Blink Reflex Parameters are Affected Acutely after Sport-related Concussion in Military Cadets

Objective: A pilot study reported sport-related concussion (SRC) affects the stimulated blink reflex response in collegiate male cadets, demonstrating hyper-reflexive blinks, increased time between closure of the ipsilateral and contralateral eyelid, and increased number of eyelid oscillations post-blink. The purpose of this study was to validate our earlier findings in a larger and diverse sample. Materials and Methods: Prospective cohort study at a military cadet college enrolled participants between 2018 and 2022. Participants blink reflex was assessed at preseason physicals and then again within 48 hours of concussive head injury using the EyeStat. Thirty-two cadets with SRC (mean age 20.1 years, 78% male) and 6 cadets with a repeat SRC during the enrollment period (mean age 21.7 years, 83% male) were assessed, a mean of 1 day post injury, and included in the analysis. Blink reflex parameters included latency, differential latency, eyelid velocity, excursion, oscillations, and delta 30. Results: In the primary concussion group, SRC significantly reduced ipsilateral latency (2.93 [0.44, 5.42] ms, P = .022) and increased differential latency (1.46 [0.24, 2.69] ms, P = .020). No significant difference was observed for oscillations (P = .167). Although underpowered, our exploratory analysis suggests that this finding was not affected by participant age or sex. In repeat concussions, ipsilateral latency had a similar trend, but differential latency did not. Conclusions: The blink reflex is affected after SRC, and its assessment may provide objective data to aid diagnosis. However, additional research is warranted to assess how blink reflex parameters change after subsequent concussions.