Sports-related suspected head injury is associated with otolith-mediated ocular misalignment

Introduction Annually, approximately 1.6–3.8 million sport-related mild traumatic brain injuries (mTBI) occur in the United States. Symptoms commonly include dizziness, imbalance, blurred vision, motion sensitivity, and return-to-play difficulty. These symptoms indicate vestibular dysfunction that may prolong recovery. Unfortunately, most of these injuries lack formal diagnosis, in part due to the absence of field-ready devices that offer valid and efficient objective physiological assessment. We developed portable perceptual measures of ocular alignment, Vertical Alignment Nulling (VAN) and Torsional Alignment Nulling (TAN), to assess the otolith-mediated ocular tilt reaction. These tasks quantify perceived misalignment between the two eyes and provide separate estimates of vertical and torsional alignment. The purpose of this study was to investigate the ability of VAN and TAN to identify recreational athletes who sustained symptoms after a suspected, acute head injury following rugby play. Methods Seventy-seven ( n = 38 females) rugby athletes aged 18–63 years old participated in this study ( n = 29 suspected head injury, n = 48 uninjured controls). All participants completed the VAN and TAN tests, and a subset of n = 67 athletes ( n = 25 suspected head injury, n = 42 controls) completed the Sport Concussion Assessment Tool - 3rd Edition (SCAT3). Results Compared with uninjured control athletes, rugby athletes with suspected head injury exhibited significantly higher misalignment on the TAN test [Median (IQR): 0.795 (0.450–0.995) vs. 0.410 (0.212–0.679); p = 0.005], suggesting abnormal perception in the roll plane. In contrast, VAN scores showed no significant difference between groups [Median (IQR): 0.038 (0.021–0.069) vs. 0.046 (0.026–0.101); p = 0.592]. Injured athletes demonstrated significantly elevated scores in headache ( p < 0.001), dizziness ( p = 0.001), and confusion ( p = 0.002). Across athletes evaluated with the SCAT3, elevated TAN scores correlated selectively with vestibular symptoms (dizziness, balance impairment; rho = 0.27–0.30, p < 0.05) and cognitive impairment (confusion, memory recall), but did not show a significant correlation with headache (rho = 0.185, p = 0.134). Exploratory ROC analysis of TAN yielded an AUC of 0.693 (sensitivity: 62.1%, specificity: 75.0%). Conclusion Our results suggest the on-field testing of TAN may serve as an objective, adjunctive biomarker of vestibular perceptual impairment following acute suspected head injury.