Quantified Head-Ball Impacts in Soccer: A Preliminary, Prospective Study

Repetitive, sub-concussive head impacts have been associated with increased chronic traumatic encephalopathy (CTE) incidence. CTE diagnosis traditionally relies on postmortem examination, which limits precise correlation between cause and effect. This prospective study embraced innovative diffusion magnetic resonance imaging, which enables in vivo quantification of acute, subacute, and chronic changes in brain tissue microstructure. This approach was used to evaluate changes in white matter microstructural status at intervals up to 180 days following a specified soccer heading protocol. This study was approved by university research ethics committees. Twelve adult males were recruited to the study and gave signed, informed consent. Six Intervention participants were university-level soccer players, with six Control participants drawn from university-level noncontact sports. Multi-shell diffusion-weighted MRI data were acquired on a 3T Siemens Connectom (300 mT/m) scanner using the HARDI protocols. Baseline measures of fractional anisotropy, mean diffusivity, and mean kurtosis were acquired at day 0. The Intervention cohort then performed 10 soccer "headers" in a laboratory, with acceleration-time data captured using an instrumented mouthguard and post-processed to report common metrics. The Intervention group was then re-scanned at day 1 (n = 6), day 90 (n = 5), and day 180 (n = 4). The Control group was re-scanned at day 1 (n = 6) and day 180 (n = 3). Many brain tracts were identified as having significant (p < 0.05) changes in white matter microstructural changes at day 90, which correlated strongly with the magnitude of head impact. A smaller number of tracts had changes at day 1 and day 180. These results indicate that, within this pilot population, the magnitude of repeated soccer headers appears to correlate with the magnitude of white matter microstructural change. Additional investigation is required to determine whether the effect of such an intervention influences long-term brain health risk.Board.