Search

Objective Examine differences between the recently implemented integrated spiral (year 1) and conventional block (years 2-4) MD curriculum at University of British Columbia (UBC) with respect to knowledge of concussion diagnosis and management. Design Cross-sectional survey Setting UBC undergraduate MD program Participants An online survey was distributed to all 1152 students currently enrolled in UBC medical school. To date, 123 surveys have been returned (10.7% response rate) with 58 first year students (integrated spiral curriculum) and 65 students in years 2-4 (conventional block curriculum). Females made up 60% of responses. Interventions Online survey, hosted by FluidSurveys (Fluidware, Ottawa, ON), distributed through email. Outcome measures Questions focused on demographic data, knowledge of concussion definitions, and management considerations. Main results Majority of responses revealed both curriculums have promoted a strong understanding of concussion definition and related symptoms (84% correct response rate). Only 8.1% of participants believed that functional imaging (MRI or CT) is a mandatory assessment tool for concussions. Differences between the conventional and integrated curriculums included: understanding concussions can occur without direct impact to the head (91.4% integrated vs. 69.2% conventional: χ2(1)=43.325, p Conclusions The findings from this study reveal a number of positive signs regarding the evolution of medical education in terms of concussion diagnosis and management. The integrated curriculum is taking further steps in advancing concussion knowledge in medical education. Competing interests None.

Objective To determine the influence of a history of 3+ previous concussions on quiet stance. Design Retrospective cohort. Setting Laboratory. Participants Eighty-seven male (age range 17–22) contact-sport athletes (football and hockey) entered the study. Participants were recruited from the same sport teams and tested during the pre-season. Exclusion criteria: concussion in the prior 6 months, or history of 1 or 2 concussions. Forty-four met the inclusion criteria: thirty-one had no previous concussions, and thirteen had a history of 3+ concussions. Interventions Participants held quiet upright stance on a force plate (NDI True Impulse) with feet hip-width apart and hands on hips with eyes-open (1 min), and closed (1 min). Independent variables included condition (2) and concussion history (2). Outcome measures Root-mean-square displacement (RMSd), and mean velocity of centre-of-pressure (COP) in the anterior/posterior (AP) and medial/lateral (ML) directions. Main results Mixed ANOVA indicated a significant condition effect in ML-RMSd (p=0.015, 95% CI: 0.032–0.277) between eyes-open and eyes-closed conditions. ML mean velocity also displayed a significant condition effect (p=0.025, 95% CI: 0.025–0.358). In contrast to the effect of visual input, there was no main effect of concussion history on these metrics. Conclusions A history of 3+ concussions does not appear to result in long-term deficits controlling in quiet stance. Those ML variables were sensitive to condition and indicate that frontal plane COP movements may be more sensitive than those in the sagittal plane. These findings are important as a history of concussion does not appear to alter quiet stance balance control mechanisms. Competing interests None.

Objective To examine how sub-concussive head trauma throughout a contact-sport season affects quiet stance centre of pressure (COP) sway Design Prospective cohort Setting Laboratory Participants: Twenty-four elite male football players (age range 18–22) were recruited for the study Intervention Quiet stance data was collected at the start and at the end of the competitive season. One-minute trials were performed with eyes-open and eyes-closed on a force plate (NDI True Impulse) with feet hip-width apart and hands-on-hips. Biomechanical head-impact exposure was indexed using the xPatch (X2 Biosystems) Outcome measures COP measures: Anterior/posterior (AP) and medial/lateral (ML) root-mean-square displacement (RMSd) and mean velocity. Biomechanical head-impact data: For hits above 20g, peak linear acceleration (PLA), and peak rotational acceleration (PRAwere estimated across the competitive season. Independent variables included time (2) and condition (2) Results RM-ANOVA reveal an effect of condition (eyes-open vs eyes-closed) in AP-RMSd (p=0.035, 95% CI: 0.006, 0.159), ML-RMSd (p Conclusions In contrast to the prolonged COP alterations observed following acute concussions, there were no discernable effects of sub-concussive trauma on COP sway during quiet stance in the same population. This is an important finding as it reveals that participation in contract-sport does not impair quiet stance balance Competing interests None.

