Sport-related concussion induces transient cardiovascular autonomic dysfunction

Sensor-Assisted Analysis of Autonomic and Cerebrovascular Dysregulation following Concussion in an Individual with a History of Ten Concussions: A Case Study

INTRODUCTION

Concussion is known to cause transient autonomic and cerebrovascular dysregulation that generally recovers; however, few studies have focused on individuals with an extensive concussion history.

METHOD

The case was a 26-year-old male with a history of 10 concussions, diagnosed for bipolar type II disorder, mild attention-deficit hyperactivity disorder, and a history of migraines/headaches. The case was medicated with Valproic Acid and Escitalopram. Sensor-based baseline data were collected within six months of his injury and on days 1-5, 10, and 14 post-injury. Symptom reporting, heart rate variability (HRV), neurovascular coupling (NVC), and dynamic cerebral autoregulation (dCA) assessments were completed using numerous biomedical devices (i.e., transcranial Doppler ultrasound, 3-lead electrocardiography, finger photoplethysmography).

RESULTS

Total symptom and symptom severity scores were higher for the first-week post-injury, with physical and emotional symptoms being the most impacted. The NVC response showed lowered activation in the first three days post-injury, while autonomic (HRV) and autoregulation (dCA) were impaired across all testing visits occurring in the first 14 days following his concussion.

CONCLUSIONS

Despite symptom resolution, the case demonstrated ongoing autonomic and autoregulatory dysfunction. Larger samples examining individuals with an extensive history of concussion are warranted to understand the chronic physiological changes that occur following cumulative concussions through biosensing devices.

The Evaluation and Management of Concussion to Optimize Safe Recovery

Concussion is a mild traumatic brain injury causing temporary neurologic dysfunction. Symptoms following concussion are variable and generally are expected to resolve within about 1 month, but some patients experience persistent and prolonged symptoms. An early return to safe, symptom-limited activity is now favored, using targeted rehabilitation and treatments. Accommodations may be needed to facilitate return-to-school and work following concussion. Athletes should not be cleared for a full return to sport until they have recovered from a concussion and completed a return-to-play progression, in addition to returning to work/school fully.

A treadmill running research protocol to assess dynamic visual acuity and balance for athletes with and without recent concussion history

Athletes interpret dynamic visual scenes quickly and accurately during physical exertion. It is important to understand how increased exertion may impact vision and cognition following sport-related concussion (SRC).Purpose To examine the effect of a treadmill running research protocol on the assessment of dynamic visual acuity (DVA) and balance for athletes with and without recent history of SRC.Methods Varsity athletes following recent SRC (CONC=12) were compared to athletes without SRC (ATHLETE=19). The DVA task presented a Tumbling 'E' target in four possible orientations during random walk (RW) or horizontal (H) motion at a speed of 30°/s. Participants performed DVA trials standing on a force plate (1000Hz) at four time points: 1) pre-exercise (PRE-EX), 2) immediately (POST1), 3) 10-minutes (POST10), and 4) 20-minutes post- exercise (POST20). Performance was calculated as a change in DVA score from PRE-EX and median response time (RT, ms). Balance control was analyzed using the root mean square of centre of pressure displacement (dCOP).Results Both groups maintained DVA scores for both motion types and exhibited immediate exercise-induced benefits on RT. Both groups had similar change in balance control strategy following treadmill exercise.Conclusion Both groups elicited similar exercise-induced benefits on DVA following exercise. A repeated measures assessment following vigorous exercise may provide meaningful insights about visual and neurocognitive functions for athletes returning to sport following concussion.

Athletic Fear Avoidance in Athletes Receiving Rehabilitation for Sport-Related Concussion: A Preliminary Study

BACKGROUND

Fear avoidance after musculoskeletal injury is avoiding activity due to fear of pain and contributes to persistent symptoms, depression, and disability. Little is known about fear avoidance for sport (athletic fear avoidance) in athletes with sport-related concussion (SRC).

HYPOTHESIS

Athletic fear avoidance after SRC would be elevated at the start of rehabilitation, improve over time, and be associated with postconcussion recovery outcomes.

STUDY DESIGN

Observational study.

LEVEL OF EVIDENCE

Level 4.

METHODS

Athletes in rehabilitation after SRC participated. Testing at initial and discharge visits and 6-month follow-up included Athletic Fear Avoidance Questionnaire (AFAQ), Postconcussion Symptom Scale (PCSS), Profile of Mood States (POMS), and Dizziness Handicap Inventory (DHI). Differences were explored in AFAQ score at initial testing based on sex or age (<18 or ≥18 years). Change in questionnaire scores over time was examined. Association of AFAQ score with other questionnaire scores was determined at each timepoint.

RESULTS

A total of 48 athletes participated: 28 completed initial testing only (INITIAL ONLY), and 20 completed all testing (LONGITUDINAL). Across cohorts, the mean (SD) AFAQ score at initial testing was 24.3 (7.6) points, with no significant difference by sex or age. AFAQ, PCSS, POMS, and DHI scores improved in LONGITUDINAL; the effect size was large from initial to discharge testing (1.0, 1.0, 1.0, and 1.2, respectively) and variable from discharge to follow-up testing (0.52, -0.34, -0.08, and 0.02, respectively). AFAQ scores increased from discharge to follow-up in 3 athletes and were consistently above the mean value in 2 athletes. AFAQ score was significantly correlated to the other questionnaire scores at each timepoint (range, r = 0.36-0.75).

CONCLUSION

Athletic fear avoidance was elevated at the start of SRC rehabilitation, improved over time in most patients, and was associated with postconcussion symptoms, mood, and disability.

CLINICAL RELEVANCE

Athletic fear avoidance may impact recovery after SRC.

Collegiate student-athletes concussion knowledge and attitudes: what a difference a decade Makes

OBJECTIVE

The purpose of this study was to assess changes in concussion knowledge and attitudes amongst incoming intercollegiate student-athletes over the course of a decade (2010-2012 vs 2021-2023).

METHODS

There were 592 student-athletes from 2 cohorts (2010-2012, 2021-2023) who completed the Rosenbaum Concussion Knowledge and Attitudes Survey (ROCKaS) questionnaire which is comprised of a concussion knowledge index (CKI, 0-24) and attitude index (CAI, 15-75) with higher scores reflecting better performance. A three factor ANOVA (Group, Sex, Concussion History) compared performance on the CKI and CAI. Individual questions were compared between groups with a Chi-Square analysis.

RESULTS

For the CKI, there was a significant main effect for Group (2010-2012: 18.5 ± 2.6, 2021-2023: 19.4 ± 2.5, p < 0.001, η 2 = 0.032 ) . For the CAI, there was also a significant main effect for group (2010-2012: 52.9 ± 6.0, 2021-2023: 62.2 ± 6.5, p < 0.001, η 2 = 0.359 ) .

CONCLUSIONS

The results of this study show a modest increase in concussion knowledge; however, large improvements in concussion attitudes were observed between groups. These results suggest a continued improvement in student-athlete concussion awareness and provide specific areas to continue addressing persistent misconceptions.

The Role of Concussion History and Biological Sex on Pupillary Light Reflex Metrics in Adolescent Rugby Players: A Cross-Sectional Study

Background: Concussion examination is based primarily on clinical evaluation and symptomatic reporting. Pupillary light reflex (PLR) metrics may provide an objective physiological marker to inform concussion diagnosis and recovery, but few studies have assessed PLR, and normative data are lacking, particularly for adolescents. Aim: To capture PLR data in adolescent rugby players and examine the effects of concussion history and biological sex. Design: Cross-sectional. Methods: Male and female adolescent rugby union players aged 16 to 18 years were recruited at the start of the 2022-2023 playing season. PLR was recorded using a handheld pupillometer which provided seven different metrics relating to pupil diameter, constriction/dilation latency, and velocity. Data were analysed using a series of 2 × 2 ANOVAs to examine the main effects of independent variables: biological sex, concussion history, and their interactions, using adjusted p-values (p < 0.05). Results: 149 participants (75% male) were included. A total of 42% reported at least one previous concussion. Most metrics were unaffected by the independent variables. There were however significant main effects for concussion history (F = 4.11 (1); p = 0.05) and sex (F = 5.42 (1); p = 0.02) in end pupil diameters, and a main effect for sex in initial pupil diameters (F = 4.45 (1); p = 0.04). Although no significant interaction effects were found, on average, females with a concussion history presented with greater pupillary diameters and velocity metrics, with many pairwise comparisons showing large effects (SMD > 0.8). Conclusions: Pupillary diameters in adolescent athletes were significantly affected by concussion history and sex. The most extreme PLR metrics were recorded in females with a history of concussion (higher pupillary diameters and velocities). This highlights the importance of establishing baseline PLR metrics prior to interpretation of the PLR post-concussion. Long-standing PLR abnormalities post-concussion may reflect ongoing autonomic nervous system dysfunction. This warrants further investigation in longitudinal studies.

