This month Aaron is talking to Dr. Tom McAllister, the Albert Eugene Sterne Professor and Chairman, Indiana University School of Medicine Department of Psychiatry. He specializes in studying brain injuries and chronic traumatic encephalopathy, and he'll tell about brain injuries, their treatment, and some of the advances in detecting such injuries.
The Healthcare Triage podcast is sponsored by Indiana University School of Medicine whose mission is to advance health in the state of Indiana and beyond by promoting innovation and excellence in education, research and patient care.
IU School of Medicine is leading Indiana University's first grand challenge, the Precision Health Initiative, with bold goals to cure multiple myeloma, triple negative breast cancer and childhood sarcoma and prevent type 2 diabetes and Alzheimer's disease.
Dr. Aaron Carroll: Hi, welcome back to the Healthcare Triage podcast. I'm your host, Aaron Carroll. And today our guest is Tom McAllister, the Albert Stern Professor and Chair of the Department of Psychiatry at Indiana University School of Medicine. The Healthcare Triage podcast is sponsored by Indiana University School of Medicine, whose mission is to advance health in the state of Indiana and beyond by promoting innovation and excellence in education research and patient care.
IU School of Medicine is leading Indiana University's first grand challenge to precision health initiative with bold goals to cure multiple myeloma, triple negative breast cancer and childhood sarcoma and prevent Type 2 diabetes and Alzheimer's disease. Today, we're going to be talking about traumatic brain injury. What is it? What can we do about it? How can we prevent it?
Thanks for joining us, Tom.
Dr. Tom McAllister: Thank you, Aaron.
Dr. Aaron Carroll: I'd like to start these conversations by asking how you got here. How did you decide you wanted to get into psychiatry? What was your training? How did you get into traumatic brain injury?
Dr. Tom McAllister: Great. Yeah. Well, the one thing I knew when I went to medical school that I was not going to be was a psychiatrist. So you should take everything I say with a grain of salt from here on in. But it turns out that I became fascinated with brain behavioral relationships. If you injure the brain, or if you have a disease in a particular part of the brain, how does that then influence mood, emotions and behavior in general? And it sucked me in and I ended up going into psychiatry and in particular field of psychiatry called neuro psychiatry.
Dr. Aaron Carroll: So where did you go to medical school?
Dr. Tom McAllister: I went to Dartmouth Medical School and I was ambivalent about being in psychiatry. So I did a year of internal medicine and then trained at Dartmouth in psychiatry.
Dr. Aaron Carroll: So how did you get into traumatic brain injury?
Dr. Tom McAllister: Well, this may seem like a recurrent theme, but I knew I was never going to take care of people with brain injury. I had jobs calling saying, we really need somebody to help us care for the behavioral disturbances that often are associated with brain injury. And I said, no, thanks. And then one time in Philadelphia during my Philadelphia phase, somebody called up and said, are you the organic psychiatrist? And I said, well, as far as I know.
And it turned out that at that point in time, there was a lot of effort to bring people with brain injury who were young when they were injured, and were living with profound array of neuropsychiatric problems. And nobody knew how to take care of them. They were in institutions and so forth. So somebody was trying to bring them out into the community and needed some help. And I said, sure, and have been working in the field of brain injury for the last 30 years.
Dr. Aaron Carroll: So when we talk about traumatic brain injury, does that mean any injury to the brain or is it mostly blunt or can it be a gunshot or is it just not matter?
Dr. Tom McAllister: Well, it does matter from a couple of perspectives, but strictly speaking, there are a couple of broad division points. One is it has to be an entry that results from some kind of biomechanical force on the brain. It could be a penetrating injury from a bullet, for example, or it could be a blunt injury, for example, your head hitting the windshield, or you stumble and fall and you hit your head on the floor. But there has to be some kind of force acting on the brain that results in disruption of neurological function.
This separates it, therefore, from other kinds of injuries, such as a stroke or conditions that people might be born with that result in intellectual disability and so forth. So it has to be an acquired injury, but it has to be acquired by dent of biomechanical force on the brain.
