Table 2

Changes observed on advanced imaging and investigation techniques

PaperStudy type/settingSubject characteristicsInclusion criteriaInvestigationFindings/results
A. Athletes with persistent symptoms following concussion
Chen et al54Prospective cohort9 Concussions, 6 healthy controlsPersistent symptoms following concussionfMRI (working memory task)Significantly reduced task-related BOLD changes in the prefrontal cortex in athletes with prolonged symptoms following concussion
Activation patterns improved as symptoms improved on follow-up
Cubon et al55Cross-sectional10 Collegiate students with prolonged symptoms compared to 10 healthy controls and 5 TBI patients (2 moderate TBI and 3 severe TBI)Persistent symptoms 1 month postinjuryDiffusion tensor imaging (MD and FA analysed using tract-based spatial statistics)Significant increase in MD in concussed individuals
Similar results were observed in the moderate but not severe TBI patients when compared to controls
Gosselin et al56Cross-sectional14 Patients with mild TBI—recruited from 2 tertiary trauma centres
23 Controls
Persistent symptoms following mild TBIERP, fMRI (working memory task)Attenuated BOLD signal changes and reduced amplitude for the working memory task were observed in the mild TBI group
BOLD signal changes were correlated with symptom severity
Tallus et al57Cross-sectional19 Individuals with mild TBI (11 with persistent symptoms, 8 recovered) and 9 healthy controlsInjury sustained 5 years earlier, GCS 13–15 on admission, normal MRIMT (measured using navigated transcranial magnetic stimulation and electromyography)MT was higher in some (but not all) mild TBI individuals compared to controls
Changes were observed even in individuals who had recovered clinically
The results suggest that subtle prolonged changes may exist in some patients following mTBI and that in a proportion of these patients the changes may be ‘compensated’
B. Athletes with concussion whose symptoms had resolved
Vagnozzi et al58Prospective (multicentre) cohort40 Concussions
30 Healthy controls
Recent concussion; age 16–35MRS
Used single voxel (ROI: right frontal lobe), and chemical shift techniques to analyse data
Self-reported symptoms recovered within 3–15 days
Significant differences between concussed and control groups were observed in metabolite ratios at day 3 postinjury. Metabolite changes gradually recovered to control levels within 30 days of injury
Henry et al59Prospective cohortCollege athletes
10 Concussions
10 controls
Recent concussionMRS (ROI: prefrontal and primary motor cortex)Neurometabolic differences between concussed and control groups were observed in the acute phase (lower N-acetylaspartate:creatine levels in the prefrontal cortex and lower glutamate:creatine levels in the motor cortex) as well as the delayed phase (increase in the myoinositol levels in the motor cortex)
Slobounov et al60Cross-sectionalCollege athletes
17 concussions
17 controls
Recent concussion, clinically recoveredrsFMRI (ROI: right dorsolateral prefrontal cortex, bilateral precuneus, bilateral primary visual cortex, bilateral hippocampus)All concussion individuals were asymptomatic at rest and had no NP deficits
rsFMRI revealed disrupted functional network both at rest and in response to a graded physical test
Baillargeon et al61Cross-sectional48 Concussions
48 Controls
Concussion assessed >6 months postinjuryEEG (visual 3-stimulus oddball paradigm)Concussed athletes had lower P3b amplitudes than the control athletes
Adolescent athletes showed persistent deficits in working memory
Johnson et al62Cross-sectionalCollegiate athletes
14 Concussions
15 Controls
9 Additional concussions
Recent concussion, recovered clinicallyrsFMRI (measured the default mode network)Significant default mode network connectivity differences were observed between concussed and control groups
Regression analysis revealed a significant reduction in magnitude of connection between various structures in the brain as a function of the number of concussions
  • BOLD, blood oxygenation level-dependent; ERP, event-related brain potential; FA, fractional anisotropy; fMRI, functional magnetic resonance imaging; NP, neuropsychological; MD, mean diffusivity; MRS, MR spectroscopy; MT, motor threshold; ROI, regions of interest; rsFMRI, resting state fMRI; TBI, traumatic brain injury.