Novel brain biometrics could help inform whether an athlete is ready to return to play following a concussion, according to new research from the University of SA.
Conducted in partnership with the University of California San Francisco (UCFC), researchers found that changes in micromovements of the brain – termed ‘headpulses’ – could detect the lasting impacts of a concussion.
Using a custom-designed headset to evaluate headpulse biometrics among 101 amateur male and female Australian Rules Football players in SA, the team identified brain abnormalities in 81% of players inflicted by concussion, signalling sustained injury beyond expected recovery times.
The headpulse comprised forces aimed toward the head following each cardiac contraction in the 10 to 15 milli-g (gravitational force unit) range and a non-invasive battery-powered device of highly sensitive accelerometers attached to a headband, placed on participants’ heads coronally, recorded the signal.
The team found that headpulse alterations lasted 14 days beyond concussion symptoms and were exacerbated by return-to-play or unsupervised physical activity, and UniSA Professor of Exercise Science, Kevin Norton, explained that headpulse measures could complement current return-to-play protocols.
“Traumatic brain injury inflicts more than 60 million people every year, with a third of these being sports related. Another concussion during recovery can be neurologically deleterious, causing “second impact syndrome,” which in rare cases can be fatal,” Professor Norton said.
“While we know that Australia’s sports sector takes concussions seriously via considered return-to-play protocols, we also know that objective measures of concussion recovery are not fully established.”
Australian Football concussion recovery protocols require 24 to 48 hours of strict physical and cognitive rest, followed by graded individual then team training, provided there is no symptom exacerbation; the earliest allowed return-to-play after protocol completion and medical clearance is 12 days after a concussion.
“We have previously showed that frequency domain analysis of headpulse supports the diagnosis of concussion and recovery, and demonstrated headpulse abnormalities in moderate to severe TBI, large vessel stroke, cerebral vasospasm, and cardiac arrest,” Professor Norton explained.
“We have now discovered that almost all players who received a concussion had a ‘disconnect’ between their symptoms and the headpulse, such that even when the players said they felt good, the headpulse still showed evidence of brain injury.”
A total of 762 athletes across 9 clubs provided written consent at season start, with active, concussion free, athlete controls recruited from one club. Concussed male individuals (the A1 cohort) were recruited across all clubs as de novo concussion occurred between August 5, 2021, and September 10, 2021. The A2 cohort (male and female athletes) was recruited between May 5, 2022, and September 3, 2022.
Research coordinators attended games and were alerted to players with a concussion. An attempt was made to record from concussed athletes early, and all recordings except 1 were conducted within one hour of the index concussive event. Coordinators travelled to individuals’ homes every one to three days for a month after injury to obtain additional recordings, with the A2 cohort invited to wear a wristband accelerometer to document physical activity.
While most players felt that they’d recovered 10-14 days after their injury, the findings showed that some players took up to four weeks to recover and return to normal headpulse patterns.
“Of 762 consented athletes, 59 control and 43 concussed individuals had headpulse measurements, yielding 44 total concussions from 101 total individuals and overall, headpulse analysis detected 9% of concussions on day 0, 50% by day two, and 90% by day 14,” Professor Norton said.
“Of 32 participants with longitudinal recordings, 26 had adapted digital Neurobehavioral Symptom Inventory (NSI) values return to zero within 30 days, and of the 81% of athletes that had symptomatic duration under one month, 50% returned to a zero NSI score by day seven.
“Compared with symptom resolution, only 57% of athletes demonstrated biometric resolution by day 30 with 50% achieving this by day 21, 14 days later than NSI improvement.”
The digital biomarker was derived from cranial accelerometry, which draws on the principles of ballistocardiography (BCG), first recognized in the 19th century. BCG can provide information about the overall performance of the circulatory system by measuring the mass of the circulating blood and the heart during the cardiac cycle, with the body’s shifting centre of mass generating the BCG waveform.
“While ballistocardiography measures whole body forces produced by cardiac contraction, our study focuses on measuring cardiac output forces directed toward the head,” Professor Norton said.
“Highly sensitive accelerometers within our headset noninvasively measure cardiac forces sustained by the head. We call the resulting waveform the “headpulse” – a measure of brain ‘wobble’ aligned with each heartbeat – that can be assessed for any changes in frequency resulting from a concussion.
“These repeated motions happen due to the rapid acceleration of blood when it is ejected and moved in the great vessels of the body during periods diastole and systole, respectively.”