Recognizing, treating and preventing this common injury
Traumatic brain injury (TBI) has been defined by the National Institute of Neurological Disorders and Stroke as “acquired brain injury caused by sudden trauma resulting in damage to brain tissue.”1,2
Mild traumatic brain injury more commonly referred to as concussion, is the most common form of TBI, accounting for 75% of all traumatic brain injuries.1 Concussion affects patients of all ages, most commonly occurring as a result of falls, motor vehicle accidents, assaults and recreational activities.2
Concussion leads to a variety of short-term physical, emotional, cognitive and sleep-related symptoms, as well as numerous potential long-term consequences.3In recent years, much attention has been focused on sport-related concussion, from the adolescent to professional level, and what can be done to aid in both the primary and secondary prevention of this common sports injury.3-7 Preventing concussion is an important goal of health professionals and those involved in athletics.
Definition & Pathophysiology
Concussion is defined as a traumatically-induced, transient disruption of normal brain function.
This occurs due to a rotational or acceleration/deceleration forces transmitted to the head, either as a result of a direct blow to the head, neck or face or a blow to another area of the body that is transmitted to the head.3,4,5
Brain injuries are typically classified as either focal or diffuse, and either primary or secondary. Concussion is considered to be a diffuse brain injury, as the entire brain is generally affected, as opposed to only the specific, direct area of injury causing symptoms. This type of injury is also classified as a secondary brain injury, meaning that the symptoms of concussion are a result of the pathophysiological events that occur after the moment of impact, as opposed to injury resulting from the trauma immediately and directly.3,6,7
The rotational and acceleration/deceleration forces in a concussion are believed to cause stretching and disruption of neuronal membranes.2,3 This allows for a massive efflux of potassium from the neuronal intracellular space to the extracellular space, triggering the release of glutamate. An excitatory neurotransmitter, glutamate subsequently prompts continued potassium release.
The depolarization of a massive number of neurons by this mechanism leads to the suppression of normal, physiologic neuronal activity. In an attempt to achieve homeostasis, sodium-potassium pump activity is increased, resulting in utilization of substantially more than normal amounts of cellular fuel in the forms of adenosine triphosphate (ATP) and glucose. As a result, lactate accumulates within the brain and cerebral blood flow is decreased, leading to an “energy crisis” in the brain.3
The massive efflux of potassium previously described also leads to an accumulation of calcium within neurons, which can interfere with oxidative metabolism and activate biochemical pathways that lead to catabolic processes, free radical accumulation, and cell death.3,8 These events lead to a hypometabolic state within the brain, which can persist for four weeks.3
Adolescents aged 15-19 years are one of the age groups most at risk for concussion, and sports injuries are the most common cause of concussion in this patient population.
The Centers for Disease Control and Prevention estimates that in sports alone 1.6-3.8 million concussions occur annually in the United States, accounting for 8.9% of sport-related injuries in high school athletes.1-4
Most of these reported injuries occur during participation in organized sports, specifically during competition rather than in practice.4 Concussion is most likely to occur during player-to-player contact; unsurprisingly, male athletes have the highest concussion risk while playing football, while female athletes are at greatest risk while participating in soccer.3,4 Specific positions within these and other sports that lend themselves to increased opportunities for player-to-player contact are also associated with an increased risk of concussion.4
A previous history of a concussion is the single greatest risk factor for sustaining a subsequent concussion, creating a 2-5.8 times increased risk, and a 6 times increased risk if the previous concussion was accompanied by loss of consciousness.4,9-11 This risk is greatest in the first 7-10 days following a concussion.4
While the reason for this profound increased risk is not fully understood, it is postulated that it may be due to the athlete’s style of play, the pre-existing, personal susceptibility of the athlete, including the athlete’s age, level of participation, and exposure time, and the brain’s increased susceptibility to concussion while recovering from previous concussion.4
In sports with comparable rules and exposure, females are more likely to sustain a concussion than males. Females also report greater numbers, severity and duration of symptoms of concussion compared to males.4,9 The reasons for these observations are not clear, but are thought to be due to differences in head-neck segment mass between males and females, as well as to differences in estrogen levels and cerebral blood flow that may influence the pathophysiology of symptom development and recovery.4
Younger athletes appear to be at an increased risk for concussion, potentially due to differing physiology of developing brains, but studies in athletes under the age of 15 are minimal.4,9
Specific genetic mutations have been thought to be associated with an increased risk of concussion, but studies of these mutations to date have failed to show a significant increased risk.4,9 A personal history of mood disorders, learning disabilities, attention disorders and migraine headaches have all been shown to be associated with an increased risk for concussion, as well as an increased risk for prolonged recovery time following an injury.4,9
Signs & Symptoms
Concussion can lead to a large variety of signs and symptoms in the physical, emotional, cognitive and sleep domains (Table 1).3,4,9
Headache is the most common symptom, followed by dizziness.4,9 While loss of consciousness is classically thought of as a prominent concussion symptom, this only occurs in 10% of all concussions.4
Athletes suffering from these symptoms after a rotational or acceleration/deceleration impact should receive further attention and care.3,4,9,12
As with any traumatic injury, immediate assessment of airway, breathing and circulation should be the top priority. If there is concern of cervical spine injury, the cervical spine should be stabilized and the patient should be transported to an emergency department immediately.3,4
If the patient is not being immediately transferred to an ED, a review of systems and physical examination should occur on the sidelines. Many concussion assessment tools exist, each with its own sensitivity, specificity and limitations.
