Update on Sport-Related Concussion

Concussion in sport is an evolving area of medicine that continues to garner significant attention. Recent literature suggests that an estimated 135,000 to 300,000 athletes in the United States will seek medical care for concussion each year, regardless of the sport.^1-3 The incidence of concussion varies based on the sport. In the National Football League, for example, it is estimated that 61.7 concussions occur per 100 games.⁴ However, it is difficult to estimate concussion rates across sports accurately for several reasons, including the continued lack of medically trained personnel at all events, the underreporting of symptoms by potentially concussed athletes, and the inherent false-positive and false-negative rates associated with a concussion diagnosis, which is complex by nature and coexists with several medical conditions that produce similar clinical presentations.^3,5,6 Therefore, it is important for clinicians to keep up-to-date on concussion diagnosis and management to avoid the common pitfalls.

The most up-to-date approach to concussion evaluation and diagnosis begins with careful consideration of the suspected mechanism of injury, by video if available or by in-depth discussion. In cases of suspected sport-related concussion, it is also extremely important to recognize that 2 distinct medical decisions exist, requiring 2 differing approaches. The first is the “in-event” or sideline decision that is made for the athlete’s safety. This is essentially a triage decision, resulting in removal from participation, predicated on a reasonable suspicion of injury. The second medical decision is the diagnostic one, which should be considered carefully during clinical follow-up, which must include a thorough medical history and neurologic examination. As with all areas of medicine, a comprehensive and carefully crafted differential diagnosis must then be created to account for additional and alternative pathologies.

Concussion Defined

As with other areas of neurologic pathology, such as central nervous system ischemic events, it is important to recognize the difference between the underlying pathology of concussion and the clinical syndrome produced from that pathology. Because a large portion of the most common clinical symptoms and findings related to concussion, such as headache, dizziness, and balance difficulties, are nonspecific as to cause, it is most prudent to use the term “concussion” to refer to pathophysiologic changes. One clear clinically useful definition of concussion is a transient physiological condition brought on by exposure to a biomechanical force resulting in changes in network function, related primarily to membrane dysfunction and fluctuations in ion concentrations.

This underlying pathophysiology may produce direct clinical effects, such as loss of consciousness, memory dysfunction, or disorientation; or secondary effects related to the nervous system’s response to the primary injury. At the same time, as is discussed in greater detail in the following sections, the clinician must also realize that many presenting clinical effects may be the result of concurrent pathologies related to the biomechanical force in question.

Evaluating the Impact

Because of the nonspecific nature of concussion symptoms, accurate diagnosis must begin with careful consideration and estimation of the biomechanical force the brain likely experienced as a result of the impact in question.⁷ One useful approach is to categorize the mechanism of injury using the Kutcher Clinic Scale, a 3-tiered classification system allowing for general categorization of impact force events based on likely clinical outcome as it relates to concussion (Table 1).

Of course, such categorization requires a working familiarity with the sport in question. However, when applied, the Kutcher Clinic Scale may help facilitate the development and application of an accurate differential diagnosis initially based on the amount of force the athlete experienced. Given that a person may experience symptoms after an impact for several reasons other than concussion,^5,8 the ranking of impact force helps clinicians improve the diagnostic certainty of concussion.

Triage Decision versus Concussion Diagnosis

When performing a concussion evaluation during any athletic event, the initial decision is always focused first on athlete safety. The final diagnosis of concussion, as well as any concurrent pathology, is not required at the time of the initial evaluation and often is deferred until later in the clinical course. There are many signs and symptoms that raise the suspicion of concussion (Table 2), but many of these are nonspecific, such as headache, nausea, dizziness, and photophobia, and may represent alternative pathology.⁵ Several concussion assessment tools have been developed (e.g., SCAT5, SAC, and BESS) that may be implemented to help a clinician during the initial evaluation of suspected concussion, providing a standardized screening framework for collecting important early clinical information and making initial triage decisions. It is important to understand these metrics do not diagnose concussion and should not be used as a substitute for the necessary comprehensive clinical decision-making process.

