Definitions of Sports Concussion, Initial Diagnosis, and On-Field Evaluation

Leah G. Concannon, MD

Brian C. Liem, MD

Stanley A. Herring, MD

Ronnie Barnes, ATC

Leigh J. Weiss, ATC

Dr. Herring or an immediate family member had served as an unpaid consultant to X2Biosystems; has stock or stock options held in Vicis; and serves as a member of the editorial board of The Physician and Sports Medicine. Neither of the following authors nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Concannon and Dr. Liem.

Sports concussions account for 5% to 18% of all sports-related injuries in high school and collegiate athletes,¹^,²^,³ with an estimated 1.6 to 3.8 million sports-related concussions per year,⁴ which is probably low. The annual incidence of sports concussions is apparently rising, but some attribute this trend to an increased awareness and reporting by athletes and healthcare professionals.⁵ The greatest number of concussions occur in high school and collegiate football, with a rate of 0.60 per 1000 athletic exposures.²^,⁵^,⁶^,⁷ In one study of high school and collegiate football players, 14.7% of concussed players sustained a second injury during the same season.⁶ Among high school female athletes, soccer players have the highest incidence of concussion.²^,⁵ Although the absolute number of concussions is highest in football, the rate of concussions is higher in women’s collegiate soccer than in collegiate football (0.63 vs. 0.61 per 1000 athlete exposures).²

Definitions

The definition of a sports concussion continues to evolve. The Fourth International Conference on Concussion in Sport, held in Zurich in 2012, described a concussion as a subset of traumatic brain injury defined as a complex pathophysiological process affecting the brain induced, by biochemical forces.⁸ Four key features help to further clarify this definition:

May result from a direct blow to the head, face, neck, or body with “impulsive” force transmitted to the head
Rapid onset of short-lived impairment of neurologic function that resolves spontaneously but may progress over minutes to hours
Injury is largely functional rather than structural, which generally results in normal standard neuroimaging studies
Concussion results in a graded set of clinical and cognitive symptoms. These symptoms typically resolve in a sequential course, but some individuals may have a more prolonged course.⁸

Diagnosis

Concussion remains a clinical diagnosis. Assessment includes recognition of mechanism of injury, assessment of symptoms, evaluation of cognitive function, and balance testing. Screening neurologic and physical examination are also performed to rule out other injuries, including more severe brain injury. Because concussion is largely a functional deficit, standard imaging, including CT and MRI, is routinely normal and does not rule out concussion.⁹ However, CT may be used in the acute setting to evaluate for intracranial hemorrhage or skull fracture.¹⁰ MRI may be better in the subacute setting to identify evidence of diffuse axonal injury. Magnetic resonance spectroscopy, diffusion tensor imaging, and functional MRI are promising imaging modalities that may be capable of detecting acute subtle neuropathologic changes, but further research is needed to determine their application in the clinical setting.¹¹

An athlete suspected of concussion may report or display one or more elements from five clinical areas:
(1) symptoms, (2) physical signs, (3) behavioral changes, (4) sleep disturbance, and (5) cognitive impairment.⁸

Symptoms

Symptoms experienced in a concussion can be divided into three main categories: somatic, cognitive, and affective. The most common somatic symptom is headache, reported in up to 80% to 90% of concussed athletes.⁶^,¹² Other somatic symptoms include nausea, dizziness, blurred vision, fatigue, and neck pain. Cognitive complaints can present as difficulty concentrating and remembering, confusion, feeling “foggy,” and slowed down. Athletes may also have affective changes such as emotional lability, irritability, and anxiety.

Physical Signs

Physical signs may include loss of consciousness (LOC) and amnesia, but it is important to note that LOC is not necessary for the diagnosis of concussion. Studies have shown that only 4–8% of athletes diagnosed with concussion suffer LOC.⁶^,¹² There is conflicting evidence on whether or not the presence of LOC is associated with prolonged symptom duration.¹³^,¹⁴

Behavior Changes

Changes in behavior such as increased irritability or depressed mood may be evident in a concussed athlete. A study by Kontos et al found that concussed high school and college athletes had a statistically significant increase from baseline in reported depression symptoms 2, 7, and even 14 days after injury.¹⁵

Sleep Disturbance

Sleep disturbance in concussed athletes is common and may be caused by a neurophysiologic injury. In a study comparing concussed patients versus those with only orthopedic injuries, there was a statistically significant greater number of concussed individuals who reported difficulties with sleep initiation, frequent awakenings, increased sleep duration, and daytime sleepiness.¹⁶

Cognitive Impairment

Cognitive impairment is a frequent finding in concussed athletes. The areas of neurocognitive functioning most affected include attention and concentration, short-term memory, processing speed, and problem solving.¹⁷ Studies suggest that recovery of cognitive deficits generally occurs within 3 to 7 days.¹⁸ However, in 18% of athletes, recovery can last beyond 7 days.¹⁹ It is important to note that in some cases, cognitive recovery may not occur until up to 2 to 3 days after symptom resolution.¹⁹ Therefore, it is important to not rely only on the athlete’s symptom reporting when determining timing of return to play (RTP). The Standardized Assessment of Concussion (SAC) is a well-validated sideline tool used to evaluate an athlete’s cognitive function immediately after a suspected concussion.²⁰ It includes assessments of orientation, immediate memory, concentration, and delayed recall.

Assessment Tools

A standardized instrument used to help assess all of the above is the Sports Concussion Assessment Tool version 3 SCAT3 published in 2013, an update to the SCAT2 published in 2009 (Figure 24-1).²¹ A separate SCAT3 for children 12 years and younger has also been published to address differences in symptom reporting by children compared with adults (Figure 24-2).²² The SCAT3 combines several concussion assessment measures and includes seven measures: Glasgow Coma Scale score, modified Maddock’s questions for orientation, concussion symptom checklist, standardized assessment of concussion (SAC) to assess cognition, neck examination, modified Balance Error Scoring System (mBESS), and coordination testing. It takes approximately 8 to 10 minutes to administer the SCAT3 which is usually performed on the sideline or in the locker room. By combining the various concussion assessments into one tool, the goal is to improve the sensitivity and specificity of concussion diagnosis. The SCAT2 was found to have high sensitivity (83%) and specificity (91%) for concussion when using a cutoff score of 74.5.²³ However, there have been no similar studies yet published on the SCAT3 nor the Child-SCAT3. Comparison of sideline SCAT3 should be made to a baseline (preseason) assessment if available.

The National Football League (NFL) sideline concussion tool is similar to the SCAT3 with the additional component of six “No Go” criteria (Figure 24-3).²⁴ These criteria are not specific to football and can be used in any sport. If an athlete exhibits any one of the six “No Go” criteria outlined in Table 24-1, he or she is presumed to have sustained a concussion and prohibited from RTP in the same game or practice.

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