Neurometabolic cascade after traumatic injury. Cellular events: 1. Nonspecific depolarization and initiation of action potentials. 2. Release of excitatory neurotransmitters. 3. Massive efflux of potassium. 4. Increased activity of membrane ionic pumps to restore homeostasis. 5. Hyperglycolysis to generate more adenosine triphosphate (ATP). 6. Lactate accumulation. 7. Calcium influx and sequestration in mitochondria, leading to impaired oxidative metabolism. 8. Decreased energy (ATP) production. 9. Calpain activation and initiation of apoptosis. Axonal events: A. Axolemmal disruption and calcium influx; B. Neurofilament compaction via phosphorylation or sidearm cleavage. C. Microtubule disassembly and accumulation of axonally transported organelles; D. Axonal swelling and eventual axotomy. ADP adenosine diphosphate, AMPA alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid, Glut glutamate, NMDA N-methyl-d-aspartate. (From Giza CC, Hovda DA. The neurometabolic cascade of concussion. J Athl Train 2001;36:230)
Functional versus structural injury: In SRC, neurological impairment is short-lived and resolves spontaneously. Clinical signs and symptoms largely reflect the result of direct impact resulting in acute acceleration or deceleration of the body with the brain moving within the cranium, which leads to injury. Cumulative exposures can have clinical consequence, and some studies report cognitive deterioration is directly related to exposure burden, whereas other studies have failed to reproduce this result .
9.3 Concussion Evaluation
SRC is an evolving injury in the acute phase and there are quickly changing clinical signs and symptoms. SRC is considered one of the most complex injuries in sports medicine to diagnose, assess, and manage. Complicating this, often there is no loss of consciousness or delineating neurologic signs. There is also no perfect diagnostic test. So, SRC cannot be ruled out when injury occurs. If SRC is suspected, the individual should be removed from the playing field and assessed by a physician.
Sideline evaluation of cognitive function is essential in the assessment of injury. Neuropsychological (NP) test batteries assessing attention and memory function are effective. Included in this is the SCAT5, which contains Maddocks questions (Maddocks) and standardized assessment of concussion (SAC) . Orientation questions like person, place, and time are unreliable compared to memory assessment. These sideline screening tests are not meant to replace neurological evaluation or as an ongoing management tool for SRC.
The purpose of the rapid screening for SRC is not to make a definitive diagnosis of head injury. If clear on-field signs of SRC (e.g., loss of consciousness, tonic posturing, balance disturbance) are apparent, the individual should be immediately suspended from play. Sideline (SCAT5) and a more thorough diagnostic evaluation should be performed in a distraction-free environment. Sideline assessment, including information from the athlete and assessment or inspection of videotape of the incident, can be used to determine if concussion is no longer suspected. The physician determines the timing of return to play.
Contact sports have a tendency to be fast-paced, in disorganized environments, and field of play is often obscured. Therefore, these present challenges in diagnosing SRC. Because of this, suspected SRC should be approached with multidimensional testing and well-established instruments for sideline assessment. Both the SCAT5 and Child SCAT5 are suggested in the evaluation of SRC. These sideline assessments help in distinguishing if an athlete is concussed or non-concussed, but the tests’ usefulness decreases significantly after 3–5 days of the injury. The symptom checklist has more utility in tracking recovery. Replicating baseline testing conditions should be similar. Additional areas that may be assessed are clinical reaction time, gait/balance assessment, video observation, and oculomotor screening. Video review appears to be a promising mode of identifying and evaluating SRC.
9.3.1 Signs and Symptoms: Physical, Cognitive, Emotional, Sleep 
- Clinical symptoms
somatic (e.g., headache), cognitive (e.g., feeling like in a fog), and/or emotional symptoms (e.g., lability)
- Physical signs
e.g., loss of consciousness, amnesia, neurological deficit
- Balance impairment
e.g., gait unsteadiness
- Behavioral impairment
- Cognitive impairment
e.g., slowed reaction times
- Sleep/wake disturbance
e.g., somnolence, drowsiness
These signs and symptoms may be present with non-brain-related injury. Therefore, concussion is added to the differential diagnosis for further investigation, but concussion cannot be diagnosed based on the symptoms present. The majority of athletes (80–90%) have symptom resolution after a week, but younger children under age 12 may take a month before fewer symptoms are present. Symptom resolution does not guarantee complete cognitive recovery .
220.127.116.11 Concussion Evaluation Tools
When an athlete aged 13 and older is suspected of having sustained an SRC, the SCAT5 is a tool used by sideline physicians to assess for the presence of concussion and initiate management based on clinical findings. If the athlete falls into the ages of 5–12 years old, the Child SCAT5 will be utilized. The athlete with a possible concussion should be immediately removed from play and evaluated by medical personnel for any red flag signs.
