A Physiological Approach to Assessment and Rehabilitation of Acute Concussion in Collegiate and Professional Athletes

Does Physiologic Post-Concussion Disorder Cause Persistent Post-Traumatic Headache?

PURPOSE OF REVIEW

One system classifies patients with symptoms after concussion into physiologic, vestibulo-ocular, cervicogenic, and mood/cognition post-concussion disorders (PCD) based upon the preponderance of specific symptoms and physical impairments. This review discusses physiologic PCD and its potential relationship to the development of persistent post-traumatic headaches (PPTH).

RECENT FINDINGS

Headache is the most reported symptom after a concussion. Headaches in physiologic PCD are suspected to be due to abnormal cellular metabolism, subclinical neuroinflammation, and dysfunction of the autonomic nervous system (ANS). These abnormalities have been linked to the development of migraine-like and neuralgia-related PPTH. Physiologic PCD is a potential cause of PPTH after a concussion. Future research should focus on how to prevent PPTH in patients with physiologic PCD.

Sub-symptom threshold aerobic exercise for patients with persisting post-concussion symptoms and exercise intolerance after mild traumatic brain injury - a study protocol with a nested feasibility study for a randomized controlled trial

BACKGROUND

Persistent post-concussion symptoms (PPCS) affect between 34 and 46% after a mild traumatic brain injury (mTBI). Many also experience exercise intolerance. Sub-symptom threshold aerobic exercise, SSTAE (exercise at an intensity level that does not increase symptoms) is proposed as a treatment to both reduce the symptom burden and increase the exercise tolerance after the injury. It is unclear if this also applies in a more chronic phase after mTBI.

MAIN PURPOSE

The main purpose of this study is to evaluate whether SSTAE in addition to ordinary rehabilitation will lead to clinically meaningful improvement of symptom burden, normalize exercise tolerance, increase physical activity, improve health-related quality of life, and reduce patient-specific activity limitations compared to a control group that only receives ordinary rehabilitation.

DESIGN

Randomized, controlled, single-blind parallel-group study with three measurement times; T0 at baseline, T1 after the intervention and T2 six months after T1.

METHODS

Patients between the ages of 18 and 60 with exercise intolerance and persistent PPCS (> 3 months) will be recruited to the study and randomized to two groups. All patients will receive follow-up at the outpatient TBI clinic. The intervention group will in addition receive SSTAE for 12 weeks with exercise diaries and a retest every 3 weeks for optimal dosage and progression. The Rivermead post-concussion symptoms questionnaire will be the main outcome measure. The secondary outcome measure will be a test of exercise tolerance-the Buffalo Concussion Treadmill Test. Other outcome measures include the patient-specific functional scale that measures patient-specific activity limitations, as well as outcome measures for diagnosis-specific health-related quality of life, anxiety and depression, specific symptoms such as dizziness, headache and fatigue, and physical activity.

DISCUSSION

This study will add knowledge about the effect of SSTAE and whether it should be implemented in rehabilitation for the adult population with persistent PPCS after mTBI. The nested feasibility trial showed that the SSTAE intervention was safe and that the study procedures and delivery of the intervention overall were feasible. However, minor amendments to the study protocol were made prior to the commencement of the RCT.

TRIAL REGISTRATION

Clinical Trials.gov, NCT05086419. Registered on September 5th, 2021.

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.

Efficacy of aerobic exercise following concussion: a narrative review

Concussion is a type of mild traumatic brain injury which results in symptoms within the physical, cognitive, emotional, and sleep domains. Historically, guidelines established by expert opinion have recommended rest during the initial stages of recovery following a concussion until symptom resolution. However, recent recommendations have shifted to advise an initial period of 24-48 h of rest immediately following concussion with the gradual introduction of light-to-moderate intensity aerobic exercise thereafter. Given the relatively recent transition in recommendations, the aim of this review is to provide an overview of the current literature on the efficacy of aerobic exercise following concussion. The current literature is limited to studies assessing the impact of standardized aerobic exercise following concussion. Upon review, literature suggests participating in aerobic exercise below the point of symptom exacerbation is safe in both the acute and chronic post-concussion symptom stages of recovery and does not delay time to medical clearance. Future large-scale randomized controlled trials assessing the impact of aerobic exercise and differences between males and females would help support the current evidence suggesting aerobic exercise could improve time to recovery following concussion and identify any sex differences in response. As well, future studies with the purpose of identifying optimal aerobic exercise volume and intensity in the treatment of concussion could improve the specificity of the current guidelines.

