Epidemiology

The most recent population data estimates 2.5 million traumatic brain injury–related emergency department (ED) visits, hospitalizations, and deaths each year in the United States. According to the Nationwide ED Sample, the rate of mTBI in ED visits was 807 per 100,000 visits in 2012, with the highest rates of mTBI requiring medical attention occurring in 0- to 4-year-olds, followed by male 15- to 24-year-olds, and females 65 years and older. The lowest rates were found for 45- to 64-year-olds. Across all age groups, males were found to have a higher rate of mTBI ED visits compared with females, except among those patients aged 65 years and older. Among all patients diagnosed with mTBI, falls were found to be the most common external cause of injury.

In the United States, estimates of 1.6 to 3.8 million athletes sustain an SRC each year, a statistic that includes those for which no medical attention is sought. With nearly 8 million participants annually, high school athletes make up the single largest athletic cohort in the country who may be susceptible to head injuries. The National High School Sports-Related Injury Surveillance Study showed that concussion moved from the fourth most commonly reported category of injury in 2005–06 (9% of all sports-related injuries) to the most commonly reported injury category in 2016–17, accounting for 24.8% of all sports-related injuries. The National Athletic Treatment, Injury and Outcomes Network (NATION) study that used a convenience sample of 147 high schools drawn from 26 states to compile data on 31 sports found a total of 2004 SRCs across 3 academic years (2011–2014), leading to an overall SRC rate of 3.89 per 10,000 athletic exposures (defined as one student participating in one athletic practice or competition). High school football had the highest overall SRC rate, followed by boys’ lacrosse and girls’ soccer ( Table 23.2 ). For all sports, the rate of SRC was higher during competition compared with practice. Nearly 3% of all SRCs were reported to be recurrent concussions ; however, recurrent concussions, specifically in the high school athlete population, have been reported to account for 11% of all SRCs.

During the 2009–10 to 2013–14 academic years, it was estimated that SRCs constituted 6.2% of all injuries that occurred during participation in collegiate athletics. Wasserman and colleagues reported a total of 1670 SRCs in schools participating in the National Collegiate Athletic Association (NCAA) Injury Surveillance Program (ISP), leading to a yearly national estimate of 10,560 SRCs in collegiate sports. Although football contributed the greatest number of SRCs (36.1%), followed by men’s ice hockey (13.4%) and women’s soccer (8.1%), of the 25 collegiate sports investigated in the NCAA ISP, men’s wrestling and men’s and women’s ice hockey were found to have the highest overall concussion rates (see Table 23.2 ). ^, Similar to high school athletes, a higher rate of concussions occurred during competition compared with practice, with an injury rate of 14.59 and 2.57 per 10,000 athletic exposures, respectively. Nearly 1 in every 11 SRCs that occurred were reported to be recurrent concussions. Overall, most concussions were related to player contact; however, other mechanisms, such as contact with the playing surface and equipment such as sticks and balls, have been described.

It is well documented that females are at greater risk of experiencing an SRC compared with males participating in high school and collegiate sports. ^, In high school athletics, the rate of SRCs has been found to be 56% higher in girls than in boys, and the disparity in SRC incidence between girls and boys has been reported to be twice as high when considering contact sports alone. Some researchers have suggested that structural and physiological differences in cervical spine morphology, strength, and dynamic stability ^{, ,} account for sex differences in the incidence of SRCs; however, given the evidence that female athletes are more likely than male athletes to report a concussion, ^, it is unlikely that potential structural and physiological differences solely explain the biological sex gap in SRC incidence.

Pathophysiology

The basic neurobiology of concussion has been described as a neurometabolic cascade of events that does not always result in cell death, but will lead to a functional injury where cells undergo a significant energy crisis. This process, referred to as the bioenergetic crisis , is characterized by a mismatch between energy supply and demand.

Neurons have a relatively high consumption of oxygen and depend almost exclusively on oxidative phosphorylation for energy production. Mechanical deformation of neurons, termed mechanoporation , caused by an acceleration/deceleration force quickly leads to two mechanisms of dysfunction: failure of energy-dependent ion transport pumps and release of large quantities of glutamate. Failure of the energy-dependent ion pumps allows charged ions to move across their electrical and concentration gradients, leading to an efflux of potassium and an influx of calcium and sodium. Excessive concentrations of calcium and sodium within the cell causes degradation of cytoskeletal proteins and cytotoxic edema as water follows positively charged ions into the cell. The ionic flux leads to an energy crisis as a considerable amount of the cell’s energy reserve is spent attempting to restore ionic homeostasis by pumping calcium and water out of the cell. A direct consequence of the excessive calcium influx is release of excessive glutamate, a potent excitatory molecule, into the extracellular space. Glutamate then binds to N -methyl- d -aspartate (NMDA) receptors on neighboring neurons leading to calcium influx and release of more glutamate into the extracellular space. This process, referred to as excitotoxicity , leads to a self-perpetuating, deleterious cycle of hyperexcitability and cellular instability.

Another contribution to the energy crisis is an initial decrease in cerebral blood flow, which creates a mismatch between energy supply and demand (increased glucose metabolism to support increased neural activity) in the initial stages of concussion. Functionally, the cell is then vulnerable to subsequent injury, meaning the cell has less energy reserve or resources to address a subsequent stress, be it a second biomechanical stress (e.g., second impact syndrome) or a functional stress such as an increased cognitive or physical load. This point is important for medical professionals who consider return to play protocols in acute concussion as the impaired metabolic state can extend for weeks to months.

Cytoskeletal and axonal alteration due to axonal stretch can interfere with axonal transport, leading to impaired synaptic transmission and in severe cases result in retraction and degeneration of the synapse. This process, referred to as axonal disconnection , can be a transient event and in some cases may recover, but due to the poor regenerative capacity of the central nervous system, such stretching may lead to permanent axonal damage. ^,

Recent studies suggest that inflammatory changes are also triggered by mTBI and cause functional disruption of neural activity. Cytokines, cystokines, and immune-mediated responses may play in important role in neuroinflammation after injury. Immunoassay of plasma cytokines, chemokines, epinephrine, and norepinephrine in individuals following brain trauma has revealed a relationship between systemic inflammation and autonomic nervous system dysregulation with an acute hyperadrenergic state. A preliminary study of rugby players who have sustained concussion injuries indicates that genetic influences may trigger a postinflammatory brain syndrome (PIBS) that is congruent with prolonged symptoms after injury.

It appears there is little to no cell death associated with mTBI; however, the impact of subsequent head injury or potential detrimental structural and physiological degeneration that occurs over time is unclear. In longitudinal studies of mTBI using rodent models, there is evidence of cortical and subcortical atrophy and depletion of dopaminergic neurons in subcortical nuclei ; however, the degree to which the changes occur in humans or how they relate to impaired cognitive, physical, and emotional function following a concussion in humans has not been determined at this time.