Heart Rate Variability in Concussed College Athletes: Follow-Up Study and Biological Sex Differences

Finding reliable biomarkers to assess concussions could play a pivotal role in diagnosis, monitoring, and predicting associated risks. The present study aimed to explore the use of heart rate variability (HRV) in the follow-up of concussions among college athletes and to investigate the relationships between biological sex, symptomatology, and HRV values at baseline and after a concussion. Correlations between measures were also analyzed. A total of 169 (55 females) athletes aged 16 to 22 years old completed baseline testing, and 30 (8 females) concussion cases were followed. Baseline assessment (T1) included psychosocial and psychological questionnaires, symptoms report, and four minutes of HRV recording. In the event of a concussion, athletes underwent re-testing within 72 h (T2) and before returning to play (T3). Baseline findings revealed that girls had higher %VLF while sitting than boys, and a small negligible correlation was identified between %HF and total symptoms score as well as %HF and affective sx. Post-concussion analyses demonstrated a significant effect of time × position × biological sex for %HF, where girls exhibited higher %HF at T3. These findings suggest disruptions in HRV following a concussion and underscore biological sex as an important factor in the analysis of HRV variation in concussion recovery trajectory.

National Collegiate Athletic Association athletic trainers' response to the Arrington settlement: management, compliance, and practice patterns

The primary purpose of this study was to assess Athletic Trainers' (ATs) report of NCAA member institution compliance with the Arrington settlement, the concussion lawsuit vs. the NCAA, and to elucidate compliance predictors. A secondary purpose was to provide a contemporary concussion management clinical practice pattern description among NCAA collegiate athletic trainers. Head Athletic Trainers from NCAA Division I, II, and III completed an electronic questionnaire in August 2020 regarding their institution's response to the Arrington Settlement and their current concussion management clinical practice patterns. The 37-item questionnaire included AT and institution demographics, current concussion management policies, and response to the Arrington settlement with a specific focus on the five settlement requirements. An overall compliance score on the five requirements, compliance on the individual requirements, and concussion management practices are reported with descriptives. Regression was used to identify specific predictors of both overall and individual settlement requirements. An ANOVA compared compliance by NCAA division level. Being pressured to be non-compliant was assessed between sexes by a chi-square. There were 223 respondents (21.8%), and overall compliance was high (4.1 ± 0.7) with the five required Arrington Settlement components. Settlement requirement 1, pre-season baseline testing, and requirement 5, presence of trained personnel at all contact sport practices, had the lowest compliance rates at 44.8% and 73.3%, respectively. The number of sports the institution offered was the only significant predictor of each requirement. There was no difference in compliance between NCAA divisions. Although the overall rate of being non-compliant pressure was low (13.8%), females were 3.28x more likely report being pressured than males. NCAA institutions are generally compliant with the Arrington settlement; however, lack of clarity in the requirements, particularly requirement 1, raises potential concerns. Concussion management practices continue to incorporate multifaceted approaches and are largely consistent with current best practices.

Neuroimaging to enhance understanding of cardiovascular autonomic changes associated with mild traumatic brain injury: a scoping review

BACKGROUND

Cardiovascular changes, such as altered heart rate and blood pressure, have been identified in some individuals following mild traumatic brain injury (mTBI) and may be related to disturbances of the autonomic nervous system and cerebral blood flow.

METHODS

We conducted a scoping review according to PRISMA-ScR guidelines across six databases (Medline, CINAHL, Web of Science, PsychInfo, SportDiscus and Google Scholar) to explore literature examining both cardiovascular parameters and neuroimaging modalities following mTBI, with the aim of better understanding the pathophysiological basis of cardiovascular autonomic changes associated with mTBI.

RESULTS

Twenty-nine studies were included and two main research approaches emerged from data synthesis. Firstly, more than half the studies used transcranial Doppler ultrasound and found evidence of cerebral blood flow impairments that persisted beyond symptom resolution. Secondly, studies utilizing advanced MRI identified microstructural injury within brain regions responsible for cardiac autonomic function, providing preliminary evidence that cardiovascular autonomic changes are a consequence of injury to these areas.

CONCLUSION

Neuroimaging modalities hold considerable potential to aid understanding of the complex relationship between cardiovascular changes and brain pathophysiology associated with mTBI. However, it is difficult to draw definitive conclusions from the available data due to variability in study methodology and terminology.

Role of biomarkers and emerging technologies in defining and assessing neurobiological recovery after sport-related concussion: a systematic review

OBJECTIVE

Determine the role of fluid-based biomarkers, advanced neuroimaging, genetic testing and emerging technologies in defining and assessing neurobiological recovery after sport-related concussion (SRC).

DESIGN

Systematic review.

DATA SOURCES

Searches of seven databases from 1 January 2001 through 24 March 2022 using keywords and index terms relevant to concussion, sports and neurobiological recovery. Separate reviews were conducted for studies involving neuroimaging, fluid biomarkers, genetic testing and emerging technologies. A standardised method and data extraction tool was used to document the study design, population, methodology and results. Reviewers also rated the risk of bias and quality of each study.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies were included if they: (1) were published in English; (2) represented original research; (3) involved human research; (4) pertained only to SRC; (5) included data involving neuroimaging (including electrophysiological testing), fluid biomarkers or genetic testing or other advanced technologies used to assess neurobiological recovery after SRC; (6) had a minimum of one data collection point within 6 months post-SRC; and (7) contained a minimum sample size of 10 participants.

RESULTS

A total of 205 studies met inclusion criteria, including 81 neuroimaging, 50 fluid biomarkers, 5 genetic testing, 73 advanced technologies studies (4 studies overlapped two separate domains). Numerous studies have demonstrated the ability of neuroimaging and fluid-based biomarkers to detect the acute effects of concussion and to track neurobiological recovery after injury. Recent studies have also reported on the diagnostic and prognostic performance of emerging technologies in the assessment of SRC. In sum, the available evidence reinforces the theory that physiological recovery may persist beyond clinical recovery after SRC. The potential role of genetic testing remains unclear based on limited research.

CONCLUSIONS

Advanced neuroimaging, fluid-based biomarkers, genetic testing and emerging technologies are valuable research tools for the study of SRC, but there is not sufficient evidence to recommend their use in clinical practice.

PROSPERO REGISTRATION NUMBER

CRD42020164558.

Clinical Mental Health Measures and Prediction of Postconcussion Musculoskeletal Injury

CONTEXT

The rate of lower extremity musculoskeletal injury (LE MSK) is elevated after concussion; however, the underlying mechanism has not been elucidated. Physical characteristics have been investigated despite poorer mental health being a common postconcussion complaint and linked to MSKs.

OBJECTIVE

To evaluate the role of mental health as a predictor of postconcussion LE MSK.

DESIGN

Case-control study.

SETTING

Intercollegiate athletic training facility.

PATIENTS OR OTHER PARTICIPANTS

A total of 67 National Collegiate Athletic Association Division I student-athletes (n = 39 females) who had been diagnosed with a sport-related concussion.

MAIN OUTCOME MEASURE(S)

The Brief Symptom Inventory-18, Hospital Anxiety and Depression Scale, and Satisfaction With Life Scale (SWLS) measures were completed at baseline (preseason) and on the day participants were cleared for unrestricted return to play (RTP) after a concussion. Two binary logistic regressions were used to predict postconcussion LE MSK within a year, one for the baseline time point and the second for the RTP time point. A 2 (group: LE MSK, no LE MSK)-by-2 (time: baseline, RTP) repeated-measures analysis of variance compared performance between baseline and RTP.

RESULTS

Subsequent LE MSKs were sustained by 44 participants (65.7%). The only significant predictor of postconcussion LE MSK was the SWLS score at RTP, with Exp(B) = 0.64, indicating that an increased (improved) SWLS score was associated with a lower LE MSK rate. No significant interactions were present between mental health measures and subsequent MSK (P values = .105-.885).

