The use Of Pupillary Light Reflex in Concussed Athletes

Abstract

Background:Despite advancements, concussion diagnosis remains reliant on subjective symptom report and clinical assessments. Visual deficits and autonomic dysfunction have been described following concussion. Testing of the pupillary light reflex (PLR) is a simple, portable, non-invasive, and objective means of quantifying pupillary function.Purpose:The aim of this study was to objectively evaluate pupillary responses to a light stimulus in concussed adolescent athletes and to determine whether clinical assessments correlated with PLR responses after a diagnosed concussion when compared to pre-injury responses.Methods:In this prospective cohort study, PLR and clinical measures [PCSI and/or SCAT symptom scales, near point of convergence (NPC) and accommodation amplitude (AA) of both eyes] were assessed in 93 (45 female), non-concussed adolescent athletes (ages 14-18) during their pre-season. PLR was obtained in response to a brief white light stimulus using a hand-held pupillometer. During each assessment, three monocular trials were performed in each eye alternatively, with subsequent averaged responses for each eye. Seven athletes (ages 14-17) sustained a concussion and had post-injury assessments of PLR and clinical measures completed longitudinally through recovery.Results:All seven concussed athletes completed PLR and clinical assessments at least once post-injury (mean initial day of evaluation = 6 days post injury). Six out of the seven concussed athletes demonstrated an increase in steady state diameter of 24% (median 18%), minimum pupil diameter of 17% (median 11%) and a maximum constriction velocity of 28% (median 33%) following concussion which decreased over the course of recovery, returning to pre-injury or below pre-injury measurements. Six of seven of the concussed athletes completed NPC and AA assessments at both pre-season and post-injury timepoints. In contrast to the PLR findings, both NPC and AA measures were normal at post-injury assessments. Reported symptom scores improved throughout recovery, correlating with PLR response recovery, with both returning to pre-injury measurements.Conclusion:Pupil responsivity was found to be significantly enhanced after concussion compared to pre-injury measurements, waning over time during recovery, following a similar trajectory as symptom burden. NPC and AA, which have autonomic contributions and are clinical measures, were normal pre- and post-injury and did not differentiate the concussed state from the uninjured state in our series. Our preliminary results demonstrate that dynamic PLR responses may detect acute autonomic deficits that are not evident via clinical assessments. Further investigation of its potential utility as sensitive and objective biomarker in concussion diagnosis, management and sports clearance is warranted.