Persistent symptoms/prolonged recovery

Injuries that seem mild initially can occasionally cause a constellation of somatic, cognitive, emotional, and behavioral symptoms. In most cases, the majority of individuals will have a complete functional recovery and return to their life activities without the burden of these sequelae. ^, But a “miserable minority,” approximately 10% to 33% of patients, will experience an incomplete recovery, and their symptoms often persist for months or even years after the initial injury. ^, Using these numbers, an estimated 200,000 to 600,000 individuals every year in the United States are likely to experience persistent symptoms after a head injury. With few longitudinal studies, there is limited information related to time periods that persistent symptoms may last; however, for concussions in general, the prevalence of persistent symptoms at 1 year following the injury is estimated to be 5%.

As one may expect, differences have been found across age groups for patients who continue to endorse persistent symptoms following a concussion. For SRCs, higher rates of persistent symptoms have been reported following concussion in cohorts of high school athletes compared with collegiate and professional athletes. Using American football as an example, 17% to 30% of high school athletes have persistent symptoms greater than 21 days following injury, ^, and 10% to 15% of collegiate athletes have symptoms beyond 10 days, while it is uncommon for professional athletes to experience persistent symptoms beyond 7 days.

Although a small number of patients may have symptoms that persist for 1 year, several reports from specialty concussion clinics in rehabilitation have described children and adults who present for treatment with continued symptoms that have persisted for 2 to 5 years following injury, which may represent up to 20% of the patients with mTBI who are referred for care in these specialty clinics.

Several terms have been used to characterize symptoms following a concussion, such as postconcussion syndrome (PCS), persistent postconcussion syndrome, persistent postconcussion symptoms (PPCS), prolonged recovery, protracted recovery, ^, or slow-to-recover (see Table 23.1 ). Importantly, there is continued controversy related to the time period used to classify individuals into one of these categories and what the underlying cause of the continued symptom complaint may be. Barlow and colleagues and Yeates and colleagues showed individuals who endorse somatic, cognitive, emotional, and/or behavioral symptoms following a biomechanical force to the head recover differently than those who endorse similar symptoms following an injury to the body without sustaining a hit to the head. ^, Barlow and colleagues conducted one of the largest prospective, population-based studies comparing symptom complaints of children (aged 0 to 18 years) after mTBI (as defined by the American Congress of Rehabilitation Medicine) to children who presented to the ED with an extracranial injury (ECI). Three months after injury, 11% of children were symptomatic in the mTBI group compared with 0.5% in the ECI group. Between group differences were even larger when considering children and adolescents between the ages of 6 and 18, where 13.7% of the mTBI group were symptomatic 3 months following the injury compared with only 1% of the ECI group.

For simplicity, but not to suggest consensus in the literature related to proper classification of such individuals, we will use the term PPCS to refer to adults who continue to be symptomatic 10 to 14 days following injury and children (aged 0 to 18 years) who continue to be symptomatic 28 to 30 days following injury. Risk factors and outcomes associated with PPCS and treatment options for different clinical profiles will be reviewed in later sections.

Recognize

Parents, coaches, spectators, and most importantly licensed medical professionals must understand that the brain can undergo a neurometabolic crisis without the head coming in contact with an object or the brain coming in contact with the inside of the skull. ^{, ,} The only requirement for a concussive event is the presence of a large enough acceleration/deceleration force, which can result from a direct blow to the head, or a blow to the body, that subsequently causes a whiplash movement of the head and neck. Importantly, the injury does not require loss of consciousness, loss of memory, or the presence of apparent neurological decline. ^, Suspected diagnosis of SRC can include one or more of the following clinical domains :

• •
  

  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 changes (e.g., irritability)

  
  
• •
  

  Cognitive impairment (e.g., slowed attention speed)

Given the circumstances that may provide sufficient force to cause a functional injury, combined with the fact that such signs and symptoms can be observed or reported following physical exertion in a nonconcussed athlete, ^{, ,} it can be difficult for the medical professional to make the correct choice to Recognize and Remove in every case. It is therefore strongly recommended that the medical professional always error on the side of caution. ^, Once a concussion is suspected, the athlete should be removed from participation in the sport, and the athlete will not return to participation: (1) within the same day, and (2) until an evaluation by a licensed medical professional (Evaluate) has been completed.

Remove

There is overwhelming agreement across position statements and consensus reports that an athlete who is suspected of sustaining a concussion should not return to participation within the same day. ^{, ,} In fact, this recommendation is mandated by law in all 50 states in the United States with regard to children and adolescent concussions. Athletes are removed from participation in sports, especially contact sports, to remove the risk of impact during a time when the brain is vulnerable to damage from an initial injury. The time period of this vulnerable state is unclear, as it has been shown to last up to 5 days in rodent models, but it is not known how this time frame translates to human populations. Therefore it is important to note, the medical professional is not withdrawing the athlete from physical activity in general, although there is evidence that vigorous exercise during this vulnerable period of brain recovery can lead to delayed recovery in rodent models of mTBI ; instead, the athlete is removed from participation at the time of suspected concussion to reduce the risk of another mechanical force occurring on an already injured brain during the acute neurometabolic crisis, an event known as the rare but potentially dangerous second impact syndrome. ^,

If a concussion is suspected, medical personnel must address first aid issues including an assessment of the “ABCs” (airway, breathing, circulation). If any of these are compromised, or if there is prolonged loss of consciousness, seizure, suspicion, or evidence of cervical spine instability or a rapidly deteriorating level of consciousness, emergency medical services should be activated immediately. ^,

Evaluate

In the majority of cases the athlete is able to leave the playing area independently or with assistance from medical personnel and should be escorted to a safe, isolated environment for a sideline evaluation. The objective of the sideline evaluation is to provide a rapid screening for a suspected SRC that may rule out the need for urgent referral to emergency services to address critical medical conditions (e.g., hemorrhage, elevated intracranial pressure, cervical spine instability).

The sideline evaluation should be composed of tests and measures that assess the functional system domains known to be affected by concussion, and at a minimum should include a neurocognitive, motor control, and symptom complaint assessment, ^{, ,} which could be accomplished by using the Sport Concussion Assessment Tool 5 (SCAT5) or Standardized Assessment of Concussion (SAC), combined with a physical test and a self-report checklist for symptom complaints (see Table 23.3 ). The following section describes the tests and measures that should be used in the sideline evaluation. The National Institute of Neurological Disorders and Stroke (NINDS) has supported the collaboration of basic science researchers, clinician-researchers, and clinicians to develop a recommendation for Common Data Elements (CDE) to be used in the assessment of individuals following SRC during the acute (less than 3 days), subacute (3 days to 3 months), and chronic (greater than or equal to 3 months) phases of recovery following concussion. Recommendations from the NINDS CDE can be obtained at https://www-commondataelements-ninds-nih-gov.easyaccess2.lib.cuhk.edu.hk/SRC.aspx# tab=Data_Standards .