CONCLUSIONS

Limited associations were evident between postconcussion LE MSK and scores on commonly used measures of anxiety, depression, and satisfaction with life. Reported increased satisfaction with life was associated with a decreased injury risk, which warrants further attention. Our results suggest that these measures of anxiety, depression, and satisfaction with life have limited value in assisting sports medicine clinicians with determining which student-athletes are at elevated risk of postconcussion LE MSK.

Autonomic dysfunction and exercise intolerance in concussion: a scoping review

PURPOSE

Concussion commonly results in exercise intolerance, often limiting return to activities. Improved understanding of the underlying mechanisms of post-concussive exercise intolerance could help guide mechanism-directed rehabilitation approaches. Signs of altered cardiovascular autonomic regulation-a potential contributor to exercise intolerance-have been reported following concussion, although it is not clear how these findings inform underlying mechanisms of post-concussive symptoms. Systematic summarization and synthesis of prior work is needed to best understand current evidence, allowing identification of common themes and gaps requiring further study. The purpose of this review was to (1) summarize published data linking exercise intolerance to autonomic dysfunction, and (2) summarize key findings, highlighting opportunities for future investigation.

METHODS

The protocol was developed a priori, and conducted in five stages; results were collated, summarized, and reported according to PRISMA guidelines. Studies including injuries classified as mild traumatic brain injury (mTBI)/concussion, regardless of mechanism of injury, were included. Studies were required to include both autonomic and exercise intolerance testing. Exclusion criteria included confounding central or peripheral nervous system dysfunction beyond those stemming from the concussion, animal model studies, and case reports.

RESULTS

A total of 3116 publications were screened; 17 were included in the final review.

CONCLUSION

There was wide variability in approach to autonomic/exercise tolerance testing, as well as inclusion criteria/testing timelines, which limited comparisons across studies. The reviewed studies support current clinical suspicion of autonomic dysfunction as an important component of exercise intolerance. However, the specific mechanisms of impairment and relationship to symptoms and recovery require additional investigation.

Evolving the SCAT5 for Ruling Out Higher-Severity Traumatic Brain Injuries-Can Decision Rules Developed for Emergency Settings Help?

BACKGROUND: Decision rules (eg, Canadian computed tomography head rule [CCHR] for adults and Pediatric Emergency Care Applied Research Network [PECARN] rule for children/adolescents) are used in emergency settings (emergency room [ER] rules) to assess traumatic brain injuries (TBIs). The rules have a high-sensitivity and near-perfect negative predictive value that help to rule out more severe TBI. CLINICAL QUESTION: Which criteria should be added to the Sport Concussion Assessment Tool 5 (SCAT5) to reach the sensitivity of the ER rules and improve the utility of the SCAT5 for screening for higher-severity head and brain injuries? KEY RESULTS: We performed a comparative analysis of the SCAT5 with the CCHR and PECARN rules. We compared the presence (yes or no) and comparative "face value" sensitivity (lower, identical, or higher) of the SCAT5 criteria to the ER rules criteria. Loss of consciousness, vomiting, severe/increasing headache, and seizure are SCAT "red flags" with similar or higher sensitivity compared to ER rules criteria. Five criteria had lower sensitivity or were absent from the SCAT. Emergency room rules include any abnormality on the Glasgow Coma Scale (GCS<15), but only a "deterioration of the state of consciousness" is considered a "red flag" in the SCAT5. Persistent retrograde amnesia for more than 30 minutes, age>65, severity of the mechanism of injury, and signs of skull fractures are not mentioned in the SCAT5. CLINICAL APPLICATION: We identified 5 criteria that could inform the evolution the SCAT5 to improve its ability to rule out more severe TBI in a sideline assessment context. J Orthop Sports Phys Ther 2023;53(3):113-119. Epub: 9 December 2022. doi:10.2519/jospt.2022.11301.

Lower Extremity Musculoskeletal Injuries After Concussion in Collegiate Student-Athletes

BACKGROUND

An association has been identified between concussion and lower extremity musculoskeletal injury (LEMSKI) after return to sports participation. However, the collegiate student-athlete studies have relied on relatively small single-institution studies, which limits generalizability.

PURPOSE

To assess odds of, and time to, LEMSKI after concussion in US collegiate athletes, using the National Collegiate Athletic Association (NCAA) Injury Surveillance Program (ISP).

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Data from the NCAA ISP during the 2010-2011 through 2019-2020 athletic seasons were considered for analysis. Frequency distributions were examined for details related to the initial and subsequent injuries (injuries to bone, bursa, joint, ligament, muscle, or tendon). Multivariable logistic regression models and random-effects Poisson regression models examined odds of time loss (TL) and non-time loss (NTL) LEMSKI after concussion, as well as the time interval between initial concussion and subsequent LEMSKI in a single athletic season, or initial musculoskeletal injury (MSKI) and subsequent LEMSKI in a single athletic season. Analyses were performed separately for football and other sports.

RESULTS

A total of 31,556 initial injuries were recorded (football: 11,900; other sports: 19,656), which were followed by 0 or 1 injury in the same season. Overall, first injury type was not a significant predictor of subsequent LEMSKI, although certain contrasts yielded significant estimates. In football, the odds of NTL LEMSKI were higher after concussion than after upper extremity MSKI (UEMSKI; adjusted odds ratio [OR_Adj], 1.56; 95% CI, 1.06-2.31). In football, the odds of TL LEMSKI were lower after concussion than after UEMSKI (OR_Adj, 0.71; 95% CI, 0.51-0.99). No other significant effect estimates were observed for football or other sports.

CONCLUSION

First injury type, either concussion or upper extremity, was not associated with an elevated risk of LEMSKI. Specifically, the results of this study did not identify an elevated odds of LEMSKI after a concussion. However, the authors observed greater odds of NTL LEMSKI and lower odds of TL LEMSKI in football.

Changes in the cardiac autonomic control system during rehabilitation in children after severe traumatic brain injury

BACKGROUND

One of the sequalae of severe traumatic brain injury (TBI) in children is impaired function of the cardiac autonomic control system (CACS) at rest. The CACS response to conventional autonomic tests is little known.

OBJECTIVE

To examine the CACS response to conventional autonomic tests in children after severe TBI during the rehabilitation period and to compare with typically developing (TD) children.

METHODS

This study combined a case-control and follow-up design. The severe TBI group (cases) consisted of 33 children aged 9-18 years, 14-142 days after severe TBI who were followed for 8 weeks during rehabilitation. The control group consisted of 19 TD children matched for age and sex. Heart rate (HR) and heart rate variability (HRV) were evaluated with the Polar RS800CX device at rest (sitting), during a handgrip test and during a paced breathing test.

RESULTS

At the first assessment, we found lower HRV values at rest and a lower HRV response during the paced breathing and handgrip tests in the TBI group than the TD group (p<0.01). After 8 weeks, HRV values did not change at rest in the TBI group, but the response to the autonomic tests improved significantly, with increased HRV values in response to the paced breathing test (p<0.01) and the handgrip test (p = 0.01).

CONCLUSIONS

After severe TBI, children exhibited an impaired CACS response to autonomic tests, with parasympathetic suppression and sympathetic arousal. After 8 weeks of rehabilitation, CACS function recovered partially and the response to the autonomic tests improved with no change in CACS function at rest.

Headache and Autonomic Dysfunction: a Review

PURPOSE OF REVIEW

We explore the anatomy of the central and peripheral autonomic pathways involved in primary headache as well as the mechanisms for secondary headache associated with disorders of the autonomic nervous system. The prevalence and clinical presentation of cranial and systemic autonomic symptoms in these conditions will be discussed, with a focus on recent studies.

RECENT FINDINGS

Several small studies have utilized the relationship between headache and the autonomic nervous system to identify potential biomarkers to aid in diagnosis of migraine and cluster headache. Headache in postural orthostatic tachycardia syndrome (POTS) has also been further characterized, particularly in its association with orthostatic headache and spontaneous intracranial hypotension (SIH). This review examines the pathophysiology of primary and secondary headache disorders in the context of the autonomic nervous system. Mechanisms of headache associated with systemic autonomic disorders are also reviewed.

Concussion is not associated with elevated rates of lower-extremity musculoskeletal injuries in National Football League Players

OBJECTIVE

Emerging evidence has identified an ~2x elevated risk of musculoskeletal (MSK) injury in the year following a concussion. Most of these studies have examined a single college/university athletic department and may lack generalizability to professional sports. Therefore, the purpose of this study was to assess the odds of post-concussion MSK injury utilizing publicly available National Football League (NFL) injury reports.

