Quantitative pupillometry as a potential biomarker in early concussion assessment

Abstract

Background

There are limited objective methods when it comes to identifying and diagnosing concussion. Pupil assessment is performed routinely as a standard-of-care following traumatic brain injury (TBI). Unlike the highly subjective and limited reliability of pupil assessment using penlights and flashlights, Quantitative pupillometry (QP) is an established, valid, and reliable method of pupillary assessment. This study aims to investigate the use of QP values in concussion evaluation.

Methods

This observational study analyzed data collected by the North Texas Concussion Registry (ConTex). ConTex enrolls subjects who are >5-years of age and clinically diagnosed with concussion. Subjects are excluded if they had moderate or severe traumatic brain injury, spinal cord injury with an American Spinal Injury Association score of C or worse, or if the injury occurred > 6 months from enrollment. Data included demographics, medical history, time since concussion, the Sport Concussion Assessment Tool (SCAT5©) post-concussion symptom scale (PCSS), and QP assessment using the PLR3000® (Neuroptics Inc.) hand-held pupillometer. This study identified all subjects clinically diagnosed with concussion who had completed QP assessment, totaling 162. We created tertiles to describe the lowest (0–20), middle (21–43), and the highest (44–113) symptom score groupings to examine QP data.

Results

Of 162 subjects, 88 were female (54.3%), with a mean age of 15.8 (SD=6.9) years. Most (49.4%) occurrences were sport-related injuries. The mean time since injury was 21 (SD=28.6) days. The mean SCAT5 PCSS score was 37.3 (SD=25.6). A significant difference within average and maximum constriction velocities (p=.041 and 0.034, respectively) was found between subjects seen early (<2weeks) versus late (>2weeks) after injury. Pupillometry values were statistically different across SCAT5 PCSS tertiles for anisocoria after light exposure (p=.046).

Conclusions

This exploratory study is among the first to show that certain QP values — latency of constriction, constriction velocity, and average dilation velocity — may be useful in providing objective metrics when evaluating more symptomatic concussion.