Visual disorders and mal de debarquement syndrome: a potential comorbidity questionnaire-based study

Aim: Mal de debarquement syndrome (MdDS) is a neurological condition characterized by a constant sensation of self-motion; onset may be motion-triggered (MT) or non-motion-triggered/spontaneous (NMT/SO). People with MdDS experience similar symptoms to those with vertical heterophoria, a subset of binocular visual dysfunction. Hence, we aimed to explore potential visual symptom overlaps. Methods: MdDS patients (n = 196) and controls (n = 197) completed a visual health questionnaire. Results: Compared with controls, the MdDS group demonstrated higher visual disorder scores and visual complaints. NMT/SO participants reported unique visual symptoms and a higher prevalence of mild traumatic brain injury. Conclusion: Our findings suggest visual disorders may coexist with MdDS, particularly the NMT/SO subtype. The difference in visual dysfunction frequency and medical histories between subtypes, warrants further investigation into differing pathophysiological mechanisms.

Pediatric Sports-Related Concussion: An Approach to Care

Sports-related concussion (SRC) is a common sports injury in children and adolescents. With the vast amount of youth sports participation, an increase in awareness of concussion and evidence that the injury can lead to consequences for school, sports and overall quality of life, it has become increasingly important to properly diagnose and manage concussion. SRC in the student athlete is a unique and complex injury, and it is important to highlight the differences in the management of child and adolescent concussion compared with adults. This review focuses on the importance of developing a multimodal systematic approach to diagnosing and managing pediatric sports-related concussion, from the sidelines through recovery.

Progression through return-to-sport and return-to-academics guidelines for concussion management and recovery in collegiate student athletes: findings from the Ivy League-Big Ten Epidemiology of Concussion Study

Objective

To examine the progression of collegiate student athletes through five stages of a return-to-activity protocol following sport-related concussion (SRC).

Methods

In a multisite prospective cohort study, we identified the frequency of initial 24–48 hours physical and cognitive rest, and the sequence of (1) symptom resolution and return to (2) exertion activity, (3) limited sport, (4) full sport and (5) full academics. In resulting profiles we estimated the likelihood of return to full sport ≤14 days or prolonged >28 days and tested for variability based on timing of the stages.

Results

Among 1715 athletes with SRC (31.6% females), 67.9% had 24–48 hours initial physical and cognitive rest. The median was 6 days to return to full academics, 8 days to symptom resolution and 9 days to exertion. Three profiles emerged; all had the same sport-specific return progression, but varied in the relative timing of full academics. In unadjusted analyses, full academics as the first stage corresponded to the longest time to return to full sport, and initiating exertion the same day as symptom resolution resulted in the shortest time. In adjusted regression analyses, athletes initiating full academics while still symptomatic were 21.5% less likely (95% CI −27.4% to −15.5%) to return to full sport ≤14 days and, analogously, 19.1% more likely (95% CI 13.4% to 24.7%) to have prolonged return >28 days. While additionally controlling for initial rest, sex, symptom count and concussion history, the likelihood of prolonged return >28 days was 37.0% (95% CI 25.2% to 48.8%) in athletes initiating exertion considerably before symptoms resolved (ie, 7+ days), but only 3.6% (95% CI −1.4% to 8.6%) in athletes initiating exertion shortly before achieving symptom resolution (ie, 3–4 days).

Conclusion

We found evidence that sequential progressions were consistent with current recommendations including brief initial rest, and the initiation and relative timing of each stage impacted the final return-to-sport outcome.

