Concussions and TBIs
Keeping Your Head in the Game
I get questions about concussions and TBIs all the time— mainly from anxious parents who, understandably, have concerns about enrolling their kids in high-contact sports. To tackle this topic, I brought in the big guns:
Dr. Sarah Scheinman (a literal neuroscientist) and Dr. Julie Bruene (a sports medicine physician who treats these things all the time). I truly feel like I have assembled an Avengers-style brain health team. Let’s dig in.
What is a Concussion?
So, what exactly is a concussion and how does it affect the brain? A concussion is a type of traumatic brain injury (TBI) typically caused by an impact to the body and/or head that causes the brain to bounce or twist against the interior of the skull.
Within the skull, the brain is surrounded by cerebrospinal fluid (CSF), an ultrafiltrate of plasma that provides nutrients and protection to the brain. The CSF cushions the brain and prevents it from rattling around inside the skull during everyday activities such as walking, nodding, and bending over. The skull itself is one of the strongest bones in the body and can handle large forces that give way to large accelerations of the head (remember Newton’s second law of motion?). HOWEVER, our gelatinous brains cannot withstand the same amount of force that our bony skulls can. When the skull is jolted too fast or impacted by something such as a punch or a collision, the brain continues its original plane of motion within the CSF, eventually striking the skull’s hard interior, often repeatedly, before coming to rest once again. This substantial acceleration of the brain inside the skull translates to an equally massive force on the brain that causes the TBI.
The Neurobiological Impact
This type of injury is classified as “traumatic” because it typically results in a temporary loss of normal brain function. When the brain ricochets off the inside of the skull at high speed, long, spindly brain cells called neurons stretch and even tear, disrupting their ability to communicate with one another. Specifically, the cell membranes of neurons become damaged, which causes an imbalance in the flow of ions into and out of the cell, dysregulation of neurotransmitter levels, and an overall inhibition of neuronal activity. Damaged neurons release signaling molecules that alert the brain’s immune system to the injury and trigger the activation of resident immune cells called glia. Glial cells play key roles in maintaining brain health and responding to injury and their activation leads to the release of inflammatory mediators such as cytokines and chemokines. However, while the activation of glial cells helps in clearing the areas of primary injury and preventing subsequent infections, prolonged inflammation, such as that which occurs following severe concussions, can cause additional damage to brain tissue beyond that which is caused by the initial injury.
In general, when homeostasis is interrupted, neurons have mechanisms to restore balance. However, these biological processes require large amounts of energy to carry out, rapidly depleting cellular energy stores and overburdening mitochondria, the powerhouse of the cell. To make matters worse, decreased energy availability within neurons is compounded by reduced blood flow to the brain which can persist for over a week post-injury, beyond the point of clinical recovery. In conjunction with sustained inflammation, this energy crisis is one of the primary reasons that the concussed brain is more susceptible to damage caused by subsequent injuries.
Long-Term Consequences
For example, second-impact syndrome (SIS), is caused by the occurrence of an additional concussion before recovery from an earlier injury, which can cause rapid and catastrophic swelling of the brain, herniation, and even death. Multiple concussions can also increase susceptibility to a condition called chronic traumatic encephalopathy (CTE), a progressive neurodegenerative disorder that leads to problems with thinking and memory, and physically manifests as a reduction in brain weight, cortical atrophy, abnormal protein aggregation, and brain tissue scarring. However, the risk of developing conditions such as SIS and CTE can be mitigated by the appropriate clinical management of concussions and by ensuring proper recovery to prevent long-term complications.
The Nuanced Relationship Between Concussions and CTE
While we've discussed the potential long-term consequences of concussions, including chronic traumatic encephalopathy (CTE), it's important to note that the relationship between concussions and later-life brain health is complex and still not fully understood. Recent research, as highlighted in the 2022 Amsterdam Consensus Statement, presents a more nuanced picture:
Mental Health Outcomes: Studies have not found an increased risk of depression, suicidality, or psychiatric hospitalization in former amateur athletes compared to the general population. This includes American football players and soccer players.
Cognitive and Neurological Outcomes: Former male amateur athletes were not found to be at increased risk for cognitive impairment, neurological disorders, or neurodegenerative diseases compared to the general population. However, some studies have reported higher mortality rates from neurological diseases and dementia in former professional American football and soccer players.