Objective To examine the effects of concussion history on an index of cerebral autoregulation in a healthy athlete population. Design Retrospective Cohort. Setting Laboratory. Participants 136 male contact sport athletes (19.1±1.4 years, 66 football, 70 hockey) were recruited; 39 presented with 0 previous concussions, 16 with 3+ previous concussions; exclusion criteria included history of concussion within 6 months. Intervention Participants completed baseline testing prior to the athletic season. Squat-stand manoeuvres at 0.05 and 0.10 Hz were used to enhance blood pressure (BP) variation. BP and cerebral blood velocity (CBV) in the middle cerebral artery were indexed non-invasively via finger photoplethysmography and transcranial Doppler ultrasound, respectively. Independent variables included sport (2) and concussion history (2). Outcomes Transfer function analysis point estimates at 0.05 and 0.10 Hz characterised the coherence (correlation), phase (synchronisation), and gain (amplitude buffer) between BP and CBV waveforms during the squat-stand manoeuvres. Results These findings suggest that, despite reductions in 0.10 Hz phase lead being reported acutely after concussion, multiple concussions do not appear to induce long-term impairments in dynamic cerebral autoregulation metrics. This is an important revelation as it indicates that the cerebrovasculature is able to adequately recover following the acutely diminished buffering capacity associated with a concussive injury Conclusions These findings suggest that, despite reductions in 0.10 Hz phase lead being reported acutely after concussion, multiple concussions do not appear to induce long-term impairments in dynamic cerebral autoregulation metrics. This is an important revelation as it indicates that the cerebrovasculature is able to adequately recover following the acutely diminished buffering capacity associated with a concussive injury Competing interests None.

Objective To examine how acute sport-related concussion influences centre of pressure (COP) sway during quiet stance Design Prospective cohort Setting Laboratory Participants Eighty-seven male contact-sport (football and hockey) athletes entered the study. Seven subjects (age range 17–22) were concussed and completed follow-up testing 72-hours, two-weeks, and one-month following the injury. Intervention One-minute eyes-open and eyes-closed quiet stance trials were performed on a force plate (NDI True Impluse) with feet hip-width apart. Force plate data and SCAT3 were collected at each time point. Outcome measures Root-mean-square COP displacement (RMSd) and mean COP velocity were quantified in the anterior/posterior (AP) and medial/lateral (ML) directions. Independent variables included condition (2) and time (4) Main results RM-ANOVA indicated a main effect of time for all outcomes: AP-RMSd (p=0.006), AP mean velocity (p=0.012), ML-RMSd (p=0.001), ML mean velocity (p=0.001). Pairwise comparisons indicated reductions at 2-weeks in AP-RMSd (0.05, 95% CI: −0.672, 0.000), and AP mean velocity (p=0.039, 95% CI: −1.275, −0.036). ML-RMSd was reduced 1 month post-concussion (p=0.021, 95% CI: −0.365, −0.034). Change scores from baseline to 72-hours were correclated between: AP-RMSd and Balance Error Scoring System (r=0.878, p=0.009), AP mean velocity and Standardised Assessment of Concussion (SAC) (r=−0.822, p=0.023), and ML mean velocity and SAC (r=−0.836, p=0.019). Conclusions Measures of COP sway during quiet stance revealed alterations in displacement and velocity that persisted up to one-month following a sports-related concussion. These COP alterations exceeded the duration of clinical recovery (median return-to-play: 14 days) indicating that clinical recovery does not equal physiological recovery. Competing interests None.

