Automated Pupillometry Following Sport-Related Concussion in National Level Rugby League Athletes

Background Sport-related concussion accounts for 9% of all sporting injuries. Within elite rugby league athletes, 17% will suffer a concussion in a three-year period. Although there is increasing knowledge of incidence and risk of SRC in rugby league, gaps regarding the optimal diagnostic and return to play protocols remain. The National Rugby League requires teams to follow a strict concussion protocol, the Head Injury Assessment, which incorporates the Sport Concussion Assessment Tool (3rd ed). The effectiveness of the Sport Concussion Assessment Tool 3rd Edition protocol, along with existing cognitive assessment tools to diagnose and predict a return to play have been disputed, which has highlighted the need for objective biomarkers. The pupil light reflex is an autonomic nervous system function that occurs when there is a light stimulus upon the pupil. Emerging evidence has been suggested that pupil light reflex may be useful as a potential objective physiological biomarker for neuroanatomical pathway disruption. The aim of the present study was to determine whether there was a change in the pupil light reflex and anisocoria (pupil asymmetry) following a sport-related concussion in national level rugby league athletes. Aims and Objectives The study aimed to determine whether a change in the PLR and anisocoria is detectable following an acute sport-related concussion in national level rugby league athletes. To achieve this, comparisons of the PLR, anisocoria, variability and time-frame variations between concussed and non-concussed athletes were undertaken. Methods Fifty-five male volunteer athletes (age: 23 ± 4.5 years) were recruited from a local National Rugby League club. Eight pupil light reflex parameters were measured via a handheld monocular pupillometer during the rugby league pre-season. During the 2017 National Rugby League season, the pupil light reflex of nine athletes without a sport-related concussion diagnosis was monitored. Sixteen athletes were diagnosed with sport-related concussion and the pupil light reflex was recorded over a ten-day time frame, and broken down to three periods, 0 – 3 days, 4 – 6 days and 7 – 10 days, to measure recovery. Absolute change scores between the pupil light reflex parameter values were calculated for each athlete. Independent t-tests and Mann-Whitney U tests were used to test the study objectives. Results The neurological pupil index was significantly lower in the sport-related concussion group compared to the no-sport-related concussion (p = 0.0002). There was no statistical difference in the additional seven pupil light reflex parameters between the two groups. Given the variability within sport-related concussion and no-sport-related concussion athletes, absolute change scores were calculated to determine difference between groups. The absolute change score for resting pupil diameter (p = 0.001) and minimum pupil diameter (p 0.05). Conclusion The pupil light reflex has previously been observed to have a statistical difference between control groups and mild traumatic brain injury groups. The present study found scientifically significant changes in the pupil light reflex following acute sport-related concussion in national level rugby league athletes compared to non-concussed athletes. The neurological pupil index for athletes with sport-related concussion were found to be statistically smaller than non-concussed athletes. Similar to previous research investigating mild traumatic brain injuries, the resting and minimum pupil diameter were found to be significantly different between a sport-related concussion group and non-concussion group. Results of the present study suggests the pupil light reflex may provide an objective physiological biomarker for diagnosis and recovery monitoring of an acute sport-related concussion in national level rugby league athletes. The change in the pupil light reflex observed in the present study suggest the potential application within the diagnosis and recovery monitoring of an acute sport-related concussion in national level rugby league athletes.