Balance assessment

Balance Error Scoring System.

The Balance Error Scoring System (BESS) is a clinical balance assessment of postural stability, which is a component of the SCAT5 and can be completed within 5 minutes. ^{, ,} The BESS was designed to evaluate steady-state balance for clinicians without instrumented laboratory equipment. The BESS has been validated in children, adolescents, and adults with concussion, and has compared favorably to laboratory-based posturography tools such as the sensory organization test (SOT). The BESS consists of three stances: double-leg stance (hands on hips and feet together), single-leg stance (standing on the nondominant leg with hands on hips), and a tandem stance (nondominant foot behind the dominant foot) in a heel-to-toe fashion. The six testing conditions are shown in Fig. 23.1 . The stances are performed on a firm surface and on a foam surface with the eyes closed, with errors counted during each 20-second trial. An error is defined as any one of the following: opening eyes, lifting hands off hips, stepping, stumbling or falling out of position, lifting forefoot or heel, abducting the hip by more than 30 degrees, or failing to return to the test position in more than 5 seconds. Multiple errors that are committed simultaneously are counted as a single error. The maximum number of errors in each trial is 10, and the maximum number of errors in total is 60.

Six Conditions of the Balance Error Scoring System to Assess Balance Performance in Acute Concussion.

Stances used in Balance Error Scoring System: (A) double-leg stance; (B) single-leg stance (standing on the nondominant limb); (C) tandem stance; (D) double-leg stance with foam; (E) single leg on foam; and (F) tandem stance on foam.

(Adapted from Bell, 2011. )

The BESS has high sensitivity (94%), when combined with a brief neurocognitive examination and symptom report, to detect individuals with concussion. However, the sensitivity of the BESS declines rapidly in the days postinjury. ^, Test-retest reliability has been found to be moderate in children aged 9 to 18 years and young adults, with large ranges of intrarater (ICC values of 0.60 to 0.92) and interrater (ICC values of 0.57 to 0.85) reliability depending on the age and mechanism of injury. Scores can be compared with normative data for community-dwelling adults, which may not be appropriate for comparison of performance in the child and adolescent populations. For this reason, Alsalaheen and colleagues described percentile scores for the 6 testing conditions of the BESS in 91 high school students (mean age 15.6 years), which can be used to gauge age-normed performance on each of the conditions for the test. Findings from Alsalaheen and colleagues were consistent with previous studies showing the average number of errors accumulated in high school and collegiate athletes without history of concussion ranges from 12 to 13 errors. Therefore there is evidence to support the use of the BESS test, in combination with cognitive and symptom scales, as a diagnostic measure early following concussion or as a screening tool to compare a patient’s performance to age-match norms for adolescents and adults. However, psychometric properties of the test do not support its use as an outcome measure, as it is not responsive to change in performance over time, nor has it been validated for use in the subacute and chronic stages of recovery following concussion.

Symptom complaint

Postconcussion Symptom Inventory.

The Postconcussion Symptom Inventory (PCSI) is a standardized self-report questionnaire that allows an individual to provide an overall rating of symptoms following concussion. The scale covers six domains: affective, amnesia, cognitive, fatigue, physical, and sleep. The PCSI was modified from the original Postconcussion Scale for appropriate use in children. The PCSI has three forms for children of different ages; the PCSI-SR5 ( https://www.commondataelements.ninds.nih. gov/ReportViewer.aspx?/nindscdereports/rptNOC&rs:Command= Render&rc:Parameters=false&crfID=F2351 ) for ages 5 to 7 years; the PCSI-SR8 ( https://www-commondataelements-ninds-nih-gov.easyaccess2.lib.cuhk.edu.hk/ReportViewer.aspx?/nindscdereports/rptNOC&rs:Command=Render &rc:Parameters=false&crfID=F2355 ) for ages 8 to 12 years; and the PCSI-SR13 ( https://www-commondataelements-ninds-nih-gov.easyaccess2.lib.cuhk.edu.hk/ReportViewer.aspx?/nindscdereports/rptNOC&rs:Command=Render&rc:Parameters=false&crfID=F2354 ) for children aged 13 to 18 years. The tool has been found to have fair-to-good to excellent reliability with ICC values of 0.65 to 0.89 over a 2-week testing period for the four patient-centered questionnaires. A questionnaire has also been developed for parents to report observations of symptom complaints in their children aged 5 to 18 years (PCSI-P; https://www-commondataelements-ninds-nih-gov.easyaccess2.lib.cuhk.edu.hk/ReportViewer.aspx?/nindscdereports/rptNOC&rs:Command=Render&rc:Parameters= false&crfID=F1978 ). Interestingly, for individuals following concussion, parent-child concordance was low to moderate for individual symptom but moderate to strong for the subscales and the total score of the PCSI. Test-retest reliability of the parent administered test has not been reported, and no information related to the responsiveness to change in the measure has been established.

Post concussion symptom scale.

The PCSS is a portion of the SCAT5 that allows the patient to identify symptoms they are experiencing and attempts to quantify the severity of each symptom ( Fig. 23.2 ). The PCSS requires the patient to rate the severity of 22 different symptoms of concussion on a 0 to 6 scale, with higher scores indicating greater severity of symptoms. Patients can be assigned a symptom severity score from 0 to 132.

(A) Postconcussion symptom scale within SCAT5. (B) Postconcussion symptom score checklist recommended for children, kindergarten to sixth grade.

(A, Modified from McCrory P, Meeuwisse WH, Aubry M, et al. Consensus statement on concussion in sport: the 5th International Conference on Concussion in Sport held in Belin, October 2016. Br J Sports Med . 2017;51:838–847. B, Modified from McCrory P, Meeuwisse WH, Aubry M, et al. Consensus statement on concussion in sport: the 4th International Conference on Concussion in Sport held in Zurich, November 2012. Br J Sports Med . 2013;47[5]:250–258.)

In the subacute and chronic stages of recovery, the scale has been validated for individuals with PPCS, though there are no cutoff values reported to rule in/out the condition. Instead, there are established norms for males and females, which the rehabilitation specialist could use to quantify symptom severity. The scale can also be used as an outcome measure to monitor within subject changes in the number and intensity of symptom complaints over time. The PCSS was found to have a standard error of measurement (SEM) value of 5.3 points for high school and collegiate males and females who have sustained a concussion.

