| 幸福大叔 |
2022-07-23 13:00 |
Why helmets don't prevent concussions -- and what might头盔可以预防脑震荡吗?
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Why helmets don't prevent concussions -- and what might
1,623,687 views April 2016~~July 2022 | David Camarillo • TEDx Stanford Bioengineer
David Camarillo's research focuses on understanding and preventing traumatic brain injury.
00:00
The word concussion evokes a fear these days more so than it ever has, and I know this personally. I played 10 years of football, was struck in the head thousands of times. And I have to tell you, though, what was much worse than that was a pair of bike accidents I had where I suffered concussions, and I'm still dealing with the effects of the most recent one today as I stand in front of you.
00:27
There is a fear around concussion that does have some evidence behind it. There is information that a repeated history of concussion can lead to early dementia, such as Alzheimer's, and chronic traumatic encephalopathy. That was the subject of the Will Smith movie "Concussion." And so everybody is caught up in football and what they see in the military, but you may not know that bike riding is the leading cause of concussion for kids, sports-related concussion, that is. And so another thing that I should tell you that you may not know is that the helmets that are worn in bicycling and football and many activities, they're not designed or tested for how well they can protect your children against concussion. They're in fact designed and tested for their ability to protect against skull fracture.
01:19
And so I get this question all the time from parents, and they ask me, "Would you let your own child play football?" Or, "Should I let my child play soccer?" And I think that as a field, we're a long way from giving an answer with any kind of confidence there.
01:41
So I look at that question from a bit of a different lens, and I want to know, how can we prevent concussion? Is that even possible? And most experts think that it's not, but the work that we're doing in my lab is starting to reveal more of the details around concussion so that we can have a better understanding. The reason we're able to prevent skull fracture with helmets is because it's pretty simple. We know how it works. Concussion has been much more of a mystery.
02:12
So to give you a sense of what might be happening in a concussion, I want to show you the video here that you see when you type into Google, "What is a concussion?" The CDC website comes up, and this video essentially tells the whole story. What you see is the head moves forward, the brain lags behind, then the brain catches up and smashes into the skull. It rebounds off the skull and then proceeds to run into the other side of the skull. And what you'll notice is highlighted in this video from the CDC, which I'll note was funded by the NFL, is that the outer surface of the brain, where it was to have smashed into the skull, looks like it's been damaged or injured, so it's on the outer surface of the brain. And what I'd like to do with this video is to tell you that there are some aspects that are probably right, indicative of what the scientists think happens with concussion, but there's probably more that's wrong with this video.
03:11
So one thing that I do agree with, and I think most experts would, is that the brain does have these dynamics. It does lag behind the skull and then catch up and move back and forth and oscillate. That we think is true. However, the amount of motion you see in the brain in this video is probably not right at all. There's very little room in the cranial vault, only a few millimeters, and it's filled entirely with cerebral spinal fluid, which acts as a protective layer. And so the brain as a whole probably moves very little inside the skull.
03:44
The other problem with this video is that the brain is shown as a kind of rigid whole as it moves around, and that's not true either. Your brain is one of the softest substances in your body, and you can think of it kind of like jello. So as your head is moving back and forth, your brain is twisting and turning and contorting, and the tissue is getting stretched. And so most experts, I think, would agree that concussion is not likely to be something that's happening on this outer surface of the brain, but rather it's something that's much deeper towards the center of the brain.
04:19
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.
05:15
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.
05:41
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. So please watch this video.
06:03
Announcer: Cougars bring extra people late, but Luck has time, and Winslow is crushed. I hope he's all right.
06:11
(Audience roars)
06:18
Top of your screen, you'll see him come on just this little post route, get separation, safety. Here it comes at you in real speed. You'll hear this. The hit delivered by --
06:35
David Camarillo: Sorry, three times is probably a little excessive there. But you get the idea.
06:40
So when you look at just the film here, pretty much the only thing you can see is he got hit really hard and he was hurt. But when we extract the data out of the mouthguard that he 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.
07:23
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.
08:06
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.
08:22
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 is 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.
09:23
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.
