Why helmets don't prevent concussions -- and what might | David Camarillo

291,826 views ・ 2016-09-29

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Please double-click on the English subtitles below to play the video.

00:12
The word concussion evokes a fear these days more so than it ever has,
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and I know this personally.
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I played 10 years of football,
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was struck in the head thousands of times.
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And I have to tell you, though, what was much worse than that
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was a pair of bike accidents I had where I suffered concussions,
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and I'm still dealing with the effects of the most recent one
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today as I stand in front of you.
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There is a fear around concussion
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that does have some evidence behind it.
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There is information that a repeated history of concussion
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can lead to early dementia, such as Alzheimer's,
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and chronic traumatic encephalopathy.
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That was the subject of the Will Smith movie "Concussion."
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And so everybody is caught up in football and what they see in the military,
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but you may not know
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that bike riding is the leading cause of concussion for kids,
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sports-related concussion, that is.
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And so another thing that I should tell you
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that you may not know
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is that the helmets that are worn in bicycling and football
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and many activities,
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they're not designed or tested
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for how well they can protect your children against concussion.
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They're in fact designed and tested
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for their ability to protect against skull fracture.
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And so I get this question all the time from parents,
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and they ask me,
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"Would you let your own child play football?"
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Or, "Should I let my child play soccer?"
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And I think that as a field,
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we're a long way from giving an answer with any kind of confidence there.
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So I look at that question from a bit of a different lens,
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and I want to know, how can we prevent concussion?
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Is that even possible?
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And most experts think that it's not,
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but the work that we're doing in my lab
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is starting to reveal more of the details around concussion
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so that we can have a better understanding.
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The reason we're able to prevent skull fracture with helmets
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is because it's pretty simple. We know how it works.
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Concussion has been much more of a mystery.
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So to give you a sense of what might be happening in a concussion,
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I want to show you the video here
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that you see when you type into Google,
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"What is a concussion?"
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The CDC website comes up,
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and this video essentially tells the whole story.
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What you see is the head moves forward,
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the brain lags behind,
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then the brain catches up
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and smashes into the skull.
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It rebounds off the skull
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and then proceeds to run into the other side of the skull.
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And what you'll notice is highlighted in this video from the CDC,
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which I'll note was funded by the NFL,
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is that the outer surface of the brain,
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where it was to have smashed into the skull,
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looks like it's been damaged or injured, so it's on the outer surface of the brain.
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And what I'd like to do with this video
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is to tell you that there are some aspects that are probably right,
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indicative of what the scientists think happens with concussion,
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but there's probably more that's wrong with this video.
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So one thing that I do agree with, and I think most experts would,
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is that the brain does have these dynamics.
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It does lag behind the skull
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and then catch up and move back and forth and oscillate.
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That we think is true.
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However, the amount of motion you see in the brain in this video
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is probably not right at all.
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There's very little room in the cranial vault,
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only a few millimeters,
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and it's filled entirely with cerebral spinal fluid,
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which acts as a protective layer.
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And so the brain as a whole probably moves very little inside the skull.
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The other problem with this video
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is that the brain is shown
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as a kind of rigid whole as it moves around,
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and that's not true either.
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Your brain is one of the softest substances in your body,
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and you can think of it kind of like jello.
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So as your head is moving back and forth,
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your brain is twisting and turning and contorting,
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and the tissue is getting stretched.
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And so most experts, I think, would agree
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that concussion is not likely to be something that's happening
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on this outer surface of the brain,
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but rather it's something that's much deeper
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towards the center of the brain.
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Now, the way that we're approaching this problem
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to try to understand the mechanisms of concussion
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and to figure out if we can prevent it
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is we are using a device like this.
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It's a mouthguard.
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It has sensors in it that are essentially the same
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that are in your cell phone:
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accelerometers, gyroscopes,
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and when someone is struck in the head,
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it can tell you how their head moved
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at a thousand samples per second.
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The principle behind the mouthguard is this:
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it fits onto your teeth.
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Your teeth are one of the hardest substances in your body.
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So it rigidly couples to your skull
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and gives you the most precise possible measurement
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of how the skull moves.
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People have tried other approaches, with helmets.
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We've looked at other sensors that go on your skin,
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and they all simply move around too much,
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and so we found that this is the only reliable way
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to take a good measurement.
