Mild TBI or concussion typically results in impaired neurological function and symptoms. In most cases, these resolve over time if repeat injuries are avoided. Evidence for chronic/lasting cognitive impairment from a single mild TBI or concussion is limited, but some population-based studies suggest slightly higher risk for behavioral, psychiatric, and neurological problems later, after even a single mild TBI. Chronic symptoms after mild TBI or concussion have been relatively strongly associated with preexisting problems such as migraines, ADHD, learning disability, and psychiatric disorders. There is some evidence that repetitive mild TBI or concussion may increase risk for late dementia and neurocognitive disorders, but this is still under investigation.
Head impacts do not show a universal biomechanical threshold for causing symptoms or dysfunction. Chronic neurobehavioral impairments may be associated with participation in activities involving repetitive head impacts, but the challenge is that the threshold is uncertain and probably differs on an individual basis. There has been very little work specifically looking at the relationship between comorbid conditions and repeat impacts without concussion (subconcussion), or specifically linking repetitive head impacts and neurodegeneration. These have been mostly case series or anecdotes, and these types of studies are unable to demonstrate definitive causality and are unable to determine actual risk.
Dr Coughlin: Our group at Johns Hopkins Medicine is 1 of several scientific teams that are working to better our understanding of repeated, sports-related hits to the head and the effects on mood and memory. We are concerned that the repeated concussive and subconcussive blows may set off a molecular cascade wherein the immune cells in the brain that normally repair injury actually go into overdrive and cause more harm than good. This molecular response of heightened brain inflammation has been hard to study in the living human brain, until now, as we can’t access brain tissue. However, this is an exciting time for concussion research because we now have a way to measure this inflammation safely in the brains of players through use of imaging.
Neurology Advisor: What are the implications of this evidence for clinicians, policymakers, coaches, and others?
Dr Giza: The implications are different for different stakeholders. Clinicians need to understand both the different types of acute injuries and the different types of outcomes. Then, each patient needs to be considered on their individual characteristics. Clinicians also need to have tools to properly communicate medical findings to athletic and academic staff.
Policymakers need to provide simpler education and guidance for nonmedical stakeholders. This means more easily interpretable rules like:
- “When in Doubt, Sit It Out”
- Avoiding repeat injuries in close succession
- Leaving clinical/medical flexibility in decision-making for healthcare providers
- Empower officials to enforce proper rules of play
- Be aware that knowledge and standards for TBI identification and management are changing rapidly, so policies need to be evidence-based and able to evolve with new information
- Consider unintended consequences of policies based on “gut” or “common sense,” but lacking data or built on incomplete data
- Consider the importance of trained healthcare providers (such as certified athletic trainers) at youth sporting events
Coaches need basic knowledge about clinical symptoms and characteristics of injuries, and they need to understand the importance of “When in Doubt, Sit It Out,” rather than trying to make a diagnosis, which is better left to healthcare providers. Coaches should also provide an athletic environment of respect for rules and other athletes, including the opponent, and they need to understand evolving strategies for training and new laws that govern sports practice and are aimed to diminish risk for injury.
Dr Coughlin: Current guidelines for clinicians, coaches, and players underscore a cautious approach to return to play after sport-related concussion. Our goal is to use new imaging technology to provide more detailed answers to the questions about the long-term risks and effects from repeated, sports-related hits to the head. For example, we recently showed that positron emission tomography imaging can capture the increase in a marker of brain injury in active and recently retired National Football League players who were exposed to repeated concussive and subconcussive hits. Now, we are following players over time with this imaging to answer the question of whether the brain injury persists, or whether the brain repairs itself. If the brain repairs itself, we expect the signal on the positron emission tomography imaging to diminish over time. However, If the brain signal persists among players, then we will be positioned to carefully study and characterize what aspects of play (position, age of first concussion, and so on) might make a given player more vulnerable to damaging effects.
Neurology Advisor: Do you think mental health batteries should be included in presport evaluations?
Dr Giza: Asking about baseline cognitive and mental health problems is an important part of every preseason screening or neurological assessment. Detailed administration of formal mental health batteries or widespread formal neurocognitive testing, particularly in youth, have not been well validated. In most nonprofessional settings, where resources are more limited, detailed testing may not be practical.
Dr Coughlin: As a psychiatrist who specializes in treatment of young adults with mood disorders such as depression and bipolar disorder, I think mental health assessments are a helpful aspect to the presport evaluation. The evaluation is only useful, however, if it is linked to access to care for those in need. The science cannot yet predict whether repeated hits to the head in sport will put a given individual at increased risk for depression, but presport evaluations are a wonderful opportunity to check in with players about their mental health and to guide those who are suffering to the relevant specialist. Mood disorders are very treatable.
Neurology Advisor: What should be the focus of future research on this topic?
Dr Giza: Additional needs are prospective studies that include preinjury assessment of neurobehavioral problems in different age groups, demonstration of the utility of having access to behavioral health providers for proper evaluation and treatment of injuries, identification of resiliency factors and training to enhance resiliency among all at-risk individuals even before injury, and more research focused on specific interventions that may be beneficial to general brain health and either reduce risk for injury or enhance opportunities for recovery.
Dr Coughlin: because the imaging technology is now available to visualize and measure a marker of brain injury in the living human brain, we are working hard to gather data from repeated imaging of recently retired National Football League players. These data will help us answer the questions about whether there are aspects of the game that should be changed to protect players, or whether there are protective factors that may prevent injury or facilitate brain healing after repeated, sports-related hits. We will have those answers in the coming years, and I look forward to sharing that knowledge to guide athletes of all levels of play.
- Montenigro PH, Alosco ML, Martin BM, et al. Cumulative head impact exposure predicts later-life depression, apathy, executive dysfunction, and cognitive impairment in former high school and college football players. J Neurotrauma. 2016;34(2):32-340.
- Wright MJ, Woo E, Birath JB, et al. An index predictive of cognitive outcome in retired professional American Football players with a history of sports concussion. J Clin Exp Neuropsychol. 2016;38(5):561-571.
- Singh R, Meier TB, Kuplicki R, et al. Relationship of collegiate football experience and concussion with hippocampal volume and cognitive outcomes. JAMA. 2014;311(18):1883-1888.
- Adler CM, DelBello MP, Weber W, et al. MRI evidence of neuropathic changes in former college football players [published online October 17, 2016]. Clin J Sport Med. doi: 10.1097/JSM.0000000000000391
- McKee AC, Cairns NJ, Dickson DW, et al. The ﬁrst NINDS/NIBIB consensus meeting to deﬁne neuropathological criteria for the diagnosis of chronic traumatic encephalopathy. Acta Neuropathol. 2016;131:75-86.
- Alosco ML, Kasimis AB, Stamm JM, et al. Age of first exposure to American football and long-term neuropsychiatric and cognitive outcomes. Transl Psychiatry. 2017;7(9):e1236.
- Munce TA, Dorman JC, Thompson PA, Valentine VD, Bergeron MF. Head impact exposure and neurologic function of youth football players. Med Sci Sports Exerc. 2015;47(8):1567-1576.
- Cobb BR, Urban JE, Davenport EM, et al. Head impact exposure in youth football: elementary school ages 9-12 years and the effect of practice structure. Ann Biomed Eng. 2013;41(12):2463-2473.
- Bahrami N, Sharma D, Rosenthal S, et al. Subconcussive head impact exposure and white matter tract changes over a single season of youth football. Radiology. 2016;281(3):919-926.
This article originally appeared on Neurology Advisor