Neuropsychological and neuropsychiatric recovery from mild traumatic brain injury

PURPOSE OF REVIEW

Mild traumatic brain injury (mTBI) is a significant public health concern for children. This review summarizes recent literature on early symptoms and neuropsychiatric and neuropsychological outcomes following pediatric mTBI and highlights factors that predict prolonged recovery. Evidence-based recommendations for assessment and treatment are also discussed.

RECENT FINDINGS

Whereas most children recover within 1 month after mTBI, 10-30% of children experience lingering neuropsychiatric or neuropsychological symptoms 3 months or more after injury. For the subset who experience prolonged recovery, new or worsening emotional and behavioral symptoms are the most frequent concerns. Recent research has suggested that specific factors, including preinjury mental health concerns, female sex, and family characteristics, are associated with increased risk of experiencing prolonged recovery. Early management includes reassurance, brief rest (1-3 days), and gradual return to typical activities. When symptoms linger for more than 4 weeks, evaluation in a specialty clinic is recommended and multimodal therapies are considered. Active recovery models, which include gradual return to aerobic exercise and cognitive behavioral approaches, are promising for the management of prolonged symptoms.

SUMMARY

A minority of children with mTBI experience prolonged neuropsychiatric or neuropsychological concerns. While our understanding of pediatric mTBI is growing, and recommendations for assessment and management have been developed, many gaps remain.

Assessment of Saccades and Gaze Stability in the Diagnosis of Pediatric Concussion

OBJECTIVE

To evaluate the discriminatory ability of different repetition increments of saccades and gaze stability testing for diagnosing concussion in adolescents.

DESIGN

Cross-sectional.

SETTING

Suburban high school and academic pediatric tertiary care center.

PARTICIPANTS

Sixty-nine adolescent athletes within 28 days of a sports- or recreation-related concussion and 69 adolescent athletes without recent concussion.

ASSESSMENT OF INDEPENDENT VARIABLES

Symptom provocation with horizontal and vertical saccades and gaze stability testing performed up to 30 repetitions.

MAIN OUTCOME MEASURES

Sensitivity and specificity at 10-repetition increments (≤10, ≤20, ≤30) and area under the receiver operating characteristic curves (AUC) of a visio-vestibular examination (VVE) subscore, scored 0 to 4 based on the number of assessments with symptom provocation, at each repetition increment.

RESULTS

Sensitivity improved when increasing from ≤10 to ≤20 to ≤30 repetitions for horizontal (25% to 50% to 69%) and vertical (32% to 52% to 74%) saccades and horizontal (19% to 45% to 71%) and vertical (23% to 45% to 72%) gaze stability. Specificity was comparable at ≤10 and ≤20 repetitions, but decreased at ≤30 repetitions across assessments. For a VVE subscore (0-4) based on the number of symptomatic assessments, the discriminatory ability of the test was highest at ≤20 repetitions (AUC of 0.79) with an optimal subscore of one (sensitivity 59%, specificity 96%).

CONCLUSIONS

A VVE including a higher threshold level of repetitions for saccades and gaze stability has improved discriminatory ability for concussion, with an optimized AUC of 0.79 at ≤20 repetitions.

CLINICAL RELEVANCE

The findings in this study suggest that a higher threshold level of repetitions of 2 commonly used visio-vestibular assessments enables clinicians to more accurately diagnose youth concussion.

Greater symptom burden results in reduced exercise tolerance in adolescents following concussion

OBJECTIVES

To explore the relationship between symptoms and exercise tolerance in adolescents following concussion.

METHODS

A retrospective analysis of 417 adolescents who attended a concussion service between January 2015 and April 2021 was performed, with 149 meeting eligibility criteria for inclusion. Post-Concussion Symptom Scale (PCSS) and graded exercise tolerance time (min) were assessed at initial and follow-up visits. Spearman's correlation was used to examine the relationship between PCSS scores and exercise time.

