Impaired Dynamic Cerebrovascular Autoregulation in Adolescent Concussion

Although cerebrovascular impairments are believed to contribute to concussion symptoms, little information exists regarding brain vasomotor control in adolescent concussion, particularly during changes in arterial blood pressure (ABP). This research tested the hypothesis that adolescent concussion is marked by impaired dynamic cerebral autoregulation (dCA). Thirty concussed adolescents and thirty healthy controls completed two sit-to-stand trials. Cerebral blood flow velocity and ABP were measured continuously. Cerebrovascular resistance (CVR) was calculated and the rate of drop in CVR relative to the change in ABP provided the rate of regulation (RoR). The concussed adolescents were followed through rehabilitation for up to 12-weeks. At the first visit, the concussed adolescents demonstrated reduced RoR compared with the healthy controls (0.16±0.04 vs. 0.21±0.07 sec-1; P≤0.001). At the concussed adolescents final visit, RoR recovers to levels seen in the healthy controls (0.21±0.08 vs. 0.21±0.07 sec-1; P=0.93). Concussed adolescents demonstrate an impairment in dCA that recovers with symptoms

Head Trauma not Associated with Long Term Effects on Autonomic Function

International Journal of Exercise Science 14(3): 779-790, 2021. Contact-sports can elicit concussions, which impacts autonomic function, as well as elicit repetitive head trauma, where autonomic function has not yet been assessed. The purpose of this study was to determine if differences in autonomic function exist among three groups (CTRL: healthy non-contact-sport participant, RHT: repetitive head trauma contact-sport participant, CONC: previous concussion). Forty participants (16 men and 24 women), aged 18-37 (22 ± 3), participated in the study. Participants were grouped based on their sport and concussion history (CTRL, RHT, and CONC). Body composition was measured via air displacement plethysmography. Prior to testing, participants were outfitted with equipment to evaluate heart rate, blood pressure, and cerebral-artery blood flow velocity (CBFv). The participant performed against three stimuli: deep breathing, Valsalva maneuver, and a 70° head-up tilt test. Following autonomic function testing, a YMCA submaximal cycle test was performed. All group comparisons were analyzed using a one-way ANOVA and all data are presented as means ± standard deviation. The results of this study indicated that the groups did not differ in respiratory sinus arrhythmia (CTRL: 22 ± 6 bpm, RHT: 21 ± 8 bpm, CONC: 19 ± 7 bpm, p = 0.471), Valsalva ratio (CTRL: 2.19 ± 0.39, RHT: 2.09 ± 0.37, CONC: 2.00 ± 0.47, p = 0.519), CBFv (CTRL: 47.74 ± 25.28 cm/s, RHT: 40.99 ± 10.93 cm/s, CONC: 43.97 ± 17.55 cm/s, p = 0.657), or tilt time (CTRL: 806.09 ± 368.37 sec, RHT: 943.07 ± 339.54 sec, CONC: 978.40 ± 387.98 sec, p = 0.479). However, CONC (113.24 ± 11.64 mmHg) had a significantly higher mean systolic blood pressure during the tilt test than CTRL (102.66 ± 7.79 mmHg, p = 0.026), while RHT (107.9 ± 9.0 mmHg) was not significantly different than CTRL (p = 0.39) or CONC (p = 0.319). The results of this study are the first step in determining if long-lasting deficits to the autonomic nervous system occur following a diagnosis of concussion. However, concussions do not seem to have lasting effects on autonomic function. Overwhelmingly, dysautonomia is not present during chronic recovery from concussions or in individuals with RHT from contact-sports. In the future, sex should be considered as a variable

Cerebral Autoregulation Is Disrupted Following a Season of Contact Sports Participation

Repetitive subconcussive head impacts across a season of contact sports participation are associated with a number of deficits in brain function. To date, no research has investigated the effect of such head impact exposure on dynamic cerebral autoregulation (dCA). To address this issue, 179 elite, junior-level (age 19.6 ± 1.5 years) contact sport (ice hockey, American football) athletes were recruited for pre-season testing. Fifty-two non-concussed athletes returned for post-season testing. Fifteen non-contact sport athletes (age 20.4 ± 2.2) also completed pre- and postseason testing. dCA was assessed via recordings of beat-by-beat mean arterial pressure (MAP) and middle cerebral artery blood velocity (MCAv) using finger photoplethysmography and transcranial Doppler ultrasound, respectively, during repetitive squat-stand maneuvers at 0.05 and 0.10 Hz. Transfer function analysis was used to determine Coherence (correlation), Gain (response amplitude), and Phase (response latency) of the MAP-MCAv relationship. Results showed that in contact sport athletes, Phase was reduced (p = 0.027) and Gain increased (p < 0.001) at post-season compared to pre-season during the 0.10 Hz squat-stand maneuvers, indicating cerebral autoregulatory impairment in both the latency and magnitude of the response. Changes in Phase were greater in athletes experiencing higher numbers and severity of head impacts. By contrast, no changes in dCA were observed in non-contact sport controls. Taken together, these results demonstrate that repetitive subconcussive head impacts occurring across a season of contact sports participation are associated with exposure-dependent impairments in the cerebrovascular pressure-buffering system capacity. It is unknown how long these deficits persist or if they accumulate year-over-year

