Transcranial Doppler ultrasound and concussion: Supplemental symptoms with physiology - A systematic review.

Sport-related concussion (SRC) can impair the cerebrovasculature both acutely and chronically. Transcranial Doppler (TCD) ultrasound assessment has the potential to illuminate the mechanisms of impairment and provide an objective evaluation of SRC. The current systematic review investigated studies employing TCD ultrasound assessment of intracranial arteries across three broad categories of cerebrovascular regulation: neurovascular coupling (NVC), cerebrovascular reactivity (CVR), and dynamic cerebral autoregulation (dCA). The current review was registered in the Prospero database (CRD42021275627). The search strategy was applied to PubMed as this database indexes all biomedical journals. Original TCD articles for athletes with medically diagnosed SRC were included. Title/abstract and full-text screening were completed by three authors. Two authors completed data extraction and risk of bias using Methodological Index for Non-Randomized Studies and Scottish Intercollegiate Guideline Network checklists. Of the 141 articles identified, 14 met the eligibility criteria. One article used a NVC challenge, eight assessed CVR, and six investigated dCA. Methodologies varied widely between studies, and results were heterogeneous. There was evidence of cerebrovascular impairment in all three domains roughly 2 days post-SRC, but the magnitude and recovery of these impairments were not clear. There was evidence clinical symptom resolution occurred before cerebrovascular function, indicating physiological deficits may persist despite clinical recovery and return to play. Collectively, this emphasises the opportunity for the use of TCD to illuminate the cerebrovascular deficits caused by SRC. It also highlights there is need for consistent methodological rigor when employing TCD in a SRC population.