Red flags SCAT5
– Neck pain or tenderness
– Seizure or convulsions
– Double vision
– Loss of consciousness
– Weakness or tingling/burning in arms or legs
– Deteriorating conscious state
– Severe or increasing headache
– Increasingly restless, agitated, or combative
Observable signs including lack of movement, disorientation, vacant stare, and orofacial injury after head trauma should be assessed. The Glasgow Coma Scale (GCS) can be performed serially to assess for changes in eye, verbal, and motor response. Maddocks questions for memory assessment and cervical spine examination are critical in the initial assessment. A cervical injury should be assumed until proven otherwise [7, 8]. Decision to transport an athlete should be made in a timely fashion. The athlete background and symptom evaluation should be performed in a distraction-free environment. The cognitive screening includes the following: orientation, immediate memory from lists of words, and concentration assessed by digits backwards and months in reverse order. Neurological screening includes the ability to read without difficulties, full pain-free active neck movements, movement of the head or neck without double vision, coordination, and tandem gait testing. Delayed recall should include words from the list read earlier. When differentiating concussed from non-concussed athletes, the graded symptom checklist, Standardized Assessment of Concussion (SAC), and Balance Error Scoring System (BESS)/modified Balance Error Scoring System (mBESS) were found to be the most useful post-injury . When assessing for concussion, a single scoring system should not determine the diagnosis. Although tools such as the SCAT5 are utilized, more research is required to determine the efficacy of these tools in improving SRC identification and management.
Components of SCAT5
Glasgow Coma Scale
Cervical spine evaluation
Athlete background and symptom evaluation
9.3.2 Neuropsychology Evaluation
Most concussion symptoms will resolve within 7–10 days. Neuropsychological (NP) testing can be useful for those athletes with prolonged symptoms and recovery. This testing can be used as part of a comprehensive investigation and should not be used alone to guide management. “Both paper and pencil and computerized testing have significant individual variability with regard to domains measured and performance measures such as validity, sensitivity, specificity, reliable change index and baseline variability” . Computerized NP baseline testing can be useful in comparing post-injury results, but this can result in expenses that may not be affordable for many school systems. NP testing performed when the athlete is asymptomatic may be useful when considering return-to-school and return-to-play decisions. Although neuropsychologists have the background to administer and interpret test results, the ultimate return-to-play decision should remain with the medical team .
18.104.22.168 Pencil and Paper
Neuropsychological testing is a tool used to assess cognitive impairment after an athlete sustains a concussion and to document an athlete’s recovery. Testing is administered and interpreted by a neuropsychologist; therefore, this method is expensive and more time-consuming. The testing typically focuses on memory, cognitive processing speed, and reaction time .
22.214.171.124 Computer-Based Testing
Computerized neuropsychological testing has not been validated as a diagnostic tool . Advantages of computerized testing include less time to administer, more cost-effectiveness, and more precision reporting on reaction time.
9.3.3 Vestibular/Ocular-Motor System (VOMS) Evaluation
Vestibular/ocular-motor screening can assist with proper assessment and subsequent referral placement. Prolonged symptoms along with vestibular and oculomotor impairment may be associated with delayed recovery after SRC. Examples of vestibular symptoms may include the following: blurry vision, dizziness, nausea, and vertigo. Oculomotor symptoms may include blurry vision, nausea, difficulty scanning, convergence insufficiency, and difficulty reading [25, 26]. These symptoms can impact academic performance, reading, and ultimately overall performance.
126.96.36.199 King-Devick Test
9.3.4 Balance Assessment
Following SRC, acute postural instability may persist for up to 72 h . Studies report that changes in balance and postural stability, when compared with preseason baselines, are sensitive for the diagnosis of concussion. The Balance Error Scoring System (BESS) is a standardized sideline assessment tool. This test can be administered in 5–7 min and is cost-effective. Three stances (double-leg stance, single-leg stance, and tandem stance) are performed on two surfaces (firm surface/floor or medium density foam). The athlete stands during each stance with hands on hips and eyes closed for 20 s. Points are deducted from a maximum of 60 when using two surfaces, if the athlete lifts her hands off the hips, stumbles, steps away, opens her eyes, or falls. BESS performance returns to preseason baseline levels by 3–7 days post-injury for most athletes. Balance testing is limited by fatigue, exercise, serial assessments, and reliability. According to McCrea, sensitivity of balance testing is best within 24 h of injury (0.34), and specificity was 0.91 and 0.96 between days 1 and 7 post-injury. Completing the BESS on the sideline can be challenging, so the modified BESS is often used at halftime or in the locker room after practice or game. The high specificity combined with other assessment tools reinforces the use in the sideline evaluation.
9.3.5 No RTS Same Day
There is a no return to sport on same-day policy for those diagnosed with concussion. In 2009, legislation began in Washington state with the Lystedt law. The legislation mandates any athlete younger than 18 must be removed from play and is unable to return on the day of injury. Many states have concussion laws that oppose a same-day return. Signs and symptoms may evolve over time; therefore, reassessment of the athlete’s condition and erring on the side of caution are reasonable actions.
9.4 Concussion Management
If the athlete demonstrates signs and symptoms of cervical spine injury, intracranial bleeding, or skull fracture, the emergency action plan should be activated, and the athlete will be transported to an appropriate medical facility . The sideline examination should include documentation of the injured athlete’s symptoms and neurologic examination including cognition, cranial nerve function, and balance. Visual tracking can provide further information. Symptom scores and cognitive assessment are the most sensitive and specific within 48 h of injury. Comparing post-injury scores to the athlete’s baseline is also useful. This does not replace the benefits of knowing the athlete prior to injury and using clinical judgment despite the athlete passing a sideline screening. All athletes, regardless of level of competition, should be managed using the same principles.