Objective To examine the effect of multiple previous concussions on heart rate variability (HRV) in contact-sport athletes. Design Retrospective Cohort. Setting Laboratory. Participants 136 male elite contact-sport (hockey and football) athletes were recruited for this study. Forty-one had no previous concussion history (Hx-), while nineteen had a history of three or more concussions (Hx+). All testing was preformed prior to the start of the competitive season Interventions HRV was assessed during 5-minutes of quiet stance, and while actively squatting at 0.10 Hz via a 3-lead electrocardiogram, using Kubios software. Independent variables included condition (rest vs active) and group (Hx+ vs Hx-) Outcome measures Time-Domain: square root of mean squared differences of successive R-R intervals (RMSSD), percentage of successive R-R intervals that differ by more than 50 milliseconds (pNN50). Frequency-Domain: total power. Main results Mixed ANOVA revealed repeated squat-stand manoeuvres challenged the autonomic system, increasing total power by 2477 milliseconds2 (95% CI: 1153–3801, p Conclusions A history of multiple sport-related concussions impairs the ability of the autonomic system to respond to an everyday stressor applied to the cardiovascular system (squatting and standing). This is an important finding, as it reveals that cumulative concussions may impart long-term impairments in the ability to accurately regulate the autonomic system. Competing interests None.

Objective To determine how a history of 3+ concussions alters elevations in cerebral blood velocity (CBV) in the posterior cerebral artery (PCA) during visual tasks. Design Retrospective Cohort. Setting Laboratory. Participants 136 male contact-sport athletes (19.1±1.4 years, 66 football, 70 hockey) were recruited; 39 presented with 0 previous concussions, 16 with 3+ previous concussions; exclusion criteria included history of concussion within 6 months. Intervention Transcranial Doppler ultrasound indexed PCA-CBV during a series of visual tasks. Participants closed their eyes (20-seconds) and, when prompted, opened their eyes to complete a visual task (40-seconds). Testing occurred prior to the start of their athletic season. The visual trial raw traces were averaged together to enhance the signal-to-noise ratio of outcome measurements. The independent variable tested was concussion history. Outcomes Eyes-closed CBV (cm/s), peak elevation in CBV after eyes-open (cm/s), relative change in CBV (%), and total activation during the first 30 seconds of the task (indexed via area under the curve-AUC) Main results Independent samples T-Tests indicated there were no effects of concussion history on any outcome: Eyes-closed CBV (p=0.950), peak CBV (p=0.903), % CBV elevation (p=0.593), and AUC (p=0.718). Conclusions A history of multiple concussions does not alter the cerebrovasculature’s ability to maintain nutrient delivery required for visual challenges in cortical areas supplied by the PCA. This is an important finding; despite the long-term neurocognitive deficits associated with a history of concussions, the transcranial Doppler assessment of neurovascular coupling appears intact for this population of younger adult contact-sport athletes. Competing interests None.

Objective To determinethe extentto which an acute sport-related concussion disrupts elevations in cerebral blood velocity (CBV) in the posterior cerebral artery (PCA) during visual tasks. Design Prospective Cohort. Setting Laboratory. Participants 136 male contact-sport athletes (19.1±1.4 years) recruited, subset of 14 participants (19±1.4 years) sustained concussions. Intervention Transcranial Doppler ultrasound was used to index CBV in the PCA during a series of visual tasks. Participants closed their eyes (20 seconds), and when prompted, opened their eyes and completed a visual task (40 seconds). Testing was completed prior to the start of their athletic season (T0), and again (if concussed) at 72-hours (T1), 2-weeks (T2), and 1-month (T3) post-injury. The raw traces from each trial were averaged to enhance the signal-to-noise ratio of the outcome measurements. Independent variable tested was time (4 points). Outcome measures Eyes-closed CBV (cm/s), peak elevation in CBV (cm/s), relative change in CBV (%) and total activation during the first 30 seconds of the task (indexed via area under the curve-AUC) Main results RM-ANOVA indicated there were no time effects forany of the outcome metrics: Eyes-closed CBV (p=0.473), peak CBV (p=0.541),% CBV elevation (p=0.603) and AUC (p=0.972). Conclusions These negative findings are important, as they indicate the PCA is able to maintain nutrient delivery required for visual challenges. Thus, neurovascular coupling is maintained despite the reported impairments in indices of cerebral autoregulation in the same population. Competing interests None.