Dr. Aaron Carroll: How common is it?
Dr. Tom McAllister: It's really common. If you look at the burden of neurological disorders in the country, it probably ranks first or second in terms of numbers. Some estimates put it that about 1% of the population are living with some form of brain injury or TBI, traumatic brain injury-related disability.
Dr. Aaron Carroll: What causes it most of the time? Has that changed over time?
Dr. Tom McAllister: It has changed over time. So back when I was turning down jobs in brain injury, the most common cause were motor vehicle accidents. And typically it was in people in their second and third decade, the folks that were beginning to drive, were not particularly good at it or using alcohol often, at the same time feeling they were immortal. And this was before seatbelt laws and airbags. So that was the most common cause back in the '60s, '70s and '80s. Right now the most common cause is falls, and not just in the elderly, although that's driving a lot of it.
Dr. Aaron Carroll: So, have the demographics changed? Is it more that you see it much more in the elderly now than it used to be?
Dr. Tom McAllister: We still continue to see it across the lifespan, but in terms of what is the most common cause of it, it is false. But there are peaks. So there's a peak in very young people and then a peak in the elderly, but there's still this bump in the second and third decade related to motor vehicle accidents.
Dr. Aaron Carroll: So, have there been any changes with respect to how we diagnose it, with respect to imaging or anything else that have changed over time?
Dr. Tom McAllister: There have, actually, and these are some of the more exciting areas in the field at this point in time. And it takes a couple of different forms to date. Brain injury, especially on the mild brain injury side or concussion, has been a clinical diagnosis, it remains a clinical diagnosis. So you have to have some sort of plausible force that is acting on the brain, such as hitting your head in a football game or whatever. And then you have to have an alteration in the level of consciousness manifested by incomplete memory or being tased and confused and so forth.
One of the big areas of interest is in neuroimaging. So at this point in time, the most common imaging study in people with brain injury remains a CAT scan or a computed nextel tomography scan, because it's really good at showing if there's accumulation of blood or if somebody needs a neurosurgical procedure. It's not so good at revealing very subtle, very tiny areas of hemorrhage or a neuronal injury.
So MRI magnetic resonance imaging is a better tool for that. It's more expensive. It takes longer to acquire the image. But there are now new signal acquisition techniques, meaning ways of taking the image that can reveal these subtle changes that we talked about in the fibers that connect one nerve cell to another, so-called white matter imaging or diffusion imaging. And in some work that is coming out of this care study, our imaging group has been able to show that there are subtle changes in white matter that persist beyond the point in time when athletes report that they are asymptomatic or that they've fully recovered. So that's not necessarily a diagnosis, although it could be used that way, but it's also in treatment and recovery monitoring.
The other big area's in so-called fluid biomarkers where traumas are associated with the release of certain proteins and other compounds into the bloodstream. And we are in the process of taking a look at a large sample of our concussed athletes from this study. And it shows very, very promising separation in certain of these biomarkers, between people who are concussed, people who are teammates, who are hitting their head on a regular basis but not concussed, and people who are playing golf or swimmers, who aren't hitting their head on a regular basis.
So I think if you look a year or two down the road, I think we will probably have a panel of blood tests that we can do that, with fairly good accuracy, will at least help confirm and strengthen the diagnostic impression, if not actually be a standalone kind of a diagnostic marker for concussion. The next challenge will then be developing a point of service machine that could do that on the sideline, for example, or in the theater of war so that people could know right away.
Dr. Aaron Carroll: So given that most of it is blunt, can you talk a little bit about the mechanism, about what happens to the brain when such injuries occur?
Dr. Tom McAllister: We generally talk about two different broad types. One is in impact or contact mechanism in which something impacts or contacts the brain resulting in damage from that. And the other is more of an inertial kind of entry in which damage is inflicted on the brain by dent of a very rapid change in the momentum or motion of the brain, either an acceleration of the brain. So think about standing still and somebody comes up behind you and whacks you with a baseball bat or something. Your head is going from zero to whatever speed very rapidly, and/or a deceleration kind of event in which you're driving down the interstate at 70, and you hit the person in front of you and your head hits the windshield and you're decelerating from 70 miles an hour to nothing over the course of milliseconds.
