The primary end point for sideline assessment is to determine the probability that an athlete has sustained a concussion. If the athlete is deemed unlikely to have had a concussion, continued participation should be safe. If the evaluation indicates a definite or probable concussion, the athlete should be removed from participation with no same day return to play. Sport-related concussion is an evolving injury and should be serially reassessed when suspected.
An office assessment should include a comprehensive history and neurological examination including details of injury mechanism, symptom trajectory, neurocognitive functioning, sleep/wake disturbance, ocular function, vestibular function, gait, balance, and a cervical spine examination. The utility of sideline neurocognitive and balance assessments to identify concussion decreases as early as 3 days after injury.41 Symptom checklists can be useful to track symptom trajectory. To confirm the diagnosis of SRC, there should typically be a clear mechanism consistent with concussion; characteristic signs, symptoms, and time course of concussion; and no other cause for the constellation of clinical findings. It is not unusual for symptoms, signs, and testing to normalize by the time an office visit occurs,44 in which case the visit should focus on recommendations for safe return to school and sport. If computerized neurocognitive tests were performed before injury, they are often repeated during this assessment period.
There is a need for definitive, objective, and clinically useful tools for the diagnosis of concussion. This interest has led to innovation and fast-paced changes with the ongoing need for refinement and validation of these efforts.
Other sideline evaluation tools have been developed, including tests of vestibular–ocular function and reaction time. Physical examination components of the VOMS are becoming more frequently used in the office setting, but the role of formal VOMS testing on the sideline has not yet been studied. The King-Devick (KD) Test is a proprietary, timed saccadic eye movement test requiring individuals to quickly read numbers aloud.28 The KD requires a baseline test as well as an understanding of potential learning and practice effects to be useful. Simple reaction time as a sideline screen has also been studied using a dropped weighted stick.47 Further research including larger numbers and control subjects is needed for these tests.
Other technologies such as app-based measures of reaction time, eye trackers, postural stability, speech pattern, quantitative electroencephalography, and various abbreviated neurocognitive tests are being developed. Some are available on portable electronic platforms with the ability to share information with multiple users. These newer technologies do not have sufficient research to establish their utility. The mention of all of these sideline tools does not imply AMSSM endorsement.
Current impact sensor systems indirectly monitor linear and angular acceleration forces to the brain; however, they may not consistently record head impacts or forces transmitted to the brain. Neither a device nor a specific threshold measure of force or angular acceleration can be used to diagnose concussion.38,48 Some athletes experience high forces with no clinical symptoms of concussion, and some athletes sustain a concussion at much lower impact forces, making current impact measures a poor predictor of SRC.49 The number, location, density, and individual thresholds of head impacts may be important parameters. At this time, impact monitors are a research tool requiring additional study and are not validated for clinical use in the diagnosis or management of SRC.
Head computerized tomography (CT) is rarely necessary in the evaluation of SRC but should be used when clinical suspicion for intracranial bleeding or macrostructural injury exists. Intracranial bleeds are rare in the context of SRC, but can occur, and CT is the standard evaluation tool for these and other suspected neurosurgical emergencies in acute and critical care. Conventional brain magnetic resonance imaging (MRI) is not commonly used in the evaluation of concussion but may have value in cases with atypical or prolonged recovery. Newer, advanced multimodal MRI technologies (eg, diffusion tensor imaging, resting state functional MRI, quantitative susceptibility imaging, magnetic resonance spectrography, and arterial spin labeling) are being studied in research protocols aimed at understanding the neurobiological effects and recovery after SRC.50 Additional research will be required to determine the clinical utility of advanced neuroimaging in the setting of SRC.