Rivermead Post-Concussion Symptoms Questionnaire.

The Rivermead Post-Concussion Symptoms Questionnaire (RPQ) is a 16-item self-report questionnaire in which patients rate the severity of cognitive, emotional, and physical symptoms in comparison with how the patient perceived they were functioning prior to their injury. Items in the RPQ can be divided into two subcategories: the RPQ-3 and the RPQ-13. The RPQ-3 is associated with common sequela of postconcussive symptoms (e.g., headaches, dizziness, nausea and/or vomiting) that often occur early following the injury (score range 0 to 12). The RPQ-13 is associated with having a greater impact on individuals’ participation, psychosocial functioning, and lifestyle (score range 0 to 52). For both subcategories, a higher score indicates a more impaired condition. The RPQ has been shown to be a valid measure of outcome, particularly after a mild to moderate head injury.

Health and Behavior Inventory.

The Health and Behavior Inventory (HBI) is a 50-item self-report questionnaire, which requires parents and children to rate the frequency of somatic, cognitive, emotional, and behavioral symptoms over the past week on a four-point scale, ranging from “never” to “often.” Significant parent-child agreement at the item level and on composite symptom dimensions have been reported, revealing two underlying dimensions of the HBI—cognitive and somatic symptoms. ^,

Graded Symptom Checklist.

The Graded Symptom Checklist (GSC) is a 17-item self-rated survey of postconcussive symptoms, where patients score each item on a Likert scale of 0, indicating no symptoms to 6 indicating severe symptoms. The total score ranges from 0 to 102, with lower scores reflecting a lower symptom burden. The tool is estimated to take 2 to 3 minutes to complete.

The sideline evaluation does not need to resemble the full, comprehensive neurological evaluation performed in the clinic by a physician with experience in the examination of individuals with brain injury (Reevaluate) or the complete evaluation used as the preparticipation baseline assessment (both of which may use neuropsychological testing). Although there is debate for the need of the preparticipation assessment across all youth, high school, and collegiate sports, it is recommended that all athletes participating in contact or collision sports undergo a baseline assessment. ^{, ,} It is true that the degree of cognitive, physical, emotional, and/or behavioral change that may occur in the athlete following a concussion can be assessed more accurately when compared with information obtained from a preparticipation assessment, the results of the sideline assessment can be interpreted without a preinjury baseline assessment. Further consideration should be taken when comparing postinjury findings to preinjury baseline assessments as a recent analysis of the test-retest reliability for many tests and measures used in the baseline assessment have poor to fair test-retest reliability with a 1- and 2-year test interval.

Reevaluate

It is beyond the scope of this chapter to describe the clinical interview and physical examination performed by a physician for a patient presenting with symptoms following a concussion. For a full discussion, the reader is directed to the following reviews: Matuszak and colleagues ; Ellis and colleagues ; McKeag and colleagues ; Kutcher and Giza.

There is a strong recommendation that the reevaluation include neuropsychological testing (pencil and paper or computerized), which may be administered without a licensed Neuropsychologist or Speech-Language Pathologist (SLP), but requires the knowledge base and skill set of a Neuropsychologist or SLP to interpret the results of the neuropsychological tests. For the majority of patients, a neurological screening examination will reveal no abnormalities ^, ; however, any focal neurological deficits or severe neck pain presenting with malalignment or radicular symptoms should indicate imaging of the appropriate body area. ^, The objective of the follow-up clinical evaluation, performed by a neurologist or sports medicine physician who is experienced in the examination and treatment of athletes following a concussion, is to determine the diagnosis of concussion, inform medical management, and to determine recommendations for return to play/sport and return to school/learn.

Determination of diagnosis of concussion

As mentioned previously, no single test or battery of tests has the absolute sensitivity and specificity to diagnose a concussion; therefore concussion is a clinical diagnosis and requires the judgment of a physician. For this reason, a classification system has been proposed, which is based on the level of certainty for diagnosis of concussion being possible, probable, or definite. The physician should consider if the mechanism of injury and the signs and symptoms follow a reasonable pattern and time course of concussion. The natural course of concussion being early symptom provocation within the first 1 to 2 days of injury improves gradually over time, given that no introduction to exacerbating activities occurs in that time. ^, Therefore an athlete who was unresponsive for ten seconds following a head-to-head collision in a soccer match who presents 36 hours later with headache, dizziness, and difficulty concentrating while reading would have a reasonable mechanism of injury (witnessed head-to-head collision) combined with a decline in mental status (loss of consciousness) to meet the criteria for a diagnosis of definite concussion. However, in the case of the athlete with a prior medical history of migraine who presents to the physician with complaints of headache, dizziness, and nausea exacerbated by physical exertion, which began 2 weeks following a cross-country event where the athlete states she “may have hit her head,” concussion is not the most likely cause of the clinical presentation given the absence of a reasonable mechanism of injury, the extensive delay in symptom provocation, and the symptoms that mimic a known comorbidity of migraine. The female cross-country athlete would likely be diagnosed with possible concussion, and the medical management of whether to treat as though this female athlete has a concussion would be the physician’s discretion.

Medical management

Some postconcussion injury symptoms may be addressed in the early stages with pharmacological therapies. Following concussion, pharmacological agents can be prescribed to treat headache, sleep disturbances, nausea, mood disorders, and cognitive deficits (e.g., attentional deficits), as they are indicated for nonconcussed patients. Table 23.5 provides examples of commonly prescribed medications and side effects to manage postconcussion symptoms. It is important to note there is limited evidence demonstrating efficacy of such medications to address symptoms following concussion, and to date, there is still no FDA-approved pharmacological treatment for SRC. ^, Expert opinion suggests that medications should be tapered and then limited 2 to 10 days following the concussion, and then stopped by 2 weeks postinjury. In the case of PPCS, pharmacological interventions should be combined with active rehabilitation programs and lifestyle management for optimal treatment.

The final outcome of the reevaluation by a physician is to determine return to play/sport and return to school/learn recommendations. Given the absence of a direct method for measuring the pathophysiology of the injury to determine when the neurometabolic cascade has recovered (i.e., physiological recovery), once the patient is asymptomatic, he/she should engage in routine activity and begin the process of graduated exertion. For information related to rest and activity guidelines following concussion, see “Recommendations for Return to Play and Return to School/Learn.” A critical point related to return to play that licensed medical providers must consider is that student-athletes must be asymptomatic prior to beginning a graduated return to activity, and should not be taking any pharmacological agents that may mask or modify symptom provocation when the decision to return to full participation is determined.

