Sideline evaluation of concussion

INTRODUCTION — Concussions are common, but complex, traumatic brain injuries seen in athletes of all ages and skill levels in a wide variety of athletic settings. Given the variability of the clinical presentation associated with concussion, it is important that team physicians and other clinicians responsible for the care of athletes perform a systematic and comprehensive sideline evaluation of each athlete with a suspected concussion.  

This topic reviews the risk factors, clinical presentation, sideline evaluation, and initial management of adolescent and adult athletes with a sports-related concussion. More detailed discussions of mild traumatic brain injury, concussion in children, and trauma assessment are provided separately:

●Adult and older adolescent with concussion (see "Clinic-based evaluation of sports-related concussion in adolescents and adults" and "Clinic-based management of sports-related concussion in adolescents and adults" and "Acute mild traumatic brain injury (concussion) in adults" and "Postconcussion syndrome")

●Child and young adolescent with concussion (see "Minor blunt head trauma in infants and young children (<2 years): Clinical features and evaluation" and "Concussion in children and adolescents: Clinical manifestations and diagnosis" and "Concussion in children and adolescents: Management")

●Trauma and collapsed athlete: (see "Evaluation of the collapsed adult athlete" and "Initial management of trauma in adults" and "Trauma management: Approach to the unstable child")

DEFINITION — A concussion is a complex, trauma-induced pathophysiological process affecting the brain. The biomechanical forces involved in the trauma (eg, acceleration, deceleration, rotation) can injure the brain via a direct blow to the head, face, or neck, or via a blow to the body that transmits force to the head (eg, whiplash). The ensuing brain disturbance is due to neurometabolic dysfunction, which manifests in a wide variety of symptoms and signs that may or may not include loss of consciousness [1-3]. No gross structural abnormalities are seen with conventional neuroimaging.

It is important to note that while a concussion typically manifests with rapid onset of short-lived neurologic dysfunction, in some cases, development of signs and symptoms of concussion can be delayed minutes to hours [1]. Detailed discussions of the definitions, pathophysiology, and epidemiology of concussion are provided separately. (See "Acute mild traumatic brain injury (concussion) in adults", section on 'Pathophysiology'.)

ACUTE CONCUSSION EVALUATION — Evaluation and diagnosis of concussion remains a clinical exercise. At this point, there is no compelling evidence supporting one specific test, tool, biomarker, imaging study, or protocol to definitively diagnose or exclude a concussion. In the absence of such evidence, use of a consensus-derived, multimodal concussion assessment tool, such as the sixth edition of the Sport Concussion Assessment Tool (SCAT6), is recommended as the framework for a sideline concussion evaluation [4].

As part of the acute sideline evaluation, we recommend gathering all available information about the athlete and their injury, including: mechanism of injury, immediate clinical presentation, concussion risk factors, and initial treatment rendered (if any).

RISK FACTORS — Factors associated with an increased for concussion sustained during sport or more severe symptoms from such a concussion are discussed in detail separately. (See "Clinic-based evaluation of sports-related concussion in adolescents and adults", section on 'Risk factors'.)

Risk factors include the following:

●Previous concussion  

●Younger age  

●Participation in a high risk sport (collision or combat sport)

●Female sex  

CLINICAL PRESENTATION

Mechanism of injury — The relationship between mechanisms of injury and concussion risk is the subject of ongoing research and debate [4-8]. Nevertheless, we believe the mechanism is an important piece of information when a reliable history or a video of the injury can be obtained. With the proliferation of video technology in smartphones and other devices, video review of the mechanism of injury has become more widely available for sideline evaluation and subsequent assessment at all levels of sports.

Location and magnitude of impact — Data collected to determine whether there is a correlation between the location and force of impact and a diagnosis of concussion are primarily from studies involving head impact sensors. Although individual studies of athletes using such sensors have concluded that higher forces from both linear acceleration (particularly greater than 100 G) and rotational acceleration (greater than 5500 m/second) are associated with an increased incidence of concussion [9-13], a 2017 systematic review found that the available studies have not established a clinically significant relationship between impact location or impact magnitude and resultant concussion [1,4]. Overall, head impact sensors have not been shown to provide useful information for sideline clinicians and are not recommended as a component of the sideline evaluation.

Studies of video review in acute sideline evaluation for concussion show promise, but are limited and of low quality [4,14]. The practice of video review and screening for signs of concussion is used in some professional and high level contact and collision sports, such as American football, hockey, and rugby.