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So now that we've got this device, we can go beyond studying cadavers,
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because you can only learn so much about concussion
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from studying a cadaver,
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and we want to learn and study live humans.
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So where can we find a group of willing volunteers
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to go out and smash their heads into each other on a regular basis
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and sustain concussion?
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Well, I was one of them,
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and it's your local friendly Stanford football team.
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So this is our laboratory,
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and I want to show you
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the first concussion we measured with this device.
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One of the things that I should point out is the device has this gyroscope in it,
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and that allows you to measure the rotation of the head.
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Most experts think that that's the critical factor
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that might start to tell us what is happening in concussion.
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So please watch this video.
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Announcer: Cougars bring extra people late, but Luck has time,
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and Winslow is crushed.
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I hope he's all right.
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(Audience roars)
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Top of your screen,
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you'll see him come on just this little post route,
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get separation, safety.
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Here it comes at you in real speed. You'll hear this.
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The hit delivered by --
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David Camarillo: Sorry, three times is probably a little excessive there.
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But you get the idea.
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So when you look at just the film here,
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pretty much the only thing you can see is he got hit really hard and he was hurt.
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But when we extract the data
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out of the mouthguard that he was wearing,
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we can see much more detail, much richer information.
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And one of the things that we noticed here
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is that he was struck in the lower left side of his face mask.
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And so that did something first that was a little counterintuitive.
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His head did not move to the right.
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In fact, it rotated first to the left.
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Then as the neck began to compress,
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the force of the blow caused it to whip back to the right.
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So this left-right motion was sort of a whiplash-type phenomenon,
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and we think that is probably what led to the brain injury.
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Now, this device is only limited in such that it can measure the skull motion,
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but what we really want to know is what's happening inside of the brain.
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So we collaborate with Svein Kleiven's group in Sweden.
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They've developed a finite element model of the brain.
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And so this is a simulation
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using the data from our mouthguard from the injury I just showed you,
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and what you see is the brain --
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this is a cross-section right in the front
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of the brain twisting and contorting as I mentioned.
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So you can see this doesn't look a lot like the CDC video.
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Now, the colors that you're looking at
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are how much the brain tissue is being stretched.
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And so the red is 50 percent.
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That means the brain has been stretched to 50 percent of its original length,
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the tissue in that particular area.
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And the main thing I want to draw your attention to is this red spot.
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So the red spot is very close to the center of the brain,
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and relatively speaking,
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you don't see a lot of colors like that on the exterior surface
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as the CDC video showed.
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Now, to explain a little more detail
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about how we think concussion might be happening,
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one thing I should mention
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is that we and others have observed that a concussion is more likely
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when you're struck and your head rotates in this direction.
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This is more common in sports like football,
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but this seems to be more dangerous. So what might be happening there?
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Well, one thing that you'll notice in the human brain
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that is different than other animals
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is we have these two very large lobes.
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We have the right brain and the left brain.
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And the key thing to notice in this figure here
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is that right down the center of the right brain and the left brain
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there's a large fissure that goes deep into the brain.
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And in that fissure, what you can't see in this image,
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you'll have to trust me,
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there is a fibrous sheet of tissue.
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It's called the falx,
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and it runs from the front of your head all the way to the back of your head,
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and it's quite stiff.
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And so what that allows for is when you're struck
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and your head rotates in this left-right direction,
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forces can rapidly transmit right down to the center of your brain.
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Now, what's there at the bottom of this fissure?
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It's the wiring of your brain,
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and in fact this red bundle here at the bottom of that fissure
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is the single largest fiber bundle
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that is the wiring that connects the right and left sides of your brain.
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It's called the corpus callosum.
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And we think that this might be
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one of the most common mechanisms of concussion,
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and as the forces move down, they strike the corpus callosum,
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it causes a dissociation between your right and your left brain
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and could explain some of the symptoms of concussion.
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This finding is also consistent of what we've seen
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in this brain disease that I mentioned, chronic traumatic encephalopathy.
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So this is an image of a middle-aged ex-professional football player,
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and the thing that I want to point out is if you look at the corpus callosum,
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and I'll page back here so you can see the size of a normal corpus callosum
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and the size of the person here who has chronic traumatic encephalopathy,
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it is greatly atrophied.
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And the same goes for all of the space in the ventricles.