And then associated with the conflicts in Iraq and Afghanistan over the last couple of decades, there's been a lot more attention focused on blast injury as a potential other kind of a way of damaging the brain.
Dr. Aaron Carroll: Is it that we're actually smacking the gray matter or the white matter of the brain? Or is it that there's a disruption of the blood flow or is it something else entirely?
Dr. Tom McAllister: Yes. It's all of those. But basically if you think about, or can imagine the brain floating essentially in spinal fluid and partially tethered by the spinal cord, and now set the body in motion, what's happening is that the brain is essentially sloshing around in this bath of spinal fluid and is moving out of phase with the skull. And it turns out that the inside of the skull is not completely smooth. It has bumps, ridges, points of contact with the brain. And it's great for protecting things from the outside. But when you set the brain in motion or the head in motion, it becomes a sort of hostile work environment for the brain to live in. And there are particular parts of the brain which are then bumping up against the inside of the skull.
And what happens is that those particular brain regions are extremely vulnerable to contusions or bruising and bleeding in those areas. And then in addition, the motion and the out of phase motion of the brain with the skull sets up twisting and stretching and forces on the fibers of the neurons, which rips them, or can stretch them in a way that renders them dysfunctional. So if you think about a slinky, for example, many people are familiar with a slinky, that you can bend those things to a certain point, and then all of a sudden they're not going to work the way they're supposed to.
Dr. Aaron Carroll: That's interesting. First of all, it strikes me that I never really thought about this way, but I guess from an evolutionary standpoint, we were never meant to go that fast. Dr. Tom McAllister: We were not.
Dr. Aaron Carroll: Yeah. And so we're just not prepared for the sudden acceleration or deceleration.
Dr. Tom McAllister: Correct.
Dr. Aaron Carroll: So what can we do about that? If this damage occurs, what do you do?
Dr. Tom McAllister: That's the 64-whatever million dollar question at this point in time. I think there are a couple things to recognize. One is that, I mentioned that there're particular brain regions that are vulnerable to these biomechanical forces and a typical injury such as we're talking about. And it turns out that there're the under surfaces of the front part of the brain and the temporal lobes, which are below the temporal bone, and then the white matter fibers which connect these different brain regions.
And if you were to draw a map of those brain regions and overlay it on the brain regions which modulate mood emotions, impulse control, judgment, executive functions, memory, and a variety of other cognitive functions, you really couldn't make a more careful overlapping Venn diagram. And so this is an injury that is the perfect storm from the standpoint of inflicting damage to what we usually think of as the essence of being human, so our ability to plan, to make judgments, to modulate our impulses and so forth.
And fundamentally that's what happened when I began working with folks with brain injury. This is a form of acquired psychiatric illness, essentially. So the relative risk of depression goes way up, the relative risk of developing an anxiety disorder goes up. So it's essentially getting at all that we view as being part of a complex organism with all the capacities that humans have.
Dr. Aaron Carroll: Can we do anything about it?
Dr. Tom McAllister: Yes, with a qualification that you can probably hear in my voice. We've spent millions and millions of dollars trying to mitigate the downstream effects of that initial entry with so-called neuroprotective trials, medicines, and agents, or interventions such as cooling of the brain and so forth, which are designed to stop the damage from evolving once you have the impact of the brain, on the skull or whatever it hits.
So that's one strategy. Let's stipulate that the brain is going to get injured, but let's try and prevent the evolution of the damage that occurs over hours or days subsequent to them.
Dr. Aaron Carroll: So I imagine you have to get to somebody reasonably quickly, though, as soon as injury occurs to try any of that?