High-risk mechanisms

●Double hit – Although high quality evidence is lacking, in the authors' experience a "double-hit" impact often leads to more severe injury. An example of such an impact might involve an ice hockey player who is checked by an opponent whose shoulder strikes the player's head (first hit), followed immediately by a fall in which the checked player's head strikes the ice (second hit).

●Trauma with rotational forces – Shearing forces from a rotational blow to the head are associated with an increased likelihood of concussion, and often more severe dysfunction with prolonged recovery [11-13]. An example would be an American football player spun forcefully to the turf causing the occiput to strike the ground as it is moving in an arc.

●Second hit – A previous blow to the head sustained either earlier the same day (injured early in the first period and again late in the game) or in the days or weeks prior appears to lower the threshold for a more severe concussion. The initial injury may have gone unreported or undetected. This "second blow" phenomenon is distinct from Second Impact Syndrome, a rare but often fatal neurologic injury. (See "Acute mild traumatic brain injury (concussion) in adults".)

Immediate clinical response after trauma — Most concussions do not present with frank neurologic signs, such as loss of consciousness, posturing, gross disequilibrium, or clear disorientation. However, when these findings are present, the athlete has very likely suffered a concussion and warrants thorough evaluation for concussion or more severe neurologic injury (eg, intracranial bleed, cervical spine injury). (See 'Indications for emergency department evaluation' below.)

Symptoms of concussion — Most concussions are diagnosed based on symptoms. Any new neurologic symptom that develops following sports-related head trauma, whether direct or indirect, strongly suggests the diagnosis of concussion. As examples, a soccer player who heads a ball or an American football receiver or rugby winger that is hit by an opponent with a shoulder to the mid-section and then reports dizziness or feeling "slow" has a concussion. If the same players were to report a new headache only, they should be removed from competition and formally evaluated for a possible concussion. When in doubt, the clinician performing a sideline assessment of an athlete with a new onset headache should treat this as a concussion until further evaluation confirms a different cause. Symptoms associated with concussion are described in greater detail separately. (See "Acute mild traumatic brain injury (concussion) in adults", section on 'Clinical features'.)

Symptom review is best done in a systematic, comprehensive manner using standardized questionnaires and checklists, such as those found in SCAT6. While such concussion symptom scales have not yet been validated for reliability, sensitivity, and specificity [15,16], these instruments are widely used by sideline clinicians. Most instruments use the Likert scale and many group symptoms into clusters. Commonly used sideline instruments are described below. (See 'Assessment instruments' below.)

We find that organizing related symptoms into clusters makes both initial evaluation and surveillance easier to perform. The following are commonly used clusters of concussion symptoms used for evaluation [15-17]:

●Physical – Headache, nausea, vomiting, balance problems, incoordination, dizziness, visual problems, fatigue, photophobia, phonophobia, numbness/tingling, neck pain. An on-field complaint of dizziness by the athlete is among the best predictors of concussion with a protracted recovery [18].

●Cognitive – Feeling mentally foggy or slow, disorientation, difficulty concentrating, difficulty remembering, slow or incoherent speech, word-finding difficulty, slowed reaction time.

●Emotional – Irritability, sadness, emotional lability, nervousness, behavioral changes. As changes in mood may be difficult to gauge, it can be helpful to question family, coaches, teammates, or friends to help determine the athlete’s baseline.

●Sleep-related – Drowsiness, somnolence.

PERFORMANCE OF THE PHYSICAL EXAMINATION — Important elements of the physical examination for assessing patients with possible concussion are described below and include the following:

●Observation

●Memory and attentiveness assessment

●Focused neurologic examination

Performance of the neurologic examination is reviewed in detail separately. (See "The detailed neurologic examination in adults".)

Note that cognitive assessment alone is insufficient for evaluating a patient with a possible concussion. In addition, it is important to note that many concussions are diagnosed based on symptoms alone. The presence of new symptoms after head trauma is sufficient to make a tentative sideline diagnosis of concussion even in the setting of a normal physical examination.

●Observation – Look closely for signs of disequilibrium and lack of coordination. During the evaluation, be aware of concerning abnormalities such as inattentiveness, confusion, atypical emotionality (eg, crying or laughter that is inappropriate or out of character for the athlete), or problems following instructions or focusing on a task.

●Memory and attentiveness – After the initial symptom review, assess memory and attentiveness. Deficits in recall and concentration are common with a concussion. This assessment is best done using a brief standardized neuropsychological test. We recommend SCAT6. SCAT6 incorporates the Maddocks questions (table 1) and Standardized Assessment of Concussion (SAC), which have each been shown to be effective and reliable (table 2) [19,20]. (See 'Assessment instruments' below.)