Risk reduction/prevention of sports-related concussion

Perhaps no other topic related to concussion has engrossed the general public more than how to reduce the risk for SRC, especially in children. Many organizations have disseminated information to school personnel, parents, coaches, athletes, and clinicians related to prevention of SRC. The most well-known program is the CDC’s “Head Up to Schools: Know Your Concussion ABC’s.” As a result of the high incidence of concussion and the limited knowledge of the long-term consequences associated with concussion (e.g., chronic traumatic encephalopathy [CTE], dementia, mental health disorders), there has been misinformation related to what types of actions and/or policies are effective in reducing the risk of concussion. Table 23.6 provides a list of factors and characteristics associated with concussion risk.

It is well documented that a history of prior concussions is a strong risk factor for subsequent concussion. Guskiewicz and colleagues found a dose-response relationship between the number of prior concussions and the likelihood of sustaining a future concussion, where collegiate football players with a history of three or more previous concussions were three times more likely to sustain a concussive injury than those without a history of concussion. It is difficult to determine if these individuals have a decreased threshold/increased vulnerability due to never achieving a full physiological recovery, or if the phenomenon could be explained by “history repeating itself,” as these individuals continue to put themselves in high-risk situations that increase the likelihood of sustaining a sufficient blow to the body/head. Still, this explains the importance of obtaining information related to the number of previous concussions in a medical evaluation (preparticipation baseline assessment or reevaluation), as the athlete can be identified as high-risk for concussion, which should impact future decisions made by the medical team. Identification of high-risk athletes can also be an opportunity for education to the athlete related to SRC prevention. The strongest and most consistent evidence leading to decreased incidence of SRC has been the adoption of policy to eliminate body checking in ice hockey for youth under the age of 13. Other strategies used with the objective to reduce risk for SRC, such as helmets in American football and soccer or use of mouthguards, have not provided clear results in decreasing the risk for SRC. Perhaps most surprising is the evidence that policy changes for fair play rules in youth ice hockey, tackle training without helmets and shoulder pads in youth American football, and tackle technique training in professional rugby do not lead to a reduction in SRC risk. There is also insufficient evidence to determine whether age or level of competition (e.g., youth, collegiate, amateur, professional) increases the risk of SRC ; however, the argument could be made for continued attention toward reducing risk of SRC in children due to the potential added vulnerability of the developing brain at this age.

Potential long-term effects associated with sports-related concussion

There is evidence that some former athletes in contact and collision sports experience depression and cognitive deficits later in life. In addition to impaired clinical findings, there is evidence from advanced neuroimaging and electrophysiological studies of changes in brain function, activation patterns, and white matter fiber tracts in athletes with PPCS months and years following injury. Perhaps more concerning, such structural and physiological changes have been identified even when the athlete has achieved clinical recovery (e.g., asymptomatic at rest and with cognitive and physical exertion) and returned to play. For example, Gosselin and colleagues found a reduction in amplitude and increased latency in auditory evoked potentials in 20 symptomatic and asymptomatic athletes compared with 10 control athletes. Interestingly, the asymptomatic athletes had a similar electrophysiological profile to that of the symptomatic athletes, suggesting continued physiological impairment in athletes who were determined to be clinically recovered. At this time, it is unclear how to interpret these findings as abnormal brain activation patterns and white matter tract findings are not specific to concussion injury, and, due to a lack of methodologically sound, longitudinal investigations, the impact of structural and functional changes in neuroimaging studies on an individual’s function across his or her life-span is unknown.

Due to the current level of discourse related to the association between neurodegenerative disease (e.g., Alzheimer disease and CTE) and concussion, it is worth discussing the state of evidence for the causal relationship between these two conditions. The most extensive review related to long-term effects of SRC was completed by Manley and colleagues, who reviewed 47 studies that investigated neuroimaging, clinical, and neuropathology outcomes in athletes who sustained a concussion. The authors concluded there is emerging evidence that some retired athletes have mild cognitive impairment, neuroimaging abnormalities, and differences in brain metabolism disproportionate to their age, and there is an association between cognitive and psychological deficits and a history of multiple concussions in former athletes. However, the authors emphasize that the majority of former athletes report functioning at a similar level to the general public and are not at increased risk for death by suicide. Further, former high school American football players do not appear to be at increased risk for neurodegenerative diseases later in life. Finally, in terms of the link between CTE and repeated neurotrauma, there is consensus that a cause-and-effect relationship has not been established between neurodegenerative disorders and SRCs or exposure to contact sports; thus the implication that repeated concussion causes CTE remains undetermined. ^,

Retirement from sports

For a select number of athletes, it may be important for medical professionals to discuss retirement from continued participation in sports-related activities, especially those with increased risk of concussion in contact or collision sports. At the foundation of this decision is consideration of the potential risks of prolonged or permanent neurological effects weighed against the positive aspects of continued participation in the sport, which may include the athlete’s personal athletic goals (e.g., future aspirations of participation at a professional level), financial incentives (e.g., scholarship or athletics as a career), and/or the individual’s identity as an athlete. Unfortunately, the decision for retirement depends on many factors, for which there is limited supportive evidence to be used for guidance as there is uncertainty related to the long-term effects of repeated concussion.

Kutcher and Giza provide three scenarios that medical professionals should consider in the decision to recommend retirement from contact sports: (1) evidence of a clear lowering of a threshold for injury, meaning that over time, less force is required for an athlete to acquire postconcussion symptoms; (2) cases where the clinical syndrome is more severe than the average presentation and may last for several weeks, which outweighs the benefits of playing the sport; and (3) cases where an athlete demonstrates objective signs of declining or persistently impaired brain function (e.g., neuropsychological testing and/or diminished academic/work performance) without a plausible explanation other than exposure to impact forces (e.g., depression, migraine headache). In addition to the considerations provided by Kutcher and Giza, medical professionals may use the Columbia SRC Retirement Algorithm proposed by Davis-Hayes and colleagues to determine when a discussion related to retirement from sport may be indicated versus circumstances where a recommendation for retirement from sport should be provided to an athlete. For example, medical professionals should provide a recommendation for retirement where there is evidence of structural abnormality on routine neuroimaging (e.g., frontotemporal contusions or gliosis). Conversely, in cases where the cumulative effects of repeated concussions lead to relative contraindications for continued exposure, retirement from sports or recommendations for a replacement activity with reduced risk for contact or collisions may be warranted. Symptoms or neurological signs persisting greater than 3 months, persistent cognitive impairment, diminished academic performance or social engagement, and evidence of a decreased threshold to trigger postconcussion symptoms may be useful criteria to suggest altered activities to prevent further injury.