METHODS

Concussions were identified through a review of published NFL injury reports during the 2015, 2016, and 2017 regular seasons. Concussed players were matched by team and position, and injuries were tracked for both groups for the remainder of the season. A chi-square analysis compared the frequency of MSK injury in both groups and a Cox Proportional Hazard model calculated the risk of sustaining a subsequent MSK injury.

RESULTS

There were 322 concussed NFL players who met inclusion criteria and were successfully matched. From the time of concussion through the remainder of the season, 21.4% of the concussed players were injured and 26.4% of control participants were injured. There was no difference in MSK injury rates (p = 0.166), and the relative risk ratio was 0.90 for subsequent injury in the concussion group. There was no difference in the time to event for subsequent MSK between the two groups (p = 0.123).

CONCLUSION

The primary finding of this study was no elevated risk of post-concussion MSK in NFL football players.

Autonomic dysfunction in adults following mild traumatic brain injury: A systematic review

BACKGROUND

Increasing evidence suggests autonomic nervous system (ANS) dysfunction may occur following mild traumatic brain injury (mTBI). Measures of heart rate, heart rate variability, blood pressure and baroreceptor sensitivity can be used to evaluate ANS dysfunction following mTBI.

OBJECTIVE

Summarize the evidence for ANS dysfunction in adults following mTBI.

METHODS

A search of Embase, MEDLINE, Cochrane Central Register, PsycINFO, CINAHL and SPORTDiscus databases was conducted. Search topics included: mTBI and ANS. Identified abstracts were independently reviewed by 2 reviewers followed by full text screening. Risk of bias was assessed using a modified SIGN checklist. A structured synthesis was performed.

RESULTS

Thirty-nine studies (combined 1,467 participants diagnosed with mTBI) evaluating ANS function were included. ANS function was evaluated under various conditions including: rest, during exertion, cold pressor test, Valsalva maneuver, using face cooling and eyeball pressure paradigms. Short-term or ultra-short-term recordings were most common. The majority of studies (28/39) were rated as "unacceptable" for quality of evidence.

CONCLUSIONS

Altered parameters of ANS function have been reported in multiple conditions following mTBI, both acutely and in the post-acute/chronic stages of recovery. However, due to methodological limitations, conclusions regarding the severity and timing of ANS dysfunction following mTBI cannot be drawn.

Acute Physical and Mental Activity Influence on Concussion Recovery

INTRODUCTION

Physical activity (PA) and mental activity (MA) postconcussion has received renewed attention to improve concussion management; however, most protocols start after several days and do not assess the acute window. Therefore, the purpose of this study was to assess PA and MA in the first 48 h postconcussion on the time to symptom-free status and return to play.

METHODS

We recruited 78 NCAA Division I athletes (male, 51.3%; age, 19.6 ± 1.4 yr; height, 173.7 ± 11.5 cm; weight, 80.1 ± 23.2 kg) who were diagnosed with a sports-related concussion. Participants completed a 0-5 PA and MA scale daily until fully cleared for return to participation (mean, 15.1 ± 6.9 d). A quadratic model regression assessed PA and MA over the first 2 d (acute) postconcussion on to time to symptom-free status and return to play.

RESULTS

The overall model was significant for both time to symptom free (r2 = 0.27, P = 0.004) and return to play (r2 = 0.23, P = 0.019). Reported PA was the only significant predictor for time to symptom-free (P = 0.002) and return-to-participation (P = 0.006) day. Reported MA was not associated either outcome.

CONCLUSIONS

The primary finding of this study was that mild to moderate PA acutely postconcussion was associated with reduced time to symptom free and return to participation as opposed to either lower or higher levels of PA. Conversely, acute MA was not associated with recovery outcomes. These results further elucidate the role of postconcussion PA.

Persistent CO2 reactivity deficits are associated with neurological dysfunction up to one year after repetitive mild closed head injury in adolescent mice

Cerebrovascular reactivity (CVR) deficits in adolescents with concussion may persist after resolution of neurological symptoms. Whether or not CVR deficits predict long term neurological function is unknown. We used adolescent mice closed head injury (CHI) models (54 g, 107 cm or 117 cm drop height), followed by blood oxygenation level dependent (BOLD)-functional MRI with CO₂ challenge to assess CVR and brain connectivity. At one week, 3HD 107 cm mice showed delayed BOLD responses (p = 0.0074), normal striatal connectivity_, and an impaired respiratory rate response to CO₂ challenge (p = 0.0061 in ΔRmax). The 107 cm group developed rotarod deficits at 6 months (p = 0.02) and altered post-CO₂ brain connectivity (3-fold increase in striatum to motor cortex correlation coefficient) by one year, but resolved their CVR and respiratory rate impairments, and did not develop cognitive or circadian activity deficits. In contrast, the 117 cm group had persistent CVR (delay time: p = 0.016; washout time: p = 0.039) and circadian activity deficits (free-running period: 23.7 hr in sham vs 23.9 hr in 3HD; amplitude: 0.15 in sham vs 0.2 in 3HD; peak activity: 18 in sham vs 21 in 3HD) at one year. Persistent CVR deficits after concussion may portend long-term neurological dysfunction. Further studies are warranted to determine the utility of CVR to predict chronic neurological outcome after mild traumatic brain injury.

Insufficient sampling frequencies skew heart rate variability estimates: Implications for extracting heart rate metrics from neuroimaging and physiological data

BACKGROUND

While cardiac pulsations are widely present within physiological and neuroimaging data, it is unknown the extent this information can provide valid and reliable heart rate and heart rate variability (HRV) estimates. The objective of this study was to demonstrate how a slight temporal shift due to an insufficient sampling frequency can impact the validity/accuracy of deriving cardiac metrics.

METHODS

Twenty-two participants were instrumented with valid/reliable industry-standard or open-source electrocardiograms. Five-minute lead II recordings were collected at 1000 Hz in an upright orthostatic position. Following artifact removal, the 1000 Hz recording for each participant was downsampled to frequencies ranging 2-500 Hz. The validity of each participant's downsampled recording was compared against their 1000 Hz recording ("reference-standard") using Bland-Altman plots with 95 % limits of agreement (LOA), coefficient of variation (CoV), intraclass correlation coefficients, and adjusted r-squared values.

RESULTS

Downsampled frequencies of ≥ 50 and ≥ 90 Hz produced highly robust measures with narrow log-transformed 95 % LOA (<±0.01) and low CoV values (≤3.5 %) for heart rate and HRV metrics, respectively. Below these thresholds, the log-transformed 95 % LOA became wider (LOA range: ±0.1-1.9) and more variable (CoV range: 1.5-111.6 %).

CONCLUSION

These results provide an important consideration for obtaining cardiac information from physiological data. Compared to the "reference-standard" ECG, a seemingly negligible temporal shift of the systolic contraction (R wave) greater than 11-milliseconds (90 Hz) away from its true value, lessened the validity of the HRV. Further research is warranted to determine the minimum sampling frequency required to obtain valid heart rate/HRV metrics from pulsatile waveforms.

Use of Mayer wave activity to demonstrate aberrant cardiovascular autonomic control following sports concussion injury

Dysregulation of cardiovascular autonomic control is gaining recognition as a prevailing consequence of concussion injury. Characterizing the presence of autonomic dysfunction in concussed persons is inconsistent and conventional metrics of autonomic function cannot differentiate the presence/absence of injury. Mayer wave (MW) activity originates through baroreflex adjustments to blood pressure (BP) oscillations that appear in the low‐frequency (LF: 0.04–0.15 Hz) band of the BP and heart rate (HR) power spectrum after a fast Fourier transform. We prospectively explored MW activity (∼0.1 Hz) in 19 concussed and 19 noninjured athletes for 5 min while seated at rest within 48 h and 1 week of injury. MW activity was derived from the LF band of continuous digital electrocardiogram and beat‐to‐beat BP signals (LFHR, LF‐SBP, MWHR, and MW‐SBP, respectively); a proportion between MWBP and MWHR was computed (cMW). At 48 h, the concussion group had a significantly lower MWBP and cMW than controls; these differences were gone by 1 week. MWHR, LFHR, and LF‐SBP were not different between groups at either visit. Attenuated sympathetic vasomotor tone was present and the central autonomic mechanisms regulating MW activity to the heart and peripheral vasculature became transiently discordant early after concussion with apparent resolution by 1 week.