Simple orientation questions (eg, person, place, time) alone have not been shown to be as helpful in acute sideline assessment [21,22]. Observational studies suggest that amnesia, particularly anterograde amnesia, predicts more severe injury [5].

●Neurologic examination – Look closely for focal deficits (eg, weakness of an extremity, speech difficulty), which may signify more serious intracranial pathology. Be certain to include the following elements:

•Cranial nerve testing. (See "The detailed neurologic examination in adults".)

•Strength and sensation testing of upper and lower extremities. For strength and motor assessment, we test the following: shoulder abduction; elbow flexion and extension; wrist flexion and extension; finger adduction and abduction; hip flexion, extension, adduction, and abduction; knee flexion and extension; and, ankle plantar and dorsi-flexion.

•Vestibular and ocular motor assessment – Assessment of the patient's vestibular and ocular motor function is essential. It can elicit symptoms that may not otherwise manifest. Symptoms (eg, dizziness, nausea) and findings (eg, exophoria during testing of convergence or accommodation) may not be provoked until the ocular motor system fatigues [23-25].

In the authors' experience, an athlete with impaired vestibular or ocular motor function typically performs progressively worse with increased neurocognitive stress, and often becomes symptomatic. In other words, vestibular and ocular motor function in a concussed athlete is often worse at the end of an evaluation than the beginning. This is not true in athletes without a concussion. We take this into account in the order of our assessment, which is as follows:

-Cognitive assessment (memory and attentiveness)

-Cranial nerve and motor-sensory function

-Vestibular and oculomotor assessment (20 seconds each of ocular pursuits [H test]) (movie 1)

-Horizontal and vertical saccades (movie 2)

-Horizontal and vertical gaze stability (movie 3)

-Visual motor sensitivity (movie 4)

-Accommodation and convergence evaluation, three trials of each (movie 5)

-Balance assessment

•Balance assessment – This is a key component of the sideline evaluation for concussion. Balance deficits are common with occipital brain injury (eg, athlete strikes the back of their head on the ground, contrecoup injury involving the occipital lobe) and with rotational injuries, and can often be observed with simple testing. The best studied evaluation is the Balance Error Scoring System (BESS), which is reliable and valid for detecting more pronounced balance problems, but less reliable with subtle deficits (picture 1) [26].

In our experience, balance abnormalities are often not initially appreciated by the athlete, but become readily apparent with a simple assessment (eg, BESS) and are helpful for convincing the athlete that they have a concussion [27]. If initial concussion evaluation is normal and the athlete is asymptomatic, proceed with an exertional trial to determine whether physical exertion provokes any symptoms. The goals are to increase the athlete's heart rate with brief aerobic and resistance exercise and then immediately stress the vestibular system. One simple approach is to have the athlete perform 20 push-ups, run two to three short sprints, perform 15 jumping jacks, and then run a few "figure-eights" (short sprint in a path shaped like the number eight). After this exertional trial, ask the athlete if he or she developed any symptoms (a full symptom checklist is not required for this test).

Of note, acute concussion is often a dynamic and evolving injury, and therefore serial examinations may be warranted to assess for delayed signs or symptoms.

DIAGNOSIS — It may not be possible to make a definitive diagnosis of concussion on the sideline. However, a preliminary diagnosis can generally be made on the basis of the history (including mechanism of injury), symptoms, and examination findings. If a concussion is suspected, the athlete should be removed from further practice or play, or any other activities with a risk of head trauma. (See 'Management' below.)

●History and mechanism of injury – An athlete sustains a concussion via trauma to their head either from a direct blow or through forces transferred to their head from trauma to another part of the body (eg, whiplash). (See 'Mechanism of injury' above.)

Although head trauma often immediately precedes symptom onset, sometimes precipitating trauma occurs many minutes or even hours before an athlete appreciates symptoms or manifests neurologic abnormalities (eg, athlete sustains an unwitnessed blow early during a game but presents with symptoms at half-time).

●Signs – Any athlete who manifests loss of consciousness, confusion, disorientation, disequilibrium, or abnormal speech immediately following head trauma or during the sideline evaluation has at the very least sustained a concussion. In some athletes, the diagnosis of concussion is clear because they experience an obvious transient loss of consciousness witnessed by other players or present during the initial examination. In others, it may be unclear whether a loss of consciousness occurred. However, loss of consciousness is not required for the diagnosis.

●Symptoms – Any new neurologic symptom following direct or indirect head trauma establishes the working sideline diagnosis of concussion. Symptoms of concussion should be assessed using a structured symptom review, such as that included in the SCAT6 assessment checklist. (See 'Symptoms of concussion' above.)