Dr. Tom McAllister: Exactly. And sadly, every single one of the neuroprotective agent trials over the last probably three decades have failed despite elegant, elegant evidence that they should work in animal models. And it's in part because there's this cascade of events that I'm talking about as the celebrity choreographed, multi-system kind of evolution that you just can't fix a single part of it. It's like putting up an umbrella in a hurricane.
Dr. Aaron Carroll: Okay. Given that, that doesn't work, do we have other options?
Dr. Tom McAllister: Let's just back up a second and say, really the best option is to prevent the injury-
Dr. Aaron Carroll: I was going to get to that. I was going to get there.
Dr. Tom McAllister: So, we can return to that, but let's stipulate again for the moment that somebody gets injured. So then there's aggressive rehabilitation that can work with people to regain a lot of the function that they may have temporarily lost, so learning to speak again, learning to walk again. What's more challenging, and what is often the most problematic concern for both people with brain injury and the folks that take care of them, their family, caregivers, or loved ones, is this assault on who they were, their essence, their personality. So we very commonly hear, this is not the person I married, or this is not my son or daughter. This is somebody completely different. And at its essence, these are dysexecutive syndromes that have been brought about by where in the brain the damage is likely to occur.
Dr. Aaron Carroll: Do the people themselves feel like they're not the same person or it's just other people around them feel that way?
Dr. Tom McAllister: It's a great question. So a lot of this depends on the severity of the injury. So at the milder end to brain injury, people often do have an awareness in it, sometimes an acute awareness that they're not quite functioning the way they used to, and it can be enormously frustrating and challenging. At the more severe ends of the spectrum, there is often damage to the part of the brain, as we've been talking about, that allows people to be aware of their behavior in a social context and aware of what the social norms are, and it's as if they're blind to them. And so it's very common to see people who are quite unaware of their behavior and how it differs from how they used to be and how it differs from social norms or what people expect in a given context.
Dr. Aaron Carroll: So given all this difficulty, it does seem like prevention is the best thing that we can do. So what are the major things we do to help prevent this from happening?
Dr. Tom McAllister: Well, I mentioned at the outset that back a couple of decades ago, the most common causes of brain injury were motor vehicle accidents and crashes. And so once seatbelt laws were put into effect and airbags were developed and use was widespread, that resulted in a pretty dramatic improvement, both in terms of reduction in frequency and also a reduction in severity. Driving under the influence is obviously a huge contributor to motor vehicle accidents. Another major in all these things, and it's not going to be of any surprise to people who are listening, assaults are a huge problem, particularly in certain areas, and falls. So anything that we can do to mitigate or prevent reduce the risk of falls, that's a huge issue.
Dr. Aaron Carroll: So I imagine in some of those areas, we have made great strides and in others probably not so much. So where's the focus mostly these days?
Dr. Tom McAllister: So, the focus these days actually is on preventable causes of entry. And one of the major focus really is on sport-related concussion. So basically if you think about it, some of the activities that we engage in, football being an example is associated with a context in which there's a lot of repetitive head impacts, some of which can result in a concussion and so forth.
Dr. Aaron Carroll: So as a pediatrician, this is the one that's constantly shoved in front of my face, and that we're talking about all the time, especially with ideas of, should we let kids participate in these sports because... Why is it all of a sudden that, it feels like all of a sudden I should say this, this has entered our national consciousness? A lot of these sports have been going on for quite some time.
Dr. Tom McAllister: Yes, they have and it's a great question. And I would point to a couple of different issues which brought this into focus for the last, it's really been about 15 or 20 years. Back when I started in this area, reluctantly, as I mentioned before, I began a clinic for people with a brain injury and ended up seeing a lot of folks with so-called myeobrain injury, which is synonymous in my mind with concussion. So I'm going to use the terms interchangeably, but it's a mild traumatic brain injury. And I thought that this was a horrible, horrible condition because I was being referred only those people who don't get better. And so it was a sampling bias.
