Purpose Given the fact that neuroimaging studies are currently not used routinely in the evaluation of concussions in the clinical setting, the diagnosis and management of concussion has centered around subjective symptom reports, clinical and neurocognitive examinations. Functional near-infrared spectroscopy (fNIRS), a noninvasive and portable neuroimaging modality that detects changes in blood oxygenation related to human brain function, is a promising tool to address this gap in the clinical evaluation of concussion. While fNIRS has recently demonstrated that adults with a concussion show reduced brain activation on neurocognitive tests compared to healthy age-matched controls, it has not yet been assessed with other clinical tasks or in the pediatric setting. Thus, we sought to determine the utility of fNIRS to detect and differentiate cortical brain activity among the suite of vestibular oculomotor tests used in a standard clinical evaluation of pediatric concussion. Methods We conducted baseline testing of nine athletes, ages 11-17, who performed a series of tasks commonly used in the clinical evaluation of concussion while wearing an fNIRS headband that recorded anterior prefrontal cortex oxygenation changes with 12 channels/4 optodes at 4Hz sampling rate. The fNIRS sensor used in the study is a portable system miniaturized to the size of a smartphone that can wirelessly transfer data in real-time. The tasks that participants performed with the fNIRS system included a modified version of the vestibulo-ocular motor screen (VOMS), the King-Devick test, and tandem walk assessment. Results Cortical oxygenation changes confirmed prefrontal cortex involvement in oculomotor task engagement as reported in the literature. With controlled task load changes throughout the oculomotor tasks, there were significant differences across increasing difficulty of King-Devick test conditions (F3,32=4.65, p < 0.01) and for horizontal and vertical saccades (F3,14=3.35, p < 0.01). Moreover, for tandem walk, there was a significant interaction with direction (forward and backward) with eyes open and closed (F1,20=7.33, p < 0.014) highlighting that more prefrontal coordination is required specifically for backward eyes closed movement. Conclusion Our preliminary experimental results demonstrate that fNIRS can reliably detect changes in cerebral blood oxygenation that reflect the cognitive workload associated with a given task. The fNIRS’ portability and sensitivity to discriminate based on task difficulty makes it a promising clinical tool for quantifying cortical oxygenation changes after concussion. Further investigation into the utility of this neuroimaging modality in detecting and quantifying changes in the cognitive workload demands of these clinical tasks after injury and over the course of recovery is warranted.
Oxygenation changes with varying conditions of King-Devick test