Stimulated Blink Reflex Abnormalities Before And After Sport-related Concussion And Association With Self-reported Symptoms

PURPOSE: Athletes with sport-related concussion (SRC) have blink reflex abnormalities, and can report combinations of physical, cognitive, fatigue or mood-related symptoms after injury. This study compares blink reflex before and after injury and identifies associations with self-reported symptoms. METHODS: Blink reflex (EyeStat, BlinkCNS) and Post-Concussion Symptom Scale (max = 126) were assessed preseason and within 2 days of SRC. Clustering identified High (HS) and Low (LS) symptom groups. Blink reflex parameters: time to ipsilateral blink (latency), contralateral blink (differential latency), initial velocity, time to open, time to close, number of oscillations, and distance traveled (excursion). RESULTS: Differential latency increased (baseline: 4.28 ± 1.8 vs post-injury: 5.33 ± 3.0 ms, p = 0.047) and time to close decreased (34.30 ± 5.6 vs 32.38 ± 4.3 ms, p = 0.022) after injury on paired t-test, and there was a trend for significance for latency (p = 0.094) and oscillations (p = 0.074). HS (n = 15, 87% male, 20.8 ± 1.5 years, symptoms = 43.3 ± 11.4) had slower initial velocity (4.23 ± 0.7 vs 5.16 ± 1.0 pixel/s, p = 0.002) than LS (n = 23, 74% male, 20.1 ± 1.4 years, symptoms = 13.0 ± 6.3), and there was a trend for significance for excursions (p = 0.081). Physical symptoms correlated with latency (rho = -0.28, p = 0.026) and oscillations (rho = 0.37,p = 0.003); cognitive correlated with initial velocity (rho = -0.36, p = 0.003) and exclusions (rho = -0.38,p = 0.002); fatigue correlated with initial velocity (rho = -0.48, p < 0.001), time to close (rho = -0.26, p = 0.034) and excursion (rho = -0.49, p < 0.001). Mood correlated with differential latency (rho = 0.49, p < 0.001) and initial velocity (rho = -0.30, p = 0.014). CONCLUSIONS: The stimulated blink reflex is abnormal acutely after SRC. Increase in differential latency is suggestive that the contralateral blink reflex arch is less efficient. Decreased time to close with a trend that latency is also faster is suggestive that the blink reflex is excited. The strongest correlations were between increasing differential latency and increasing mood symptoms and decreasing excursions and increasing fatigue. Technology-assisted objective assessment using a portable blink reflexometer has the potential to aid in SRC diagnosis and validate self-reported symptoms.