Beyond the Brain: Peripheral Interactions after Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of death and disability, and there are currently no pharmacological treatments known to improve patient outcomes. Unquestionably, contributing toward a lack of effective treatments is the highly complex and heterogenous nature of TBI. In this review, we highlight the recent surge of research that has demonstrated various central interactions with the periphery as a potential major contributor toward this heterogeneity and, in particular, the breadth of research from Australia. We describe the growing evidence of how extracranial factors, such as polytrauma and infection, can significantly alter TBI neuropathology. In addition, we highlight how dysregulation of the autonomic nervous system and the systemic inflammatory response induced by TBI can have profound pathophysiological effects on peripheral organs, such as the heart, lung, gastrointestinal tract, liver, kidney, spleen, and bone. Collectively, this review firmly establishes TBI as a systemic condition. Further, the central and peripheral interactions that can occur after TBI must be further explored and accounted for in the ongoing search for effective treatments.

Review of wearable technologies and machine learning methodologies for systematic detection of mild traumatic brain injuries

Mild traumatic brain injuries (mTBIs) are the most common type of brain injury. Timely diagnosis of mTBI is crucial in making 'go/no-go' decision in order to prevent repeated injury, avoid strenuous activities which may prolong recovery, and assure capabilities of high-level performance of the subject. If undiagnosed, mTBI may lead to various short- and long-term abnormalities, which include, but are not limited to impaired cognitive function, fatigue, depression, irritability, and headaches. Existing screening and diagnostic tools to detect acute andearly-stagemTBIs have insufficient sensitivity and specificity. This results in uncertainty in clinical decision-making regarding diagnosis and returning to activity or requiring further medical treatment. Therefore, it is important to identify relevant physiological biomarkers that can be integrated into a mutually complementary set and provide a combination of data modalities for improved on-site diagnostic sensitivity of mTBI. In recent years, the processing power, signal fidelity, and the number of recording channels and modalities of wearable healthcare devices have improved tremendously and generated an enormous amount of data. During the same period, there have been incredible advances in machine learning tools and data processing methodologies. These achievements are enabling clinicians and engineers to develop and implement multiparametric high-precision diagnostic tools for mTBI. In this review, we first assess clinical challenges in the diagnosis of acute mTBI, and then consider recording modalities and hardware implementation of various sensing technologies used to assess physiological biomarkers that may be related to mTBI. Finally, we discuss the state of the art in machine learning-based detection of mTBI and consider how a more diverse list of quantitative physiological biomarker features may improve current data-driven approaches in providing mTBI patients timely diagnosis and treatment.

Cardiovascular Sequalae of Sports-Related Concussions

We are becoming more aware of sports-related concussions (SRCs). Current return-to-play (RTP) guidelines are often based on subjective clinical symptoms rather than objective physiologic measures. Although evidence is limited, the purpose of this manuscript is to summarize the data pertaining to acute and chronic cardiovascular effects of SRCs, and to determine whether there are objective metrics that could improve currently used RTP protocols. Research shows that SRCs cause cardiovascular autonomic nervous system (CV-ANS) dysfunction induced by decreased baroreceptor sensitivity (BRS). This disturbance persists past the point of clinical symptom resolution and can worsen through subsequent exertion, which may impact long-term recovery. Further studies are needed to establish the most appropriate physiologic metrics for analyzing recovery post-SRC and whether the addition of physiologic measures to RTP guidelines improves recovery from these injuries. This is an understudied area that carries important clinical implications. Larger and more robust trials are warranted to inform the development of guidelines that should focus on lessening the compounding effects of multiple concussions and improve the management of SRCs. This article is protected by copyright. All rights reserved.

Clinical Evaluation and Treatment of Patients with Postconcussion Syndrome

Postconcussion syndrome (PCS) is a complex set of symptoms occurring in a small percentage of patients following concussion. The condition is characterized by headaches, dizziness, cognitive difficulties, somatosensory issues, and a variety of other symptoms with varying durations. There is a lack of objective markers and standard treatment protocols. With the complexity created by premorbid conditions, psychosomatic issues, secondary gains, and litigations, providers often find themselves in a tough situation in the care of these patients. This article combines literature review and clinical insights with a focus on the underlying pathophysiology of PCS to provide a roadmap for evaluating and treating this condition.

The Influence of Family History of Neurodegenerative Disease on Adolescent Concussion Outcomes

Evidence suggests that factors associated with a family history of neurodegenerative disease (fhNDD) may influence outcomes following a concussion. However, the relevance of these findings in adolescent populations has not been fully explored. Therefore, the present study sought to evaluate the relationship between fhNDD and neurological outcomes following an adolescent concussion. Data from a local pediatric concussion clinic were used to compare adolescents with (n = 22) and without (n = 44) an fhNDD. Clinical symptom burden, emotional health, cardio-autonomic function, and cognitive performance were assessed at initial (~2 weeks) and follow-up (~5 weeks) post-injury evaluations. Cardio-autonomic function was assessed at rest and during isometric handgrip contraction (IHGC). Results indicated no significant group differences in emotional health or cognitive performance. Across evaluations, those with an fhNDD exhibited greater somatic symptom severity, alterations in HRV at rest, and early blunted cardio-autonomic reactivity during IHGC compared to those without an fhNDD. These findings suggest that positive fhNDD is negatively associated with clinical symptomology and cardio-autonomic functioning following an adolescent concussion. Further, these findings encourage clinicians to utilize a comprehensive neurological evaluation to monitor concussion recovery. Future studies should look into exploring the role of specific neurodegenerative processes and conditions on concussion outcomes in adolescents.

No Clinical Predictors of Postconcussion Musculoskeletal Injury in College Athletes

PURPOSE

This study aimed to identify clinical predictors of postconcussion subsequent musculoskeletal (MSK) injuries.

METHODS

We recruited 66 National Collegiate Athletic Association intercollegiate student-athletes with a diagnosed concussion as well as 36 National Collegiate Athletic Association student-athletes without a concussion. All participants completed a multifaceted concussion baseline consisting of 1) 22-item 0-6 self-reported symptom checklist with outcomes including both the number of symptoms endorsed (0-22) and 2) total symptom score (0-132), 3) Standard Assessment of Concussion, 4) Balance Error Scoring System, 5) Immediate Post-Concussion Assessment and Cognitive Testing, 6) clinical reaction time, and 7) the King-Devick as well as demographic and injury characteristics. The concussion participants completed the same examination acutely postconcussion, and binary logistic regression was used to identify predictors of subsequent MSK from the change scores (acute minus baseline). From the 66 concussed student-athletes, a subset 36, matched with the healthy athletes, compared the risk of subsequent MSK in the year before and year after their concussion.

RESULTS

The concussion participants were 1.78 times (95% confidence interval, 1.12-2.84; P = 0.015) more likely to suffer a lower extremity MSK in the year after their concussion than the control participants. The participant demographics and injury characteristics (P = 0.318) and concussion clinical outcomes (P = 0.461) did not predict subsequent MSK.

CONCLUSION

The concussion participants were 1.78 times more likely to sustain a subsequent MSK; however, no demographic, injury characteristic, or concussion assessments predicted the MSK. Thus, clinicians are not able to utilize common neurological measures or participant demographics to identify those at risk for subsequent lower extremity MSK. Injury prevention strategies should be considered for collegiate student-athletes upon premature return to participation after a concussion to reduce the subsequent MSK.

Impairments in Dynamic Postural Control across Concussion Clinical Milestones

The aim of this study was to assess gait initiation (GI) performance longitudinally across clinical concussion recovery milestones through return to participation (RTP). We recruited 54 collegiate student-athletes, 27 with concussions and 27 matched controls (15 female and 12 male per group). Participants performed five trials of GI at baseline and again at five post-concussion clinical milestones: 1) Acute, the day clinical tests achieved baseline values on the 2) Balance Error Scoring System (BESS), 3) Immediate Post-Concussion Assessment and Cognitive Test ImPACT, 4) Asymptomatic, and 5) RTP Day. GI performance on six outcome measures (anterior/posterior and medial/lateral center of pressure displacements and velocities during the anticipatory postural adjustment [APA] phase and initial step length and velocity) with repeated-measures mixed model and pair-wise post hoc. A reliable change index (RCI) was calculated, and post-concussion participant's performance was compared to the RCI at milestones. There were significant interactions for APA posterior and lateral displacement, APA posterior velocity, step length, and step velocity. The post-hoc tests identified significant deficits across clinical milestones and at RTP for APA posterior and lateral displacement, step length, and step velocity. There were no post-hoc differences for any outcome measure in the control group. At RTP, 85.2-88.9% of concussion participants had at least one outcome measure which exceeded the 80% or 95% RCI. The primary finding of this study was persistent impairments in dynamic postural control, suggesting ongoing neurophysiological impairment despite clinical recovery. These results suggest that collegiate student-athletes may be RTP before neurophysiological recovery and potentially exposing themselves to elevated risk of recurrent concussion or subsequent musculoskeletal injury.