What is the evidence for physical and cognitive activity in acute concussion?

Conversely, there is evidence that rather than strict rest, engaging in moderate levels of physical and cognitive activity can be beneficial for decreasing the burden of postconcussion symptoms, promoting earlier return to baseline performance on standardized neuropsychological and physical assessments, earlier return to play/sport, and earlier return to school/work. Majerske and colleagues performed a retrospective chart review and found that individuals who engaged in moderate levels of exertion (slow jogging and sports practice) demonstrated better outcomes on neuropsychological testing compared with individuals with the least (no school or exercise) or greatest (full school and competition participation) level of activity. Lawrence and colleagues reviewed charts of adolescents (aged 15 to 20 years) who engaged in either self-initiated or physician-prescribed physical activity within 14 days of an SRC. Although each athlete was symptomatic at the time of initiating aerobic exercise, the authors reported a shorter time to initiation of aerobic exercise (e.g., earlier physical activity) was associated with faster full return to sport and school/work-related activities. Grool and colleagues conducted a large prospective study investigating the association between participation in physical activity within 7 days and PPCS in children aged 5 to 18 years. Participants who met the criteria for concussion as defined by the CISG completed surveys (via internet or phone) related to current level of physical activity and symptom complaint (using the PCSI). Among 2413 participants, 69.5% participated in some form of physical activity within 7 days following concussion, primarily with light aerobic exercise, which was associated with lower risk of symptom complaint at 28 days compared with no physical activity. The proportion of participants with PPCS at 28 days was 28.7% compared with 40.1% for those engaging in early physical activity versus no activity, respectively. Therefore it appears that moderate physical and mental activity during the acute phase of recovery may be beneficial.

What criteria should be used to determine recovery?

Similar to diagnostic testing, at this time there is no single test or biomarker that can be used to determine prognosis for recovery following concussion. ^, Here, it is important to distinguish two types of recovery: clinical recovery and physiological recovery. Clinical recovery is the proxy that medical professionals (typically a neurologist, sports medicine physician, or rehabilitation medicine physician) use to determine an individual is able to perform all previous life activities without presence or exacerbation of baseline symptoms. The operational definition of clinical recovery provided by the CISG encompasses a resolution of postconcussion-related symptoms and a return to clinically normal balance and cognitive functioning, which results in a return to normal activities, including school, work, and sport. However, using clinical recovery as the benchmark for return to activities, it is unclear to what extent there is continued physiological dysfunction (e.g., impaired metabolic activity, abnormal synaptic and neurotransmission, impaired cerebral blood flow, inflammation), as neurobiological recovery might extend beyond clinical recovery in some individuals. Results from neuroimaging studies ^, suggest that physiological recovery time may outlast the time to clinical recovery. However, many of the neuroimaging techniques used to identify such dysfunction are not available in most medical clinics and are not used as a standard of care for individuals following concussion. Further, abnormalities found on neuroimaging studies are not specific to injury following concussion. Still, advanced neuroimaging and fluid biomarkers continue to be investigated for use in identifying physiological recovery.

At this time, fluid biomarkers to identify concussion injury are in development and are critical to the ability to diagnose and determine prognosis for recovery. On February 14, 2018, the FDA released approval for TBI Endpoints Development (TED) and TRACK TBI to study ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) and glial fibrillary acidic protein (GFAP), which are proteins released from the brain into the blood after brain injury. A multicenter prospective study of 1947 adult blood samples showed that the Banyan Brain Trauma Indicator, a blood test that measures the presence of UCH-LI and GFAP, was able to predict intracranial lesions that would not appear on standard imaging (e.g., computed tomography). Many other neuroimaging techniques and biomarkers for impaired neuroplasticity, inflammatory processes, and autoimmune antibodies are being investigated to better understand factors associated with comorbidities and prolonged recovery. For a discussion on neuroimaging and fluid biomarker research in concussion, the reader is referred to the following reviews: Makdissi and colleagues, Kevin and colleagues, Dambinova and colleagues, and Schmidt and colleagues.

The physician must rely on behavioral measures as a proxy for recovery; therefore at this time, recovery is synonymous with clinical recovery because the full physiological recovery process remains unclear. For this reason, clinical recovery constitutes waiting until the patient is asymptomatic and has returned to baseline on cognitive and physically based performance measures, ^{, ,} before initiating a graduated return-to-play (RTP) strategy.

Recommendations for return to play and return to school/learn

Statements generated from international consensus, position statements, practice guidelines, and reviews related to RTP (also referred to as return to sport and return to activity) can be found in Box 23.1 .

Prognosis and outcomes following sports-related concussion

There is a critical need to determine demographic characteristics and clinically relevant factors that are associated with clinical recovery prior to injury, at the time of injury, and postinjury. Such information would be useful for decision making for medical and rehabilitation approaches. For example, demographic and preinjury characteristics could be used by medical professionals to identify athletes who are at high risk for developing PPCS during preparticipation screenings and ensure careful monitoring and appropriately timed referrals for pharmacological and/or rehabilitation therapies in the event of a concussion. In addition, knowledge of variables at the time of injury and following the injury that contribute to a protracted recovery could impact clinical decision making for medical professionals on the field and in the clinic to better utilize resources for those at highest risk for protracted recovery, to promote successful and timely return to play and return to learn strategies.

The Predicting and Preventing Postconcussive Problems in Pediatrics (5Ps) study was designed to develop and validate a clinical risk score in order to stratify PPCS risk after acute concussion in children and youth. Zemek and colleagues completed a multicenter cohort study from 9 pediatric EDs within the Pediatric Emergency Research Canada network, where children aged 5 to 18 years underwent a comprehensive evaluation in the ED and completed electronic surveys at 7, 14, and 28 days following a diagnosis of concussion. Out of 47 risk factors associated with PPCS (defined as 3 or more new or worsening symptoms as measured by the PCSI at 28 days compared with prior injury state), Zemek and colleagues found 9 factors that independently predicted PPCS at 28 days, including age, sex, prior concussion and symptom duration, physician-diagnosed migraine history, answering questions slowly, number of errors for BESS tandem stance position, headache, sensitivity to noise, and fatigue. Depending on the PPCS risk score, the group was able to establish a probability of developing PPCS at 28 days. Although the clinical utility of the PPCS risk score needs to be established, the use of such a stratification system has the potential to individualize concussion care and lead to the identification of children who are at risk for developing PPCS during the acute stage of recovery following a concussion.