10:00
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 of the space in the ventricles. These ventricles are much larger. And so all of this tissue near the center of the brain has died off over time. So what we're learning is indeed consistent.
10:41
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.
11:13
So how can we slow the head down?
11:18
(Laughter)
11:20
A gigantic helmet. So with more space, you have more time, and this is a bit of a joke, but some of you may have seen this. This is bubble soccer, and it's a real sport. In fact, I saw some young adults playing this sport down the street from my house the other day, and as far as I know there have been no reported concussions.
11:39
(Laughter)
11:40
But in all seriousness, this principle does work, but this has gone too far. This isn't something that's practical for bike riding or playing football. And so we are collaborating with a company in Sweden called Hövding. Some of you may have seen their work, and they're using the same principle of air to give you some extra space to prevent concussion. Kids, don't try this at home please. This stuntman does not have a helmet. He instead has a neck collar, and this neck collar has sensors in it, the same type of sensors that are in our mouthguard, and it detects when he's likely to have a fall, and there's an airbag that explodes and triggers, the same way that an airbag works in your car, essentially. And in the experiments we've done in my lab with their device, we found that it can greatly reduce the risk of concussion in some scenarios compared to a normal bicycle helmet. So it's a pretty exciting development.
12:41
But in order for us to actually realize the benefits of technology that can prevent concussion, it needs to meet regulations. That's a reality. And this device is for sale in Europe but is not for sale in the US, and probably won't be any time soon. So I wanted to tell you why. There are some good reasons and then there are some not so good reasons.
13:05
Bike helmets are federally regulated. The Consumer Product Safety Commission has been given jurisdiction to approve any bike helmet for sale, and this is the test they use. This is back to what I was telling you at the beginning about skull fracture. That's what this test is for. And that's an important thing to do. It can save your life, but it's not sufficient, I would say. So for example, one thing this test doesn't evaluate is it doesn't tell you is that airbag going to trigger at the right time and place, and not trigger when it doesn't need to? Similarly, it's not going to tell you is this helmet likely to prevent concussion or not? And if you look at football helmets, which aren't regulated, they still have a very similar test. They're not regulated by the government, anyway. They have an industry body, which is the way most industries work. But this industry body, I can tell you, has been quite resistant to updating their standards. So in my lab, we are working on not only the mechanism of concussion, but we want to understand how can we have better test standards? And we hope that the government can use this type of information to encourage innovation by letting consumers know how protected are you with a given helmet.
14:13
And I want to bring this back finally to the original question I asked, which is, would I feel comfortable letting my child play football or ride a bicycle? And this might be just a result of my own traumatic experience. I'm much more nervous about my daughter, Rose, riding a bicycle. So she's a year and a half old, and she's already, well, wants to anyway, race down the streets of San Francisco. This is the bottom of one of these streets. And so my personal goal is to -- and I believe this is possible -- is to further develop these technologies, and in fact, we're working on something in my lab in particular that really makes optimal use of the given space of a helmet. And I am confident that we will be able to, before she's ready to ride a two-wheeler, have something available that can in fact really reduce the risk of concussion and comply with regulatory bodies.
15:07
And so what I'd like to do -- and I know that this is for some of you of more immediate nature, I've got a couple years here -- is to be able to tell parents and grandparents when I'm asked, it is safe and healthy for your children to engage in these activities. And I'm very fortunate to have a wonderful team at Stanford that's working hard on this.
15:27
So I hope to come back in a few years with the final story, but for now I will tell you, please don't just be afraid when you hear the word concussion. There is hope.
15:37
Thank you.