Early Aerobic Exercise for the Treatment of Acute Pediatric Concussions

Sport-related concussion is a common injury that has garnered the attention of the media and general public because of the potential for prolonged acute symptoms and increased risk for long-term impairment. Currently, a growing body of evidence supports the use of various therapies to improve recovery after a concussion. A contemporary approach to managing concussion symptoms is to use aerobic exercise as treatment. To date, several studies on both pediatric and adult patients have established that controlled aerobic exercise is a safe and effective way to rehabilitate patients experiencing delayed recovery after concussion. However, less is known about the utility of an early exercise protocol for optimizing recovery after acute concussion and reducing the risk for persistent postconcussive symptoms, particularly in pediatric populations. Thus, the purpose of our paper was to review and evaluate the available literature on the implementation of aerobic exercise for the treatment of acute pediatric concussion.

Causal Link between Ventricular Ectopy and Concussion

We present a unique case study report of a male individual with a history of mild nonischaemic cardiomyopathy, with no ventricular ectopy, that at the age of 76 years sustained multiple concussions (i.e., mild traumatic brain injury) within a week of each other. Concussion symptoms included cognitive difficulties, "not feeling well," lethargy, fatigue, and signs of depression. He was later medically diagnosed with postconcussion syndrome. The patient, WJT, was referred for cardiac and neurological assessment. Structural neuroimaging of the brain (MRI) was unremarkable, but electrocardiography (ECG) assessments using a 24-hour Holter monitor revealed significant incidence of ventricular ectopy (9.4%; 9,350/99,836 beats) over a period of 5-6 months after injury and then a further increase in ventricular ectopy to 18% (15,968/88,189 beats) during the subsequent 3 months. The patient was then prescribed Amiodarone 200 mg, and his ventricular ectopy and concussion symptoms completely resolved simultaneously within days. To the authors' knowledge, our study is the first to show a direct link between observable and documented cardiac dysregulation and concussion symptomology. Our study has important implications for both cardiac patients and the patients that sustain a concussion, and if medically managed with appropriate pharmacological intervention, it can reverse ventricular ectopy and concussion symptomology. More research is warranted to investigate the mechanisms for this dramatic and remarkable change in cardiac and cerebral functions and to further explore the brain-heart interaction and the intricate autonomic interaction that exists between the extrinsic and intracardiac nervous systems.

Assessing the Quality of Heart Rate Variability Estimated from Wrist and Finger PPG: A Novel Approach Based on Cross-Mapping Method

The non-invasiveness of photoplethysmographic (PPG) acquisition systems, together with their cost-effectiveness and easiness of connection with IoT technologies, is opening up to the possibility of their widespread use. For this reason, the study of the reliability of PPG and pulse rate variability (PRV) signal quality has become of great scientific, technological, and commercial interest. In this field, sensor location has been demonstrated to play a crucial role. The goal of this study was to investigate PPG and PRV signal quality acquired from two body locations: finger and wrist. We simultaneously acquired the PPG and electrocardiographic (ECG) signals from sixteen healthy subjects (aged 28.5 ± 3.5, seven females) who followed an experimental protocol of affective stimulation through visual stimuli. Statistical tests demonstrated that PPG signals acquired from the wrist and the finger presented different signal quality indexes (kurtosis and Shannon entropy), with higher values for the wrist-PPG. Then we propose to apply the cross-mapping (CM) approach as a new method to quantify the PRV signal quality. We found that the performance achieved using the two sites was significantly different in all the experimental sessions (p < 0.01), and the PRV dynamics acquired from the finger were the most similar to heart rate variability (HRV) dynamics.

Differential Effects of Acute and Multiple Concussions on Gait Initiation Performance

OBJECTIVE

To identify the effect of acute and multiple concussions on gait initiation performance.

DESIGN

Cohort study.

SETTING

University research center.

PARTICIPANTS

A population-based sample of participants (N=45) divided into 3 groups: No Prior Concussion, ≥3 Prior Concussions, and Acute Concussion. The Acute Concussion participants were assessed within 24 hours of their concussion. Participants were matched based on (1) sport, (2) position, and (3) anthropometric measures.

INTERVENTIONS

Participants were tested on a single occasion and performed 5 trials of gait initiation on 4 force plates. The No Prior Concussion and ≥3 Prior Concussions groups were tested out of their primary athletic season.

MAIN OUTCOME MEASURES

The dependent variables were the posterior and lateral displacement and velocity of the center of pressure (COP) during the anticipatory postural adjustment phase and initial step kinematics (step length and step velocity). Comparisons between groups used a 1-way analysis of variance with Tukey post hoc when significant effects were identified and effect sizes were calculated.

RESULTS

There were significant effects for group for all 6 outcome measures with large effect sizes. Post hoc tests identified differences between Acute Concussion and No Prior Concussion groups for all measures. The ≥3 Prior Concussions group and No Prior Concussion group were different for COP posterior displacement (4.91±1.09 and 4.91±1.09cm, respectively, P=.032, d=0.91) and velocity (0.18±0.06 and 0.27±0.08m/s, respectively, P=.002, d=1.27).

CONCLUSION

There was continuum of performance identified whereby the Acute Concussion participants performed worse and the No Prior Concussion participants performed the best. The ≥3 Prior Concussions generally fell between these 2 groups, but only statistical significance on COP posterior displacement and velocity. These results suggest there may be subtle neurophysiological deficits present in collegiate student-athletes with ≥3 Prior Concussions group, and further investigation over the lifespan is warranted.

Attenuated Cardiovascular Responses to the Cold Pressor Test in Concussed Collegiate Athletes

CONTEXT

Cardiovascular responses to the cold pressor test (CPT) provide information regarding sympathetic function.

OBJECTIVE

To determine if recently concussed collegiate athletes had blunted cardiovascular responses during the CPT.

DESIGN

Cross-sectional study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 10 symptomatic concussed collegiate athletes (5 men, 5 women; age = 20 ± 2 years) who were within 7 days of diagnosis and 10 healthy control individuals (5 men, 5 women; age = 24 ± 4 years).

INTERVENTION(S)

The participants' right hands were submerged in agitated ice water for 120 seconds (CPT).

MAIN OUTCOME MEASURE(S)

Heart rate and blood pressure were continuously measured and averaged at baseline and every 30 seconds during the CPT.

RESULTS

Baseline heart rate and mean arterial pressure were not different between groups. Heart rate increased throughout 90 seconds of the CPT (peak increase at 60 seconds = 16 ± 13 beats/min; P < .001) in healthy control participants but remained unchanged in concussed athletes (peak increase at 60 seconds = 7 ± 10 beats/min; P = .08). We observed no differences between groups for the heart rate response (P > .28). Mean arterial pressure was elevated throughout the CPT starting at 30 seconds (5 ± 7 mm Hg; P = .048) in healthy control individuals (peak increase at 120 seconds = 26 ± 9 mm Hg; P < .001). Mean arterial pressure increased in concussed athletes at 90 seconds (8 ± 8 mm Hg; P = .003) and 120 seconds (12 ± 8 mm Hg; P < .001). Healthy control participants had a greater increase in mean arterial pressure starting at 60 seconds (P < .001) and throughout the CPT than concussed athletes (peak difference at 90 seconds = 25 ± 10 mm Hg and 8 ± 8 mm Hg, respectively; P < .001).

CONCLUSIONS

Recently concussed athletes had blunted cardiovascular responses to the CPT, which indicated sympathetic dysfunction.

Attenuation of Spontaneous Baroreceptor Sensitivity after Concussion

INTRODUCTION

Cardiovascular autonomic nervous system (CV-ANS) function is negatively impacted after concussion. The arterial baroreflex buffers pressor and depressor challenges through efferent modulation of cardiac chronotropism and inotropism, and peripheral vascular tone. Baroreceptor sensitivity (BRS) reflects the capacity of the CV-ANS to accommodate dynamic metabolic demands in the periphery. The impact of concussion on BRS has yet to be defined.