The role of fluid biomarkers (blood, saliva, and cerebrospinal fluid) in the diagnosis of SRC is also under active investigation.50 Proteomic markers of injury and recovery in more severe forms of civilian neurotrauma and traumatic brain injury have shown some promise; however, in recent systematic reviews, the overall level of evidence is low for using fluid biomarkers for diagnosis of SRC.50 Fluid biomarkers have potential for informing the pathophysiology of concussion and neurobiological recovery, but more research is required to determine their clinical utility.50 Recent Federal Drug Administration (FDA) approval of a two-protein brain trauma indicator with glial fibrillary acidic protein and ubiquitin carboxy-terminal hydrolase L1 (UCHL1), and clinical use of S100 calcium-binding protein β (s100β) in Europe, show promise for ruling out intracranial bleeds and structural damage to reduce utilization of head CTs in the emergency department setting. At this time, none of these tests has a role in the diagnosis or management of SRC.
There is currently no scientific support for genetic testing in the evaluation and management of athletes with SRC, and additional research is needed to determine how genetic factors influence risk of injury and recovery after SRC.50
In this section the role of rest, physical activity and nutraceuticals are discussed.
Prescribed cognitive and physical rest has been the mainstay of treatment for the past several decades despite insufficient evidence to support this approach.59,60 Earlier animal data suggested that uncontrolled or forced early exercise is detrimental to recovery61–63; however, recent data in aerobically trained animals given early access to exercise showed improved outcomes compared with no or delayed exercise or to social isolation.64 In human studies, strict rest after SRC slowed recovery and led to an increased chance of prolonged symptoms.65,66 Total rest, that is, “the dark room” or “cocoon therapy,” may have detrimental effects similar to social isolation effects seen in animal studies and is no longer recommended.3,51 Consensus guidelines endorse 24 to 48 hours of symptom-limited cognitive and physical rest followed by a gradual increase in activity, staying below symptom-exacerbation thresholds.3 Further research is needed to define the role of prescribed rest in recovery.
Postconcussion syndrome or disorder are terms that have been frequently used to describe patients with lingering symptoms after a sport- or recreation-related concussion, but often those patients do not meet diagnostic criteria for these diagnoses. A preferred term is persistent postconcussive symptoms (PPCS), defined as symptoms that persist beyond the expected recovery time frame (>2 weeks in adults, >4 weeks in children).44 Persistent symptoms do not necessarily represent ongoing concussive injury to the brain. It is not unusual for common symptoms to be inappropriately or mistakenly attributed to concussion; therefore, it is critical to understand pre-existing or coexisting symptoms and conditions in the evaluation of PPCS.
Recent systematic reviews have advocated including vestibular, oculomotor, psychological, sleep, cervical and autonomic nervous system evaluations in the assessment to facilitate individualized and targeted management of PPCS.77
Activity and exercise that does not exacerbate symptoms are recommended for those with PPCS. A formal symptom-limited aerobic exercise program has been shown to be safe and improve resolution of persistent symptoms compared with controls and should be considered in athletes with symptoms lasting longer than expected.78–80 The Buffalo Concussion Exercise Treatment Protocol, a progressive subsymptom threshold aerobic exercise program based on systematically establishing the level of exercise tolerance on the Buffalo Concussion Treadmill Test, is the most studied controlled exercise program.81 It is ideal for those with PPCS to be evaluated by a provider or multidisciplinary team with expertise in complicated concussion management.
Athletes with migraine/headache should be evaluated for underlying headache disorders, cervical dysfunction causing headache, and other possible contributors, and treated appropriately with nonpharmacologic and pharmacologic treatments.77 Vestibular therapy should focus on specific deficits identified and use an “expose-recover” model performed by clinicians with expertise in vestibular rehabilitation.51,82 There is preliminary evidence that addressing cervical spine and/or vestibular dysfunction with a targeted physical therapy program improves outcomes in those with PPCS.83,84 Cognitive work should be modified or limited to that which does not exacerbate symptoms.60 In athletes with sleep disturbances after an SRC, sleep hygiene should be addressed, sleep monitored, and treated with nonpharmacologic or pharmacologic strategies.85 Individuals experiencing psychological symptoms such as irritability, sadness, and anxiety should be evaluated and offered appropriate treatment. A collaborative care model including cognitive behavioral therapy can improve outcomes in those with PPCS.86
In addition to return to learning and sporting environments, older athletes may need to return to driving, where subtle deficits could compromise safety. Most sports medicine physicians do not counsel athletes with SRC about driving.90 Driving is a complex process involving coordination of cognitive, visual, and motor skills as well as concentration, attention, visual perception, insight, and memory that can all be affected by SRC.90 Little is known about the risk of driving after SRC, but preliminary data suggest some impairment exists when concussion patients report they are asymptomatic.91 Currently, no widely accepted return to driving protocols exist; however, in athletes who drive, discussing the potential risks and harms is appropriate.