Robotic Semi-Automated Transcranial Doppler Assessment of Cerebrovascular Autoregulation in Post Concussional Syndrome: Methodological Considerations

Abstract Introduction Post-concussive syndrome (PCS) refers to a constellation of physical, cognitive, and emotional symptoms after traumatic brain injury (TBI). Despite its incidence, the underlying mechanisms are unclear. We hypothesised that impaired cerebral autoregulation (CA) is a contributor. Method A prospective, observational study was integrated into outpatient clinics at a tertiary neurosurgical centre. Data points included: demographics, symptoms (Post-Concussion Symptom Scale [PCSS]), neuropsychological assessment (Cambridge Neuropsychological Test Automated-Battery [CANTAB]) and cerebrovascular metrics (Mxa co-efficient and the transient hyperaemic-response ratio [THRR]) - via transcranial Doppler (TCD), plethysmography and bespoke software (ICM+). Results 12 participants were recruited with 2 excluded after unsuccessful cerebrovascular TCD insonation. 10 participants (5 TBI patients, 5 healthy controls) were included in the analysis (median age 26.5, male:female 7:3). Median PCSS scores were 6/126 (TBI subgroup). Median CANTAB percentiles were 78 (healthy controls) and 25 (TBI). Mxa was calculated for 90% and THRR for 50% of participants. Median study time was 127.5 minutes and feedback (n = 6) highlighted the perceived acceptability of the study. Conclusions This pilot study has demonstrated a feasible and reproducible assessment of PCS and CA metrics (non-invasively) in a real-world setting. By scaling this methodology, we hope to test whether CA changes are correlated with symptomatic PCS in patients post-TBI. </jats:sec

THE EFFECT OF REPETITIVE HEAD IMPACT EXPOSURE ON CEREBROVASCULAR FUNCTION IN HIGH SCHOOL ATHLETES

Recent data suggest subconcussive head impacts may contribute to short- and long-term neurophysiological deficits. It is important to characterize the neurophysiological effects of these impacts early in the athletic career. The purpose of this study was to determine how subconcussive head impact exposure in high school collision sport student-athletes influenced cerebrovascular function (as measured using transcranial Doppler). Transcranial Doppler was used to assess: 1) resting middle (MCA) and posterior cerebral arteries (PCA), 2) cerebrovascular reactivity (CVR) via breath-holding index, vasomotor reactivity response (VMRr) and overall MCA response curve, and 3) neurovascular coupling (NVC) via NVC response magnitude and overall PCA response curve. Fifty-three high school-aged athletes (age=15.8±1.2yrs, height=175.8±8.1cm, mass=69.4±13.5kg) were recruited into two groups based on sport participation (collision vs. non-collision sport). Prior to the start of their respective seasons, all participants completed a preseason cerebrovascular function assessment using transcranial Doppler. Following a 4- to 5-month window (median=113 days, IQR=23 days), 48 athletes (age=16.0±1.2yrs, height=175.5±8.1cm, mass=68.6± 4.0kg) repeated the cerebrovascular assessment. At pre-season testing, there were no group differences in resting MCA (t50=1.70, p=0.10) or PCA velocities (t50=1.70, p=0.10), CVR as measured by breath-holding index (BHI) (t50=0.68, p=0.50), vasomotor reactivity response (VMRr) (t50=1.70, p=0.10), and overall MCA response curve during breath-holding (F1,2594=0.20, p=0.66) or hyperventilation (F1,2594=0.00, p=0.99), or NVC as measured by NVC response magnitude during the reading task (t48=-0.91, p=0.37) or the visual search task (t49=0.50, p=0.62), and overall PCA response curve during the reading task (F1,1448=0.82, p=0.36) or the visual search task (F1,1448=0.08, p=0.78). At post-season testing, there were significant group differences in pre- to post season BHI changes (t44=-2.21, p=0.03) and overall PCA response curve to the reading task (F1,2710=101.54, p0.05). Though the clinical meaningfulness of our results are still unclear, our study demonstrates that CVR and NVC assessments may be sensitive to the dynamic cerebrovascular changes occurring in adolescent athletes. Future research should continue to assess these outcomes following both subconcussive head impact exposure and throughout the recovery trajectory following concussion.Doctor of Philosoph

Robotic Semi-Automated Transcranial Doppler Assessment of Cerebrovascular Autoregulation in Post-Concussion Syndrome: Methodological Considerations.

