Diffusion Tensor Imaging of Sports-Related Concussion in Adolescents

Abstract

Concussion is among the least understood neurologic injuries. The impact of concussion on the adolescent brain remains largely unknown. This study sought to establish short-term changes in white-matter integrity after sports-related concussion in adolescents, and examine the association between changes in white-matter integrity and a clinical measure of concussion. Twelve adolescents, aged 14-17 years with a sports-related concussion within 2 months, and 10 age-matched adolescents with no history of concussion were evaluated with the Sports Concussion Assessment Tool 2 and diffusion tensor imaging. Two measures compared the two groups: fractional anisotropy and mean diffusivity. Whole-brain fractional anisotropy values significantly increased (F(1,40) = 6.29, P = 0.010), and mean diffusivity values decreased (F(1,40) = 4.75, P = 0.036), in concussed athletes compared with control participants. Total scores on the Sports Concussion Assessment Tool 2 were associated with whole-brain fractional anisotropy. Mean diffusivity values with lower scores were associated with higher fractional anisotropy (R² = 0.25, P = 0.017) and lower mean diffusivity (R² = 0.20, P = 0.038). We provide evidence of structural changes in the integrity of white matter in adolescent athletes after sports-related concussion.

Introduction

An estimated 173,285 sports-related and recreation-related traumatic brain injuries in children and adolescents are treated in emergency rooms in the United States annually [1]. These data likely underestimate the actual number of injuries, because many are not reported or are treated outside the emergency room, making traumatic brain injuries a significant public health issue. In Canada, an estimated 98,440 people (2.4% of the population aged at least 12 years) sustained a head injury between 2009 and 2010. Of those, 23% (n = 22,720) were adolescents [2].

The risk of concussion in youth is of particular concern because the brain is still developing throughout adolescence and may be more susceptible to hypoxia, ischemia, and traumatic axonal injury [3], [4]. Although physical features resolve within 2-10 days in the majority of adults who sustain a single concussion [5], [6], [7], school-aged children demonstrate postconcussive features for a longer period. Barlow et al. [8] reported that 3 months after injury, 14% of children aged more than 6 years remained symptomatic. The frontal and temporal lobes appear most vulnerable to injury, and damage to these areas is associated with impairments of executive function, learning, and memory, along with behavioral disturbances [9], [10], [11]. Impairments in executive functioning during the adolescent phase of development may involve long-term implications for quality of life and future developmental processes. However, associations between behavioral sequelae and underlying structural brain changes after concussion have been difficult to establish.

Growing interest has developed in the use of newer imaging technologies, such as diffusion tensor imaging, which is particularly sensitive to changes in the microstructure of frontal white matter [12] and provides quantitative measures of the structural integrity of white matter in the brain. Importantly, diffusion tensor imaging detects subtle reductions in white matter integrity that correlate with function [13]. This study sought to investigate structural changes in the brains of adolescents who had sustained a sports-related concussion within a 2-month period, using diffusion tensor imaging, compared with age-matched control subjects with no history of concussion. In addition, the association between specific diffusion tensor imaging measures and a clinical assessment tool (Sports Concussion Assessment Tool 2) was examined.