The most commonly used scoring systems include the Maddocks Questions, the Standardized Assessment of Concussion, the Balance Error Scoring System, the modified Balance Error Scoring System, the Sport Concussion Assessment Tool 2 and the NFL Sideline Concussion Assessment Tool.4,9 Once the patient has been assessed, the concussion should be graded on a scale of 1-3 and immediate management should proceed accordingly (Table 1).2
After a suspected concussion, the patient should be evaluated by a medical professional, either in the ED or in an office setting. This evaluation should include a thorough past medical history, specifically concussion history, as well as a thorough history of the current concussion, including mechanism of injury, symptom course and scores from tests that may have been performed.3,4
A physical examination should be performed, with particular emphasis on the head and neck exam and the neurologic exam, including balance and cognitive testing.3 Depending on the timing of this evaluation, many symptoms may have begun to resolve and exam findings that once would have been positive will be negative. Balance, for example, generally returns to normal by day three post-concussion.4
Conventional neuroimaging, namely CT and MRI, do not show changes with concussion. As such, these tests are unnecessary, although one or both are often performed to rule out more serious processes.13
Neuroimaging should be performed if there is concern of more serious brain injury, such as in patients with severe or worsening symptoms including severe headache, seizure, difficult arousal, repeated emesis, lack of orientation or neck pain. Additionally, neuroimaging should always be performed in patients who lost consciousness for more than 30 seconds.3 CT is most often the neuroimaging test of choice as it superior to MRI in detecting hemorrhage and skull fracture. MRI, however, is better able to show contusion, petechial hemorrhage and white matter damage and may be utilized along with CT in some situations, such as if imaging is being obtained greater than 48 hours after the time of the injury, or if there is specific concern of white matter damage.3.4,13 More advanced techniques, such as functional MRI and PET scanning are currently only used in research.4
Neuropsychological (NP) testing, such as the Impact test, has gained popularity in concussion diagnosis and management. Administered via pencil and paper or, more commonly, via computer, NP testing aims to identify neurocognitive deficits that may not be elucidated by simple, standard neurologic exams and cognitive tests.4,9
NP testing is a tool that can aid in concussion management, but it cannot independently be used to diagnose a concussion or clear a patient to return to normal activity.3 Scores on NP testing can vary greatly among patients, so it is difficult to determine what results indicate concussion-related impairment. It has been suggested that to account for this, athletes should complete pre-season testing during pre-participation physicals and this score could then be compared to a score on testing performed following future concussion.
