What happens in the brain during a concussion? What is at risk when individuals – athletes or otherwise – sustain multiple concussions? What is CTE, and how can we prevent it? Professor of physical medicine and rehabilitation Dr. Harvey Levin explains.
Harvey Levin, Ph.D., is a professor and research scientist at Baylor College of Medicine and the Michael E. DeBakey Veterans Affairs Medical Center, where he researches the chronic effects of traumatic brain injuries.
See below for more of Dr. Levin’s research:
Facing Concussions Head On: CTE Research
Erin: Welcome to Body of Work an exploration of health topics in the news and important issues facing science with experts from Baylor College of Medicine. I'm Erin Blair and my guest today is Dr. Harvey Levin professor of physical medicine and rehabilitation.
Erin: Although we hear the term quite often, what exactly is a concussion or, more clinically, a mild traumatic brain injury?
Dr. Levin: So, these terms concussion and mild traumatic brain injury are interchangeable. This is a sudden onset of neurological changes associated with impact to the head or impact to other regions of the body which causes sudden acceleration of the brain inside the skull which have similar effects as an impact to the head. Concussion or mild traumatic brain injury can be detected by observing the individual to lose consciousness or have impaired consciousness. The symptoms that typically arise immediately or after some delay include: headaches, dizziness, poor postural control, fatigue, and frequently confusion. However, some concussions, especially in sports, may be difficult to detect just by visually following the player. They may be quite subtle and the player may not lose any consciousness and may appear to the layperson to be functioning normally. So, there are different gradations of concussion and mild traumatic brain injury.
Erin: You hear a lot about concussions in regards to contact sports or just athletes at risk of mild traumatic brain injuries? What other events cause concussions?
Dr. Levin: It's a good question. We hear the term concussion in the news frequently in reference to athletes, but in fact in non-athletes the most common causes are motor vehicle crashes, assaults, being struck with an object, or impact of the head against a solid object. The causes depend also on the individuals age. Older people, for example, are more vulnerable to falls and in young adults and late adolescents motor vehicle crashes occur at a high rate.
Erin: So, whether it's an older person with a fall or cheerleader or a professional athlete, car crash victim, can you describe what happens in the brain in a concussion?
Dr. Levin: In a concussion, there's a tearing or stretching of these nerve fibers that connect different regions of the brain. This may be reversible or the effects may be more persistent and what those fibers do is help the brain work. Ordinarily, they help with communication among different regions of the brain. For example, communication between the prefrontal cortex which is heavily involved in our cognition decision-making computation and the parietal region which gets involved in working memory. That complex functioning that we are capable of most days depends on brain networks so if there is a disruption in communication among brain regions these relevant networks are dysfunctional and we don't perform well. Other changes in the brain that I mentioned earlier have to do with focal brain lesions such as contusions.
Erin: Is that like a bruise?
Dr. Levin: Yes, it's a bruise to the cortex of the brain. In fact, these are quite infrequent in sports related concussions but they're more common in persons who are involved in a motor vehicle crash especially in a high velocity rollover they're much more common and they contribute to the severity of the impairments that result from the injuries.
Erin: So what kind of post-concussion symptoms do patients experience? How long can that persist?
Dr. Levin: The most common symptoms are headaches, dizziness, fatigue, increased sensitivity to light or to noise. The question of how long these symptoms may persist is somewhat unsettled and controversial.
Erin: What kind of recovery is required? Are there personal factors that might affect the amount of time it would take for someone to recover from a concussion?
Dr. Levin: After a concussion, an individual is more vulnerable to suffering another concussion. Consequently, it's important to observe a period in which the individual refrains from engaging in a contact sport, or even if their hobby is boxing, they shouldn't be sparring. They should take it easy, not completely rest necessarily, but take precautions not to have another injury within a short period after having their first concussion. In the early 1990s, there were seminal reports about college football players and reporting that 90% of these players would fully recover in terms of their symptoms and being capable of returning to play in seven to ten days. We now know that there are exceptions to that timeline, particularly in adolescence. For example, high school contact sport athletes and youth contact sport athletes and also female athletes in these groups approximately 20% have not recovered in terms of their post-concussion symptoms even at 30 days after injury. So, there are subgroups that are more vulnerable. People who've had previous concussions, people who have had migraine headaches prior to their injury, and individuals who've had some emotional conditions, depression especially, are also more vulnerable to having a longer period of post-concussion symptoms. We've learned that in non-sports-related mild traumatic brain injury there's a shift toward older age. We also know that mature adults are now more often engaged in sports than they used to be and we don't know as much about the timeline for their recovery.
