How diffusion tensor imaging findings in subconcussive head impacts correlate with head kinematic exposures: a systematic review and quantitative synthesis
- 1Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
Abstract
Collision and contact-sport athletes are repeatedly exposed to subconcussive head impacts or subclinical head acceleration events (HAEs), which are impacts that do not result in a clinical diagnosis of mild traumatic brain injury but may induce subtle neurological alterations. These effects may include structural, functional, and metabolic changes within the brain. Various exposure quantification techniques have been developed to characterise HAE exposure, while diffusion MRI enables assessment of brain microstructural organisation, with changes in diffusion-derived metrics associated with pathophysiological processes.
This systematic review was conducted in accordance with PRISMA guidelines to evaluate the use of various HAE exposure quantification techniques, exposure weighting approaches, and diffusion MRI in characterising the relationship between HAE exposure and brain microstructure in athletes. Across studies, longitudinal findings for fractional anisotropy (FA), mean (MD), axial (AD), and radial diffusivity (RD) were inconsistent, and substantial heterogeneity in exposure quantification methods and analyses was observed. However, quantitative analysis demonstrated a significant negative association between total subclinical HAE count across the season and FA, and a positive association with MD, suggesting cumulative microstructural alteration.
Exposure metrics--including risk-weighted, time-weighted, and finite-element-derived strain measures--showed stronger associations with diffusion MRI alterations than simple impact counts or peak acceleration measures. However, HAE exposure risk models are sport-specific and require broader validation for applicability across sporting cohorts. Future studies should reduce methodological heterogeneity, control for confounding variables, and refine exposure quantification and weighting approaches to better understand the relationship between repetitive subclinical HAE exposure and WM microstructural integrity.
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BibTeX
@misc{tayebi2026diffusion,
title = {{How diffusion tensor imaging findings in subconcussive head impacts correlate with head kinematic exposures: a systematic review and quantitative synthesis}},
author = {M. Tayebi and C. J. A. Saludar and W. Schierding and E. Kwon and J. P. McGeown and A. Wang and J. Fernandez and S. Holdsworth and V. Shim},
howpublished = {medRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.28.26364205},
url = {https://www.medrxiv.org/content/10.64898/2026.09.28.26364205v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - How diffusion tensor imaging findings in subconcussive head impacts correlate with head kinematic exposures: a systematic review and quantitative synthesis
AU - M. Tayebi
AU - C. J. A. Saludar
AU - W. Schierding
AU - E. Kwon
AU - J. P. McGeown
AU - A. Wang
AU - J. Fernandez
AU - S. Holdsworth
AU - V. Shim
PY - 2026
DA - 2026/09/28
PB - medRxiv
DO - 10.64898/2026.09.28.26364205
UR - https://www.medrxiv.org/content/10.64898/2026.09.28.26364205v1
AB - Collision and contact-sport athletes are repeatedly exposed to subconcussive head impacts or subclinical head acceleration events (HAEs), which are impacts that do not result in a clinical diagnosis of mild traumatic brain injury but may induce subtle neurological alterations. These effects may include structural, functional, and metabolic changes within the brain. Various exposure quantification techniques have been developed to characterise HAE exposure, while diffusion MRI enables assessment of brain microstructural organisation, with changes in diffusion-derived metrics associated with pathophysiological processes. This systematic review was conducted in accordance with PRISMA guidelines to evaluate the use of various HAE exposure quantification techniques, exposure weighting approaches, and diffusion MRI in characterising the relationship between HAE exposure and brain microstructure in athletes. Across studies, longitudinal findings for fractional anisotropy (FA), mean (MD), axial (AD), and radial diffusivity (RD) were inconsistent, and substantial heterogeneity in exposure quantification methods and analyses was observed. However, quantitative analysis demonstrated a significant negative association between total subclinical HAE count across the season and FA, and a positive association with MD, suggesting cumulative microstructural alteration. Exposure metrics--including risk-weighted, time-weighted, and finite-element-derived strain measures--showed stronger associations with diffusion MRI alterations than simple impact counts or peak acceleration measures. However, HAE exposure risk models are sport-specific and require broader validation for applicability across sporting cohorts. Future studies should reduce methodological heterogeneity, control for confounding variables, and refine exposure quantification and weighting approaches to better understand the relationship between repetitive subclinical HAE exposure and WM microstructural integrity.
ER -