But, nevertheless, I had to convince people that sometimes people don't have a good outcome after a seemingly mild brain injury. And then with the emergence of the war on terrorism and the appreciation that our military personnel were being exposed to increasing numbers of blast forces... And it's important to point out that while the blast wave can damage the brain in and of itself, it's usually associated with a [inaudible 00:20:32] accident or being blown up and colliding with a wall or hitting the ground or whatever. So it's typically a combination of blast forces and impact and inertial forces.
And there were a group of people who were psychiatrists, neurologist, physical medicine folks, and others who became aware that many of the military personnel were beginning to report signs and symptoms consistent with mild brain injury. So the Department of Defense ended up, as most people are aware, naming brain injury or referring to it as the signature wound of the war, wars in Iraq and Afghanistan. That called a huge amount of attention to it. It created a huge funding stream through the Department of Defense to study this. If you look at the growth curve of papers published on traumatic brain injury over the last 20 years, there's an exponential rise. I used to be able to do a PubMed search and complete it in about five minutes and now it's not so much.
So that was one. Then in 2003 Bennet Omalu and colleagues published a paper on something called chronic traumatic encephalopathy in an NFL football player who had killed himself. And this brought attention in a fairly stark way and surprising way to the potential risks of repetitive head impacts and repetitive concussions. Now it turns out we had known about this for a long time. So the original work on this was published by Martin Lin back in the 1920s. And it was in professional boxers who, not surprisingly, had multiple concussions and multiple head impacts.
They described a similar neuropathology in this football player, and subsequently went on to summarize similar findings in a variety of other retired professional athletes in other contexts, including interestingly, some military personnel who had been exposed to multiple blast events during the war.
So the confluence of a high profile war on terror, and the fact that brain injury was a huge component of the burden of morbidity associated with the conflicts, and high profile papers dealing with CTE or chronic traumatic encephalopathy in retired athletes brought it into focus. The other point is that a lot of the soldiers in OEF and OIF were protected by body armor that we didn't use to have to that extent. And so they were living now, but they were living with the sequelae of brain injury, which the body armor doesn't really protect.
Dr. Aaron Carroll: That's really interesting. But if we're focus on sports for a minute, we keep hearing about NFL athletes especially having this, and it's interesting because I'll read something in the news and it'll seem like it's a crisis, and then it feels like it goes away, and then it comes back and that's a crisis, and then it goes away. Is there a sense of how real or how prevalent this is in NFL players or just pro sports players in general?
Dr. Tom McAllister: This is a subject of huge controversy. And basically the way this story is evolving is that it seems clear that, in the same way that it was fairly clear in boxers, that there are a group of folks who are exposed to either repetitive concussions or repetitive head impacts, or both most commonly, for whom that exposure is associated with the development of this neurodegenerative condition that we're labeling chronic traumatic encephalopathy or CTE. The problem that we have to date is that we don't know what the denominator is. So as you pointed out, people have been playing football for over a hundred years at an organized level. We, to our knowledge, don't have an epidemic of chronic traumatic encephalopathy. Number one.
Number two, the data that has been published so far is based on the brains of NFL players and other folks with other kinds of collision sport activities or military exposures in which their families were motivated to donate the brain or the players and the people themselves were motivated to donate the brain because they were convinced that they were not who they used to be, that they were undergoing these changes.
So it's a very selected sample. It's not a random sample, and we don't really know what... We're not seeing all the brains of the people who don't fall into that category. There was an interesting follow-on... Let me back up, sorry, a couple of years ago, or maybe it was just last year and Mickey's group at Boston University published a study in which they said 110 out of 111 brains of NFL players had chronic traumatic encephalopathy. And that made a big splash, it appeared in the New York times as well. And they made the point that this was a selected sample. We still don't know what the true prevalence is.
So another group of investigators said, well, we could probably figure out. So the brains were collected over an eight-year period. And they went to the NFL Players Association and figured out all the NFL players who had died over that same period of time. And it turns out it was about 1100. So if everybody who had CTE ended up in Mickey's group, then the rate would be about 10%.
Dr. Aaron Carroll: That's still seems high.