●Examination – The physical examination of an athlete with a possible concussion should include assessments of memory, attentiveness, cognition, and a neurologic evaluation, including assessments of balance, vestibular function, and oculomotor function. Abnormalities in any of these areas elicited via examination confirm the diagnosis of concussion. (See 'Performance of the physical examination' above.)

It is important to understand that concussion, unlike many sports-related injuries, is a diagnosis that must be excluded through a negative review of current symptoms and normal examination. In other words, any athlete being evaluated on the sideline for a suspected concussion must prove to the evaluator that they do not have a concussion. They do so through the absence of symptoms and a normal examination, but must have both.

INDICATIONS FOR EMERGENCY DEPARTMENT EVALUATION — The decision to send an athlete to the emergency department (ED) for more sophisticated testing is based upon the likelihood of significant injury other than concussion (eg, cervical spine injury, intracranial hemorrhage, skull fracture) and the need for neuroimaging and possible intervention. If such injuries are not suspected based upon clinical evaluation, ED referral for concussion management is not cost-effective and may be harmful (cognitive stimuli such as those experienced in the ED may slow recovery and unnecessary neuroimaging with associated radiation exposure may be performed). Indications for transfer by ambulance to the closest ED include:

●Prolonged loss of consciousness (eg, longer than one minute) ‒ Although there is no high quality evidence to support this threshold, one minute is commonly used by clinicians to determine that the duration of loss of consciousness may represent a more dangerous condition. The one minute threshold is cited in the Consensus Statement on Concussion in Sport published by the Fourth International Conference on Concussion in Sport [28].

●Concern for cervical spine injury based upon the mechanism of injury (eg, axial load to the crown of the head), complaints of midline neck pain, midline cervical tenderness on examination, and/or upper or lower extremity motor or sensory deficits. Any athlete with neurologic deficits in bilateral upper or bilateral lower extremities has a cervical spine injury until proven otherwise. (See "Acute traumatic spinal cord injury" and "Cervical spinal column injuries in adults: Evaluation and initial management".)

●High-impact or high-risk mechanism for intracranial bleed (eg, player's head forcefully striking a soccer goal post, cheerleader falling to ground from a significant height) [29], including high velocity impact from a solid object (eg, baseball striking temporal region, bat striking head). Collisions involving cyclists, equestrians, or those involved in motor sports (eg, motocross, snowmobiling) generally involve impact at relatively high speed and should be considered high-risk. (See "Subdural hematoma in adults: Etiology, clinical features, and diagnosis", section on 'Clinical manifestations' and "Intracranial epidural hematoma in adults", section on 'Clinical manifestations' and "Management of acute moderate and severe traumatic brain injury".)

●Examination findings suggestive of skull fracture ‒ Examples of such findings include palpable skull deformity, hemotympanum, and drainage of cerebral spinal fluid from the nose. (See "Skull fractures in adults".)

●Post-traumatic seizure ‒ A seizure is not a sign of concussion and suggests the presence of intracranial pathology (eg, hemorrhage). The presence of seizure activity makes concussion a diagnosis of exclusion until intracranial pathology is ruled out. Therefore, any athlete who develops seizure activity following head trauma should be taken immediately by ambulance to the emergency department for evaluation. (See "Posttraumatic seizures and epilepsy".)

●Any significant acute worsening in the patient's condition – Such findings suggest intracranial hemorrhage and typically become evident within the first several minutes to a few hours after head trauma (may take longer in athletes over 60 years). Signs that warrant concern include:

•Persistent nausea and vomiting

•Focal neurologic deficits

•Deteriorating neurologic status including progressive somnolence, slurred speech, difficulty or inability to walk, worsening mental status

DIFFERENTIAL DIAGNOSIS: CONCUSSION MIMICS — In addition to the emergency conditions discussed above that may be sustained from head trauma (eg, intracranial hemorrhage, skull fracture), clinicians should consider concussion mimics as part of the differential diagnosis when evaluating an athlete on the sideline. Such mimics include the following:

●Migraine – Concussion can be difficult to differentiate from migraine, for which exertion can be a trigger. Key points of distinction include: the athlete is a known migraineur, the headache presentation is typical of previous migraines, and no trauma occurred prior to the onset of the headache. (See "Pathophysiology, clinical manifestations, and diagnosis of migraine in adults".)

●Non-concussion headache – Headaches are common in athletes and many are not due to concussion. A headache from an acute concussion is triggered by trauma. The absence of trauma is crucial in distinguishing concussion headache from non-concussion headache.