RESULTS

Adolescents (n = 149, 13.9 ± 1.7 years, 66.4% male) presented at 28.6 ± 19.7 days post-injury. Statistically significant correlations were identified between initial (r = -0.36, p < .001) and follow-up (r = -0.41, p < .001) PCSS scores and exercise time among all participants. Initial PCSS and initial exercise time were inversely correlated for males (r = -0.24, p = .018) and females (r = -0.22, p = .127). Follow-up PCSS and follow-up exercise time were inversely correlated for males (r = -0.30, p = .003) and females (r = -0.35, p = .014).

CONCLUSION

There is a statistically significant relationship between higher PCSS and poorer exercise time and both factors should be considered together to provide the most accurate assessment, particularly in females.

Mild Traumatic Brain Injury/Concussion Initiates an Atypical Astrocyte Response Caused by Blood-Brain Barrier Dysfunction

Mild traumatic brain injury/concussion (mTBI) accounts for 70-90% of all reported TBI cases and causes long-lasting neurological consequences in 10-40% of patients. Recent clinical studies revealed increased blood-brain barrier (BBB) permeability in mTBI patients, which correlated with secondary damage after mTBI. However, the cascade of cellular events initiated by exposure to blood-borne factors resulting in sustained damage is not fully understood. We previously reported that astrocytes respond atypically to mTBI, rapidly losing many proteins essential to their homeostatic function, while classic scar formation does not occur. Here, we tested the hypothesis that mTBI-induced BBB damage causes atypical astrocytes through exposure to blood-borne factors. Using an mTBI mouse model, two-photon imaging, an endothelial cell-specific genetic ablation approach, and serum-free primary astrocyte cultures, we demonstrated that areas with atypical astrocytes coincide with BBB damage and that exposure of astrocytes to plasma proteins is sufficient to initiate loss of astrocyte homeostatic proteins. Although mTBI resulted in frequent impairment of both physical and metabolic BBB properties and leakage of small-sized blood-borne factors, deposition of the coagulation factor fibrinogen or vessel rupture were rare. Surprisingly, even months after mTBI, BBB repair did not occur in areas with atypical astrocytes. Together, these findings implicate that even relatively small BBB disturbances are sustained long term, and render nearby astrocytes dysfunctional, likely at the cost of neuronal health and function.

Collision avoidance behaviors of recently concussed female rugby players with an approaching person

BACKGROUND

Successful collision avoidance requires individuals to use readily available perceptual information to make decisions and act within their action capabilities. Female varsity rugby players use time-to-collision information to get closer to an obstacle before deviating; however, following a sport-related concussion (SRC), individuals may not be able to use the same strategies due to poorer action boundary perception. The current study examined the effects of a SRC on collision avoidance with an approaching person.

METHODS

Non-concussed female varsity rugby athletes (ATH, n = 10) and recently concussed but asymptomatic teammates (CONC, n = 3) were instructed to walk at a comfortable pace and avoid colliding with an approaching confederate. Time-to-collision (TTC), rate of medial-lateral (ML) avoidance, and ML spatial requirement were calculated and analyzed using mixed repeated measures ANOVAs.

FINDINGS

There were no physical characteristic differences between groups (p < 0.05) and no collisions occurred on any of the trials. However, CONC displayed larger TTC than ATH (p = 0.03), indicative of a more cautious avoidance strategy.

INTERPRETATION

While rugby players are trained to avoid opponents, a more cautious strategy following a SRC may reflect visuomotor detraining and changes in embodiment. This suggests that despite being asymptomatic, there is a reduced sense of agency during dynamic perception-action tasks and persistent alterations between pre-concussion and post-concussion self.

Machine Learning for Subtyping Concussion Using a Clustering Approach

Background: Concussion subtypes are typically organized into commonly affected symptom areas or a combination of affected systems, an approach that may be flawed by bias in conceptualization or the inherent limitations of interdisciplinary expertise.

Objective: The purpose of this study was to determine whether a bottom-up, unsupervised, machine learning approach, could more accurately support concussion subtyping.