METHODS

Cardiovascular autonomic nervous system assessment (e.g., electrocardiogram and beat-to-beat systolic blood pressure [SBP]) was performed the seated upright position at rest within 48 h (V1) of concussion and 1 wk later (V2) in 10 intercollegiate male athletes with concussion and 10 noninjured male athletes. Changes in HR, SBP, high- and low-frequency HR variabilities (HF-HRV and LF-HRV, respectively), LF-SBP variability and BRS for increasing (BRSn-Up) and decreasing (BRSn-Dn) SBP excursions, and overall BRS (BRSn-Avg) were assessed for differences at V1 and V2.

RESULTS

The concussion (age, 20 ± 1 yr; height, 1.79 ± 0.14 m; weight, 83 ± 10 kg) and control (age, 20 ± 1 yr; height, 1.78 ± 0.10 m; weight, 79 ± 13 kg) groups were matched for demographics. Concussed athletes had a significantly reduced BRSn-Up, BRSn-Dn, and BRSn-Avg compared with controls at V1 or V2; these changes occurred without differences in conventional markers of CV-ANS function (e.g., HF-HRV, LF-HRV, LF-SBP), HR, or SBP at either visit.

CONCLUSIONS

Reduced BRS is a postconcussive consequence of CV-ANS dysfunction during the first postinjury week. Because SBP was similar between groups, it may be speculated that reduced BRS was not afferent in origin, but represents a postinjury consequence of the central nervous system after injury.

Pediatric Traumatic Brain Injury and Exercise Medicine: A Narrative Review

The multidisciplinary field of pediatric traumatic brain injury (TBI) and exercise medicine is of growing importance. There is active study into the diagnostic and therapeutic potential of exercise in pediatric TBI as well as the effects of TBI on postinjury fitness. With the evidence-based growing, a literature review can help establish the state of the science and inform future research. Therefore, the authors performed a narrative review (based on a search of 6 health sciences databases) to summarize evidence on pediatric TBI and cardiorespiratory fitness, muscular fitness and neuromotor control, and obesity. To date, studies related to cardiorespiratory fitness have centered on exercise tolerance and readiness to return to play, and indicate that protracted rest may not facilitate symptom recovery; this suggests a role for exercise in concussion management. Furthermore, strength and gait may be impaired following pediatric brain injury, and interventions designed to train these impairments may lead to their improvement. Pediatric brain injury can also lead to changes in body composition (which may be related to poorer cognitive recovery), but additional research is required to better understand such associations. This narrative review of pediatric TBI and exercise medicine can serve as a reference for researchers and clinicians alike.

Considerations for Diagnosis and Management of Concussion

Concussion is an ongoing concern for health care providers. The incidence rates continue to be high and the rate of recovery is variable due to potential risk factors. With no valid biomarkers, diagnosis and assessment of concussion remain a clinical challenge. The heterogeneity in presentation following injury provides an additional level of complexity, requiring the screening and evaluation of diverse body systems, including oculomotor, vestibular, autonomic, psychiatric, cervical, and cognitive symptoms. While a few tools, such as the Vestibular/Ocular Motor Screening and Balance Error Scoring System, have been developed specifically for concussion, the vast majority of tests are adapted from other conditions. Further complicating the process is the overlapping and interactive nature of the multiple domains of postconcussion presentation. This commentary illustrates how clinicians can conceptualize the multiple profiles that present following concussion and describes tools that are available to assist with screening and evaluation of each area. The multifaceted nature of concussion warrants broad clinical screening skills and an interdisciplinary approach to management. J Orthop Sports Phys Ther 2019;49(11):787-798. doi:10.2519/jospt.2019.8855.

Adapting the Dynamic, Recursive Model of Sport Injury to Concussion: An Individualized Approach to Concussion Prevention, Detection, Assessment, and Treatment

The risk factors of concussion may be categorized as intrinsic (internal factors specific to the individual) or extrinsic (external factors related to the environment or sport). Identifying these factors is part of an individualized, patient-centered approach to prevention, assessment, and management of concussion. In most cases, the symptoms of concussion resolve in the initial few days following the injury, and a strategy involving a gradual return to sport and school is recommended. When symptoms persist for longer than 7 to 10 days, a multifaceted interdisciplinary assessment to guide treatment is recommended. This article applies the dynamic, recursive model of sport injury to sport-related concussion and summarizes the process of individualized assessment and management following concussion in athletes of all ages, with a focus on physical rehabilitation. J Orthop Sports Phys Ther 2019;49(11):799-810. doi:10.2519/jospt.2019.8926.

Multiannual, Intensive Strength-Endurance Training Modulates the Activity of the Cardiovascular and Autonomic Nervous System among Rowers of the International Level

Introduction

Professional athlete training is significantly different from recreational physical activity, and sustained, repetitive exposure to over-strenuous and intensive training may result in critical changes of most systems and organs in a sportsman's body.

Aim

The assessment of the influence of multiannual strength-endurance training on the autonomic nervous system (ANS) and cardiovascular system (CVS) among the rowers of Polish national team.

Materials and Methods

20 rowers, aged 20–30, seniors of Polish national team were qualified into the study. The functional examination of ANS was conducted by means of Task Force® Monitor system. The assessed parameters included hemodynamic parameters, heart rate, and blood pressure variability and reflexes sensitivity of baroreceptors. In order to examine and compare the reaction of autonomic nervous system the subjects underwent a tilt test.

Results

In the study group, significantly higher levels of sBP (129.3  ±  12.2 vs 118.3 ± 8.4, p = 0.0030), SI (59.9 ± 8.8 vs 41.2 ± 6.8, p > 0.001), CI (3.2 ± 0.5 vs 2.4 ± 0.4, p > 0.001), and significantly lower levels of HR (54.2 ± 5.3 vs 60.1 ± 5.7, p = 0.0034) and TPRI (2333.3 ± 389.9 vs 2950.2 ± 604.2, p = 0.0012) compared to the control group, were found. After the tilt test the levels of HR (p = 0.0005) and TPRI (p = 0.0128) were significantly higher but SI (p > 0.001) and CI (p = 0.0006) were significantly lower in the study group compared to the control.

Conclusions

Multiannual strength-endurance training connected with rowing activities substantially modulates the activity of cardiovascular and autonomic nervous system, influences the volumetric workload of the heart and structural changes, and increases the sensitivity of reflexes of arterial baroreceptors.

Activity and Exercise Intolerance After Concussion: Identification and Management of Postural Orthostatic Tachycardia Syndrome

Supplemental Digital Content is Available in the Text.

Background and Purpose:

Postural orthostatic tachycardia syndrome (POTS) is increasingly recognized as a complication affecting recovery from concussion. Individuals with POTS demonstrate refractory dizziness, lightheadedness, cognitive dysfunction, fatigue, headache, chronic pain, nausea and gastrointestinal dysmotility, activity and exercise intolerance, syncope, and tachycardia. Subtypes of POTS may include hypovolemia, hyperadrenergic states, autonomic neuropathy, and underlying autoimmunity, which may variably impact response to rehabilitation in varying ways. The subtle presentation of POTS postconcussion is often mistaken for underlying anxiety, conversion disorder, or lack of motivation for recovery. This article will present clinical features of POTS that may arise after concussion, and propose a role for physical therapists in the diagnosis and management of POTS during concussion recovery.

Summary of Key Points:

Data recorded and entered into a database during clinic visits from a large pediatric institution indicate that 11.4% of individuals diagnosed with POTS report onset of symptoms within 3 months of sustaining a concussion. Activation of the sympathetic nervous system can result in lightheadedness, shortness of breath, chest pain, tachycardia, palpitations on standing or with exertion, and activity and exercise intolerance. Identified comorbidities in people with POTS such as joint hypermobility and autoimmune disorders can further influence recovery.

Recommendations for Clinical Practice:

Physical therapists may identify signs and symptoms of POTS in a subset of individuals who remain refractory to typical interventions and who exhibit symptom exacerbation with orthostatic activity. Incorporation of an individualized POTS exercise program into current established concussion interventions may be useful, with emphasis on initial recumbent exercises and ongoing physical therapy assessment of exercise tolerance for dosing of activity intensity and duration.

Video Abstract available for more insights from the authors (see Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A211).