15:39
(Applause)
Chen Wang, Translator
Diana Li, Reviewer
00:00
“脑震荡”一词从未引起过如此之大的恐慌 我自己也患过脑震荡 我曾打过十年橄榄球 数千次被球打中脑袋 但我可以告诉你 自行车事故中我遭受的脑震荡要更为严重 现如今当我站在你面前时 我还在从最近的那次脑震荡中恢复
00:27
对脑震荡的恐惧 有些是有道理的 有证据表明 反复多次脑震荡 会导致早期痴呆 比如阿耳茨海默氏病 也会导致慢性的创伤性脑病 这是威尔•史密斯主演的电影《震荡效应》的主题 几乎每个人在橄榄球比赛中 或是在部队里 都会遭受脑震荡 但你可能不知道 对孩子们而言 骑自行车才是脑震荡的主要成因 即运动相关脑震荡 我还想告诉在座各位一件事 你们或许也不知道 诸如自行车和橄榄球等运动 所规定佩戴的头盔 并不是为了防止或减轻脑震荡而设计的 事实上 此类头盔的目的在于保护头骨 预防头骨骨折
01:19
家长们总是问我这样一个问题 他们问我 “你会让你自己的小孩儿打橄榄球吗？” 或者“我应该让我小孩儿踢足球吗？” 我认为从一个学科领域的角度来讲 我们远没有信心在此回答这样一个问题
01:41
所以我从另外一个角度思考了这个问题 我想知道 我们如何预防脑震荡？ 这能做到吗？ 绝大多数专家认为不能 但我的实验室目前所从事的研究 将揭示脑震荡的更多细节 从而我们会对脑震荡有更深刻的认知 戴头盔能预防颅骨骨折的原因非常简单 我们知道这一原理 而脑震荡至今仍是未解之谜
02:12
为了让在座各位对脑震荡有更直观的了解 我要放一段影片 你可以在谷歌搜索如下字样 What is a concussion? 什么是脑震荡? 然后打开CDC（美国疾病控制与预防中心）网页 网页上的这段视频就会讲述脑震荡的成因 你可以看到：头部向前移动 脑组织移动延后 接着脑组织跟了上来也向前移 撞向颅骨 被颅骨弹回 然后向另一边颅骨撞去 CDC影片中高亮的那部分 顺带说一下 这一影片由 NFL（美国国家橄榄球联盟）资助 是脑组织的外部边缘 这部分脑组织之前曾撞向颅骨 看起来它受到了损伤 所以高亮部分是在脑组织的外部边缘 我放这段影片 是为了告诉各位 这段影片的部分内容 或许确实正确地表述了科学家对脑震荡的理解 但这段影片更多地方是错误的
03:11
其中一点我个人是同意的 我相信绝大多数专家也同意 那就是脑部确实有这样的动态 它的运动迟于颅骨 接着逐渐追赶上 并向前向后振动 这一点上我们认为它是正确的 然而 视频中所示的脑部的运动大小 可能并不准确 颅顶的空间极小 只有几微米 同时这些空间填满了脑脊液 这些脑脊液对脑部来说是一个保护层 所以说 整体来看 脑部在颅骨内的移动极为微小
03:44
视频中还有另外一个问题 视频中所示的脑部 在它移动时像是一个坚硬体 这也是错的 人类的大脑是人体上最柔软的物质之一 你可以把它想象成果冻 所以当头部前后晃动时 脑部在旋转、扭曲 部分组织会被拉抻 我认为绝大多数专家都会同意这样一个观点 脑震荡可能不是发生在 脑部的外部边缘 而是发生在脑部的深处 接近脑部中央的位置
04:19
当下 我们通过这样一个设备研究这一问题 从而试图理解脑震荡产生机制 并确定我们是否可以防治脑震荡 我们所采用的是这样一个设备 它是个牙套 它里面包含了 和手机内置传感器类似的 加速计和陀螺仪 当一个人被击中头部时 它可以以每秒钟一千次的速度 记录下头部的移动方式 这个牙套的原理在于 它固定在牙齿上 而牙齿是人体内最坚硬的物质之一 所以相当于它直接连接在颅骨上 从而可以最为精确地测算出 颅骨的运动模式 研究者们也曾试验过其他方法 比如头盔 我们也曾实验过 将传感器贴在皮肤上 但是它们移动得太多了 所以我们发现这是可以得到精确测算的 唯一可信方式