Methods: Initial patient intake data as well as objective outcome measures including, the Patient-Reported Outcomes Measurement Information System (PROMIS), Dizziness Handicap Inventory (DHI), Pain Catastrophizing Scale (PCS), and Immediate Post-Concussion Assessment and Cognitive Testing Tool (ImPACT) were retrospectively extracted from the Advance Concussion Clinic's database. A correlation matrix and principal component analysis (PCA) were used to reduce the dimensionality of the dataset. Sklearn's agglomerative clustering algorithm was then applied, and the optimal number of clusters within the patient database were generated. Between-group comparisons among the formed clusters were performed using a Mann-Whitney U test.

Results: Two hundred seventy-five patients within the clinics database were analyzed. Five distinct clusters emerged from the data when maximizing the Silhouette score (0.36) and minimizing the Davies-Bouldin score (0.83). Concussion subtypes derived demonstrated clinically distinct profiles, with statistically significant differences (p < 0.05) between all five clusters.

Conclusion: This machine learning approach enabled the identification and characterization of five distinct concussion subtypes, which were best understood according to levels of complexity, ranging from Extremely Complex to Minimally Complex. Understanding concussion in terms of Complexity with the utilization of artificial intelligence, could provide a more accurate concussion classification or subtype approach; one that better reflects the true heterogeneity and complex system disruptions associated with mild traumatic brain injury.

Evaluating the Vestibulo-Ocular Reflex Following Traumatic Brain Injury: A Scoping Review

Purpose:To identify the tests and tools used to evaluate vestibulo-ocular reflex (VOR) function after traumatic brain injury (TBI) in all age groups and across TBI severity.Methods: An electronic search was conducted to include relevant peer-reviewed literature published up to November 2019. Studies included those done with humans, of all ages, and had assessments of oculomotor and/or vestibulo-ocular function in TBI.Results: Of the articles selected (N = 48), 50% were published in 2018/2019. A majority targeted mild TBI, with equal focus on non-computerized versus computerized measures of VOR. Computerized assessment tools used were videonystagmography, dynamic visual acuity/gaze stability, rotary chair, and caloric irrigation. Non-computerized tests included the head thrust, dynamic visual acuity, gaze stability, head shaking nystagmus, rotary chair tests and the vestibular/oculomotor screening tool. High variability in administration protocols were identified. Namely: testing environment, distances/positioning/equipment used, active/passive state, procedures, rotation frequencies, and variables observed.Conclusions: There is a rapid growth of literature incorporating VOR tests in mild TBI but moderate and severe TBI continues to be under-represented. Determining how to pair a clinical test with a computerized tool and developing standardized protocols when administering tests will help in developing an optimal battery assessing the VOR in TBI.

Pre-frontal Cortex Oxygenation Changes During Aerobic Exercise in Elite Athletes Experiencing Sport-Related Concussion

Aims: Recent research suggests that aerobic exercise can be performed safely within the first week following a concussion injury and that early initiation of exercise may speed recovery. To better understand the physiological changes during a concussion, we tested the hypothesis that mild-to-intense exercise testing can be performed within days immediately following injury, and can be used to discern differences between the concussed and normal healthy state. Thus, the purpose was to observe the cerebral hemodynamic responses to incremental exercise testing performed acutely post-concussion in high-performance athletes. Methods: This study was a within- and between-experimental design, with seven male university ice hockey teams participating. A subgroup of five players acted as control subjects (CON) and was tested at the same time as the 14 concussed (mTBI) players on Day 2, 4, and 7 post-concussion. A 5-min resting baseline and 5-min exercise bouts of mild (EX1), moderate (EX2), and high (EX3) intensity exercise were performed on a cycle ergometer. Near-infrared spectroscopy was used to monitor pre-frontal cortex oxy-haemoglobin (HbO2), deoxy-haemoglobin (HHb), and total blood volume (tHb) changes. Results: ANOVA compared differences between testing days and groups, and although large percentage changes in HbO2 (20-30%), HHb (30-40%), and tHb (30-40%) were recorded, no significant (p ≤ 0.05) differences in cerebral hemodynamics occurred between mTBI vs. CON during aerobic exercise testing on any day post-injury. Furthermore, there was a linear relationship between exercise intensity vs. cerebral hemodynamics during testing for each day (r 2 = 0.83-0.99). Conclusion: These results demonstrate two novel findings: (1) mild-to-intense aerobic exercise testing can be performed safely as early as Day 2 post-concussion injury in a controlled laboratory environment; and (2) evidence-based objective measures such as cerebral hemodynamics can easily be collected using near-infrared spectroscopy (NIRS) to monitor physiological changes during the first-week post-injury. This research has important implications for monitoring physiological recovery post-injury and establishing new rehabilitation guidelines.

