Hockey Concussion Education Project, Part 2. Microstructural white matter alterations in acutely concussed ice hockey players: a longitudinal free-water MRI study

Abstract

Object Concussion is a common injury in ice hockey and a health problem for the general population. Traumatic axonal injury has been associated with concussions (also referred to as mild traumatic brain injuries), yet the pathological course that leads from injury to recovery or to long-term sequelae is still not known. This study investigated the longitudinal course of concussion by comparing diffusion MRI (dMRI) scans of the brains of ice hockey players before and after a concussion. Methods The 2011–2012 Hockey Concussion Education Project followed 45 university-level ice hockey players (both male and female) during a single Canadian Interuniversity Sports season. Of these, 38 players had usable dMRI scans obtained in the preseason. During the season, 11 players suffered a concussion, and 7 of these 11 players had usable dMRI scans that were taken within 72 hours of injury. To analyze the data, the authors performed free-water imaging, which reflects an increase in specificity over other dMRI analysis methods by identifying alterations that occur in the extracellular space compared with those that occur in proximity to cellular tissue in the white matter. They used an individualized approach to identify alterations that are spatially heterogeneous, as is expected in concussions. Results Paired comparison of the concussed players before and after injury revealed a statistically significant (p < 0.05) common pattern of reduced free-water volume and reduced axial and radial diffusivities following elimination of free-water. These free-water–corrected measures are less affected by partial volumes containing extracellular water and are therefore more specific to processes that occur within the brain tissue. Fractional anisotropy was significantly increased, but this change was no longer significant following the free-water elimination. Conclusions Concussion during ice hockey games results in microstructural alterations that are detectable using dMRI. The alterations that the authors found suggest decreased extracellular space and decreased diffusivities in white matter tissue. This finding might be explained by swelling and/or by increased cellularity of glia cells. Even though these findings in and of themselves cannot determine whether the observed microstructural alterations are related to long-term pathology or persistent symptoms, they are important nonetheless because they establish a clearer picture of how the brain responds to concussion.

Mind the gaps—advancing research into short-term and long-term neuropsychological outcomes of youth sports-related concussions

“…53 Collegiate ice hockey players exhibited similar white matter changes over the course of a season. [54][55][56][57] In addition, repetitive subconcussive head impacts in collegiate American football players have been linked, in a dose-dependent manner, to deficits in BBB integrity, potential loss of white matter integrity, and cognitive dysfunction. 58 These findings probably reflect some level of risk for youths who sustain repetitive subconcussive head impacts, although little research has been devoted specifi cally to this topic.…”

Brain magnetic resonance imaging CO2 stress testing in adolescent postconcussion syndrome

“…Clinical neuroimaging studies, including conventional MRI, are normal in the majority of cases. 17 For this reason, authors of recent studies have aimed to apply even more sophisticated neuroimaging techniques to this condition, including magnetoencephalography, 53 diffusion tensor imaging (DTI), 11,25,29,31,44,47 and task-based functional MRI (fMRI). 7,26,35,49 Despite detecting changes between groups of concussion patients and healthy controls, none of these techniques has emerged as a useful clinical tool that contributes to the management of acute SRC or PCS.…”

Sports Concussion: A Clinical Overview

“…A more recent DTI and concussion systematic review [49] suggested that the most consistent findings were decreased mean diffusivity and/or an increase in fractional anisotropy in white matter within 6 months post-concussion [66][67][68][69][70], but these findings are not universal (i.e., the opposite patterns have also been reported in other studies) [56,62,71]. In addition, reduced radial diffusivity has been reported [68,[72][73][74], but increase and decrease in axial diffusivity have been described [68,69].…”