A systematic review completed as a part of the CISG conference synthesized the evidence regarding predictors of clinical recovery following concussion. In general, Iverson and colleagues reported that the literature is mixed with positive and negative findings related to predictive factors of clinical recovery, because many of the included studies were found to use different criteria to establish clinical recovery, which made it difficult to provide definitive conclusions. Still, Iverson and colleagues reported that preinjury mental health problems (prior personal or family psychological history), especially depression, and prior concussions appear to be risk factors for PPCS. Importantly, adolescent years might be a particularly vulnerable time for experiencing persistent symptoms, with greater risk for girls than boys. ^{, , ,}

It is also worth noting the variables that were not found to be associated with increased risk for protracted recovery or the development of PPCS, such as complaint of dizziness, initial severity of cognitive deficits, or development of oculomotor dysfunction, and individuals with prior cognitive and learning disabilities, and individuals with prior cognitive and learning disabilities (e.g., attention deficit hyperactivity disorder). There were also inconsistent findings related to “Red Flags” and memory assessment (e.g., loss of consciousness and posttraumatic amnesia) at the time of injury leading to PPCS.

A list of factors associated with increased risk for PPCS (continued symptoms beyond 14 days in adults and 28 days in children) is provided in Table 23.6 .

Prognosis and outcome following non–sports-related concussion in adults

To date, most studies evaluating outcomes for individuals following concussion have been directed almost exclusively toward clinical recovery after SRC. However, young and older adults sustain mTBI due to falls, motor vehicle accidents, physical assault, and participation in recreational activities. Similar to student-athletes, the majority of adults who sustain a concussion will resume normal activities within 10 to 14 days; however, a minority of these individuals will endorse PPCS and experience a slow return to participation in meaningful activities, perhaps the most important of which is return to work (RTW).

Following concussion, perhaps due to instructions provided by a physician, but more than likely due to postconcussion symptoms, many patients will miss work for a period of time. Absence from work can lead to lost or reduced income, psychological stress due to pressures placed on family relationships, and secondary physical and mental health conditions due to prolonged withdrawal from typical activities (e.g., deconditioning and psychological distress). All of these factors can add to normal work-related, household, and financial stressors already present in most adult’s lives.

Because of various external or internal pressures, some adults will RTW while still symptomatic, which can lead to an unsuccessful return and more time away from productive work, resulting in profound negative financial and emotional consequences. Even for those whom are asymptomatic, it is possible that the increased physical or cognitive load may cause somatic, cognitive, emotional, and/or behavioral impairments. Despite these well-known complications that can create barriers for successful RTW, there is a paucity of literature related to RTW following mTBI.

The International Collaboration on mTBI Prognosis group completed a systematic review of the literature from 2001 to 2012 to update the previous World Health Organization Collaborating Centre Task Force on mTBI findings on RTW in 2004. The group reported most workers returned to work within 3 to 6 months ; however, RTW rates varied widely based on the time from injury and the geographic area of the investigation. For example, as many as 84% and as little as 41% of individuals were found to RTW 1 week following mTBI, while other investigations reported a range of 25% to 100% of individuals returning to work 1 month postinjury. Wäljas and colleagues followed a group of 109 patients with an average age of 37.4 years, 76% of whom were working full time, 5.6% working part time, with the remaining patients being students, who were diagnosed with an mTBI at a University Hospital ED in Finland, and found the vast majority of the group (91.7%) returned to work within 2 months. Due to the repeated measure design of the study, the following RTW rates were reported; 46.8% RTW at 1 week, 59.6% RTW at 2 weeks, 70.6% RTW at 1 month, 91.7% RTW at 2 months, and 97.2% RTW at 1 year following mTBI.

One major limitation of studies investigating RTW following mTBI is considering whether the patient achieves a full return to preinjury work-related activities. Two studies have somewhat disparate findings for full RTW rates at 6 months following injury, where 41.7% of individuals presenting to an outpatient concussion clinic and 76% of individuals presenting to an ED were reported to have a full RTW 6 months postinjury.

Perhaps it is obvious that work disability includes time off from work and sick leave, but it also incorporates reduced productivity or working with functional limitations. ^, However, few studies have evaluated RTW as a continuum based on a RTW hierarchy considering reduced workload, a change in roles/responsibilities, or lower productivity due to functional impairments such as cognitive deficits or symptom provocation. ^{, , ,} Evaluating RTW as a dichotomy (employed vs. unemployed) rather than a hierarchy can lead to a drastic underestimation of disability an individual may experience when attempting to fully return to preinjury work. In 79 patients recruited from concussion specialty clinics in Vancouver, Canada, Silverberg and colleagues reported that although 58.2% (46) of patients returned to any level of work, only 41.7% of patients fully returned to their preinjury work responsibilities at 6 months following injury. Importantly, at 6 months, 1 in 4 patients who had returned to work were still on modified duties, working reduced hours, or receiving accommodations, or took a different, less demanding job. Further, nearly 50% of patients who fully returned to work continued to report multiple somatic, cognitive, and emotional symptoms.

A secondary objective of the study by Wäljas and colleagues was to examine factors that influence RTW status in individuals who are slow to recover following mTBI. Wäljas and colleagues concluded appearance of the following combination of factors within the first 4 weeks following mTBI strongly predicted RTW status: age, multiple bodily injuries, intracranial abnormalities on CT scan the day of injury, and fatigue ratings. Consistent with other studies, the authors reported that injury severity variables (e.g., duration of unconsciousness, Glasgow Coma Scale score, and duration of posttraumatic amnesia) were not associated with length of time to RTW. ^,

Based primarily on the Veteran’s Affairs/Department of Defense (VA/DoD) Clinical Practice Guideline for Management of Concussion/mTBI, Marshall and colleagues provided the following recommendations for RTW following a concussion :

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  In some cases, vocational modifications are required and may include:

  
  
  
  
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    Modification of the length of the workday

    
    
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    Gradual work reentry (e.g., starting at 2 days/week and expanding to 3 days/week)

    
    
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    Additional time for task completion

    
    
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    Change of job

    
    
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    Environment modifications (e.g., quieter work environment)

  
  
  
  
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  Individuals who continue to experience persistent impairments following mTBI or those who have not successfully resumed preinjury work duties following injury should be referred for an in-depth vocational evaluation by clinical specialists and teams (e.g., occupational therapist, vocational rehabilitation counsellor, occupational medicine physician, neuropsychologist, SLP) with expertise in assessing and treating mTBI.

  
  
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  A referral to a structured program that promotes community integration (e.g., volunteer work) may also be considered for individuals with PPCS that impede return to preinjury participation in a customary role.