Another distinguishing factor is that the non-concussion headache precedes participation (eg, an athlete without a recent concussion develops a nontraumatic headache before the game and this headache continues during the game). In addition, the characteristics of the headache may be helpful. Typically, a concussion-related headache is relatively diffuse, while headaches from an abrasion or contusion to the scalp are localized and superficial, and associated with focal tenderness. Helmeted athletes, particularly American football players, commonly note frontal or occipital headaches during the early part of the season as they adjust to their helmets. These headaches are not induced by trauma and resolve once the helmet is removed.

Although the distinguishing characteristics described here may be helpful, differentiating a concussion-related headache from a non-concussion headache can be difficult and may require a thorough evaluation. If the clinician is unsure, it is best to assume that a concussion has occurred and to keep the athlete out of harm's way: "when in doubt, sit them out."

●Anxiety – Acute anxiety can trigger a variety of physical and mental manifestations (eg, nausea, vomiting, confusion, irrational behavior). Clinicians can generally distinguish between symptoms attributable to anxiety and those caused by a concussion on the basis of the history. A concussion is preceded by direct or indirect head trauma. Conversely, symptoms can only be attributed to anxiety in the absence of head trauma and when the athlete provides history (current or past) that suggests anxiety as a possible cause. (See "Panic disorder in adults: Epidemiology, clinical manifestations, and diagnosis" and "Generalized anxiety disorder in adults: Epidemiology, pathogenesis, clinical manifestations, course, assessment, and diagnosis", section on 'Clinical features and course'.)

●Heat illness – Sideline clinicians must be vigilant for signs of exertional heat illness, particularly life-threatening exertional heat stroke. The presence of high ambient temperature and humidity, risk factors for heat illness (eg, obesity, deconditioning, stimulant use), progressing symptoms, and elevated core body temperature (rectal temperature), and the absence of preceding trauma, usually enable the clinician to distinguish heat illness from concussion. (See "Exertional heat illness in adolescents and adults: Epidemiology, thermoregulation, risk factors, and diagnosis".)

●Exertional sickle cell crisis – The presentation of this condition can be similar to exertional heat illness (confusion, lethargy, mental status changes) [30]. Knowledge of the patient's history, the absence of trauma, and the presence of risk factors for sickling (eg, deconditioning, activity at high altitude, concomitant febrile illness, dehydration) increase the likelihood of exertional sickle crisis in an athlete with sickle cell trait. Of note, the overwhelming majority of sickle cell trait-associated deaths in collegiate athletics occur during non-contact, off-season training. (See "Sickle cell trait", section on 'Rhabdomyolysis and sudden death during strenuous physical activity'.)

MANAGEMENT

Initial patient evaluation — During the initial evaluation of an athlete with a possible concussion, the clinician must answer a few key questions:

●Is this a concussion or a more severe head injury?

●Has the athlete sustained significant injuries other than head trauma (eg, cervical spine injury)?

●Is emergency department evaluation needed?

●What initial management steps are needed?

Athletes who have sustained significant trauma and are at risk of significant internal injury or manifest examination findings suggestive of such injury are managed according to standard trauma protocols and transferred to the emergency department. (See 'Indications for emergency department evaluation' above and "Initial management of trauma in adults" and "Trauma management: Approach to the unstable child".)

Concussion assessment — For athletes with a potential concussion but no other significant injury, the sideline clinician attempts to determine the preliminary diagnosis and severity of injury by learning about the mechanism and the athlete's medical history, evaluating clinical signs and symptoms, and performing a neurologic examination, with particular focus on balance, vestibular, and ocular motor function, memory and cognition, and other functional tests [1,3,4,31,32].

Remember to ask about comorbidities. It is important to ascertain any history of previous concussion including any protracted or complicated recovery. Knowledge of any recent concussion (within the previous several weeks) is particularly important because the presence of unresolved symptoms increases susceptibility for recurrent, and often worse, injury. The sideline evaluation should be systematic and comprehensive, and typically requires 10 minutes or longer [1,6,33].

To the degree that conditions allow, evaluation should be performed in a quiet environment free off distractions. As examples, at hockey or basketball games, we bring athletes to the locker or training room for evaluation; at American football, rugby, or soccer matches, we bring athletes behind the stands, into the entry tunnel, or to the locker or training room.

We perform our assessment as follows:

●History ‒ If the trauma was not directly observed, obtain a description of the trauma from the patient and other observers (eg, athletic trainer, coach, teammates). Review video of the injury if available. Ask about the athlete's actions immediately following the episode: Was the athlete confused or disorientated? Were their movements unsteady or uncoordinated? Did the athlete appear dazed? Was their speech slow or incoherent? Did they have difficulty following directions or completing assignments on the field? Were they holding their head, or complaining of anything while on the field? (See 'Mechanism of injury' above and 'Risk factors' above.)

