Concussions in athletes: to play or not to play

     You’ve collided with someone, fallen, been struck by flying athletic equipment in a sports game. After an initial evaluation, involving an MRI or a head CT, the doctor tells you that it’s just a concussion, and it is not that bad. After all, your brain is not bleeding, you are not comatose, and with proper monitoring of your health over the next few weeks or months, full recovery is expected.

    Concussions, or mild traumatic brain injuries (MTBIs), are considered to be brain injuries that result in a temporary loss of brain function. They are disturbingly common in competitive sports that involve frequent collisions like football, hockey, soccer, and boxing. While it is true that hitting one’s head can involve a more serious brain injury, concussions should not be treated lightly. A concussion is often accompanied by one or more of the following often debilitating symptoms immediately after injury: momentary loss of consciousness or a changed level of consciousness (lethargic, etc.), alteration in mental state (confusion), loss of memory before or after injury, headache and nausea (1). Oftentimes, post-concussive symptoms (PCS) such as headache, fatigue, insomnia, anxiety, problems with concentration and memory, and psychiatric complications, persist weeks to months after a concussion (7). It has also been seen that previous MTBIs increase one’s susceptibility for future, more complicated MTBIs (1). What changes are going on in the brain when it is concussed to cause these symptoms and are these changes really transient? Do changes in the brain post-injury make individuals more susceptible to psychiatric conditions like depression, or do one’s feelings about alterations in memory, cognition and/or loss of position (on a sports team, etc.) lead to this? Finally, when is the appropriate time for concussed athletes to return to their sport healthy and with the least risk to future MTBIs?

    Last year, my brother, Jon, went up for a ball in a soccer game against another boy and they collided. Both went down initially but afterwards my brother stood up. He swayed on his feet and his teammates rushed to him, trying to get him to sit down. His eyes were unfocused, his legs would not bend, and he thought he was already sitting. He does not remember the actual injury or the moments that followed. We were later informed that his inability to control his body immediately following the MTBI is common and fits the criteria of a temporary loss of brain function. His nervous system was still capable of walking and talking, but Jon himself was momentarily both unable to control his actions and unaware of them. It seems that after a concussion certain connections in the brain are affected, such as those between an individual’s sense of self (their ability to think, feel, and do) and their nervous system, those involved in memory and cognition, and perhaps those involved in systems of neurotransmitters (leading to irritability and insomnia) as well.

    During an MTBI, alterations in connections in the brain are often due to concentrated injury to parts of the brain, which, commonly, are the brain stem, temporal lobes, and frontal lobe. Damage to the brain stem has been correlated with concentration/memory problems, disorientation and frustration, damage to the temporal lobes with changes in behavior, and damage to the frontal lobe (which is almost always affected during an MTBI) with cognitive changes (in judgment and impulsivity) (3).  Thus, the symptoms after an MTBI can be relatively understood as being created by a combination of disruptions of the signals in the brain, typically in these locations. Most of the physical symptoms are, in fact, resolved within a week or two after injury. However, it is not uncommon for individuals to suffer from PCS months after an injury, and memory and psychiatric problems are observed in a higher percentage in post-concussive individuals (2). This is important because the longer-lasting PCS and ostensibly permanent changes in memory (in some patients) seem so suggest that alterations to connections in the brain are not transient. These alterations might involve small changes leading to a simple rerouting of pathways, but it is also possible that certain pathways, certain neurons and areas of the brain, are so damaged by an MTBI that the original pathway does not exist anymore.

    It has also been observed roughly 17% of post-MTBI individuals experience major depressive episodes (MDE) within 3 months of the initial injury as compared to 33% of individuals who experienced a traumatic brain injury (TBI) within the first year (8). These statistics, compared with the 5.9% of the general population with major depressive disorder (MDD, otherwise known as clinical depression), are startlingly high (9). It seems that something crucial can change in the brain post-concussion, and that the severity of the injury, perhaps to certain locations or pathways in the brain, is related to the development of depression in some individuals.

    A relatively recent study performed by Chen et. al addresses the differences in the appearance of the brains of male athletes (with PCS) that are concussed and depressed and those that are concussed but not depressed (2). Blood oxygenation level-dependent (BOLD) Functional magnetic resonance imaging (fMRI) was used to scan the brains and a significant variation between the brains of non-concussed, concussed, and depressed/concussed individuals was observed. Non-concussed individuals did not demonstrate any reduction in gray matter or hyperactivity in any location in the brain. All concussed individuals showed a loss of gray matter in a certain portion of the brain, while concussed individuals with depression showed additional loss of gray matter density in locations identified to be necessary for memory. An increase in the severity of depression symptoms was correlated with further reduction of gray matter in areas of the brain and increased neural activities in other areas of the brain, both of which have been implicated in MDD and affective disorders (and related to dopamine regulation). Depressed individuals also demonstrated a higher severity of PCS, which could mean that PCS is associated with a greater loss of gray matter during or post-injury (2).

      First off, this study suggests that all concussions cause some loss of gray matter in the brain, and that damage to the brain is permanent. Secondly, an organic origin for depression post-concussion is indicated. It may indeed be possible for an athlete to develop some level of depression because of a loss of a position or frustration due to changes in cognition, but the loss of gray matter in these individuals as well as the high statistical probability of concussed individuals to develop depression suggest that a change in the brain is mainly responsible for the condition. Gray matter is comprised of neuronal cell bodies, dendrites, axons, and terminals. It is where the neurons communicate between one another and once these neurons are destroyed by an injury, they cannot be replenished. The excess gray matter lost in the brains of concussed/depressed individuals not only seems to have destroyed certain neural pathways possibly related to the regulation of dopamine (and other neurotransmitters related to depression) but also seems to have created increased activity in other parts of the brain (related to MDD). Perhaps this increased activity is the brain’s way of coping with the loss of those neurons and pathways. It would be interesting to see whether increased activity in other areas of the brain (not related to depression) are ever observed after an MTBI, or whether every brain that experiences loss of gray matter in the same locations of the brain reroutes its pathways in the same manner with the same result. As every brain behaves uniquely, I would assume that this is not the case and further research on previously concussed individuals is needed.