Objective To examine how head-impact exposures affect the elevation in cerebral blood velocity (CBV) in the posterior cerebral artery (PCA) during visual tasks. Design Prospective Cohort. Setting Laboratory. Participants To date: 40 male contact-sport athletes (19.4±1.2 years) and 3 cross-country athletes (20.0±1.0 years) have completed testing (non-contact controls). Intervention Transcranial Doppler ultrasound indexed PCA CBV during visual tasks. Participants closed their eyes (20-seconds), and when prompted, opened them and completed a visual task (40-seconds). Testing occurred prior-to and upon-completion-of the competitive athletic season. Raw traces from each trial were averaged to enhance the signal-to-noise ratio of outcome measurements. Independent variable tested was time (2). Outcome Eyes-closed CBV (cm/s), peak elevation in CBV (cm/s), relative change in CBV (%) and total activation during the first 30 seconds of the task (indexed via area under the curve-AUC). Head-impact exposure was characterised in a subset of contact-sport athletes (n=29) using the xPatch (X2 Biosystems). Main results RM-ANOVA indicated the contact-sport season had no effects on any outcome metrics: Eyes-closed CBV (p=0.181), peak CBV (p=0.117),% CBV elevation (p=0.252) and AUC (p=0.366), despite experiencing cumulative peak linear accelerations of 8147.2±6215.5 g, and cumulative peak rotational accelerations of 34.5×106 ± 59.0×106 rad/?s2. Conclusions The results from this study suggest neurovascular coupling metrics are maintained throughout a contact-sport season. This indicates nutrient delivery is maintained for neurocognitive challenges despite possible impairments in cerebrovasculature’s ability to buffer blood pressure challenges associated elevations in rotational accelerations experienced during a contact-sport season. Competing interests None.

Objective Examine how the frequency-dependent relationship between blood pressure (BP) and cerebral blood velocity (CBV) is affected by acute sport-related concussion. Design Prospective Cohort. Setting Laboratory. Participants: 136 male contact-sport athletes (19.1±1.4 years) recruited, subset of 14 sustained concussions (19±1.4 years). Intervention Participants completed baseline (T0) and post-injury testing at 72-hours (T1), 2-weeks (T2), and 1-month (T3). BP was monitored via finger photoplethysmography, and transcranial Doppler ultrasound indexed CBV in the middle cerebral artery. Squat-stand manoeuvers were performed at 0.05 and 0.10Hz to enhance BP variation. RM-ANOVA independent variables included time (4) and frequency (2). Outcome measures Transfer function analysis point estimates quantified coherence (correlation), phase (synchronisation) and gain (amplitude buffer) metrics between BP and CBV waveforms. Results Significant frequency-time interactions for phase (p=0.007) and gain (p=0.049). Simple effects analysis revealed time effects for phase at 0.10 Hz, indicating reductions at T1 (95% CI: 0.033 – 0.24 rads, p=0.008) and T2 (95% CI: 0.014–0.196 rads, p=0.02) compared to T0. On average, return-to-play occurred at T2 (median 14 days). Phase reductions at T1 were correlated with Standardised Assessment of Concussion performance (r=0.659, p=0.02). Conclusions These results reveal transient post-concussion impairments in the capacity of the cerebrovasculature to buffer BP oscillations, which exceeded clinical recovery duration. Phase reductions at 0.10Hz suggest the presence of a cerebrovascular autonomic dysregulation, which could leave the brain less protected to BP surges. This key finding may help explain why the brain is more vulnerable to additional trauma during the post-injury recovery period. Competing interests None.