A Multifaceted Approach to Interpreting Reaction Time Deficits After Adolescent Concussion

Abstract

Context: Reaction time (RT) is a critical element of return to participation (RTP), and impairments have been linked to subsequent injury after a concussion. Current RT assessments have limitations in clinical feasibility and in the identification of subtle deficits after concussion symptom resolution.

Objectives: To examine the utility of RT measurements (clinical drop stick, simple stimulus-response, single-task Stroop, and dual-task Stroop) to differentiate between adolescents with concussion and uninjured control individuals at initial assessment and RTP.

Design: Prospective cohort study.

Setting: A pediatric sports medicine center associated with a regional tertiary care hospital.

Patients or other participants: Twenty-seven adolescents with a concussion (mean age = 14.8 ± 2.1 years; 52% female; tested 7.0 ± 3.3 days postconcussion) and 21 uninjured control individuals (mean age = 15.5 ± 1.6 years; 48% female).

Main outcome measure(s): Participants completed the Post-Concussion Symptoms Inventory (PCSI) and a battery of RT tests: clinical drop stick, simple stimulus-response, single-task Stroop, and dual-task Stroop.

Results: The concussion group demonstrated slower clinical drop stick (β = 58.8; 95% CI = 29.2, 88.3; P < .001) and dual-task Stroop (β = 464.2; 95% CI = 318.4, 610.0; P < .001) RT measures at the initial assessment than the uninjured control group. At 1-month follow up, the concussion group displayed slower clinical drop stick (238.9 ± 25.9 versus 188.1 ± 21.7 milliseconds; P < .001; d = 2.10), single-task Stroop (1527.8 ± 204.5 versus 1319.8 ± 133.5 milliseconds; P = .001; d = 1.20), and dual-task Stroop (1549.9 ± 264.7 versus 1341.5 ± 114.7 milliseconds; P = .002; d = 1.04) RT than the control group, respectively, while symptom severity was similar between groups (7.4 ± 11.2 versus 5.3 ± 6.5; P = .44; d = 0.24). Classification accuracy and area under the curve (AUC) values were highest for the clinical drop stick (85.1% accuracy, AUC = 0.86, P < .001) and dual-task Stroop (87.2% accuracy, AUC = 0.92, P < .002) RT variables at initial evaluation.

Conclusions: Adolescents recovering from concussion may have initial RT deficits that persist despite symptom recovery. The clinical drop stick and dual-task Stroop RT measures demonstrated high clinical utility given high classification accuracy, sensitivity, and specificity to detect postconcussion RT deficits and may be considered for initial and RTP assessment.

Keywords: adolescent athletes; mild traumatic brain injuries; return to participation; sports.

Figure 1

Representative photograph of the clinical drop stick reaction time (A) test setup and (B) starting position. The image emphasizes participant hand placement in an “L” versus a “C” for the starting position.

Figure 2

Reaction time performance characteristics and statistical test results between the concussion and control groups across the 4 methods. Violin plots are presented as median (center dot) and interquartile range (IQR; box around the median). The shaded area represents the probability density of data at each level of the scale, smoothed using a kernel density estimator. Abbreviation: AUC, area under the curve.