerebellum. So I thought I'd use the rest of this podcast time to talk a little bit about the cerebellum specifically. Some people call it the old brain. If you went on Google images right now

and typed in cerebellum, and I'd encourage you to do so, you're going to see the brain, and you're going to see what looks like a little brain at the back. And that's the cerebellum. The cerebellum is typically associated with motor control. All right, so the movement of the body. associated with motor control. Alright, so the movement of the body. If you went through medical school, you know, that's the story that you would be told. Alright, so they would talk about the cerebellum and they talk about coordination and movement timing.

And that is the classic role of the cerebellum. The cerebellum though does have roles other than that, okay? So typically motor control, timing, coordination are the big things. So it's when you go to move, you see it. But the cerebellum goes beyond that. It seems to play a role in our emotional system now and also in our decision-making system. And I want

to dive into that a little bit more before we wrap up in what the syrup the modern view of the cerebellum. And the reason I say the modern view is if you spoke to a doctor over let's call it the age of 35 they might not be aware of this because they would have been taught the traditional role of the of the cerebellum, which is timing and coordination in the motor system. So the modern view of the cerebellum is it's all about prediction, what we call forward control. Now, I'll use a motor example for this, and I've actually used this one in the past, but

I want to revisit it and extend this. Let's say that you're going to reach out and pick up an apple. There's an apple in front of you. So what happens is the motor system builds up a motor command which is basically the signals you're going to send to the primary motor cortex that allows the brain to move and reach a movement target. Now you execute the movement so you decide to move. It's not grip it and rip it. Like when you move like this you don't commit to the movement and just do the whole movement. What you actually do is you continuously update the motor command. You're constantly tweaking it to make sure it works. Now how do we do this Well, the old view of this is we used to rely on feedback.

We had watch our limb moving through space and we would make adjustments. We call this feedback-based control or online control. The problem with this is it's incredibly slow. So what do we actually do? The motor system and the cerebellum specifically makes a prediction, if I keep doing this, what's going to happen? And we call this the predicted state, and the predicted state in grabbing an apple should be

grabbing an apple. Now our desired state is also grabbing the apple. So the cerebellum makes this prediction, and then the motor system compares this predicted state with a desired state. motor system compares this predicted state with a desired state. And if these things match, we keep doing what we're doing. If they don't match, then we adjust the motor command. And because of this predictive control, this is how the the cerebellum now is thought to play a role in, say, coordination or movement timing. Because if you disrupt the cerebellum it can't do predictive control so your timing is off and your coordination is off. We also think this predictive control extends beyond just the motor system so our ability to make estimations and predictions about future

states of the world are thought to be tied to the cerebellum. And what's interesting is it's because of the way the neurons are actually laid out in the cerebellum, the actual physical makeup is thought to play a massive role in this predictive capability. So that's a bit on the cerebellum, and I guess what I'm trying to tell you is predictive control. When you start making estimations about the world,

it's probably your cerebellum that's playing a key role in that. And I started with the Chiari Malformation and the link is that the Chiari Malformation is typically the brain extending beyond where it's supposed to be and typically it's the cerebellum that's doing this, although not always.

So hopefully you found that interesting on the Chiari Malformation. Brad, that one's just for you. Thanks for supporting the podcast. And hopefully you found that bit on the cerebellum interesting as well. Don't forget the website, thatneuroscienceguy.com. We do have a link to our Etsy store

and we have new shirts up finally after years of talking about it. and we're looking for designs. So if you want to do us a favor and give us a Christmas present that neuroscienceguy at gmail.com if you have a t-shirt idea please email us and let us know. You can also reach us on threads or X at thatneurosciguy.com. Send in ideas for podcasts like this one that came from my friend Brad, because we want to know what you want to know about the neuroscience of everyday life. And of course the podcast itself.

Thank you so much for listening. Please subscribe if you haven't already. My name is Olav Krogolson and I'm that Neuroscience Guy. I'll see you soon for another episode of the podcast.