    In addition to encumbering concussion symptoms, PCS, and possible depression, post-concussion athletes are also at a higher risk for future concussions than they were before injury (6). This is perhaps because the brain has already been injured, has lost neuronal pathways, is still recovering, and is less able to adapt to injury caused by whiplash and light blows to the head. It is also known that individuals who suffer multiple concussions experience more memory and cognitive disabilities, which is most likely due to the increased loss of neurons and pathways for memory with each subsequent MTBI (2). The question is, when are these athletes ready to return to the fast-paced, collision-rich environment of the game? If they will forever be prone to concussions, should they ever be ready? Some individuals demonstrate concussion symptoms for a week or so, and, after the doctor’s “okay” and a short period of rehab, they are back on the field. Other individuals have symptoms that may disappear and reappear weeks later and the same inspection that is given to an individual with “typical” symptoms is not effective for them. Some athletes do not even exhibit serious concussion symptoms (it is important to note that this does not imply that less damage to the brain occurred). Many athletes will deny the presence of concussion symptoms (especially those in professional and collegiate sports) because they do not want to lose their position on a team. By returning to sports too early, athletes are extremely susceptible to concussions and are also at risk from the deadly Second Impact Syndrome (6).

    Moreover, a system for examining and clearing athletes is highly important so that the amount of athletes suffering second concussions can be limited. Each individual’s brain works differently, has the potential to be damaged in different areas, and probably adjusts and reroutes neuronal pathways post-damage differently. Thus, each concussed individual must be treated uniquely and athletic trainers and doctors must be familiarized with the current research, dangers, symptoms, etc. of concussions. It is also important for athletes to report their symptoms. While an athlete may desire to say they “feel fine” and keep playing throughout the season, will it really be worth it in the long run when they suffer permanent memory or cognitive deficits? Bryn Mawr College and many other colleges and professional sports teams require that each athlete take an “Impact Test” before they begin their athletic career. This computerized exam tests an individual’s reaction time, memory, and cognition. After an athlete suffers a concussion, they need to pass this test as well as they did when they were uninjured before they can be deemed fit for play. So far, this has reduced the number of athletes who suffer a second concussion or a more serious injury.

     In summary, concussions, or MTBIs, cause a permanent loss of gray matter in certain parts of the brain and, oftentimes, this can cause long-term psychiatric problems (like depression) and memory/cognition difficulties. It may be possible that different individuals who suffer similar impacts lose different amounts of gray matter in different parts of the brain because every brain is different. Also, it is likely the varying post-concussive symptoms and the varying severity of these is related to how each individual’s brain adapts to the destruction of previous neuronal pathways and reroutes them. Perhaps certain individuals are more innately impervious or able to adapt to brain damage following impact. Likewise, it will be interesting to find out whether the severity of depression in individuals who are already prone to depression increases post-concussion, as hyperactivity in areas associated with depression is observed in some individuals. The big question is, will there ever be an appropriate method of determining whether athletes are fit to play? Will post-MTBI individuals ever truly ready to go back on the field with all its flying objects and bodies? These are all topics that should be explored further to allow athletes and people in general a swifter, more individualized recovery so that they can function well in life (though, perhaps not necessarily in a competitive sport).

References
1.    CDC. "Concussion." Centers for Disease Control and Prevention, 08 Mar 2010. Web. 6 Apr 2010. <http://www.cdc.gov/concussion/signs_symptoms.html>.
2.    Chen, Jen-Kai, Karen M. Johnston, Michael Petrides, and Alain Ptito. "Neural Substrates of Symptoms of Depression Following Concussion in Male Athletes With Persisting Postconcussion Symptoms." Archives of General Psychiatry. 65.1 (2008): 81-89. Print.
3.    CNS. "Traumatic Brain Injury." Center for Neuro Skills. CNS, 2010. Web. 6 Apr 2010. <http://www.neuroskills.com/tbi/injury.shtml>.
4.    Levin, Harvey Stephen R.S, Stephen R. McCauley, Claudia Pedroza Josic, Corwin Boake, and Sharon A. Brown. "Predicting Depression Following Mild Traumatic Brain Injury." Archives of General Psychiatry. 62. (2005): 523-528. Print.
5.    McCrory, R., and S.F. Berkovic. "Second Impact Syndrome." Traumatic Brain Injury. University of Nebraska-Lincoln, 1998. Web. 2 Apr 2010. <http://tbi.unl.edu/savedTBI/sports/sis.html>.
6.    McFadden, Maureen. " Returning to sports too soon after a concussion could be deadly ." WNDU.com 03 Sep 2009: n. pag. Web. 6 Apr 2010.
7.    NIH. "Post Concussion Syndrome." Brain Injury Resource Center. National Institutes of Health, 1998. Web. 6 Apr 2010. <http://www.headinjury.com/faqpcs.htm>.
8.    van Reekum, Robert, Tammy Cohen, and Jenny Wong. "Can Traumatic Brain Injury Cause Psychiatric Disorders?." Journal of Neuropsychiatry and Clinical Neurosciences. 12.3 (2000): 316-327. Print.
9.    Wikipedia. "Major Depressive Disorder." Wikipedia. Web. 6 Apr 2010. <http://en.wikipedia.org/wiki/Major_depressive_disorder>.