Evaluation of Early Submaximal Exercise Tolerance in Adolescents with Symptomatic Sport-related Concussion

PURPOSE

This study aimed to compare cardiorespiratory response to a graded aerobic exercise challenge between adolescents with symptomatic sport-related concussion (SSRC) and healthy control subjects.

METHODS

A quasiexperimental nonrandomized study at a multidisciplinary pediatric concussion program was conducted. Thirty-four adolescents with SSRC (19 males and 15 females) and 40 healthy control subjects (13 males and 27 females) completed the Buffalo Concussion Treadmill Testing (BCTT) until either symptom exacerbation or volitional fatigue. Main outcome measures included heart rate (HR), oxygen consumption (V˙O2), carbon dioxide production (V˙CO2), and minute ventilation (V˙E) at rest and at test termination, and change from rest in variables (ΔHR, ΔV˙O2, ΔV˙CO2, and ΔV˙E) during the first five stages of the BCTT. Main outcomes were analyzed using three-way mixed-model ANOVA, with group status (control vs SSRC) and sex (male vs female) as between-subject factors, and time (BCTT stage) as the within-subject factor.

RESULTS

No group differences in resting HR, systolic and diastolic blood pressure, ΔV˙O2, V˙CO2, and V˙E were observed. During the first five stages of the BCTT, no group differences in ΔV˙O2, V˙CO2, and V˙E were observed; however, SSRC patients demonstrated higher RPE (P < 0.0005) compared with control subjects. No sex-based differences were observed among SSRC patients on measures collected at rest and during early stages of BCTT.

CONCLUSIONS

Although SSRC patients exhibited higher RPE during a graded aerobic exercise challenge, no differences in cardiorespiratory response were observed compared with control subjects exercising at equivalent workloads. Further work is needed to elucidate the physiological mechanisms underlying exercise intolerance after SSRC.

Why exercise may be beneficial in concussion rehabilitation: A cellular perspective

INTRODUCTION

Concussion diagnosis and rehabilitation management has become a prevalent area of research, and yet much is still unknown about these complex injuries. Historically, exercise prescription post-concussion was conservatively used for rehabilitation due to the suspected harmful effects that exercise can have on damaged neurons, and increase in symptoms. However, there has been a shift to implement exercise earlier into recovery as several studies have demonstrated positive outcomes.

OBJECTIVE

The objective of this literature review is to update the reader about new advances in concussion research related to the beneficial effects of physical activity from both a neurometabolic and a broader physiological perspective, using gene expression as a vehicle to demonstrate why and how physical activity has the capacity to optimize recovery from a cellular perspective. To further this clinical guideline, the evidence must continue to support these positive outcomes from an inductive and deductive physiologic approach (i.e., the clinical evidence aligned from a micro- to macroscopic approach and vice versa).

DESIGN

Narrative review.

METHODS

Pubmed and Medline were used with the following key words: concussion and, physical activity, neurometabolic, gene regulation, trauma, nervous system, mild head injury, acute exercise, cellular physiology and pathophysiology.

CONCLUSION

It is our contention that understanding the cellular perspective will help guide clinical management, and promote research into post-concussion exercise.