●Symptom assessment ‒ Assess the athlete's symptoms by interviewing the patient using a standardized assessment tool, such as the SCAT6, which includes a symptom questionnaire (SCAT6). (See 'Assessment instruments' below and 'Symptoms of concussion' above.)

●Physical examination ‒ Perform a careful examination using a standardized approach, such as that provided in SCAT6 or Concussion Assessment & Response: Sport Version (CARE). Focus on the following areas (important note: vestibular and ocular motor evaluation is not included in the SCAT6 or CARE guides, but the authors believe these are essential for proper assessment) (see 'Performance of the physical examination' above):

•Memory and attentiveness

•Cranial nerve function

•Motor-strength and sensation

•Vestibular and ocular motor performance

•Balance

Even if the initial evaluation is unremarkable, it is important to maintain a high index of suspicion given that the symptoms and signs of concussion can be delayed from minutes to several hours. Accordingly, we recommend asking the athlete about any onset of symptoms periodically over the course of the contest (typically every 30 minutes or so) and then after the game. If suspicion for a concussion persists but the results of the initial evaluation are unclear, we suggest resting the athlete and repeating the evaluation between 30 to 60 minutes after the initial assessment. If the clinician remains suspicious about a potential concussion, it is best to remove the athlete from competition regardless of any test results ("when in doubt, sit them out").

Assessment instruments — The potentially concussed athlete is best evaluated using instruments designed explicitly for the assessment of a sports-related concussion, thereby ensuring a systematic assessment amenable to field or court-side conditions. Such instruments should include an appropriate review of current symptoms and a focused physical examination, including tests of neurologic function. In addition, it is essential to include post-exertion testing in order to unmask symptoms that may not be present at rest. Post-exertion testing is described above. (See 'Performance of the physical examination' above.)

Several instruments for sideline evaluation are available. There is no compelling evidence supporting one specific test, tool, biomarker, imaging study, or protocol to definitively diagnose or exclude concussion. In the absence of such evidence, use of a consensus-derived multimodal concussion assessment tool is recommended [4]. We are most familiar with SCAT and find it to be effective, but other tools, such as the Concussion Assessment & Response: Sport Version (CARE), are sound guides as well. Useful assessment instruments are thorough but concise, and typically require 8 to 20 minutes to complete (but may take longer). Studies of available standardized assessment instruments are discussed separately. (See "Acute mild traumatic brain injury (concussion) in adults", section on 'Standardized examinations'.)

The following are among the more popular instruments:

●Sport Concussion Assessment Tool Edition 6 (SCAT6) (for ages 13 and older) and Child SCAT6 (for ages 5 to 12 years) were endorsed in the 2022 Consensus Statement on Concussion in Sport and are used widely for sideline evaluation [3,4,34,35]. SCAT6 and Child SCAT6 provide a well-organized, evidence-based, and detailed guide to early clinical assessment and include: review of indications for emergency referral, Glasgow Coma Scale, symptom assessment, and physical and cognitive assessment. They provide a scoring summary in table format (although normative data and cut-off scores for concussion diagnosis have not been defined).  

●Concussion Assessment & Response: Sport Version (CARE) ‒ This is a smart-phone application that helps health care professionals evaluate a potential concussion in a systematic fashion. It includes: initial injury assessment (primary emergency survey including red flags, review of concussion signs and symptoms), evaluation of cranial nerve function, CPR cues, Balance Error Scoring System (BESS) (picture 1), Standardized Assessment of Concussion (SAC), Graded Symptom Checklist (GSC), Return-to-Play Guide, General Information (frequently asked questions), and ACE Post-Concussion Home/School Instructions.

●Standardized Assessment of Concussion (SAC) – The SAC is one of the earliest and most thoroughly studied tools for acute evaluation of athletes with possible concussion. The SAC includes tests for orientation, immediate and delayed recall, and concentration, as well as exertional maneuvers (table 2 and table 3). Although not part of the scored assessment, the SAC also includes a graded symptom checklist, a brief neurologic examination, and records the presence of post-traumatic and retrograde amnesia.

The SAC appears to provide more accurate information when results are compared with an established baseline obtained prior to injury [36]. In a study involving 41 concussed collegiate athletes and 41 uninjured, matched teammate controls, SAC showed poor retest reliability [37].

●Applications for smart phones and tablets – Smart phone technology has made it easier to access tools for the acute sideline assessment of concussion. However, not all of these applications meet suitable standards, and many are proprietary [38]. We suggest the SCAT6, which is available for free and has been approved and adopted by a wide range of amateur and professional sports organizations.

