A-101 Reaction Time and Reaction Time Variability with the Brain Gauge Somatosensory Device in Service Members with and without Acute Concussion

Abstract

Abstract Objective Research has demonstrated reaction time variability (RTV) as a potentially sensitive metric for post-concussion assessments. The Brain Gauge Clinical Metrics battery (BG) device uses tactile sensory stimulation to elicit a response, increasing accuracy to <1 msec versus 30–100 msec in visually-based reaction time (RT) measures. We sought to determine if BG RTV could adequately identify individuals with acute concussion. Methods We administered BG to 98 healthy control service members (SMs) and 64 SMs within 7 days of a medically diagnosed concussion. The battery includes simple RT and repeated simple RT subtests with RT variability (RTV) for each test calculated as the sd of mean RT for each participant. We used t-tests and gamma regression to compare group RT and RTV means. “Cutoffs” based on percentiles of the control group RTV distribution were calculated and the proportion of each group falling below these cutoffs was determined. Results There were statistically significant differences with large effect sizes between groups across all four metrics. The proportion of participants in the concussion group falling below the cutoffs was higher than among controls, with large effect sizes. T-tests and gamma regression showed that group mean RT and RTV differed significantly under multiple distributional assumptions. Conclusions Both RT and RTV using the BG somatosensory device demonstrated the ability to discriminate between healthy control SMs and SMs with acute concussion. This is further evidence that RTV is a sensitive measure for acute concussion and the use of a tactile sensory stimulus may represent an improvement over a visual stimulus.