THE UTILITY OF PUPILLARY LIGHT REFLEX AS AN OBJECTIVE BIOMARKER OF ACUTE CONCUSSION IN THE ADOLESCENT ATHLETE

Abstract

Purpose: Visual problems and autonomic dysfunction have been well recognized following pediatric concussion. Testing of the pupillary light reflex (PLR) is a simple, non-invasive, and objective approach to examine the autonomic nervous system by accessing the brain pathways. The aim of this study was to objectively evaluate adolescent pupillary responses to a light stimulus after a physician-diagnosed concussion. Method(s): In this on-going prospective cohort study, PLR was assessed in xxx (number) of athletes in the pre-season. Within this cohort 6 athletes sustained a concussion during their sports season and had post-injury assessments of PLR. The PLR was obtained in response to a brief step-input (0.8 seconds) white light stimulus, group of six adolescent athletes, ages (14+/- 17 years) prior to the beginning of their sport season and in a longitudinal manner after concussion. PLR was quantified using the Neuroptics model PLR-300, hand-held pupilometer (stimulus recording duration = 5 seconds, light intensity = 150. Pre-set and automated devicegenerated parameters used for analysis include the minimum and maximum pupil diameter, response amplitude and latency, mean constriction and dilation velocities and the maximum (peak) constriction velocity of the eye in response to a light stimulus. During each visit, three monocular trials were performed in each eye alternatively, and the responses for each eye were subsequently averaged. Result(s): Five out of the six concussed adolescents showed response enhancement (25% or greater) following concussion, which decreased during the recovery process (days to weeks post-injury) to pre-injury or below initial pre-injury baseline measurements. Pupillary responsivity was found to be significantly enhanced after concussion compared to baseline measurements, waning over time. Maximum constriction velocity better highlighted the enhancement compared to the baseline pupil diameter. Conclusion(s): Preliminary findings suggest autonomic dysfunction related to acute concussion, as identified by changes in the PLR, which wanes over time during recovery. Assessment of dynamic PLR responses has the potential utility as an objective biomarker to aid in concussion diagnosis on the sidelines or in the office, allowing physicians to quantify various static and dynamic parameters of the autonomic nervous system under parasympathetic and sympathetic control after concussion.