Sex differences in white matter alterations following repetitive subconcussive head impacts in collegiate ice hockey players

axial diffusivity

CIS

Canadian Interuniversity Sports

corona radiata

Diffusion tensor imaging

external capsule

fractional anisotropy

HCEP

Hockey Concussion Education Project

internal capsule

Ice hockey

ImPACT

Immediate Post-Concussion Assessment and Cognitive Test

left hemisphere

mean diffusivity

MRI

magnetic resonance imaging

NCAA

National Collegiate Athletic Association

radial diffusivity

right hemisphere

RSHI

repetitive subconcussive head impacts

Repetitive subconcussive head impacts

standard deviation

SLF

superior longitudinal fasciculus

Sex difference

TBI

traumatic brain injury

TBSS

tract-based spatial statistics

Traumatic brain injury

white matter

White matter

dMRI

diffusion magnetic resonance imaging

Spearman’s rank correlation coefficient

PMID: 29204342 DOI: 10.1016/j.nicl.2017.11.020

Author

Nico Sollmann, Paul S Echlin, Vivian Schultz, Petra V Viher, Amanda E Lyall, Yorghos Tripodis, David Kaufmann, Elisabeth Hartl, Philipp Kinzel, Lorie A Forwell, Andrew M Johnson, Elaine N Skopelja, Christian Lepage, Sylvain Bouix, Ofer Pasternak, Alexander P Lin, Martha E Shenton, Inga K Koerte

Published

October 31, 2017

Abstract:

OBJECTIVE: Repetitive subconcussive head impacts (RSHI) may lead to structural, functional, and metabolic alterations of the brain. While differences between males and females have already been suggested following a concussion, whether there are sex differences following exposure to RSHI remains unknown. The aim of this study was to identify and to characterize sex differences following exposure to RSHI.

METHODS: Twenty-five collegiate ice hockey players (14 males and 11 females, 20.6 +- 2.0 years), all part of the Hockey Concussion Education Project (HCEP), underwent diffusion-weighted magnetic resonance imaging (dMRI) before and after the Canadian Interuniversity Sports (CIS) ice hockey season 2011-2012 and did not experience a concussion during the season. Whole-brain tract-based spatial statistics (TBSS) were used to compare pre- and postseason imaging in both sexes for fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD). Pre- and postseason neurocognitive performance were assessed by the Immediate Post-Concussion Assessment and Cognitive Test (ImPACT).

RESULTS: Significant differences between the sexes were primarily located within the superior longitudinal fasciculus (SLF), the internal capsule (IC), and the corona radiata (CR) of the right hemisphere (RH). In significant voxel clusters (p < 0.05), decreases in FA (absolute difference pre- vs. postseason: 0.0268) and increases in MD (0.0002), AD (0.00008), and RD (0.00005) were observed in females whereas males showed no significant changes. There was no significant correlation between the change in diffusion scalar measures over the course of the season and neurocognitive performance as evidenced from postseason ImPACT scores.

CONCLUSIONS: The results of this study suggest sex differences in structural alterations following exposure to RSHI. Future studies need to investigate further the underlying mechanisms and association with exposure and clinical outcomes.