Additional tools for assessment — Assessment tools have been and continue to be developed to assist with the sideline evaluation of athletes with a possible concussion, but further study is needed before strong recommendations can be made. Some institutions are developing applications for smart phones and hand-held devices for on-field concussion assessment [39]. Head impact sensors (helmet sensors, or sensors in mouth guards, headbands, or directly applied to skin) have not been shown to provide helpful information to sideline clinicians [1,4].

The King-Devick test is a proprietary tool that assesses saccadic eye movements. The results of studies to assess the test's performance as a sideline assessment tool have been mixed [4,37,40-44]. In a study comparing 41 acutely concussed collegiate athletes with 41 uninjured matched teammate controls, King-Devick performed more accurately than other standardized tests (eg, SAC, modified BESS) but not as well as a symptom severity score [37].

Initial treatment

Remove from play; no return to play — Once a concussion is suspected or diagnosed, the most important next step is to remove the athlete from harm's way. No athlete should be permitted to return to a game or practice, or any activity with a risk of head trauma, on the day a concussion is diagnosed or suspected. Avoiding repeat head trauma is critical to a quick recovery, while continued play increases the risk for complications [45,46].

Relative rest — Relative neurocognitive rest ("prescribed rest") remains an important element of initial concussion treatment. While there are no well-established definitions of "rest," our approach includes reasonable restrictions on physical and cognitive activity, particularly during the first 24 to 48 hours, based on the severity of injury. Rest appears to be most effective when employed immediately upon diagnosis, rather than days or weeks later [1,47]. We recommend no driving until a complete, office-based clinical assessment can be performed.

Light physical activity is permitted and encouraged provided it does not provoke an increase in symptoms [48]. In general, we limit exercise to simple activities that cause little if any vestibular stress, such as walking or easy riding on a stationary bicycle, and instruct athletes to stay below intensity levels that exacerbate symptoms.

For those with milder symptoms and reassuring examination and test results, we suggest relative cognitive rest. Further, we encourage eliminating or at least limiting screen time during the first 48 hours after injury [48-50]. In our experience, exposure to video games, loud music, prolonged screen time, or mental activities requiring high levels of focus and concentration frequently induces symptoms and needs to be curtailed for a few days after injury.

For patients with severe symptoms or concerning provocative testing results, additional limitations for a short period of time (eg, no phone, no test taking, no texting, no TV, no computer) may be helpful. However, it is now generally accepted that total stimulus deprivation ("cocoon therapy") and protracted rest is ineffective and may be detrimental to recovery. The evidence pertaining to cognitive rest following concussion is reviewed separately. (See "Concussion in children and adolescents: Management", section on 'Cognitive rest'.)

Patients evaluated on the sideline and diagnosed with a concussion should be re-evaluated soon (ideally within 24 to 48 hours after injury) by a physician who can provide education about the injury and determine appropriate next steps, including additional testing or consultation as indicated and treatment recommendations. Treatment may include guidance regarding appropriate levels of physical, cognitive, and social activity, as well as active interventions (eg, vestibular or ocular motor rehabilitation). (See "Clinic-based management of sports-related concussion in adolescents and adults", section on 'Treatment' and "Concussion in children and adolescents: Management", section on 'Initial approach'.)

Management of somatic symptoms — Although treatment with analgesics following concussion has not been formally studied, based on broad clinical experience it appears safe to treat somatic symptoms, particularly headache, with over-the-counter analgesics. Acetaminophen or over-the-counter nonsteroidal anti-inflammatory medications (NSAIDs) are safe and reasonably effective for headache related to concussion. It is important to note that athletes diagnosed with or suspected to have sustained a concussion may not return to play even if their symptoms resolve with over-the-counter analgesics. (See 'Remove from play; no return to play' above and "Clinic-based management of sports-related concussion in adolescents and adults".)

We recommend strict avoidance of any medications or substances that may adversely affect cognition, such as opioids, tramadol, "muscle relaxants" (eg, cyclobenzaprine), benzodiazepines, alcohol, and illicit drugs. In our experience, we have not found there to be much need for other acute symptomatic medications, including anti-emetics.

We have found that nausea following a concussion generally subsides quickly and does not require aggressive medical therapy. If necessary, athletes may take small sips of over-the-counter anti-nausea products (eg, fructose, dextrose, and orthophosphoric acid combination; bismuth) to reduce their symptoms. In the rare circumstance when severe nausea persists and there is no likelihood of intracranial hemorrhage (concern for which requires immediate evaluation in the emergency department), clinicians may give a low dose of a relatively safe antiemetic that is unlikely to cause side effects affecting the central nervous system, particularly altered mental status (eg, ondansetron).

