Does time since concussion alter the factor structure of a multidomain assessment in adolescents?

The utilization of principal component analysis (PCA) approaches to concussion is beneficial to inform the interpretation of clinical outcome data in adolescent patients. While researchers have identified factors using post-concussive symptom scales and cognitive testing, there has yet to be a PCA that incorporates vestibular or oculomotor outcomes, or that focuses exclusively on adolescents. Moreover, the role of time since injury has not been examined in relation to concussion factors in this at-risk population. PCA methods were applied to two independent samples of 237 adolescents who presented to an outpatient concussion clinic: 1) ≤7 days (n = 145), and 2) 8 days-1 month (n = 92). The two separate PCAs included nine clinical assessments comprised of: a) four symptoms factors (cognitive/fatigue/migraine, affective, somatic, sleep), b) memory and speeded cognitive performance, c) near point of convergence (NPC), d) oculomotor, and e) vestibular outcomes. A three-component model including 1) symptoms, 2) cognitive, and 3) vestibular/oculomotor factors that accounted for 69.2% of the variance was supported for the ≤7 days sample. All items except somatic symptoms loaded. A different three-component model was supported for the 8 days-1 month sample, including 1) vestibulo-ocular migraine, 2) visuo-cognitive, and 3) affective-sleep that accounted for 72.1% of the variance, with all items loading. The findings supported two different concussion factor models that highlight the influence of time since injury and importance of considering vestibular and oculomotor outcomes in adolescents. Clinicians should evaluate these different factors using a comprehensive, multi domain approach to better inform assessment and monitor recovery in adolescent patients following concussion.Abbreviations: Principal Components Analysis (PCA), Immediate Post-concussion Assessment and Cognitive Testing (ImPACT), Post-concussion Symptom Scale (PCSS), Vestibular/Ocular Motor Screening (VOMS).