Changes observed on advanced imaging and investigation techniques
| Paper | Study type/setting | Subject characteristics | Inclusion criteria | Investigation | Findings/results |
|---|---|---|---|---|---|
| A. Athletes with persistent symptoms following concussion | |||||
| Chen et al54 | Prospective cohort | 9 Concussions, 6 healthy controls | Persistent symptoms following concussion | fMRI (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 al55 | Cross-sectional | 10 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 postinjury | Diffusion 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 al56 | Cross-sectional | 14 Patients with mild TBI—recruited from 2 tertiary trauma centres 23 Controls | Persistent symptoms following mild TBI | ERP, 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 al57 | Cross-sectional | 19 Individuals with mild TBI (11 with persistent symptoms, 8 recovered) and 9 healthy controls | Injury sustained 5 years earlier, GCS 13–15 on admission, normal MRI | MT (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 al58 | Prospective (multicentre) cohort | 40 Concussions 30 Healthy controls | Recent concussion; age 16–35 | MRS 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 al59 | Prospective cohort | College athletes 10 Concussions 10 controls | Recent concussion | MRS (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 al60 | Cross-sectional | College athletes 17 concussions 17 controls | Recent concussion, clinically recovered | rsFMRI (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 al61 | Cross-sectional | 48 Concussions 48 Controls | Concussion assessed >6 months postinjury | EEG (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 al62 | Cross-sectional | Collegiate athletes 14 Concussions 15 Controls 9 Additional concussions | Recent concussion, recovered clinically | rsFMRI (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.