Physical and cognitive rest and prevention of a second head injury is the mainstay of treatment.4,9
Cognitive effort exacerbates concussion symptoms in many patients, at times even when symptoms are absent unless the patient is being cognitively exerted.3,4 Many athletes have difficulty with school while recovering from concussion, especially with foreign language and mathematics classes.3
As such, a period of “cognitive rest” is often recommended following concussion. This should be individualized to meet patient needs, but can include accommodations such as absences from school, shortened school days and extra time to complete homework and exams.3,4 The athlete should rest outside of school as well, avoid excess stimuli such as computers, television, video games and leisure reading.3
Just as return to cognitive exertion should be individualized and guided by symptoms, return to physical exertion should follow the same cues.2,14 As the brain is in the previously described “energy crisis,” the extra stress on the brain from physical exertion can be overwhelming, and can increase the risk of subsequent concussion and second impact syndrome.3
As such, ensuring athletes refrain from athletic and recreational activity until all symptoms have resolved is of paramount importance. When the athlete is free of symptoms and the neurologic exam is within normal limits, return to activity can be gradually attempted over days to weeks with the supervision of a licensed medical professional. If symptoms recur at any point, the athlete should rest before activity is again attempted.3,4,9,14
Little medical intervention is available for the management of concussion. There is no medication that can help with or speed recovery from concussion. However, some medications can be used to manage symptoms, where other medications are best avoided.4
Headache can be successfully treated with acetaminophen. Nonsteroidal anti-inflammatory drugs (NSAIDs) are also effective headache treatments, but due to a small risk of intracranial hemorrhage associated with NSAIDs use after head injury, these medications should be avoided.3,4
Sleep disturbances are common in concussion patients. While sleep can be induced with medication, such as benzodiazepines, sleep-inducing medications should be avoided in the short-term following concussion due to the cognition-clouding side effects of these medications that can be accentuated post-concussion.4
Anti-nausea medication should be avoided for the same reason, as further clouding cognition poses a greater risk to the patient than the benefit that is gained from the treatment. Use of these medications, such as meclizine, can be considered if symptoms are extremely severe and the benefit is thought to outweigh the risk.4
Antidepressant medications, such as selective serotonin reuptake inhibitors (SSRIs) could be effective for anxiety or depression symptoms, but as these medications take time to become effective, their use in immediate post-concussive management is limited, although they may have a greater role in the treatment of post-concussion syndrome.4 Stimulant medication that could be used to treat attention symptoms is generally not used for the same reason.4
Complications of Concussion
In most patients, symptoms of concussion resolve within 7-10 days.4 However, in some patients, symptoms persist for weeks to months.
The presence of three or more concussion symptoms persisting for greater than 7-10 days post- injury is defined as post-concussion syndrome and can consist of any of the physical, emotional, cognitive or sleep-related symptoms of concussion, although headache is the most common symptom.3,4,13 Development of post-concussion syndrome is not related to the number of previous concussions or the severity of the current concussion.
Risk factors for development of post-concussion syndrome include female sex, history of migraine and history of mood disorders or learning disorders.4,13 The mainstay of management of post-concussion syndrome is time. Due to the chronic nature of the symptoms, however, there is a greater role for the use of the medications previously discussed in the management of post-concussion syndrome as opposed to the immediate management of concussion.4,13
Second impact syndrome is a rare, but serious complication of concussion.9 As it occurs almost exclusively in patients under the age of 21, it is a particular concern in sports concussion patients.3,9 This syndrome occurs when a patient sustains a second concussion before he or she has fully recovered from a prior concussion, usually within two weeks of the original injury.
This second injury progresses rapidly and can result in loss of consciousness, respiratory failure, coma and death due to preexisting and progressing cerebrovascular dysregulation, which leads to vascular engorgement, metabolic changes and herniation of brain tissue.3,9 Preventing this devastating complication is an important reason to avoid premature return to play.9
Chronic traumatic encephalopathy (CTE) is a neurodegenerative disorder that is associated with a history of multiple concussions.4,9 The disease is characterized by protein accumulation in the brain that leads to executive dysfunction, memory impairment, depression and poor impulse control.4
This disorder does not occur in all athletes who have experienced multiple concussive or sub concussive impacts, so researchers suspect that there is a genetic component to this disease. However, there is a clear association between history of concussion and future development of CTE, so as there is currently no way to predict who is truly at risk based on genetics. All patients who have experienced multiple concussions are thought to be at risk for developing CTE.4,9 The exact number and severity of impacts to pose a risk is unknown.9
Another complication of concussion, includes chronic neurocognitive impairment (CNI), which is defined as cognitive deficits that occur immediately post-concussion and do not remit, or cognitive deficits that develop years following recovery from concussion that then persist. The risk for CNI increases with increasing number and severity of concussions.4
In 2009, following a devastating TBI in a young football player, Washington became the first state to enact a law pertaining to concussion in youth sports. Since that time, 44 states and Washington D.C. have passed similar laws.5,15
There is some variability between these laws, but most require at least 24 hours of rest, evaluation by a health professional before return to play and mandatory education for parents and coaches.
