Objective Emerging evidence suggests that advanced neuroimaging of cerebral hemodynamics may yield a clinical biomarker of mild traumatic brain injury (mTBI). We examined whether (coherence) and novel (absolute phase) functional near-infrared spectroscopy metrics differentiated children with mTBI from mild orthopedic injury (OI).

Design Prospective cohort

Participants Children between 8.00–16.99 years of age were recruited during emergency department visits at Alberta Children’s Hospital within 48 hours of sustaining an mTBI (n = 8, 62.5% sport-related concussion) or mild OI (n=5), and completed fNIRS as part of a follow-up assessment 2 months post-injury (M = 35.38±5.19 days). fNIRS was collected during rest and a 2-back working memory task, with optodes placed over four regions of interest (bilateral dorsolateral prefrontal and motor cortex).

Outcome Measures Two-way ANOVA was used to evaluate the effect of group, regions of interest (ROI), and their interaction on coherence and absolute phase.

Main Results During rest, children with mTBI demonstrated lower absolute phase across ROIs relative to children with OI (F(1, 82)=14.79, p<.001) but the groups did not differ in resting state coherence. During the 2-back task, coherence was reduced in children with mTBI relative to OI, (F(1, 82)=12.35,p<.001), and also varied across ROI, (F(5, 82)=3.82, p=0.004).

Conclusions Our results suggest differences in cerebral hemodynamic measures in pediatric mTBI were context-dependent, with reduced absolute phase at rest and reduced coherence during working memory performance.