IMPAIRED EYE TRACKING IS ASSOCIATED WITH SYMPTOMS BUT NOT DYNAMIC POSTURAL CONTROL IN ADOLESCENTS FOLLOWING CONCUSSION

Abstract

Background:Visual impairments are common following concussion, and vision tests are recommended as part of a comprehensive clinical concussion evaluation. Persistent symptoms from vision disturbances can delay recovery and earlier detection may reduce symptom burden. Further, while gait-related deficits were reported among adolescents with abnormal near point of convergence following concussion, further research is needed to understand gait performance among those with impaired eye tracking abilities.Hypothesis/Purpose:Our purposes were to: 1) examine the relationship between self-reported symptoms and concussion-related visual impairments; and 2) compare single-task and dual-task gait speed between concussed adolescents with and without abnormal visual tracking abilities, to healthy controls.Methods:Thirty concussed participants and thirty healthy controls (Table 1) completed an eye tracking assessment during which they watched a brief (220s) video clip. The video clip moved in a clockwise direction around the screen while pupil positions were measured with an objective eye tracker to create a box trajectory of each eye movement. The eye tracking dependent variable (BOX score) was a binary classifier with <10 being classified as normal and ≥10 abnormal. Symptoms were collected using the Post-Concussion Symptom Scale (PCSS), and gait speed was measured with three triaxial accelerometers placed on the dorsal side of each foot and L5. Participants walked along a 10-m walkway, turned, and returned to the starting point at a self-selected pace. During dual-task trials, participants simultaneously answered cognitive questions (spelling backwards, serial 6s or 7s, reciting months backwards) while walking. We conducted a linear regression to examine the relationship between PCSS and BOX scores and a two-way mixed effects analysis of variance followed by a Tukey post-hoc to examine the effect of group (abnormal BOX, normal BOX, and healthy control) on single and dual-task gait speed.Results:There was a significant association between total PCSS score and BOX score (Figure 1). There were no significant differences in single-task or dual-task gait speed between the groups. (Figure 2)Conclusion:There appears to be a positive relationship between total PCSS score and BOX score, and the concussed group with impaired eye tracking reported the highest symptom scores. However, the sample size of the impaired group was small, which warrants future research. While not statistically significant, the slower single and dual-task gait speeds in those with abnormal BOX scores may still be clinically relevant, as gait-related impairments have been shown to persist far beyond clinical recovery.Table 1.Mean ± standard deviations for demographic characteristics. *There were significant differences between the groups for total PCSS score and BOX score. Concussion:Abnormal BOX(n=9)Concussion:Normal BOX(n=21)HealthyControls(n=30)p-valueAge (y)14.4 ± 2.713.9 ± 2.014.2 ± 2.20.79Height (cm)165.8 ± 13.0158.5 ± 13.1159.9 ± 12.20.34Mass (kg)60.4 ± 16.354.3 ± 15.352.3 ± 14.80.39PCSS Score*51.1 ± 16.331.4 ± 19.33.7 ± 8.6<0.001BOX Score*15.9 ± 3.64.7 ± 3.07.8 ± 5.6<0.001Figure 1.There was a significant association between total PCSS scores and BOX scores (β=0.085, p=0.014, 95% CI= 0.018-0.151).Figure 2.There was not a significant difference in single-task (Abnormal: 1.00 ± 0.14 m/s, Normal: 1.11 ± 0.21 m/s, Healthy: 1.14 ± 0.18 m/s , p=0.08) or dual-task (Abnormal: 0.77 ± 0.15 m/s, Normal: 0.84 ± 0.21 m/s, Healthy: 0.90 ± 0.18 m/s, p=0.16) gait speed between the groups. The error bars represent 95% confidence intervals.