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These ventricles are much larger.
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And so all of this tissue near the center of the brain
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has died off over time.
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So what we're learning is indeed consistent.
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Now, there is some good news here,
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and I hope to give you a sense of hope by the end of this talk.
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One of the things that we've noticed,
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specifically about this mechanism of injury,
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is although there's a rapid transmission of the forces down this fissure,
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it still takes a defined amount of time.
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And what we think is that if we can slow the head down just enough
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so that the brain does not lag behind the skull
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but instead it moves in synchrony with the skull,
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then we might be able to prevent this mechanism of concussion.
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So how can we slow the head down?
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(Laughter)
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A gigantic helmet.
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So with more space, you have more time,
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and this is a bit of a joke, but some of you may have seen this.
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This is bubble soccer, and it's a real sport.
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In fact, I saw some young adults
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playing this sport down the street from my house the other day,
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and as far as I know there have been no reported concussions.
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(Laughter)
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But in all seriousness, this principle does work,
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but this has gone too far.
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This isn't something that's practical for bike riding or playing football.
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And so we are collaborating with a company in Sweden called Hövding.
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Some of you may have seen their work,
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and they're using the same principle of air to give you some extra space
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to prevent concussion.
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Kids, don't try this at home please.
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This stuntman does not have a helmet.
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He instead has a neck collar,
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and this neck collar has sensors in it,
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the same type of sensors that are in our mouthguard,
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and it detects when he's likely to have a fall,
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and there's an airbag that explodes and triggers,
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the same way that an airbag works in your car, essentially.
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And in the experiments we've done in my lab with their device,
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we found that it can greatly reduce the risk of concussion in some scenarios
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compared to a normal bicycle helmet.
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So it's a pretty exciting development.
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But in order for us to actually realize the benefits of technology
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that can prevent concussion,
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it needs to meet regulations.
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That's a reality.
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And this device is for sale in Europe
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but is not for sale in the US, and probably won't be any time soon.
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So I wanted to tell you why.
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There are some good reasons and then there are some not so good reasons.
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Bike helmets are federally regulated.
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The Consumer Product Safety Commission has been given jurisdiction
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to approve any bike helmet for sale,
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and this is the test they use.
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This is back to what I was telling you at the beginning about skull fracture.
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That's what this test is for.
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And that's an important thing to do.
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It can save your life, but it's not sufficient, I would say.
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So for example, one thing this test doesn't evaluate
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is it doesn't tell you is that airbag going to trigger
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at the right time and place, and not trigger when it doesn't need to?
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Similarly, it's not going to tell you
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is this helmet likely to prevent concussion or not?
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And if you look at football helmets, which aren't regulated,
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they still have a very similar test.
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They're not regulated by the government, anyway.
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They have an industry body, which is the way most industries work.
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But this industry body, I can tell you, has been quite resistant
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to updating their standards.
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So in my lab, we are working on not only the mechanism of concussion,
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but we want to understand how can we have better test standards?
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And we hope that the government can use this type of information
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to encourage innovation
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by letting consumers know
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how protected are you with a given helmet.
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And I want to bring this back finally to the original question I asked,
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which is, would I feel comfortable letting my child play football
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or ride a bicycle?
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And this might be just a result of my own traumatic experience.
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I'm much more nervous about my daughter, Rose, riding a bicycle.
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So she's a year and a half old,
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and she's already, well, wants to anyway, race down the streets of San Francisco.
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This is the bottom of one of these streets.
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And so my personal goal is to -- and I believe this is possible --
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is to further develop these technologies,
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and in fact, we're working on something in my lab in particular
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that really makes optimal use of the given space of a helmet.
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And I am confident that we will be able to,
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before she's ready to ride a two-wheeler,
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have something available
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that can in fact really reduce the risk of concussion
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and comply with regulatory bodies.
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And so what I'd like to do --
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and I know that this is for some of you of more immediate nature,
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I've got a couple years here --
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is to be able to tell parents and grandparents when I'm asked,
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it is safe and healthy for your children to engage in these activities.
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And I'm very fortunate to have a wonderful team at Stanford
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that's working hard on this.
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So I hope to come back in a few years with the final story,
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but for now I will tell you,
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please don't just be afraid when you hear the word concussion.
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There is hope.
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Thank you.
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(Applause)
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