Erin: Say the concussed person was an athlete and continues to play an impact sport, what happens if they endure another concussion?
Dr. Levin: We're still learning about the effects of repeated concussions and I'll make the distinction between repeated concussions and repetitive head impacts. Repetitive head impacts, for example in football players, in rugby players, occur often during a typical game depending on what position the individual plays. There is emerging evidence that the effects of these repetitive impacts over the course of a season which can be hundreds of these head impact, and over successive seasons, thousands of repetitive head impacts may have cumulative effects. There are some investigators who are of the opinion that these head impacts are more deleterious than the concussions, but this is an unsettled question. In regard to repetitive concussions, there's some evidence that the effects are cumulative and also that the distribution of these concussions over time is a relevant factor. In other words, individuals who have repetitive concussions in short succession, for example separated by days or even a week or two, these might be more deleterious than someone who's had several concussions spread out over a decade. This issue is important not only for athletes but also those in the military where they may be exposed to repetitive blast-related trauma affecting the brain. In the combat theater, many of these blasts could occur in a short period of time.
Erin: Would say that to the individual, repeated head impacts would feel less dire or less distressing than a concussion?
Dr. Levin: For the persons experience, the head impacts probably less of a concern because they don't typically cause symptoms as following a concussion as I described earlier. However, we do know that there are effects which are subtle. There are a small number of recent brain imaging studies showing that over the course of a season, for example playing hockey or football, there are detectable changes in these brain white matter tracks which can be seen on a type of imaging called diffusion tensor imaging. The player may or may not have had a concussion and may or may not be aware of any changes and it's still not clear whether there are cognitive changes associated with these detectable changes on brain imaging. This is ongoing work, and it raises issues but we're just at the beginning of this area of research.
Erin: Why aren't helmets preventing mild traumatic brain injuries?
Dr. Levin: Helmets are quite important and there's some evidence they may protect against focal lesions of the brain or perhaps skull fracture, they may prevent that. I don't think it's entirely clear what the effects of helmets are on preventing this sudden stretching of these white matter tracks or these fibers this effect occurs after an impact to the head. If we think of the brain floating in cerebral spinal fluid, yes, an analogy that sometimes is made, if you have a plastic toy and a bathtub full of water. So, at the time of the sudden acceleration/deceleration, there's a swirling or rotational acceleration imparted to the brain and these nerve fibers then may tend to stretch. If this rotational acceleration is of sufficient velocity, they may tear. The effects of this rotational acceleration to the brain may not necessarily be diminished very much by wearing the helmet.
Erin: Sure, it's not keeping the head still, in one place. It's just protecting.
Dr. Levin: Yes, exactly. So, for focal impacts it does offer protection. But if the head is accelerated very quickly and suddenly decelerated as, let's say a running back running at a high speed, and suddenly there's a collision or suddenly the players thrown on the ground there is likely to be this type of acceleration/deceleration effect of the brain floating in this cerebral spinal fluid.
Erin: I understand that's it's quite an image. You had said that the age of the person had an effect on the recovery time. Why is that?
