Now, the way that we’re approaching this problem to try to understand the mechanisms of concussion and to figure out if we can prevent it is, we are using a device like this. It’s a mouthguard. It has sensors in it that are essentially the same that are in your cell phone: accelerometers, gyroscopes, and when someone is struck in the head, it can tell you how their head moved at a thousand samples per second. The principle behind the mouthguard is this: it fits onto your teeth. Your teeth are one of the hardest substances in your body.
So, it rigidly couples to your skull and gives you the most precise possible measurement of how the skull moves. People have tried other approaches, with helmets. We’ve looked at other sensors that go on your skin, and they all simply move around too much, and so we found that this is the only reliable way to take a good measurement. So now that we’ve got this device, we can go beyond studying cadavers, because you can only learn so much about concussion from studying a cadaver, and we want to learn and study live humans. So where can we find a group of willing volunteers to go out and smash their heads into each other on a regular basis and sustain concussion? Well, I was one of them, and it’s your local friendly Stanford football team. So, this is our laboratory, and I want to show you the first concussion we measured with this device.
One of the things that I should point out is the device has this gyroscope in it, and that allows you to measure the rotation of the head. Most experts think that that’s the critical factor that might start to tell us what is happening in concussion.
But when we extract the data out of the mouthguard that a person was wearing, we can see much more detail, much richer information. And one of the things that we noticed here is that he was struck in the lower left side of his face mask. And so that did something first that was a little counterintuitive. His head did not move to the right. In fact, it rotated first to the left. Then as the neck began to compress, the force of the blow caused it to whip back to the right, so this left-right motion was sort of a whiplash type phenomenon and we think that is probably what led to the brain injury. Now, this device is only limited in such that it can measure the skull motion, but what we really want to know is what’s happening inside of the brain.
So, we collaborate with Svein Kleiven’s group in Sweden. They’ve developed a finite element model of the brain. And so this is a simulation using the data from our mouthguard from the injury I just showed you, and what you see is the brain — this is a cross-section right in the front of the brain twisting and contorting as I mentioned. So, you can see this doesn’t look a lot like the CDC video. Now, the colors that you’re looking at are how much the brain tissue is being stretched, and so the red is 50 percent.
That means the brain has been stretched to 50 percent of its original length, the tissue in that particular area. And the main thing I want to draw your attention to is this red spot. So, the red spot is very close to the center of the brain, and relatively speaking, you don’t see a lot of colors like that on the exterior surface as the CDC video showed. Now, to explain a little more detail about how we think concussion might be happening, one thing I should mention is that we and others have observed that a concussion is more likely when you’re struck, and your head rotates in this direction. This is more common in sports like football, but this seems to be more dangerous. So, what might be happening there? Well, one thing that you’ll notice in the human brain that is different than other animals are we have these two very large lobes. We have the right brain and the left brain. And the key thing to notice in this figure here is that right down the center of the right brain and the left brain there’s a large fissure that goes deep into the brain.
And in that fissure, what you can’t see in this image, you’ll have to trust me, there is a fibrous sheet of tissue. It’s called the falx, and it runs from the front of your head all the way to the back of your head, and it’s quite stiff. And so, what that allows for is when you’re struck and your head rotates in this left-right direction, forces can rapidly transmit right down to the center of your brain.
Now, what’s there at the bottom of this fissure? It’s the wiring of your brain, and in fact this red bundle here at the bottom of that fissure is the single largest fiber bundle that is the wiring that connects the right and left sides of your brain. It’s called the corpus callosum, and we think that this might be one of the most common mechanisms of concussion, and as the forces move down, they strike the corpus callosum, it causes a dissociation between your right and your left brain and could explain some of the symptoms of concussion. This finding is also consistent of what we’ve seen in this brain disease that I mentioned, chronic traumatic encephalopathy.
So this is an image of a middle-aged ex-professional football player, and the thing that I want to point out is if you look at the corpus callosum, and I’ll page back here so you can see the size of a normal corpus callosum and the size of the person here who has chronic traumatic encephalopathy, it is greatly atrophied. And the same goes for all the space in the ventricles. These ventricles are much larger. And so, all this tissue near the center of the brain has died off over time. So, what we’re learning is indeed consistent. Now, there is some good news here, and I hope to give you a sense of hope by the end of this talk.
One of the things that we’ve noticed, specifically about this mechanism of injury, is although there’s a rapid transmission of the forces down this fissure, it still takes a defined amount of time, and what we think is that if we can slow the head down just enough so that the brain does not lag behind the skull but instead it moves in synchrony with the skull, then we might be able to prevent this mechanism of concussion.
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