On occasion, concussion can be diagnosed reliably based on certain initial presenting findings, such as a clear loss of consciousness or seizure.⁹ However, even in these cases, it is important for the clinician to develop a differential diagnosis to consider concurrent pathologies (Figure 1). The on-field decisions made after an impact are made for the athlete’s safety but also must allow for the further development of a differential. In this way, if concussion is suspected to any reasonable degree, based on the mechanism of injury, the clinical syndrome produced, or both, the athlete should be removed from participation immediately and evaluated. After the evaluation, if any suspicion of concussion remains, the athlete should not return to participation until either concussion has been ruled out or the concussion has been determined to have resolved.

Diagnostic Certainty: Clinical History and Examination

After the initial triage decision, a comprehensive clinical history and neurologic examination are essential to providing diagnostic clarity. At this point, previous brain health baseline evaluations may be useful, incorporating a detailed neurologic history including migraine; sleep, mood, or attention disorders; and other common neurologic concerns. A detailed family history and a complete previous neurologic examination are essential components that often aid both diagnosis and injury management.

When developing the differential diagnosis, the mechanism of injury and the clinical presentation should be used together to determine the likelihood of concussion. The diagnosis of concussion then should be categorized further as possible, probable, or definite, as described by Kutcher and Giza.⁵ An important consideration when an individual sustains a biomechanical force that may cause concussion is that other systems also may have been affected (Figure 1). Most people diagnosed with concussion experience additional injury, referred to as “concussion-plus” (Table 3). Traumatic migraine and cervical muscle strain commonly are concurrent with concussion.⁵ It is critical that these additional areas of injury are recognized and treated appropriately. This highlights the importance of a differential diagnosis as these alternatives may help explain athletes’ ongoing symptoms after concussion.

Concussion Management

Whereas definite or probable concussion diagnoses are clear indications for the application of specific concussion management principles, it should be recognized that possible concussion diagnoses do not automatically trigger the same approach. Rather, these cases should be considered individually, taking into account the available medical resources, such as a dedicated athletic training staff, ability for efficient clinical follow-up, and access to athletic tools and facilities for further sport-specific evaluation.

Once the decision has been made to treat the athlete as if concussion is present, initial management focuses on reasonable clinical observation to screen further for additional intracranial pathology. Although somewhat incident-specific, this typically means the individual should be in an observational setting, with a supervising adult, for 4 to 5 hours after the suspected injury. During this time, mental status and other basic neurologic function should be monitored carefully. Signs of declining level of consciousness or focal neurologic findings warrant an emergent evaluation. Other considerations for initiating an emergency response include, but are not limited to, seizure and persistent vomiting.

For the initial 24 hours of concussion management, anti-inflammatory medications should be avoided. Aceta-minophen may be used. The individual should avoid activities and environments that exacerbate symptoms significantly. However, care should be given to avoid overresting. After 48 hours, people with concussion typically can tolerate a gradual return to academic, physical, and social activities. This process should be monitored carefully, with the individual being taken through a progressive series of stages based on the specific clinical presentation, medical history, and typical activities. In the end, the goal of this process is to challenge the individual’s brain safely and gradually, while avoiding the introduction of the significant risk of reimpact activities. Other considerations during concussion management include a direct and coordinated approach to supporting sleep, mood, and headache, often with the use of medications.

Summary

Concussion related to sport is a complex field that requires a comprehensive, thoughtful approach to diagnosis and management. The preferred method begins with evaluation of the impact sustained by the athlete either through video or in-depth discussion. The impact then can be categorized as Kutcher Clinic Scale level 1, 2, or 3 based on the amount of biomechanical force experienced by the brain. When evaluating acute concussion during competition, the initial triage decision is made for athlete safety. The diagnosis of concussion is established during follow-up clinical visits with in-depth medical history, neurologic examination, and consideration of additional pathology, leading to different levels of diagnostic certainty. Concussion remains a clinical diagnosis, best obtained through a methodical approach including a broad differential diagnosis and acknowledgment of concurrent pathology.