Dr. Levin: An underappreciated aspect of concussion and mild traumatic brain injury is in pre-adolescence and throughout adolescence and until at least the mid-20s. The prefrontal cortex and the underlying white matter connections between prefrontal cortex and other regions of the brain are still undergoing maturation. So, if there are repeated concussions or head impacts during this period of maturation, there is concern about what the long-term effects may be when the individual is an adult. This isn't known, but we do know a fair amount about these maturational changes because there have been major brain imaging studies of healthy children and adolescents as they age chronologically, and we suspect that there could be deleterious effects by exposure to multiple concussions and repetitive head impacts. In an older individual and here I'm talking about a person perhaps 60 years old or older, we know that there's a higher vulnerability to developing a collection of blood in the subdural compartment of the brain even from what we would consider to be relatively minor head trauma. We don't know what the long-term effects of that are, and we don't know much about what the long-term effects of concussions and repetitive head impacts may be as a person is getting into their 50s and 60s and 70s. But, we do know that from epidemiologic studies that having a history of concussion and mild traumatic brain injury is a risk for developing neurodegenerative diseases such as Alzheimer's and Parkinson's.
Erin: In recent years, we've heard a lot about aging football players and boxers having CTE. What is CTE?
Dr. Levin: Anyone that is attentive to the news has heard about chronic traumatic encephalopathy which is a pathological diagnosis, so it's not a diagnosis made clinically in a living person. It's a diagnosis made strictly on the presence of specific pathologies in the brain. So, it's made in brains that have been donated, and at this point, most of these brain donations came from families of former athletes, particularly NFL football players. In studies of these brains, the presence of chronic traumatic encephalopathy has been confirmed in large proportion of these donated brains and it's thought that this occurred as a result of being exposed to multiple concussions and repetitive head impacts over the course of their careers with athletes. However, it's unclear how much of a risk factor this is for the other thousands, millions of athletes. These athletes whose brains were donated had very extensive careers playing at the highest level of professional football, and we don't know to what extent any of this can be generalized to people that play contact sports in college, high school, or younger. We don't know what the threshold is for causing this type of pathology. Chronic traumatic encephalopathy typically begins in the depths of the frontal lobes involving white matter below the cortical surface, and it's associated with an excess of what's described as hyper-phospholated tau. Tau is found in other brains but an excessive amount is found in the brains of individuals who have CTE pathology. Initially, it's located in a very local or discrete region of the brain, but as the years pass it tends to spread to other regions such as to the temporal lobe, the parietal lobe, and it may become diffuse through the brain. As it increases, there are associated changes or degeneration of the brain that can even be seen on an imaging, but in the early stages it cannot be seen or detected by currently available brain imaging. Again, this is under investigation. With the changes in the pathology as it progresses, there have been published descriptions of the onset of changes in behavior and in cognition, but this is based on retrospective reports by family members because the pathology has been analyzed in the brains of former athletes, primarily. These individuals did not undergo any particular assessments before their death, so it's all based on retrospective reports by families who were interviewed at some point after the pathology was analyzed.
Erin: So, you're saying that CTE can only be detected with the donation of the brain of a dead athlete?
Dr. Levin: It's a pathological diagnosis.
Erin: So, there's not biomarkers or anything like that that we can see now and say oh that's a problem you know? You could have more problems as you get older…
Dr. Levin: There are biomarkers, and there are studies that have been done. For example, I mentioned the tau? There was a study of analyzing the cerebral spinal fluid of boxers in Sweden. They were Olympic level boxers, and they had analysis of their tau from undergoing spiral taps. There was some elevation and it tended to be elevated after they had finished bouts, but we don't know what the threshold is for tau. We don't know what predictions can be made by doing this measurement of tau in the spinal fluid. There are now some biomarkers that are measured using positron emission tomography which is a type of brain imaging or nuclear medicine. This work is ongoing. We still have very little data about how frequently there is an elevation of tau on the PET scanning, and we don't know yet to what extent this is predictive of changes in cognitive performance or changes in behavior. So, most of the information on cognitive problems and behavior at this point is based on this retrospective interview information that was obtained from the next-of-kin of those whose brains have been analyzed pathologically.
Erin: Can we attribute any particular diseases or conditions to CTE?
Dr. Levin: CTE is a disease. It's a neurological degenerative disease, but what has been reported is that there is a co-occurrence in a sub-group of these brains with evidence for Parkinson's disease and possibly Alzheimer's.
Erin: What steps are being taken to prevent CTE or multiple mild traumatic brain injuries?