Chronic traumatic encephalopathy (CTE) and other neurodegenerative diseases have been described in former athletes with a history of concussion or repetitive head impact exposure, typically accompanied by behavioral change. The incidence and prevalence of CTE in the general population, in former athletes, or in former athletes with a history of concussion or repetitive head impact exposure is unknown. A cause and effect relationship between postmortem CTE changes and antemortem behavioral and cognitive manifestations has not been demonstrated, and, asymptomatic players have had confirmed CTE pathology at autopsy.105,106 It is also unknown whether CTE is a progressive disease and whether tau deposition is the cause of CTE or a byproduct or marker of a disease.107
The expression of CTE-associated symptoms may be related to impact load and type, duration of career, underlying genetic factors, or other lifestyle behaviors including alcohol, drug and anabolic steroid use, general health, psychiatric disease, and other factors. Some retrospective studies have reported increased risk of neurodegenerative disease in former professional football players; however, former high school football players do not show a higher prevalence of neurodegenerative disease when compared with nonfootball peers.108,109 The most widely described risk factor to date is extensive exposure to both multiple concussions and repetitive head impacts, but the degree of necessary exposure is likely specific to the individual and subject to multiple modifying risk factors.110 Athletes and former athletes who present with neuropsychiatric symptoms and signs that have been ascribed to CTE should be evaluated for potentially treatable comorbid conditions that share symptoms and not be assumed to have CTE.111
Subconcussive or nonconcussive head impacts have been discussed as an entity apart from concussion history that may create risk of long-term neurologic sequelae. Subconcussive impacts are defined as transfer of mechanical energy to the brain causing presumed axonal or neuronal injury in the absence of clinical signs or symptoms.112 It is unclear whether a biomechanical threshold or other factors lead to injury or whether this entity qualifies as injury, as it does not seem to be associated with neuropsychological changes.113 Although subconcussive impacts have been associated with CTE, the short- and long-term effects of repetitive head impacts, similar to SRC, cannot be accurately characterized using current technology. Future research will depend on developing technologies that can assess brain changes after repetitive asymptomatic head trauma in living subjects.
Prevention of SRC is ultimately more effective in reducing the burden of this condition than any treatment, and although primary prevention of all SRC is not possible, measures to decrease the number and severity of concussions are of value. Rule changes, enforcement of existing rules, technique changes, neck strengthening, and equipment modifications have been the primary focus of prevention. There is moderate evidence that delaying the introduction of body checking in youth hockey reduces concussion rates.115–117 The effectiveness of rule changes in youth soccer and football to reduce concussion incidence is not clear; however, there is initial evidence that practice modification and changes in tackling technique may reduce injury.118,119 There is conflicting evidence regarding mouthguards and concussion reduction, and mouthguards should primarily be used for preventing dental trauma.117 Helmets prevent skull trauma and intracranial bleeding, but their protective effects for concussion are less pronounced. Some football helmet designs have improved the ability to absorb force, but it is unknown whether this will reduce concussion incidence. Studies of headgear in other sports have produced mixed results. Player behavior can change when athletes wear new or “improved” protective equipment, encouraging a more aggressive style of play, potentially increasing the risk of injury.
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