Acoustic Startle Reflex In Adolescents With And Without A Concussion History: A Preliminary Investigation

Abstract

Due to its narrow structure and sensitivity to rotational forces, the brainstem is particularly vulnerable to injury from head impacts. The acoustic startle reflex is a brainstem-mediated, cross-species reflex that may serve as a sensitive marker for concussion-related brainstem injury. PURPOSE: To examine the acoustic startle reflex in adolescent athletes with a concussion history compared to healthy controls. METHODS: We conducted a cross-sectional study on twenty adolescent athletes with (n = 13, age: 14.8 ± 2.0 years; 46% female) and without (n = 7; age: 13.9 ± 3.1 years; 43% female) a concussion history. Acoustic startle probes were administered to participants through noise-canceling headphones while sitting upright with eyes fixed on a target. The eye blink component of the startle reflex was recorded via electromyography activity of the orbicularis oculi muscle using electrodes placed under the right eye. Measurement sessions began with a one-minute acclimatization period of white noise, followed by twelve 103 decibel acoustic startle probes approximately 50 milliseconds in duration delivered 15-25 seconds apart. The primary dependent variable was mean startle magnitude (μV), and group was the primary independent variable. We analyzed mean startle magnitude with group (concussion history vs healthy control) as a between subjects factor and participant age as a covariate. RESULTS: Mean startle magnitude was markedly lower in adolescents with a concussion history (70.8 ± 25.6 μV) compared to healthy controls (164.1 ± 35.0 μV, t = 2.15, p = 0.047). CONCLUSIONS: These preliminary results provide novel evidence for a distinct attenuation of acoustic startle magnitude in adolescent athletes with a concussion history. This suggests potential for use of the startle reflex to detect lingering physiological dysfunction beyond traditional clinical assessment of recovery. Supported by Thrasher Research Fund Early Career Award