Quantifying Activity Levels After Sport-Related Concussion Using Actigraph and Mobile (mHealth) Technologies

CONTEXT

Interest in identifying the effects of physical and mental activity on recovery after sport-related concussion is growing. Clinical studies of concussed athletes' activities require well-validated methods for tracking their intensity and timing.

OBJECTIVE

To develop and validate a novel multimodal approach to monitoring activity postconcussion using mobile (mHealth) technologies.

DESIGN

Cohort study.

SETTING

Translational research unit.

PATIENTS OR OTHER PARTICIPANTS

A total of 40 high school and collegiate football players were evaluated at preseason and followed longitudinally after either concussion (n = 25; age = 17.88 ± 1.74 years, height = 182.07 ± 8.08 cm, mass = 98.36 ± 21.70 kg) or selection as a nonconcussed control (n = 15; age = 18.27 ± 1.83 years, height = 180.01 ± 7.19 cm, mass = 93.83 ± 24.56 kg).

MAIN OUTCOME MEASURE(S)

Participants wore a commercial actigraph and completed a daily mobile survey for 2 weeks. Analyses focused on comparisons between groups for actigraph-based physical activity and self-reported physical and mental activity during the follow-up period.

RESULTS

For the first 2 days postinjury, objective measures showed fewer daily steps in concussed (6663 ± 2667 steps) than in control (11 148 ± 3381 steps) athletes (P < .001), and both objective and self-reported measures indicated less moderate to vigorous physical activity in concussed (27.6 ± 32.6 min/d and 25.0 ± 43.6 min/d, respectively) than in control (57.3 ± 38.6 min/d and 67.5 ± 40.1 min/d, respectively) athletes (both P values < .05). Correlations between objective and self-reported measures of moderate to vigorous physical activity were moderate across select 1-week and 2-week averages. We observed no group differences in self-reported mental activities.

CONCLUSIONS

Physical activity after sport-related concussion varied widely across athletes but on average was reduced during the acute and early subacute postinjury periods for both objective and self-reported measures. The lack of differences in mental activities between groups may reflect limited change in mental exertion postconcussion or difficulty accurately measuring mental activities. Assessing concussed athletes' activities using actigraphy and self-reported scales may help monitor their compliance with activity recommendations and be useful in studies aimed at better understanding the effects of physical activity on concussion recovery.

Active recovery from concussion

PURPOSE OF REVIEW

Recent studies are challenging the utility of prolonged rest as treatment for concussion and postconcussion syndrome (PCS). The purpose of this paper is to review the evidence for active recovery from concussion and PCS.

RECENT FINDINGS

Emerging data identify the central role of autonomic nervous system (ANS) dysfunction in concussion pathophysiology. The exercise intolerance demonstrated by athletes after sport-related concussion may be related to abnormal ANS regulation of cerebral blood flow. As aerobic exercise training improves ANS function, sub-symptom threshold exercise treatment is potentially therapeutic for concussion. A systematic assessment of exercise tolerance using the Buffalo Concussion Treadmill Test has been safely employed to prescribe a progressive, individualized subthreshold aerobic exercise treatment program that can return patients to sport and work. Multiple studies are demonstrating the efficacy of an active approach to concussion management.

SUMMARY

Sustained rest from all activities after concussion, so-called 'cocoon therapy', is not beneficial to recovery. Evidence supports the safety, tolerability, and efficacy of controlled sub-symptom threshold aerobic exercise treatment for PCS patients. Further study should determine the efficacy and optimal timing, dose, and duration of subthreshold aerobic exercise treatment acutely after concussion because early intervention has potential to prevent PCS.

Face cooling exposes cardiac parasympathetic and sympathetic dysfunction in recently concussed college athletes

We tested the hypothesis that concussed college athletes (CA) have attenuated parasympathetic and sympathetic responses to face cooling (FC). Eleven symptomatic CA (age: 20 ± 2 years, 5 women) who were within 10 days of concussion diagnosis and 10 healthy controls (HC; age: 24 ± 4 years, 5 women) participated. During FC, a plastic bag filled with ice water (~0°C) was placed on the forehead, eyes, and cheeks for 3 min. Heart rate (ECG) and blood pressure (photoplethysmography) were averaged at baseline and every 60 sec during FC. High‐frequency (HF) power was obtained from spectral analysis of the R‐R interval. Data are presented as a change from baseline. Baseline heart rate (HC: 61 ± 12, CA: 57 ± 12 bpm; P = 0.69), mean arterial pressure (MAP) (HC: 94 ± 10, CA: 96 ± 13 mmHg; P = 0.74), and HF (HC: 2294 ± 2314, CA: 2459 ± 2058 msec²; P = 0.86) were not different between groups. Heart rate in HC decreased at 2 min (−7 ± 11 bpm; P = 0.02) but did not change in CA (P > 0.43). MAP increased at 1 min (HC: 12 ± 6, CA: 6 ± 6 mmHg), 2 min (HC: 21 ± 7, CA: 11 ± 7 mmHg), and 3 min (HC: 20 ± 6, CA: 13 ± 7 mmHg) in both groups (P < 0.01 for all) but the increase was greater at each interval in HC (P < 0.02). HF increased at 1 min (12354 ± 11489 msec²; P < 0.01) and 2 min (5832 ± 8002 msec²; P = 0.02) in HC but did not change in CA (P > 0.58). The increase in HF at 1 min was greater in HC versus CA (P < 0.01). These data indicate that symptomatic concussed patients have impaired cardiac parasympathetic and sympathetic activation.

Evidence of a distinct peripheral inflammatory profile in sport-related concussion

Background

Inflammation is considered a hallmark of concussion pathophysiology in experimental models, yet is understudied in human injury. Despite the growing use of blood biomarkers in concussion, inflammatory biomarkers have not been well characterized. Furthermore, it is unclear if the systemic inflammatory response to concussion differs from that of musculoskeletal injury. The purpose of this paper was to characterize systemic inflammation after injury in athletes with sport-related concussion or musculoskeletal injury.

Methods

A prospective, observational cohort study was conducted employing 175 interuniversity athletes (sport-related concussion, n = 43; musculoskeletal injury, n = 30; healthy, n = 102) from 12 sports at a sports medicine clinic at an academic institution.

High-sensitivity immunoassay was used to evaluate 20 inflammatory biomarkers in the peripheral blood of athletes within 7 days of injury (subacute) and at medical clearance. Healthy athletes were sampled prior to the start of their competitive season. Partial least squares regression analyses were used to identify salient biomarker contributions to class separation between injured and healthy athletes, as well as to evaluate the relationship between biomarkers and days to recovery in injured athletes.

Results

In the subacute period after injury, compared to healthy athletes, athletes with sport-related concussion had higher levels of the chemokines’ monocyte chemoattractant protein-4 (p < 0.001) and macrophage inflammatory protein-1β (p = 0.001); athletes with musculoskeletal injury had higher levels of thymus and activation-regulated chemokine (p = 0.001). No significant differences in biomarker profiles were observed at medical clearance. Furthermore, concentrations of monocyte chemoattractant protein-1 (p = 0.007) and monocyte chemoattractant protein-4 (p < 0.001) at the subacute time point were positively correlated with days to recovery in athletes with sport-related concussion, while thymus and activation-regulated chemokine was (p = 0.001) positively correlated with days to recovery in athletes with musculoskeletal injury.

Conclusion

Sport-related concussion is associated with perturbations to systemic inflammatory chemokines that differ from those observed in athletes with a musculoskeletal injury. These results support inflammation as an important facet of secondary injury after sport-related concussion that can be measured systemically in a human model of injury.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1402-y) contains supplementary material, which is available to authorized users.

Brain-Heart Interactions in Traumatic Brain Injury

The cardiovascular manifestations associated with nontraumatic head disorders are commonly known. Similar manifestations have been reported in patients with traumatic brain injury (TBI); however, the underlying mechanisms and impact on the patient's clinical outcomes are not well explored. The neurocardiac axis theory and neurogenic stunned myocardium phenomenon could partly explain the brain-heart link and interactions and can thus pave the way to a better understanding and management of TBI. Several observational retrospective studies have shown a promising role for beta-adrenergic blockers in patients with TBI in reducing the overall TBI-related mortality. However, several questions remain to be answered in clinical randomized-controlled trials, including population selection, beta blocker type, dosage, timing, and duration of therapy, while maintaining the optimal mean arterial pressure and cerebral perfusion pressure in patients with TBI.