Symptom complaint

A high prevalence of complaints of headache (83%), dizziness (65%), and confusion (57%) is reported by athletes following SRC. Other common symptoms endorsed by patients who have sustained a concussion include nausea, intermittent vomiting, disturbances of balance or gait, tinnitus, photophobia, phonophobia, difficulty focusing, slowed speech, lightheadedness or fogginess, extreme fatigue, and other impairments in cognitive processing and memory. ^{, , ,} Following concussion, 10% to 33% of patients will continue to endorse symptoms, which may persist for months or even years. ^, Although the time course of recovery that characterizes PPCS continues to be debated and has changed over time, ^{, , ,} PPCS should be considered if symptoms continue for longer than 10 to 14 days for adults and more than 28 days for children.

Special consideration should be taken for clinicians providing care to children and adolescents with persistent symptoms following concussion. Often children and adolescents do not have the insight or vocabulary to identify or articulate the symptoms they are experiencing. It is recommended that clinicians working with this population, especially children, phrase interview questions in contexts that are appropriate to the child’s life, such as inquiring about the child’s experience for specific activities such as going to the grocery store, walking up the stairs, playing video games, and riding in the car, and will often illicit confirmatory evidence that those activities make the child feel anxious, foggy, or “not right.” Also, it is important to consider the method of obtaining symptom complaints can influence the number and severity of the symptoms reported, ^, and on average, even healthy children and young adults will endorse concussion symptoms listed on common symptom complaint assessments. The Pediatric Visually Induced Dizziness (PVID) Questionnaire is an example of a tool that has been developed and validated alongside the Pediatric Vestibular Symptom Questionnaire (PVSQ) to assess visually induced dizziness (ViD) in children aged 6 to 17 years. The PVID shows utility in identifying and quantifying symptoms of ViD related to concussion, migraine, and other vestibular conditions—an important consideration in the assessment of children and adolescents, as they have been found to rely on the visual system as the predominant system for balance and to resolve sensory conflict until multisensory processing reaches maturation, even in the absence of injury.

Tests and measures to evaluate persistent postconcussion symptom complaint

The NINDS CDE recommends that symptom complaints of patients with PPCS be monitored using the PCSI, PCSS, RPQ, and the HBI. Information related to these self-reported symptom complaint questionnaires has been provided earlier in the chapter. A review of the decision making process of the rehabilitation specialist as it relates to symptom complaint is discussed here.

Clinicians are advised not to use the results from either the PCSI, PCSS, RPQ, or the HBI alone to direct their care. Symptoms can be nonspecific and can mimic symptoms associated with chronic pain, depression, and anxiety disorders ; therefore symptom complaints alone cannot be used to identify underlying impairments of functional systems that may cause common symptom complaints following concussion. ^{, ,} For example, a symptom complaint of a headache could be due to visual problems or cervical spine dysfunction, or could be related to prior history of migraines. Similarly, a symptom complaint of dizziness could be caused by orthostatic hypotension, vestibulo-ocular problems, or anxiety associated with the inability to return to sports, school, or social activities. Further, symptom complaints endorsed by individuals following a concussion are commonly reported among nonconcussed individuals. ^{, ,} For athletes specifically, the accuracy of symptom report from adolescents recovering from SRC has been questioned, as athletes may not disclose concussive signs and symptoms as they may intentionally withhold reporting them or, conversely, they may be motivated to inflate or continue reporting symptoms despite injury resolution as a means to leave a sport. ^{, ,} Therefore symptom complaints alone are not sensitive to either diagnose concussion or to identify underlying causes of dysfunction.

For this reason, the clinical examination should be made up of tests and measures that can provide the clinician with objective data about potential impairments of physical or psychological systems, or personal circumstances that may contribute to the reported symptoms. This point cannot be emphasized enough: the rehabilitation specialist should structure the examination to identify underlying impairments in functional systems and activity limitations so that interventions can be matched to the findings of the physical examination. In our experience, clinicians who rely on symptom complaint to guide decision making do not have successful outcomes in the management of concussion-related functional deficits.

Cognitive/neuropsychological dysfunction

As discussed previously, there is evidence that concussion may lead to neurocognitive dysfunction secondary to axonal shearing, secondary neuronal death, altered cerebral blood flow, and dysregulated biochemical function. ^, In most clinical cases, there are no obvious initial neuroimaging results that identify this damage or dysfunction. However, the pattern of neurocognitive deficits is relatively consistent when evaluated clinically and behaviorally. Although the research debate continues on the existence of a constellation of neurocognitive deficits, the primary deficits reported by researchers, patients, and clinicians include attention, memory, executive functions, word retrieval, and social skills/pragmatics.

Exercise intolerance

Concussion can lead to physiological dysfunction, including neurometabolic challenges, altered cerebral blood flow, and/or autonomic dysfunction. ^{, ,} Patients with concussion have been found to have higher resting heart rates, and there is evidence from imaging studies of abnormal cerebral blood flow volume and distribution in humans both acutely after concussion and in those with PPCS . Such cellular and physiological alterations lead to a mismatch between energy supply and demand that is thought to be a major contributing factor to exercise intolerance and prolonged recovery following concussion.

As mentioned previously, international consensus guidelines provide a strong recommendation for a period of rest (1 to 2 days), followed by a graduated return to activity (see Table 23.7 ). However, the clinician and patient with PPCS are often stuck in a gray area, questioning: What is the optimal amount of rest? When should exercise begin? And how can the exercise progress safely? For this reason, John Leddy’s group at SUNY Buffalo developed a subsymptom exercise tolerance test, the Buffalo Concussion Treadmill Test (BCTT), to identify individuals with exercise intolerance following a concussion and provide clinicians with a tool for guidance in exercise prescription related to return to activity.

Assessment of exercise intolerance: Subsymptom exercise tolerance test

The BCTT has been shown to be a safe ^, and reliable measure, which can be useful for identifying levels of exercise tolerance in patients following SRC, quantifying the clinical severity of the concussion, and developing exercise prescription for patients with PPCS. ^, Using a standardized Balke protocol, patients perform an incremental treadmill exercise test ( Fig. 23.4 ) that is terminated upon provocation of new symptoms, elevation of symptoms beyond established criteria, or maximum exertion is achieved. The starting speed is set to 3.2 to 3.6 mph. During the first minute, the treadmill is set at a 0% incline. After 1 minute, the incline is increased by 1% grade and then by 1% grade each minute thereafter while maintaining the same speed until the patient can no longer continue, whether because of symptom exacerbation or fatigue. Rating of perceived exertion (RPE, using the Borg Rating scale) and symptoms, using a 1- to 10-point visual analog scale (VAS), are assessed every minute. Blood pressure (with an automated or manual cuff) and heart rate (HR) are measured every 2 minutes. For the most accurate information, it has been recommended that a heart rate monitor be worn across the chest during the test (HR, by Polar HR monitor, Model #FIT N2965; Kempele, Finland).

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