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Diffusion tensor imaging in sport-related concussion: A systematic review using an a priori quality rating system.

Diffusion tensor imaging (DTI) of brain white matter (WM) may be useful for characterizing the nature and degree of brain injury following sport-related concussion (SRC) and assist in establishing objective diagnostic and prognostic biomarkers. This study aimed to conduct a systematic review using an a priori quality rating strategy to determine the most consistent DTI WM changes following SRC. Articles published in English (until June 2020) were retrieved via standard research engine and grey literature searches (N=4932), using PRISMA guidelines. Eligible studies were non-interventional naturalistic original studies that conducted DTI within six months of SRC in current athletes from all levels of play, types of sports and sex. A total of 29 articles were included in the review, and following quality appraisal by two raters, data from 10 studies were extracted after being identified as high quality. High quality studies showed widespread moderate to large WM differences when SRC samples were compared to controls during the acute to early chronic stage (days to weeks) following SRC, including both increased and decreased fractional anisotropy and axial diffusivity and decreased mean diffusivity and radial diffusivity. WM differences remained stable in the chronic stage (2 to 6 months post-SRC). DTI metrics were commonly associated with SRC symptom severity, although standardized SRC diagnostics would improve future research. This indicates that microstructural recovery is often incomplete at return to play and may lag behind clinically assessed recovery measures. Future work should explore inter-individual trajectories to improve understanding of the heterogeneous and dynamic WM patterns following SRC.