More time and research is needed to see the full effect of these laws. It is thought, however, that education could potentially reduce the number of concussions, while more stringent return to play guidelines and proper examination and treatment of athletes combined with education could help prevent subsequent and potentially more dangerous concussions.5,15
Helmets and headgear are unquestionably effective in reducing biomechanical forces in head injury, as well as reducing the risk of scalp lacerations, skull fractures and intracranial bleeds. They have not, however, been shown to reduce the risk of concussion. With advancing technology, prevention of concussion is a major goal of helmet manufacturers.4,9,16,11
Mouth guards are also indisputably effective in preventing peri-oral and dental injuries, but have not been found to reduce the risk of concussion.3,4 Protective equipment can actually increase the risk of concussion in some situations, as it creates a false sense of security and safety that can prompt an athlete to take excessive risks.4
Some specific genes have been thought to be associated with an increased risk of concussion. However, as none of these mutations have shown a substantial increased risk of concussion, genetic screening of athletes is not currently recommended or thought to be an effective method for preventing concussion.3
Certain sports and more specifically certain maneuvers, techniques and plays within those sports are associated with greater concussion risk. Implementing rules that restrict these types of plays allowed in certain sports can decrease concussion risk.4,16
Eliminating body checking in youth hockey, modifying kickoff rules and banning spear tackling in football, and prohibiting elbow to head in soccer has greatly reduced the number and severity of concussions in these sports.4,16 Additional analysis and rule changes could help to further reduce athlete’s risks of concussion in these and other sports.16
Education of athletes, parents and coaches is still the best tool to protect against concussion.3,4,16 Misconceptions about the symptoms, seriousness and proper management of concussion are very common. Helping those on the sidelines to better identify at-risk athletes and to identify and diagnose concussion immediately after injury occurs is the first step to improving care.
Making those involved aware of the dangers and repercussions of this common injury can lead to improved compliance with safety rules and regulations, both before and following a concussion, potentially reducing both the number of and complications resulting from concussions.3,4,16
Preventing concussion is a major goal of many sports organizations and healthcare providers.1,5,16 With updated legislation, improved technology, modified play regulations and continued education, risk of concussion can be reduced and safety of athletes can be improved.3,4,15,16
- Centers for Disease Control and Prevention. CDC grand rounds: reducing severe traumatic brain injury in the United States. Morb Mortal Wkly Rep. 2013;62(27):549-52. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6227a2.html
- Mason C. Mild traumatic brain injury in children. Pediatr Nurs. 2013;39(6):267-82.
- Halstead ME, et al. American Academy of Pediatrics. Clinical report–sport-related concussion in children and adolescents. Pediatrics. 2010;126(3):597-615. doi: 10.1542/peds.2010-2005.
- Harmon KG, et al. American medical society for sports medicine position statement: concussion in sport. Br J Sports Med. 2013;47:15-26. doi: 10.1136/bjsports-2012-091941
- Harvey H. Reducing traumatic brain injuries in youth sports: youth sports traumatic brain injury state laws, January 2009-December 2012. Am J Public Health. 2013 Jul;103(7):1249-54. doi: 10.2105/AJPH.2012.301107
- Andriessen TM, et al. Clinical characteristics and pathophysiological mechanisms of focal and diffuse traumatic brain injury. J Cell Mol Med. 2010;14(10):2381-92. doi: 10.1111/j.1582-4934.2010.01164.x.
- Tran L. Understanding the pathophysiology of traumatic brain Injury and the mechanisms of action of neuroprotective interventions. J Trauma Nurs. 2014;21(1):30-5. doi: 10.1097/JTN.0000000000000026.
- Werner C, Engelhard K. Pathophysiology of traumatic brain injury. Br J Anaesth. 2007;99:4-9.
- King D, et al. Assessment, management and knowledge of sport-related concussion: systematic review. Sports Med.2014;44(4):449-71. doi: 10.1007/s40279-013-0134-x.
- Braine M, et al. Traumatic brain injury in children part 1–initial assessment and management. Br J Of Sch Nurs. 2013;8(4):175-9.
- Braine M. Traumatic brain injury in children part 2: Recovery process and outcomes. Br J Of Sch Nurs. 2013;8(7):330-5.
- Hyatt K. Mild traumatic brain injury. Am J Nurs. 2014 Nov;114(11):36-42. doi: 10.1097/01.NAJ.0000456426.79527.9b.
- Giza CC, et al. Summary of evidence-based guideline update: evaluation and management of concussion in sports: report of the Guideline Development Subcommittee of the American Academy of Neurology.Neurology. 2013;80(24):2250-7. doi: 10.1212/WNL.0b013e31828d57dd.
- Echemendia RJ, et al. Developing guidelines for return to play: consensus and evidence-based approaches. Brain Inj. 2015;29(2):185-94. doi: 10.3109/02699052.2014.965212.
- Bachynski K, et al. Youth sports & public health: framing risks of mild traumatic brain injury in American football and ice hockey. J Law Med Ethics. 2014;42(3):323-33. doi: 10.1111/jlme.12149.
- Goldberg DS. Mild traumatic brain injury, the National Football League, and the manufacture of doubt: an ethical, legal, and historical analysis. J Legal Med. 2013;34(2):157-91. doi: 10.1080/01947648.2013.800792.