Dr. Tom McAllister: Well, so if only half of the people that have CTE ended up donating their brains, then we're getting up around 25, 30, 40% of folks, but it's not everyone. And the narrative-
Dr. Aaron Carroll: Right. That's true.
Dr. Tom McAllister: ... in the lay press is that a single concussion may be sending you down the path to CTE. And we don't know that. And in fact, there have been statements made comparing, letting your child play football to a form of child abuse, because we're so certain that it's going to develop, then it's going to be associated with CT. We just don't know that.
Dr. Aaron Carroll: That is partially what it is. I've read, and again, this is Les Aaron compared to everything else, but, of course, football players in the NFL are going to be striking each other with a lot more force in general than pee wee football is going to have. But of course, we're all rolling dice with all kinds of things that we do, but we have no evidence at this time questioning this, that their playing football at lower levels leads to this. The evidence we have at this point is from NFL players. Is that correct?
Dr. Tom McAllister: Not entirely correct. So there have been some reports of people who meet the criteria for CTE. And I should point out that this condition remains a neuropathological diagnosis, meaning that you can't make a definitive diagnosis until the person has passed away and the brain is autopsied. And it wasn't until either 2016 or 2017 when the NIH convened a consensus conference, that the neuro pathologist could agree on what the criteria were and how much slicing and dicing of the brain you needed to do in order to rule it in or rule it out.
So that said, there have been reports of, for example, college football players who did not report any concussion by history. One of whom who committed suicide came to autopsy and was found to have the hallmarks of CTE. Others from different groups have done neuropathological diagnosis on a series of brains and found people who met the criteria for CTE who had no history of trauma. So this is not an area that we have all the answers to.
There also have been quite a few reports of folks exposed to these blasts concussive force and other kinds of brain entering the military. At last report, my understanding is that about somewhere around 60% of the brains, again, that were collected by a particular group with this kind of exposure, had findings suggestive of CTE.
So I think there's reason to be concerned. There's clearly reason to be concerned. What we don't know is, are we asking the right question? Is hitting your head bad for everybody? Or a better question is for whom is hitting your head bad.? There might be individual factors which make one person more vulnerable than others.
Dr. Aaron Carroll: So what are we doing about all of that? Or are we doing anything about all of that?
Dr. Tom McAllister: Well, we are. So one of the big advances in the last decade or so has been the development of sensors that we can put in, for example, football helmets, or conceivably military helmets, that will measure with some obviously measurement error built into that, the amount of force that people are exposed to. So, for example, in the case of football players, we've done studies in which the helmets are equipped with accelerometers, similar to what you might find in your iPhone or your watch, your Fitbit, that will measure the G-forces associated with a particular hit to the head.
And when we started this work, it seemed like it was going to be pretty straightforward and easy. We're going to equip the whole football team. We're going to measure them. And we're going to say, you had a concussion and it was a ADG hit, and you did not, and it was a 79 G hit. Then we're going to say, there we go, there's the threshold. So it turns out sadly that it's way more complicated than that in part, probably because these sensors may not be completely accurate in measuring what's really going on. But it's very clear that people can be diagnosed with a concussion at relatively low impacts. Not that I would want them that, but I've had 50 or 60 Gs, for example. And there are other people who can sustain 110 G 120 G hit, bounce right up and have apparently no symptoms associated with concussion.
And so that has led the group that we're working with and others to speculate that perhaps context matters. So might it be that it's not just a particular smoking gun hit, but it's the fact that the person was hit five or six times earlier in the game or in the practice or earlier in the week, and there's a kind of priming or kindling of the brain that's going on, which makes that next blow the one that sort of is associated with concussion?
Dr. Aaron Carroll: So, is there anything we can do in the short-term about all of this? Is there actions we can take to try to limit the damage?
Dr. Tom McAllister: So, I think there are. We're part of a large study that has been funded by the US Department of Defense and the NCAA, called the Care Consortium. And that has basically allowed us to put together a concussion research network. We now have 26 civilian universities and colleges who are participating in four of the military service academies. And basically the way it works is that we do a set of baseline measures before any season starts in all sports and both men and women. So it's going to be the largest study to date of sport-related concussion.