Dr. Levin: There have been changes in the clinical management. This is particularly the case in sports in which there are health providers which can be physicians, there are athletic trainers, neuropsychologist who perform various standard tests on players after they've had a concussion. These tests are often done preseason, so there's a baseline while the player is healthy. So, these tests include a checklist for the symptoms such as headaches and dizziness and cognitive performance, reaction time, attention, memory. This kind of assessment is done, and before the player can return to play she or he has to have resolution of these symptoms. Their postural control or balance has to be returned to normal, and their cognitive performance has to return to normal. So, they're monitored by the health provider, and when they're thought to have been clinically recovered, they're cleared to return to play. This is very common now in school systems, high schools, in collegiate sports, and professional sports. The concussions are managed. I don't know that there's as much reporting about how they're managed as there is at the college level in regard to mild traumatic brain injury versus non-sports related. I think there's a lot of work to be done and here. I'm referring to individuals who are brought to the emergency department. The rate of clinical follow-up of these individuals is fairly low, and in my view there's a lack of standard protocols compared to what we see have been developed in the care of athletes. Now of course in the individuals who are cared for in emergency departments, these individuals are not returning to practice and to games where they're going to be exposed more head impacts. So, it's much different, but that's not to say that closer follow-up, especially of individuals at high risk for persistent post-concussion symptoms. I think a case could be made that these subgroups should be followed up, and they may need some follow-up care.
Erin: Do you think that parents should discourage their children from engaging in contact sport? Is it something where there's enough known about traumatic brain injuries to caution young people against contact sports all together?
Dr. Levin: This is a difficult question which I think many families are confronting. I think, taking football as an example, I think the quality of the training by the coaches is extremely important. One aspect of this is that, from what I've read, the quality of the training and oversight of student athletes tends to be much higher at the level of collegiate sports then for example junior high school or high school. It's not to say anything disparaging, and I would surmise that there are major differences across the schools. Some schools have higher quality programs than others but I do think that it should be thought through very carefully, and the player and the family should be aware of the risks. I think it's important for the player if she or he is hit and is experiencing the symptoms that we've discussed that they should come forward and mention this to their coach, and not try to be tough about it. Because in the past, and unfortunately, even at present, there's a tendency for some players to feel very loyal to their team, and they want to make a contribution. They may feel macho. They may be reluctant to come forward and say that they were hit, that they have headache, that they're dizzy. We know now there is a vulnerability after having a concussion. So, this individual has to have some rest, not for a real long time – maybe a couple of days, but they should definitely not be in play. They need to go through the concussion management that we talked about and gradually return to exercising and training with the team, then returning to game. But, they have to go through this concussion management. If they don't, based on the evidence that we have seen, this is increasing their risk of persistent effects that may only be detected later when they're adults.
Erin: Can you tell us a little bit about your research areas?
Dr. Levin: My research areas include concussion and sports concussion. Recently, with colleagues at Baylor and University of Texas Medical School in Houston, we completed a study of high school athletes who had sustained concussions. They were primarily football player, and we tested the hypothesis that players who had a concussion and were thought to clinically recover within 30 days and were cleared by their health providers to return to football would still have aberrant or dysfunctional brain imaging findings on advanced brain imaging. So, our hypothesis was that the brain was not recovered in these individuals even though they were clinically returned to return to play. We had a control group of similar athletes, similar demographic features, but they had an orthopedic injury – no involvement of the head. Sure enough, we found that there was evidence on the functional MRI that their brain networks were still dysfunctional. We also found on diffusion tensor imaging that these white matter tracks were not recovered to what would be normal for their age. So, we are planning a follow-up project to that look at related questions. For example, comparing male and female athletes in their recovery of brain function and structure as well as their clinical recovery.
Erin: With all that you know about traumatic brain injury, you bicycle in the Texas Medical Center. Do you ever think about the fact that you could injure your own brain?
Dr. Levin: It probably crosses my mind several times a week, and I try to be careful. I have to balance that against my enjoyment, exercise, and I have an excellent parking space free of charge. So, there are benefits but I have to be careful.
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