05:15
现如今我们有了这一设备 就可以不仅限于研究尸体了 因为在尸体身上对脑震荡的研究 已经近乎到达极限 我们想要进行活体实验 在哪里才可以找到一组 愿意经常出去 把头乱撞 从而患上脑震荡的志愿者呢？ 嗯 我就是其中一员 他们是你们友好的斯坦福橄榄球队
05:41
所以这就是我们的实验室 我将向各位展示 我们通过这一设备测量到的第一例脑震荡 我需要指出一点：该设备中含有陀螺仪 它可以测出头部的旋转 而绝大多数专家认为 头部的旋转或许是解释脑震荡成因的关键因素 请看这段视频
06:03
解说员：Cougars带了大批人马但是已经晚了 Luck现在有机会了 Winslow被撞了 希望他还好
06:11
（观众吼叫）
06:18
屏幕上方 你可以看到他选择了这一短程球门柱路线 被分开 安全了 现在您看到的是常速回放 你会听到 由--的这一击
06:35
抱歉 放了三次可能有点儿多 但你应该会看明白
06:40
当你看这段影片时 你可能只会看出 他被击打得很严重 他受伤了 但当我们从他戴的牙套中 提取到数据后 我们可以看到更多细节、更多信息 我们可以注意到 他的左下侧面罩被击中 所以有点违反直觉的是 他的头并没有向右移 相反 它首先向左旋转 接着颈部开始弯曲 最后这一下击打的力度才让头部向右移动 这样的左右移动是鞭打现象的一种 我们认为也许是这样的移动 造成了脑损伤
07:23
当下 这个设备仅能测量出颅骨的运动 但我们真正想知道的是 脑部内部的情形 所以我们与瑞典的Svein Kleiven团队合作 他们研发出了一种脑部有限元素模型 这是一个模拟图 模拟所用数据是刚才影片中那次受伤后 我们从牙套中得到的数据 你会看到 如我之前所述 脑部正前方左右脑交界处发生旋转、扭曲 所以这和CDC视频中所描述的并不一致 这里不同颜色所代表的是 脑组织被拉伸的程度 红色代表百分之五十 这意味着红色区域的这部分脑组织 被拉长了原来长度的50%
08:06
值得注意的是红色点状区域的分布 它们非常接近脑部中心 相对而言 和CDC影片中所示不同 脑组织外部红色区域较少
08:22
接下来 我会更详细地阐释 我们对脑震荡成因的观点 值得一提的是 我们和其他同行都观察到 如果头部被击打 并像这样旋转 更容易造成脑震荡 橄榄球等运动中这种情况（前后晃动）更为常见 但这种（左右晃动）似乎更为危险 所以这种情况中脑部发生了什么呢？ 值得注意的是 人类大脑与其他动物的并不相同 主要差异在于 我们有两块儿相当大的大脑额叶 它们是我们的右脑和左脑 这幅图中值得注意的是 左右脑中间的正下方 有一个深入脑组织的裂缝 虽然这幅图中看不到 但你得相信我 裂缝中有一层纤维化组织 它被称为脑镰 脑镰连通头部的最前方和最后方 它很硬 当你头部被击中 并左右旋转时 脑镰可以让受力迅速传至脑部中央
09:23
所以 裂缝的底部有什么？ 那里有脑部的“线路” 事实上 裂缝底部红色的那一捆“线路” 是最大的单个纤维束 也就是它连接着你们的左右脑 它被称为脑胼胝体 我们认为 这也许是脑震荡最为常见的成因 击打力向下移动 撞机脑胼胝体 导致左右脑之间的连接断裂 这样就可以脑震荡的一些症状
10:00
此外 这项发现与我之前提过的 脑震荡引起的诸如慢性创伤性脑病等 脑部疾病的症状相符 这是一个中年前橄榄球职业运动员的脑部图片 我想指出的是 如果你仔细观察脑胼胝体 我们看一下上一页的这张图片 这是一个正常脑胼胝体的大小 这是那位患有慢性创伤性脑病的脑胼胝体 它大幅萎缩了 脑室的大小也有变化 然而它们却变大很多 这意味着脑部中央附近的组织细胞 已经逐渐凋亡 这也印证了我们的研究发现
10:41