And then if somebody is identified as having a concussion, we repeat these measures at five time points, so that we have a really good idea of what the natural history of the injury is. And we've now been funded to do a follow on studies, so that we're getting an additional time point when these participants graduate from university or Service Academy, to look at their cumulative effects of hitting your head over and over and over again. And we're working to hopefully be able to extend that study of this cohort for decades if we if [crosstalk 00:33:28]
Dr. Aaron Carroll: Right. Of course that's part of it, is following what happens over a lifetime. But in the short term, how long do you expect that study to run?
Dr. Tom McAllister: Let's see, it's run for about... We're in our fifth year now. We have funding for two years to do the cumulative study and we're applying for the more longitudinal component in five-year increments. So we'll see in a few months how that works.
Dr. Aaron Carroll: Always we talk about long-term [inaudible 00:34:00] it's so fascinating because of course it takes so much work to get this going, but you know what, we really are so often interested as the long-term downstream fix. But you need to start so many years ago to find those things out. It's good that, that's going on, but I imagine we'll be getting data for years to decades.
Dr. Tom McAllister: Yes. Yes, indeed. Absolutely.
Dr. Aaron Carroll: Is there any other work that you're working on in this area that we should know about?
Dr. Tom McAllister: As part of this study that we're talking about, there's a subgroup of the athletes and participants who undergo a much more detailed characterization of brain structure and function. So these folks undergo multimodal MRI imaging, which allows us to look at the structure and function of the brain's white matter. We're looking at a regional blood flow in these folks and, of great interest to me is this idea that people probably differ in their vulnerability to both the injury itself, the sequelae of the entry and the recovery trajectory.
So we've been looking at fluid biomarkers of good response and bad response. We've been looking at genetic predictors of outcome as well as vulnerability. And I think that what we want to do going forward is to actually begin to look at some of what we think are the hallmarks of this chronic traumatic encephalopathy, meaning a pet study of the protein tau, which we think is one of the markers for the condition.
Dr. Aaron Carroll: And is that something that is a marker, just to tell us that it's happening or something you think you can act upon to limit or reverse some the damage?
Dr. Tom McAllister: Yeah, that's the million-dollar question. So like Alzheimer's, it's a condition, and many other neurodegenerative disorders. Tau's is a protein that is a normal part of the brain, but if it accumulates in certain areas that can provoke, we think, an inflammatory response, which can have destructive downstream effects. And it turns out that many of these proteins can be folded improperly and that can lead to accumulation and failure to remove it.
So your question is exactly the right one, which is, is that just a marker for something bad that's already happened, or is that the precipitating cause? And we don't know that at this point in time. If it's the precipitating cause, then one could think about vaccines that might do. Or medications that might facilitate its removal from the brain. But similar to Alzheimer's disease, where a lot of work is focused on amyloid, another protein, and the collection of that and whether we can vaccinate against it or we can... It hasn't worked out the way everybody hoped yet. And so it's the kind of work that we're going to just have to go through until we get the answer.
Dr. Aaron Carroll: Well, until then it sounds like prevention is still our best bet.
Dr. Tom McAllister: It is indeed. It is indeed. Yeah.
Dr. Aaron Carroll: Tom, thanks so much for being here. This has been fascinating. If we can, I'm sure we'd love to have you back again as new details and new information arises.
Dr. Tom McAllister: My pleasure. As you can tell, I love to talk about this stuff, so I'm glad you're shutting me off.
Dr. Aaron Carroll: We love to hear about it. Thank you very much.
Dr. Tom McAllister: All right. Thanks, Aaron.
Dr. Aaron Carroll: Thanks again for listening to the Healthcare Triage podcast. We are here each and every month to bring you information about health, health research, health policy, tons of information you can use. If you'd like to support the show you can do so through patreon.com. Subscription services allows you to help support the show in any way you like. Go to patreon.com/healthcaretriage.