Post-concussion syndrome (PCS) refers to a constellation of physical, cognitive, and emotional symptoms after traumatic brain injury (TBI). Despite its incidence and impact, the underlying mechanisms of PCS are unclear. We hypothesized that impaired cerebral autoregulation (CA) is a contributor. In this article, we present our protocol for non-invasively assessing CA in patients with TBI and PCS in a real-world clinical setting. A prospective, observational study was integrated into outpatient clinics at a tertiary neurosurgical center. Data points included: demographics, symptom profile (Post-Concussion Symptom Scale [PCSS]) and neuropsychological assessment (Cambridge Neuropsychological Test Automated-Battery [CANTAB]). Cerebrovascular metrics (nMxa co-efficient and the transient hyperaemic-response ratio [THRR]) were collected using transcranial Doppler (TCD), finger plethysmography, and bespoke software (ICM+). Twelve participants were initially recruited but 2 were excluded after unsuccessful insonation of the middle cerebral artery (MCA); 10 participants (5 patients with TBI, 5 healthy controls) were included in the analysis (median age 26.5 years, male to female ratio: 7:3). Median PCSS scores were 6/126 for the TBI patient sub-groups. Median CANTAB percentiles were 78 (healthy controls) and 25 (TBI). nMxa was calculated for 90% of included patients, whereas THRR was calculated for 50%. Median study time was 127.5 min and feedback (n = 6) highlighted the perceived acceptability of the study. This pilot study has demonstrated a reproducible assessment of PCS and CA metrics (non-invasively) in a real-world setting. This protocol is feasible and is acceptable to participants. By scaling this methodology, we hope to test whether CA changes are correlated with symptomatic PCS in patients post-TBI

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

Brain Injury

The present two volume book "Brain Injury" is distinctive in its presentation and includes a wealth of updated information on many aspects in the field of brain injury. The Book is devoted to the pathogenesis of brain injury, concepts in cerebral blood flow and metabolism, investigative approaches and monitoring of brain injured, different protective mechanisms and recovery and management approach to these individuals, functional and endocrine aspects of brain injuries, approaches to rehabilitation of brain injured and preventive aspects of traumatic brain injuries. The collective contribution from experts in brain injury research area would be successfully conveyed to the readers and readers will find this book to be a valuable guide to further develop their understanding about brain injury

The acute effect of heading on neurovascular coupling, optic nerve sheath diameter and memory recall in women footballers

Purpose: Retired male footballers are at 3.5 times greater risk of neurodegenerative disease, with repeated heading suggested to contribute to the increased risk. Currently, no such cohort data exist in women players. However, the women’s game is growing, so studies are needed to understand whether heading acutely alters outcomes potentially linked to neurodegenerative disease in this group. Alterations in neurovascular coupling (NVC) may precede the cognitive impairment associated with neurological disease, and evidence suggests that NVC is acutely altered following heading in men. Increased intracranial pressure (ICP) is linked with unfavourable patient outcomes following mild traumatic brain injury. This study assessed whether exposure to a realistic number of football headers acutely influenced NVC, ICP and cognitive function in women footballers. Methods: 19 women footballers completed a heading trial consisting of 6 headers at 40 ± 5 km/h, evenly spaced across an hour, and a time-matched seated control trial. Trials were performed on separate days, spaced a least 7 days apart. The posterior cerebral artery blood velocity response to a visual search task was measured via transcranial Doppler ultrasonography and used to quantify NVC. ICP was evaluated by measuring the optic nerve sheath diameter (ONSD). Finally, cognitive performance was determined using a modified version of the international shopping list test. Each outcome was assessed before and after the heading and control trials. Results: No significant time by trial interaction was present for any metric of NVC (P>0.14, ηp2<0.16), ONSD (P= 0.65, ηp2 = 0.01) or cognitive function (P = 0.053, ηp2 = 0.19). Conclusion: Our data suggests that NVC, ICP and cognitive function is not altered following six headers in women footballers. Future studies should examine how these outcomes are effected by repeated exposure across a season and career