但是 这里我也要带来一些好消息 希望能给在座各位一些希望 我们注意到一些损伤机制的细节 虽然力在裂缝中的向下传导非常迅速 它还是需要一定的时间的 所以我们设想 如果能够减缓头部的向下移动 那么脑部运动就不会落后于颅骨 而是与颅骨同步 这样我们或许就能预防脑震荡
11:13
那我们该如何减缓头部的向下移动？
11:18
（笑声）
11:20
可以佩戴巨型头盔 空间变大 缓冲时间就会变长 当然这是个玩笑 虽然你们有人可能见过这个 这是泡泡足球 而且它真是一项运动 事实上 前几天 我就在我家附近的街上看到一些年轻人在玩儿它 据我所知 没有这种运动中发生脑震荡的报道
11:39
（笑声）
11:40
但严肃地说 这一原则确实有效 但它有点过头儿了 毕竟对于自行车和橄榄球运动来讲 这不大现实 目前 我们正和瑞典Hövding公司合作 研发一个产品 可能有人见过它 它实际上运用了同一项原则 利用空气提供更多空间 从而预防脑震荡 小孩子请勿在家尝试 这个特技演员没有戴头盔 而是戴了一个颈环 这个颈环内置传感器 这些传感器和我们的牙套中的传感器同属一个类型 当骑行者要摔倒时 它可以感测到 并且弹出安全气囊 这一引发机制和汽车中的基本一致 我的实验室对这一设备进行了一系列实验 我们发现与普通自行车头盔相比 这一设备在一些情境下可以大幅降低脑震荡风险 这是个很令人激动的新发展
12:41
但为了真正利用这一可以预防脑震荡的技术 它必须得符合监管的要求 这是个现实问题 这一设备目前在欧洲出售 但目前却没有 很可能近期都不会 在美国出售 我会告诉各位这是为什么 有些原因很合理 而有些却不是
13:05
自行车头盔由联邦政府监管 美国消费品安全委员会有权 批准自行车头盔产品上市 他们用这样的测试方法 这又回到了我们开始时候谈到的颅骨骨折问题 而这正是这一测试的目的 这一测试很重要 它能挽救生命 但我得说 它不够全面 比如说 这一测试没有评估 安全气囊能否在正确地时间地点弹出 也没有评估它在不需要弹出的情况是否会弹出 同样 这一测试也不能判断 这一头盔是否能够预防脑震荡 其实橄榄球头盔虽然未被联邦政府监管 但他们的测试基本相同 虽然它们并未被政府监管 但如同绝大多数行业一样 有一个行业机构负责此事 但我得说 这一机构极力反对更新它们的标准 所以我们实验室不仅研究脑震荡机制 还想研究如何才能采用更好的测试标准 我们希望政府可以利用这类信息鼓励创新 让消费者了解某一特定头盔的保护能力
14:13
最后我想要回到最初我常被问到的那个问题 我会让我的小孩打橄榄球吗？ 会让它骑自行车吗？ 因为我自己的痛苦经历 当我女儿Rose骑自行车时 我会非常紧张 她现在才一岁半 就已经很想冲下旧金山的街道 这张图片拍摄于某条街道的末尾 所以我个人的目标是进一步研发这些技术 而且我认为这一肯能行很大 事实上 我的实验室尤其致力于研究 头盔内部空间的最佳使用方式 我敢肯定我们能在我女儿可以骑两轮自行车前 做到这一点 研发出能够真正减少脑震荡风险 且符合监管机构要求的头盔
15:07
我希望再过几年 我可以告诉孩子家长和祖父母 孩子们可以安全、健康地骑自行车、打橄榄球 非常有幸我能在斯坦福有这样一个 致力于研究脑震荡的团队
15:27
我希望过几年我可以再来讲最后的故事 但现在我可以各位 当你听到脑震荡一词时不要害怕 这还有希望
15:37
谢谢各位
15:39
（掌声）
https://www.ted.com/talks/david_camarillo_why_helmets_don_t_prevent_concussions_and_what_might/transcript?referrer=playlist-how_can_we_keep_our_brains_healthy&autoplay=true
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