Cerebral Haemodynamic Assessment Following Sport-related Concussion (Mild Traumatic Brain Injury) in Youth and Amateur Rugby Union Players.

Background: Using functional near-infrared spectroscopy (fNIRS) as an objective diagnostic tool, we aimed to (1) compare fNIRS measurements in adult and youth male rugby players against controls over a playing season, and 2) document the fNIRS changes that occur in concussed rugby players during the England Rugby Football Union Graduated Return-To-Play programme (GRTP). Sixty-seven participants (rugby = 41 (26 adults: 27.5 ± 4.4 years; 15 youth: 16.5 ± 0.6 years; control = 26 (11 adult: 30.5 ± 5.2 years; 15 youth: 16.9 ± 0.4 years) completed fNIRS assessments at pre, mid and end-season. Eight players (five youth, three adult) sustained concussions, and completed fNIRS and the Graded Symptom Checklist from the Sport Concussion Assessment Tool version 5 (SCAT5) assessment throughout the GRTP period. Mixed linear models were utilised to assess the effect of group and time on fNIRS measures of oxyhaemoglobin (∆O₂Hb) and deoxyhaemoglobin (∆HHb) during performance tasks. Typical Error (TE) i.e., normal biological fluctuation and measurement error, was calculated to identify 'cut-off' thresholds for identifying effects of concussion.

Results: There were significant differences in fNIRS indices over time in adult and youth groups (p < 0.05) but no significant differences between rugby and control groups (p > 0.05). Seven out of eight (87.5%) concussed players showed changes greater than TE during the GRTP period for both ∆O₂Hb and ∆HHb during performance tasks and these players' ∆O₂Hb profiles had not returned to within 'normal' levels within the GRTP period. All players' symptom severity and number returned to normal within the GRTP period.

Conclusion: Current GRTP protocols alone are problematic and there is a need for a more individualised approach to concussion management, utilising objective biomarker tools such as fNIRS.