Methodological Limitations: It's crucial to note that many studies in this field have not accounted for various factors that can influence brain health, such as genetics, education, socioeconomic status, lifestyle factors, and other medical conditions. This makes it challenging to establish a clear causal relationship between early-life sports participation and late-life cognitive impairment or dementia.
CTE Neuropathology: The term CTE now refers specifically to a neuropathological entity (CTE-NC) identified post-mortem. While it appears to be more common in brain samples from former professional athletes with high exposure to repetitive head impacts, its prevalence in the general population is unknown. Moreover, the relationship between this neuropathology and clinical symptoms during life is not yet fully understood.
Need for Further Research: To establish clearer links between sports participation, concussions, and long-term brain health, more comprehensive studies are needed. These should account for various risk factors and confounding variables.
Given these complexities, it's important to approach the topic of long-term effects of concussions with caution. While we should take concussions seriously and manage them appropriately, we should also be careful not to draw overly broad conclusions about their long-term impacts based on current evidence. The field continues to evolve, and our understanding may change as more research is conducted.
Concussions in Young Athletes
The developing brains of young athletes are particularly vulnerable to the effects of concussions. Recent research has led to recommendations specifically aimed at reducing sport-related concussions in children and adolescents. These include:
Mandating mouthguard use in ice hockey
Prohibiting body checking in youth ice hockey
Implementing neuromuscular training programs (particularly effective in rugby)
Limiting contact practices in American football
Recovery and Management
Our understanding of concussion recovery has evolved. The previous approach of "total rest" has given way to a more nuanced strategy. Current guidelines recommend:
A brief period of rest (24-48 hours) followed by gradual reintroduction of light activity
Focusing on symptom control through techniques like neurovestibular rehabilitation and balance training
Addressing associated issues such as neck pain
Carefully monitored return-to-learn and return-to-play protocols
It's important to note that common pain medications often prove ineffective against concussion-related headaches, necessitating specialized management approaches.
Diagnostic Advances
While clinical assessment remains the cornerstone of concussion diagnosis, new tools are emerging. The Sport Concussion Assessment Tool (SCAT6) is currently the recommended initial assessment tool for individuals 13 and older, with a modified version (Child SCAT6) available for younger children.
Promising research is also being conducted on concussion biomarkers. For instance, Abbott's i-STAT TBI Plasma Test measures levels of specific proteins associated with brain injury. However, these tests are currently used to guide further diagnostic decisions rather than as standalone diagnostic tools.
Balancing Risks and Benefits
As a mom of two kids who may or may not find themselves interested in contact sports down the road, I am following this quite closely. (Sidenote: the thought of a child of mine having ANY athletic abilities boggles the mind. But I digress.) The prevalence of concussions in sports, particularly among young athletes, presents a significant public health challenge. However, the benefits of sports participation - including physical fitness, social development, and mental health benefits - must also be considered.
To strike a balance, a comprehensive approach is needed. This includes implementing and enforcing protective rules in sports, providing proper equipment and training, educating athletes, coaches, and parents about concussion risks and management, and investing in research for better prevention and treatment strategies.
By addressing this challenge proactively, we can work towards safeguarding the health of our athletes while preserving the many benefits of sports participation.
Stay tuned for our upcoming episode on this topic. We will dig deeper into some of the clinical signs and indications you should be on the lookout for!
About the co-authors:
Sarah Scheinman, PhD, is a Chicago-based neurobiologist with expertise in basic science, preclinical, and translational biomedical research. Her primary focus is on the molecular mechanisms of aging and neurodegenerative diseases, but she also has subject-matter expertise in cell biology, genetics, epigenetics, and psychology. She received her PhD in neuroscience from the University of Illinois College of Medicine and is currently an NIH-funded research fellow at Northwestern University. Spoiler alert: you’ll be seeing and hearing a LOT from Sarah on the Unbiased Science Podcast. You will fall in love with her just as I have!
Julia Bruene, MD, is a sports medicine physician with special interests in acute and chronic orthopedic injuries, concussion management, care of female athletes, care of combat athletes/mixed martial arts, and special needs athletes. Also, NBD, but Julie is the team physician for the Chicago White Sox, Chicago Bulls and DePaul University. She also co-hosts the AMAZING “Your Doctor Friends” podcast with Dr. Jeremy Alland. After listening you will feel like they are YOUR DOCTOR FRIENDS, IRL!