Observation after injury and during sleep — It is important to ensure that a responsible adult is with the concussed athlete for the first six to eight hours after concussion primarily to monitor for any acute worsening during this time. Acute deterioration in mental status suggests possible intracranial hemorrhage and the need for emergent assessment. (See 'Indications for emergency department evaluation' above.)

However, it is not necessary, nor is it our practice, to advise waking an athlete every two to three hours throughout the night for reassessment. Not only does this interfere with the cognitive rest needed for recovery, but it is difficult to assess accurately the cognitive status of a concussed athlete who is awakened every two to three hours. Instead, we suggest allowing the athlete to sleep, but recommend having a responsible adult look in on them every few hours to ensure that they do not show any sign of distress (eg, labored breathing, thrashing about).

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Sports-related concussion" and "Society guideline links: Increased intracranial pressure and moderate-to-severe traumatic brain injury" and "Society guideline links: Minor head trauma and concussion".)

SUMMARY AND RECOMMENDATIONS

●Definitions, risk factors, and mechanisms – A concussion is a complex pathophysiological process affecting the brain and caused by trauma. It may involve a direct blow to the head or a blow to the body that transmits force to the head (eg, whiplash). Concussion can manifest in a wide variety of symptoms and signs that may or may not include loss of consciousness. No gross structural abnormalities are seen with neuroimaging. (See 'Definition' above.)

Risk factors include previous concussion, younger age (prepubescent athletes are at greater risk), sports involving collision (eg, American football, rugby), and possibly female gender. Concussion may be more likely following high-energy impact, double hits, and blows involving rotational forces, and in athletes who have recently sustained head trauma. (See 'Risk factors' above and 'Mechanism of injury' above.)

●Symptoms of concussion – Symptoms may include physical (eg, headache, nausea, balance problems, dizziness, and visual changes), cognitive (eg, mental slowness, difficulty concentrating or remembering, speech difficulties), emotional (eg, irritability, sadness, emotional lability), or sleep-related findings (eg, drowsiness). (See 'Symptoms of concussion' above.)

●Examination – Assessment of the potentially concussed athlete must include a careful physical examination; cognitive assessment alone is not sufficient. The examination should include observation for signs of concussion (eg, decreased coordination), assessment of memory and attentiveness, and a systematic neurologic examination (including assessment of cranial nerves, strength and sensation of the upper and lower extremities, ocular motor and vestibular function, and balance). It is important to include exertional testing, which may elicit symptoms. (See 'Performance of the physical examination' above.)

We suggest that a standardized multimodal assessment instrument be used to help ensure a proper evaluation. Suitable instruments include SCAT6 and the CARE smart-phone application. (See 'Concussion assessment' above and 'Assessment instruments' above.)

●Diagnosis – It may not be possible to make a definitive diagnosis of concussion on the sideline. However, a preliminary diagnosis can generally be made on the basis of the history (including mechanism of injury), symptoms, and examination findings. Any new neurologic symptom or sign that develops following sports-related head trauma makes the diagnosis of concussion. (See 'Diagnosis' above.)

●Indications for transfer to emergency department (ED) – Athletes who have sustained a concussion but are not suspected of having any other significant injury should not be transferred to the ED. Indications for transfer by ambulance to the ED include:

•Prolonged loss of consciousness (eg, over one minute)

•Concern for a cervical spine injury

•High risk for intracranial bleed

•Examination findings suggestive of skull fracture

•Post-traumatic seizure

•Significant acute worsening of the patient's condition (see 'Indications for emergency department evaluation' above)

●Initial management – Any athlete diagnosed with a concussion should not return to play that day. When the diagnosis is unclear but remains a possibility, the best approach is to remove the athlete from practice or play ("when in doubt, sit them out").

Once a concussion is diagnosed, initial treatment consists primarily of relative cognitive and physical rest. A responsible adult should remain with the concussed athlete for the first six to eight hours to monitor for any acute worsening. However, it is not necessary to wake the athlete every two to three hours throughout the night for reassessment.

Over-the-counter analgesics (eg, acetaminophen) are safe and reasonably effective for headache related to concussion. We recommend strictly avoiding any medications or substances that may adversely affect cognition, such as opioids, tramadol, "muscle relaxants" (eg, cyclobenzaprine), benzodiazepines, alcohol, and illicit drugs. The patient should be reevaluated within the next day or two by a physician. (See 'Initial treatment' above and "Clinic-based evaluation of sports-related concussion in adolescents and adults".)